The origin of sulfur and gold in Archean orogenic gold systems should provide significant insights into the dynamics of fluid movement in the crust of the early Earth, but is poorly constrained and highly debated. Our natural laboratory to address this knowledge gap is the metal-endowed Yilgarn Craton (Western Australia), where we measured the multiple sulfur isotope signatures of representative sulfide-bearing auriferous samples from 24 Archean orogenic gold deposits varying in size and geological setting. Utilizing chemically conservative mass-independent fractionated sulfur (MIF-S) isotope signatures, we fingerprinted a major source of sulfur in these deposits. Contrary to previous studies, our data show that they display MIF-S isotope anomalies, with Δ33S values ranging from –1.18‰ to +2.04‰; most of the studied deposits show a sulfur signature that is consistent with a crustally derived source. Unlike smaller deposits, which may form with sulfur derived from a single sedimentary sulfur source, therefore providing a coherent Archean atmospheric signal in their Δ33S-Δ36S slope (~0.9–1.5), the formation of giant deposits may require sourcing from a wider range of sulfur reservoirs and using different processes, as reflected in their apparently random Δ33S-Δ36S slopes.
Atmospheric sulfur in the orogenic gold deposits of the Archean Yilgarn Craton, Australia
Marco L. Fiorentini
Crystal K. LaFlamme
Vikraman Selvaraja, Stefano Caruso, Marco L. Fiorentini, Crystal K. LaFlamme, Thi-Hao Bui; Atmospheric sulfur in the orogenic gold deposits of the Archean Yilgarn Craton, Australia. Geology 2017 doi: 10.1130/G39018.1
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