Petrogenesis of the Kalka, Ewarara and Gosse Pile layered intrusions, Musgrave Province, South Australia, and implications for magmatic sulfide prospectivity

Abstract

Abstract The Musgrave Province of central Australia was the focus of long-lived mantle upwelling that produced large volumes of magnesian basaltic to tholeiitic magma and their felsic derivatives. The Musgrave Province contains one of the greatest concentrations of mafic–ultramafic layered intrusions globally, grouped as the Giles intrusions. In the present paper, we study the magmatic ore potential of the Kalka, Gosse Pile and Ewarara layered intrusions located in South Australia. Ewarara and Gosse Pile appear to have relatively low potential for platnium-group element (PGE) reefs and magmatic Ni–Cu, based on lack of evident metal enrichment and the absence of a mafic–ultramafic transition zone that hosts most PGE reefs globally. However, mafic–ultramafic pipes within the intrusions that could have higher ore potential have not been studied by us. At Kalka, the mafic–ultramafic transition interval is exposed, rendering this intrusion potentially more prospective for PGE reefs. However, based on the available data, this zone appears to be barren. Instead, there are signs of PGE enrichment and metal ratio variation in the magnetite-bearing upper portion of the intrusion suggestive of undiscovered PGE reefs. This interpretation is consistent with subtle Cu–Pd enrichment of soils adjacent to the upper portion of the intrusion. KEY POINTS First assessment of magmatic ore potential of Kalka, Ewarara and Gosse Pile layered intrusions in South Australia. Kalka shows signs of PGE enrichment in upper, magnetite-bearing portion of intrusion, suggesting enhanced potential for a PGE reef. Ewarara and Gosse Pile appear to be less prospective for PGE–Ni–Cu, but picrite pipes remain unstudied.