Accretionary orogenic process of Western Tianshan, China

The Western Tianshan area is situated along the southwestern margin of the Central Asia Orogenic belt and has undergone an accretional orogenic process. It is also a tectonic zone where the wide active margin in the southern Siberia finally amalgamated with the passive margin of the northern Tarim. On the basis of recent research advances, we subdivide the Western Tianshan into following tectonic units: the North Tianshan Arc Accretionary Wedge, the Northern Active Continental Margin of the Yili block, the Yili block, the Southern Active Continental Margin of the Yili block, the Central Tianshan Composite Arc Terrane, the Western Tianshan (high-pressure) Accretionary Wedge and the Northern margin of the Tarim block. The new chronological data of ophiolites, high-pressure metamorphic rocks and granitoids have also been summed up in order to discuss the accretionary orogenic process of the western Tianshan. This orogenic process is related to the evolution of three paleo-oceanic basins, namely, the early Paleozoic ‘Terskey Ocean’, the latest early Paleozoic-late Paleozoic ‘South Tianshan Ocean’ and the late Paleozoic ‘North Tianshan Ocean’. The accretionary orogenesis terminated at the end Early Carboniferous. Subsequently, the Western Tianshan and the whole Central Asia may have evolved into a post-collisional stage in Permian. The data obtained up to now has demonstrated that the Western Tianshan Orogen is a late Paleozoic accretionary orogenic belt, instead of a Triassic collisional one.