Mineral exploration in Australia currently faces the challenge of declining discovery rates despite continued exploration investment. The UNCOVER roadmap, produced by stakeholders from industry, government and academia, has highlighted the need for discovering mineral systems in areas under cover. This is where prospective basement is covered by regolith including transported sediments, challenging many traditional exploration methods that rely on outcrop sampling. Groundwater-rock interaction in the subsurface has the potential to impart both geochemical and isotopic characteristics to water that may persist over time and space (down the groundwater flow path). Geoscience Australia’s minerals hydrogeochemistry project, part of the Exploring for the Future Programme, aims to use groundwater chemistry to better understand the bedrock-regolith system and develop new methods for recognising mineral system footprints within and below cover.
This work will be conducted in selected areas to identify the best chemical indicators to use with various mineral systems. Initially targeting areas of shallow cover near known mineral deposits and in barren areas, the project will then extend into deeper under cover regions to develop diagnostic tools. Focus areas will be up to three 1:250,000 scale map sheets, targeting existing groundwater bores that ensure good spatial coverage. The Tennant Creek and McArthur Basin regions have been identified as initial focus areas.
In addition to the standard measurements such as bulk parameters, major anions, major cations and trace elements, selected groundwater samples will be analysed for a comprehensive suite of isotopes (e.g. Sr, Cl, I, C, O, S, H, Pb, Rn), organics and hydrocarbons, and dissolved gases. All data will be released to the public. If suitable chemical indicators can be recognised and mapped spatially, hydrogeochemistry can become a successful, more widely used exploration tool in Australia with the capability to identify and target parts of mineral systems undercover.