Deformation characteristics of granitic rocks in Erguna ductile shear zone, NE China

The Erguna ductile shear zone is situated in the Erguna Massif, which has been exposed along the eastern bank of the Erguna River in northeastern China. The authors present comprehensive study results on the macro- and micro-structures, finite strain and kinematic vorticity, quartz electron backscatter diffraction (EBSD) fabrics, and geochronology of granitic rocks in the Erguna ductile shear zone. The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing. Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites. Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550 ℃. New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic (~248.6 Ma) and Early Cretaceous (~136.7 Ma). All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.