Journal article

Extreme Silver Isotope Variation in Orogenic Gold Systems Implies Multistaged Metal Remobilization During Ore Genesis

Christopher R Voisey, Andrew G Tomkins, Michael Brauns, Gerhard Bruegmann, Roland Maas

ECONOMIC GEOLOGY | SOC ECONOMIC GEOLOGISTS, INC | Published : 2019

Abstract

We report the frst Ag isotope data for the Paleozoic orogenic Au deposits in the Victorian Goldfelds, southeast Australia, a world-class province with a historic production of 2,400 tonnes of Au. Despite their relatively uniform geology—similar host-rock types, age, mineralization style—deposits in Victoria show a wide range in 107Ag/109Ag ratios in native Au (e107Ag -6.6 to +8.3, relative to the NIST SRM 978a Ag standard), comparable to the entire previously known terrestrial range (-9.4 to +5.3). The data show no correlation with mineralization age or host-rock composition, and there is no obvious isotopic link to established "mantle" or "crustal" Ag isotope values, implying that source ro..

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Grants

Awarded by ARC Linkage grant


Funding Acknowledgements

The authors wish to thank Braden Verity, Simon Hitchman, Nathan Phillips, and the geologic team at the Fosterville gold mine for their assistance and advice. We would also like to thank Rob Duncan and the Geological Survey of Victoria for their partnership in this endeavor. We would like to show our appreciation towards Museum Victoria for their kind donation of samples from their collections, which made this study possible. Finally, thanks to Dr. Nicholas Hunter for providing stimulating discussion regarding sample textures. This project was funded by the ARC Linkage grant (LP150100717).