Activity of the Baiganhu Fault of the Altyn Tagh Fault System, northern Tibetan Plateau: Insights from zircon and apatite fission track analyses

Abstract

The geometry and kinematics of first-order structural systems on the Tibetan Plateau (TP) are key to understanding how the continental crust and lithosphere deformed during the India-Asia collision. The Altyn Tagh Fault (ATF), which is a large-scale fault bounding the northern edge of the Tibetan Plateau (NTP), absorbed as much as one-third of the total convergence in the collision between India and Eurasia. The Baiganhu Fault, in the western Qimen Tagh Mountains on the NTP, is recognized as belonging to the ATF and has played an important role in the development of its adjacent region. Due to the high elevation and harsh working conditions, this fault has received little attention, and the timing of its activation has not been thoroughly researched. In this study, we collected granite samples from close to the Baiganhu Fault in the Qimen Tagh Mountains, and used zircon and apatite fission track dating to constrain the timing of activation for this fault. The fission track ages and HeFTy modeling results reveal two rapid cooling stages along the Baiganhu Fault: one during the Jurassic-cretaceous (~180–120 Ma) and the second since the mid-Miocene (~15–10 Ma), consistent with other regions on the NTP. The first fast exhumation event was a far-field response to the Lhasa-Qiangtang collision, and the second stage most likely resulted from crustal thickening, with a connection to the ATF occurring at around ~15–10 Ma.