Zircon U–Pb and Hf isotopic constraints on the onset time of India-Asia collision

Abstract

The time of initial collision between India and Asia has been extremely controversial despite the fact that it is vital to constraining the orogenesis and subsequent evolution of the Himalayas and Tibetan Plateau. Here we report U–Pb and Hf isotope analysis of detrital zircons from two principal foreland basins, that is, the Sangdanlin and Gyangze basins respectively in the western and central parts of southern Tibet. Our data suggest that Asian-derived clastic sediments started contributing to sedimentation on the Indian continental margin earlier than generally thought, at ∼60 Ma in both basins near the Yarlung-Zangbo Suture Zone. In southern Tibet, no evidence for the existence of an intra-oceanic arc within the Neotethys is observed. We conclude that ∼60 Ma can be used to constrain the onset time of the India-Asia collision, at least in central Tibet. After this initial collision, closure of the Neotethys propagated both westward and eastward, with the final closure occurring at ∼50 and ∼45 Ma in northwestern and eastern Himalayas, respectively. Our conclusion differs significantly from the previous view that the India-Asia collision may have started in northwestern Himalaya and propagated eastward with diachronous suturing.