New Type of Gold-Bearing Mineralization at the Ozernovskoe Au–Te–Se Epithermal Deposit (Central Kamchatka, Russia)

The ores of the Ozernovskoe Au–Te–Se epithermal volcanic deposit occur in linear zones of secondary quartzites in the Neogene volcanic rocks and include linear stockworks and pipes of quartz hydrothermal breccias with disseminated ore minerals: sulfides, tellurides, and selenides. The studied gold mineralization of new type is found in the upper horizon of the deposit. The major gold mineral maletoyvayamite Au₃Se₄Te₆ forms small inclusions in Se-bearing native tellurium together with microinclusions of other (typically, also rare) minerals: bambollaite Cu_{1 – x}(Se,S,Te)₂ and fahlores of the goldfieldite and ústalečite subgroups. This mineral complex could form in the upper part of a boiling hydrothermal system as a result of mixing of an ascending flow of heterogeneous aqueous–vapor fluid with oxygen-enriched subsurface waters and oxidation of its reduced S, Se, and Te forms. The primary ore minerals are typically partly replaced by several generations of supergene minerals: from native selenium and Au–Ag selenides of the early stage to tellurites and selenites of the late oxidation stage.