Cenozoic low temperature cooling history of the Northern Tethyan Himalaya in Zedang, SE Tibet and its implications

Abstract

Major structures and climatic change during the Cenozoic (especially Miocene) interacted to shape the giant Tibetan Plateau, whose formation was triggered by convergence of Indian and Asian plates. In this work, we report a low-temperature thermochronology data set from the northern Tethyan Himalaya and Indus–Yarlung suture zone in the Zedang area, where structures are defined by two parallel thrusts (the Zhongba–Gyantse Thrust to the south and Great Counter Thrust to the north). Eighteen samples from the region constrain their low temperature cooling and exhumation histories and further elucidate the evolution of the southern Tibetan Plateau. Thermal history modelling reveals Eocene and Miocene cooling episodes. Based on the temporal and spatial patterns, Eocene cooling is probably linked to crustal thickening resulting in the Eocene anatexis in the northern Tethyan Himalaya; the rapid pronounced cooling episode between ca. 20Ma and 15Ma in the Luobusha area reflects the activity of the Great Counter Thrust (GCT); the ca. 14–10Ma cooling event of the Yardoi dome can probably be linked to rapid erosional denudation during that period; and pronounced cooling commencing in the middle Miocene was probably caused by incision of branches of the Yarlung–Zangbo River. A further cooling episode commencing in late Miocene time (ca. 5Ma) in Luobusha area and Yardoi dome, may reflect initial activity of the Cona Graben cutting through the region.