The conditions of formation of Au–Ag epithermal mineralization of the Amguemo-Kanchalan volcanic field (Eastern Chukotka)

Abstract

The article considers the conditions of formation of Au–Ag epithermal mineralization of the Amguemo-Kanchalan volcanic field (AKVP), located on the Western closure of the East Chukchi flank zone of the Okhotsk-Chukchi volcanic belt (OCHVB). In the AKVP potentially large Au–Ag Valunisty mine and several perspective deposits and ore occurrences (Zhilnoye, Shah, Gornoye, Ognennoye and Osennee) are localized. The results of thermo- and cryometric studies of fluid inclusions in quartz and calcite of epithermal veins showed that the solutions was dominated by chlorides Na and K. Epithermal mineralization was deposited by heterogeneous hydrothermal fluids with low salt concentrations (0.2–3.6 wt. % equiv. NaCl, in medium-temperature conditions – 174–354°C). The fluid pressure reached 30–160 bar, which corresponds to the formation depth of 0.1–0.6 km, under hydrostatic conditions. The obtained results allow us to attribute the studied epithermal mineralization to the low sulfidation class. The magmatic hearth of andesitic magmas and meteoric waters are the most probable sources of ore-forming fluids. The information given in the article is of practical importance for regional forecast-metallogenic constructions, prospecting and evaluation of epithermal Au–Ag deposits.