Regolith and associated geochemical and biogeochemical expression of buried copper-gold mineralisation at the Hillside Prospect, Yorke Peninsula

Abstract

Significant Cu-Au mineralisation with some high grade U has been discovered by recent drilling by Rex Minerals Ltd within its Hillside Project, Yorke Peninsula, South Australia. Drilling so far suggests that mineralisation has characteristics typical of Iron-Oxide Copper Gold (IOCG) mineralisation, which provide large economic resources for South Australia. Much of Australia is covered by extensive regolith, much of which is equivalent to Hillside. Vegetation, soil and calcrete sampling was conducted to characterise the regolith expression of the buried Cu-Au mineralisation in the ‘Hillside’ area. More specifically this included: 1. characterisation of geochemical and biogeochemical signatures with moderate transported cover thickness; 2. develop a recommended soil geochemical exploration approach for the project area, and potentially equivalent settings; 3. characterisation of soil geochemistry across the mineralised zones and non-mineralised substrate with increasing thicknesses of sedimentary cover; and, 4. interpretation of recommended soil geochemistry exploration results within the project area, including their possible implications for further mineral exploration. The suite of elements chosen for detailed presentation is based on their local abundance and expression of known mineralisation. These include; mineralisation commodity elements (Au, Cu, U), secondary mineral trace element host elements (Al, Fe, Ca), and pathfinder and mineralisation accessory elements (Ce, Co, Dy, Li, Tl and V). This study highlights the potential of geochemical and biogeochemical sampling to characterise regolith expression of the buried Cu-Au mineralisation. The results from this study have major implications for mineral exploration in landscapes dominated by aeolian cover, such as at Hillside. This study supports the use of vegetation, calcrete and soil as a sampling medium in regional, prospect and tenement-scale mineral exploration programs. This study has also emphasised the importance of understanding the landscape setting and using orientation studies. These vital elements of the research process enable suitable sampling medium to be recognised, making an effective geochemical and biogeochemical sampling program for applications in mineral exploration.