U-Pb Age and Petrogeochemistry of the Granitoids (Semibratskii Complex, Northeastern Part of the Bashkirian Meganticlinorium) as Indicators of Their Early Orogenic Nature

摘要

The junction zone of the Ural Orogen with the East European platform (EEP) is a striking example of boundary areas between geological structures of contrasting evolution. It is characterized by a complex structure and high-grade metamorphism, which complicates reliable determination of their age, geody-namic settings, and all stages of evolution. One of the poorly studied segments of this zone is the northeastern part of the Bashkirian meganticlinorium (BMA), which contains metasedimentary and metavolcanogenic rocks of controversial stratigraphic position. Unfortunately, lithology and petrocheochemistry do not always allow definite determination of the geodynamic regime.