A comprehensive interpretation of thermochronological data in the Hengduan Mountains with tectonic implications

The Hengduan Mountains, located on the southeastern edge of the Tibetan Plateau, is a key area for understanding the lateral growth and outward expansion of the Tibetan Plateau. Although several kinematic models have been proposed, uncertainties remain. To refine our understanding of the deformation and exhumation histories of the Hengduan Mountains, the region is divided into 103 subareas, and new apatite and zircon (U-Th)/He ages combined with existing data are inverted for exhumation rates for each subarea using iterative pseudo-age-elevation profiles and Gaussian Linear Inversion of Data to Exhumation rate (GLIDE) modeling. These methods, calibrated with the current geothermal gradient, yield consistent exhumation patterns. Our results indicate two distinct phases of active deformation during the mid- to late Cenozoic. From the Oligocene to early Miocene, lateral shearing dominated to the west of the Ailao Shan–Red River Shear Zone, while crustal shortening prevailed along the Longmen Shan–Anninghe–Yalong–Yulong (Jinhe–Qinghe) Thrust Belts to the east. From the late Miocene to the present, the activation of the Xianshuihe–Xiaojiang Strike-Slip System marked a shift toward more diffuse and intensified deformation. This is reflected in increased activity along the Longmen Shan Thrust Belt, the southward migration of shortening from the Yalong–Yulong (Jinhe–Qinghe) Thrust Belts, and enhanced regional exhumation, particularly in the Three Rivers Region. The transition between the two phases is driven by changing boundary conditions due to rollback of the surrounding subducted plates offering more space or the rollback of southeastern Indian mantle lithosphere inducing a larger flow during the northward indentation of the Indian plate corner.