National- and regional-scale surface geochemistry data can provide valuable information about mineral prospectivity and geology of a country or region, and allow for informed decision-making around environmental management. Whilst a number of regional geochemistry surveys of varying heritage exist across Australia, they currently stand as individual surveys with limited ability to utilise with other surveys. To increase our understanding of the surface of Australia and aid in determining areas of mineral prospectivity, a decision was made to level each of these individual surveys and thus create a unified levelled geochemical baseline of Australia.
Levelling of regional surveys can remove the analytically-introduced variation; however, the majority of the survey areas are spatially isolated from one another. Fortunately, Australia has a national-scale survey, the National Geochemical Survey of Australia (NGSA), which acts as a backbone interlinking each of the higher density regional surveys. A pilot project released in 2020, utilised this approach to create a levelled geochemical baseline for the northern Australia. The pilot project highlighted several limitations, particularly the small number of chemical elements analysed for in historical regional surveys. Another limitation was the common absence of analytical data for reference materials meaning the accuracy and/or precision of these surveys is unknown.
To address these shortcomings ~9,000 samples from historical regional surveys from around Australia were reanalysed by one laboratory using modern analytical techniques to produce a comprehensive suite of analytes. The results for these surveys were then levelled with recent regional geochemistry surveys (e.g., southern Thomson regional geochemistry survey, Northern Australia Geochemical Survey) and the NGSA, to produce a national geochemical baseline to which future geochemical surveys can be added.
Initial examination of this new levelled Australia-wide dataset has identified new areas of interest for rare earth element enrichment. These areas of interest were not present in the original dataset due to the limitations of the original analytical techniques. The new data allows for examination of the mechanisms and source of these areas of enrichment. These initial findings demonstrate the power of bringing Australia’s historic archive of samples up to modern standards, and the utility of levelling them to create a seamless product.
Abstract presented at the 30th International Applied Geochemistry Symposium 2024 (IAGS 2024)
