Mesozoic−Cenozoic exhumation and tectonic evolution of central Tibet

Orogenic plateaus preserve a long-term record of lithospheric deformation. The evolution history of the Tibetan Plateau, the world’s largest orogenic plateau, is obscured by multiple tectonic overprints, especially in central Tibet (Qiangtang and Hoh Xil−Songpan-Ganzi terranes). Understanding the Mesozoic−Cenozoic tectonic history is critical because this interval covers the successive closures of the Paleo-, Meso-, and Neo-Tethys Oceans, and corresponding terrane collisions, all of which have shaped the plateau’s present topography to varying degrees. Here, we present new zircon U-Pb and apatite fission-track data from Late Jurassic−Paleogene sandstones and igneous clasts from central Tibet. Detrital zircon U-Pb dates constrain provenance, whereas apatite fission-track ages reflect exhumation, together providing a record of deformation and exhumation of the sedimentary sources. The data show that during the late Early Jurassic−earliest Cretaceous (180−140 Ma), the Hoh Xil−Songpan-Ganzi terrane was largely a peneplain that supplied detritus for the Qiangtang shallow- and marginal marine deposits. In the Early Cretaceous (130−100 Ma), the closure of the Meso-Tethys Ocean and subsequent Lhasa-Qiangtang collision drove widespread deformation across Qiangtang, except in northern North Qiangtang. By the Late Cretaceous (90−70 Ma), deformation had shifted northward into the central and northern North Qiangtang and Hoh Xil, likely associated with the flat-slab subduction of the Neo-Tethys oceanic lithosphere beneath southern Tibet. Resumption of normal-angle subduction of the Neo-Tethys Ocean (70−60 Ma) and the subsequent India-Asia collision (60−50 Ma) led to focused deformation in South Qiangtang and central North Qiangtang. Northward thrust loading from the Tanggula thrust belt in central North Qiangtang resulted in deposition in the Hoh Xil foreland basin. During the middle Eocene−early Oligocene (50−30 Ma), the plateau’s northern boundary and deformation front migrated northward, transforming the Hoh Xil foreland basin into hinterland basins. No evidence of horizontal shortening was found in central Tibet during the Neogene (after 23 Ma); however, the Hoh Xil Basin probably experienced additional surface uplift due to subsurface geodynamic processes. Together, these results highlight the following: (1) Central Tibet experienced two distinct phases of northward plateau growth during the Cretaceous and Cenozoic, and (2) early Mesozoic Paleo-Tethys tectonic events contributed negligibly to the present high elevation of the Tibetan Plateau.