Geochemistry and isotopic ages of granitoids of the Bashkirian Mega-Anticlinorium: Evidence for several pulses of tectono-magmatic activity at the junction zone between the Uralian orogen and East European Platform

摘要

The study provides the first evidence for post-Riphean phases of granite emplacement in the Bashkirian Mega-Anticlinorium (BMA) at the boundary between the East European Platform and Uralian orogen. The tectono-thermal activity in the BMA is well-constrained by emplacement of the Kusa-Kopan plagiogranitoid intrusion (660 Ma) and late gneiss-granites of the Yurma complex (540 Ma). The geochemical features of these rocks are transitional between within-plate rift and orogenic suites. It was shown that the Paleozoic stage of the BMA was marked by emplacement of granites of the Kialim massif (314 Ma) and Semibratka complex (300 Ma). The age and geochemical features of these rocks are similar to those of Carboniferous granites of the Uralian orogen, which are interpreted to mark the end of subduction and beginning of collision. This similarity suggests that the BMA was adjoined to the Uralian orogen in the Carboniferous and Paleozoic granite emplacement in both structures was the result of their common geological evolution and protoliths of a similar geochemical composition.