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Originally Processed With FOIA(s):
FOIA Number:
2005-0336-F
2005-0336-F
FOIA
MARKER
This is not a textual record. This is used as an
administrative marker by the George Bush Presidential
Library Staff.
Record Group/Collection:
George H.W. Bush Presidential Records
Collection/Office of Origin:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
OA/ID Number:
62006
Folder ID Number:
62006-008
Folder Title:
D. Allan Bromley: Referrals [2 of 7] [1992]
Stack:
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Section:
Shelf:
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0
O
0
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TYPE:
ACTION
DOCUMENT NUMBER: 9203591
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
SIE, Soey: CSIRO AUSTRALIA
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 12/07/92
SUBJECT: HE IS WRITING WITH PERSONAL INFORMATION AND
REQUESTING A RECOMMENDATION FROM DR. BROMLEY.
DIRECTORATE
STAFF
ASSIGNED:
D. Allan Bromley
ASSIGNED:
ACTION
STAFF
REQUIRED:
AS NECESSARY
ACTION:
SENDER'S DUE DATE:
OSTP DUE DATE:
12/30/92
STAFF DUE DATE
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DATE COMPLETED/DEPT:
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EXT:
REMARKS:
OSTP RECEIVED: 12/16/92
DEPT RECEIVED:
FILE: P-DAB-REFERRAL
CENTRAL FILES:
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
01a. Letter
To: Allan Bromley From: Soey Hian Sie
12/7/92
(b)(6)
Re: Request for recommendation [personal information
redacted] (2 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
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2005-0336-F
Appeal Case #:
Re-review Case #:
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RESTRICTION CODES
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Freedom of Information Act - [5 U.S.C. 552(b)]
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(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
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P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
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and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
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personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
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C. Closed in accordance with restrictions contained in donor's deed of
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gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
01b. Resume
Resume of Soey Hian Sie [personal information redacted]
11/92
(b)(6)
(1 pp.)
Collection:
Record Group:
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Office:
Science and Technology Policy, Office of (OSTP)
Series:
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Subseries:
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WHORM Cat.:
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D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
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FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
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AR Disposition:
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RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
C
S
I
R
ppm sensitivity
micron spatial resolution
in-house interpretative support
V
S
I
N
F
Nuclear Instruments and Methods in Physics Research B15 (1986) 525-529
525
North-Holland, Amsterdam
MR
DEPTH PROFILES OF HYDROGEN AND OXYGEN IN HYDROGENATED AMORPHOUS
SILICON THIN FILMS
S.H. SIE 1) D.R. McKENZIE ²). G.B. SMITH 3) and C.G. RYAN 1)
11 CSIRO Division of Mineral Physics, P.O. Box 136, North Ryde, NSW 2113, Australia
2) School of Physics, University of Sydney, NSW 2006, Australia
3) Department of Physics, New South Wales Institute of Technology, Sydney, NSW 2007, Australia
Detailed depth profiles of hydrogen and oxygen have been measured in samples of thin films of a-Si: H produced by dc magnetron
glow discharge techniques. The resonant capture reaction ¹H(¹⁹F, αγ)¹⁶O at E₁₉₁ = 6.417 MeV was used for hydrogen profile
measurements, and resonant a scattering at Eₐ = 3.0359 MeV was used for oxygen. Contrasting results reflecting the different
fabrication conditions were obtained and these were correlated with measured electrical properties.
1. Introduction
tive interpretation of the resultant data is difficult [5].
Electron energy loss spectroscopy (EELS) and Ruther-
The electrical and optical properties of a-Si: H pro-
ford back scattering spectrometry (RBS) can yield infor-
duced by glow discharge decomposition of silane are
mation on depth profiles, but the nuclear reactions
related to the distribution of hydrogen. Incorporated in
¹⁸O(p, α)¹⁵ N and ¹⁸O(p, γ)¹⁹F are more commonly
the silicon network, hydrogen increases dopability by
used [6]. These reactions however rely on the rare iso-
terminating dangling bonds [1]. However hydrogen may
tope ¹⁸O, and are therefore impractical due to the
also be present in other forms, particularly as hydroxyls
reduced sensitivity in natural targets. The deuteron re-
when moisture absorption occurs, which could be detri-
actions ¹⁶O(d, p) or (d, n) have also been used, but the
mental to the electrical properties.
high radiation background produced by these beams
The presence of oxygen in the bulk of a semiconduc-
makes the technique less attractive [6].
tor can also affect its electrical properties, and on the
In this paper, we report the use of resonant α
surface it can affect contact properties, which are im-
scattering to determine the oxygen profiles. exploiting
portant for device applications. Surface defects may in
the resonance at an α bombarding energy of Eₐ = 3.0359
fact dominate electrical properties by creating mobile
MeV. Results are presented together with hydrogen
carrier accumulation layers [2]. Oxidation can be ex-
profiles obtained from the same specimens, to delineate
pected to be one source of oxygen, but a major contri-
the sources of these elements and correlate them with
bution could come from adsorption and absorption of
the properties of the samples.
moisture into microvoids, typically found in films of
semiconductor produced by vacuum deposition tech-
niques. The porosity of the films depends on the fabri-
2. Experimental procedure
cation conditions, and thus the hydrogen and oxygen
contents may be used to diagnose the effects of different
2.1. Film preparation
conditions.
In the following, a number of samples of thin films
Various parameters in the glow discharge deposition
of a-Si: H produced by dc magnetron glow discharge
of a-Si H in the dc magnetron system have a consider-
have been studied. Hydrogen profiles were determined
able impact on the electrical, optical and mechanical
using the ¹H(¹⁹F, αγ)¹⁶O resonant reaction at a ¹⁹F
properties of the films [7]. In particular, very significant
bombarding energy of 6.417 MeV. Preliminary results of
differences are observed between samples prepared with
these measurements have been reported [3].
the substrate at cathode potential, where there is consid-
Oxygen content is usually determined as part of the
erable bombardment by energetic positive ions and also
hydroxyl using the infrared absorption (IR) technique
fast deposition rates of up to 3.5 nm/s. Electrical
[4], which does not provide depth profile information.
measurements have indicated that the surfaces play a
Some attempts have been made to measure oxygen
more significant role under these conditions. and one
profiles using Auger electron spectroscopy (AES) and
aim of this study was to see whether the hydrogen and
secondary ion mass spectrometry (SIMS), but quantita-
oxygen profiles could be used to distinguish between
0168-583X/86/$03.50 © Elsevier Science Publishers B.V.
X. NUCLEAR REACTION ANALYSIS
(North-Holland Physics Publishing Division)
632
Nuclear Instruments and Methods in Physics Research B15 (1986) 632-635
North-Holland, Amsterdam
MRF318
ANALYSIS OF CARBON CONTENT AND DISTRIBUTION IN a-Si₁ H FILMS BY RESONANT
SCATTERING
S.H. SIE D.R. McKENZIE ²), G.B. SMITH 3) and C.G RYAN 1)
" CSIRO Division of Mineral Physics, PO Box 136, North Ryde, NSW, 2113, Australia
2) School of Physics, University of Sydney, Sydney, NSW, 2006, Australia
3) Department of Physics, New South Wales Institute of Technology, Sydney, NSW, 2007, Australia
Resonant alpha scattering has been used to determine detailed depth profiles of carbon in amorphous silicon carbon alloys
produced by glow discharge decomposition. The carbon profiles exhibit a two layer structure similar to that indicated by hydrogen
profiles in a-Si: H films. By comparison electron probe analysis seems to considerably overestimate average carbon content while
electron energy loss measurements on very thin specimens agree with the surface layer content in the resonance profiles of thicker
films. The bulk content is, however, still lower.
1. Introduction
of the samples were also examined by the resonance
scattering method [4].
Amorphous hydrogenated silicon-carbon alloys have
important applications in optoelectronic devices. They
have a variable optical gap [1] according to the carbon
2. Experimental method
content, adjustable from 1.8 eV for a-Si H through a
maximum value of around 2.4 eV for intermediate com-
2.1. Sample preparation
positions to 2.0 eV for a-C H. The alloys can be
produced by glow discharge decomposition techniques
The dc magnetron apparatus used in the production
from mixtures of silane and methane. The rates of
of the specimens has been described in detail elsewhere
decomposition of the two gases vary with conditions of
[5]. The cathode was stainless steel which was operated
manufacture and the mixture, and thus the carbon
in a condition in which it became overcoated with
content of the resultant material must be determined
silicon and carbon. Various mixtures of semiconductor
independently.
grade silane (SiH₄) and ultra high purity methane (CH₄)
Unfortunately, although there are a number of stud-
gases were used. Operating conditions for the mag-
ies of a-Si₁. Cx H in the literature, most of the methods
netron are shown in table 1. Substrates for the speci-
used for the analysis of film composition are dubious. It
mens were mounted on the anode. The cathode was
has recently been found [2] that two methods of analy-
operated for 5 min in the gases to be used for deposition
sis, electron probe microanalysis (EPMA) and electron
before the sample was inserted. Various substrate tem-
energy loss spectroscopy (EELS) give results differing
peratures were used, in the range 26-500°C (table 2).
by as much as factor of 2. Conventional RBS (Ruther-
Film thicknesses were measured using a Talystep step
ford backscattering) methods could, in favourable cases
height gauge.
(e.g. for thick films >1 µm), be used to determine C
content, but detailed profiles cannot be determined
reliably by this method. However, a strong resonance
occurs at a higher bombarding energy Eₐ = 4.26 MeV,
Table 1
which enhances the detection sensitivity and, as a result
The deposition conditions for a-Si₁ XCx H films
of its narrow width, enables measurements of detailed
depth profiles [3].
Discharge voltage
900 V
In the following, carbon profiles in several a-
Current
30-50 mA
Si, ,Cx H thin film samples produced by the dc mag-
Magnetic field
0.01 T
netron glow discharge method were obtained using the
Total gas pressure
1.2 Pa
Substrate (anode) cathode distance
30 mm
resonant α scattering technique. The results are com-
Substrate temperature
25-500°C
pared with other methods. The oxygen contents of some
0168-583X/86/S03.50 © Elsevier Science Publishers B.V.
(North-Holland Physics Publishing Division)
Scanning Microscopy, Vol. 5, No. 4, 1991 (Pages 977-987)
0891-7035/91$3.00+.00
Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA
MICRO-PIXE (PARTICLE-INDUCED X-RAY EMISSION ANALYSIS)
APPLICATIONS IN MINERALS RESEARCH
S.H. Sie*, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility (HIAF)
CSIRO Division of Exploration Geoscience
(Received for publication May 6, 1991, and in revised form October 22, 1991)
Abstract
Introduction
The versatility of the PIXE method with microbeams
of protons as a non-destructive, in-situ probe for trace
Microbeam methods in the geosciences have expanded
element analysis in the geosciences has been demonstrated
rapidly within the past two decades, adding new dimensions
in an ever increasing number of cases. While in most
to established methodology and opening up new areas of
applications the method can be considered as derivative or as
investigation. Much of the progress is due to the fact that
an extension of electron microprobe methodology, features
detailed analysis can be carried out on monomineralic grains,
unique to the proton microprobe enable new approaches to
the basic constituent of all geological samples. With
hitherto intractable problems of analysis. An appropriate
micrometre size probes chemical composition can be
niche has been established in igneous mineralogy and
obtained on microstructures associated with the generation
and subsequent alteration of the minerals. The electron
petrology, with important implications both in the basic
geosciences as well as mineral industry applications,
microprobe has been responsible for identification of many
new minerals, with its prime capability of in-situ non-
particularly in the diamond exploration industry. This paper
destructive elemental analysis of the major and minor
reviews recent advances and discusses the advantages and
elements, and trace elements at concentrations above 500
limitations of current micro-PIXE applications in the
ppm. Secondary ion mass spectrometry (SIMS) with ion
geosciences in view of other competing and complimentary
methods.
microprobes is traditionally a tool for isotopic geochemistry
and geochronology, but is now also used as a trace analyzer
[Reed 1989]. A newcomer into the field is the synchrotron
radiation probe [Bos et al., 1984]. The proton microprobe
[Cookson et al., 1972, 1976] has also been in existence for
two decades and its applications in minerals research and in
other areas [Cahill, 1980] are expanding rapidly.
Applications of proton microbeam methods have
developed along two separate lines, similar to the
development of electron beam methodology. In one the
emphasis is on imaging applications and spatial resolution is
usually the driving force behind its development, akin to the
scanning electron microscope (SEM) development. The
other mode concentrates on quantitative analysis, usually
directed towards obtaining the best sensitivity for elemental
analysis, akin to the electron microprobe (EMP). With the
much lower level of accompanying background continuum
KEY WORDS: Proton-microprobe, PIXE, X-ray analysis,
radiation, particle induced X-ray emission (PIXE)
[Johansson et al, 1970, 1976, Folkmann et al 1974] offers a
trace element, geology, mineralogy.
sensitivity as much as 100 times better than electron induced
*Address for correspondence:
X-ray spectroscopy. The proton microprobe can also used
S.H. Sie
for Rutherford backscattering spectrometry (RBS) and
Heavy Ion Analytical Facility (HIAF)
nuclear reaction analysis (NRA) [Toulhot et al. 1991, Courel
CSIRO Division of Exploration Geoscience
et al. 1991]. When gamma rays are detected the method is
P.O. Box 136, North Ryde NSW 2113, Australia
known as PIGME - particle induced gamma ray emission,
which is used mainly to detect low Z elements (e.g. F with
Phone No. 61 2 887-8648
ppm sensitivity [Bird and Clayton 1983]). Microbeams of
977
294
Nuclear Instruments and Methods in Physics Research B52 (1990) 294-297
North-Holland
An AMS facility for minerals exploration research
S.H. Sie, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, PO Box 136, N. Ryde 2113, Sydney, Australia
An AMS (accelerator mass spectrometry) system based on a Tandetron has been constructed at the CSIRO HIAF laboratory at
North Ryde, and is currently undergoing tests. The system is designed to enable cosmogenic isotope based chronology, and
eventually will be developed to enable ultratrace measurements in mineralogical samples.
1. Introduction
2. The AMS system
HIAF is an analytical laboratory based on a model
The HIAF-AMS project will proceed in two stages,
1430 Tandetron accelerator, commissioned in late 1983
with the first resulting in standard AMS capability, viz.
[1]. It is dedicated to developing IBA (ion beam analy-
10 Be, ¹⁴C dating on "bulk" samples. ³⁶Cl detection will
sis) and AMS applications in the geosciences in support
also be attempted. The second stage involves the devel-
of the Australian minerals industry. An essential re-
opment of the microprobing Cs sputter source. The
quirement for mineralogical and petrological applica-
AMS system incorporates the existing beam transport
tions of IBA is the development of the proton micro-
system at HIAF, with the addition of a beamline for the
probe, completed in 1985, to enable in situ microanaly-
detection system, and a separate injector.
sis of monomineralic grains, the fundamental con-
A schematic of the HIAF beam transport system,
stituent of geological samples [2,3]. With this instru-
including the AMS system, is shown in fig. 1. The AMS
ment, significant progress has been achieved in the area
injector system is based on a double focusing, 90°
of trace element geochemistry, particularly in igneous
analyzing magnet with a radius of 30 cm and beam
mineralogy leading to new methods of exploration.
product (ME/q² in amu MeV/e² units) of 7, with a
The development of AMS was carried out mainly in
maximum, aberration-limited momentum resolution of
recognition of its importance in geochronology, based
6500 for an object diameter of 0.25 mm. For normal
on cosmogenic light radioisotopes. The research interest
operation using typical ion sources, a more moderate
of the Division lies mainly in the applications of 10 Be
resolution is expected for good transmission efficiency
and 36 dating to problems relevant to exploration and
through the accelerator. The magnet box is electrically
mining. The scope of published work on applications of
insulated from the rest of the beamline to permit energy
10 Be [4], ranging from soil transport and erosion studies,
modulation of the incident beam ("bouncing") to main-
rock exposure ages on to petroleum dating offers excit-
tain the same magnetic rigidity. A 90° electrostatic
ing prospects in research of ore and petroleum genesis
spherical analyzer with 75 cm radius preceding the
as aids in exploration. Similarly, the information from
magnet will be added in the future, to improve the
³⁶Cl as a tracer and chronometer of groundwater can be
rejection ratio of adjacent isotopes.
an important supplement in hydrogeochemical methods
The beam from a General Ionex model 834 Hiconex
of exploration, and water management in arid areas. In
sputter source is focused by an einzel lens to form a
addition to the direct requirements in the minerals
waist at the magnet's object slits. The beam is further
industry, HIAF is accessible by other areas of research,
transported to the original low-energy cup through the
and thus the AMS facility will also be available for ¹⁴C
"old", demagnetized injector, by means of another einzel
dating.
lens. Distances are chosen to match the emittance of the
Of more direct interest to minerals research is the
AMS injector system to the acceptance of the original
AMS capability to detect very low levels (ppb) of trace
system. The "cone" of the Hiconex source, which holds
elements. So far the method has been applied using a
the sample to be sputtered, is modified to permit focus-
submillimeter sputtering beam, which is not adequate
ing of the Cs beam onto the downstream side, and into
for most measurements requiring monomineralic in situ
a smaller area. The sample is loaded into a "well" in the
microanalysis [5]. A microprobing sputter source must
cone (1 mm diameter and 1 mm deep). This modifica-
be developed for successful applications of AMS as a
tion reduces the amount of sample required and im-
trace analyzer.
proves the source emittance.
0168-583X/90/$03.50 © 1990 - Elsevier Science Publishers B.V. (North-Holland)
294
Nuclear Instruments and Methods in Physics Research B52 (1990) 294-297
North-Holland
An AMS facility for minerals exploration research
S.H. Sie, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, PO Box 136, N. Ryde 2113, Sydney, Australia
An AMS (accelerator mass spectrometry) system based on a Tandetron has been constructed at the CSIRO HIAF laboratory at
North Ryde, and is currently undergoing tests. The system is designed to enable cosmogenic isotope based chronology, and
eventually will be developed to enable ultratrace measurements in mineralogical samples.
1. Introduction
2. The AMS system
HIAF is an analytical laboratory based on a model
The HIAF-AMS project will proceed in two stages,
1430 Tandetron accelerator, commissioned in late 1983
with the first resulting in standard AMS capability, viz.
[1]. It is dedicated to developing IBA (ion beam analy-
10 Be, 1⁴C dating on "bulk" samples. 36 Cl detection will
sis) and AMS applications in the geosciences in support
also be attempted. The second stage involves the devel-
of the Australian minerals industry. An essential re-
opment of the microprobing Cs sputter source. The
quirement for mineralogical and petrological applica-
AMS system incorporates the existing beam transport
tions of IBA is the development of the proton micro-
system at HIAF, with the addition of a beamline for the
probe, completed in 1985, to enable in situ microanaly-
detection system, and a separate injector.
sis of monomineralic grains, the fundamental con-
A schematic of the HIAF beam transport system,
stituent of geological samples [2,3]. With this instru-
including the AMS system, is shown in fig. 1. The AMS
ment, significant progress has been achieved in the area
injector system is based on a double focusing, 90°
of trace element geochemistry, particularly in igneous
analyzing magnet with a radius of 30 cm and beam
mineralogy leading to new methods of exploration.
product (ME/q² in amu MeV/e² units) of 7, with a
The development of AMS was carried out mainly in
maximum, aberration-limited momentum resolution of
recognition of its importance in geochronology, based
6500 for an object diameter of 0.25 mm. For normal
on cosmogenic light radioisotopes. The research interest
operation using typical ion sources, a more moderate
of the Division lies mainly in the applications of 10 Be
resolution is expected for good transmission efficiency
and ³⁶Cl dating to problems relevant to exploration and
through the accelerator. The magnet box is electrically
mining. The scope of published work on applications of
insulated from the rest of the beamline to permit energy
10 Be [4], ranging from soil transport and erosion studies,
modulation of the incident beam ("bouncing") to main-
rock exposure ages on to petroleum dating offers excit-
tain the same magnetic rigidity. A 90° electrostatic
ing prospects in research of ore and petroleum genesis
spherical analyzer with 75 cm radius preceding the
as aids in exploration. Similarly, the information from
magnet will be added in the future, to improve the
³⁶Cl as a tracer and chronometer of groundwater can be
rejection ratio of adjacent isotopes.
an important supplement in hydrogeochemical methods
The beam from a General Ionex model 834 Hiconex
of exploration, and water management in arid areas. In
sputter source is focused by an einzel lens to form a
addition to the direct requirements in the minerals
waist at the magnet's object slits. The beam is further
industry, HIAF is accessible by other areas of research,
transported to the original low-energy cup through the
and thus the AMS facility will also be available for ¹⁴C
"old", demagnetized injector, by means of another einzel
dating.
lens. Distances are chosen to match the emittance of the
Of more direct interest to minerals research is the
AMS injector system to the acceptance of the original
AMS capability to detect very low levels (ppb) of trace
system. The "cone" of the Hiconex source, which holds
elements. So far the method has been applied using a
the sample to be sputtered, is modified to permit focus-
submillimeter sputtering beam, which is not adequate
ing of the Cs beam onto the downstream side, and into
for most measurements requiring monomineralic in situ
a smaller area. The sample is loaded into a well" in the
microanalysis [5]. A microprobing sputter source must
cone (1 mm diameter and 1 mm deep). This modifica-
be developed for successful applications of AMS as a
tion reduces the amount of sample required and im-
trace analyzer.
proves the source emittance.
0168-583X/90/$03.50 © 1990 Elsevier Science Publishers B.V. (North-Holland)
284
Nuclear Instruments and Methods in Physics Research B54 (1991) 284-291
North-Holland
Section VIII. Geological and mineralogical applications
The proton microprobe: a revolution in mineral analysis
1
S.H. Sie, W.L. Griffin, C.G. Ryan, G.F. Suter and D.R. Cousens
Heavy Ion Analytical Facility (HIAF), CSIRO Division of Exploration Geoscience, P.O. Box 136, N. Ryde, NSW 2113, Australia
Application of the proton microprobe as a quantitative tool for trace-element microanalysis in the geosciences can be considered
to have crossed the threshold of acceptability in a number of areas, particularly in igneous and metamorphic mineralogy and
petrology. In the minerals industry, applications in base metal ore mineralogy provide new data useful for both processing and
genetic studies. Applications in diamond and gold exploration are developing into new methods, with potential widespread
acceptance. The paper will review a few case histories, and discuss the limitations of the current state-of-art and conditions conducive
to widespread acceptance by geoscientists and by the minerals industry.
1. Introduction
an appropriate niche in igneous mineralogy and pe-
trology, marked by contribution to advances in the
The anticipated benefits of the proton microprobe
mainstream areas. In sulfide mineralogy, trace-element
applications in the geoscience have been realized in an
data have contributed to the understanding of ore gene-
ever increasing number of areas, marked by the progres-
sis and found direct application in exploration and
sion from experimentation to routine application of the
processing of base metal ores. The present paper re-
technique. Better access to accelerator facilities by geo-
views the potential and constraints of analytical micro-
scientists, close links between physicists and geoscien-
PIXE, and presents a few case histories for illustration.
tists, and dedicated facilities are requisites of this pro-
gress. Such conditions apply in a number of laborato-
ries, notably at Heidelberg, Witwatersrand and Los
Alamos [1-3]. HIAF is an example of a dedicated
facility, established to enable sustained development of
2. The proton microprobe
the applications in the geosciences, and promote the
introduction of accelerator-based analytical methods
into the mineral industry [4]. This includes not only the
The applications of the proton microprobe in general
proton microprobe [5], but other ion beam analysis
have developed along two virtually separate lines. In
(IBA) methods and accelerator mass spectrometry
one the emphasis is on imaging and on the attainment
(AMS) as well. In Australia this is warranted by the
of the best resolution, with the scanning mode as the
important role of the mineral industry in the national
main mode of operation [7,8]. The other concentrates
economy.
on its use as a quantitative microanalytical tool [6,9],
The statistical nature of geological samples and data
with resolution considered as a second priority. The
requires analysis of large numbers of samples, and the
latter has been the line adopted at HIAF for geoscien-
interpretation often depends critically on the accuracy
tific applications. Progress in this has been reviewed in
of the data. Speed of analysis governs the viability of
a number of recent papers [11-13], and is the subject of
the method, particularly in the industrial context, affect-
the present paper.
ing among others the cost factor. With appropriate
One emerging conclusion is that quantitative micro-
design of both hardware [5] and software [6] these
PIXE in the geosciences has graduated from being an
requirements can be fulfilled successfully.
experimental tool, into a vital tool for the progress in a
While experimentation continues, significant pro-
number of specific areas. The successes achieved thus
gress has been achieved over the past few years. In
far have been based mainly on adaptation of electron
particular, quantitative analytical micro-PIXE has found
microbeam methodology, i.e. nondestructive in-situ
trace-element analysis by induced X-ray spectrometry.
The better sensitivity (as low as <1 ppm) afforded by
the lower bremsstrahlung revealed new information
1
Present address: Electron Microscopy Unit, Queensland
hitherto inaccessible or tedious to obtain. However, one
University of Technology, Brisbane, Qld., Australia.
has to be continually aware of alternative [14], and
0168-583X/91/$03.50 © 1991 - Elsevier Science Publishers B.V. (North-Holland)
308
Nuclear Instruments and Methods in Physics Research B49 (1990) 318-322
North-Holland
APPLICATION
THE
MICROPROBE TO DIAMOND EXPLORATION AND GENESIS
W.L. GRIFFIN
SFNS. S.H. SIE and G.F. SUTER
Ion
Analytical
xploration Geoscience, North Ryde, NSW 2113, Australia
The
HIAF
proton
chromites.
The
trace elements in mantle-derived minerals, including garnets, ilmenites,
goal
Interpretation
and to improve the use of indicator minerals in diamond exploration
time
scales
of
on magma compositions and fractionation mechanisms, metasomatic
improve
and the environment of diamond formation. Trace-element data on indicator
within
one
diamondiferous source rocks, and help to recognize the presence of multiple
drainage.
ulcomately
help
to
improve
the
models
that
guide
exploration.
1. Introduction
2. Methods
km in the Earth's mantle, and carried more surface
Diamonds are formed at depths of than 150
The analytical methods used in this work have been
reported elsewhere [1,2] and a detailed treatment of the
kimberlite during volcanic eruptions of special rock to the such as
HIAF hardware and software is given by Ryan et al.
rocks or lamproite. The diamond types, of such
[3-5]. Mineralogical applications of the proton micro-
therefore is typically a few ppm. Exploration content for diamonds
probe, especially those reported here, require large num-
abundant is heavily based on the of more
bers of accurate, high-precision analyses. The HIAF
mantle-derived "indicator recognition minerals"
hardware [6] has been specifically designed to allow
soil rope garnet, Mg-rich ilmenite. chromite) in of
high sample throughput, with high beam currents for
and stream sediments.
low detection limits, flexible sample handling and
Electron the microprobe analyses of
minimum cycling times for sample changes. The soft-
These give data major-element are used composition
ware development has concentrated on ease of use and
evaluation of prospects. during to
reliability of data treatment, with special attention given
to the development of stable background algorithms for
particular samples are derived
rocks. However, this method
the reproducible treatment of low-statistics peaks [3,5].
because minerals of similar
For most of the PIXE microanalysis reported here, a 8
also may be derived from
nA 3 MeV proton beam was used, with a beam spot size
Since 1987, HIAF
of 20 µ.m. A 200 µm Al X-ray absorber is usually
selected to attenuate major-element lines. The typical
proton microprobe analysis
tor minerals, aimed at
integrated charge was 3 µC, corresponding to an
crimination to this exp
acquisition time of 6 min per grain.
material being analyzed
centrates from diamond
provide empirical discrir
3. Results
analyzing the minerals
(xenoliths and megacrysts
3.1. Garnets
kimberlites, and the minera
diamonds. These studies
The grains of Cr-pyrope garnet ((Mg, Fe)₃-
ming processes in the man
(Al, Cr)₂Si₃O₁₂) found in heavy-mineral concentrates
ble for the formation of
from volcanic rocks are derived largely from the disag-
interpret compositional fea
gregation of xenoliths of mantle wall rocks such as
samples. This report will
garnet peridotite. Griffin et al. [7] showed that the
studies of xenoliths and inci
distribution of Ni between Cr-pyrope garnet and olivine
in such xenoliths is strongly dependent on T, as mea-
(North-Holland) 0168-583X/90/$03.50 Elsevier
NORTH-HOLLAND
PHYSICS
PUBLISHING
NH
APPLICATION OF THE PROTON MICROPROBE IN MINERAL EXPLORATION
AND PROCESSING
S.H. SIE, C.G. RYAN, D.R. COUSENS and W.L. GRIFFIN
Heavy Ion Analytical Facility, CSIRO. Division of Exploration Geoscience, P.O. Box 136, North Ryde, NSW 2113, Australia
The in situ high-sensitivity multielement detection capability of PIXE, combined with µm spatial resolution opens up new
possibilities in mineral-related research. Trace element data obtained using the proton microprobe provide new tools in exploration
for diamond and precious metals, ore genesis studies as well as in the processing of precious-metal-bearing ores. Introduction of this
new methodology to the minerals industry however is controlled by economic factors which must be taken into consideration.
Reprinted from NUCLEAR INSTRUMENTS AND METHODS
IN PHYSICS RESEARCH B
664
Nuclear Instruments and Methods in Physics Research B10/11 664-67
North-Holland. Amsterdam
AN ACCELERATOR FACILITY WITHIN A MINERAL RESEARCH ESTABLISHMENT
S.H. SIE
Division of Mineral Physics. CSIRO Institute of Energy and Earth Resources. PO Box 136. North Ryde. NSW 2113. Australia
The importance of the minerals industry in Australia is evident from its share of about 40% of the country's export earnings. its
economic success is due in no small measure to the industry's ability to keep abreast with technological innovations and scientific
developments. often through collaborations with federal Governments research laboratories such as the CSIRO. In this context. the
CSIRO Division of Mineral Physics recently commissioned a Laboratory. known as HIAF - the Heavy Ion Analytical Facility -
based on a General Ionex 3 MV Tandetron. a tandem electrostatic accelerator. The Laboratory was designed to facilitate the
development of the applications of a host of ion-beam techniques to problems in the geosciences. extending or complementing
established methods. Flow-on to the minerals industry is anticipated. with varying degrees of immediacy dependent on the particular
technique. The first stage operational at the commissioning provides RBS (Rutherford backscattering spectrometry). PIXE (particle
induced X-ray emission) and NRA (nuclear reaction analysis) measurements. and includes the development of 2 beam microprobe
An ultra-sensitive accelerator mass spectrometry (AMS) system is planned for the second stage. to permit studies of chronology based
on radio cosmogenic isotopes and ultra-traces in mineral samples.
1. Introduction
based analytical techniques in the material sciences is
now fairly established. and applications in minerals
The Australian minerals industry expanded rapidly
research. where one now deals with natural instead of
during the past two decades and became an important
man-made material. can be considered as a logical pro-
part in the country's economy. In its peak year of
gression.
1981-82, the industry generated about 40% of the ex-
Of immediate interest is the application of standard
port earnings [1]. One contributing factor to the success
ion-beam techniques. namely the RBS (Rutherford
of the industry is its ability to keep abreast with techno-
backscattering spectrometry). NRA (Nuclear Reaction
logical and scientific developments in all its stages. from
Analysis) and PIXE (particle Induced X-ray Emission
exploration, mining on to beneficiation process. this
ability is bolstered by the Federal and State govern-
Table 1
ments involvement through bodies such as Geological
Comparison of analytical techniques in the geosciences
Survey bureaus and research laboratories such as the
CSIRO Minerals Research Laboratories as it was origi-
Conventional method
Ion-beam method
nally known, now part of the larger Institute of Energy
Crystallography
XRD
RBS-channeling
and Earth Resources. Collaborative efforts between the
(gross structure)
(atomic location of
industry and government laboratories proved effective
impurities)
in the introduction and development of various ad-
Trace elements
XRF
PIXE
vanced techniques.
(some trace detection
(ppm sensitivity
The Division of Mineral Physics played a consid-
capabilities)
electron microprobe
PIXE microprobe
erable role in a number of cases: the transient electro-
(in-situ. > 500 ppm
(in-situ. 1 ppm
magnetic technique for prospecting of buried ore bod-
sensitivity)
sensitivity)
ies, the use of Landsat images as aid in explorations and
Isotopic analysis
Muss-spectrometer
AMS
adaptation of nuclear techniques in mining and be-
(1:10" sensitivity
(1:10th)
neficiation. The decision by the Division to acquire an
no probing)
sensitivity.
accelerator laboratory can be viewed as a continuation
Ion-microprobe
trace detection
of this tradition. The Laboratory, known as HIAF the
(trace detection
ppb)
Heavy Ion Analytical Facility - was conceived in the
> 100 ppm)
recognition of the demonstrated and potential applica-
Depth profiling
(ion-microprobe)
NRA
tions of ion-beam techniques to geological and minera-
depth resolution 10 (depth resolution
range <1 µ
10 nm
logical problems. as well as in other research areas of
range several pm
interest to the Institute. Applications of accelerator
0168-583X/85/$03.30 is Elsevier Science Publishers B.V.
(North-Holland Physics Publishing Division)
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
01c. Resume
Resume of Soey Hian Sie [personal information redacted]
11/92
(b)(6)
(5 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
664
Nuclear Instruments and Methods in Physics Research B10/11 (1985) 664-676
North-Holland. Amsterdam
AN ACCELERATOR FACILITY WITHIN A MINERAL RESEARCH ESTABLISHMENT
S.H. SIE
Division of Mineral Physics. CSIRO Institute of Energy and Earth Resources. PO Box 136. North Ryde. NSW 2113. Australia
The importance of the minerals industry in Australia is evident from its share of about 40% of the country's export earnings. Its
economic success is due in no small measure to the industry's ability to keep abreast with technological innovations and scientific
developments. often through collaborations with federal Governments research laboratories such as the CSIRO. In this context. the
CSIRO Division of Mineral Physics recently commissioned a Laboratory. known as HIAF the Heavy Ion Analytical Facility
based on a General Ionex 3 MV Tandetron. a tandem electrostatic accelerator. The Laboratory was designed to facilitate the
development of the applications of a host of ion-beam techniques to problems in the geosciences. extending or complementing
established methods. Flow-on to the minerals industry is anticipated. with varying degrees of immediacy dependent on the particular
technique. The first stage operational at the commissioning provides RBS (Rutherford backscattering spectrometry). PIXE (particle
induced X-ray emission) and NRA (nuclear reaction analysis) measurements. and includes the development of a beam microprobe
An ultra-sensitive accelerator mass spectrometry (AMS) system is planned for the second stage. to permit studies of chronology based
on radio cosmogenic isotopes and ultra-traces in mineral samples.
1. Introduction
based analytical techniques in the material sciences is
now fairly established. and applications in minerals
The Australian minerals industry expanded rapidly
research, where one now deals with natural instead of
during the past two decades and became an important
man-made material. can be considered as a logical pro-
part in the country's economy. In its peak year of
gression.
1981-82, the industry generated about 40% of the ex-
Of immediate interest is the application of standard
port earnings [1]. One contributing factor to the success
ion-beam techniques. namely the RBS (Rutherford
of the industry is its ability to keep abreast with techno-
backscattering spectrometry). NRA (Nuclear Reaction
logical and scientific developments in all its stages. from
Analysis) and PIXE (particle Induced X-ray Emission
exploration. mining on to beneficiation process. this
ability is bolstered by the Federal and State govern-
Table 1
ments involvement through bodies such as Geological
Comparison of analytical techniques in the geosciences
Survey bureaus and research laboratories such as the
CSIRO Minerals Research Laboratories as it was origi-
Conventional method
Ion-beam method
nally known, now part of the larger Institute of Energy
Crystallography
XRD
RBS-channeling
and Earth Resources. Collaborative efforts between the
(gross structure)
(atomic location of
industry and government laboratories proved effective
impurities)
in the introduction and development of various ad-
Trace elements
XRF
PIXE
vanced techniques.
(some trace detection
(ppm sensitivity
The Division of Mineral Physics played a consid-
capabilities)
electron microprobe
PIXE microprobe
erable role in a number of cases: the transient electro-
(in-situ. > 500 ppm
(in-situ. 1 ppm
magnetic technique for prospecting of buried ore bod-
sensitivity)
sensitivity)
ies, the use of Landsat images as aid in explorations and
Isotopic analysis
Mass-spectrometer
AMS
adaptation of nuclear techniques in mining and be-
(1: 10" sensitivity
(1:10
neficiation. The decision by the Division to acquire an
no probing)
sensitivity.
accelerator laboratory can be viewed as a continuation
Ion-microprobe
trace detection
of this tradition. The Laboratory, known as HIAF - the
(trace detection
ppb)
Heavy Ion Analytical Facility - was conceived in the
> 100 ppm)
recognition of the demonstrated and potential applica-
Depth profiling
(ion-microprobe)
NRA
tions of ion-beam techniques to geological and minera-
depth resolution - 10.A (depth resolution
range μ
- 10 nm
logical problems. as well as in other research areas of
range several µm
interest to the Institute. Applications of accelerator
0168-583X/85/$03.30 is Elsevier Science Publishers B.V.
(North-Holland Physics Publishing Division)
S.H. Sie / An accelerator facility within a Mineral Research Establishment
665
The advent of AMS (Accelerator Mass Spectrometry)
Table 2
presents yet another tool which is even more directly
Acceptance test at General Ionex Corp. (February 1983) and in
applicable to geological problems. Table 1 summarizes a
Sydney (September 1983)
number of typical analyses required in minerals research
Terminal voltage
and the ion-beam techniques are juxtaposed as an ex-
conditioning: + 2.6 MV (at GIC). 2.8 MV in Sydney
tension or as a complement to established techniques.
with beam (protons): 2.4 2.5 MV
This paper describes briefly the development of the
ripple (DVM-GVM): 0.3-0.7 kV
laboratory. Some preliminary results are presented to
Analyzed beam currents:
illustrate the utility of accelerator-based techniques in
1. Direct extraction Duo Plasmatron:
the earth sciences, and in minerals research in particu-
protons: > 10 µA. E = 5.0 MeV
lar.
> 10 µA. E = 0.4 MeV
50% transmission)
oxygen (0³⁺ ): 12 µA. E = 9.0 MeV
2. The Laboratory
2. D.P. (+ve)+ exchange canal
Alphas (He²⁺ ): 2 µ.A. E = 6.75 MeV
3. Hiconex sputter source:
The selection for a suitable accelerator was governed
Si (3⁺) 3 µA, E = 6.4 MeV (max rigidity)
by a number of criteria:
Ni (3⁺) 46 nA. E = 3.0 MeV
- the accelerator must enable all ion beam techniques
(3⁺) 3 µA, E = 6.0 MeV
applications, including the AMS;
C (3⁺) 15 µA. E = 9.0 MeV
- since the Division has no established infra-structure
N¹⁴ (3⁺) 0.5 µA. E = 9.0 MeV
comparable to that found typically in physics depart-
ments, the accelerator must be relatively easy to
operate and maintain;
- the variety of techniques requires a flexible machine.
Particular care was observed during the accelerator
where change of ion species and variation in energies
installation to the alignment, cleanliness of vacuum
can be effected expeditiously;
components and the pressure vessel. The laboratory
- an extra criterion set by other interests in the In-
floor was preloaded prior to the arrival of the accelera-
stitute is that the accelerator should be capable of
tor with simulated weight of the system. to ensure that
producing heavy ion beams of relatively low energies
no change can occur after the installation. Thorough
500 keV), comparable to that obtainable with
cleaning of vacuum parts. particularly the accelerator
ion-implanters.
tubes, resulted in a vacuum of 6X 10⁻⁸ Torr in the
The first three criteria lead naturally to the specifica-
tubes. The pressure vessel was alternatingly evacuated
tions for a tandem electrostatic accelerator. with a
to 20 µm Hg and backfilled with dry N₂ a few times
minimum terminal voltage of at least 2 MV.
prior to charging with the SF₀ insulating gas. The mois-
The General Ionex Co. won the tender for the supply
ture content of the SF₆ in the pressure vessel was found
of a 2.25 MV Tandetron. which was subsequently up-
to be stable at around 90 parts-per-million (ppm)
graded to 3 MV. The accelerator was delivered in mid
eliminating the need for a drying system. A cryogenic
1983 and acceptance tests were carried out in September
SF₆ gas handling system was built which minimizes
1983 (see table 2). Although the laboratory was offi-
contamination sources by eliminating the need for com-
cially opened in October 1983, tests and development
pressors. The system consists of a bank of Al gas
continued well into 1984. Fig. 1 shows the layout of the
cylinders which can be cooled by immersion in liquid
laboratory, which occupies the ground-floor of a new
nitrogen when storing the gas from the tank. The re-
three storey building. Up to five beam lines will be
verse cycle is simply effected by heating the cylinders to
installed ultimately. Fig. 2 is the photograph of the
provide the latent heat of evaporation.
accelerator hall. showing the two beam lines operational
The accelerator voltage was calibrated by means of
at commissioning. All experimental apparatus pass the
the "F (p. αγ) ¹⁶O* resonance at Eₚ = 0.8721 MeV. Li
switching magnet were designed and built by the Divi-
(p. n) Be and "F (p. n) "Ne neutron thresholds at
sion to ultra-high vacuum standards. The first beam line
Eₚ = 1.8806 and 4.2343 MeV respectively [3] on a thick
permits RBS. NRA and PIXE measurements. The sec-
LiF target. The analyzing magnet field is measured with
ond beam line is a dedicated microprobe. A set of
a Rawson probe. Over the period of 8 months we found
electrostatic quadrupole lens with the "Russian
that the energy stability of accelerator is excellent. as
quadruplet" configuration is used to shape the beam to
can be observed in experiments involving resonances.
microns dimensions [2]. The specimen chamber includes
such as hydrogen profiling described further below.
a Si(Li) detector and provisions for a wavelength disper-
There was no evidence of long term drift. the reproduci-
sive system to be installed at a later date. and a normal
bility of terminal voltage over the same period is better
viewing microscope with 400 X magnification.
than 0.5 kV. This is remarkable considering that there is
VI. PIXE
666
S.H. Sie / An accelerator facility within a Mineral Research Establishment
SFS GAS MANGLING
SYSTEM
TANDETRON
ANALYZER
10% SOURCE
MAGNET
OFFICE
OFFICE
an
ACCELERATOR MALL
CONTROL
CONSOLE
COMPUTER
SWITCHING MAGNET
CONTROL ROOM
EXPERIMENTAL
ELECTRONICS
SETUP
TARGET
PREPARATION
OFFICE
OFFICE
OFFICE
TARGET AREA
0
1
2
3
6
5 m
Fig. 1. Schematic lay-out of the HIAF Laboratory at the CSIRO Institute of Energy and Earth Resources. Sydney, Australia. Two out
of the ultimate five beam lines are operational currently.
orders of magnitude better than can be obtained with
electron microprobes. Fig. 3 shows a PIXE spectrum
obtained from a US Geological Survey Standard "5
ppm" glass (GSC) using 3 MeV protons. A 400 µm Al
absorber was used to suppress lines from the major
elements, mainly below Fe. It can be seen that 5 ppm
for medium mass elements can be detected quite read-
ily.
1000
GSC GLASS
3 MeV PROTONS
Rb
Sr 27ppm
Pb
Y 8 pm
Fig. 2. A view of the accelerator hall showing the Tandetron in
the background and the two beam lines in the foreground. All
Counts
As
beam lines are constructed to UHV standard.
Nb 5 ppm
500
Ge
Mo
no analyzing slits stabilization system, such as that used
on Van de Graaffs.
Rh
3. Experimental programme
0
10.0
15.0
20.0
X -ray energy
( keV
3.1. PIXE
Fig. 3. PIXE spectrum obtained with 3 MeV protons of a
standard glass containing a cocktail of trace elements. A 400
The importance of this technique is apparent from
µm Al absorber was used to suppress major lines. It can be
the fact that its sensitivity at a few ppm is at least two
seen that 5 ppm level can be detected readily.
S.H. Sie / An accelerator facility within a Mineral Research Establishment
667
For mineralogical applications, a microbeam is nec-
Fe
ILMENITE
essary to enable probing of coexisting mineral phases
200
which typically would be a few tens of microns dimen-
Nb
sion.
6ppm
Electrostatic lenses offer a few advantages over mag-
netic ones, particularly when used with electrostatic
Zr
100
10ppm
accelerators. Excitation of the lens is proportional to
E/q = + 1)V/q, where E and q are the beam energy
and charge state respectively, V is the terminal voltage.
The excitation is thus completely independent of the
C
0
=
mass of the beam projectile m, whereas magnetic lenses
would require an excitation proportional to m/q which
150
may not be realizable for heavy ions. Another ad-
vantage is that electrostatic lenses are amenable to
miniaturization, enabling compact lenses to be built. in
100
turn liberating more space for other uses such as the
wavelength dispersive detector system planned for
50
HIAF.
The electrostatic quadruplet lens at HIAF has been
0
constructed with minimal adjustment, and relied instead
4.0
8.0
12.0
16.0
20.0
on the best possible mechanical precision for alignment
X-ray energy (keV)
of the components. Preliminary test on-line yielded a 20
µm beam spot with a coarse object slits. An object
YIELD WITH 400 F AL ABSORBER
aperture with a defined dimension will be installed
Fig. 4. PIXE spectra obtained with 3 MeV protons microbeam
shortly.
of 2 samples of ilmenite (FeTiO₃) from two different sources.
Trace element distribution plays an important role in
showing the contrast of the trace elements Zr and Nb. The
studies of mineral and ore genesis, an in geochemical
major lines are suppressed by the 400 µm Al absorber.
methods of exploration for concealed deposits. In the
last decade some 20 major deposits and even more
sources. The object of the study is to investigate whether
smaller ones ranging from porphyry and massive
there are systematic differences in characteristics of the
sulphide types to gold-silver veins and pegmatites have
trace element distribution in this mineral found in bar-
been discovered by geochemical techniques [3]. The
methods are based mainly on areal surveys of secondary
ren areas and in formations containing economic miner-
dispersion haloes and trains in media such as surface
waters, soils and drainage sediments. A number of
techniques are available for detection of elements at
trace levels < 1000 ppm), based mainly on optical
emission or absorption, but they are invariably destruc-
tive thus incapable of giving in-situ information. Erro-
neous information can arise due to concentration of
trace elements in inclusions and imperfections in the
mineral's crystalline structure.
One example of potentially major application of
PIXE with a microprobe is in the study of pathfinder
minerals. Fig. 4 shows the two spectra obtained from
ilmenite (FeTiO₃) found commonly in igneous rocks.
Again the spectra were obtained with 3 MeV protons
and a 400 µm Al absorber was used to suppress the
major elements. The importance of using a microprobe
can be understood when one examines the photo micro-
200 µm
graph of the mineral grain (fig. 5), showing extensive
pitting and cracks where anomalous concentrations of
certain trace elements may occur. Data were obtained
Fig. 5. A photograph of one of the grains of ilmenite mineral
from parts of the grain with clear surface, and the two
used to obtain the spectra in fig. 4. A microbeam is needed to
spectra show a contrast of the content of trace elements
avoid the pits and inclusions in the mineral which will give
Zr and Nb obtained from two grains from different
erroneous trace element concentrations.
VI. PIXE
668
S.H. Sie / An accelerator facility within a Mineral Research Establishment
als such as diamonds in kimberlites. Such a study re-
The use of RBS in crystallographic study through the
quires extensive accumulation of data. to establish any
channeling phenomenon is well established. with most
possible trend.
applications in the semiconductor study. Extension of
The PIXE technique with energy dispersive detectors
these applications in mineral crystallography can be
is necessarily limited to detection of elements heavier
anticipated to yield new information.
than Na. due to the absorbers needed to protect the
detector from scattered beam. This limit can be pushed
3.3. NRA
towards lower Z when a heavier beam is used to induce
the fluorescence, requiring thinner absorber.
The role of NRA in hydrogen profiling is well docu-
mented [6]. One application of interest in geotectonic
3.2. RBS
study is in the measurement of the rate of diffusion of
water in quartz, a major constituent of most rocks.
Detection of low Z elements, particularly H. C. N.
under high pressure and temperature such as that ob-
O, F are of interest in geological and minerals research.
taining in the earth's crust. The phenomenon "hydro-
as they are present in virtually all minerals. The RBS
litic weakening" in quartz [7]. the increase of plasticity
technique and NRA as will be discussed further below.
with increasing water content, has so far been studied
can be used to complement PIXE for detection of light
mainly by means of infrared spectroscopy for the detec-
elements. A variation of the RBS technique exploiting
tion of the hydroxyl. which does not yield depth distri-
resonant scattering provides an alternative method of
bution information. A systematic study to elucidate the
profiling. For example. a strong resonance at alpha
problem has begun at HIAF. Fig. 7 shows an example
bombarding energy of 3.0359 MeV can be exploited to
of hydrogen profile obtained from a synthetic quartz
detect and depth profile oxygen [5]. This is illustrated in
hydrated under high pressure and temperature.
fig. 6 showing spectra obtained from a mineral pyrrho-
The data were obtained with the 19 ay). ¹⁶O*
tite - a nonstoichiometric compound of general formula
reaction at resonant energy 6.417 MeV. Although this
Fe₁ xS, where X can vary from 0 to 0.21. Oxygen plays
resonance is not as strong as the more commonly used
an important role in determining the stability of the
one at 16.44 MeV, it gives a better depth resolution and
various compounds, particularly monoclinic pyrrhotite
longer range of applicability. The N reaction at 6.385
(X = 0.125). The oxygen can be detected readily as can
MeV gives even better resolution, but the beam is not as
be seen in the figure. Normal RBS does give sufficient
easily produced in a tandem accelerator as ¹⁹F.
sensitivity, particularly on thick samples. The resonance
Future development to increase the H detection
enhances the oxygen detection, illustrated dramatically
sensitivity includes a low background system similar to
in part b of the figure obtained from quartz, where
that developed at Heidelberg [8] or the forward recoil
oxygen is present in large quantity (67% atomic). The
spectrometry method [9].
oxygen must be determined in-situ with a microbeam to
avoid micro-inclusions of oxides and silicates.
Depth (nm)
0
100
200
300
400
E = 6.417 MeV
3.1 MeV a on
3
10
(a) Pyrrhotite
60
(b) Quartz
(a)
0
S
50
103
Fe
102
Si
Pb
Resonance yield (arb.units)
2
40
0.73 %
Cu
at. H
Counts
(b)
30
PH
1
20
10
10
1
0
0
0
1
2
3
6.5
7.0
7.5
Eα (MeV)
E19F (MeV)
Fig. 6. RBS spectra from (a) pyrrhotite and (b) quartz showing
Fig. 7. Hydrogen profile of a synthetic quartz hydrated at high
the resonant oxygen peak. The bombarding energy is higher
temperature and pressure. The surface peak represents mois-
than the resonance O(a. a') at ER = 3.0359 MeV. thus the
ture adsorbed on the surface. The data can be unravelled to
peaks observed originate from sub-surface oxygen.
deduce the diffusion rate of water.
S.H. Sie / An accelerator facility within u Mineral Research Establishment
669
Table 3
The system planned for HIAF is shown in fig. 8. A
Application of 10 Be and 36 dating by AMS
double focusing magnet with a moderately high resolu-
tion (M/AM> 800) will be added as a separate injec-
10
tor. The E/q analysis follows the m/q analysis. as
climatology from study of ice cores
practised in a number of laboratories. This has the
cosmic ray variation from study of sediments
disadvantages in the need to alter the analysing magnet
global production rate from rainfall study
setting for injection of the various isotopes. With the
ocean floor subduction from study of volcanic rocks
eventual computerized control of the beam transport
age of marine phosphorities
mineral nodules study
components, this does not present a severe drawback.
dating of petroleum
soil study for erosion, weathering
surface exposure age of rocks
5. Summary
meteoritic impact ejects
A 3 MV Tandetron Accelerator was installed at the
hydrology: groundwater in Arizona
Heavy Ion Analytical Facility (HIAF) of the CSIRO
Great Artesian Basin
Division of Mineral Physics at North Ryde. a suburb of
Milk River Aquifer
Sydney, Australia. The laboratory was designed to
radioactive waste repository evaluation
facilitate development and applications of ion-beam
techniques in the geosciences, with the anticipated flow-
on to the minerals industry. Initially, established tech-
3.4. AMS
niques of RBS. NRA and PIXE, including a micro-
probe. will be utilized, and these can be considered as
The relevance of AMS to the geosciences became
an extension or complementary to conventional analyti-
more apparent with the increasing number of applica-
cal tools at the geoscientist's disposal. In addition. an
tions [10]. Its significance in the ¹⁴C dating is now
accelerator mass spectrometry system, with obvious im-
firmly established. More important to the geosciences is
portant application in the geochronology and trace ele-
the application of ¹⁰Be and ³⁶C1 dating. A summary, by
ment studies, will be developed.
no means complete. of applications to date is shown in
One key ingredient to ensure the success of such
table 3.
facility is the ease of operation and maintenance from
In addition, with a microprobing source the AMS
the user's and support staff points of view. The choice
will extend the range of the best of current conventional
of a Tandetron appears to have fulfilled these aims.
ion-microprobe, not only for isotopic analysis. but also
despite minor problems encountered at the beginning.
for in-situ ultra-trace detection (parts-per-billion ranges).
The author wishes to thank the staff at the Division
of Mineral Physics. and the general site staff at the
F.
Cs beam
Institute for their prodigious effort and skill in the
U
sputter lon source
installation and development of the laboratory. The
O
Division of Mineralogy contributed in the development
Existing
injector
2.5 MV
90' Analyzing
of the microprobe. General Ionex cooperativeness dur-
magnet
HV Terminal
magnet
©
ing the whole project is gratefully acknowledged. Spe-
AMS
injector
cial thanks are due to C. Ryan. G. Suter, J. Pearson and
Select
magnet
m q
C. Dawson on site and to K. Purser, A. Petersen. R.
HV Stock
"TANDETRON"
Schneider, D. Mills and T. Smick at General Ionex.
Switching
Duoplasmatron
mcgnet
P.x
p-Pixe
RESUNPA
beam
References
Electrostatic
spherical
analyzer
[1] D.M. Newbold. ed., Jobson's Mining Yearbook 1983/1984
12* (down)
(Dun and Bradstreet. Melbourne. Australia. 1983).
ДЕНЕ
[2] T. Ya. Fishkova, L.A. Baranova and S.A. Yavor. Bull.
proportional
counter
Acad. Sci. (USSR) 32 (1968) 951; J.A. Cookson. Nucl.
AMS
Instr. and Meth. 165 (1979) 477.
beam line
[3] R.W. Boyle, in: Geophysics and Geochemistry in Search
Fig. 8. Schematic diagram of the AMS system planned for the
for Metallic Ores, ed., P.J. Hood, Geol. Surv. Canada.
HIAF laboratory. A separate injector will be added. and the
Econ. Geol. Report 31 (1979) 25.
detector system including a spherical electrostatic analyzer will
[4] J.B. Marion and F.C. Young. Nuclear Reaction Analysis.
be installed as one of the beam lines.
Graphs and Tables (North-Holland, Amsterdam, 1968) p.
145.
VI. PIXE
670
S.H. Sie / An accelerator facility within a Mineral Research Establishment
[5] F. Ajzenberg-Selove. Nucl. Phys. A392 (1983) 1: J.R.
[8] H. Damjantschitsch et al., Nucl. Instr. and Meth. 218
Cameron. Phys. Rev. 90 (1953) 839.
(1983) 129.
[6] J.F. Ziegler et al., Nucl. Instr. and Meth. 149 (1978) 19.
[9] J. L'Ecuyer. C. Brassard. C. Cardinal and B. Terreault.
[7] D.T. Griggs and J.D. Blacic. Trans. Amer. Geophys. Un-
Nucl. Instr. and Meth. 149 (1978) 271.
ion 45 (1964) 102; M.S. Paterson. Bull. Mineral 105 (1982)
[10] G.F. Herzog and T.H. Kruse, in: EOS. American Geo-
20.
physical Union Transactions 64 (1983) 594; B.R. Doe.
ibid., 595.
NORTH-HOLLAND
PHYSICS
PUBLISHING
NH
APPLICATION OF THE PROTON MICROPROBE IN MINERAL EXPLORATION
AND PROCESSING
S.H. SIE, C.G. RYAN, D.R. COUSENS and W.L. GRIFFIN
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, P.O. Box 136, North Ryde, NSW 2113, Australia
The in situ high-sensitivity multielement detection capability of PIXE, combined with µm spatial resolution opens up new
possibilities in mineral-related research. Trace element data obtained using the proton microprobe provide new tools in exploration
for diamond and precious metals, ore genesis studies as well as in the processing of precious-metal-bearing ores. Introduction of this
new methodology to the minerals industry however is controlled by economic factors which must be taken into consideration.
Reprinted from NUCLEAR INSTRUMENTS AND METHODS
IN PHYSICS RESEARCH B
690
Nuclear Instruments and Methods in Physics Research B40/41 (1989) 690-697
North-Holland, Amsterdam
APPLICATION OF THE PROTON MICROPROBE IN MINERAL EXPLORATION
AND PROCESSING
S.H. SIE, C.G. RYAN, D.R. COUSENS and W.L. GRIFFIN
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, P.O. Box 136, North Ryde, NSW 2113, Australia
The in situ high-sensitivity multielement detection capability of PIXE, combined with µm spatial resolution opens up new
possibilities in mineral-related research. Trace element data obtained using the proton microprobe provide new tools in exploration
for diamond and precious metals, ore genesis studies as well as in the processing of precious-metal-bearing ores. Introduction of this
new methodology to the minerals industry however is controlled by economic factors which must be taken into consideration.
1. Introduction
may not be advisable to analyze grains with sizes less
than a few tens of µm, to avoid complications due to
Accelerator-based analytical methods' applications
underlying or overlapping phases.
in the geosciences expanded rapidly within the past
Extending the applications to the minerals industry
decade, as more laboratories developed stronger links
adds another dimension, namely the cost factor, to the
with geoscience establishments. Such links became the
general problem of introducing a novel methodology. In
foundation of the establishment of the CSIRO HIAF
contrast to academic applications where usually a limited
laboratory, warranted by the importance of the minerals
number of analyses on a limited number of samples are
industry in the Australian economy [1].
sufficient, industrial applications deal with much larger
Among the methods, PIXE is the most readily
numbers of samples. Hence the cost of analyses must be
adapted one, being closely related to the established
reduced in order to make the method viable in view of
electron microprobe (EMP). With detection limits of
competing with conventional methods. This can be off-
approximately up to a hundredfold better than those of
set by the uniqueness of the information or by superior
the EMP, it offers new possibilities in trace-element
quality of the data obtained. Economic considerations
geochemistry, with implications in both geology and
are of paramount importance in an industry controlled
exploration research. For example, it can provide parti-
by commodity market fluctuations which in turn govern
tion coefficients of trace elements among coexisting
the areas for development of applications. In the follow-
mineral phases or the distribution of certain elements
ing, examples are presented which reflect this con-
straint.
(zoning) in a single grain. These are key data for under-
standing the physicochemical control of geological
processes, a subset of which is the ore genesis. In
exploration, the signature of elements at trace levels in
2. The instrument
pathfinder minerals can yield discriminants to dis-
tinguish barren prospects. Distribution of trace ele-
The design of a microprobe system is invariably
ments around a prospect of concealed ore deposit can
dictated by the intended use of the facility. In a recent
improve targeting.
review, Cabri [2] listed attributes of an ideal system
The use of microbeams in the analysis is often cru-
from a mineralogical perspective.
cial: in natural and laboratory-synthesized samples
The CSIRO HIAF microprobe system is part of an
coexisting mineral phases are usually minute, typically a
analytical laboratory, based on a General Ionex 3 MeV
few µm in dimensions; zoning occurs on µm scale; in
Tandetron. The laboratory was designed to enable ap-
processing ores comminution to µm size is typical.
plications of the complete suite of ion-beam analytical
However, while it may be desirable to use the smallest
methods (RBS, NRA) including accelerator mass spec-
beam possible, usually at the expense of beam intensity,
trometry (AMS). The microprobe system is based on an
this must be balanced against the fact that the range of
elecrostatic "Russian" quadruplet lens [3]. There is con-
proton beams used in PIXE (2-4 MeV) is of the order
siderable overlap between Cabri's list and the following
of 50 µm in most minerals, although the effective depth
features which were implemented at HIAF in view of
of X-ray production is less (10-20 µ m). Therefore, it
the perceived requirements for geoscientific and in-
0168-583X/89/$03.50 © Elsevier Science Publishers B.V.
(North-Holland Physics Publishing Division)
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
691
dustrial applications:
themselves, particularly in microanalysis, and the meth-
- Practical beam currents (1-20 nA) at 5-20 µm reso-
ods of determination used originally to establish the
lution for viable analysis time for traces at the ppm
published values. This could arise from possible inho-
level;
mogeneity of standard material itself, or in the prepara-
- ability to view the specimen at normal angle, to
tion of the specimen. Such problems apply for natural
enable analysis of thick samples of opaque minerals,
(e.g. SARM-7, BCR, AGV) and synthetic standards (e.g.
with 150 X magnification; this also facilitates tuning
USGS GSC). The reliability of the computer analysis of
of the microbeam visually on an optically fluorescing
typical X-ray spectra for treatments of the general back-
target;
ground and of weak peaks in the presence of interfering
- ability to move specimens in view with microstages;
strong lines or relatively high background becomes of
- a set of filters or combination of filters for the Si(Li)
fundamental importance. A suite of computer programs
detectors readily selectable, to permit optimization of
have been developed which addressed these problems,
detection sensitivities of desired elements;
and these are described in detail elsewhere [4-6].
- rapid sample change through a vacuum lock;
- detection of radiations other than X-rays, namely
backscattered particles and gamma rays;
3. Applications
- on-line data analysis, and rapid turnaround;
- ease of operation and maintenance;
3.1. Diamond exploration
- standardless quantitative analysis.
It is important to recognize that PIXE should not be
An established method for diamond exploration is
used in isolation, but rather to complement or to be
based on characterization of indicator heavy-minerals
supplemented by other more conventional tools, such as
collected by stream and soil sampling. These indicator
EMP or optical microscopy, in view of a number of
minerals are associated with igneous, mafic or ultra-
problems:
mafic rocks, such as kimberlites and lamproites, which
- The use of absorbers in order to protect the Si(Li)
are the main sources of diamonds. The same minerals
detector from scattered beam or to optimize detection
are often found as inclusions in the diamonds them-
sensitivity of a certain range of elements usually pre-
selves, and the proton microprobe has been used to
vents detection of major light elements in the matrix
study their characteristics which provide information on
which are required in the quantification of the data.
the conditions of the diamond growth [4].
While nominal compositions can be used if the sample
In exploration, garnets and ilmenites are commonly
is known generically, more often there are significant
used, and chromites are particularly important being
variations from the nominal values, which affects the
resistant to deep weathering. Previous schemes to dif-
results of the analysis.
ferentiate diamondiferous occurrences based on major
- Normalization of the observed major element is also
and minor element composition derived from electron
required to bypass the problem of accurate beam charge
probe analysis, have met with some success, particularly
measurements. Charge buildup on targets, despite the
in the case of garnets as used for South African kimber-
presence of a conducting layer on the specimen surface,
lites. However, the applicability of the method is not
affects beamcharge integration unpredictably.
universal, as evidenced by the failure of the garnet
- It is sometimes desirable to analyze "thin" 20-30
classification scheme in the Australian situation. Dis-
µm) sections of the specimens, either for convenience or
criminants based on major elements often fail to iden-
to eliminate the possibility of unobserved overlapping
tify multiple sources within a single-mineral anomaly.
grains, particularly in cases of opaque minerals. While
Chromites present a special problem, being present in a
the resultant analysis is only mildly dependent on the
wide range of igneous rocks, including komatiites,
exact thickness, absolute quantification can only be
ophiolites, gabbros and basalts which are not usually
obtained by normalization to a known concentration.
diamondiferous. Trace element data, particularly those
Optical microscopy is a necessary first step for
of incompatible elements, can be a sensitive method to
mineralogical examination of ore or geological samples,
supplement the classification scheme, reflecting pres-
if only to select or identify particular grains for detailed
sure- and temperature-controlled fractional crystalliza-
analysis. This is particularly important when one deals
tion effects during the evolution of the magma.
with an assemblage of clear minerals, e.g. silicates,
Samples of these indicators minerals collected in
unless sophisticated optical microscopy features such as
stream and soil sampling are usually minute, typically
polarisers are available on the PIXE system.
0.2-1 mm in the extreme dimensions, but those in the
An important cornerstone in establishing PIXE as a
original host rocks could be quite large (megacrysts).
routine analytical tool is a demonstration of the reliabil-
For the more typical small samples, preparations for
ity of the method. At present there is considerable
analysis involve mounting them on glass slides or set-
uncertainty in the reliability of trace element standards
ting them in araldite followed by polishing. A repre-
V. PIXE/MICROPROBES
692
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
Fe
Kimberlites
BASIC INTRUSIVES
10
Sample: Ilmenite
50
SPINELS
3 MeV protons
200 um Al filter
10
Ni
Cr
Nb
40
Zr
counts/channel
Ti
Zn
10
Ga
Cr (%)
pile-up
30
10
Mn
Lamproites
10
20
10
6.000
10.000
14.000
18.000
22.000
0
1000
2000
X-ray energy (kev)
Ni (ppm)
Fig. 1. A representative spectrum of ilmenite obtained with a
Fig. 3. Correlations between the trace element Ni in chromian
microbeam of 3 MeV protons, including the computer fit to
spinels (chromites) against the Cr content from kimberlites,
the data. The computed background, which includes the pileup
lamproites and from gabbroic intrusions show as shaded areas.
peak contribution, is also shown. Trace elements observed are
The trends observed from the gabbroic intrusions are the result
Cr, Mn, Ni, Zn, Ga, Zr and Nb at 1314, 2954, 1635, 115, 15,
of competing olivine precipitation, which depletes the melt of
286 and 339 ppm, respectively. The spectrum was obtained
Cr and Ni. Such information can be used in exploration
using a 200 µm thick Al absorber and for 0.9 µC beam charge.
programs to sort out usually nondiamondiferous gabbroic
sources of chromites.
sentative spectrum from ilmenite is shown in fig. 1,
obtained with a microbeam of 3 MeV protons. A 200
the cluster. The increase of Mg and Ni with decreasing
µm Al filter was used to enhance the detection of trace
Nb is a signature of coprecipitation of the ilmenite with
elements heavier than Fe. The major (Fe, Ti) and light
olivine and garnet, and the clustering probably reflects
minor elements (Mg) were obtained with an EMP, and
individual small batches of crystallized magma sampled
where there are overlaps (e.g. Ti, Cr and Mn) the agree-
by each kimberlite. Such data demonstrate the utility of
ment is excellent. Fig. 2 shows the relation between
certain trace element data to identify multiple sources.
trace Nb and another trace Ni and against a minor
Fig. 3 shows only the envelopes of similar groups
element Mg, for ilmenite from several South African
observed for chromites from kimberlites and lamproites,
kimberlites, and the limits of those obtained from
and from a number of gabbroic intrusive complexes
basalts. The kimberlite data are separated from the
shown as shaded areas. The distinct trends observed
basalts, and they indicate good clustering and trends in
from the gabbroic sources is the result of competing
ILMENITES
10
1500
Sekameng
8
Lemphane
Kamfersdam
Ni (ppm)
Liqhobong
1000
Kao
0880°C
Klipfontein
(%) Mg
6
Koffeefontein
00°
8
500
8
4
O
Basalts
Basalts
80
0
2
500
1000
1500
2000
2500
3000
500
1000
1500
2000
2500
Nb (ppm)
Nb (ppm)
Fig. 2. Correlations between trace Nb and another trace Ni, and against a minor element Mg for several sets of samples of ilmenite
from South African kimberlites. Limits of values obtained from basalts are also shown. Groupings of data from the same source
shown by the hand-drawn envelopes reflect the fractional crystallization and different sources of magma, and can be used to classify
unknown samples.
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
693
crystallization of olivine during the chromite precipita-
10
Sample: SARM-7
Ag
tion, depletion the melt in Cr and Ni. Systematic studies
Pd
Pt
such as this will eventually establish a more definitive
10
Au
criteria for identification of the source rocks for the
indicator minerals.
10
counts/channel
10
3.2. Platinum
10
3 MeV protons
Exploration for primary sources of platinum pre-
10
200 um Al filter
sents a challenging problem, mainly due to the still
rather poor body of knowledge on the genesis of differ-
10
ent types of PGE deposit. While there is a possibility
9.000
15.000
21.000
27.000
X-ray energy (keV)
that for certain deposits, trace elements other than the
PGE can be used in exploration, the elements them-
Fig. 4. A spectrum obtained from a silver prill prepared from
selves are often the best pathfinders. In order to develop
the SARM-7 standard reference material for platinum. The
the method it is desirable to devise a technique that
fire-assay preconcentrates the precious metals (PGE and Au)
by a factor of a few thousand. With a PIXE detection limit on
enables detection of these elements at crustal abun-
few-ppm level in the analysis of the prill, sensitivities on
dance levels (parts per billion). Detection of the PGE at
few-ppb level can be obtained for the original material. The
these levels has been carried out predominantly by
method is limited to Pt, Pd and Au. The remainder of the
neutron activation analysis (NAA), either directly or
PGEs are either partially (Ru, Rh) or completely (Os, Ir)
following a preconcentration step [7].
volatilized during the cupellation process.
Table 1
Comparison of results of prill analysis with other methods
Sample
N a)
Au
Pt
Pd
[ppm weight]
Ore sample C1
this measurement b)
3
8.5 (2.7)
0.49 (0.15)
1.60 (0.33)
all measurements c)
23
7.43 (1.97)
0.45 (0.22)
1.18 (0.52)
minᵈ)
4.15
0.23
0.60
max d)
11.73
0.60
3.20
Ore sample C2
this measurement
3
69.18 (8.5)
7.81 (1.39)
16.09 (1.17)
all measurements
53
70.89 (3.76)
6.25 (1.15)
15.50 (1.29)
min
59.47
3.29
13.13
max
77.70
8.92
17.50
MDL
0.006
0.006
0.013
Geomin standards
SS7-97/98
this measurement
2
5.64 (0.14)
1.49 (0.41)
4.96 (0.27)
all measurements
14
6.46 (0.58)
1.77 (0.29)
5.04 (0.26)
min
5.40
1.09
4.97
max
7.07
2.12
5.40
SS6-701
this measurements
1
1.354 (0.012)
-
-
all measurements
2
1.427 (0.073)
calculated e)
1.470
SS6-955
this measurement
1
1.981 (0.023)
-
-
all measurements
7
2.029 (0.025)
calculated e)
2.000
SARM-7 standard
Certified value
0.310 (0.015)
3.74 (0.045)
1.53 (0.03)
This measurement: Ag prill
0.532 (0.006)
3.13 (0.03)
1.727 (0.022)
a) Total number of analysis.
b) Mean values of results (s.d.) of the present measurements.
c) Mean values of results (s.d.) of this and other measurements.
d) Minimum and maximum of values for all measurements.
e) Calculated value, supplied by GEOMIN.
V. PIXE/MICROPROBES
694
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
At HIAF a method has been developed combining
values adopted does not reflect the much larger spread
preconcentration by fire-assay with the PIXE method,
in the individual results.
which can achieve a detection sensitivity of 5 ppb. In
The results of this test indicate that micro-PIXE
the most commonly used fire-assay [8], the precious
analysis of the prills can provide a quick and reliable
metals are extracted by fusing 20-50 g of the finely
method for PGE and Au determination, and with a
crushed ore 75 µm particle size) with litharge (PbO)
resultant minimum detection limit at the 5 ppb level,
and appropriate fluxes, at around 1000 C. The noble
the method can be readily applied to exploration.
metal collects in the resulting Pb button, which is
subsequently removed by cupellation, leaving the noble
metal residue, the prill. For low-grade material Ag is
3.3 Gold processing
normally added as the concentrator, resulting in the Ag
prill. During cupellation only Pt, Pd and Au remains;
In the beneficiation of gold ores, certain classes of
the other PGEs are either partially (Rh, Ru) or com-
ore do not yield the total gold content as determined by
pletely (Os, Ir) volatilized.
bulk assay. Part of the gold not liberated by the normal
The Ag prills ensuing from the cupellation are
cyanidization is known as refractory gold. There are a
analyzed by micro-PIXE, following a simple prepara-
number of causes of refractoriness, e.g. the presence of
tion involving flattening them is a holder, e.g. and Al
Cu minerals which consumes the leaching solution, and
disc or plate with suitably sized holes. The use of
occlusion of the gold in other minerals resistant to the
microbeams minimizes effects of the nonflatness of the
leaching solution. A more fundamental problem is the
surface. This typical prill weight in the 10-20 mg range
occurrence of gold as solid solution in other phases,
and preconcentration factors ranging from 1000 to
such as arsenopyrite or arsenous pyrite. Roasting the
10000 can be obtained. The thickness of the flattened
ore to remobilize the Au is necessary to successfully
prill is more than sufficient to stop the proton beam.
liberate the gold. Pyrrhotite and pyrite also consume the
The method was tested on a number of ore samples
cyanide, so unless they contain economic amounts of
and standards material: the SARM-7 standard [9] for
Au they should be removed from the concentrate. The
PGE analysis, and another two standards obtained lo-
Au distribution in the mill concentrate, or in the ore
cally (Geomin Pty. Ltd). Fig. 4 shows the spectrum
itself, can be determined by proton microprobe to for-
obtained from the Ag prill from the SARM-7 standard,
mulate an optimum beneficiation strategy.
including the computer fit to the data. In deriving the
In a study of one deposit, optical microscopy of
final concentrations of the elements in the prill, an
polished sections indicates that only ~ 20% of the gold
iterative procedure was followed to ensure a self-con-
assayed is present as free gold. The quartz- and
sistent result for the matrix. This is particularly im-
dolomite-hosted deposit contains sulfide minerals, with
portant for analysis of ore grade material. The homo-
pyrrhotite being the dominant phase at around 10%
geneity of the prill was tested by several spot analyses
abundance. Minor phases is order of decreasing abun-
on the same prill.
dance include pyrite ~ 1%), arsenopyrite 1%),
Table 1 shows the results for the ore samples, and
chalcopyrite, sphalerite and rare galena and pentlandite.
the GEOMIN standards, including those from other
Initial mineralogical and metallurgical tests suggested a
analyses carried out by conventional methods (NAA,
concentration of gold into the arsenopyrite relative to
optical emission and absorption spectroscopy), are also
the pyrrhotite and pyrite. It was difficult to draw firm
shown. Most of the present results agree well with the
conclusions from such tests due to the intergrown na-
other measurements. However, the results for the
ture of the ore. In order to sort out this problem, the
SARM-7 standard show significant discrepancies with
proton microprobe was applied to study the distribution
the certified values [9]. This may be attributable to
of the gold in pyrite, pyrrhotite and arsenopyrite phases
possible sample inhomogeneity and variation in the
in the sample.
fire-assay collection efficiency. The sample inhomogene-
Fig. 5 shows the spectra obtained from a selection of
ity is plausible, considering that the platinum group
arsenopyrite grains in polished samples of the ore.
minerals are considerably heavier than the silicate ma-
Analysis of the pyrite and pyrrhotite grains show the
trix, and some settling effect can occur. In the fire
same suite of trace elements, and As (table 2).
assay, the effect of the flow of air in the furnace during
The results confirm arsenopyrite as the main carrier
fusion was known to produce variation in the collection
of gold. The gold content, however, varies considerably
efficiency [10]. However, the good agreement between
in the 12 grains selected for this study, and ranges from
the results for the other samples and other measure-
below detection limit (40 ppm) to 405 ppm. An average
ments imply that this is not likely in the present case.
of 160 ppm was obtained from all grains. Zn can
One other point to be considered also is that, although
interfere with the detection of gold, due to the closeness
the certified values of the SARM-7 were arrived at
of the energy of the Zn Kβ line (9.572 keV) and the Lα
through a round-robin analysis [9], the narrow range of
line of gold (9.711 keV). In the present sample Zn only
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
695
gives low levels of As (10-75 ppm) and Se (18-67 ppm).
10
Arsenopyrite
Gold values obtained are unusually at or below detec-
10
As
3 MeV protons
tion limit of 13 ppm of the individual runs. Analysis of
Fe
200 um Al filter
the sum of all runs gives a 7 ppm average with a 5 ppm
10
detection limit.
counts/channel
S
10
Cu
Zn
pile-up peaks
In arsenopyrite, Sb can substitute for As, and in the
Au
present case it occurs at trace levels varying from 197 to
10
(3)
Sb
830 ppm. Both As and Sb affect the precipitation of
10
Au; as is believed to form a bond with Au in arsenopyrite
10
[12] while Sb is thought to be anticorrelated with Au.
(2)
(1)
The present data do not show such definite correlations.
10
Another feature of the data is the relatively high level of
10
Se between 116 and 400 ppm, usually associated with
6.000
12.000
18.000
24.000
30.000
X-ray energy (keV)
polymetallic-type deposits [13]. This trace element com-
bined with sulfur data, can be used to determine the
Fig. 5. A selection of X-ray spectra obtained from individual
arsenopyrite grains in a refractory ore sample analyzed with a
temperature in the ore paragenesis.
3 MeV proton microbeam. Grains 1, 2 and 3 contain 0, 110
and 405 ppm gold, respectively. A minimum detection limit of
3.4. Silver
40 ppm is obtained, limited by the interference of the low-en-
ergy "tail" of the As Kα line. The Ni, Cu, Zn and S in grain 3
This precious metal is commonly obtained as a by-
are 280, 380, 165 and 200 ppm, respectively. For pyrite and
product of mass-metal (Zn, Cu, Pb) ore processing, with
pyrrhotite a minimum detection limit of 5 ppm can be ob-
sulfide ores being the main source. Significant amounts
tained.
of Ag, however, may be lost to the tailings. Silver occurs
either as silver minerals (tetrahedrite, freibergite) or as
solid solution in other sulfide minerals such as galena
occurs at levels generally below 20 ppm, eliminating the
and chalcopyrite. Efficiency of recovery depends cru-
potential problem.
cially on the knowledge to its distribution in the various
The pyrite analysis from the same ore sample shows
phases. Improvement in the recovery of Ag by a few
a high level of arsenic (averaging - 1000 ppm), al-
tens of ppm can translate into substantial additional
though the values vary from as low as 12 ppm to as high
revenue, considering the usually large volume of ore
as 1%. Inclusions of arsenopyrite in the latter cannot be
processed.
ruled out. The gold content from individual measure-
As solid solution, Ag occurs at levels as high as a few
ments shows levels slightly above the detection limit of
thousand ppm, for which electron probe analysis is
10 ppm. Analysis of the sum of runs on 16 grains gives
quite adequate. However, at around 100 ppm it is still
an average value of 9 ppm with 5 ppm detection limit.
economic to recover, but below the detection limit of
For the majority of grains Au values do not correlate
electron microprobes. Cabri et al. [14] determined the
with As values. Sb is not detectable (≤ 8 ppm), while Se
distribution of Ag and other trace elements in several
varies from 18 to 76 ppm. Analysis of the pyrrhotite
massive sulfide deposits. While galena was confirmed as
the most common carrier of silver, other phases such as
chalcopyrite can also be important carriers [15].
Table 2
In a study of a mill concentrate, bulk analysis re-
Summary of trace element concentrations [ppm] in a
vealed a strong correlation between silver and Pb con-
gold-bearing ore sample
tent, shown in fig. 6. The proton microprobe was ap-
Arsenopyrite
Pyrite
Pyrrhotite
plied to study the distribution in the sample. The mill
No. of grains
concentrate sample is set in araldite and polished for
analyzed
12
16
16
presentation to the beam. Fig. 7 shows a typical view of
Au range
0- 405
0- 74
0- 36
the sample, which consists of fragments of the sulfide
Average, (MDL)
162 (40)
9 (5)
7 (5)
and some gangue minerals recovered from the flotation
Ni
521- 800
0- 909
43-1790
circuit. Typical size of the fragments is 150 X 50 µm²,
Cu
241-1580
0- 85
0- 29
and there is some probability that the thickness is less
Zn
113- 483
0- 381
0- 24
than 50 µ m. The polished surface (25 mm diameter)
Ga
44- 115
0- 17
0- 26
contains approximately 50000 grains which were first
As
11-1760
10- 34
scanned by optical microscopy at intermediate magnifi-
Se
116- 400
18- 76
56- 121
Sb
197- 505
cation. The major constituents in decreasing abundance
Pb
0- 29
0- 58
are galena, sphalerite and gangue. Minor minerals pre-
sent include chalcopyrite pyrrhotite, tetrahedrite.
V. PIXE/MICROPROBES
696
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
70
10
SAMPLE T1
Sample: T1 concentrate
10
Pb
60
Pb
3 MeV protons
Zn
10
100 um A1,25 um Cr filters
Cu X 100
Sn
50
10
Ag
Fe
Cd
Sb
Te
A
counts/channel
10
Zn
galena
A
Concentration, %
40
10
30
10
Cu
sphalerite
4
10
20
10
chalcopyrite
10
10
0
B
9.000
15.000
21.000
27.000
33.000
R
X-ray energy (keV)
0
100
200
300
400
500
600
Fig. 8. Representative spectra from monomineralic fragments
Ag (ppm)
in the mill concentrate sample. Galena is a major component
Fig. 6. Graph of the silver content against the various major
in the concentrate and can be seen to contain Ag as well as
elements of the base-metal sulfides in a sample of mill con-
other traces. Sphalerite contains mainly Cd, and the minor
centrate. A strong correlation with Pb can be seen, suggesting
component of chalcopyrite contains a significant amount of
association of silver with galena. This is confirmed by the
silver.
proton microprobe analysis of monomineralic constituents of
the sample.
Ag; instead, Cd is the main trace element at 530 ppm to
0.17% weight. Trace Cd as well as Sb, Sn and Te are
Representative spectra from individual monominer-
also observed in galena. Combined with a modal analy-
alic fragments are shown in fig. 8, and a summary of the
sis, the trace Ag distribution can be used to evaluate the
results is shown in table 3. It confirms galena as a main
efficiency of the beneficiation process.
carrier of Ag, at levels of 400-800 ppm. The average is
The distribution of the trace elements, particularly
596 ppm, in good agreement with the Ag/Pb value of
Ag, Sb and Bi (not observed, however, in the present
~ 680 ppm obtained from the bulk analysis. The zero
case), can provide information on the ore genesis and
Pb intercept in fig. 6 at ~ 150 ppm Ag indicates the Ag
metamorphism. The presence of Sb and Bi increases the
content in other phases. The graph does not indicate
solubility of Ag in galena, representing coupled sub-
linear correlation between Ag and Cu, as chalcopyrite is
stitution with valence balance of AgBi(Sb) for 2Pb. The
only a minor component in the concentrate. The Ag
ratio of Ag/(Sb + Bi) can be used to deduce the equi-
content of chalcopyrite is only revealed by the proton
libration temperature of galena, reflecting the metamor-
microprobe analysis, with values ranging from 210 to
phic or depositional temperature [16]. The detection
940 ppm. In this sample, sphalerite does not contain
limit for Bi in galena is relatively poor due to the
interference of the Pb lines. With better resolution
detectors, e.g. a wavelength-dispersive spectrometer, a
more precise determination of this ratio can be made to
test existing models of the genesis of massive sulfide
deposits.
Table 3
Summary of trace element concentrations [ppm] in a mixed
sulfide mill concentrate sample
Galena
Sphalerite
Chalcopyrite
No. of grains
analyzed
9
4
5
Ag range
324-
830
< 40- 135
213-920
Average, (MDL)
596 (40)
60 (40)
643 (50)
Cu
2600-26000
1300-8600
Fig. 7. A micrograph of a typical polished section made from a
Cd
90- 375
530-1700
< 50- 80
mill concentrate set in araldite. Fragments of separated miner-
Sn
< 80
210-420
als from the crushed ore are typically between 100 and 150
Sb
388- 2800
< 100
< 70
µ m.
S.H. Sie et al. / The proton microprobe in mineral exploration and processing
697
4. Discussion and conclusion
References
The examples cited above illustrate the utility of
PIXE with microbeams in mineral-related problems.
[1] S.H. Sie, Nucl. Instr. and Meth. B10/11 (1985) 664.
[2] L.J. Cabri, Nucl. Instr. and Meth. B30 (1988) 459.
Trace element data in Pt-, Au-, and Ag-bearing deposits
[3] S.H. Sie and C.G. Ryan, Nucl. Instr. and Meth. B15
are useful both in beneficiation as well as in studies of
(1986) 664.
the genesis of the deposit, which in turn can aid ex-
[4] W.L. Griffin, L. Jacques, S.H. Sie, C.G. Ryan, D.R.
ploration strategy. Some of the data cannot be obtained
Cousens and G.F. Suter, Contr. Mineralogy and Petrology
by any other means, while some methods, e.g. the
99 (1988) 143.
detection of Pt and Au at crustal abundances, provide
[5] C.G. Ryan, E. Clayton, W.L. Griffin, S.H. Sie and D.R.
an alternative and more convenient method. Invariably,
Cousens, Nucl. Instr. and Meth. B34 (1988) 396.
however, large numbers of samples have to be analyzed
[6] D.R. Cousens, C.G. Ryan, S.H. Sie and W.L. Griffin, to
and often the time factor is important in both explora-
be published in Nucl. Instr. and Meth.
tion and beneficiation tests. Both require appropriate
C.G. Ryan et al., to be published in Nucl. Instr. and
Meth.
design of the hardware and software, and the cost factor
[7] J.H. Crocket and L.J. Cabri, in: Platinum group Ele-
can be further reduced through increased utilization of
ments: Mineralogy, Geology and Recovery, ed. L.J. Cabri,
the facility and further technical improvements. Some
Canadian Institute of Mining and Metallurgy special
can be readily achieved: e.g. adding another detector
volume 23 (1981) 71.
would immediately double the counting efficiency. Fur-
[8] J. Haffty, L.B. Riley and W.D. Goss, A Manual on Fire
ther developments are directed towards improving de-
Assaying and Determination of Noble Metals in Geologi-
tection limits through better resolution or development
cal Materials, Geological Survey Bulletin 1445 (US Dept.
of alternative methods. Current development at HIAF
of Interior, 1977).
includes:
[9] T.W. Steele, J. Levin and I. Copelowitz, Report no.
- WDS spectrometers: in PIXE interference can con-
1696-1975 of National Inst. of Metallurgy, South Africa,
1975.
tribute significantly, if not dominate the MDL. WDS
[10] E. Van Wijk and K. Dixon, Report no. M88, Mintek,
spectrometers offer much better energy resolution, but
South Africa, 1983.
at the expense of detection efficiency. Development of a
[11] P.M. Swash and P. Ellis, Proc. Int. Conf. on Gold, volume
high-current microprobe may be required alongside this
2: Extractive Metallurgy of Gold, Johannesburg, South
development. Areas which will benefit include detection
Africa (SAIMM, 1986) p. 235.
of PGE, Au and rare-earth elements.
[12] M. Cathelineau, M.C. Boiron, Ph. Holliger and Ph. Ma-
- Improvement in detection limit can also be achieved
rion, Proc. Bicentennial Gold '88 Conf, Melbourne, 1988
by selective X-ray excitation, exploitating the phenome-
(Geological Society of Australia) p. 235.
non of molecular orbital electron promotion induced by
[13] R.W. Boyle, GSC Bulletin no. 280 (Energy Mines and
heavy-ion beams [17].
Resource Canada, Ottawa, 1983).
[14] L.J. Cabri, J.L. Campbell, J.H. Gilles Laflamme, R.G.
Widespread acceptance of the proton-microprobe-
Leight, J.A. Maxwell and J.D. Scott, Can. Mineralogist 23
based methodology by the minerals industry is contin-
(1985) 133.
gent upon the factors discussed above, as well as con-
[15] D.C. Harris, L.J. Cabri and R. Nobiling, Can. Mineralo-
tinuing accumulation of case histories. Applications of
gist 22 (1984) 493.
the other accelerator-based methods such as AMS, RBS
[16] O. Amcoff, Minerallium Deposita 19 (1984) 63.
and NRA remain to be developed and exploited. AMS
[17] U. Fano and W. Lichten, Phys. Rev. Lett. 14 (1965) 627.
has been shown to be capable of detecting trace element
[18] J.C. Rucklidge et al., Nucl. Instr. and Meth. 191 (1981) 1.
in the ppb range [18]. This method will also allow
in-situ analysis of the isotopic composition of many
trace elements. Application in minerals exploration is
contingent upon the development of a microprobing ion
source to enable analysis of individual mineral grains.
V. PIXE/MICROPROBES
318
Nuclear Instruments and Methods in Physics Research B49 (1990) 318-322
North-Holland
APPLICATION OF THE PROTON MICROPROBE TO DIAMOND EXPLORATION AND GENESIS
W.L. GRIFFIN, C.G. RYAN, D.R. COUSENS, S.H. SIE and G.F. SUTER
Heavy Ion Analytical Facility (HIAF), CSIRO Division of Exploration Geoscience, North Ryde, NSW 2113, Australia
The HIAF proton microprobe is being used to analyze trace elements in mantle-derived minerals, including garnets, ilmenites,
and chromites. The goals are to understand mantle processes and to improve the use of indicator minerals in diamond exploration
programs. Interpretation of the data provides new information on magma compositions and fractionation mechanisms, metasomatic
processes, time scales of heating and melt infiltration, and the environment of diamond formation. Trace-element data on indicator
minerals improve discrimination between barren and diamondiferous source rocks, and help to recognize the presence of multiple
source rocks within one drainage; they will also ultimately help to improve the models that guide exploration.
1. Introduction
2. Methods
The analytical methods used in this work have been
Diamonds are formed at depths of more than 150
km in the Earth's mantle, and carried to the surface
reported elsewhere [1,2] and a detailed treatment of the
during volcanic eruptions of special rock types, such as
HIAF hardware and software is given by Ryan et al.
kimberlite or lamproite. The diamond content of such
[3-5]. Mineralogical applications of the proton micro-
rocks is typically a few ppm. Exploration for diamonds
probe, especially those reported here, require large num-
therefore is heavily based on the recognition of more
bers of accurate, high-precision analyses. The HIAF
abundant mantle-derived "indicator minerals" (Cr-py-
hardware [6] has been specifically designed to allow
rope garnet, Mg-rich ilmenite, chromite) in samples of
high sample throughput, with high beam currents for
soil and stream sediments.
low detection limits, flexible sample handling and
Electron microprobe analyses of indicator minerals
minimum cycling times for sample changes. The soft-
give the major-element composition of individual grains.
ware development has concentrated on ease of use and
These data are used during exploration and during
reliability of data treatment, with special attention given
evaluation of prospects, to assess the probability that
to the development of stable background algorithms for
particular samples are derived from diamondiferous
the reproducible treatment of low-statistics peaks [3,5].
rocks. However, this method is commonly ambiguous,
For most of the PIXE microanalysis reported here, a 8
because minerals of similar major-element composition
nA 3 MeV proton beam was used, with a beam spot size
also may be derived from a range of barren rock types.
of 20 µ m. A 200 µm Al X-ray absorber is usually
Since 1987, HIAF has carried out a program of
selected to attenuate major-element lines. The typical
proton microprobe analysis of trace elements in indica-
integrated charge was 3 µC, corresponding to an
tor minerals, aimed at adding another level of dis-
acquisition time of 6 min per grain.
crimination to this exploration method. Much of the
material being analyzed consists of heavy-mineral con-
centrates from diamondiferous and barren sources, to
3. Results
provide empirical discriminants. However, we are also
analyzing the minerals in fragments of mantle rocks
3.1. Garnets
(xenoliths and megacrysts) carried to the surface by
kimberlites, and the mineral inclusions enclosed within
The grains of Cr-pyrope garnet ((Mg, Fe)₃-
diamonds. These studies provide insights into rock-for-
(Al, Cr)₂Si₃O₁₂) found in heavy-mineral concentrates
ming processes in the mantle, including those responsi-
from volcanic rocks are derived largely from the disag-
ble for the formation of diamond, and help us to
gregation of xenoliths of mantle wall rocks such as
interpret compositional features seen in the concentrate
garnet peridotite. Griffin et al. [7] showed that the
samples. This report will emphasize results from the
distribution of Ni between Cr-pyrope garnet and olivine
studies of xenoliths and inclusions in diamond.
in such xenoliths is strongly dependent on T, as mea-
0168-583X/90/$03.50 © Elsevier Science Publishers B.V.
(North-Holland)
W.L. Griffin et al. / Application of the proton microprobe to diamond exploration
319
10
concluded that infiltration of magma had produced
Ni as measured
overgrowths on garnets in sheared peridotite xenoliths,
*
(r=-0.98)
and strongly modified the composition of the rocks.
Modelling of zoning profiles indicated that geologically
very short time scales, on the order of tens to hundreds
of years prior to eruption, were involved. The results
100(GNT/OLIV)
1.0
have important consequences for models of mantle
*
1400
1200
1000
800
600°C
0.1
0.5
0.6
0.7
0.9
KAMFERSDAM
0.8
1.0
1.1
(high-grade)
1000/T,K
Fig. 1. Partitioning of Ni between olivine and Cr-pyrope
garnet, as a function of temperature (T; determined by two-py-
roxene or olivine-garnet thermometry). Stars, peridotite xeno-
liths; circles, olivine inclusions in garnet grains; triangles,
olivine-garnet pairs from single diamonds [1]. From ref. [7].
800
1000
1200
1400 °C
sured by two-pyroxene thermometry (fig. 1). In these
ultramafic rocks, the Ni content of olivine is essentially
constant (2900 ± 200 ppm), while the Ni content of the
garnet varies from < 20 ppm to > 120 ppm over the T
range 600-1400 C. This makes it possible to estimate
the equilibration T of a single garnet grain simply by
GRAPHITE
DIAMOND
analyzing its Ni content; the estimated uncertainty is
< 100° C.
This "Ni thermometer" has important potential as
KLIPFONTEIN
(low grade)
an exploration tool. The temperature-vs-depth relation
(the "geotherm") is reasonably well-constrained in the
stable continental areas (cratons), where most diamond
exploration is concentrated. In such cratons, diamonds
are only stable at depths greater than those correspond-
ing to T of ~ 1000° A kimberlite pipe or other
600
800
1000
1200
1400 °C
volcanic rock will ony be a potential diamond carrier if
it has originated below this depth and carries a signifi-
cant proportion of mantle material equilibrated at T>
1000 C. Thus the probability that a population of
garnets comes from a diamond-bearing pipe may be in
part assessed by studying the distribution of Ni-temper-
GRAPHITE
DIAMOND
MOSES ROCK
(barren)
atures in the population (fig. 2).
The Ni thermometer may also be used to identify
short-lived heating and cooling episodes in the mantle,
by studying the zoning of Ni within individual garnet
grains. Smith et al. [8] used Ni zoning in garnets of
xenoliths from the Colorado Plateau to calculate heat-
600
800
1000
1200
1400° °C
ing rates of 0.1-0.01° C/yr over a period of about
10000 years. These zoning profiles were frozen in when
Fig. 2. Histograms of T estimates derived from single garnet
grains in heavy-mineral concentrates from two African
the xenolith was entrained in the magma and erupted
kimberlites of differing diamond content, and the barren Mo-
rapidly to the surface.
ses Rock diatreme (Arizona). Shaded area, subcalcic garnets.
Garnet grains zoned in other elements, such as Zr,
The diamond/graphite line represents the intersection of a
Ti, Y and Ga, provide evidence on the movement of
normal continental geotherm with the diamond-graphite equi-
mantle melts through shear zones. Griffin et al. [2]
librium curve.
V. GEOLOGICAL/ARCHAEOLOGICAL APPLICATIONS
320
W.L. Griffin et al. / Application of the proton microprobe to diamond exploration
Nb
Nb
a
b
3000
3000
Z+
concentration (ppm)
2000
concentration (ppm)
2000
02+
1000
1000
S-
Zr
Ni
0
500
1000
1500
0
500
1000
1500
concentration (ppm)
concentration (ppm)
Fig. 3. Plots of Ni and Zr VS Nb in ilmenite megacrysts from the Frank Smith kimberlite pipe, South Africa. Nb increases
continuously during fractionation of the magma; inflections in the curves reflect changes in the coprecipitating minerals. Z+,
beginning of zircon crystallization; S-, cessation of pyroxene + garnet + olivine crystallization; O2+, + beginning of second olivine
crystallization. From ref. [10].
evolution; they demonstrate that the unusual composi-
slightly different. The result has significant implications
tions of these xenoliths are not, as commonly assumed,
for exploration strategies; it may be possible to tell
representative of long-lived mantle reservoirs.
from analysis of an ilmenite concentrate how many
kimberlite bodies are to be found within an exploration
3.2. Ilmenites
area. It is also an important argument in favour of a
genetic relationship between the ilmenite-forming
Many kimberlites carry abundant megacrysts (> 2
magma and the kimberlite which brought the ilmenites
mm diameter) of magnesian ilmenite ((Fe, Mg)TiO₃),
to the surface.
which is resistant to weathering and transport, and
Many non-diamondiferous alkalic basalts carry mag-
serves as an indicator mineral. The origin of the ilmenite,
nesian ilmenites that overlap the major-element com-
and its genetic relation to the kimberlite, is a matter of
positional range of kimberlite ilmenites, and these pose
considerable debate. Trace-element studies of ilmenites
a serious exploration problem. However, preliminary
from individual kimberlites typically show well-defined
studies of basaltic Mg-ilmenites suggest that they have
interelement trends (fig. 3). These are easily interpreted
low contents of Ni, Zr and Nb compared to kimberlitic
in terms of fractional crystallization of single batches of
ones, and that the interelement relationships are differ-
magma, in which crystallizing phases are removed from
ent as well. These results suggest that the basaltic
the magma (for example, by sinking) to form cumulate
ilmenites are formed either from different magma types,
rocks. In a detailed study of ilmenites and coexisting
or under different P-T conditions, or both. A separate
silicate phases from the Monastery Mine kimberlite,
project is underway at HIAF to examine this problem.
Moore et al. [9] have shown that Nb behaves incompati-
bly, remaining concentrated in the liquid phase. Hence
3.3. Chromites
the Nb content of the ilmenites increases steadily
throughout the fractionation sequence, while the con-
Chrome spinels ((Fe, Mg)(Cr, Al)₂O₄) with high Cr
tents of other elements, such as Ni, Zr, Ga and Ta, vary
contents 40%) are widely used as indicators of
according to the nature of the coprecipitating phases
kimberlites or lamproites, especially in deeply weathered
(cf. fig. 3). In effect, the ilmenite serves as a monitor of
terrains such as Australia, where garnet and ilmenite
the evolving composition of the magma.
may not survive. However, their meaning is commonly
In a broader study of ilmenite suites from 20 African
ambiguous: spinels with lower Cr content also occur in
kimberlites, Griffin et al. [10] found trends generally
kimberlites and lamproites, and high-Cr spinels may be
similar to those shown in fig. 3, but with clear dif-
shed from a wide variety of non-diamondiferous rocks,
ferences from pipe to pipe. In general, each kimberlite
including peridotite bodies, greenstones and gabbros.
appears to contain ilmenites derived from a single batch
Chromites contain relatively few trace elements that
of magma, and the compositions of these magmas are
can be analyzed by PIXE; Ni, Zn and Ga are the most
W.L. Griffin et al. / Application of the proton microprobe to diamond exploration
321
60%
100
Cr
KIMBERLITE SPINELS
Ga
KIMBERLITE SPINELS
(n 400)
a
(n 400)
b
Contours: 98%
Contours: 98%
80
85%
85%
50%
50%
20%
*
20%
40%
60
40
20%
20
*
Ni
Ni
0
0
500
1000
1500
2000
0
500
1000
1500
2000
Fig. 4. Distribution of Cr, Ni and Ga in 400 chromites from African kimberlites. Dashed countour encloses 98% of data points; other
contours are 85%, 50%, 20%. (Griffin and Gurney, unpublished data.)
abundant. However, when combined with the major-ele-
history of the diamond; they carry important informa-
ment data from the electron microprobe, these elements
tion on the environment and processes of diamond
can provide useful discriminants. The compositional
formation. These inclusions can be classified into two
range of kimberlite chromites has been defined through
suites, corresponding to the two major mantle rock
analysis of more than 400 samples (fig. 4). While spinels
types. The peridotite suite is dominated by olivine,
from other sources may also lie within this range for
Cr-rich garnet and Cr-rich chromite; the eclogite suite is
individual element pairs, their interelement relations are
dominated by sodic clinopyroxene and low-Cr, often
typically different. Multivariate analysis of this data-
Fe-rich, garnets.
base will ultimately provide a screening procedure for
Griffin et al. [14] used Ni thermometry to demon-
classification of individual grains from exploration sam-
strate that some peridotite-suite garnets were trapped at
ples.
unusually high 1300° C), suggesting formation in
thermal aureoles around deep-seated magma bodies,
3.4. Element partitioning
and possibly in the presence of melt. Most other garnet
inclusions give temperatures consistent with formation
Data on trace-element partitioning between coexist-
at similar depths, but lower T, and thus in the solid
ing phases are potentially of great importance not only
state. They also found that the trace-element patterns of
in geothermobarometry [7], but in testing for equi-
one group of low-Ca garnets requires a two-stage evolu-
librium, modelling of partial melting and fractional
tion; an overall depletion of the mantle rocks in low-
crystallization, and understanding of metasomatism in
melting components was followed by equilibration with
the mantle. Griffin et al. [1,11,12] have analyzed the
a carbonate-rich melt or fluid.
effects of pressure, temperature and composition on
A study of eclogite-suite inclusions in diamonds
partitioning of trace elements between phases of eclo-
from the Argyle mine (Australia) provided further evi-
gites and peridotites. O'Reilly et al. [13] have studied
dence for high formation temperatures [1]. This study
the distribution of trace elements between the minerals
also showed that several inclusions of garnet and pyrox-
of metasomatized spinel peridotite xenoliths, and dem-
ene within single diamonds were not in compositional
onstrated the importance of crystal chemistry in con-
equilibrium when they were trapped. The results were
trolling the trace-element composition of rocks formed
interpreted as showing crystallization of diamond in an
in open systems.
open system that was undergoing rapid compositional
change. Moore et al. [15] showed that the trace-element
3.5. Inclusions in diamond
compositions of eclogite-suite inclusions in Monastery
Mine diamonds do not match those of minerals in
Mineral phases trapped during the growth of a di-
eclogite xenoliths from the same mine. These data sug-
amond crystal are shielded from compositional change
gest that metasomatic processes have modified the com-
or other physical modification during the subsequent
positions of mantle rocks following the crystallization of
V. GEOLOGICAL/ARCHAEOLOGICAL APPLICATIONS
322
W.L. Griffin et al. / Application of the proton microprobe to diamond exploration
diamond. McCandless et al. [16] showed that different
[2] W.L. Griffin, D. Smith, F.R. Boyd, D.R. Cousens, C.G.
varieties of diamond from the Orapa mine contain
Ryan, S.H. Sie and G.F. Suter, Geochim. Cosmochim.
similar types of garnet inclusions.
Acta 53 (1989) 561.
[3] C.G. Ryan, E. Clayton, W.L. Griffin, S.H. Sie and D.R.
Cousens, Nucl. Instr. and Meth. B34 (1988) 396.
[4] C.G. Ryan, D.R. Cousens, S.H. Sie, W.L. Griffin and E.
4. Conclusion
Clayton, Nucl. Instr. and Meth. B47 (1990) 55.
[5] C.G. Ryan, D.R. Cousens, S.H. Sie and W.L. Griffin,
Trace-element studies of heavy-mineral concentrates
these Proceedings (5th Int. Conf. on PIXE Amsterdam,
and xenolith material are providing tools for the dis-
The Netherlands, 1989) Nucl. Instr. and Meth. B49 (1990)
crimination of barren and diamondiferous source rocks,
271.
and for recognizing the presence of multiple sources
[6] S.H. Sie and C.G. Ryan, Nucl. Instr. and Meth. B15
within an exploration area. Studies of mantle-derived
(1986) 664.
xenoliths and macrocryst suites provide information on
[7] W.L. Griffin, C.G. Ryan, D.R. Cousens, S.H. Sie and
mantle processes, including those important for di-
G.F. Suter, Contr. Mineral. Petrol. 103 (1989) 199.
[8] D. Smith, W.L. Griffin, C.G. Ryan, D.R. Cousens, S.H.
amond formation. The data are pertinent to determin-
Sie and G.F. Suter, to be submitted to Contr. Mineral.
ing the types of magmas present, and their crystalli-
Petrol.
zation histories; the interaction between magmas and
[9] R.O. Moore, W.L. Griffin, J.J. Gurney, C.G. Ryan, D.R.
their wall rocks; and the relationship between the
Cousens, S.H. Sie and G.F. Suter, to be submitted to
'megacryst magma" and kimberlite. Especially exciting
Contr. Mineral. Petrol.
is the information on time scales which is becoming
[10] W.L. Griffin, R.O. Moore, J.J. Gurney, C.G. Ryan, S.H.
available through proton-probe studies of trace-element
Sie and G.F. Suter, to be submitted to Contr. Mineral.
zoning in garnets and other phases. Studies of inclu-
Petrol.
sions in diamonds are providing important information
[11] W.L. Griffin, D. Smith, C.G. Ryan, S.H. Sie and G.F.
on the environment of diamond formation, and on
Suter, to be submitted to Geochim. Cosmochim. Acta.
[12] W.L. Griffin, S.Y. O'Reilly, D.R. Cousens, C.G. Ryan,
metasomatic processes through time.
S.H. Sie and G.F. Suter, Terra Abstracts 1 (1989) 9.
Ultimately, understanding of the mantle processes
[13] S.Y. O'Reilly, W.L. Griffin, C.G. Ryan, D.R. Cousens,
that control the formation of diamond, kimberlite and
S.H. Sie and G.F. Suter, Trans. 28th Int. Geol. Cong.
other diamondiferous rocks will lead to better explora-
(1989) 2-535.
tion models for locating primary deposits of diamonds.
[14] W.L. Griffin, J.J. Curney, C.G. Ryan, D.R. Cousens, S.H.
Proton-microprobe studies are making a significant con-
Sie and G.F. Suter, 28th Int. Geol. Congr. (Diamond
tribution to that understanding.
workshop), Extended Abstracts (1989) p. 23.
[15] R.O. Moore, J.J. Gurney and W.L. Griffin, ibid., p. 65.
[16] T.E. McCandless, M.B. Kirkley, D.N. Robinson, J.J. Gur-
References
ney, W.L. Griffin, D.R. Cousens and F.R. Boyd, ibid., p.
47.
[1] W.L. Griffin, A.L. Jaques, S.H. Sie, C.G. Ryan, D.R.
Cousens and G.F. Suter, Contr. Mineral. Petrol. 99 (1988)
143.
284
Nuclear Instruments and Methods in Physics Research B54 (1991) 284-291
North-Holland
Section VIII. Geological and mineralogical applications
The proton microprobe: a revolution in mineral analysis
S.H. Sie, W.L. Griffin, C.G. Ryan, G.F. Suter and D.R. Cousens
1
Heavy Ion Analytical Facility (HIAF), CSIRO Division of Exploration Geoscience, P.O. Box 136, N. Ryde, NSW 2113, Australia
Application of the proton microprobe as a quantitative tool for trace-element microanalysis in the geosciences can be considered
to have crossed the threshold of acceptability in a number of areas, particularly in igneous and metamorphic mineralogy and
petrology. In the minerals industry, applications in base metal ore mineralogy provide new data useful for both processing and
genetic studies. Applications in diamond and gold exploration are developing into new methods, with potential widespread
acceptance. The paper will review a few case histories, and discuss the limitations of the current state-of-art and conditions conducive
to widespread acceptance by geoscientists and by the minerals industry.
1. Introduction
an appropriate niche in igneous mineralogy and pe-
trology, marked by contribution to advances in the
The anticipated benefits of the proton microprobe
mainstream areas. In sulfide mineralogy, trace-element
applications in the geoscience have been realized in an
data have contributed to the understanding of ore gene-
ever increasing number of areas, marked by the progres-
sis and found direct application in exploration and
sion from experimentation to routine application of the
processing of base metal ores. The present paper re-
technique. Better access to accelerator facilities by geo-
views the potential and constraints of analytical micro-
scientists, close links between physicists and geoscien-
PIXE, and presents a few case histories for illustration.
tists, and dedicated facilities are requisites of this pro-
gress. Such conditions apply in a number of laborato-
ries, notably at Heidelberg, Witwatersrand and Los
Alamos [1-3]. HIAF is an example of a dedicated
facility, established to enable sustained development of
the applications in the geosciences, and promote the
2. The proton microprobe
introduction of accelerator-based analytical methods
into the mineral industry [4]. This includes not only the
The applications of the proton microprobe in general
proton microprobe [5], but other ion beam analysis
have developed along two virtually separate lines. In
(IBA) methods and accelerator mass spectrometry
one the emphasis is on imaging and on the attainment
(AMS) as well. In Australia this is warranted by the
of the best resolution, with the scanning mode as the
important role of the mineral industry in the national
main mode of operation [7,8]. The other concentrates
economy.
on its use as a quantitative microanalytical tool [6,9],
The statistical nature of geological samples and data
with resolution considered as a second priority. The
requires analysis of large numbers of samples, and the
latter has been the line adopted at HIAF for geoscien-
interpretation often depends critically on the accuracy
tific applications. Progress in this has been reviewed in
of the data. Speed of analysis governs the viability of
a number of recent papers [11-13], and is the subject of
the method, particularly in the industrial context, affect-
the present paper.
ing among others the cost factor. With appropriate
One emerging conclusion is that quantitative micro-
design of both hardware [5] and software [6] these
PIXE in the geosciences has graduated from being an
requirements can be fulfilled successfully.
experimental tool, into a vital tool for the progress in a
While experimentation continues, significant pro-
number of specific areas. The successes achieved thus
gress has been achieved over the past few years. In
far have been based mainly on adaptation of electron
particular, quantitative analytical micro-PIXE has found
microbeam methodology, i.e. nondestructive in-situ
trace-element analysis by induced X-ray spectrometry.
The better sensitivity (as low as <1 ppm) afforded by
the lower bremsstrahlung revealed new information
1 Present address: Electron Microscopy Unit, Queensland
hitherto inaccessible or tedious to obtain. However, one
University of Technology, Brisbane, Qld., Australia.
has to be continually aware of alternative [14], and
0168-583X/91/$03.50 © 1991 Elsevier Science Publishers B.V. (North-Holland)
S.H. Sie et al. / The proton microprobe in mineral analysis
285
possible less expensive methods in choosing the proton
current reported at 1 µm resolution is 100 pA [7,8], at
microprobe as a viable tool.
which point the chromatic aberration dominates. With
While the proton microprobe methodology for
achromatic systems [17], the resolution could be im-
mineralogical analysis can be considered as derivative
proved in principle, but in practice spherical aberration
of that of the electron microprobe, it is instructive to
and parasitic aberrations due to imperfect construction
consider the contrast, and in many instances the com-
of the lens can dominate and limit the beam currents
plementarity of the two methods:
achievable at micron resolution. At HIAF, the micro-
- Sample size and preparation: The effective depth
probe is based on an electrostatic "Russian" quadruplet
of analysis is ~ 5 µm for electron beams with energies
system [5,16], a 100 pA proton beam with 3 µm resolu-
15-30 keV, typical for electron probes. For 2-4 MeV
tion was achieved with a 32 µm object aperture and 0.5
protons typically used in PIXE measurements, the effec-
mm diameter lens aperture. A practical beam current
tive depth of analysis varies between 10 and 30 µm,
for quantitative trace-element analysis of 10 nA can be
depending on the mineral. Smoothness of the sample
obtained with - 20 µm beam spot.
surface (better than 0.2 µm polish) is important for
- X-ray detection: Filters are important in PIXE
electron-probe measurements, whereas for proton mea-
measurements using and EDS. The basic function is to
surements this is not as critical. The larger excitation
protect the Si(Li) detector from the scattered beam, but
depth, however, implies that proton-microprobe analy-
the more important aspect is to tailor the measurement
sis should be used with caution when grains less than 30
for optimum sensitivity for desired elements by attenua-
µm size are analyzed, due to possible excitation of
tion the count rate of major elements, and to reduce
underlying and overlapping phases. This could be
pileup effects. The latter could be essential in number of
avoided with thin transparent specimens, but for opaque
cases, e.g. Rb or Sr masked by pileup from Fe. Special
minerals it may not be practical. Spatial resolution in
filters can be used exploiting X-ray absorption edges,
the micron or submicron regime is thus not the most
but secondary fluorescence of the filters themselves can
important criterion when ideal samples are in the 30-50
mask elements of interest. Ability to change filters
µm minimum size, unless special features such as zona-
quickly is an important feature from a practical view-
tion in minerals require it. On the other hand, the large
point.
excitation depth enables analysis of special samples,
The use of filters, however, also reduces the ability to
such as fluid inclusions [15].
measure the major element composition of most
- Minimum detection limit (MDL): The ultimate
minerals. The minimum filter for 3 MeV protons ab-
minimum detection limit is determined mainly by the
sorbs most X-rays from elements below Na. For heavier
presence of continuum background, primarily due to
beams a thinner absorber can be used, and conse-
bremsstrahlung. In the case of the electron probe, this
quently lighter elements can be detected. However, this
limits the detection of trace elements to levels > 500
may still require supplementing the data with that ob-
ppm with standard energy-dispersive spectrometers
tained the electron probe. This may also be required for
(EDS, i.e. Si(Li)); 50-100 ppm is achievable with great
other reasons, e.g. when beam integration is a problem
care using wavelength-dispersive spectrometers (WDS).
due to charge buildup on insulating targets. A large
For protons, MDL in the 0.1-50 ppm range is achieva-
dynamic range of beam current can cause problems in
ble even with energy-dispersive spectrometers (EDS), by
secondary methods of beam measurement.
virtue of the lower level of background. However, this is
- Electron detection: Backscattered electrons in elec-
achieved only at a certain required integrated beam
tron-probe analysis are copious and provide good con-
charge. For example, to achieve 1 ppm MDL of transi-
trast for heavy elements in light matrices, e.g. grain
tion elements in a silicate matrix, 10 µC of 3 MeV
noble metals on olivine grain boundaries. Most scan-
proton beam is required when the Si(Li) detector has a
ning electron probes are operated using this radiation.
solid angle of 50 msr. With a 10 nA beam this requires
To obtain comparable data by scanning PIXE is not as
approximately 20 min. The measurement time would be
advantageous: the secondary electrons are not as copi-
unviable if a beam current of less than 1 nA is available.
ous and do not give sufficient discrimination, and the
- Beam intensities and resolution: Electron sources
X-ray yield is usually very low, and viable beam current
are much brighter than proton sources, e.g. 10⁵
at comparable resolution is not possible.
A/(cm² sr) compared to only about 20 for a duoplas-
- Other radiations: The additional advantage of
matron source. Hence viable electron beam currents
using proton or other ion beams is the possibility of
(50-100 nA) are readily available at a resolution of
exploiting the scattered beam and gamma-radiations. In
around 1 µm, with aberration effects already taken into
the case of proton and alpha beams, Rutherford back-
account. Even in the absence of aberrations, to achieve
scattering (RBS) or resonant scattering can be used to
comparable resolution for protons, the available beam
determine light elements e.g. C, O, N. Gamma rays
intensity would be considerably lower which may ren-
from resonant and nonresonant reactions induced by
der quantitative analysis unfeasible [16]. The best beam
protons can be used to detect an assortment of light
VIII. GEOLOGY/MINERALOGY
286
S.H. Sie et al. / The proton microprobe in mineral analysis
nuclei, e.g. fluorine. Development in this area is pro-
for U and Th, which are the main traces, the MDL
gressing rapidly [18], but will not be discussed further in
value is ~ 20 ppm.
this paper.
Partitioning of these marker elements between the
Conditions considered optimum for quantitative mi-
magma and the crystallizing phases is sensitive to pres-
cro-PIXE of mineralogical samples can thus be sum-
sure (P), temperature (T) and initial composition of
marized as follows:
the parent magma, and also may be dependent on the
- For monomineralic-grain analysis, the size is prefer-
valence of the elements being partitioned. Geochemical
ably greater than 30-60 µm to avoid possible over-
modelling of the evolution of magmas requires accurate
lapping grains.
knowledge of these partition coefficients. Different
- For viable measurement time, and combined with the
phases may be involved in different magmas. For exam-
above, it follows that proton beam resolution of the
ple, important phases at high pressure for basaltic liquid
order 5-20 µm is necessary and sufficient.
are garnets and clinopyroxene and an important phase
- To fully exploit PIXE's advantage as a trace-element
for intermediate or granitic magmas is amphibole. The
probe, the scanning ability must be used judiciously.
P,T-dependence of the partition coefficients can be
Line scan, or selective probing would be more effec-
determined in natural systems, or in experimentally
tive for quantitative analysis.
synthesized minerals produced under laboratory condi-
- From the practical point of view, the ability to view
tions simulating the mantle conditions. Elements occur-
the specimen in the reflecting geometry is important,
ring as major or minor elements can be measured read-
if only to enable convenient positioning of the sam-
ily both in natural and synthezised samples with elec-
ple tuning of the beam spot.
tron probes. However, elements which are not readily
incorporated in the lattice, i.e. incompatible elements,
occur only at very low levels, usually below the detec-
3. Applications
tion limits of electron microprobes. Increasing the con-
centration to measurable levels in synthetic samples
may invalidate the results due to breakdown of Henry's
At HIAF, quantitative trace-element distribution by
law. With the proton microprobe, despite the limita-
micro-PIXE has been applied to the study of indicator
tions discussed above, detection limits for most of the
minerals used in diamond exploration, diamonds, di-
amond inclusions, mantle-derived xenoliths and mega-
important marker elements are still in the 1-10 ppm
regime, making systematic study of partition coeffi-
crysts, sulfide minerals, sapphires, native Au and fluid
cients under conditions close to most natural systems
inclusions. The samples can be polished thin or thick
possible. An example of such study of partition coeffi-
sections of the rock or ore, or concentrate prepared as
cients of Nb and Ta, thought previously to be geochem-
grain mounts as for electron-microprobe analysis.
ically coherent, between garnet, clinopyroxene and
basaltic liquid, showed large fractionation effects which
3.1. Igneous mineralogy and petrology
must be taken into account in geochemical modelling
[19].
In retrospect, analyses of samples of igneous
Changes in the melt composition due to fractional
minerals, except zircons are the easiest. For most
crystallization or magma mixing result in a spectacular
minerals, Fe is the heaviest element in the matrix and
distribution of trace elements in certain phases of natu-
thus many geochemically important marker elements
ral systems, e.g. kimberlites and lamproites, the main
such as Ni, Zn, Ga, Ge, Rb, Sr, Zr, Y, Nb and Ta can
source for diamonds. Igneous minerals contained in
be detected with good MDL. The rare-earth elements
these rocks, sometimes as megacrysts, preserve the sig-
(REE) are equally important, but their detection, how-
nature of their evolution in the upper mantle, prior to
ever, is at present still problematic. The L lines are
emplacement by eruption. The minerals are usually
totally masked by either the FeK lines or the escape
dispersed by weathering process and erosion. Of these,
peaks, and for the light REE the peak-to-background is
ilmenites, garnets and chromites are the most com-
degraded by the tail of the Fe line. The K lines can be
monly used in diamond exploration and the characteri-
observed free of interference, but the detection ef-
zation of the source rocks [20]. For example, fig. 1
ficiency for Si(Li) detectors drops dramatically above
shows the Zr content of ilmenites from one kimberlite
~ 30 keV. In apatite, using the K lines, MDL values of
pipe in South Africa. These show the effects of frac-
- 40 ppm for La, Ce, Pr and Nd can be obtained. With
tional crystallization, with dramatic changes in con-
a Ge detector, the K lines can be detected more effi-
centration marking the onset of precipitation of other
ciently, but a continuum background due to Compton-
phases, e.g. zircons. Similar results were obtained for Ni
scattered gamma rays also results in a relatively poor
in chromites, where sudden changes can be attributed to
peak-to-background ratio. For zircons, the tail of the Zr
the precipitation of olivine. Fig. 2 shows the result for
K lines degrades the MDL of all elements below it, and
ilmenites from a number of pipes. Dependence on the
S.H. Sie et al. / The proton microprobe in mineral analysis
287
4000
Nb
Nb
3000
2000
ppm
Zircon
precipitation
starts
1000
Olivine
precipitation
stops
Zr
Ni
200
400
600
800
0
500
1000
ppm
ppm
Fig. 1. Correlation diagrams of trace elements in ilmenites from one kimberlite pipe, showing the effect of fractional crystallizations.
Precipitation of Zr depletes Zr in the melt, and similarly olivine depletes Ni.
initial magma composition is reflected in the grouping
The effect of temperature is equally spectacular in
of the concentrations levels, whereas the trend in the
the case of Ni in pyrope garnets coexisting with olivine
individual grouping is governed by the evolution of the
[21]. Partition between the two phases, and the roughly
magma. Such grouping provides the discriminants to
constant Ni content of mantle olivines at around 3000
identify multiple sources and/or different types of rocks
ppm, results in a single mineral geothermometer. Sup-
in diamond-exploration applications.
plemented with the appropriate geotherm, the ther-
10
X
X
1500
Sekameng
8
Lemphane
Kamfersdam
Ni (ppm)
&
Liqhobong
1000
Kao
0880°C
Klipfontein
Mg (%)
6
X
Koffeefontein
DD
i
500
B
4
Basalts
Basalts
80
0
2
500
1000
1500
2000
2500
3000
500
1000
1500
2000
2500
Nb (ppm)
Nb (ppm)
Fig. 2. Result of analysis of ilmenites from a number of pipes showing grouping of the trace-element distribution, which can be used
to identify multiple sources. The trend observed in each group reflects the fractional crystallization effect. The grouping also can be
used to distinguish source rocks; those from basalts are clearly well separated from those from kimberlites.
VIII. GEOLOGY/MINERALOGY
288
S.H. Sie et al. / The proton microprobe in mineral analysis
mometer can be used to assess the prospectivity of a
Arsenopyrite, pyrite and pyrrhotite are usually the
potential diamond source.
phase carrying Au either as submicroscopic particles or
The effect of pressure and temperature, and associ-
in complete solid solution. Ore containing Au in such
ated processes of deformation and metasomatic events
phases is known as refractory ore, and requires roasting
are also reflected as compositional zoning in individual
prior to the usual processing. Detailed distribution is
mineral grains. With the proton microprobe the effect
therefore required to determine whether the ore is worth
on incompatible elements can be studied in detail. In-
processing. In pyrite and pyrrhotite, MDL of 5 ppm can
filtration of melts or other fluids into a rock will change
be obtained, while in arsenopyrite the tail of As de-
the bulk composition of the system, while changes in
grades the MDL to ~ 40 ppm. While the absorber can
temperature will change the partitioning of elements
play an important role in enhancing MDL by absorbing
between minerals. Elements with appropriate diffusion
the major lines, this does not help the Au in the
rates will record these changes as zoning patterns, and it
arsenopyrite case.
is possible to derive information on the nature of the
Sulfide phases can also be carriers of the other noble
processes and the time scales involved [22].
metals, the platinum group elements (PGE). These ele-
ments occur at very low crustal abundances, but are
3.2. Sulfide mineralogy
obtained economically from placers, komatiite-hosted
Ni-Cu ores and layered mafic/ultramafic intrusions.
In sulfide minerals, the trace elements may be of
Cabri et al. [9] have studied the distribution of PGE in
interest both geochemically (Se, Cd, In, Ni, Sb, Sn, Hg)
the Sudbury Ni-Cu deposit and the Stillwater layered
and economically (Au, Ag). In arsenopyrite Sb can
complex. Another example of a layered intrusion is the
substitute for As, and both As and Sb can affect the
Merensky Reef in the Bushveld Complex intrusion of
precipitation of Au. In galena, the presence of Sb and
South Africa, one of the main sources of PGE. In this
Bi increases the solubility of Ag through coupled sub-
deposit, the PGEs occur mainly as platinum group
stitution, with AgBi or AgSb substituting for 2Pb [23].
minerals (PGM) in sulfide-bearing gabbros associated
The ratio of Ag to Sb and Bi can be used to deduce the
with the chromitite layers. A significant fraction of the
temperature of equilibration, reflecting metamorphic or
PGE is contained in the sulfides and a study of the
depositional temperature. Likewise the Se/S ratio is
detailed distribution in them using the proton micro-
expected to increase with temperature of formation,
probe revealed pyrrhotite and pentlandite as significant
with high Se associated with a hydrothermal-magmatic
carriers. MDL values of 1.5-2 ppm are obtained for Pd,
system, and a sedimentary system showing lower Se
Rh and Ru, and 5-7 ppm for Pt, Os and Ir in these
content. Although this correlation does not always hold,
minerals [28]. In addition to the direct application of
with the proton microprobe it is now possible to study
micro-PIXE, a supplementary method combining it with
the behaviour of Se and the other trace elements under
a preconcentration step by fire assay can be used to
different depositional conditions systematically. The
determine the bulk concentration of Pt and Pd. A
temperature dependence is normally obtained from iso-
detection sensitivity of 6 ppb, comparable to crustal
topic studies (e.g. ³⁴S), but if it can be obtained nonde-
abundances, can be obtained by analyzing the silver
structively from trace element analysis it would be
prills from the Pb-Ag fire assay [29,12].
useful as supplementary data, e.g. in the applications of
the sphalerite geobarometer [24]. In general, the prob-
3.3. Trace elements in gold
lem of solid solution of e.g. Fe in sphalerite, or Zn in
chalcopyrite can be delineated through systematic stud-
Silver is nearly always present in native Au, and the
ies of natural and synthetic samples [9,25]. Detection
variation of its content can be associated with different
limits with EDS detectors are typically in the range
genetic types and interpreted as the effect of tempera-
5-20 ppm for most of the elements of interest. For
ture of formation and salinity of the ore fluids [30].
galena, MDL values are generally higher, and Hg and
However, the Ag/Au content can be altered during
Bi can only be detected with a MDL value at around
fluvial transport which can obscure the genetic informa-
200 ppm due to severe interference problems.
tion. The presence of other trace elements, e.g. Fe, Cu,
From the point of view of mineral processing, the
Zn, Pb and Hg was demonstrated by Warren and
distribution of Ag among coexisting sulfides is of eco-
Thompson [31] by spectrographic techniques. They con-
nomic interest [12,26]. The detailed distribution of Ag
cluded that observed trace-element variations are con-
in sulfide concentrates can be used to improve benefici-
trolled mainly by the characteristics of the metallogenic
ation efficiency, by recovering from minor Ag bearing
provinces rather than the type of deposit, raising the
phases which otherwise would be lost to the tailings. In
possibility of using trace elements as a more sensitive
these phases, except for those containing high level of
discriminant. This would have implications in explora-
Sb, e.g. tetrahedrite or stibnite, Ag readily can be de-
tion where study of alluvial gold grains can be used to
termined to 1-10 ppm.
establish their provenance through genetic associations
S.H. Sie et al. / The proton microprobe in mineral analysis
289
and to identify multiple sources. The early spectro-
Examples of the results obtained for Cu and Hg are
graphic studies were beset by problems of contamina-
shown in the correlation diagrams in fig. 4. The data
tion due e.g. to mineral inclusions and multiple sources
obtained so far showed some evidence of characteristic
could not possibly be identified because a large number
differences between different deposit types and styles of
of grains were required for each analysis. Later elec-
mineralization, between deposits of the same type and
tron-probe studies avoided these problems, enabling
between different mineralogical associations within a
one to distinguish traces in solid solution, but most of
particular deposit. High Hg content was observed for
these are below detection limits [32].
mafic/ultramafic associations. Alluvial samples show
In a preliminary study of trace element in gold, a
decreasing Ag content with distance from the source.
suite of samples from a number of sources in Tasmania
With more analysis, more definite characteristics may
have been analyzed using micro-PIXE at HIAF [33].
emerge.
Fig. 3 shows a typical spectrum obtained from the gold
grains, showing the dominant Au and Ag peaks. This
example illustrates the limits of the EDS system: the
4. Conclusion
Au lines masked most of the L lines for adjacent
elements. Pb and Bi can only be observed reliably
The examples discussed here and elsewhere in the
through their L gamma lines. The PGE L lines are also
Proceedings demonstrate that the application of the
unresolved, and this problem is further compounded by
proton microprobe in mineralogy is truly revolutionary
'tails" of the AuL photopeaks at the low-energy side
in the sense that it provides new or much better-quality
which can be time dependent. Hg, with peaks higher in
data which can provide much tighter constraints on
energy than Au, can be fitted unambiguously, but the
geological interpretations. The applications illustrate the
MDL is still in the 200 ppm regime. The tails of the
exploitation of various aspects of quantitative micro-
AgK lines interfere with the detection of Pd. More
PIXE: the sensitivity, rapidity of analysis, large effec-
significantly, Pd is also interfered with by the pileup
tive depth of analysis (fluid inclusions), and wherever
peaks from Au, as can be seen in fig. 3. Despite these
necessary, the spatial resolution (zoning in minerals).
limitations, the preliminary results are encouraging. In
The tradeoff between spatial resolution and beam inten-
these samples the Au ranges from 69 to 98 wt.%, and Ag
sity is one area where development in lens and ion-
from 1.4 to 30 wt.%. Elements observed include Hg, Bi
source technology can make significant improvements.
and Cu at about 0.1% concentrations, and other base
Within the present constraints, further improvements in
metals (Fe, Pb and Zn) at < 0.1%. Traces of Pd, As and
detector technologies, e.g. large-area and/or multiple-
Mn were also measured. The Mn numbers are unreli-
detector systems, can improve efficiency. This and other
able because of the high absorption by the filter used.
features such as a quick sample changer, a good
Au
10
5
Sample: Jane River #4
3 MeV protons
Hg
100 um Al filter
10
4
counts per channel
3
Cu
10
Fe
Ag
10
2
Pb
pile-up
Pd
peaks
10
1
10
20
X-ray energy (keV)
Fig. 3. A typical spectrum obtained from the gold grain, showing the dominant Au and Ag peaks, and the fitted spectrum with the
pileup peaks indicated.
VIII. GEOLOGY/MINERALOGY
290
S.H. Sie et al. / The proton microprobe in mineral analysis
Cu
As more geoscientists discover the instrument, the scope
and mode of applications will also grow, and ultimately
the instrument should be regarded as a standard, vital
4000
and versatile fool for advances in the geosciences. How-
ever, one has to be continually aware of parallel devel-
opment of competing methods such as the ion micro-
concentration (ppm)
probe, the synchroton radiation microprobe, and also
the electron microprobe which is being improved stead-
ily. It is equally important to recognize the appropriate
2000
niches for the various techniques in order to capitalize
on their respective unique features.
Au
References
Hg
[1] H. Blank, R. Nobiling, K. Traxel and A. El Goresy, Lunar
elliot_bay
Sci. 13 (1982) 49.
jane_river
[2] J.P.F. Sellschop, Nucl. Instr. and Meth. 191 (1981) 11.
2.0
lea_river
[3] T.M. Benjamin, C.J. Duffy and P.S.Z. Rogers, Nucl. Instr.
19m creek
and Meth. B30 (1988) 454.
warrego
[4] S.H. Sie, Nucl. Instr. and Meth. B10/11 (1985) 664.
concentration (wt. 8)
0 rosebery
[5] S.H. Sie and C.G. Ryan, Nucl. Instr. and Meth. B15
V que_river
(1986) 664.
[6] C.G. Ryan, D.R. Cousens, S.H. Sie, W.L. Griffin, G.F.
1.0 %
Suter and E. Clayton, Nucl. Instr. and Meth. B47 (1990)
55.
[7] G.J.F. Legge, Nucl. Instr. and Meth. B3 (1984) 561.
[8] F. Watt, G.W. Grime, G.D. Blower and J. Takacs, IEEE
Trans. Nucl. Sci. NS-28 (1981) 1413.
[9] L.J. Cabri, H. Blank, A. El Goresy, J.H.G. Laflamme, R.
Au
Nobiling, M.B. Sizgoric and K. Traxel, Can. Mineralogist
22 (1984) 521.
60 %
70 %
80 %
90 %
100 %
[10] J.L. Campbell, W. Maenhaut, E. Bombelka, E. Clayton,
concentration (wt. 8)
K. Malmqvist, J.A. Maxwell, J. Pallon and J. Vanderhaute,
Fig. 4. Correlation diagram for Cu (in ppm) and Hg(%) vs
Nucl. Instr. and Meth. B14 (1986) 204.
Au(%) for the samples studied. With more data, discrimination
[11] L.J. Cabri, Nucl. Instr. and Meth. B30 (1988) 459.
between different types of sources will become more evident.
[12] S.H. Sie, C.G. Ryan, D.R. Cousens and W.L. Griffin,
Nucl. Instr. and Meth. B40/41 (1989) 690.
[13] S.H. Sie, C.G. Ryan, D.R. Cousens and W.L. Griffin,
sample-viewing system, and last but not least an effi-
Proc. 10th IBA Conf., Kingston, Canada 1989, Nucl.
Instr. and Meth. B45 (1990) 604.
cient data handling system would reduce unit cost of
[14] L.J. Cabri, S.L. Chryssoulis and J.L. Campbell, to be
analysis, which is one of the crucial factors for
published.
widespread acceptance by the minerals industry.
[15] C.G. Ryan, D.R. Cousens, C.A. Heinrich, W.L. Griffin,
The wavelength-dispersive spectrometer (WDS)
S.H. Sie and T.P. Mernagh, these Proceedings (2nd Int.
promises resolution of some currently intractable prob-
Conf. on Nuclear Microprobe Technology and Applica-
lems. This can be due either to interference problems
tions, Melbourne, Australia, 1990) Nucl. Instr. and Meth.
(detection of REE or of Au/As/Pb/Bi/Hg and photo-
B54 (1991) 292.
peak tailing problems in Pd/Ag) or to generally poorer
[16] S.H. Sie, C.G. Ryan, D.R. Cousens and G.F. Suter, Proc.
peak-to-background in analysis of high-Z minerals such
10th IBA Conf., Kingston, Canada 1989, Nucl. Instr. and
as zircons and uraninite. The last limitation also holds
Meth. B45 (1990) 543.
[17] F.W. Martin and R. Goloskie, Appl. Phys. Lett. 40 (1982)
true for the detection of trace elements lighter than Fe.
191.
However, the use of a WDS may be hampered by
[18] C. Boni, E. Caruso, E. Cereda, G.M. Braga Marcazzan
insufficient beam currents, when high spatial resolution
and P. Redaelli, Nucl. Instr. and Meth. B40/41 (1989)
is also desired.
620.
The present review covers one perspective of the use
[19] T.H. Green, S.H. Sie, C.G. Ryan and D.R. Cousens,
of the proton microprobe in mineralogical applications.
Chemical Geology 74 (1989) 201.
S.H. Sie et al. / The proton microprobe in mineral analysis
291
[20] W.L. Griffin, C.G. Ryan, D.R. Cousens, S.H. Sie and
Int. Conf. on Gold, Perth 1988 (Randol International,
G.F. Suter, Proc. 5th Conf. on PIXE and its Analytical
Golden, Colorado, 1988) p. 134.
Applications, Amsterdam, 1989, Nucl. Instr. and Meth.
[28] D.R. Cousens, W.L. Griffin, C.G. Ryan, S.H. Sie and
B49 (1990) 318.
G.F. Suter, Proc. 5th Aust. Conf. on Nuclear Techniques
[21] W.L. Griffin, D.R. Cousens, C.G. Ryan, S.H. Sie and
of Analysis (AINSE, Lucas Heights, NSW, 1987) p. 184.
G.F. Suter, Contr. Min. Petrol. 103 (1989) 199.
[29] S.H. Sie, C.G. Ryan, G.F. Suter, D.R. Cousens and W.L.
[22] W.L. Griffin, D. Smith, F.R. Boyd, D.R. Cousens, C.G.
Griffin, ibid, p. 181.
Ryan, S.H. Sie and G.F. Suter, Geochim. Cosmochim.
[30] R.W. Boyle, The Geochemistry of Gold and Its Deposits,
Acta 53 (1989) 561.
Geol. Survey of Canada Bull. 280 (1979) 197.
[23] O. Amcoff, Mineralium Deposita 19 (1984) 63.
[31] H.V. Warren and R.M. Thompson, Econ. Geol. 39 (1944)
[24] S.D. Scott, Economic Geol. 68 (1973) 466.
457.
[25] D.C. Harris, L.J. Cabri and R. Nobiling, Can. Mineralo-
[32] M. Guindon, M.Sc. Thesis, Queen's University, Canada,
gist 22 (1984) 493.
1982.
[26] L.J. Cabri, J.L. Campbell, J.H.G. Laflamme, R.G. Leigh,
[33] S.H. Sie, S.J.M. Garrett, R.R. Large, D.R. Cousens, W.L.
J.A. Maxwell and J.D. Scott, Can. Mineralogist 23 (1985)
Griffin and C.G. Ryan, Proc. 6th Aust. Conf. on Nuclear
133.
Techniques of Analysis (AINSE, Lucas Heights, NSW,
[27] S.H. Sie, C.G. Ryan, D.R. Cousens and G.F. Suter, Proc.
1989) p. 153.
VIII. GEOLOGY/MINERALOGY
294
Nuclear Instruments and Methods in Physics Research B52 (1990) 294-297
North-Holland
An AMS facility for minerals exploration research
S.H. Sie, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, PO Box 136, N. Ryde 2113, Sydney, Australia
An AMS (accelerator mass spectrometry) system based on a Tandetron has been constructed at the CSIRO HIAF laboratory at
North Ryde, and is currently undergoing tests. The system is designed to enable cosmogenic isotope based chronology, and
eventually will be developed to enable ultratrace measurements in mineralogical samples.
1. Introduction
2. The AMS system
HIAF is an analytical laboratory based on a model
The HIAF-AMS project will proceed in two stages,
1430 Tandetron accelerator, commissioned in late 1983
with the first resulting in standard AMS capability, viz.
[1]. It is dedicated to developing IBA (ion beam analy-
¹⁰Be, ¹⁴C dating on "bulk" samples. ³⁶Cl detection will
sis) and AMS applications in the geosciences in support
also be attempted. The second stage involves the devel-
of the Australian minerals industry. An essential re-
opment of the microprobing Cs sputter source. The
quirement for mineralogical and petrological applica-
AMS system incorporates the existing beam transport
tions of IBA is the development of the proton micro-
system at HIAF, with the addition of a beamline for the
probe, completed in 1985, to enable in situ microanaly-
detection system, and a separate injector.
sis of monomineralic grains, the fundamental con-
A schematic of the HIAF beam transport system,
stituent of geological samples [2,3]. With this instru-
including the AMS system, is shown in fig. 1. The AMS
ment, significant progress has been achieved in the area
injector system is based on a double focusing, 90°
of trace element geochemistry, particularly in igneous
analyzing magnet with a radius of 30 cm and beam
mineralogy leading to new methods of exploration.
product (ME/q² in amu MeV/e² units) of 7, with a
The development of AMS was carried out mainly in
maximum, aberration-limited momentum resolution of
recognition of its importance in geochronology, based
6500 for an object diameter of 0.25 mm. For normal
on cosmogenic light radioisotopes. The research interest
operation using typical ion sources, a more moderate
of the Division lies mainly in the applications of ¹⁰Be
resolution is expected for good transmission efficiency
and ³⁶Cl dating to problems relevant to exploration and
through the accelerator. The magnet box is electrically
mining. The scope of published work on applications of
insulated from the rest of the beamline to permit energy
10 Be [4], ranging from soil transport and erosion studies,
modulation of the incident beam ("bouncing") to main-
rock exposure ages on to petroleum dating offers excit-
tain the same magnetic rigidity. A 90° electrostatic
ing prospects in research of ore and petroleum genesis
spherical analyzer with 75 cm radius preceding the
as aids in exploration. Similarly, the information from
magnet will be added in the future, to improve the
³⁶Cl as a tracer and chronometer of groundwater can be
rejection ratio of adjacent isotopes.
an important supplement in hydrogeochemical methods
The beam from a General Ionex model 834 Hiconex
of exploration, and water management in arid areas. In
sputter source is focused by an einzel lens to form a
addition to the direct requirements in the minerals
waist at the magnet's object slits. The beam is further
industry, HIAF is accessible by other areas of research,
transported to the original low-energy cup through the
and thus the AMS facility will also be available for ¹⁴C
"old", demagnetized injector, by means of another einzel
dating.
lens. Distances are chosen to match the emittance of the
Of more direct interest to minerals research is the
AMS injector system to the acceptance of the original
AMS capability to detect very low levels (ppb) of trace
system. The "cone" of the Hiconex source, which holds
elements. So far the method has been applied using a
the sample to be sputtered, is modified to permit focus-
submillimeter sputtering beam, which is not adequate
ing of the Cs beam onto the downstream side, and into
for most measurements requiring monomineralic in situ
a smaller area. The sample is loaded into a "well" in the
microanalysis [5]. A microprobing sputter source must
cone (1 mm diameter and 1 mm deep). This modifica-
be developed for successful applications of AMS as a
tion reduces the amount of sample required and im-
trace analyzer.
proves the source emittance.
0168-583X/90/$03.50 © 1990 Elsevier Science Publishers B.V. (North-Holland)
S.H. Sie et al. / An AMS facility for minerals exploration research
295
Einzel
Injector
Electrostatic
LE'
Lens
Magnet
LE
Stripper
Doublet
HE
Tube Lens
AMS
Canal
Injector
Analyzing
Magnet
I
Magnet
Matching
Lens
SOURCE
Einzel Lens
MAG
TANDETRON
Einzel Lens
Triplet
Duoplasmatron Source
Quad
Switching
Magnet
AMS lon Source
HIAF:
BEAM TRANSPORT SYSTEM
LINE
Doublet Quad
Electrostatic
V
Analyzer
BEAM
lon Sources
LINE II
(NRA)
Faraday Cups
BEAM LINE I
Slits
Microprobe
(RBS)
Steerers
Quad
X
Target Chambers
Gas Counter
BEAM LINE IV
(AMS)
BEAM LINE III
Microprobe
(PIXE,NRA,RBS)
Fig. 1. A schematic of the HIAF beam transport system, showing the AMS system comprising the AMS injector and the AMS beam
line. The electrostatic analyzer bends the beam downwards by 12° into the gas counter.
The beam passes through the usual two stages of
counter is a conventional counter with a Frisch grid,
acceleration with gas stripping at the terminal. There is
operated with isobutane at pressures in the 10-40 mbar
currently no terminal pumping, which some believe to
range. The anode is segmented into three parts, each 5
be critical for reducing the effect of fractionation
cm long. The gap between the cathode plate and the
through the accelerator, but there is provision for its
grid is 25 mm, bisected by the counter window axis.
installation. After the acceleration the beam is analyzed
Initial tests were carried out with a 6 mm diameter
by the 90° analyzing magnet (beam product = 16
window made out of mutiple layers of thin films of
amu MeV/e²). The more abundant isotopes are mea-
VYNS, capable of withstanding up to 200 mbar pres-
sured in the Faraday cup at the image point of this
sure difference. For ¹²C beam, this was eventually en-
magnet. A multi-Faraday cup system with four indepen-
larged to 10 mm diameter using a 2.5 µm mylar film, to
dently adjustable cups has been designed and will be
achieve 100% transmission efficiency to the detector.
implemented as part of the second stage development.
Alignment of the counter chamber and adjustment
This will allow detection of the abundant isotopes
of focus were carried out using a ¹²C beam as a pilot
without the need to alter the analyzing magnet setting.
beam monitored using strongly fluorescing willemite
In the present system, the analyzing magnet has to be
(Zn₂SiO₄) screens at selected points, including that in
adjusted for measurements of each isotope. To facilitate
front of the window.
such switching, a computer controlled beam transport is
being implemented, which will permit automation of the
operation. The present magnet is inadequate for detec-
3. Test and progress
tion of heavy isotopes (A > 60) at moderate terminal
voltages (~ 1 MV). For the second stage development,
3.1. The source
where detection of elements up to U is anticipated, a
new magnet with a much higher beam product will be
Tests were carried out on the modified Hiconex
acquired.
cones using natural graphite and graphitized carbon,
The rare isotope is further focused by the magnetic
prepared by the usual method of CO2 reduction (sup-
triplet into the detector beam line through a 22.5°
plied by F. Leaney, CSIRO Division of Water Re-
deflection using the switching magnet. A 12° electro-
sources, Adelaide and by R. Gillespie, ANU, Canberra).
static spherical analyzer with 4 m radius and 11 mm gap
With the source mounted on the original injector,
feeds the beam into a gas proportional counter. The
analyzed beams of 12 C between 1 and 3 µA have been
II. NEW & FUTURE FACILITIES
296
S.H. Sie et al. / An AMS facility for minerals exploration research
obtained, to be compared with 6 µA typically ob-
the entrance and exit. The increased efficiency with
tained from an unmodified cone. The lower intensities
terminal voltage may reflect better matching of the
in the reflected cone are to be expected considering that
injected beam emittance with the accelerator accep-
they are sputtered from less material. Another factor is
tance, as well as stripping efficiency. The observed
the possibility of slight misalignment of the Cs gun in
efficiency compares favourably with that obtained by
the source. It was found that when the well in the
similar machines, e.g. 20% reported by the Arizona
modified cone is enlarged into a slot (3 mm by 1 mm),
group [7]. Improvements are expected with further ad-
an improved yield is obtained when the slot is in the
justments in the injector alignment.
radial direction, implying that the reflected Cs beam is
slightly off axis. The source output however was found
3.2. The dectector
to be stable to better than 1% over periods as long as an
hour.
Test with 6 and 8 MeV beams of ¹²C, ¹⁶O (q=3+) =
Initial tests to produce BeO⁻ from oxide powder
and ²⁸Si (q=4+) = have been carried out and resolu-
gave poor yield 100 nA). The sample was prepared
tions of 120, 150 and 220 keV were obtained for the dE
from natural BeO mixed with fairly coarese Cu powder
anode signal. The results are consistent with a 100 keV
(100 mesh). Further tests will be conducted with finer
electronic resolution, with the remainder accountable in
powder to improve the heat and electrical conductivity
terms of the loss distribution width. The straggling
of the mixture.
effect introduced by the change from VYNS to the
In the new injector, the source yield (past the injec-
thicker Mylar window contributes only an additional 5
tor magnet) is considerably lower due most likely to
keV to the total resolution. The obtained resolution is
alignment problems of the magnet. This problem is
more than adequate to separate the C isotopes. Fig. 2
currently being rectified. Progress within the past few
shows the spectra from the third anode at 20 mbar gas
months has been hampered by two successive failures of
pressure, obtained with the source mounted in the old
the Cs gun; a new gun has been installed recently and
injector. The ¹⁴C/¹²C peak area ratio is about 25 for
the test is continuing.
the modern sample (ANU sucrose). The ¹³C intensity is
The ¹²C beam transmission through the accelerator
high, reflecting the poor resolution of the old injector
was tested at 1.8 and 2.33 MV on the terminal. Analysis
magnet. This is expected to be reduced with the new
of the 3+ state indicates a particle efficiency of 10%
injector. For 10 Be measurements the energy resolution
and 19% respectively, to be compared with a maximum
of the counter is also more than adequate, but for ³⁶Cl it
theoretical limit of ~ 50% [6]. Most of the losses are
is inadequate to discriminate against ³⁶S, especially due
due to the narrow stripper canal, and misalignment of
to the large energy straggling effect in the counter.
10
4
(1) 30X modern
(1)
(2) ANU sucrose
10
3
E(C14) = 8.0 MeV
Counts per channel
C14
C13
C12
10
2
10
(2)
200
400
600
Channels
Fig. 2. Spectra from the third anode segment in the gas proportional counter obtained with the source mounted in the old injector.
The samples were 30 modern sample and ANU sucrose. The ¹⁴C, ¹³C and ¹²C are well resolved. The poor resolution of this injector
is reflected in the relatively high level of ¹³C.
S.H. Sie et al. / An AMS facility for minerals exploration research
297
4. Summary
References
The first stage of the CSIRO-AMS facility is virtu-
[1] S.H. Sie, Nucl. Instr. and Meth. B10/11 (1985) 664.
ally completed and is undergoing tests. It enables ¹⁰Be
[2] S.H. Sie and C.G. Ryan, Nucl. Instr. and Meth. B15 (1986)
and ¹⁴C measurements. The main problem encountered
664.
at present is the poor yield out of the source, which is
[3] S.H. Sie, C.G. Ryan, D.R. Cousens and W.L. Griffin, Nucl.
due to possible misalignment of the gun in the source
Instr. and Meth. B40/41 (1989) 690; B45 (1990) 604.
itself, as well as misalignment of the beam transport
[4] L. Brown, Annual Rev. Earth. Plan. Sci. 12 (1984) 39; Phil.
Trans. R. Soc. London A323 (1987) 57.
system.
[5] J.C. Rucklidge et al., Nucl. Instr. and Meth. 191 (1981) 1;
The second stage development will be directed to-
B45 (1990) 565.
wards heavy isotope detection and a microprobing
[6] J.B. Marion and F.C. Young, Nuclear Reaction Analysis
sputter ion source for detection of ultratraces in minera-
(North-Holland, Amsterdam, 1968).
logical research.
[7] D.J. Donahue et al., Radiocarbon 25 (1983) 719.
II. NEW & FUTURE FACILITIES
294
Nuclear Instruments and Methods in Physics Research B52 (1990) 294-297
North-Holland
An AMS facility for minerals exploration research
S.H. Sie, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility, CSIRO Division of Exploration Geoscience, PO Box 136, N. Ryde 2113, Sydney, Australia
An AMS (accelerator mass spectrometry) system based on a Tandetron has been constructed at the CSIRO HIAF laboratory at
North Ryde, and is currently undergoing tests. The system is designed to enable cosmogenic isotope based chronology, and
eventually will be developed to enable ultratrace measurements in mineralogical samples.
1. Introduction
2. The AMS system
HIAF is an analytical laboratory based on a model
The HIAF-AMS project will proceed in two stages,
1430 Tandetron accelerator, commissioned in late 1983
with the first resulting in standard AMS capability, viz.
[1]. It is dedicated to developing IBA (ion beam analy-
10 Be, ¹⁴C dating on "bulk" samples. ³⁶Cl detection will
sis) and AMS applications in the geosciences in support
also be attempted. The second stage involves the devel-
of the Australian minerals industry. An essential re-
opment of the microprobing Cs sputter source. The
quirement for mineralogical and petrological applica-
AMS system incorporates the existing beam transport
tions of IBA is the development of the proton micro-
system at HIAF, with the addition of a beamline for the
probe, completed in 1985, to enable in situ microanaly-
detection system, and a separate injector.
sis of monomineralic grains, the fundamental con-
A schematic of the HIAF beam transport system,
stituent of geological samples [2,3]. With this instru-
including the AMS system, is shown in fig. 1. The AMS
ment, significant progress has been achieved in the area
injector system is based on a double focusing, 90°
of trace element geochemistry, particularly in igneous
analyzing magnet with a radius of 30 cm and beam
mineralogy leading to new methods of exploration.
product (ME/q² in amu MeV/e² units) of 7, with a
The development of AMS was carried out mainly in
maximum, aberration-limited momentum resolution of
recognition of its importance in geochronology, based
6500 for an object diameter of 0.25 mm. For normal
on cosmogenic light radioisotopes. The research interest
operation using typical ion sources, a more moderate
of the Division lies mainly in the applications of 10 Be
resolution is expected for good transmission efficiency
and ³⁶Cl dating to problems relevant to exploration and
through the accelerator. The magnet box is electrically
mining. The scope of published work on applications of
insulated from the rest of the beamline to permit energy
10 Be [4], ranging from soil transport and erosion studies,
modulation of the incident beam ("bouncing") to main-
rock exposure ages on to petroleum dating offers excit-
tain the same magnetic rigidity. A 90° electrostatic
ing prospects in research of ore and petroleum genesis
spherical analyzer with 75 cm radius preceding the
as aids in exploration. Similarly, the information from
magnet will be added in the future, to improve the
³⁶Cl as a tracer and chronometer of groundwater can be
rejection ratio of adjacent isotopes.
an important supplement in hydrogeochemical methods
The beam from a General Ionex model 834 Hiconex
of exploration, and water management in arid areas. In
sputter source is focused by an einzel lens to form a
addition to the direct requirements in the minerals
waist at the magnet's object slits. The beam is further
industry, HIAF is accessible by other areas of research,
transported to the original low-energy cup through the
and thus the AMS facility will also be available for 14C
"old", demagnetized injector, by means of another einzel
dating.
lens. Distances are chosen to match the emittance of the
Of more direct interest to minerals research is the
AMS injector system to the acceptance of the original
AMS capability to detect very low levels (ppb) of trace
system. The "cone" of the Hiconex source, which holds
elements. So far the method has been applied using a
the sample to be sputtered, is modified to permit focus-
submillimeter sputtering beam, which is not adequate
ing of the Cs beam onto the downstream side, and into
for most measurements requiring monomineralic in situ
a smaller area. The sample is loaded into a "well" in the
microanalysis [5]. A microprobing sputter source must
cone (1 mm diameter and 1 mm deep). This modifica-
be developed for successful applications of AMS as a
tion reduces the amount of sample required and im-
trace analyzer.
proves the source emittance.
0168-583X/90/$03.50 © 1990 - Elsevier Science Publishers B.V. (North-Holland)
S.H. Sie et al. / An AMS facility for minerals exploration research
295
Einzel
Injector
Electrostatic
Magnet
LE
Stripper
Doublet
LE'
Lens
HE
Tube Lens
AMS
Canal
Analyzing
Injector
Magnet
I
Magnet
Matching
Lens
SOURCE
Einzel Lens
MAG
TANDETRON
Einzel Lens
Triplet
Duoplasmatron Source
Quad
Switching
Magnet
AMS Ion Source
HIAF:
BEAM TRANSPORT SYSTEM
LINE
Doublet Quad
Electrostatic
BEAM
V
Analyzer
lon Sources
LINE II
(NRA)
X
Faraday Cups
X
BEAM LINE I
Slits
Microprobe
(RBS)
Steerers
Quad
X
Target Chambers
Gas Counter
X
BEAM LINE IV
(AMS)
BEAM LINE III
Microprobe
(PIXE,NRA,RBS)
Fig. 1. A schematic of the HIAF beam transport system, showing the AMS system comprising the AMS injector and the AMS beam
line. The electrostatic analyzer bends the beam downwards by 12° into the gas counter.
The beam passes through the usual two stages of
counter is a conventional counter with a Frisch grid,
acceleration with gas stripping at the terminal. There is
operated with isobutane at pressures in the 10-40 mbar
currently no terminal pumping, which some believe to
range. The anode is segmented into three parts, each 5
be critical for reducing the effect of fractionation
cm long. The gap between the cathode plate and the
through the accelerator, but there is provision for its
grid is 25 mm, bisected by the counter window axis.
installation. After the acceleration the beam is analyzed
Initial tests were carried out with a 6 mm diameter
by the 90° analyzing magnet (beam product = 16
window made out of mutiple layers of thin films of
amu MeV/e²). The more abundant isotopes are mea-
VYNS, capable of withstanding up to 200 mbar pres-
sured in the Faraday cup at the image point of this
sure difference. For 12 beam, this was eventually en-
magnet. A multi-Faraday cup system with four indepen-
larged to 10 mm diameter using a 2.5 µm mylar film, to
dently adjustable cups has been designed and will be
achieve 100% transmission efficiency to the detector.
implemented as part of the second stage development.
Alignment of the counter chamber and adjustment
This will allow detection of the abundant isotopes
of focus were carried out using a ¹²C beam as a pilot
without the need to alter the analyzing magnet setting.
beam monitored using strongly fluorescing willemite
In the present system, the analyzing magnet has to be
(Zn₂SiO₄) screens at selected points, including that in
adjusted for measurements of each isotope. To facilitate
front of the window.
such switching, a computer controlled beam transport is
being implemented, which will permit automation of the
operation. The present magnet is inadequate for detec-
3. Test and progress
tion of heavy isotopes (A > 60) at moderate terminal
voltages (~ 1 MV). For the second stage development,
3.1. The source
where detection of elements up to U is anticipated, a
new magnet with a much higher beam product will be
Tests were carried out on the modified Hiconex
acquired.
cones using natural graphite and graphitized carbon,
The rare isotope is further focused by the magnetic
prepared by the usual method of CO₂ reduction (sup-
triplet into the detector beam line through a 22.5°
plied by F. Leaney, CSIRO Division of Water Re-
deflection using the switching magnet. A 12° electro-
sources, Adelaide and by R. Gillespie, ANU, Canberra).
static spherical analyzer with 4 m radius and 11 mm gap
With the source mounted on the original injector,
feeds the beam into a gas proportional counter. The
analyzed beams of 12 between 1 and 3 µA have been
II. NEW & FUTURE FACILITIES
296
S.H. Sie et al. / An AMS facility for minerals exploration research
obtained, to be compared with 6 µA typically ob-
the entrance and exit. The increased efficiency with
tained from an unmodified cone. The lower intensities
terminal voltage may reflect better matching of the
in the reflected cone are to be expected considering that
injected beam emittance with the accelerator accep-
they are sputtered from less material. Another factor is
tance, as well as stripping efficiency. The observed
the possibility of slight misalignment of the Cs gun in
efficiency compares favourably with that obtained by
the source. It was found that when the well in the
similar machines, e.g. 20% reported by the Arizona
modified cone is enlarged into a slot (3 mm by 1 mm),
group [7]. Improvements are expected with further ad-
an improved yield is obtained when the slot is in the
justments in the injector alignment.
radial direction, implying that the reflected Cs beam is
slightly off axis. The source output however was found
3.2. The dectector
to be stable to better than 1% over periods as long as an
hour.
Test with 6 and 8 MeV beams of ¹²C, =
Initial tests to produce BeO⁻ from oxide powder
and ²⁸Si (q = ) have been carried out and resolu-
gave poor yield 100 nA). The sample was prepared
tions of 120, 150 and 220 keV were obtained for the dE
from natural BeO mixed with fairly coarese Cu powder
anode signal. The results are consistent with a 100 keV
(100 mesh). Further tests will be conducted with finer
electronic resolution, with the remainder accountable in
powder to improve the heat and electrical conductivity
terms of the loss distribution width. The straggling
of the mixture.
effect introduced by the change from VYNS to the
In the new injector, the source yield (past the injec-
thicker Mylar window contributes only an additional 5
tor magnet) is considerably lower due most likely to
keV to the total resolution. The obtained resolution is
alignment problems of the magnet. This problem is
more than adequate to separate the C isotopes. Fig. 2
currently being rectified. Progress within the past few
shows the spectra from the third anode at 20 mbar gas
months has been hampered by two successive failures of
pressure, obtained with the source mounted in the old
the Cs gun; a new gun has been installed recently and
injector. The ¹⁴C/¹²C peak area ratio is about 25 for
the test is continuing.
the modern sample (ANU sucrose). The ¹³C intensity is
The 12 beam transmission through the accelerator
high, reflecting the poor resolution of the old injector
was tested at 1.8 and 2.33 MV on the terminal. Analysis
magnet. This is expected to be reduced with the new
of the 3+ state indicates a particle efficiency of 10%
injector. For 10 Be measurements the energy resolution
and 19% respectively, to be compared with a maximum
of the counter is also more than adequate, but for ³⁶Cl it
theoretical limit of ~ 50% [6]. Most of the losses are
is inadequate to discriminate against ³⁶, especially due
due to the narrow stripper canal, and misalignment of
to the large energy straggling effect in the counter.
10
4
(1) 30X modern
(1)
(2) ANU sucrose
10
3
E(C14) = 8.0 MeV
Counts per channel
C14
C13
C12
10
2
10
(2)
200
400
600
Channels
Fig. 2. Spectra from the third anode segment in the gas proportional counter obtained with the source mounted in the old injector.
The samples were 30 x modern sample and ANU sucrose. The ¹⁴C, ¹³C and ¹²C are well resolved. The poor resolution of this injector
is reflected in the relatively high level of ¹³c.
S.H. Sie et al. / An AMS facility for minerals exploration research
297
4. Summary
References
The first stage of the CSIRO-AMS facility is virtu-
[1] S.H. Sie, Nucl. Instr. and Meth. B10/11 (1985) 664.
ally completed and is undergoing tests. It enables ¹⁰Be
[2] S.H. Sie and C.G. Ryan, Nucl. Instr. and Meth. B15 (1986)
and ¹⁴C measurements. The main problem encountered
664.
at present is the poor yield out of the source, which is
[3] S.H. Sie, C.G. Ryan, D.R. Cousens and W.L. Griffin, Nucl.
due to possible misalignment of the gun in the source
Instr. and Meth. B40/41 (1989) 690; B45 (1990) 604.
[4] L. Brown, Annual Rev. Earth. Plan. Sci. 12 (1984) 39; Phil.
itself, as well as misalignment of the beam transport
Trans. R. Soc. London A323 (1987) 57.
system.
[5] J.C. Rucklidge et al., Nucl. Instr. and Meth. 191 (1981) 1;
The second stage development will be directed to-
B45 (1990) 565.
wards heavy isotope detection and a microprobing
[6] J.B. Marion and F.C. Young, Nuclear Reaction Analysis
sputter ion source for detection of ultratraces in minera-
(North-Holland, Amsterdam, 1968).
logical research.
[7] D.J. Donahue et al., Radiocarbon 25 (1983) 719.
II. NEW & FUTURE FACILITIES
Scanning Microscopy, Vol. 5, No. 4, 1991 (Pages 977-987)
0891-7035/91$3.00+.00
Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA
MICRO-PIXE (PARTICLE-INDUCED X-RAY EMISSION ANALYSIS)
APPLICATIONS IN MINERALS RESEARCH
S.H. Sie*, C.G. Ryan and G.F. Suter
Heavy Ion Analytical Facility (HIAF)
CSIRO Division of Exploration Geoscience
(Received for publication May 6, 1991, and in revised form October 22, 1991)
Abstract
Introduction
The versatility of the PIXE method with microbeams
Microbeam methods in the geosciences have expanded
of protons as a non-destructive, in-situ probe for trace
rapidly within the past two decades, adding new dimensions
element analysis in the geosciences has been demonstrated
to established methodology and opening up new areas of
in an ever increasing number of cases. While in most
investigation. Much of the progress is due to the fact that
applications the method can be considered as derivative or as
detailed analysis can be carried out on monomineralic grains,
an extension of electron microprobe methodology, features
the basic constituent of all geological samples. With
unique to the proton microprobe enable new approaches to
micrometre size probes chemical composition can be
hitherto intractable problems of analysis. An appropriate
obtained on microstructures associated with the generation
niche has been established in igneous mineralogy and
and subsequent alteration of the minerals. The electron
petrology, with important implications both in the basic
microprobe has been responsible for identification of many
geosciences as well as mineral industry applications,
new minerals, with its prime capability of in-situ non-
particularly in the diamond exploration industry. This paper
destructive elemental analysis of the major and minor
reviews recent advances and discusses the advantages and
elements, and trace elements at concentrations above 500
limitations of current micro-PIXE applications in the
ppm. Secondary ion mass spectrometry (SIMS) with ion
geosciences in view of other competing and complimentary
microprobes is traditionally a tool for isotopic geochemistry
methods.
and geochronology, but is now also used as a trace analyzer
[Reed 1989]. A newcomer into the field is the synchrotron
radiation probe [Bos et al., 1984]. The proton microprobe
[Cookson et al., 1972, 1976] has also been in existence for
two decades and its applications in minerals research and in
other areas [Cahill, 1980] are expanding rapidly.
Applications of proton microbeam methods have
developed along two separate lines, similar to the
development of electron beam methodology. In one the
emphasis is on imaging applications and spatial resolution is
usually the driving force behind its development, akin to the
scanning electron microscope (SEM) development. The
other mode concentrates on quantitative analysis, usually
directed towards obtaining the best sensitivity for elemental
analysis, akin to the electron microprobe (EMP). With the
much lower level of accompanying background continuum
radiation, particle induced X-ray emission (PIXE)
KEY WORDS: Proton-microprobe, PIXE, X-ray analysis,
[Johansson et al, 1970, 1976, Folkmann et al 1974] offers a
trace element, geology, mineralogy.
sensitivity as much as 100 times better than electron induced
X-ray spectroscopy. The proton microprobe can also used
*Address for correspondence:
for Rutherford backscattering spectrometry (RBS) and
S.H. Sie
nuclear reaction analysis (NRA) [Toulhot et al. 1991, Courel
Heavy Ion Analytical Facility (HIAF)
et al. 1991]. When gamma rays are detected the method is
CSIRO Division of Exploration Geoscience
known as PIGME particle induced gamma ray emission,
P.O. Box 136, North Ryde NSW 2113, Australia
which is used mainly to detect low Z elements (e.g. F with
Phone No. 61 2 887-8648
ppm sensitivity [Bird and Clayton 1983]). Microbeams of
977
S.H. Sie, C.G. Ryan and G.F. Suter
particles other than protons have also been applied to
10
5
geological problems. Alpha beams have been used to
PIXE Minimum Detection Limits
determine H content of melt inclusions by the elastic recoil
Q = 10 uC E (p) = 3 MeV
detection method [Mosbah et al. 1991], and deuteron beams
10
4
4
Mineral
Al filter
have been used to determine C distribution in chondrites
3
1.Zircon
100 um
[Makjanic et al. 1991]. The present review relates to the
2
2.Garnet
200 um
10
3
1
3.Pyrite
300 um
application of PIXE with a microbeam as an in-situ
micrometre size samples in minerals research.
MDL (ppm)
4.Arsenoyrite
300 um
analytical method for quantitative trace element analysis on
Mineral composition is the basis of geochemistry: in
10
2
K
L
petrology and ore mineralogy it can reveal the more subtle
4
("cryptic") signatures of the geological processes involved in
3
their genesis. Partitioning of major and minor elements
10
1
between the melt and crystallizing phases is known to be
2
affected by the composition of the parent magmas, wallrock
interactions, the presence of volatiles and the ambient
0
50
100
pressure and temperature. Incompatible elements, occurring
Atomic number
as trace elements prove to be an even more sensitive probe
for these conditions and processes. The need for sensitive
10
5
micro-analytical techniques is particularly acute in
experimental petrology, where the geological processes are
simulated on a much smaller scale, and the resulting samples
Time (sec)
10
4
are microscopic.
Zircon (100um)
In ore mineralogy trace element data can provide
important indicators of the processes involved in ore
10
3
Arsenopyrite (300um)
formation and any subsequent diagenesis and
metamorphism. For precious-metal ores, detailed mass
Pyrite (300um)
Garnet (200mm)
balance calculations either for reserve estimation or
10
evaluation of beneficiation efficiency often require the
detailed distribution of the metal at trace levels carried by the
constituent minerals [Cabri 1987].
Method
Resolution (um)
10
Proton microbeams are focussed primarily using
0
50
100
quadrupole multiplets, but solenoids and plasma lenses are
Beam Current (nA)
also used successfully. For quadrupole based lenses,
magnetic systems predominate, and have produced the best
Figure 1. The top figure shows the minimum detection
resolution. The system at the CSIRO Heavy Ion Analytical
limits (MDL) defined at 99% confidence level for various
Facility (HIAF) is an electrostatic "Russian quadruplet
elements in a number of minerals, detected either through
system" [Sie and Ryan, 1986, Sie et al, 1990a] and tests have
their K lines or their L lines, for 3 MeV proton energy and
shown that a 3 micrometre beam spot can be produced.
10 microCoulomb beam charge. The Si(Li) detector
While micrometre or even submicrometre resolution may be
subtends a solid angle of 50 msr. The use of filters enhances
desirable in certain applications, in minerals research it must
the detection limit by suppressing the major element lines in
be weighed against other considerations:
the spectrum. Effects of the detector lineshape for high Z
- Quantitative analysis demands a low detection limit
element can be seen in the case of zircon, where the
in an acceptable measurement time. At HIAF this
detection limit in the vicinity of Z = 40 is worsened. The
minimum detection limit (MDL) is defined as 3.29 VB,
bottom figure shows the analysis time required. This
where B is the underlying background counts at the
depends on the beam intensity, which in turn is inversely
energy of the peak of interest over the range of 1.06
related to the beam resolution. At high beam currents, the
FWHM of the peak. This corresponds to 99%
count rate in the detector defines the minimum time limit.
confidence limit for a standard deviation of √2B.
The minimum times for the cases shown are given for a
Figure 1 (top) shows the MDL values for an
maximum count rate of 8000 counts per second.
assortment of minerals, for 10 microCoulomb beam
charge and for a detector with 50 msr acceptance solid
angle. A 2-3 ppm MDL of transition elements are
required to accumulate the charge is given in the
obtained for a silicate matrix, e.g. garnet. The time
bottom Figure 1, as a function of the available beam
978
Micro-PIXE Applications in Minerals Research
current. This in turn is determined by the beam
former when the accurate beam charge collection is not
resolution, also shown in the same figure. The 10 µC
available.
charge can be routinely achieved in 15 minutes using
In practice thicker filters are commonly used to
beams of 20 nA if a 15 µm beam is used. The
attenuate the major element lines to permit higher beam
measurement becomes impractical if the beam
currents to be used in order to enhance the detection of
intensity falls below 1 nA. Proton sources are several
heavier trace elements, and to reduce pile-up effects that can
orders of magnitude less bright than electron sources,
interfere with the lines of interest (e.g. U and Rb can be
and thus whereas nA's of beam is possible from
masked by pileup from Fe). For the K lines, the upper limit
electron microprobes at 1 micron resolution, for proton
is defined by the rapid decrease both in the proton ionization
probes the intensity falls well below the 1 nA limit.
cross section for the K shell and in the efficiency of the
The minimum time is defined either by the available
Si(Li) detector above ~30 keV, corresponding to Ba. From
beam or the count rate in the detector. If the count rate
the lanthanides onward the L lines are used, but with the
in the detector is maintained below 8000 counts per
ubiquitous Fe K lines dominating most spectra, there is a gap
second, the minimum time required, corresponding to
in detection sensitivity from Ce to ~ Sm.
the maximum permissible beam intensity, is shown in
The detection sensitivity is affected by the continuum
Figure 1 (bottom) for a number of cases.
background, which for most minerals is mainly due to
- The range of 2-4 MeV proton beam in minerals is
bremsstrahlung. The limited resolution of the Si(Li) and the
~60 µm (in silicates, less in sulfides), but self-
response function itself, e.g. the low energy tail of the
absorption effects of the X-rays in the matrix and the
photopeak due to incomplete charge collection in the
rapid fall of X-ray production rates with depth as the
detector poses another source for degradation of the MDL.
proton beam loses energy result in effective depths of
For instance, for high Z minerals such as zircon, the tail of
analysis of ~30-40 µm. This has some bearing on the
the Zr peak presents additional background and thus
selection of samples to be analyzed: whenever possible
reducing the sensitivity of detection of elements with X-ray
grains size should not be less than ~50 µm to avoid
lines below the Zr K lines, as can be seen in Figure 1. The
complications of contributions from the substrate or
dependence on the type of minerals is due to the differences
overlapping grains. Thus a beam spot of 5-30 µm in
in self absorption.
diameter is usually appropriate and provides ample
Many applications require analyses of large numbers
scope for increased beam currents (~5-20 nA)
of samples considering that geological samples commonly
necessary to achieve low detection limits. Samples are
are variable in nature. The hardware and software must be
prepared exactly as required for electron microprobe
designed to enable such operation. Desirable features
analysis, although in view of the large effective depth
include a facility for quick sample loading and the ability to
of analysis of protons the surface finish requirement is
view specimens readily with good magnification to both
not as stringent. On the other hand the specimen
position the specimen at the beam spot location and to
thickness should be thick enough to prevent excitation
identify microscopic features. The ability to change filters
of the substrate.
quickly is another desirable feature, especially during
In most PIXE applications, the X-rays are detected
reconnaissance studies of new types of specimens. The
with an EDS (energy dispersive spectrometer) system, with
software must enable reliable analyses of many spectra with
Si(Li) being the most commonly used. Hyperpure Ge
the least amount of intervention. One of the important
detectors are occasionally used to enhance detection of X-
features in the software developed at HIAF is the ability to
rays above 30 keV. Large volume Ge(Li) detectors are also
treat layered targets as required for analysis of thin or buried
used in conjunction with PIXE to detect gamma rays from
samples, and the effects of secondary fluorescence [Reuter et
selected light elements not detectable by PIXE. The use of
al. 1975]. The spectrum fitting procedure incorporates a
WDS (wavelength dispersive spectrometer) systems are
statistics-sensitive non-linear iterative peak-clipping (SNIP)
desirable, but at present their use is still not practical because
algorithm which provides a reliable continuum background
of the limitations in the available beam current intensity.
under low statistics peaks, both isolated and next to major
The EDS offers convenience in enabling simultaneous
lines [Ryan et al, 1988]. Up to triple pile up effects are also
multi-element detection, but also defines the regime of
included in the spectrum fitting. The method is free of user
applicability. In typical measurements, filters are used both
adjustable parameters to permit batch processing, rapid and
to protect the detector from the scattered proton beam, and
able to treat complex spectra [Ryan et al, 1990a]. Effects of
more critically as a control of detector efficiency to enhance
matrix absorption on the relative intensities of suites of lines
the sensitivity of detection of element(s) of interest.
are precalculated. Up to 16 L lines and 9 K lines, including
However, the thinnest absorber of the lightest element that
KLL and KMM radiative Auger lines are included in the
can be used as filter (Be) virtually eliminates all X-rays
calculation. The X-ray yields are based on the ECPSSR
below energies of ~1 keV defining the lightest element
ionization cross sections theory of Brandt and Lapicki
detectable to Na. For this reason, proton probe data must be
(1981) as calculated by Cohen and Harrigan (1985). The
complemented by electron probe data for the major
binary encounter approximation (BEA) theory [Garcia et al.,
elements. This can be conveniently used to normalize the
1973] for the ionization cross section are still used by many
other workers and can be selected if required. The analytical
979
S.H. Sie, C.G. Ryan and G.F. Suter
procedure has been tested against a number of geological
standards for trace element analysis (BCR-1, AGV-1, GSP-
Kimberlites
BASIC INTRUSIVES
1) and accuracies of 3% for major elements and down to 5%
50
SPINELS
for trace elements depending on statistics have been
demonstrated [Ryan et al, 1990b]. Details of the microprobe
system at HIAF and the tests are described elsewhere [Sie
and Ryan, 1986; Sie et al, 1989,1990a; Ryan et al 1990a,
40
1990b; Cousens et al. 1987a].
Applications
Cr (%)
30
As anticipated from earlier applications of EMP,
Lamproites
micro-PIXE has found an appropriate niche in igneous
mineralogy and petrology. The earliest application of the
proton microprobe was in fact the study of lunar and
20
meteoritic material [Bosch et al, 1978, 1980] and this area
continues to be a significant area of application [Blank et
al,1982,1984; Woolum et al. 1987, Bajt and Traxel 1991].
0
1000
2000
The distribution of incompatible elements, occurring as trace
Ni (ppm)
elements reveals detailed information about physico-
chemical processes associated with the formation of these
Figure 2. Correlation diagram of the distribution of trace
rocks. Similarly, in terrestrial samples the trace elements
element Ni plotted against the major element Cr from
allow the study of geological processes such as magma
chromites (Cr-spinel) show grouping according to the source
mixing and evolution, and the geochemical composition of
rock types. The shaded groups belonging to various barren
the upper mantle. Considerable new information on the
igneous rocks (gabbros, greenstone) show different trend to
upper mantle has been obtained from studies of xenoliths
kimberlites and lamproites, the two types of rocks which can
(fragments of lower crust or upper mantle rocks) and
be diamondiferous [from Sie et al 1989, Griffin et al 1990].
accessory mafic minerals in volcanic rocks of mantle origin
such as kimberlites.
Collection by stream and soil sampling of these
accessory minerals such as Cr-pyrope garnets ((Mg,Fe)₃
element Nb is steadily enriched in the residual magma and
(Al,Cr)₂(SiO₄)₃), chromian spinels ((Fe,Mg)(Cr,Al)₂O₄)
its products.
and ilmenites ((Fe,Mg)TiO₃) has been the basis of diamond
While partitioning of elements between the melt and
exploration, as a means of finding diamondiferous
the crystallizing phases is already useful as an empirical,
kimberlites [Griffin et al, 1990]. These minerals are
qualitative guide for exploration purposes, it is even more
dispersed by but resistant to weathering and their
exciting to use it quantitatively in modelling the evolution of
characteristics are used as means to find the source rock
magmas. The partition coefficients, sensitive to the
itself, and to assess its prospectivity. One of the aims of the
composition of the parent magma(s), pressure (P) and
micro-PIXE study of these indicator minerals is to
temperature (T) and valence of the elements can be derived
investigate the possibility of identifying the type of source
from natural systems if they are known to be closed and in
rocks and multiple sources [Griffin et al, 1990]. Chromites
equilibrium. Alternatively they can be obtained
for instance, are frequently used being most resistant to
experimentally from systems created in the laboratory which
weathering, but can originate from various types of barren
simulate mantle conditions. Micro-PIXE applications in
igneous rocks as well as from kimberlites. Figure 2 shows
experimental petrology offer the prospect of systematic
the trace element content of chromian spinels showing
studies of partitioning of geochemical marker elements, such
grouping of samples from different types of rocks. These
as the HFSE (high field strength elements e.g. Zr,Nb,Ta),
trends, and those from accompanying trace elements, can be
the LILE (large ion lithophile elements e.g. Rb,Ba,Sr,Y)
used as the basis of a quantitative classification schemes.
groups and possibly some of the REE (rare-earth elements)
Figure 3 shows the distribution of trace elements in
between coexisting phases and for different types of magma
ilmenites from a number of kimberlite pipes in South Africa,
under various conditions. For most of the minerals of
showing the grouping according to source. The grouping
interest (e.g. garnet, pyroxenes, olivine and amphiboles)
reflects the magmatic products sampled by the kimberlite,
MDL values of around 2 ppm can be obtained readily (in 4 - -
whereas the variation within each group reflects the effects
10 minutes with a 5-15 µm beam for a collected charge of 3
of fractional crystallization. As such magmas cool, they
µC) for the LILE and HFSE groups, but for all but the
precipitate various minerals which deplete or enrich the
heaviest REE the detection limit is poor at around 50-200
magma in certain elements: precipitation of mafic silicates
ppm because of the limitations discussed above.
such as olivine ((Mg,Fe)SiO₄) depletes the magma in Ni and
One experimental study of partitioning of Nb and Ta
that of zircon (ZrSiO₄) in Zr, while the incompatible
between basaltic melt and the crystallizing phases has
980
Micro-PIXE Applications in Minerals Research
The single mineral thermometer has significant implications
in diamond exploration, where the coexisting mineral is not
usually available. Diamonds are formed in a broad range of
1500
high pressure and temperature within the diamond stability
field. In craton areas, the geotherm intersects this field
Sekameng
between 900-1200°C. Analysis of the Ni in garnets can be
Lemphane
Kamfersdam
used to assess whether the host rock sampled material from
Ni (ppm)
Liqhobong
depths conducive to diamond formation [Griffin et al 1990].
1000
8 & 00880
Kao
During crystallization of minerals, fragments of other
Klipfontein
crystals present or portions of the melt or fluid can be
Koffeefontein
trapped in the crystal to form inclusions. Isolated from
further evolution, these inclusions preserve information
:
about P,T and chemical features of the system at the moment
of trapping. Micro-PIXE is ideally suited to study these
500
inclusions, which are typically minute (few tens of µm or
smaller).
Diamonds often contain such inclusions, classified
according to two major mantle rock types: perodotitic
Basalts
8.
(olivine and Cr rich garnets and spinels) and eclogitic
0
500
1000
1500
2000
2500
3000
(mainly clinopyroxene and low Cr garnets) suites. In one
study of West Australian diamonds, evidence of
Nb (ppm)
disequilibrium based on the trace element compositions of
Figure 3. Distribution of trace elements Ni, Nb in ilmenites
the inclusions led to the conclusion that the diamonds grew
from various kimberlite pipes show groupings which can be
in an open system [Griffin et al, 1988a].
used to identify multiple sources. The grouping represents
Melt inclusions trapped in mantle minerals, e.g.
the variation in the parent magma, while the trend in the
olivine, present the opportunity to study the geochemistry of
group reflects the effects of fractional crystallization during
the mantle. While the heterogeneity of the mantle is widely
the cooling of the magma. The distribution from kimberlites
accepted, direct evidence from the compositions of mantle
are well separated from that obtained from barren basalt
xenoliths and so-called primitive magmas (high Mg content)
(left). The fractional crystallization effect can be followed in
is complicated by various processes, e.g. magma mixing,
detail in one pipe. Precipitation of olivine depletes the melt
crustal assimilation, fractional crystallization and
in Ni, and zircon in Zr, while the element Nb is steadily
metasomatic events prior to the eruptive emplacement.
enriched in the residual magma and its product [from Sie et
Ratios of trace elements of the HFSE and LILE groups in
al 1989, Griffin et al 1990].
melts are known to be distinctive in different tectonic
environments [Pearce and Cann, 1973] and thus the study of
their content in these inclusions can reveal the characteristics
suggested large fractionation effects in the partitioning of Nb
of the primitive or source mantle magma. A micro-PIXE
and Ta, hitherto assumed to be geochemically coherent
study of inclusions from several tectonic environments and
[Green et al. 1989]. Similarly, in systems of mixed, or
lunar material [A.V. Sobolev, S.H. Sie, to be published)
immiscible melts (e.g. carbonatite and silicic melts), the
shows that these ratios (e.g. Zr/Y, Sr/Y) could be very
presence of volatiles and fluids can now be studied at levels
different from the host rock, and cannot be explained by
close to natural systems. A recent experimental study [T.H.
fractional crystallization effects of other phases present.
Green, S.H. Sie to be published] of partitioning of these
This indicates magma mixing and other processes during the
elements in a mixed silicate and carbonatite melt confirmed
evolution of the magma, while the characteristics of the
in detail the preference of LILE to partition into carbonatites.
mantle source are preserved in the inclusion. Figure 4 shows
The pressure and temperature dependence of the
spectra obtained from inclusions from three tectonic settings:
partitioning of elements between coexisting phases, usually
continental lithosphere, mid ocean rift and subduction zones.
pairs of minerals, has been exploited as the basis of
The contrast in the Zr/Y ratios are evident from the raw
geothermobarometry. Examples are the orthopyroxene/
spectra after allowing for overlaps of the K alpha and K beta
garnet barometer and the two-pyroxenes [Finnerty and Boyd
lines of the suite of elements (Rb,Sr,Y,Zr,Nb). The overlaps
(1987)], or garnet/olivine [O'Neill & Wood (1979, 1980)]
are resolved in the fit to the spectra, and the extracted Zr/Y
thermometers. One of the most exciting results of the
ratios are 21, 5 and 1 respectively for the three cases shown.
indicator-mineral study is the discovery of a single mineral
The Ni observed in the spectra originate from the host
thermometer: the Ni thermometer [Griffin et al, 1989]. This
olivine and was used to estimate the thickness of the
is based on the strong temperature dependence of the
inclusion samples. Figure 5 illustrates the method to
partitioning of Ni between garnet and olivine. However the
estimate the uncertainty in the deduced concentrations of
Ni content of olivine is relatively constant over a wide range
these elements using the Ni content as a guide. The yield of
of temperature, thus allowing the use of the garnet alone.
these elements normalized to the Fe content as % of that
981
S.H. Sie, C.G. Ryan and G.F. Suter
10
Fe
Meimechite incl.#15
3 MeV protons
Ni
Sr
inclusion thickness
10
200 jum Al filter
Zr
Mn
100
10
Ga
Fe (incl.) = 10%
10 mg/cm²
Nb
Cr
Rb
10
Cu
Zn
esc.
La
(x/Fe) incl. (%)
(ol.) = 7%
Ba
pile-up
Ce
10
(B)
50
5 mg/cm²
(A)
10
Fe
E-MORB incl #30/2/36
Counts per channel
10
Ni
Sr
50
100
10
Mn,
Zr
Ga
(Ni/Fe) / (Ni/Fe) (%)
Cr
Y
Br Rb
Nb
10
Figure 5. The Ni in the spectrum in fig. 4 is assumed to be
Cu
E
esc.
Zn
Ba
due entirely to olivine, and thus can be used to correct the
data. Theoretical calculation of the yield of elements X
10
normalized to the Fe content as % of that from an infinitely
thick sample is plotted against the corresponding ratio for Ni
normalized to the measured Ni content of the olivine. The
curves are calculated for Zr but the results for the other
10
Fe
elements Rb,Sr,Y, ,Nb and Ba are the same within 1%. The
Kamchatka incl.#9
Ni
two curves shown are calculated for the two extreme cases:
10
the samples are infinitely wide and hence the Ni can only
Sr
come from the underlying olivine, and in alternatively the
10
Mn
Zr
olivine due to the drift of the beam during analysis. The two
Crf
Rb
curves give the maximum uncertainty in the absolute
Y
10
concentration for a given Ni content in the spectrum, which
Cu
Ba
are of the order of 10%.
Zn
esc.
pile-up
10
The two curves shown are calculated for the two extreme
10
20
30
cases: the samples are infinitely wide and hence the Ni can
X-ray energy (keV)
only come from the underlying olivine, and in alternatively
the olivine comes only from the beam drift. The two curves
Figure 4. Spectra from melt inclusions in olivine from
give the maximum uncertainty in the absolute concentration
ultamafic rocks from different tectonic settings: continental
for a given Ni content in the spectrum, which are of the order
lithosphere (top), mid-ocean rifts (middle) and subducted
of 10%. However, the elements Rb,Ba,Sr,Nb,Zr and Y are
zone (bottom). The trace elements of interest are
totally incompatible with olivine so the ratios should not be
Rb,Sr,Y,Nb,Zr,Ba which are completely incompatible with
affected by olivine contamination and can be used reliably.
olivine. The Ni observed in the spectrum is due to the olivine
The study shows a wide range in the distribution of ratios,
and is used to estimate the olivine contribution to the
depending on the tectonic setting, and that the LILE/Y ratios
spectrum. The ratios of these elements to the Y content
are generally correlated with Zr/Y ratios except for Sr/Y
however should be unaffected and as can be seen vary
which is affected by the presence of plagioclase [A. Sobolev
widely with the different tectonic setting.
et al, to be published].
Evidence of alteration processes in the mantle is found
in metasomatized xenoliths, not only in the composition, but
from an infinitely thick sample is plotted against the
also in the microstructure of minerals. Smith and Boyd
corresponding ratio for Ni normalized to the measured Ni
[1987,1989] explained the zoning profiles on garnets in
content of the olivine. The olivine could also be analyzed if
sheared xenoliths from the kimberlites in southern Africa as
the beam drifts away from the sample during the analysis.
evidence of infiltration by melts/fluids prior to eruption.
982
Micro-PIXE Applications in Minerals Research
Micro-PIXE studies [Griffin et al, 1988b, Smith et al, 1991]
10
C1
Fe
of similar samples revealed corresponding zoning of some of
K
Ca
St. Mewans Beacon
the trace elements which provided further clues on the nature
Sample 2320
10
4
Fe
of the infiltrating fluid and on the time scale of both heating
Mn
Inclusion B1-e
and infiltration. Interpretation of the evidence of
Zn
metasomatism found in both deformed and undeformed
the Frank Smith mine example [Griffin et al, 1988b], the
Counts per channel
10
3
Zn
xenoliths is still a controversial subject. In the xenolith from
As
Rb
Br
Sr
10
clinopyroxene does not show zoning, indicative of high
Rb Sr
diffusion coefficients and rapid homogenization, whereas in
another study, the clinopyroxene in metasomatized spinel
10
lherzolite xenoliths shows evidence of zoning [Greig et al,to
PIXE FIT
be published]. What is understood is that it is a complex
5
10
15
process of both physical and chemical alteration of wall
X-ray energy (keV)
rocks in contact with magma or fluids, which can themselves
be undergoing differentiation [O'Reilly and Griffin, 1988].
Figure 6. A typical spectrum from analysis of a fluid
Whether the same agent causing obvious ("patent") chemical
inclusion in quartz at about 13 µm depth below the surface.
changes, e.g. the presence of hydrous secondary minerals, is
The depth is estimated from the Cl Kα/Kβ ratio to an
also responsible for the more subtle ("cryptic") changes
accuracy of 1.6 microns [from Ryan et al, 1991].
observed (e.g. the zoning profiles and enrichment or
depletion of trace elements), is not conclusive and the
problem remains an exciting area of application of micro-
other trace elements in sulfides (Cd,Sb,Sn,In,Se,Te) are also
PIXE.
of interest from the ore genesis point of view.
Minerals formed in hydrothermal systems contain fluid
Micro-PIXE has been used to determine Ag and other
inclusions, relics of the mineralizing fluids. In addition to
trace element distribution both in ore samples [Cabri et al
the homogenization temperature, the composition of the
1984, 1985; Harris et al 1984, Reeson et al 1990] and in mill
fluid inclusion reveals the characteristics of the mineralizing
concentrates [Sie et al, 1989]. While galena (PbS) is a
fluid. While occasionally there can be large (millimeter size
common carrier of Ag, other phases e.g. chalcopyrite
or greater) fluid inclusions, more often they are minute with
(CuFeS₂) can also be significant carriers. Considering the
dimensions in the tens of microns or less. Bulk techniques
large quantities of ores processed in base metal smelting,
involving crushing and leaching have been used to determine
recovery of trace quantities of Ag both in tailings and the
the average composition, but in this method different
main concentrate can translate into substantial additional
generations of inclusions are scrambled together.
revenue. With detailed distribution of Ag known, mass
Microanalytical methods such as ion-microprobes, electron
balance calculations can be carried out to evaluate the
microprobes and laser ablation have been used to infer the
efficiency of the beneficiation process. In galena, sphalerite
composition, but these involve decrepitation of inclusions.
(ZnS) and chalcopyrite the MDL of Ag is typically ~10 ppm.
This may result in partial or complete loss of elements
Similar analysis can also be applied to determine Au
carried by volatile components. Exploiting the large
distribution, particularly in refractory Au ore, so-called
penetration depths of the proton beam (e.g. about 60 µm in
because of its resistance to conventional cyanidization
quartz) it is possible to study these inclusions without
process. The unliberated Au is usually locked in solid
decrepitation [Horn and Traxel 1987, MacArthur et al. 1990,
solution in various phases, with arsenopyrite (FeAsS) being
Ryan et al. 1991]. At HIAF, the inclusions to be studied are
the most common carrier. However other more abundant
judiciously selected to be as near to the surface as possible
phases, e.g. pyrite (FeS₂) and pyrrhotite (FeS) can also carry
(5-15 µm) for efficient production of the X-rays of interest
some of the Au. An MDL of 5 ppm can be achieved in
from the inclusion and minimizing contribution from the
pyrite and pyrrhotite, while in arsenopyrite a poorer
host minerals, but allowing sufficient depth from the surface
sensitivity at 40 ppm is caused by the effect of the "tail" of
to avoid rupture under beam bombardment. A typical
the As Kα line that increases the background level for the
spectrum obtained from a fluid inclusion is shown in Figure
Au Lα line [Sie et al, 1989]. By using ion implanted
6. In this case, the ratio of the Cl Kα to Kß ratio is used to
standards [Chryssoulis 1989, Chryssoulis et al 1989] for
determine the depth of the inclusion to an accuracy of 1.6
accurate quantification, Cabri et al [1991] have demonstrated
µm [Ryan et al, 1991]. The uncertainty in estimation of the
that ion microprobe analysis can be used effectively in Au
depth and the usually irregular shape of the inclusion are the
determination in arsenian pyrite. Practical MDL values of
limiting error. However, it is possible to obtain reliable
~0.4 ppm were obtained, which were compared with 20-26
results when appropriate corrections are applied [Ryan et al,
ppm by micro-PIXE for about twice the analysis time of
1991].
about 15 minutes. While the ion microprobe has better
Precious metals (Ag, Au and PGE-platinum group
detection limit, the micro-PIXE can be applied more readily
elements) are often carried at trace levels by sulfides either
without the need for elaborate standardization. In the
in solid solution or as sub-microscopic inclusions. However
example cited (Cabri et al, 1991) the resultant errors of
983
S.H. Sie, C.G. Ryan and G.F. Suter
7-10 ppm in the ion microprobe measurements due to
levels below 0.1%. The elements immediately above Au
uncertainties in implant dose, depth measurements, counting
(Hg,Pb,Bi) can be detected through their Lγ lines with MDL
statistics and density inhomogeneity are comparable to the
values of ~200 ppm.
micro-PIXE errors of 11-26 ppm for the same set of samples.
The synchroton radiation probe has also been used to
Conclusion
determine Au with an MDL of 0.8-3 ppm [Chen et al.1987]
and spatial resolution of 20x20 µm. However the typically
The present applications are based mainly on EDS
limited access to such a facility may preclude its use as a
systems, which define most of the limitations and the
routine technique.
principal advantage of multi-element detection. Detection of
As in the case of Au, the detailed distribution of PGE
REE is still not satisfactory, nor are detection limits for
(platinum group elements: Pt,Pd,Rh,Ir,Ru,Re,Os) in an ore is
samples where the major element is of high Z, e.g. zircons,
of interest because of their high monetary value. While most
Au grains, galena. The use of WDS is desirable but at
PGE occur as free PGM (platinum group minerals) readily
present it is precluded mainly because of the limitations of
separable, economic quantities may be carried in other
the proton microbeam intensities.
phases. A micro-PIXE study of the Merensky Reef ore
On the physics side there is still the unresolved
revealed pentlandite ((Fe,Ni)gSg) as a significant carrier of
question on the accuracy of the calculated cross sections for
Ru,Rh,Pd at levels up to few hundred ppm, and to a lesser
X-ray production. There is a systematic difference in the
extent pyrrhotite as carrier of Ru(8-12 ppm) [Cousens et al,
energy and Z dependence of the ionization cross section
1987b, Sie et al 1990b]. In these minerals typical MDL
between the ECPSSR theory and the BEA theory used by
values are 2-6 ppm. Orberger and Traxel (1991) measured
many other PIXE users. However some of this problem can
Pd and Se content of Ni-Cu mineralization in an ophiolite
be circumvented through calibration against standards.
complex, and also found that Pd is carried mainly by
For large scale applications, appropriate for routine
pentlandite. Similar results have been obtained from ore
applications in exploration programs, it is desirable to reduce
samples from the Stillwater and Sudbury complex [Cabri et
the unit cost of analysis. This can be achieved for instance
al 1984].
by employing multiple detectors, which may be possible for
Other trace elements can contain genetic information,
a specific situation but difficult or expensive to implement
although at present the data are often difficult to interpret.
for a more versatile system.
Frequent associations of As with Au, e.g. the fact that
Despite the clear advantage of micro-PIXE in many
arsenopyrite and arsenian pyrite are often carriers of Au lead
areas, one has to be continually aware of alternative methods
to the anticipation that a genetic relationship can be found,
which can be more viable in specific cases, for example the
especially in epithermal sytems. A detailed study of the
use of SIMS for detection of Au in sulfides. The
trace element distribution in pyrite in an epithermal system
synchrotron radiation probe is also an alternative, and as
[Griffin et al, 1991] revealed a broad spatial correlation of
more facilities become available routine applications may
Cu, Sb, Se with As, and with Ag-Au grades, but there was
become possible, and competitive with micro-PIXE
no recognizable systematic variation in the chemistry of the
especially in the REE detection. Accelerator mass
pyrite near the mineralized zones. This was attributed to the
spectrometry is another new technique that can be used with
fact that the pyrite formation occurred over more episodes
sub-ppm detection limits for heavy elements, but further
than the precious metal deposition.
development is required to improve the spatial resolution of
The trace element distribution in gold itself may be a
the sputtering beam which currently stands at ~0.5 mm
better discriminant for genetic associations. The level of Ag
[Rucklidge et al, 1990].
which is nearly universally present and alloyed in Au is
The examples presented above clearly demonstrated
related to temperature of formation and salinity of the
the versatility of micro-PIXE in the geosciences and
mineralizing fluid. Other trace elements in Au
minerals research. Most applications can be regarded as an
(Fe,Cu,Zn,Hg,Pb) were originally detected by spectrographic
extension of EMP methods, but the higher sensitivity of
techniques by Warren and Thomson [1944], who went on to
PIXE reveals new features otherwise difficult to obtain or
conclude that their variation are controlled by the
not obtainable at all non-destructively. The larger range of
characteristics of the metallogenic provinces rather than the
protons used in the analysis allows new types of
type of deposit. Micro-PIXE enables systematic non-
measurements to be carried out (e.g. fluid inclusions). Real
destructive study of detrital Au to test this hypothesis, which
progress is marked by the transition from experimentation
if proven generally would have significant implications in
stage to contribution to the mainstream of geoscience, as for
exploration. A preliminary study on bedrock and alluvial Au
example in igneous petrology.
grains from several prospects in Tasmania appears promising
in showing differences in the trace element distribution
Acknowledgement
between different deposit types and styles of mineralization,
between deposits of the same type and between different
Most of the unpublished works quoted in the present
mineralogical associations [Sie et al, 1991]. Analysis of
review are based on collaborations at HIAF with J. Adam,
gold grains highlights the limits of the EDS system: most
R.A. Binns, S. Garrett, T.H. Green, A. Greig, R. Large, J.
elements adjacently below Au are virtually undetectable at
McAndrew, I.A. Nicholls, A.V. Sobolev. We thank
984
Micro-PIXE Applications in Minerals Research
W.L. Griffin and all reviewers, especially L. Cabri for
International Conf. Proc. (eds. Bennighoven A, Evans CA,
commenting on the manuscript.
McKeegan KD, Storms HA, Werner HW) Wiley, 405-408.
Chryssoulis SL, Cabri LJ, Lennard W (1989).
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Griffin WL, Ashley PM, Ryan CG, Sie SH, Suter GF
advances in the geosciences and heavy element analysis.
(1991). Pyrite geochemistry in the North Arm (Queensland)
Nucl. Inst. Meth. Phys. Res. B45:565-560.
epithermal gold deposit: a proton microprobe study. Can.
Ryan CG, Clayton E, Griffin WL, Sie SH, Cousens
Mineral. 29:185-198.
DR (1988). SNIP- A statistics-sensitive background
Harris DC, Cabri LJ, Nobiling R. (1984). Silver-
treatment for the quantitative analysis of the PIXE spectra in
Bearing chalcopyrite, a principal source of silver in the Izok
geoscience applications. Nucl. Instr. & Methods in Phys.
Lake massive sulfide deposit: confirmation by electron and
Res. B34:396-402.
proton microprobe analysis. Canadian Mineralogist 22:493-
Ryan CG, Cousens DR, Sie SH, Griffin WL, Suter GF,
498.
Clayton E (1990a). Quantitative PIXE Microanalysis of
Horn EE, Traxel K (1987). Investigations of
geological material using the CSIRO proton microprobe.
individual fluid inclusions with the Heidelberg proton
Nucl. Instr. Meth. Phys. Res. B47:55-71.
microprobe - A non destructive analytical method. Chemical
Ryan CG, Cousens DR, Sie SH, Griffin WL (1990b).
Geology 61:29-35.
Quantitative Analysis of PIXE Spectra in geoscience
Johansson TB, Akselsson R, Johansson SAE (1970).
applications. Nucl. Instr. Meth. Phys. Res. B49:271-276.
X-ray analysis: elemental trace analysis at the 10-12 g level.
Ryan CG, Cousens DR, Heinrich CA, Griffin WL, Sie
Nucl. Instr. Meth. 84:141-143.
SH, Mernagh TP (1991). Quantitative PIXE microanalysis
Johansson SAE, Johansson TB (1976). Analytical
of fluid inclusions based on a layered yield model. Nucl.
applications of particle induced X-ray emission. Nucl. Instr.
Instr. Meth. B54:292-297.
Meth. 137:473-516.
Sie SH, Ryan CG (1986). An electrostatic "Russian"
MacArthur JD, Ma XP, Palmer GR, Anderson AJ,
quadruplet microprobe Lens. Nucl. Inst. Meth. Phys. Res.
Clark AH (1990). Below surface analysis of inclusions with
B15:664-669.
PIXE and PIGE. Nucl. Instr.Meth. Phys. Res. B45:322-326.
Sie SH, Ryan CG, Cousens DR, Griffin WL (1989).
Makjanic J, Heymann D, Vis RD (1991). On the
Application of the proton microprobe in mineral exploration
discovery of C-rich rims around troilite grains in ordinary
and processing. Nucl. Instr. and Methods in Physics
chondrites. Nucl. Instr. Meth. B54:325-327.
Research, B40/41:690-697.
Mosbah M, Clocchiatti R, Tirira J, Gosset J, Massiot P,
Sie SH, Ryan CG, Cousens DR, Suter GF (1990a). A
Trocellier P (1991). Study of hydrogen in melt inclusions
Tandetron-based microbeam system. Nucl. Instr. Meth.
trapped in quartz with a nuclear microprobe. Nucl. Inst.
Phys. Res. B45, 543-547.
Meth. B54:298-303.
Sie SH, Cousens DR, Ryan CG, Griffin WL (1990b).
O'Neill HStC, Wood BJ (1979). An experimental
IBA in minerals research: progress and prospects. Nucl.
study of Fe-Mg partitioning between garnet and olivine and
Instr. Meth. Phys. Res. B45:604-609.
its calibration as a geothermometer. Contr. Mineral. Petrol.
Sie SH, Griffin WL, Ryan CG, Suter GF, Cousens DR
70:59-70.
(1991). The proton microprobe: a revolution in minerals
O'Neill HStC, Wood BJ (1980). An experimental
Analysis. Nucl. Inst. Meth. Phys. Res. B54:284-291.
study of Fe-Mg partitioning between garnet and olivine and
Smith D, Boyd FD (1987). Compositional hetero-
its calibration as a geothermometer: corrections. Contr.
geneities in a high-T lherzolite nodule and implications for
Mineral. Petrol. 72:337.
mantle processes. In Mantle Xenoliths (ed. P.H. Nixon)
Orberger B, Traxel K (1991). Proton-microprobe
J.Wiley & Sons, pp 551-561.
analyses of palladium and selenium in Ni-Cu-sulfides. Nucl.
Smith D, Boyd FR (1989). Compositional
Instr. Meth. B54:304-311.
heterogeneities in minerals of sheared lherzolite inclusions
O'Reilly SY, Griffin WL (1988). Mantle
from African kimberlites. In: Kimberlites and related rocks,
metasomatism beneath western Victoria, Australia: I.
vol. 2. Proc. IV Intl. Kimb. Conf. Geol. Soc. Australia Spec.
Metasomatic processes in Cr-diopside lherzolites. Geochem.
Pub. 14:709-724.
Cosmochem. Acta 52:433-447.
Smith D, Griffin WL, Ryan CG, Sie SH (1991). Trace
Pearce JA and Cann JR (1973). Tectonic setting of
element zonation in garnets from The Thumb: heating and
basic rocks determined using trace element analysis. Earth
melt infiltration below the Colorado Plateau. Contr. Min.
Plan. Sci. Lett. 19:290-300.
Petr. 107:60-79.
Reed SJB (1989). Ion microprobe analysis a review
Toulhoat N, Trocellier P, Massiot P, Gosset J, Trabelsi
of geological applications. Mineral. Mag. 53:3-24.
K, Rouaud T (1991). Deuterium, nitrogen and carbon
Reeson KJ, Stanley, Jeynes C, Grime G, Watt F.
mapping in oilfield rocks. Nucl. Instr. Meth. B54:312-316.
(1990). PIXE analysisto determine the trace element
Warren HV, Thompson RM (1944). Minor elements
concentrations in a series of galena (PbS) specimens from
in gold, Econ. Geol. 39:457-471.
different localities. Nucl. Instr. Meth. Phys. Res. B45:327-
Woolum DS, Burnett DS, Benjamin TM, Rogers PSZ,
332.
Duffy CJ, Maggiore CJ (1987). Trace element content of
Reuter W, Lurio A, Cardone F, Ziegler JF (1975).
promitive meteorites; a test of solar system abundance
Quantitative analysis of complex targets by proton induced
smoothness. Nucl. Instr. Meth. B22:376-379.
986
Micro-PIXE Applications in Minerals Research
Discussion with reviewers
specimen will have to be prepared as a thin section of
comparable thickness; otherwise the analysis will inevitably
G.Remond: You refer to the work by Chryssoulis et al.,
average over several zones. The ultimate limitation would
using ion implanted mineral for the analysis of Au with
be the beam intensity: with the presently available proton
SIMS. Did you try to use implanted materials for calibrating
sources the best beam current at 1µm resolution is only 100
your analytical procedure?
pA. It would be impractical from measurement time
Authors: There is no advantage in using implanted standards
consideration to carry out many spot analyses at beam
for PIXE because the uncertainty in the depth profile of the
current levels less than 1 nA.
implanted element(s) will contribute to errors even when the
exact dosage is known. Homogeneously doped standards
K.Traxel: Diamond is an ideal matrix for the proton
would be preferred although they are not any easier to
microprobe. Do you think that investigation of inclusions
prepare. In SIMS an implanted standard is needed to
could help in optimizing the production process for artificial
normalize the sputtering yield of the element of interest,
diamonds?
which is dependent not only on the matrix but also on the
Authors: The diamond inclusions reveal the conditions of
conditions during the measurement.
diamond growth in natural geological systems, which are
generally more complex than can be simulated under
M.L.Rivers: What are the problems associated with
laboratory conditions. The phase diagram (graphite-
radiation damage in micro-PIXE?
diamond) however is predominantly determined by P and T,
Authors: Most minerals, especially igneous ones are stable
and thus in principle it would be easier to produce diamonds
under beam bombardment, but thermal damage can occur at
artificially than to understand the exact conditions of
high currents resulting in fractures. Thermal effects will
diamond production in nature.
result in loss of material in hydrous minerals and carbon-
atites. In such cases one should reduce the beam intensity, or
S.Tapper: How are the detection limits in microbeam PIXE
reduce the beam areal density by defocussing the beam.
compared with the electron microprobe using a WDS
This is usually investigated during reconnaissance runs.
detection system in the region where L lines are used?
More often the problem is the failure of the epoxy employed
Authors: Detection limits by definition depend on
to hold the mineral grains, resulting in loss of the specimens.
conditions of measurements, and in many cases the type of
matrix and interferences. Under favourable conditions WDS
L.Rivers: What are the costs (capital and manpower)
with EMP can achieve 100 ppm MDL for heavy elements
involved in setting up a micro-PIXE facility?
(rare earth elements and heavier) using the L lines, and
Authors: A micro-PIXE facility can be built around a
sometimes better (50 ppm) if M lines are used. In PIXE with
dedicated accelerator, e.g. a 1.7 MV tandem or 3 MV single
an EDS the presence of Fe (typical for geological samples)
ended electrostatic accelerator. This can cost anywhere
limits the use of L lines to elements heavier than Sm, and
between $400K to $1M. The microprobe system can be
typical detection limits are between 10-100 ppm for
built for around $300K and anywhere between $40-200K for
integrated beam charge of 3 µC. For beam spot sizes of not
the data acquisition and analysis computers, depending on
less than 10 µm this can be achieved in 4-15 minutes, with
the degree of sophistication and application requirements. A
the shortest counting time limited by the count rate in the
minimum of 3 man-year scientific plus 3 man-year technical
detector. It should be noted that EDS is a multi-element
support would be required to put it all together. These
detection, and that WDS measurements typically require 3-4
figures are based on our experience in commissioning HIAF.
minutes per element.
With the present availability of suppliers of lenses and
software packages, I believe that a basic, turn-key system
S.Tapper: Is there enough difference between the matrix of
can be built for around $1.2M.
the fluid inclusion and the surrounding mineral, to enable a
(simultaneous) RBS analysis measurement of the depth of
K.Traxel: You mention that spatial resolution is of
the inclusion?
secondary importance in geochemical applications. Using
Authors: Tests that we have performed using combined RBS
the partitioning of trace elements between coexisting phases
and PIXE on fluid inclusions in quartz were not encour-
as a geothermometer must, however, also take care of the
aging. The already small contrast in energy between protons
possible zoning of the trace elements, especially in
scattered from the fluid-quartz interfaces are further
experimental petrology with its microscopic grains. Do you
obscured by the structure in the distinctly non-Rutherford
agree that spatial resolution is important in this context?
cross section of scattering on Si, O and C present in the fluid.
Authors: I agree that the spatial resolution is a desirable
feature, but one must be aware of the consequence of the
relatively large (10-30 µm) effective depth of analysis in
PIXE. If the zoning features are say less than 2 µm, then the
987
632
Nuclear Instruments and Methods in Physics Research B15 (1986) 632-635
North-Holland, Amsterdam
MRF318
ANALYSIS OF CARBON CONTENT AND DISTRIBUTION IN a-Si₁₋,C₁: H FILMS BY RESONANT
SCATTERING
S.H. SIE 1) D.R. McKENZIE ²), G.B. SMITH 3) and C.G RYAN 1)
1) CSIRO Division of Mineral Physics, PO Box 136, North Ryde, NSW, 2113, Australia
2) School of Physics, University of Sydney, Sydney, NSW, 2006, Australia
3) Department of Physics, New South Wales Institute of Technology, Sydney, NSW, 2007, Australia
Resonant alpha scattering has been used to determine detailed depth profiles of carbon in amorphous silicon carbon alloys
produced by glow discharge decomposition. The carbon profiles exhibit a two layer structure similar to that indicated by hydrogen
profiles in a-Si: H films. By comparison electron probe analysis seems to considerably overestimate average carbon content while
electron energy loss measurements on very thin specimens agree with the surface layer content in the resonance profiles of thicker
films. The bulk content is, however, still lower.
1. Introduction
of the samples were also examined by the resonance
scattering method [4].
Amorphous hydrogenated silicon-carbon alloys have
important applications in optoelectronic devices. They
have a variable optical gap [1] according to the carbon
2. Experimental method
content, adjustable from 1.8 eV for a-Si: H through a
maximum value of around 2.4 eV for intermediate com-
2.1. Sample preparation
positions to 2.0 eV for a-C:H. The alloys can be
produced by glow discharge decomposition techniques
The dc magnetron apparatus used in the production
from mixtures of silane and methane. The rates of
of the specimens has been described in detail elsewhere
decomposition of the two gases vary with conditions of
[5]. The cathode was stainless steel which was operated
manufacture and the mixture, and thus the carbon
in a condition in which it became overcoated with
content of the resultant material must be determined
silicon and carbon. Various mixtures of semiconductor
independently.
grade silane (SiH₄) and ultra high purity methane (CH₄)
Unfortunately, although there are a number of stud-
gases were used. Operating conditions for the mag-
ies of a-Si₁_ H in the literature, most of the methods
netron are shown in table 1. Substrates for the speci-
used for the analysis of film composition are dubious. It
mens were mounted on the anode. The cathode was
has recently been found [2] that two methods of analy-
operated for 5 min in the gases to be used for deposition
sis, electron probe microanalysis (EPMA) and electron
before the sample was inserted. Various substrate tem-
energy loss spectroscopy (EELS) give results differing
peratures were used, in the range 26-500°C (table 2).
by as much as factor of 2. Conventional RBS (Ruther-
Film thicknesses were measured using a Talystep step
ford backscattering) methods could, in favourable cases
height gauge.
(e.g. for thick films >1 µm), be used to determine C
content, but detailed profiles cannot be determined
reliably by this method. However, a strong resonance
occurs at a higher bombarding energy Eₐ = 4.26 MeV,
Table 1
which enhances the detection sensitivity and, as a result
The deposition conditions for a-Si₁ -xCx H films
of its narrow width, enables measurements of detailed
depth profiles [3].
Discharge voltage
900 V
In the following, carbon profiles in several a-
Current
30-50 mA
Magnetic field
0.01 T
xCx H thin film samples produced by the dc mag-
netron glow discharge method were obtained using the
Total gas pressure
1.2 Pa
Substrate (anode) cathode distance
30 mm
resonant α scattering technique. The results are com-
Substrate temperature
25-500°C
pared with other methods. The oxygen contents of some
0168-583X/86/$03.50 © Elsevier Science Publishers B.V.
(North-Holland Physics Publishing Division)
S.H. Sie et al. / Analysis of C content and distribution
633
Table 2
Summary of samples
Sample
A
B
C
D
E
F
G
H
I
Substrate
glass
glass
Cu
glass
suprasil
Cu
glass
glass
glass
Substrate temperature
(°C)
468
365
146
250
250
58
25
25
300
Methane fraction
0.50
0.50
0.50
0.50
0.25
0.5
0.67
0.50
0.50
Film thickness (Talystep)
(µm)
0.97
1.3
~1
~1
0.030
1.74
2
~1
-
2.2. Ion beam analysis
direction. The angular spread of the detector is 1° and
the solid angle accepted was 0.9 msr.
Analysis of the samples was carried out with alpha
In the case of carbon profiles, it is essential that a
particle beams with energies in the range 2.3-4.6 MeV,
good vacuum is obtained before measurements com-
supplied by a 3 MV Tandetron at the CSIRO heavy ion
mence. A base pressure of 6 10⁻⁸ Torr was obtained,
analytical facility (HIAF).
and at this pressure there was no evidence of carbon
RBS measurements at 2.3 MeV were carried out to
buildup on the target under prolonged beam bombard-
check the structure and the thicknesses of the films.
ment. The targets were stable under irradiation with
The carbon profiles were measured using the reso-
beam currents as high as 100 nA, as confirmed by
nance scattering 12 C(α, α') at Eα = 4.26 MeV with a
repeat measurements.
width Γ = 33 keV. The characteristics of this resonance
The total widths of the resonances including the
are similar to the resonance used for oxygen profiles,
detector resolution (18 keV) translate into 81 and 39 nm
employing the reaction ¹⁶O(α, α') at Eα = 3.036 MeV
depth resolutions at the surface for C and O respec-
with Γ = 8.1 keV. Both resonances show strong angular
tively, in pure Si. These increase to 94 and 63 nm at a
distributions peaked towards the back angles. All mea-
depth of 1 µm in Si.
surements, including RBS, were carried out with the
Typical spectra obtained below and just above the
detector angle set at 165° with respect to the beam
resonances are shown in fig. 1. Resonance yields were
1300
(a)
(c)
1100
Eα = 2.3 MeV
= 3.99 MeV
900
700
0
0
Si
Si
500
Na
Na
300
Counts/channel
K
K
100
630
0
(b)
(d)
Eα = 3.04 MeV
((res)
Eα = 4.27 MeV
490
O(res)
350
Si
0
210
Na
Na
Si
70.00
K
K
200.0
400.0
600.0
800.0
200.0
400.0
600.0
800 0
Channel number
Fig. 1. An example of typical backscattered particle spectra obtained from a-Si₁ xCx H (sample H, see table 2) on glass substrates (a)
below the resonances, (b) just above the oxygen resonance, (c) just below the carbon resonance and (d) just above the carbon
resonance. The elements K, Na and bulk O originate from the glass substrate.
XII. COMBINED TECHNIQUES
634
S.H. Sie et al. / Analysis of C content and distribution
calibrated against a pure carbon (graphite) target for the
9
carbon analysis, and against a quartz target for the
a
A
8
0.5 um (Si)
B
oxygen analysis.
G
7
D
6
3. Results and discussion
Carbon content (%)
5
4
Carbon profiles from the samples studied are shown
in fig. 2. All samples exhibit a broad surface peak with
3
widths greater than the resolution of the resonance. The
2
possibility that these peaks are carbon buildup under
1
beam bombardment due to residual hydrocarbons in the
vacuum system is unlikely when one examines the range
0
4:20
4.25
4.30
4.35
4.40
of intensity of these surface peaks in different samples.
Eα(MeV)
The presence of these peaks, which can be significantly
different to the "bulk" region, point to the need for
22
caution in the interpretation of other methods of analy-
b
1um (Si)
20
C
sis which do not give detailed depth distributions or
F
18
H
which rely on very thin specimens. The results for the
16
0
present measurements are tabulated in table 3, includ-
I
ing EPMA results for a few of the samples. The present
14
results are divided into the "surface region" and "bulk"
components. The "surface region" was taken to be the
Carbon content (%)
12
10
layer corresponding to 0.25 µm thickness (calculated
8
assuming bulk silicon density, see fig. 2a, b) for samples
A, B, E, G and to 0.5 µm for samples C, D, F, H, I. The
6
remainder of the thickness was defined as "bulk". The
4
numbers obtained are necessarily coarse (with about
2
20% error) owing to the arbitrariness of the division.
0
The "average" number represents an average over the
4.10
4.20
4.30
4.40
4.50
4.60
thickness of the film, for the purpose of comparisons
Eα(MeV)
with other methods. Although these estimates involve
Fig. 2. Carbon profiles (in at.%) obtained from the samples
uncertainties, especially in those cases where the profiles
tabulated in table 2. All exhibit a surface peak region at various
were not measured through the full thickness of the
relative intensities to the "bulk" concentrations. The depth
film, they form a useful framework for the following
scales indicated were calculated assuming pure silicon.
observations. Fig. 3 shows the observed relationship
between the methane fraction of the source gas mixture
and the measured carbon content by EPMA and elec-
than EELS. This may reflect the uncertainty in EPMA
tron energy loss (EELS) for samples produced under the
analysis due to the very low X-ray energy (0.282 keV)
same conditions, together with a selection of results
which can be strongly absorbed by the silicon matrix
from the current samples all at substrate temperatures
and effects of secondary fluorescence of the carbon by
of 250-300°C. EELS results lie above the average val-
silicon X-rays. It is plausible that EPMA gives a correct
ues, but agree well with surface region content. The
analysis for certain depths, and when the distribution is
EELS films, being very thin, probably only have surface
uniform. Several works have reported good agreement
characteristics. EPMA results are systematically higher
between EPMA and AES analysis [1]. The latter analysed
Table 3
Carbon content of samples analyses (atomic fraction)
Sample
A
B
C
D
E
F
G
H
I
This work
"Surface peak" region
0.057
0.041
0.191
0.128
0.009
0.157
0.019
0.160
0.079
"Bulk"
0.014
0.011
0.152
0.049
0.007
0.138
0.016
0.047
0.017
Average
0.035
0.030
0.172
0.089
0.008
0.148
0.0175
0.103
0.048
EPMA
0.20
0.25
0.20
S.H. Sie et al. / Analysis of C content and distribution
635
under the same conditions as our thicker films, appear
80
not to develop bulk characteristics.
70
The carbon profiles in the present samples indicate
the existence of a two layer structure, such as that
60
deduced from hydrogen profiles in amorphous hydro-
Carbon content (%)
genated silicon films produced by glow discharge de-
50
composition [6]. In the present case the carbon profile is
40
EPMA
the indicator of this structure, as H was in the case of
EELS
a-Si H films. Hydrogen profile measurements are in
30
progress currently to check if there is correlation be-
tween C and H profiles. The oxygen profiles measured
20
in a few of the samples do not show any correlation
D
10
with the carbon profiles. All cases studied indicate very
RELS
E
low concentrations of oxygen, which appear mainly
0
0.0
0.2
0.4
0.6
0.8
1.0
near the film-substrate interface. Some of this oxygen
Methane gas fraction
may be due to mixing effects from the substrate.
Fig. 3. Results of various methods of analysis for carbon
The average concentrations produced with a 50%
content (in at.%) as a function of the methane gas fraction in
silane/50% methane mixture are shown in fig. 4. De-
the source gas for samples produced at 250-300°C substrate
spite the large range of concentration in each sample
temperature. EPMA electron probe micro analysis, EELS -
due to the presence of "surface" layers, they are rich in
electron energy loss analysis, RELS resonant elastic scatter-
silicon. Of most significance is the strong dependence
ing (samples D, E, I).
on the substrate temperature. Higher temperatures re-
sult in even more silicon rich films, with a transition in
samples to depths up to around 20 A, thus sampling
the region of 200-300°C (fig. 4).
only the surface layer.
The higher temperatures also appear to result in
When a strong variation in C concentration occurs in
samples with strong surface peaks, with the sample
samples such as those studied here, particularly in sam-
produced at 146°C showing the broadest peak.
ples with lower C content, EPMA will give erroneous
average concentrations when compared to resonant
4. Conclusions
scattering measurements covering the whole thickness of
the sample. All profiles measured here show strong
The resonance scattering technique proved to be a
surface peaks extending to depths of ~ 0.3 µm. EPMA
useful method for determining depth profiles of carbon,
analysis sampling the surface peak would thus be likely
and also of oxygen, in thin films of a-Si₁-xCx : H. The
to result in an overestimate of the average concentra-
typically detailed structure of the profiles, with varying
tion. EELS indicates that very thin films, prepared
surface region to bulk ratios of concentration, may
partially explain the large discrepancy between this
method and electron probe methods, which only sample
20
C
the surface region, but other sources of error are ap-
18
Surface
parent in EPMA. Electron energy loss spectroscopy of
H
F
16
Average
very thin films produced under the same conditions
Bulk
14
D
gives concentrations in agreement with surface layer
content but above bulk values. Bulk characteristics have
Carbon content (%)
12
thus not developed in the EELS samples.
10
I
8
References
6
A
B
[1] R.S. Sussmann and R. Ogden, Phil. Mag. B44 (1981) 137.
4
[2] A. Sproul, D.R. McKenzie and D.J. Cockayne, submitted
2
to Phil. Mag. B.
[3] M. Östling, C.S. Petersson and G. Possnert, Nucl. Instr.
0
0
100
200
300
400
500
and Meth. 218 (1983) 439.
Substrate temperature (°C)
[4] S.H. Sie, D.R. McKenzie, G.B. Smith and C.G. Ryan, these
Fig. 4. Substrate temperature dependence of the carbon content
Proceedings (1BA '85) Nucl. Instr. and Meth. B15 (1986)
(in at.%) for a 50% silane/50% methane gas mixture. The
525.
values shown are averaged over the thickness of the films. The
[5] D.R. McKenzie, J. Appl. Phys. 56 (1984) 2356.
samples are all relatively rich in Si, especially at higher sub-
[6] E. Sacher, J. Klemberg-Sapieha, M.R. Wertheimer, H.P.
Schreiber and R. Groleau, Phil. Mag. B49 (1984) L47.
strate temperature.
XII. COMBINED TECHNIQUES
Nuclear Instruments and Methods in Physics Research B15 (1986) 525-529
525
North-Holland, Amsterdam
MR F 317
DEPTH PROFILES OF HYDROGEN AND OXYGEN IN HYDROGENATED AMORPHOUS
SILICON THIN FILMS
S.H. SIE D.R. McKENZIE ²), G.B. SMITH 3) and C.G. RYAN 1)
1) CSIRO Division of Mineral Physics, P.O. Box 136, North Ryde, NSW 2113, Australia
2) School of Physics, University of Sydney, NSW 2006, Australia
3) Department of Physics, New South Wales Institute of Technology, Sydney, NSW 2007, Australia
Detailed depth profiles of hydrogen and oxygen have been measured in samples of thin films of a-Si: H produced by dc magnetron
glow discharge techniques. The resonant capture reaction ¹H(¹⁹F, αγ)¹⁶O at E₁₉F = 6.417 MeV was used for hydrogen profile
measurements, and resonant α scattering at Eₐ = 3.0359 MeV was used for oxygen. Contrasting results reflecting the different
fabrication conditions were obtained and these were correlated with measured electrical properties.
1. Introduction
tive interpretation of the resultant data is difficult [5].
Electron energy loss spectroscopy (EELS) and Ruther-
The electrical and optical properties of a-Si H pro-
ford back scattering spectrometry (RBS) can yield infor-
duced by glow discharge decomposition of silane are
mation on depth profiles, but the nuclear reactions
related to the distribution of hydrogen. Incorporated in
18 O(p, α)¹⁵ N and ¹⁸O(p, γ)¹⁹F are more commonly
the silicon network, hydrogen increases dopability by
used [6]. These reactions however rely on the rare iso-
terminating dangling bonds [1]. However hydrogen may
tope ¹⁸O, and are therefore impractical due to the
also be present in other forms, particularly as hydroxyls
reduced sensitivity in natural targets. The deuteron re-
when moisture absorption occurs, which could be detri-
actions O(d, p) or (d, n) have also been used, but the
mental to the electrical properties.
high radiation background produced by these beams
The presence of oxygen in the bulk of a semiconduc-
makes the technique less attractive [6].
tor can also affect its electrical properties, and on the
In this paper, we report the use of resonant α
surface it can affect contact properties, which are im-
scattering to determine the oxygen profiles, exploiting
portant for device applications. Surface defects may in
the resonance at an α bombarding energy of Eₐ = 3.0359
fact dominate electrical properties by creating mobile
MeV. Results are presented together with hydrogen
carrier accumulation layers [2]. Oxidation can be ex-
profiles obtained from the same specimens, to delineate
pected to be one source of oxygen, but a major contri-
the sources of these elements and correlate them with
bution could come from adsorption and absorption of
the properties of the samples.
moisture into microvoids, typically found in films of
semiconductor produced by vacuum deposition tech-
niques. The porosity of the films depends on the fabri-
2. Experimental procedure
cation conditions, and thus the hydrogen and oxygen
contents may be used to diagnose the effects of different
2.1. Film preparation
conditions.
In the following, a number of samples of thin films
Various parameters in the glow discharge deposition
of a-Si: H produced by dc magnetron glow discharge
of a-Si H in the dc magnetron system have a consider-
have been studied. Hydrogen profiles were determined
able impact on the electrical, optical and mechanical
using the ¹H(¹⁹F, αγ)¹⁶O resonant reaction at a ¹⁹F
properties of the films [7]. In particular, very significant
bombarding energy of 6.417 MeV. Preliminary results of
differences are observed between samples prepared with
these measurements have been reported [3].
the substrate at cathode potential, where there is consid-
Oxygen content is usually determined as part of the
erable bombardment by energetic positive ions and also
hydroxyl using the infrared absorption (IR) technique
fast deposition rates of up to 3.5 nm/s. Electrical
[4], which does not provide depth profile information.
measurements have indicated that the surfaces play a
Some attempts have been made to measure oxygen
more significant role under these conditions, and one
profiles using Auger electron spectroscopy (AES) and
aim of this study was to see whether the hydrogen and
secondary ion mass spectrometry (SIMS), but quantita-
oxygen profiles could be used to distinguish between
0168-583X/86/$03.50 © Elsevier Science Publishers B.V.
X. NUCLEAR REACTION ANALYSIS
(North-Holland Physics Publishing Division)
526
S.H. Sie et al. / Depth profiles of hydrogen and oxygen
Table 1
Preparation conditions for a-Si: H samples
Sample
Electrode
Power
Silane
Deposition
Magnetic
Substrate
dissipated
pressure
rate
field
temperature
(W)
(mbar)
(nm/s)
(T)
(°C)
A
anode
25
0.0076
0.10
0.05
315
B
anode
57
0.0078
0.58
0.05
370
C
cathode
23
0.040
2.67
0.03
320
those surface effects due to the production process and
fluorine bombarding energy of 6.417 MeV was used in
those due to subsequent adsorption.
the hydrogen profile measurements. This resonance,
Other parameters of importance are substrate tem-
while not as strong as the more commonly used one at
perature, SiH₄ partial pressure, power dissipated in the
E¹⁹F = 16.44 MeV, gives better depth resolution and is
discharge, and strength of the magnetron field. For
more isolated giving a larger accessible depth range.
anodic deposition higher deposition rates produce bet-
Using the definition of depth resolution given, for ex-
ter electrical properties [7]. Full details of the deposition
ample, in ref. [10], the resonance width of 45 keV
system are given elsewhere [7,8].
translates into a 11 nm depth resolution in pure silicon
Table 1 summarizes the central parameters for the
at the surface, increasing to 27 nm at 1 µm depth.
three films analysed in this study. Two are anodic, and
The unique reaction Y rays of 6.1 MeV were detected
differ only in deposition rate, the other is cathodic.
in a pair of 7.5 cm diameter X 20 cm long Nal detectors
Microscope glass slides were used as substrates. For IR
placed outside the vacuum chamber 3 cm from the
measurements of samples A and B, a thin Al layer
target. The close geometry helped to minimize the rela-
50 nm) was evaporated onto the substrate prior to
tive cosmic ray background. Resonance yields between
the a-Si deposition.
3.5 and 7.0 MeV were measured relative to polyethylene
((CH₂)ₙ) and mylar (C₁₀H₈O₄) targets. Normalized to
2.2. Film properties
their respective hydrogen contents, these two targets
gave similar results (within 2%). Measurements on these
Thickness was measured with a step profiling stylus
targets were carried out with less than 2 nA beam
(Talystep). The thickness of the samples on the same
currents, and the decreasing yield due to target decom-
substrate varies (by 20%) monotonically across the
position was monitored as a function of irradiation
length of the substrate as a result of the configuration of
dose. The maximum yield, corresponding to the initial
the apparatus. Dark conductivity (σd) and photocon-
condition, was obtained by extrapolation to zero irradi-
ductivity (σₚₕ) were measured in a gap cell geometry. Of
ation time. The actual samples studied appeared to be
particular significance to this work is the magnitude of
stable under bombardment with beam currents as high
dark conductivity with σd 10⁻⁹ (Ω cm) denoting
as 100 nA.
minimal surface effects and σd 10⁻⁵ (Ω cm)⁻¹ denot-
All measurements were carried out in a vacuum of
ing a dominance of surface effects. This in turn in-
≤ 1 x 10⁻⁷ mbar and no trace of carbon build up on
fluences the photoconductivity for reasons discussed by
the target was observed.
Smith and McKenzie [9], such that the essential parame-
RBS was used primarily to check the areal density of
ter for evaluating the effect of surface layers is the gain
the samples employing beams of 2.3 MeV α particles.
in conductivity on illumination as a ratio rather than a
The backscattered particles were measured with a surface
magnitude, that is σₚₕ/σ. These parameters are all
barrier detector at 165° with respect to the beam direc-
summarized in table 2. Clearly the ratio of σₚₕ/σd rises
as σd falls and the cathodic sample appears to be
Table 2
influenced much more than the other two by surface
Film properties
effects.
Sample
Dark
Photo-
0ph
2.3. Ion beam analysis
conductivity
conductivity
od
at 300 K
at 300 K
The hydrogen and oxygen profiles as well as RBS
d (Ω cm)⁻¹
°ph (Ω
measurements were performed at the CSIRO Heavy Ion
A
~10⁻⁷
~5x10⁻⁵
500
Analytical Facility (HIAF), an accelerator laboratory
B
6.4x10⁻¹⁰
1.9x10⁻⁶
3000
based on a 3 MV Tandetron.
C
1.2x10⁻⁴
5x10⁻⁴
4
The resonant capture reaction H(¹⁹F, αγ)¹⁶O at a
S.H. Sie et al. / Depth profiles of hydrogen and oxygen
527
1000
Depth (nm) Si
0
100
200
300
400
α
glass
Eα = 2.3 MeV
a-Si
AI
A
- 20% H
(0)
a-Si
500
0
Al
(K)
Resonance yield (arbitrary units)
C
(Na)
10,000
— 13.7 %H
B
Counts channel
- 10.5%H
0
Eα = 3.04 MeV
600
5000
- 8%H
0 Resonance
(0)
at surface)
Glass
Si
AI
(Na)
substrate
400
Al
a-Si
200
0
6.5
7.0
7.5
Elab MeV
(K)
Fig. 2. Hydrogen profiles in the three a-Si: H samples studied.
0
0.5
1.0
1.5
2.0
Conditions of manufacture of the samples are given in table 1.
E ( MeV )
A depth scale to guide the reader is calculated for pure silicon.
Fig. 1. Typical spectra from an a-Si: H sample taken below and
above the resonance at Eₐ = 3.0359 MeV. This sample (A) was
produced on a glass substrate coated first with a thin Al layer.
and C. For sample B, the substrate interface was not
The thick target features of elements K. Na, 0 originate from
reached in these measurements. The cathodic deposition
the glass substrate.
(sample C) results in a higher bulk hydrogen content,
with some structure near the surface. Results for the
oxygen profiles are shown in fig. 3. For samples A and
tion, at a distance of 75 mm, subtending a solid angle of
C the substrate interface can be discerned as the part
0.9 msr at the target.
with a similar profile to quartz. Again for sample B the
The same experimental setup was used for the oxygen
measurements did not extend to the substrate. The high
profile measurements, employing the resonant α scatter-
O content in sample A made it possible to separate the
ing at an incident beam energy of 3.0359 MeV. Al-
resonance yield from the sample and that of the sub-
though this resonance has been known for some time
strate. The glass substrates used provided a convenient
[11], it has only recently been used in profiling [12]. The
check on the resonance yield calibration, as well as on
angular distribution at the resonance is peaked towards
the thickness of the film. This can be obtained from the
the back angles, and consequently measurements were
shift of the resonance curve from the glass backing
carried out at the furthest angle in the backward direc-
which has a similar shape to that obtained from quartz.
tion of 165°. The resonance yield was measured relative
For samples A and B, the film thicknesses can also be
to a fused quartz target, which is assumed to be pure
deduced from the hydrogen profiles, but due to the
SiO₂, confirmed by RBS. The RBS and resonant
variation in thickness the results do not necessarily
scattering spectra are shown in fig. 1. The width of the
agree exactly with those obtained from the resonant
resonance (8.1 keV) is less than the detector resolution
RBS measurements. Because three components are
of 18 keV. Using the same definition [10], the depth
involved, the relations between the atomic concentra-
resolution from the total width is 39 nm, increasing to
tions of H and O and their respective resonance yields
63 nm at 1 µm depth in pure silicon.
are not linear. The values shown in the figures corre-
sponding to major features of the profiles were obtained
by iteration.
3. Results and discussion
The need for both hydrogen and oxygen profiles is
apparent when the profiles and electrical data are inter-
Hydrogen profiles from the three samples are shown
preted together.
in fig. 2. Results from samples A and B have been
The greatest surprise was the oxygen profile in the
reported previously [3]. The substrate interface can be
ion bombarded sample C. This profile indicates no
discerned as a rapid drop in H content in samples A
oxygen related surface structure (fig. 3), contrary to
X. NUCLEAR REACTION ANALYSIS
528
S.H. Sie et al. / Depth profiles of hydrogen and oxygen
QUARTZ
A
10000
0
100
200
300 nm (Si)
x
Resonance yield (arbitrary units)
Surface
Surface
5000
a-Si
Al
Glass
substrate
24 at %
X
0
X
3.00
3.05
3.10
3.00
3.05
3.10
Eα ( MeV)
C
B
10000
0
100
200
300
400 nm(Si)
0
100
200
300
400nm(Si)
Resonance yield (arbitrary units)
Surface
Surface
5000
Glass
substrate
4 at %
5 at %
0
b-
3.00
3.05
3.10
3.00
3:05
3:10
3.20
Eα MeV
Fig. 3. Oxygen profiles corresponding to the resonance yield measured on fused quartz and the a-Si: H samples. Depth scales, again
only to be used as a guide, are given for pure silicon. The glass substrate can be identified as the part resembling the quartz profile.
expectations based on the electrical properties. How-
(silane) pressure. In the ion-beam analyses, no evidence
ever, a definite surface layer 40 nm thick is seen in
of carbon build up on the samples under beam
the hydrogen profile. The surface profiles of H have
bombardment was observed, indicating minimal or no
been referred to by others [13] with the significant drop
hydrocarbon contamination. Possible contribution from
in concentration indicative of a boundary between a
the vacuum system is further eliminated when the same
surface layer of different structure to the bulk. The
profiles were obtained from repeat measurements.
evidence is mainly obtained from nuclear reaction stud-
It is more likely the hydrogen rich surface is an
ies but other techniques such as permeability [13] have
intrinsic property of the surface. Growth models have
produced similar evidence.
been postulated which provide a surface layer ~ 20 nm
The excess hydrogen relative to oxygen observed for
thick with different properties to the bulk [13]. This
the surface region in samples B and C (fig. 2) cannot be
hydrogen rich layer may represent an incomplete reac-
accounted for in terms of moisture adsorption only. The
tion zone with an excess of dangling bonds with molecu-
possibility that hydrocarbons may be adsorbed on the
lar hydrogen or other forms containing hydrogen in the
surface [13] is unlikely in the present case. In the
microvoids. Such a zone could be expected to extend
production of the samples, the hydrocarbon partial
deeper in ion bombarded samples, as in sample C, due
pressure due to possible backstreaming of contaminants
to mixing effects between layers during growth.
from the vacuum pumps at a base pressure of 10⁻⁷
The cathodic films are also extremely adherent as
mbar would be negligible compared to the source gas
deduced from a scratch test. The rise in the oxygen
S.H. Sie et al. / Depth profiles of hydrogen and oxygen
529
profile near the substrate where the hydrogen falls off
4. Conclusions
indicates ion mixing with the substrate, which could
provide greater mechanical strength. By contrast with
Films produced anodically by the dc magnetron glow
sample A (see below), the film is not very porous so that
discharge system were shown previously [7] to have
there is little scope for adsorption.
improved electrical properties at higher deposition rates;
The two anodic samples are quite different to the
the increased rate also improved the quality of solar
cathodic sample and to each other. Here the evidence
cells [14]. This improvement can be associated with a
for a surface layer which might influence electrical
decrease in porosity deduced from a lower moisture
behaviour, as observed, is clear cut for A. The atomic
intake, as implied from the oxygen and hydrogen pro-
ratios of hydrogen 20 at.%) and oxygen 24 at.%)
files.
indicate other sources of oxygen, such as surface oxide.
Similar deductions for the cathodic samples imply
But the main source, given the close correlation of the
that they have low porosity, however their electrical
oxygen and hydrogen profiles over the full film, is either
properties are dominated by surface layer effects. Re-
adsorbed water or hydroxyl. The thickness of surface
sults of the present study suggest that these surface
peaks in both the H and O profiles for this sample A
effects are linked to a distinct surface layer which is
appears to be ~ 100 nm, showing a significant level of
hydrogen rich as a result of the growth process under
penetration of water or hydroxyl into the film bulk.
these conditions of strong ion bombardment.
This in turn denotes high porosity, particularly in the
surface region.
Sample B, in contrast to both other samples, shows a
References
surface depleted in hydrogen and no clear cut demarca-
tion zone but a gradual rise to the bulk value. A weak
[1] J.D. Joannopoulos and G. Lucovsky (eds.), Physics of
surface oxide peak is however observed. Electrically this
Hydrogenated Amorphous Silicon, vol. 1 (Springer Verlag,
film is the best of those analysed here (low dark current
Berlin, 1984).
[2] B. Aker and H. Fritzsche, J. Appl. Phys. 54 (1983) 6628.
and high σₚₕ/σď, although significantly better results
[3] S.H. Sie, D.R. McKenzie and G.B. Smith, Appl. Surf. Sci.
have been produced using this technique [9]. This film is
22/23 (1985) 916.
very much softer (as shown by the scratch test) than
[4] M.H. Brodsky, M. Cardona and J.C. Knights, Phys. Rev.
sample C and is less dense, as deduced from IR reflec-
B16 (1977) 3556.
tivity. The porosity or void structure in these anodic
[5] W. Reuter, Nucl. Instr. and Meth. 218 (1983) 391.
films appears to be strongly influenced by deposition
[6] J.F. Ziegler (ed.), New Uses of Ion Accelerators (Plenum
rate.
Press, New York, 1975).
In sample B the correlation of hydrogen and oxygen
[7] G.B. Smith and D.R. McKenzie, Solar Energy Mater. 11
is relatively constant in the vicinity of the surface. This
(1984) 45.
indicates the probable penetration of water into the
[8] D.R. McKenzie, J. Appl. Phys. 56 (1984) 2356.
film. However the depth at which the oxygen become
[9] G.B. Smith and D.R. McKenzie, submitted for publica-
tion.
negligible is well away from the film-substrate inter-
[10] C.A. Barnes, J.C. Overley, Z.E. Switkowski and T.A.
face. This film has much less water penetration than its
Tombrello, Appl. Phys. Lett. 31 (1977) 239.
more slowly deposited counterpart, sample A. The re-
[11] J.R. Cameron, Phys.Rev. 90 (1953) 839.
duced hydrogen at the surface of B could be due in part
[12] S. Petersson, H. Norde, G. Possnert and B. Orre, Nucl.
to the higher substrate temperature.
Instr. and Meth. 149 (1978) 285.
[13] E. Sacher, J. Klemberg-Sapieha, M.R. Wertheimer, H.P.
Schreiber and R. Groleau, Philos. Mag. B49 (1984) L47.
[14] G.B. Smith and D.R. McKenzie, Appl. Surf. Sci. 22/23
(1985) 891.
X. NUCLEAR REACTION ANALYSIS
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P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203541
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
SALE, Stephen: FEHRENBACHER, SALE, QUINN & DEESE
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 12/01/92
SUBJECT: HE IS ASKING DR. BROMLEY TO WRITE A LETTER ON BEHALF
OF DR. ZAHID AND HIS EFFORTS TO SECURE A VISA FOR
HIS WIFE.
DIRECTORATE
STAFF
ASSIGNED: D. Allan Bromley
ASSIGNED:
ACTION
STAFF
REQUIRED: AS APPROPRIATE
ACTION:
SENDER'S DUE DATE:
OSTP DUE DATE:
12/18/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT:
COPIES TO:
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
OSTP RECEIVED: 12/07/92
DEPT RECEIVED:
FILE: P-DAB-PERSONAL
CENTRAL FILES:
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
03a. Letter
To: Allan Bromley From: Stephen Sale
12/1/92
(b)(6)
Re: Request for letter of behalf of Dr. Zahid and his wife
[personal information redacted] (2 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
03b. Letter
To: Mary Ann Carey, Ambassador to Algeria, From: Allan
(b)(6)
Bromley
Re: Support for visa application for Dr. Zahid and his wife
[personal information redacted] (1 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
"Document Control"
TYPÉ:
ACTION
DOCUMENT NUMBER: 9203509
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
ROSENFELD, LOUIS: NYU MEDICAL CENTER
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 11/23/92
SUBJECT: REQUEST TO SEND A LETTER OF SUPPORT TO HONOR BOTH
oTTo FOLIN AND DONALD VAN SLYKE ON A U.S. POSTAGE
STAMP.
DIRECTORATE
STAFF
ASSIGNED:
D. Allan Bromley
ASSIGNED:
ACTION
STAFF
REQUIRED: AS NECESSARY
ACTION:
The om
SENDER'S DUE DATE:
OSTP DUE DATE:
12/09/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT:
COPIES TO:
Charlie close ml
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
OSTP RECEIVED: 12/02/92
DEPT RECEIVED:
FILE: P-DAB-REFERRAL
CENTRAL FILES:
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
04a. Letter
To: Allan Bromley From: Louis Rosenfeld
11/23/92
(b)(6)
Re: Requests Letter of Recommendation for Otto Folin and
Donald Van Slyke [personal information redacted] (1 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
04b. Biography
Biography of Otto Folin and Donald Van Slyke [personal
(b)(6)
information redacted] (3 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203498
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
WALLACE, Charles E.: LAMALIE AMROP INTERNATIONAL
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 11/09/92
SUBJECT: HE IS WRITING TO SEEK DR. BROMLEY'S HELP IN FINDING
CANDIDATES FOR THE THE POSITION OF THE FIRST CEO FOR
THE AUSTRALIAN TECHNOLOGY GROUP.
DIRECTORATE
STAFF
ASSIGNED:
ALL ASSOCIATE DIRECTORS
ASSIGNED:
ACTION
STAFF
REQUIRED: COMMENTS TO DAB
ACTION:
SENDER'S DUE DATE:
OSTP DUE DATE:
12/10/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT:
COPIES TO:
D. Allan Bromley
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
I don't have any candidate to suggest
OSTP RECEIVED: 11/13/92
DEPT RECEIVED:
Engine way
FILE: P-DAB-REFERRAL
CENTRAL FILES:
1410
Charlie,
& into know who
dirfted the letter
himalf, but the is
as if DAB mate
frint to me, is C.T.
office sent I've had
should up and on Primilla
DEC 2 1992
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203498
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
WALLACE, Charles E.: LAMALIE AMROP INTERNATIONAL
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 11/09/92
SUBJECT: HE IS WRITING TO SEEK DR. BROMLEY'S HELP IN FINDING
CANDIDATES FOR THE THE POSITION OF THE FIRST CEO FOR
THE AUSTRALIAN TECHNOLOGY GROUP.
DIRECTORATE
STAFF
ASSIGNED:
ALL ASSOCIATE DIRECTORS
ASSIGNED:
See white
ACTION
STAFF
REQUIRED: COMMENTS TO DAB
ACTION:
SENDER'S DUE DATE:
OSTP DUE DATE:
12/10/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT: 12/9/92
COPIES TO: ALL ASSOCIATE DIRECTORS
D. Allan Bromley
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
Allan - I believe the restrictions -
PAS's post- gout service rule out many
logical candidites In this. I can think
of name others.
Kand
OSTP RECEIVED: 11/13/92
DEPT RECEIVED:
FILE: P-DAB-REFERRAL
CENTRAL FILES:
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203498
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
WALLACE, Charles E.: LAMALIE AMROP INTERNATIONAL
TO:
DR. D.A. BROMLEY
pn
DATE OF
CORRESPONDENCE: 11/09/92
SUBJECT: HE IS WRITING TO SEEK DR. BROMLEY'S HELP IN FINDING
CANDIDATES FOR THE THE POSITION OF THE FIRST CEO FOR
THE AUSTRALIAN TECHNOLOGY GROUP.
DIRECTORATE
STAFF
ASSIGNED:
ALL ASSOCIATE DIRECTORS
ASSIGNED:
Deffactive we ficod
ACTION
STAFF
REQUIRED:
COMMENTS TO DAB
ACTION:
A
SENDER'S DUE DATE:
OSTP DUE DATE:
12/10/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT: 12/9/22
COPIES TO:
D. Allan Bromley
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
OSTP RECEIVED: 11/13/92
DEPT RECEIVED:
FILE: P-DAB-REFERRAL
CENTRAL FILES:
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
05a. Letter
To: Charles Wallace From: Allan Bromley
12/9/92
(b)(6)
Re: Response to request for help in finding candidates for a
position [personal information redacted] (1 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
05b. Letter
To: Allan Bromley From: Charles Wallace
11/9/92
(b)(6)
Re: Request for help in finding candidates for a position
[personal information redacted] (1 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act - [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
05c.
Job Description [personal information redacted] (1 pp.)
(b)(6)
Announcement
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203361
ORIGINATOR: 02
STATUS I
DIRECTORATE STATUS
FROM:
HARMS, Timothy: THE CONFERENCE OF FEDERAL ENVIRONMENTAL
ENGINEERS
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 11/04/92
SUBJECT: HE IS REQUESTING NOMINATIONS FOR THE FEDERAL
ENVIRONMENTAL ENGINEER OF THE YEAR AWARD.
DIRECTORATE
STAFF
ASSIGNED:
D. Allan Bromley
ASSIGNED:
ACTION
STAFF
REQUIRED:
AS APPROPRIATE
ACTION:
SENDER'S DUE DATE: 01/16/93
OSTP DUE DATE:
11/16/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT:
COPIES TO: ENVIRONMENT
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS:
OSTP RECEIVED: 11/04/92
DEPT RECEIVED:
FILE: P-DAB-REFERRAL
CENTRAL FILES:
"Document Control"
TYPE:
ACTION
DOCUMENT NUMBER: 9203361
ORIGINATOR: 02-05
STATUS I
DIRECTORATE STATUS C
FROM:
HARMS, Timothy: THE CONFERENCE OF FEDERAL ENVIRONMENTAL
ENGINEERS
TO:
DR. D.A. BROMLEY
DATE OF
CORRESPONDENCE: 11/04/92
SUBJECT: HE IS REQUESTING NOMINATIONS FOR THE FEDERAL
ENVIRONMENTAL ENGINEER OF THE YEAR AWARD.
DIRECTORATE
STAFF
ASSIGNED:
D. Allan Bromley
ASSIGNED:
close CB out
ACTION
STAFF
REQUIRED: AS APPROPRIATE
ACTION:
SENDER'S DUE DATE: 01/16/93
OSTP DUE DATE:
11/16/92
STAFF DUE DATE
DATE COMPLETED:
DATE COMPLETED/DEPT:
11/16/92
COPIES TO: ENVIRONMENT
WHITE HOUSE TRACKING #:
CONTACT PERSON:
PHONE:
EXT:
REMARKS Reassigned to Karl Erb, 11/16/92
Allan I do not believe theme has her an
environmental engineer an OSTP's personal vasta in recent
years. B.11 Busch would be lose, but he was a
OSTP detailee. RECEIVED: If 11/04/92 you want DEPT to RECEIVED: naminate Bill, nancy May nad
FILE: P-DAB-REFERRAL
CENTRAL
FILES: - - Bill's Syservisor should be able Lo help.
dV/16 Karl El
Withdrawal/Redaction Sheet
(George Bush Library)
Document No.
Subject/Title of Document
Date
Restriction
Class.
and Type
06. Letter
To: Allan Bromley From: Timothy Harms
10/30/92
(b)(6)
Re: Request for nomination for Federal Environmental
Engineer of the Year award [personal information redacted]
(2 pp.)
Collection:
Record Group:
Bush Presidential Records
Office:
Science and Technology Policy, Office of (OSTP)
Series:
Bromley, D. Allan, Files
Subseries:
Correspondence Files
WHORM Cat.:
File Location:
D. Allan Bromley: Referrals [2 of 7] [1992]
Date Closed:
1/11/2010
OA/ID Number:
62006-008
FOIA/SYS Case #:
2005-0336-F
Appeal Case #:
Re-review Case #:
Appeal Disposition:
P-2/P-5 Review Case #:
Disposition Date:
AR Case #:
MR Case #:
AR Disposition:
MR Disposition:
AR Disposition Date:
MR Disposition Date:
RESTRICTION CODES
Presidential Records Act - [44 U.S.C. 2204(a)]
Freedom of Information Act [5 U.S.C. 552(b)]
P-1 National Security Classified Information [(a)(1) of the PRA]
(b)(1) National security classified information [(b)(1) of the FOIA]
P-2 Relating to the appointment to Federal office [(a)(2) of the PRA]
(b)(2) Release would disclose internal personnel rules and practices of an
P-3 Release would violate a Federal statute [(a)(3) of the PRA]
agency [(b)(2) of the FOIA]
P-4 Release would disclose trade secrets or confidential commercial or
(b)(3) Release would violate a Federal statute [(b)(3) of the FOIA]
financial information [(a)(4) of the PRA]
(b)(4) Release would disclose trade secrets or confidential or financial
P-5 Release would disclose confidential advice between the President
information [(b)(4) of the FOIA]
and his advisors, or between such advisors [a)(5) of the PRA]
(b)(6) Release would constitute a clearly unwarranted invasion of
P-6 Release would constitute a clearly unwarranted invasion of
personal privacy [(b)(6) of the FOIA]
personal privacy [(a)(6) of the PRA]
(b)(7) Release would disclose information compiled for law enforcement
purposes [(b)(7) of the FOIA]
C. Closed in accordance with restrictions contained in donor's deed of
(b)(8) Release would disclose information concerning the regulation of
gift.
financial institutions [(b)(8) of the FOIA]
(b)(9) Release would disclose geological or geophysical information
PRM. Removed as a personal record misfile.
CONFERENCE OF
FEDERAL ENVIRONMENTAL ENGINEERS
Nomination for
FEDERAL ENVIRONMENTAL ENGINEER
OF THE YEAR AWARD
1992
Agency making the nomination:
Agency point of contact:
Address:
Telephone Number:
NAME OF NOMINEE:
Position Title:
Organization and mailing address:
Telephone Number:
INITIAL QUALIFICATION OF THE NOMINEE
Only those who meet the following definition of an
environmental engineer shall be eligible for the award. "An
environmental engineer is defined as one who possesses a
Baccalaureate or higher degree in engineering from a recognized
college or university, or is licensed as an engineer by an official
state licensing agency for professional engineers; or is classified
in the Federal Service as an engineer and has prepared himself
through additional study, training and experience in the sciences
in combination with engineering, as applied to the control and
improvement of the environment for the protection and promotion of
health."
Nominee's Qualification (only one category required):
1. Name of College/University and Engineering Degree:
2. Professional Engineering License (give state and license
number): :
3. Present Job Classification in the Federal Service (If this
is the only category used to qualify the nominee, provide
a summary of training, education, or experience for the
position):
- Position Title:
- Federal Service Occupational Code:
SELECTION CRITERIA
Environmental Contributions - limited to the last two years
(70 Percent)
The engineering of a system, process, or item of
equipment characterized by initiative and imagination to
an unusual degree which resulted in an advance of the
art, a new application to environmental engineering, or
which contributes significantly to the solution of an
important and difficult problem; or
The development of a major improvement in a management
procedure which increases efficiency, reduces cost, saves
time, or otherwise contributes in large measure to the
accomplishment of an important task; or
A record of achievement or sustained exemplary leadership
in the management of environmental engineering programs.
Professional Prestige
(30 Percent)
Furnishes inspiration to and enhances the prestige of his
or her professional colleagues.
Attach a maximum of four (4) pages of narrative for the nomination.
Narrative is to be on 8.5" X 11" paper with not less than one inch
margin on all sides and no more than 12 characters per inch.
Return completed nominations NO LATER THAN January 16, 1993 to:
Mr. Anthony Tesoriero
12203 Cedarbrook Lane
Laurel, Maryland 20708