Tectonic Evolution Of The Eastern Himalayan Syntaxis(Namche Barwa)from Low Temperature Thermochronology

As a result of the collision between India and Eurasia,the Eastern Himalayan Syntaxis,with the development of high altitude,monsoon climate,large rivers and glaciers,is featured by active tectonics and intensive erosion,resulting in rapid evolution of the landscape which in turn controls the evolution of rivers and the climate in adacient regions.How the Eastern Himalayan Syntaxis was formed is of great significance to further understanding uplift of the Tibetan Plateau and its impact on regional climate and the interaction among tectonics,erosion and climate.At present,models regarding how the Eastern Himalayan Syntaxis was developed can be divided into two categories: one emphasizes tectonics and the the other emphasizes the coupling between surface process and tectonics.In order to distinguish these two models,and to reveal the relationship among tectonics,erosion and climate in this area,we collected bedrock samples along the Yigong River to the north of the Eastern Himalayan Syntaxis.Multiple low-temperature thermochronometers including Apatite and Zircon(U-Th)/He(AHe,ZHe),Apatite Fission track(AFT)and Thermoluminescence thermochronology(TL)of K-feldspar were used to establish the temporal and spatial patterns of erosion rates of the Yigong River.Our results show that the Yigong River near the confluence of the Yigong and Palong River began to be rapidly exhumed at least since 0.3Ma with exhumation rates of > 10 mm/yr.The upper reaches of the Yigong River 50 km away from the confluence also experienced rapid exhumation at least sicne 100 ka,with an average exhumation rate of ? 4.5-10 mm/yr.Besides,exhumation along the lower reach of the Yigong River from the confluence to 50 km in the upstream was gradually decreased since 60 ka to a present exhumation rate of ?2 mm/yr.Rapid exhumation on the Yigong River indicates that the high exhumation locus is not restricted in the Yalu Zangbo Canyon,core of the Eastern Himalayan Syntaxis,but also moves northward.We suggest that rapid exhumation on the Yigong River is driven by regional tectonics,which is a result of the northward expansion of the Eastern Himalayan Syntaxis...