A Uniform Orogen‐parallel Extension System of the Shear Zones in the Tongbai‐Dabie Orogenic Belt, Central China

Large‐scale magmatism affected the Tongbai‐Dabie orogenic belt during post‐collisional lateral tectonic extension in the Cretaceous, which was suggested to account for the widespread deformation and migmatization in the Tongbai‐Dabie complexes. However, it cannot explain the most deformations in the shear zones. The northwest‐southeast shear zones are developed around or wrapped the Tongbai‐Dabie complexes. They play an important role for the interpretation of the tectonic evolution of the Tongbai‐Dabie orogenic belt. By a systematically observation and description of the geometry and kinematics of these shear zones, we found that the shear zones to the north dip NE and have a uniform sinistral shear sense, the shear zone to the south dips SW and has a uniform dextral shear sense, and the shear zones at the core are sub‐horizontal and have a uniform top‐to‐NW sense of shear. Combining with the comparison of previous and our geochronological studies, we interpret these associations as indicating that these shear zones were originally a single, more flat‐lying and sub‐horizontal shear zone with a uniform top‐to‐NW shear sense before the folding‐doming of the Tongbai‐Dabie complexes and suggest that the Tongbai‐Dabie orogenic belt experienced a uniform top‐to‐NW orogen‐parallel extension in the ductile lithosphere before the widespread magmatism in the Cretaceous.