Integration of multiple sulfur isotopes with structural analysis unveils the evolution of ore fluids and source of sulfur at the Kanowna Belle Archean orogenic gold deposit, Yilgarn Craton, Western Australia

The Kanowna Belle deposit is a world-class Archean orogenic gold system that witnessed multiple fluid episodes over a protracted deformation history. The hydrothermal fluid circulation episodes at the Kanowna Belle deposit initiated with the precipitation of early gold-bearing carbonate-famatinite-pyrite-telluride-electrum veins (V1a). These early veins were subsequently folded during a NE-SW shortening event (D1b(KB)) that led to the development of sericite-chlorite-pyrite stringers (V1b) and foliation (S1(KB)) dated at c. 2658 +/- 9 Ma (U-Pb, xenotime). D1b(KB) structures are overprinted by quartz-carbonate-sericite-pyrite-gold veins (V2) controlled by the reverse faulting formed as a result of N-S shortening during D2(KB.) A subsequent deformation event (D3a(KB)) is related to sinistral shearing produced under ENE-WSW shortening and associated with the development of the Troy lodes and deposition of quartz-pyrite-sericite-gold veins (V3a) dated at c. 2628 +/- 9 Ma (U-Pb, xenotime). The application of multiple sulfur isotope analyses of sulfides related to the different mineralization events resolves the hydrothermal fluid isotopic evolution through time. Despite the ore mineralogy differences of the V1, V2, and V3 vein sets, their associated sulfides yield small positive increment S-33 (+ 0.1 to + 0.4 parts per thousand; n = 231) values with two outliers ( increment S-33 = + 0.5 parts per thousand and + 0.6 parts per thousand) across all lithology types. The constant value of MIF-S through the three temporally different gold mineralization episodes implies that sulfur was derived from a single homogenized source of sulfur distal from the deposition site, irrespective of the Au endowment. The consistent small positive increment S-33 sulfur isotope signature may support that the Archean orogenic gold system sourced sulfur and possibly hydrothermal fluids from a mantle/magmatic dominated source that homogenized with crustal sulfur at depth prior to gold deposition.

Automated summary

The Kanowna Belle deposit is a world-class Archean orogenic gold system that experienced multiple fluid episodes over a protracted deformation history. Despite differences in ore mineralogy, sulfur isotope analysis of sulfides associated with different mineralization events showed a consistent small positive increment, suggesting sulfur sourced from a mantle/magmatic dominated source.