Crustal strain field of the Mongolia-Baikal rift zone and its geodynamic implications
蒙古-贝加尔裂谷区地壳应变场及其地球动力学涵义

The tectonics and crustal deformation of the Mongolia-Baikal Rift Zone (MBRZ), which is one of the most active tectonic zones in continents, is significant for understanding continental dynamics. Based on combined GPS velocities of MBRZ, the strain rate field and the strain energy variation were calculated. It is found that the Mongolian fold belt is characterized by a NNE-SSW compression with a small rate of 2.0×10-9/a, indicating the Mongolian fold belt is stable in current tectonics. The Baikal Rift Zone (BRZ) is being extended with a maximum strain rate of 2.5×10-8/a and high shear strain and dilation are found along BRZ, which implies that the rifting of BRZ may be controlled by various mechanisms. Two high-strain belts are found in western Mongolia,combining the evidence of mantle plumes in deep region, we suggest that the two belts and the enclosed region could be regarded as the west boundary of the Amurian plate-a diffused deformation boundary zone. The consistency between the shear strain pattern and the seismicity with hypocenter depth less than 40 km indicates a high level of coupling of deformation within crust. The consistency between the mantle convection-generated drag force and the principle axis of strain and strain rate suggests that mantle convection might be one of the controlling factors for regional tectonic process in MBRZ.