Paleocene to Eocene tectonic evolution of northern Lhasa terrane: Insights from structural geology and thermochronology data in the Nagqu region

The growth of the Tibetan Plateau had a profound impact on both the regional and global climatic change. When and how the northern Lhasa terrane attained its current elevation, however, remains controversial. Situated in the east part of northern Lhasa terrane, the Nagqu region comprises Precambrian to Cenozoic rocks that preserve the archives of structural deformation and uplift history. Here, we report new geological mapping, balanced cross sections, and apatite fission-track data from the Nagqu region. The deformation studies indicate that the Nagqu region underwent intense thrusting during ca. 60−35 Ma, likely caused by the India-Asia collision and subsequent intercontinental convergence. The balanced cross section suggests that the Nagqu fold-thrust belt accommodated at least 82 km (34% to ∼39%) of N−S shortening during ca. 60−35 Ma. Integrating our results with previous studies on the deformation, paleoelevation, and magmatism of the region, we infer that how the northern Lhasa terrane attained its modern elevation is most likely due to both crustal shortening and mantle upwelling.