(U,Th)-He age of pyrite from the Karyernoe gold ore occurrence (flank of the Novogodnenskoye ore field, Polar Urals)

Abstract

In contrast to the developed areas of the Middle and Southern Urals, the hard-to-reach and eroded northern territories of the Ural folded system remain poorly studied, which determines a large number of unevaluated gold ore occurrences and single industrial objects. The Karyernoe gold ore occurrence is located among the Middle Paleozoic volcanic-clastic rocks of the Toupugol-Khanmeishorsky gold ore district on the eastern slope of the Polar Urals. The volcanic rocks show signs of early stratabound pyrite-like mineralization, which is cut by veins and dikes of the Sobsky (D1-2) and Musyur (C1-2) complexes. A new approach – (U,Th)-He pyrite dating – was used in order to determine the age of the sulfide mineralization of the Karyernoe ore occurrence, located on the flank of the Novogodnee ore field. (U,Th)-He pyrite ages (n=7) varies in a wide range from 402 to 425 Ma. Given the petrographic and mineralogical-geochemical observations, obtained data suggest the presence of at least two stages of rock mineralization: wenlock-ludlow – 424±6 Ma; and a later Early Devonian – 402±6 Ma, which is probably associated with the intrusion of Sob complex granitoids into the rocks of the Toupugolskaya formation. The obtained ages of the sulfide mineralization of the Karyernoe ore occurrence are significantly older than the age values established for large gold ore objects of the district: Petropavlovskoye and Novogodnee-Monto deposits (~382 million years). Taking into account the position of the Karyernoe ore occurrence on the flank of the Novogodnee ore field, it can be assumed that the disseminated and layered sulfide impregnation of the volcanic rocks of the Toupugolskaya formation could have acted as one of the sources of sulfur and ore metals for later stages of sulfide mineralization in the Toupugol-Khanmeishorsky district.