Xu, Xi, Zuza, Andrew V., Yin, An, Yu, Peng, Chen, Zhiyong, Zhao, Chongjin, Wang, Baodi, Chen, Hanlin, Lin, Xiubin, Wu, Lei, Kuang, Xingtao, Tian, Hefeng, Yin, Qihang, and Yang, Shufeng
The factors that control strain partitioning along plate boundaries and within continental interiors remains poorly resolved. Plate convergence may be accommodated via distributed crustal shortening or discrete crustal‐scale strike‐slip faulting, but what controls these differing modes of deformation is debated. Here we address this question by examining the actively deforming regions that surround the Tarim Basin in central Asia, where deformation is uniquely partitioned into predominately strike‐slip faults in the east and distributed fold‐thrust belts in the west to accommodate Cenozoic India‐Asia plate convergence. We present integrated geological and geophysical observations to elucidate patterns in crustal deformation and compositional structure in and around the Tarim Basin. The thrust‐dominated western Tarim Basin correlates with a strongly‐magnetic lower crust, whereas strike‐slip faulting along the eastern margins of the Tarim Basin lack such magnetic signals. We suggest that the lower crust of the western Tarim is more mafic and stronger than in the east, which impacts intra‐plate strain partitioning. A stronger lower crust results in vertical decoupling to drive mid‐crust horizontal detachments and facilitate thrust faulting, whereas a more homogenized crust favored vertical transcrustal strike‐slip faulting. These rheological differences likely originated from the impingement of the Permian Tarim plume focused in the west. A comparison with the Longmen Shan of eastern Tibetan Plateau reveals remarkably similar strain partitioning that correlates with variations in foreland rheology. Our results highlight how variations in lower‐crust viscosity impact strain partitioning in an intra‐plate setting and how plume processes exert a strong control on later continental tectonic processes. Plain Language Summary: Crustal deformation propagates far into the continental plate interior when continental plates collide and converge. Sometimes intra‐plate deformation is expressed via distributed crustal shortening in fold‐thrust belts and sometimes it is manifested as discrete vertical strike‐slip faults that accommodate lateral plate motion. It remains unclear what dictates which mode of deformation operates within the continental interior. Here we examined the patterns and compositional structure of deformational belts around the Tarim Basin in central Asia using integrated geological and geophysical datasets. The western Tarim Basin is characterized by distributed shortening and the eastern basin is characterized by strike‐slip faulting, and these differences correlate strength variations in the lower crust imaged via magnetic surveys and inversions. Specifically, we hypothesize the stronger crust of the western Tarim Basin allows the upper crust to detach to develop fold‐thrust belts, whereas the eastern Tarim Basin has a more homogenously strong crustal column that is cut by vertical strike‐slip faults. Our proposed model with lower‐crust rheology controlling the mode of intra‐plate deformation may be broadly applicable to zones of continental deformation. Key Points: Crustal deformation around the Tarim Basin is uniquely partitioned into predominately strike‐slip faults in the east and distributed fold‐thrust belts in the westLower crustal viscosity impacts crust‐scale deformation and strain partitioning in an intraplate settingPlume‐driven crustal modification exerts a strong control on later continental tectonic process [ABSTRACT FROM AUTHOR]