Geological settings and conditions of genesis of volcanogenic deposits of non-ferrous metals in Paleoisland arc environments

By the example of the Pontian-South Caucasian paleoisland arc actively functioning during the whole Mesozoic the authors consider the main peculiarities of spatial-temporal relationships between ores of non-ferrous metals and enclosing rocks, and discuss the conditions of the evolution of ore-magmatic systems. The authors’ conclusions are substantiated by data on ⁸⁷Sr/⁸⁶Sr ratios, concentration of rare elements in enclosing volcanogenic rocks, isotopic ratio of sulphur and oxygen in ores, and results of thermobarogeochemical studies. The authors hold the opinion shared by many mining geologists that the main part of ore components in non-ferrous metal deposits was extracted from nearby magmatites enclosing and underlying mineralized zones. The solutions from which ores precipitated were, by their salinity, very close to sea water. The maximum temperature of ore formation at epigenetic deposits reached 400°C for copper ores and 280°C for barite-polymetallic ores, whereas the pressure did not exceed 200 bar. As for hydrothermal-sedimentary ores, they could most likely form at the sea bottom, at depths of 2-3 km and maximum temperature no more than 300°C.