Typecasting prospective Au-bearing sedimentary lithologies using sedimentary geochemistry and Nd isotopes in poorly exposed Proterozoic basins of the Tanami region, Northern Australia

Abstract

The development of a regional stratigraphy in Palaeoproterozoic basins within the Tanami region, Northern Australia has been hindered by the difficulty of discriminating sedimentary units and facies across this isolated and poorly exposed basin. A regional stratigraphy is important as it provides constraints on sedimentary basin evolution and assists in gold exploration. Gold is known to be more concentrated in certain rock formations. Based on Nd isotopes and whole-rock geochemistry, five main sedimentary events have been identified in the Tanami region. Some sedimentary units were derived from homogeneous local sources whereas others contain evidence of a well-mixed fine-grained remote provenance. Within the basins, major gold-bearing lithologies are characterised by mafic source indicators: (1) high Cr/Th ratios; (2) low Th/Sc ratios; (3) low (La/Yb)PAAS ratios relative to Post-Archaean Average Shale (Taylor and McLennan 1985); (4) Eu anomalies equal to ~1 and, (5) distinctive ranges in initial Nd values. Potential future exploration target areas have been identified in the Tanami region at the Cashel and Sunline prospects using these geochemical parameters.