Abstract

The Vulcan prospect is a newly discovered Cu-Au prospect located within the eastern Gawler craton, South Australia. The prospect is entirely subsurface and defined by a geophysical anomaly intersected by diamond drilling. Eight drill holes have all intersected hematite-rich alteration and Cu-Au mineralization within a variety of breccia types ranging from those composed entirely of hydrothermal hematite + sericite + chlorite to those dominated by altered rock in which clasts of protolith rock are preserved. The highest-grade zones of mineralization at Vulcan occur within hematite-dominant breccias. Molybdenite within hematite-rich brecciated granite samples has been dated via the Re-Os method and yields a crystallization age of 1586 ± 8 Ma (including decay constant uncertainties). SHRIMP zircon U-Pb analyses show that a sample of hematite-sericite-chlorite–altered and brecciated granite was emplaced at 1743 ± 7 Ma. The new data from Vulcan confirm that hematite breccia-related Cu-Au mineralization formed during a widespread alteration and mineralization event between ca. 1600 and 1570 Ma, broadly coeval with the voluminous felsic large igneous province of the Gawler Range Volcanics/Hiltaba Suite, and are consistent with most interpretations of the geology of the Olympic Cu-Au province.

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