Distribution and mineralogical association of Au at the Kanmantoo Cu-Au deposit

Abstract

South Australia’s Kanmantoo Cu-Au deposit is currently operated by Hillgrove Resources and has an extended history of exploration and production dating back to 1846. However, there is little consensus on the paragenesis and structural controls of the deposit.

Empirical work specifically on Au mineralogy and paragenesis has been completed. To investigate the mineralogical and geochemical associations between Au and host mineralogy, drill core samples, grab samples and ore concentrates and tailings have been collected from the East Kavanagh, Central Kavanagh, West Kavanagh, Spitfire and Nugent ore lodes.

Petrographic analysis, Mineral Insights Goldsniffer analysis, secondary electron microscopy, mineral liberation analysis (SEM-MLA) and Laser Ablation (LA-ICP-MS) analysis observed and recorded evidence for four textural settings of Au. Two stages of Au development are proposed: early Au (associated with the main economic Cu-bearing hydrothermal fluids) and late Au (associated with retrograde Bi-rich hydrothermal fluids).

Variations observed in major and trace element composition reflect changing input from a thermally-anomalous hydrothermal fluid source. The stability field for Au nanoparticles and the rarity of precipitated visible Au supports a late-peak to post-peak metamorphic origin.

This study has implications about how Au can be recovered within the Kanmantoo Cu-Au deposit. The mineralogy and geochemical characteristics of Au at the Kanmantoo Cu-Au deposit can also be utilised as an exploration pathfinder within the greater Adelaide fold belt and the Delamarian-affected terrains at other exploration provinces within the Adelaide fold belt.