Tectonothermal implications of laser40Ar/39Ar ages of sulphide-bearing veins and their host rocks in the Willyama Supergroup, South Australia

Abstract

40Ar/39Ar age spectra of mica separates from sulphide-bearing veins and associated metasedimentary whole-rock samples in the Olary Block, South Australia, indicate widespread emplacement of epigenetic mineralisation in Willyama Supergroup metasediments between 450 and 480 Ma, during the Delamerian Orogeny. This age range complements petrographic, structural and geochemical studies, which indicate that periodic tectonic disturbances occurred in the Olary Block since the Mid-Proterozoic, triggering the intermittent development of hydrothermal fluid circulation and infiltration into reactivated faults and shear zones over time scales of more than 1000 Ma.