The Nevenrekan Gold–Silver Volcanogenic–Plutonogenic Deposits, Magadan Region, Russia: Host Rocks, Host-Rock Metasomatites, Age, and Material Composition of the Ores

This study is concerned with the material composition of the ores and the ore-bearing rocks of the Nevenrekan Au–Ag deposit. We provide a petrographic description of the rocks and their metasomatic alterations within the ore field, as well as structural and textural features of the ores. Two hypogenetic phases have been identified in the mineralization. The first, epithermal, volcanogenic phase consisted in the formation of adularia–carbonate–quartz veins and host-rock metasomatites of quartz–hydromica composition, of polysulfide and gold–sulfosalt mineralization, of extensive kaolinization regions, which gives way to chlorization and carbonatization with increasing depth. The contact action of a granitoidal pluton during the second phase gave rise to Te-, Bi-, and Sn-bearing mineral parageneses, silicification, epidotization, and sericite–quartz alterations of the host rocks. We showed the sequence of formation for paragenetic associations of minerals. Our inference is that the deposit is a multiformation feature with no analogues within the Evensky ore region. The age of epithermal mineralization as determined by the 40 Ar/ 39 Ar technique using the adularia in ore veins was 79.4 ± 1.0 Ma, which is consistent with the age of several major epithermal gold–silver deposits in the Okhotsk–Chukchi volcano-plutonic belt.