New type of gold-bearing mineralization at the Ozernovskое Au-Te-Se epithermal deposit (Central Kamchatka, Russia)

The ores of the Ozernovsky Au-Te-Se epithermal volcanogenic deposit are located in linear zones of secondary quartzites in volcanic rocks of Neogene age and are represented by linear stockworks and tubes of quartz hydrothermal breccias interspersed with ore minerals — sulfides, tellurides and selenides. A new type of gold-bearing mineralization has been discovered and studied on the upper horizon of the deposit. The main gold mineral is maletoyvayamite (Au3Se4Te6), which forms small inclusions in selenium native tellurium, together with micro inclusions of other, usually also very rare, minerals — bambollaite (Cu1-x(Se, S, Te)2), fahlores of the goldfieldite and ústalečite subgroups. This mineral complex could have been formed in the upper part of a boiling hydrothermal system as a result of mixing of the ascending flow of heterogeneous water-steam fluid with oxygen-enriched surface waters and oxidation of the reduced forms of sulfur, selenium and tellurium contained therein. The primary complex of ore minerals is usually partially replaced by several generations of hypergenic minerals: from native selenium and Au-Ag selenides of the early stage to tellurites and selenites of the late stage of oxidation.