Silver sulfotellurides from volcanic-hosted massive sulfide deposits in the Southern Urals

This paper addresses Ag-sulfotellurides occurring in volcanic-hosted massive sulfide deposits of the Southern Urals. Cervelleite-like minerals were identified in ores from the Gayskoe, Yaman-Kasy, Severo-Uvaryazhskoe, Tash-Tau, and Babaryk deposits, where they occur in ores containing chalcopyrite, galena, sphalerite, tennantite ± bornite. Other Ag- and Te-bearing minerals (electrum, hessite, stromeyerite and Ag-bearing chalcocite) are present in the association. A benleonardite-like mineral associated with sylvanite and native tellurium was found as a metastable phase in paleohydrothermal tubes relics from the Yaman-Kasy deposit. Formation of the sulfotellurides indicates relative low fTe2 in the hydrothermal systems, insufficient for formation of most S-free tellurides. The significant Cu enrichment in cervelleite relates to the association with bornite. Broad variations in composition and physical properties of cervelleite-like sulfotellurides allow the supposition of the presence of several, as yet unnamed mineral species, which can be distinguished by Cu contents, Te/S ratios, and presumably by crystal structure.