Age and Ore Matter Sources of Au-Sulfide Mineralization of the Tanadon Deposit, Republic of North Ossetia–Alania, Greater Caucasus

The results of geochronological, petrological–mineralogical, and isotope-geochemical studies of the Tanadon gold deposit in the Greater Caucasus (Republic of North Ossetia–Alania) have made it possible to determine the age of ore veins and identify ore matter sources of sulfide mineralization. The Tanadon deposit is localized in Paleozoic synmetamorphic granitic rocks at the southern margin of the epi-Hercynian Scythian Plate, which is included in the tectonic zone of the Main Caucasus Range. The orebodies are represented by quartz veins varying in thickness and containing complex sulfide mineralization (pyrite, arsenopyrite, chalcopyrite, pyrrhotite, galena, sphalerite, stannite, cobaltite, and bismuthinite). Arsenopyrite is the main repository of invisible gold. Mineralogical data provide evidence for hydrothermal ore formation, which proceeded at least in two stages, giving rise to earlier pyrite + arsenopyrite and later galena + sphalerite + chalcopyrite mineral assemblages. The Tanadon deposit is a zone of intense young magmatic activity. Neointrusions widespread therein are related to the Early Pliocene Tsana Complex (trachyandesitic dikes, ~4.7 Ma in age) and to the Late Pliocene–Early Pleistocene Tepli Complex (dacitic necks, ~1.4 Ma). According to K–Ar dating of sericite from ore-bearing veins, the Tanadon deposit formed synchronously with Early Pliocene dikes of the Tsana Complex. The total duration of the hydrothermal process likely did not exceed hundreds of thousands of years. As follows from Pb-isotope-geochemical data, hydrothermal processes coeval with Early Pliocene magmatic activity, as well as geological relationships between ore-bearing veins and trachyandesitic dikes, show that the sulfide mineralization of the Tanadon deposit is genetically related to the intrusive Tsana Complex. The main source of ore components is represented by hydrothermal solutions produced in an Early Pliocene melt spot localized beneath the considered part of Greater Caucasus. In the adjacent territory of Georgia, a number of ore objects similar in structure and mineral composition to the Tanadon deposit are also genetically and spatially related to the intrusions of the Tsana Complex. Therefore, the Tsana Complex should be regarded as productive and the areas occupied by Early Pliocene intrusive bodies as promising for Au-bearing arsenopyrite and base-metal mineralization.