Petrochemical features of granite-gneisses of the Nikolaishor massif (Subpolar Urals)

The Nikolaishor massif is located within the heavily eroded gneisses of the Nyarta metamorphic complex and is an autochthonous massif composed of plagiogranites and kalispartic granites. The conducted petrochemical study of the least modified variety of granites of this massif made it possible to identify the petrochemical features of the studied rock, as well as to determine the geodynamic conditions for the formation of the Nikolaishor massif. According to the results of the silicate analysis, granites are high-alumina leucogranites of the potassium-sodium type. The initial substrate for the studied rocks was presumably magmatic protolith. Based on the ICP-MS analysis data, various indicator ratios were calculated for the granites. The obtained indicators allowed us to conclude that the rocks under consideration were formed from melts enriched mainly with light TR, which belong to a deep crustal type source. Comprehensive study of multivariate discriminant analysis indicators for the main elements of S. Agrawal, as well as diagrams of J.A. Pearce, D. Papu, N.B. Harris, showed that the rocks of the Nikolaishor massif are syncollisional granites formed in the Late Orogenic time.