Eocene Exhumation in the Rena Co Area, Southern Qiangtang Terrane: Constraints on the Extent of the Central Tibetan Valley

Abstract The Qiangtang terrane is located in the central part of the Tibetan Plateau, and reconstructing its uplift and exhumation history is crucial for understanding the Tibetan Plateau’s formation and growth. In particular, the uplift process at its southern margin could provide constraints on the extent of the Central Tibetan Valley. In this study, we employ zircon U-Pb dating, Al-in-hornblende barometry, apatite fission track, and apatite (U-Th)/He to determine the exhumation history of Rena Co area, which is located in the western part of the southern edge of the Qiangtang terrane. Zircon U-Pb dating yielded emplacement ages of 148.81–153.85 Ma, with emplacement depths of ~7.6–12.5 km constrained by Al-in-hornblende barometry. Considering the regional thrust fault activity and adakitic volcanic rocks, the rapid exhumation during 60–50 Ma revealed by thermal history modeling is associated with the crustal shortening and thickening driven by India-Asia collision. The slow exhumation since 50 Ma marks the establishment of the proto-Tibetan Plateau in the Rena Co area. The Qiangtang terrane uplifted ~10–20 Ma earlier than the basins along the Bangong-Nujiang suture zone. The uplifted Qiangtang terrane bounded the Central Tibetan Valley to the north, which did not extend into the north-central Qiangtang terrane. The northern boundary of the Central Tibetan Valley is near the Bangong-Nujiang suture zone.