Kinematic inversion of the Xianshuihe-Xiaojiang fault system from Oligocene shortening to late Miocene left-lateral slip in the southeastern Tibetan Plateau

Several continental-scale strike-slip faults in the southeastern Tibetan Plateau developed during the Cenozoic eastward growth of the plateau. However, geodynamic mechanisms driving plateau growth and their relationship to intracontinental deformation remain poorly resolved, primarily because the brittle deformation histories of major fault systems—such as the >1000-km-long Xianshuihe-Xiaojiang (XSH-XJ) fault system—are inadequately constrained and difficult to reconstruct. To address this gap, we performed thermochronological analyses of samples from the highest mountains (i.e., Jiaozi Shan and Dahaicao Shan) flanking the XJ segment of the fault system, including apatite (U-Th)/He, apatite fission track, and zircon (U-Th)/He dating, complemented by thermal history modeling. Results reveal differential exhumation and cooling across the XJ fault between ca. 26 Ma and 22 Ma, with greater cooling in the Jiaozi Shan (30−50 °C) than the Dahaicao Shan (