Geochemistry and Mineralogy Laboratories
The Inorganic Geochemistry Laboratory provides support and services to Geoscience Australia’s national and regional programs, mineral systems research and regolith studies.
The laboratory specialises in the analysis and identification of rock and soil material, as well as the fluids trapped in rocks.
The laboratory manager must be contacted at the project planning stage if use of the laboratory facilities is envisaged. This ensures that correct sample collection procedures are chosen for the specific analytical processes required, and subsequently, the correct methods and procedures are chosen. It also allows the proper scheduling and resourcing of the work requested.
The laboratory is housed in modern facilities, has a team highly skilled and educated staff trained to not only operate the latest analytical equipment but to provide interpretation of data. The quality of the data is assured by using standard operating procedures and quality control measures which enable the accuracy and precision of the data to be demonstrated.
The aim of sample preparation is to produce a sample that is both representative and homogeneous of the sample submitted, and also suitable for the many analytical processes required for analysis in the laboratory. Sample preparation is essential for the liberation of elements of interest, aids in decomposition techniques, and reduces particle size effects in techniques such as X-ray fluorescence (XRF). The end result for geochemical samples is a fine, dry material or powder.
It must be noted that these initial processes will contaminate the sample due to the physical processes involved in reducing a sample to a fine powder. However, with careful choice of the preparation media and liaising with laboratory managers and staff, contamination can be accounted for and minimised.
Hydraulic rock splitter (Rocklabs): The hydraulic rock splitter is equipped with tungsten carbide blades and plates to minimise sample contamination, and is used to split large samples into smaller, manageable pieces suitable for the next processes, and also useful in removing weathered material from the sample if requested.
Swing-jaw crusher (Rocklabs): Following the hydraulic rock splitter, swing-jaw crusher is used to reduce samples to less than 20mm diameter. The jaw faces are made of low contaminant mild steel.
Boyd crusher (Rocklabs): Following the Swing-jaw crusher, the Boyd crusher, with attached rotary sample divider, reduces samples to less than 4mm. The sample divider can be adjusted to sample between 2% and 50% of the final crush.
Vibratory ring mill (Rocklabs): Following the Boyd crusher the ring mill is used to pulverise the coarser product to a very fine powder. The two most frequently used grinding media are the tungsten carbide (contaminants W and Co), and the tool steel (contaminants Fe, Mn, C, Si).
A number of different analytical techniques for the analysis of geochemical materials are used within the laboratory, including X-ray Fluorescence (XRF) Spectrometry; Laser Ablation (LA-ICP-MS), and solution Inductively Coupled Plasma Mass Spectrometry (ICP-MS); carbon, hydrogen and moisture analysis; volumetric, gravimetric and electrochemical methods and Laser Raman Microprobe (LRMP).
The Wavelength Dispersive XRF from Bruker (S8 Tiger) is used for analysing fusion and pressed powder samples for elements with an atomic number greater than 9. The equipment can measure concentrations as low as 1ppm and as high as 100%. The XRF is equipped with an automated sample loader and online data processing software.
Sample preparation for the XRF involves:
- the preparation of fused discs for the analysis of major elements (Si, Ti, Al, Fe, Mg, Mn, Ca, Na, K, P, S) using a semi-automatic furnace (Initiative Scientific Products Fusilux 4X4 Fusion Machine), and
- the preparation of pressed powder pellets for the analysis of trace elements (Activon Automated Speca press).
LA-ICP-MS and solution ICP-MS
The ICP-MS from Agilent Technologies (7500ce) is traditionally used with solutions, made by acid digestion of the fused discs previously analysed by the XRF. The ICP-MS is equipped with an automated sample loader and online data processing software, and presently can analyse approximately 45 trace elements with detection limits down to parts per billion levels.
The ICP-MS is also equipped with a New Wave UP-193nm solid state laser ablation system for analysis of solid samples.
The C/H/moisture analyser from Leco (RC-612) is used for the determination of organic and inorganic carbon, as well as bound water, in rock and soil samples. This instrument measures the quantity of carbon and hydrogen present in the sample, and the temperature at which they are liberated.
Volumetric, gravimetric and electrochemical methods
Supplementary analyses such as ferrous iron, loss on ignition and specific gravity also are available. Other specialised techniques may be used on request.
Mineralogical and fluid inclusion facilities
Laser Raman Microprobe (LRMP)
The HORIBA Jobin Yvon SuperLabram Laser Raman Microprobe has a fully confocal microscope and is used for the rapid and non-destructive analysis of solids, liquids and gases. The high spatial resolution of this instrument (≥ 1 micron) makes it particularly suitable for the identification of gases and solids in fluid inclusions. The Laser Raman Microprobe is equipped with a motorised stage also, which allows Raman mapping of selected areas of the sample. An optical-fibre probe can be attached to the spectrometer and used for probing larger samples that do not fit under the microscope, such as hand specimens and drill core.
X-ray Diffraction (XRD) spectrometry
The XRD from Bruker (D4 Endeavor) is used to identify minerals in powdered samples. The TOPAS software package is used to quantitatively determine the amount of each mineral identified by its X-ray diffraction pattern.
Portable Infrared Mineral Analyser (PIMA)
The PIMA from Integrated Spectronics is a field-portable, shortwave infrared spectrometer which provides rapid data on rocks and minerals. The accompanying software contains a library of PIMA mineral spectra allowing easy interpretation of unknown spectra. Measurements can be made on all types of samples including diamond drill-cores, reverse circulation (RC) and rotary air blast (RAB) chips, powders and soil samples.
Electron Probe Micro-Analyser (EPMA)
The Cameca SX-100 electron probe micro-analyser is a shared Geoscience Australia-Australian National University facility used for the analysis of elements in very small areas such as individual mineral grains. It is equipped with four wavelength dispersive X-ray spectrometers and an energy dispersive spectrometer. Cathodoluminescence and backscattered electron images also may be obtained in the scanning mode. This instrument is primarily used for major element microanalysis with detection limits typically exceeding 50-100ppm. However, detection limits may be extended into the trace element range by the use of longer counting times and precise background corrections.
Heating and freezing stages
These laboratories contain the following heating and freezing stages which are used mainly for fluid and melt inclusion studies:
- Linkam MDS (IR-adapted) 600 stage (-196°C to +600°C). This stage is mounted on an infrared microscope equipped with a Hamamatsu IR camera and a mercury lamp for UV illumination. The Linksys software is used for automated temperature control and capture of digital images at specified time or temperature intervals;
- Linkam TS 1500 stage (20 to 1500°C). This stage is automatically controlled with a TS94 programmer;
- Fluidinc modified USGS gas flow stage (-196 to +700°C). This stage is mounted on a microscope equipped with a Sony video camera for viewing;
- ChaixMeca stage (-196 to +600°C); and
- Leica 1350 stage (25 to 1350°C).
Transmitted and reflected light microscopes
These laboratories contain a range of research-grade, polarising microscopes and binocular microscope including:
- Leica DMRX polarising microscope which can be operated in transmitted or reflected or both simultaneously and is equipped with a Leica DFC 320 digital camera for microphotography;
- Leitz Orthoplan polarising microscope equipped with mercury lamp for UV illumination;
- Leitz Orthoplan polarising microscope equipped with a Leica DC100 digital camera and diamond-coated microdrill for cutting small sections from petrological thin sections;
- Olympus BX60 polarising microscope equipped with IR Optics and IR camera (400-2200nm) and mercury lamp for UV illumination; and
- Wild M400 Photomakroskop - stereo binocular microscope.
Contact the laboratory manager for further details.