TIMING OF ORE MINERALIZATION IN THE DUKAT SILVER DEPOSIT BY DATA OF THE RB-SR METHOD

Abstract

Main temporal boundaries of the formation history of the Dukat silver deposit have been dated by the Rb-Sr method. The age of ore-hosting high-potassic rhyolites of the Askol'din suite was determined at 199 Ma; the age of granites of the early and late phases of the Bystrin complex at 93 and 88.5 Ma, respectively. The latter served as a heat source of the contact metamorphism in rhyolites (88.7 Ma). Their high-temperature fluid flows caused the skarnation of carbonate-bearing ores and the reduction of the age of quartz-adular ores to 86 Ma. Based on theoretical reasoning, the model age of crystallization of adular ores has been estimated at about 104 Ma. It was postulated that ore formation was related to mechanical and thermal action of the earliest diorite intrusion, which initiated the origin of a dome and the splitting of its roof and stimulated a volcanogenic ore-forming system with the development of intense metasomatic hydromicatization of rhyolites. Subsequent heat pulses eliminated the possibility of direct dating of these structures by the Rb-Sr method and necessitated using other isotope methods, in particular, the U-Pb zircon method.