Geologicheskii Vestnik

New data on the composition of rock-forming minerals of ore-bearing dikes, as well as gold-porphyry mineralization and near-ore metasomatites of the Bolshoy Karan deposit located in the zone of the Main Ural Fault in the Southern Urals are presented. The study of the chemical composition of minerals was carried out on a VEGA II LSH Scanning Electron Microscope (Tescan) with an energy-dispersive microanalyzer INCA Energy 350 (Oxford instruments). Several genetic groups of minerals have been identified at the deposit, corresponding to different stages of the formation of gold-porphyry mineralization and hydrothermal-metasomatic changes: 1) primary magmatic, 2) hydrothermal-metasomatic, 3) ore. The first group includes rock-forming minerals (pyroxene, plagioclase, hornblende, quartz, accessory apatite and zircon, titanomagnetite and ilmenite, possibly orthoclase) formed during the crystallization of magma of diorite composition. The second group includes minerals of the near-ore metasomatic halo, represented by prenite, albite, carbonate, chlorite, sericite, muscovite, quartz and, apparently, epidote. It is established that the gold-bearing sulfide mineralization is accompanied by the development of early potash feldspar-biotite and later albite-carbonate-chlorite-quartz metasomatites with an admixture of epidote and prenite. The third group is represented by sulfides of the ore stage (pyrite, chalcopyrite and galena). Thus, the study of inclusions of ore minerals in pyrites shows the presence of a polymetallic bias in the composition of interspersed sulfide ores.

Southern Urals, zone of the Main Ural Fault, Au-porphyry deposit, inclusions of ore minerals in pyrites

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