Vodorazdelny Granite Massif (Subpolar Urals) and Correlation Problems of the Pre-Ordovician Granitoids and Volcanic Rocks from the Northern Part of the Lyapinsky Anticlinorium

Abstract

Petrogeochemical features of the Vodorazdelny massif granites (Subpolar Urals, Lyapinsky anticlinorium) indicate these rocks are close to I-granites and were formed in suprasubduction environment. The ratios of the key elements (Rb, Ba, Th, Sr, Y, Nb) suggest that the basites of the melting slab and the fluid separated during their dehydration could participate in the granite generation. The U–Pb age of the main population of magmatogenic zircons is 593 ± 4 Ma and corresponds to the Vendian (Ediacarian). It coincides with the age of the granites from the nearby Vangyr massif (598 ± 5 Ма), as well as with the age of zircon cores from the granites of the Kozhim massif located to the north. Values of εHf(t) from –2 to 0 in magmatogenic zircons with an age corresponding to the age of Vodorazdelny granites indicate a heterogeneous source of melts. The zircons of these granites also contain ancient cores with U–Pb ages from 2200 to 700 Ma, where the values of εHf(t) from +0.8 to +13 indicate the presence of a crust component in the substrate (the substance of the ancient platform basement). Petrogeochemical and isotope-geochronological parameters of granites (and their zircons) do not confirm the validity of attributing of Vodorazdelny granite massif (and its analogues – the Vangyr and Kozhim massifs) to the Cambrian Salner-Mankhambo complex. We consider there are the possibility of separating of independent complex (about 598 Ma, Vendian?) during geological mapping. The presence in the Lyapinsky anticlinorium of several stages of granite generation (Middle Riphean–Vendian–Cambrian), accompanied by metamorphism, and complicate composition of ancient metamorphic strata from this structure basement led to varying isotopic parameters characterizing the heterogeneity of the source of melts, on the one hand, and the convergence of a number of geochemical features, on the other.