Hydrothermal footprints around magmatic nickel-sulfide deposits: a case study at the Miitel deposit, Yilgarn craton, Western Australia

Magmatic nickel-sulfide deposits are highly valuable but extremely challenging exploration targets, lacking the distinctive geochemical haloes that allow small targets to be identified from sparse drilling. The remobilization of metals during post-deposition hydrothermal alteration has the potential to result in large haloes, whose recognition could increase exploration success rates. Using the West Australian Miitel komatiite-hosted nickel-sulfide deposit as case study, we investigate the nature and 3D geometry of the footprint created by the remobilization of base metals, gold and platinum group elements into the rocks surrounding the deposit. At Miitel, anomalous metal enrichment in the country rocks surrounding, the ore bodies occurs in association with the presence of sulfarsenides, which are formed during the circulation of arsenic-rich hydrothermal fluids. Nickel sulfarsenides, such as gersdorfitte, are concentrated in small sulfide veinlets within the Lunnon basalt footwall, in close proximity to the contact with the overlying komatiite. This NiAs enrichment is associated with elevated concentrations in PGEs, indicating that the nickel sulfides from the Miitel ore bodies are the source of the remobilized Ni. This cryptic NiAs signature, which has been detected using pXRF on drill core up to 200 meters away from the mineralization, could represent a good mineralization vector.