1 Influence of Structural Setting on Sulfur Isotopes in Archean Orogenic Gold Deposits, Eastern Goldfields Province, Yilgarn, Western Australia Hodkiewicz, P. F.1,2*, Groves, D. I.1, Davidson, G. J.3, Weinberg, R. F.4, and Hagemann, S. G.1 1Centre for Exploration Targeting, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia 2SRK Consulting, 10 Richardson Street, West Perth, WA 6005 Australia 3School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, TAS 7001 Australia 4School of Geosciences, Monash University, Building 28, Clayton, VIC 3800 *Corresponding author and contacts: • Email –
[email protected] • Tel: +61-8-9288-2000 • Fax: +61-8-9288-2001 2 Abstract The published mean δ34S values of ore-related pyrites from orogenic gold deposits of the Eastern Goldfields Province, Yilgarn Craton lie between -4‰ and +4‰. As for orogenic gold deposits worldwide, most deposits have positive means and a restricted range of δ34S values, but some have negative means and wider ranges of δ34S values. Wall-rock carbonation and back-mixing of similar- source fluids with different fluid pathways can explain some of the more negative δ34S signatures. However, structural setting appears to be the most important factor controlling ore-fluid oxidation state and hence the distribution of δ34S values in gold-related pyrites. Shear-hosted deposits appear to have experienced fluid-dominated processes such as phase separation, whereas stockwork, vein-hosted or disseminated deposits formed under conditions of greater rock buffering. At Victory-Defiance, in particular, negative δ34S values are more common in gently-dipping dilational structures, compared to more compressional steeply-dipping structures.