The thermal evolution of Chinese central Tianshan and its implications: Insights from multi-method chronometry

The Chinese Tianshan is located in the south of the Central Asian Orogenic Belt and formed during final consumption of the Paleo-Asian Ocean in the late Palaeozoic. In order to further elucidate the tectonic evolution of the Chinese Tianshan, we have established the temperature-time history of granitic rocks from the Chinese Tianshan through a multi-chronological approach that includes U/Pb (zircon), 40Ar/39Ar (biotite and K-feldspar), and (U-Th)/He (zircon and apatite) dating. Our data show that the central Tianshan experienced accelerated cooling during the late Carboniferous- to early Permian. Multiple sequences of complex multiple accretionary, subduction and collisional events could have induced the cooling in the Tianshan Orogenic Belt. The new 40Ar/39Ar and (U-Th)/He data, in combination with thermal history modeling results, reveal that several tectonic reactivation and exhumation episodes affected the Chinese central Tianshan during middle Triassic (245-210 Ma), early Cretaceous (140-100 Ma), late Oligocene-early Miocene (35-20 Ma) and late Miocene (12-9 Ma). The middle Triassic cooling dates was only found in the central Tianshan. Strong uplift and deformation in the Chinese Tianshan has been limited and localized. It have been concentrated in around major fault zone and the foreland thrust belt since the early Cretaceous. The middle Triassic and early Cretaceous exhumation is interpreted as distal effects of the Cimmerian collisions (i.e. the Qiangtang and Kunlun-Qaidam collision and Lhasa-Qiangtang collision) at the southern Eurasian margin. The Cenozoic reactivation and exhumation is interpreted as a far field response to the India-Eurasia collision and represents the beginning of modem mountain building and denudation in the Chinese Tianshan.