Petrographic and geochemical peculiarities of carbonaceous rocks of the upper proterozoic deposits of the Polar Urals

Black shales attract the attention of geologists due to the increased content of gold, nonferrous metals and rare earth elements. In the Central Polar Urals tectonic zone the carbonaceous rocks are distributed in the Upper Riphean deposits of the Nyarovei series and the Nemuryugan suite. According to the works of predecessors, they are characterized by superclarks content of silver, zinc, lead, vanadium, phosphorus and platinoids, and their study is of great practical interest. The typification of carbonaceous rocks of the Nyarovei series and the Nemuryugan suite by petrographic and geochemical criteria was carried out.The study of carbonaceous rocks of the Upper Proterozoic deposits of the Central Polar Urals tectonic zone showed that in the Nyarovei series they are represented by epidote-albite-chlorite-quartz-sericite terrigenous, chlorite- muscovite-quartz, muscovite-quartz terrigenous-siliceous low-carbon and carbo- naceous black shales, in the Nemuryugan suite - by quartz-carbonate low-carbon black shales. The main source of rare-earth elements, U and Th, is terrigenous material. The terrigenous black shales of the western zone of the Nyarovei series appear to fulfill a resource function in the uranium ore formation (U up to 110 ppm), while the terrigenous-siliceous black shales of the eastern zone - a barrier function in the formation of abnormally high accumulations of endogenous gold (Au up to 2,6 ppm).