Timing and Kinematics of late Cenozoic Strike-slip Faults in the Western Tibetan Plateau: New Constraints from Provenance Analysis and Detrital Thermochronology

The activities of the three large strike-slip fault systems-the Karakoram, the Karakax, and the Longmu CoGuozha Co faults-located in the western Tibetan Plateau have induced the intense exhumation of the Karakoram and the southern Western Kunlun ranges. However, the histories of these faults remain debated or loosely constrained, partly due to the restricted access to bedrock samples and associated comprehensive analyses. The application of detrital provenance analysis and detrital thermochronology to sediments can provide valuable information on the locations, crystallization timing, and exhumation of the source terranes of the sediments, thereby shedding light on tectonic histories. This study utilizes modern fluvial sand to obtain exhumation information on the Karakoram and the southern Western Kunlun ranges and to reconstruct the history of the major faults. We achieve this through provenance analysis (heavy-mineral analysis and detrital zircon U-Pb dating) and detrital apatite fission-track dating. Our results reveal widespread Paleogene rock exhumation across the western Tibetan Plateau and focused mid-Miocene (ca. 15-12 Ma) exhumation along the Karakoram and the southern Western Kunlun ranges. Moreover, the Karakoram Range experienced renewed exhumation at ca. 7 Ma. Through an integration of our results and regional geological evidence, we suggest that the focused mid-Miocene exhumation reflects the initiation of the Karakoram and the Karakax faults; the subsequent ca. 7 Ma exhumation episode of the Karakoram Range indicates a regional kinematic reorganization due to the initiation of the Longmu Co-Guozha Co Fault. We propose that the middle and late Miocene strike-slip faulting in the western Tibetan Plateau was driven by the oblique underthrusting of the Indian lithosphere.