Paleo-hydrothermal fluid flow in the Kalgoorlie Terrane, Western Australia

This thesis aims to understand the source of auriferous fluids and ore forming mechanisms in the Golden Mile-Mt. Charlotte deposits (2137 t Au) and Kundana gold camp (130 t Au). The multiple S isotope signature of pyrite in the Golden Mile-Mt. Charlotte deposits record mixing among three components: mantle, seawater and elemental S. Linear Mixed Effects Modelling of trace elements revealed difference in contents of As, Au and Te in pyrite from different mineral assemblages. In the Kundana gold camp, gold mineralization is associated with pyrrhotite, arsenopyrite and variable sphalerite in veins and altered wall rocks. Pyrrhotite ± arsenopyrite are dominant in ore grade veins and transition to pyrite ± anhydrite barren domains. The former underwent reducing conditions during mineralization, whereas the latter was deposited under oxidizing conditions. Geochemical evidence suggests that pyrrhotite rich veins acquired S from shales that reacted with hydrothermal fluids, thus promoting mineralization.