New data on genesis of the crust in the eastern segment of the Middle Urals: Sr-Nd isotopic constraints

摘要

The analysis of the Sr and Nd isotopic composition in different granitoids of the Verkhisetsk, Shartash, Krasnopolsk, Petrokamensk, and Shabry massifs, which were successively formed in the island arc, continental marginal, and collisional geodynamic settings during the period from the Middle Devonian to the early Permian, revealed that Sr-87/Sr-86(0) values in them vary from 0.70331 to 0.70431 and epsilon(Nd)(t), from +1.9 to +6.2. The two-stage model Nd age of granitoids (938-629 Ma) indicates that their magma originates from material at least Neoproterozoic in age, not younger. The observed variations in the Nd model ages of granitoids and Sr-87/Sr-86(0) values provide grounds for assuming the primary heterogeneity of the source of granitoid melts.