SHRIMP S-isotope evidence for fluid mixing during gold mineralization in a slate-belt gold deposit (Hill End, New South Wales, Australia)

Abstract

Sensitive high-resolution ion microprobe (SHRIMP) sulfur isotope data show that pyrrhotite, pyrite, galena and chalcopyrite in syntectonic auriferous quartz veins at the Hill End goldfield are characterized by two populations, with δ 34S fluid-values of ∼ +7 and ∼0%. These two populations are accounted for by fluid mixing involving two sources of sulfur during evolution of the vein systems. A local sulfur source and reduced fluids derived from trough-fill Siluro-Devonian sedimentary and volcano-sedimentary sequences are responsible for the first two gold-bearing events, whereas a more oxidized fluid and a sulfur source from turbidites and volcanics in deeper parts of the crustal sequences appear responsible for gold deposition late in the second gold-forming event and are the dominant influences in the final gold-forming stage. For fine-grained mixtures, where mineral separation is difficult, the SHRIMP analyses are particularly useful for tracing detailed δ 34S variations of sulfides precipitated in different paragenetic stages.