Multi-stage exhumation history of the West Kunlun orogen and the amalgamation of the Tibetan Plateau

Abstract

The West Kunlun range, along the northwest margin of the Tibetan Plateau contains an important record of plateau formation and its northwards expansion. However, apart from the well-documented Miocene tectonism, its long-term history of exhumation/uplift remains enigmatic. Here we report an integrated low-temperature thermochronology study (apatite fission track and corresponding zircon (U-Th)/He) across a N-S transect through the West Kunlun range that reveals a prolonged low-temperature thermochronological record, characterized by a complex mosaic of thermal histories from the individual terrane elements during amalgamation to form the Tibetan Plateau. Our new data reveal two prominent cooling episodes during the Cretaceous and the Neogene, as well as several other more subdued and/or localized cooling episodes. Late Permo-Triassic cooling correlates with the accretion of the West Kunlun, Songpan-Ganzi and Tianshuihai terranes. Early Cretaceous cooling is considered as a response to collision between the Qiangtang and Lhasa terranes, while Late Cretaceous cooling relates to collision between the Karakorum terrane and Kohistan-Ladakh Arc. Partially preserved evidence for cooling in the Paleocene-Early Eocene and latest Oligocene-Miocene likely relates to the early stages of Indo-Asian collision. Our work confirms relatively low Neogene denudation rates of about 0.1-0.2 km/myr consistent with its arid, intraplate tectonic setting with deformation resulting from stress propagated via the surface plates and most likely sourced in the buoyancy of the plateau itself.