V014-0009
Shale geochemistry as an exploration tool for base-metals (Zn-Pb-Ag ± Cu), critical minerals and hydrocarbons in northern Australia

Wednesday, 9 December 2020
Poster
Amber Jarrett1, David C Champion1, Jane P Thorne2, David Huston3, Evgeniy Bastrakov1, Alan S Collins4, Darwinaji Subarkah5, Timothy J Munson6 and Samuel C Spinks7, (1)Geoscience Australia, Canberra, Australia, (2)Geoscience Australia, Symonston, Australia, (3)Geoscience Australia, Canberra, ACT, Australia, (4)University of Adelaide, Adelaide, Australia, (5)Adelaide University, Adilaide, Australia, (6)Northern Territory Geological Survey, Darwin, Australia, (7)CSIRO Mineral Resources Flagship, Perth, Australia
Abstract:
Northern Australia contains extensive Proterozoic-aged sedimentary basins with potential for mineral, energy and groundwater resources. A corridor of Zn-Pb-Ag mineralisation spans across the region. These deposits were predominantly identified from surface gossans. These basins have been recognised as having potential for critical minerals associated with base metal mineralisation.

Exploration for hydrocarbons and base metals, although perceived to have very different exploration models, share a number of important similarities and key parameters. Foremost amongst these is shale geochemistry since the same reduced, organic-rich shales are both a hydrocarbon source rock and a depositional site for base metal mineralisation. Furthermore, anoxic and euxinic (anoxic with free hydrogen sulfide, H2S) water column and sediments are important for both the preservation of organic matter and as a H2S reservoir needed for precipitation of ore minerals after reaction with oxic metalliferous brines.

Here we present the results of new data generated from legacy drill cores to characterise the organic and inorganic geochemistry, and mineralogy of Proterozoic-aged basins in northern Australia. The results reveal many units in the Lawn Hill Platform, South Nicholson Basin and greater McArthur Basin contain organic-rich rocks that are favourable as both base metal depositional sites and hydrocarbon source rocks. Inorganic geochemistry results demonstrate a range of paleoredox conditions, from predominantly anoxic, ferruginous conditions with deviations, to sub-oxic and euxinic conditions, further bolstering the region’s prospectivity.

The precompetitive data generated in this study highlight the utility of shared geochemical datasets for resource exploration in the region. More broadly, this study improves our understanding of the mineral and hydrocarbon potential across northern Australia, supporting resource decision-making and investment.

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