Characterising the regolith profile of the E41 Gold Deposit, Cowal, NSW : implications for orepProcessing and mineral exploration

Endeavour 41 is a structurally controlled low-sulfidation epithermal gold deposit in the Cowal district of central New South Wales. This deposit is distinguished by an extensive regolith profile that hosts several highly enriched supergene gold mineralisation zones. Considering that over 80% of Australia is covered by regolith, gaining a comprehensive understanding of the structure, mineralogy, and gold deportment within the Endeavour 41regolith profile holds substantial significance. These knowledge plays significant role, shaping mine planning and ore processing strategies.
The regolith at Endeavour 41 comprises five distinct facies, including four residual and one transported regolith facies. Beneath the altered mafic monzonite and volcano-sedimentary sequences, are overlaid by saprock (10 – 30 m thick), representing the least developed portion of the regolith profile. Progressing in depth, lower ferruginous saprolite was encountered (10 – 75 m thick), which is characterised by a large portion of Fe-oxides and limonites. The upper kaolinitic saprolite (10 – 25 m thick) represents the most advanced stage of regolith developed, with primary minerals extensively weathered and replaced by kaolinite. A thin layer of indurated silcrete (1 – 3 m) marks the boundary between the residual and transported regolith. The entire deposit is covered by a 5 – 10 meters thick layer of lacustrine sediments, originating from ephemeral Lake Cowal to the east of the deposit.
Detailed mineralogical, geochemical, and spectral analysis of the regolith have unveiled high?grade gold mineralisation (exceeding 20 g/t) in the regolith profile. Gold is hosted as free gold and electrum grains, closely associated with goethite in limonite aggregates, and as lattice?bound gold within iron-oxides, indicative of pseudomorphs derived from primary pyrite alteration to goethite and hematite. The prevalence of the lattice-bound gold endorses significant supergene enrichment across the deposit, due to the significant development of iron oxides across the regolith profile.
Based on the whole rock geochemical analysis, distinct mineral weathering boundaries and geochemical profiles for each regolith facies have been identified. of an alternative proxy technique for gathering geochemical data.
Partial least squares regression using Fourier transform infrared (FTIR) data was employed to predict elemental geochemistry data with a remarkable degree of accuracy. Notably, major elements such as iron, aluminium, and calcium, exhibited exceptional prediction success (with R² of 97.1, 98.28 and 96.21, respectively). This ground-breaking finding holds the potential to directly predict whole rock elemental geochemistry data from FTIR spectral data, offering a more cost-effective, efficient, and safer approach.