Defining early stages of IOCG systems: evidence from iron oxides in the outer shell of the Olympic Dam deposit, South Australia

The IOCG deposit at Olympic Dam (South Australia) is hosted within the Roxby Downs Granite, which displays a weakly mineralised contact to the orebody (hereafter ‘outer shell’). In a mineralogical-geochemical characterisation of Fe-oxides from the outer shell, we show silician magnetite (Si-magnetite) and HFSE-bearing hematite define the early stages of alkali-calcic alteration. This association forms in the presence of hydrothermal K-feldspar...