Geochemical composition and geodynamic setting of formation of upper proterozoic deposits of Nyaroveyskaya series (Polar Urals)

Our study of the geochemical composition of the Upper Proterozoic metamorphosed volcanic-sedimentary rocks of nyaroveyskaya series in Central tectonic zone of the Polar Urals established that they had been formed in marginal-oceanic setting, possibly in back-arc marine geodynamic conditions. In the western area of distribution of nyaroveyskaya series the metabasalts are represented by high Fe tholeiites, whereas in the east - high Mg. They are geochemically similar and close to the composition of E-MORB basalt, supporting similar conditions of generation of the magmatic melt. Low Nb, Zr, and Hf contents of in the metabasalts indicate a supra-subduction nature of these formations. Metasedimentary rocks contain metapelite, metagraywacke and quartzite. Carbon and carbon-free quartzites correlate well by the content of rare earth elements. Carbon quartzites contain terrigenous-clastic and silicon varieties. Metamorphosed quartz sandstones occur only in the western area. Analysis of the geochemical composition of metaterrigenous nyaroveyskaya series suggested that their formation resulted from destruction of silicon-rich sedimentary rocks with the participation of acidic, medium and basic magmatic rocks of Early Proterozoic continental crust.