Porphyry Ore-Magmatic Labaznoe System (the Omolonsky Cratonic Terrane, Northeast Russia): Age, Mineralogy of Mineralization and Mineral Thermobarometry of Ore-Bearing Granitoids in the Viktorinsky Complex

This paper provides new data on the age (U–Pb, LA-SF-ICP-MS: 86 ± 1 Ma) of quartz monzodiorites of the Viktorisky complex in the Konginsky igneous zone of the Omolonsky cratonic terrane. The Labaznoe ore occurrence, which contains streaky-stockwork sulfide–quartz and vein polymetal mineralization, is localized within an intrusive dome uplift in whose central part a monzodiorite stock of the Viktorinsky complex is exposed. Petrographic and geochemical characteristics and mineral thermobarometry of the ore-bearing quartz monzodiorites are provided. Ore mineralogy is gien along with an estimate of the isotopic age (K–Ar: 82 ± 4 Ma) for the crystallization of sericite from a circumvein contact with the monzodiorite intrusion. Geological interrelationships and isotopic geochronologic data are used to find a paragenetic relation between the porphyry molybdenum mineralization and the phase of Late Cretaceous magmatism, viz, emplacement of Viktorinsky granitoid bodies. The phases have been reconstructed involving the formation of paragenetic mineral associations in the sequence magnetite–quartz, molybdenite–quartz, and sulfide–quartz; the hypogene phase terminates in a polymetallic phase. The materials of isotope dating of the ores and of ore-bearing granitoids in the area of study provide evidence of a Late Cretaceous (Coniacian‒Campanian) age of the porphyry igneous ore system in the Konginsky igneous zone.