Closing history of the southern Tianshan oceanic basin, western China: an oblique collisional orogeny

The Tianshan (Tien Shan) Range is an important Paleozoic collisional orogen ic belt and the key to understand the central Asia tectonic evolution. This paper integrates our research results with the existing Chinese and intern ational literature on sedimentology, geochemistry, isotopic geochronology, paleontonology and paleomagnetism of the Tianshan and Tarim regions to prop ose that the oblique collision may have played an important role in the lat e Paleozoic closing of the southern Tianshan oceanic basin. As a result of the Sinian (latest Proterozoic, younger than 800 Ma) continental extension and rifting process, the Tarim and Yili blocks separated from their parent continent in the Late Cambrian-Ordovician. The southern Tianshan oceanic cr usts between the two blocks subducted northward beneath the southern margin of the Yili block in the Silurian. During the Devonian-Early Carboniferous , the Tarim block rapidly drifted to the north and rotated about 46 degrees clockwise. This process induced the collision of the Yili micro-continent with the eastern segment (present geographical position) of the Tarim conti nent in the Late Devonian, and the southern Tianshan oceanic crust evolved to be a west-facing remnant oceanic basin. During the Late Carboniferous-Ea rly Permian, the Tarim block, located within an almost constant latitude ra nge, rotated about 26 degrees clockwise with respect to the Yili micro-cont inent, which ultimately closed the remnant oceanic basin in a 'scissors-lik e' manner from east to west and completed the Tarim-Yili collision. Subsequ ent A-type subduction of the Tarim continental crust and lithosphere-scale sinistral shearing generated a magmatic are on the southern margin of the T arim-Yili suture zone. The Late Permian-Early Triassic clastics deposited i n a peripheral foreland basin developed above the are. (C) 1999 Elsevier Sc ience B.V. All rights reserved.