Composition and conditions of formation of gold-telluride mineralization in the Tissa-Sarkhoi gold-bearing province (East Sayan)

The structure and petrologic composition of new gold-ore provinces in southeastern East Sayan (Tissa-Sarkhoi cluster) are considered. Several morphogenetic types of gold mineralization have been established: quartz veins with beresitization zones, veinlet-disseminated ores in granitoids, and listwaenitization and sulfidation zones in effusions of the Sarkhoi Group and intrusive rocks of the Late Riphean Khorin-Gol complex. According to geochronological dates and some mineralogical and geochemical features, the gold mineralization is close in age to these Precambrian island-arc complexes. Parageneses of two stages of ore formation have been recognized: early high-temperature (250-460 degrees C) gold-pyrite and late low-temperature (110-280 degrees C) gold-telluride. The latter mineralization is widespread and is represented by tellurides of Au, Ag, Pb, Bi, and Ni - petzite, calaverite, hessite, tellurobismuthite, altaite, and melonite. Native gold associated with these tellurides is characterized by a fineness of 750-900 ppm. The intimate temporal and spatial relationships of the gold mineralization with island-arc volcanoplutonic complexes and the wide occurrence of its veinlet-disseminated type suggest that this is porphyry gold mineralization related to the Late Riphean-Vendian island-arc magmatism.