The Nemuryugan suite: petrographic and geochemical features

The object of our study is Nemuryugan suite in Upper Riphean Central Tectonic zone of the Polar Urals. These rocks are characterized by scarn and high gold content. The formation conditions of ore mineralization are still poorly known. We studied primary composition and formation conditions of Nemuryugan suite. The rocks are phyllite, shale, quartzite, carbonate-epidote-quartz-albite-chlorite rocks, carbonaceous quartz-carbonate rocks and marble. Phyllitic shales are divided into non-carbonate and carbonate varieties. They consist of clay and a fraction of aleurites. Prototypes for epidote-quartz-albite-chlorite shales are tuffs of intermediate and basic composition. Phyllitic quartzite and shales are geochemically similar to, respectively, silicon and silicon terrigenous formations of underlying Nyarovey series, as well as to subduction granitoids and gneisses of Precambrian greenstone belt. Supra-subduction granitoids are parent species. The protoliths of Nemuryugan suite formed in the deep water part of the back-arc sea.