Sample Preparation and Physical Geology Laboratory
The Sample Preparation and Physical Geology Laboratory supports a range of research activities which contributes to the improved understanding of Australia's petroleum, mineral and water resources and environmental management. We specialise in micropalaeontology preparations and analysis of sediments.
Description: Palynology is the study of extant and extinct palynomorphs which includes pollen, spores, acritarchs, chitinozoa and dinoflagellates. While these organisms are unrelated, they are grouped together because their preserved remains are composed of a chemically stable mixture of biopolymers called sporopollenin.
Process: Sediments are chemically and physically treated using a variety of acids, oxidising agents, heavy liquids and sieving techniques to concentrate any palynomorphs they contain. Microscopic slides containing the palynomorphs are then prepared for viewing.
Uses: Palynology is often used to derive biostratigraphic and palaeoenvironmental information from sediments and is increasingly being applied in forensic studies.
Description: Diatoms are a major group of photosynthesising algae which are encased in a silica cell wall called a frustule. They are found in a diverse range of environments including marine, freshwater and moist soils. Diatoms are commonly between 20-200 microns but can be up to 2 millimetres in length.
Process: Diatom slides are prepared for viewing under an optical microscope. Slides can be prepared by making a simple smear slide or a more refined technique using chemicals to remove unwanted material to concentrate the specimens.
Uses: Diatoms are extensively used in environmental studies as indicators of waterway ecology and also have applications in palaeoclimate, palaeotsunami and forensic studies.
Description: Foraminifera or forams are found in all marine environments. They are single celled organisms, generally with a calcareous shell called a test. However foram test construction may also be proteinaceous or agglutinated i.e. composed of cemented particles. They range in size from <1 millimetre and up to 20 centimetres, but are usually no more than a few millimetres in diameter. Forams can be planktic (floating) or benthic (sea floor) dwelling.
Process: Foraminifera are prepared for viewing under an optical microscope. Depending on the rock type, hard samples are made into thin sections, while softer sediments are disaggregated and the forams concentrated using chemicals and sieving techniques.
Uses: Forams can be used for palaeoceanographic, palaeoclimate, biostratigraphic and other environmental purposes. They can also be used for a variety of isotopic dating methods.
Description: Calcareous nannofossils or coccoliths are calcium carbonate plates formed by coccolithophorids, which are single celled algal organisms found in marine environments. Coccoliths are held together by an organic coating to create coccospheres. Individual coccoliths range in size from 0.25 microns to 20 microns but are usually 5-10 microns in size.
Process: Calcareous nannofossils are prepared for viewing with an optical or electron microscope. Microscopic slides are prepared by making a smear slide or a dilution of the disaggregated sample.
Uses: Coccoliths are used for palaeoceanographic, palaeoclimate, biostratigraphic and other environmental studies.
Description: Conodont elements are phosphatic tooth-like structures which are believed to have been part of the feeding apparatus of an extinct early proto-chordate. They are found in marine sediments such as shale, limestone and dolomite. Conodont elements typically range in size within 1-3 millimetres.
Process: Conodonts are prepared for viewing with an optical or electron microscope. Specimens are concentrated by digesting or disaggregating samples using various chemicals, heavy liquids and sieving techniques.
Uses: Conodonts are useful as biostratigraphic indices for Ordovician to Triassic strata. The conodont alteration index (CAI) can be used to determine the temperature sediments have been subjected to and from this depth of burial can be inferred.
Description: Ostracods belong to the group metazoan meaning many cells. Their body parts are covered with a hinged shell composed of low magnesium calcite. They are found today in almost all aquatic environments.
Process: Ostracods are prepared for viewing with an optical or electron microscope. Specimens are concentrated by digesting or disaggregating samples using various chemicals, heavy liquids and sieving techniques.
Uses: Ostracods are used for biostratigraphic and environmental studies.
Description: Grainsize determinate as weight percentage by wet sieving.
Process: Samples are wet and dry sieved into Wentworth scale fractions. These are then dried, weighed and the fractions expressed as percentage mass. Sieves used are 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16000micron. The <63 fraction is collected and weighed. A measured portion is processed through the laser grainsize analyser (see below) to provide the clay and silt fractions.
Uses: Grainsize distribution studies can be used to determine sediment transport patterns, sorting and energy of deposition, infer sediment porosity, calibrate submarine sonar, detect hydrocarbon seeps and establish surrogacy for benthic ecology. Sieved size fractions can undergo further scientific analysis to determine more detailed geological, physical, chemical and biological properties specific to each fraction.
Description: Grainsize determination as volume percentage by laser diffraction.
Process: Approximately one gram of sediment is dispersed in water and laser diffraction particle size analysis is used to calculate the volume percentage of particles in the sample. This is a highly precise method suitable for particles in the range of 0.02-2000 microns.
Uses: Grainsize distribution studies can be used to determine sediment transport patterns, sorting and energy of deposition, infer sediment porosity, calibrate submarine sonar, detect hydrocarbon seeps and establish surrogacy for benthic ecology.
Description: The carbonate percentage is determined by acid digestion and subsequent pressure measurement using the method of Muller & Gastner 1979.
Process: Powdered sample is digested with acid in a sealed pressure chamber and the change in pressure due to the evolution of carbon dioxide is measured. A calibration graph equates this measured pressure to carbonate percentage. Carbonate percentage for gravel fractions are estimated through visual inspection.
Uses: Calcium carbonate is the major biogenic component of sediments in many marine areas and indicates relative biogenic or terrigenous sediment deposition.
Multi Sensor Core Logging (MSCL)
Description: A non-destructive analytical process measuring density (through gamma attenuation), magnetic susceptibility, and P-wave velocity properties of core samples. The unit incorporates a high resolution imaging system.
Process: A conveyor system carries each core section past the required sensors which scan the core as it passes.The conveyor is driven by a stepper motor which can position a core to an accuracy of better than 0.5 millimetres. The computer controlling the conveyor also controls the sensors, so that all the data are automatically correlated. The computer also measures the length of each core section. This allows the sections to follow sequentially, producing an unbroken stream of data. This system saves time by ensuring that the core sections continuously follow each other. This makes core logging a continuous, automated and uninterrupted process. The MSCL can handle core sections between 50 and 150 millimetres in diameter and 1.5m long and can sample at intervals of 1 millimetre or greater.
Uses: Core samples are collected on land or at sea by the hydrocarbon, mining and construction industries and additionally by the military. In research institutes they are now an essential part of climate studies. The cores come as exposed hard rock samples or as soft sediment encased in plastic sleeves. Correctly analysed, they can yield crucial information about the properties of rock or sedimentary strata. The hydrocarbon industry, for example, needs accurate data on the porosity, grain size, type and composition of the geology they are investigating, whereas the construction industry and the military may be interested in geotechnical properties such as p-wave velocities, density and water content.
Decription: The Hylogging systems use spectrometers which measure the reflectance spectra over a range of wavelengths; from Visible-Near Infrared (VNIR) through Short Wave Infrared (SWIR) to Thermal Infrared (TIR).
Process: The samples are retrieved from storage; they are then sorted by core measurement and samples are place in black trays; cores are fully depth logged (converted into meters where required) and recorded in excel, then photographed before being stacked in processing order with start and end depths details in each tray for the operator.
The core trays are then prepared for shipment to a HyLogging facility for analysis. Once samples are returned to Geoscience Australia, they are unpacked, returned to their original core trays and placed back into storage. The preliminary data is checked and cleaned (blanking out blocks); the depths are then checked against the core.
Uses: Based on reflectance spectroscopy the HyLogger provides mineralogical data using rapid non-destructive sampling of drill core, chips and powder. High resolution line scanning is produced as part of the operation.
Description: Core splitting. We also have sampling kits available for use.
Process: The Geotek core splitter can accommodate cores up to 150 centimetres in length. The Geotek is equipped with two vibratory disc cutters and two hooked knife blades, a smooth longitudinal cut can be made through polyvinyl chloride (PVC) core liners. The core material itself is split using the integrated cheese wire which follows the blades. These splitting techniques combined, produce negligible amounts of liner swarf which minimises contamination of the samples, and leaves perfectly undisturbed core surfaces.
Surface Area Analyser
Description: Surface area and total pore volume can be analysed using gas saturation.
Process: The Nova 2200e is designed to perform analyses on two samples at a time, with the capability to prepare eight samples for analysis whilst operating. The Nova 2200e is both PC and keyboard driven and can be left unattended during operation. After a heating and vacuum/gas cleaning process, the sample is brought to a constant temperature by means of an external bath. Then, small amounts of a gas (the adsorbate) are admitted in steps into the evacuated sample chamber. Gas molecules that adhere to the surface of the solid (adsorbent) are said to be adsorbed and tend to form a thin layer that covers the entire adsorbent surface. Based on the well known Brunauer, Emmett and Teller theory, one can estimate the number of molecules required to cover the adsorbent surface with a monolayer of adsorbed molecules, nm. Multiplying nm by the cross-sectional area of an adsorbate molecule yields the sample's surface area.
We have a range of microscopes available for use, including field, compound and stereo microscopes. Please discuss your requirements with the laboratory manager.
The PalSed Laboratory has a number of digital cameras, services and equipment available including:
- Digital SLR with various lenses - available for use through our loans register
- digital compact - available for use through our loans register
- microscopy - our microscopes are available to use within the laboratory. They are fitted with Leica and Olympus microscope specific digital cameras operated through a dedicated PC
- we have trained operators to perform photographic work - Please discuss your requirements with the laboratory manager
- 35 millimetre, strip and medical high resolution slide scanners
- munsell colour charts
- image manipulation software
- image analysis software
- photographic plate preparations for scientific publications.
Uses: Along with calcium carbonate, silica is the main component of biogenic sediments. Silica levels in marine sediments can indicate various levels of ocean productivity.
Carbonate Removal for TOC and Isotope Preparation
Description: The RockEval analysis of samples for the determination of Total Organic Carbon (TOC) and Isotope analysis requires that samples first be treated to remove all carbonate.
Process: The carbonate component of geological samples primarily in the form of calcium carbonate (CaCO3) is easily removed by digestion in hydrochloric acid (HCl). The sample is then neutralised by repeated dilution, freeze dried, powdered and finally analysed.
Description: This technique is used to estimate the age of organic materials by measuring the decay of carbon-14.
Process: There are various methods for sample preparation depending on sample type.
- Soils, sediment, peat (1): This treatment removes all but the least mobile organic fraction, leaving the "humin" fraction only (preferred for peat/wood/organic matter samples).
- Soils, sediment, peat (2): This method removes only inorganic carbon and absorbed CO2, leaving the entire organic carbon fraction (should only be used on bulk sediment samples).
- Shell and other carbonates.
Description: Kerogen is the insoluble organic component of rocks. It is often necessary to isolate the kerogen from a rock sample prior to organic geochemical analyses.
Process: Geoscience Australia's Laboratories use physical and chemical processes to isolate pure kerogen. This involves preparation of a rock powder, solvent extraction, acid digestion phases to remove naturally occurring and neo-formed minerals. Followed by density separation and final treatments to remove residual reagents from the sample. This process is conducted jointly by the Organic Geochemistry Laboratory and the Palaeontology & Sedimentology Laboratory. Processing time for this procedure is usually about two weeks.
Uses: Kerogen is subsequently analysed for Total Organic Carbon (TOC), kinetics and biomarker studies to assist hydrocarbon exploration.
Sample splitting, crushing and milling
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 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.
For samples requiring both inorganic and organic analysis a solvent wash of the grinding vessels is carried out. These samples are usually hand specimens and will be handled in a way to avoid all organic contamination.
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).
Bulk Density & specific determination
Description: Density is determined using the Archimedes Principle that states that any object immersed in a fluid, is buoyed up by a force that is equal to the weight of the fluid displaced by the object. The weight of the fluid displaced is directly proportional to the volume of displaced fluid and therefore the volume of the object submerged.
Process: Using a Density determination balance the sample is weighed dry and then the sample is submerged in water. The weight of the fluid displaced is weighed. The balance will then determine the density of sample.
Moisture content & total suspended solids analysis
Description: Samples are weighed, dried and then re-weighed again to determine moisture content. Fully evaporating a water sample and weighing the dry residue gives total suspended solid content.
Core plugging, slicing and polishing preparation
Description: Samples are prepared to requirement for the following analysis:
- Magnetic Remanence - >1cm cube or 25mm plug
- Density - >1cm cube or 25mm plug
- Magnetic Susceptibility - >1cm cube
- Thermal Conductivity - 25mm polished disc
- Porosity (mercury injection method) - >1cm cube
Process for plugs: With the use of a rock saw and drill press, core plug are cut into cylinders of 25mm diameter.These core plugs are sliced using the Isomet 5000 precision saw which is designed to make precise cuts of a wide variety of materials. This saw can be programmed to perform multiple cuts automatically with a 2 micron tolerance. It has the functionality to cut from a programmable menu and has sectioning applications from stainless steel to ceramics. The core plugs can be polished if required.
Process for cubes: With the use of a slabbing and lapidary saw, samples are cut into >1cm cubes. Further precision can be obtained using the precision saw.
Description: Thermal conductivity in the Anter 2022 meter is measured by the ATSM E1530 guarded heat flow method. A sample of the material is held under a uniform compressive load between two polished surfaces, each controlled at a different temperature. The lower surface is part of a calibrated heat flow transducer. The heat flows from the upper surface, through the sample, to the lower surface, establishing an axial temperature gradient in the stack. After reaching thermal equilibrium, the temperature difference across the sample is measured along with the output from the heat flow transducer. These values and the sample thickness are then used to calculate the thermal conductivity.
Process: The samples are prepared using the Core plugging, Slicing and Polishing method above and saturated in a vacuum chamber, then analysed using the Anter Unitherm 2022 thermal conductivity meter.
Thin Section Analysis
Description: Currently, thin section preparations are outsourced. Please contact PalSed laboratory to arrange this service.
Process: Thin Section
- General Paleo
- petrographic - polished or cover slipped
- staining- For carbonates and client specified.