Thermochronological evidence for multi-phase uplifting of the East Kunlun Mountains, northern Tibetan Plateau

Multiple phases of Mesozoic and Cenozoic cooling and uplifting events are derived from fission track (FT) dating of zircons and apatites and thermal history modeling of apatite FT ages from several plutons in East Kunlun near Golmud City. Two phases of Mesozoic cooling histories revealed by zircon FT ages are phase I in Jurassic (194.1~144.4 Ma) and phase II in Early Cretaceous (115.7~100.2 Ma). Three phases of Cenozoic cooling histories revealed by apatite FT ages and thermal history modeling are phase I in early Eocene (~52.9 Ma), phase II in middle Miocene (16.3~10.0 Ma), and phase III in Pliocene (5.1~0.9 Ma), which are considered to be closely related to the activity of Cenozoic East Kunlun thrust system. Cenozoic phase I (~52.9 Ma) cooling is consistent with the short time living of a small foreland basin formed on the north margin of the East Kunlun Mountains. The spatial distribution of apatite FT ages in Cenozoic phase II (16.3~10.0 Ma) and III (5.1~0.9 Ma) suggests the piggyback thrusting of the East Kunlun thrust system and the forming of piggyback Qaidam Basin as a result of basin-mountain coupling. According to the age comparability of the end of thrusting in Cenozoic phase II and the beginning of the major sinistral strike-slipping of Kunlun Fault, it is inferred that there was a deformational transfer from compressing to shearing at ~10.0 Ma.