Late Paleozoic tectonic evolution of the northern West Chinese Tianshan Belt

Abstract

The northern West Chinese Tianshan is divided into three subunits: Carboniferous turbidite, ophiolitic mélange and Yili magmatic arc. Stratigraphical and petrological studies suggest that the turbidite and ophiolitic mélange form a subduction complex. The ophiolitic mélange that forms the North Tianshan suture was a result of intra-oceanic tectonism and subsequent redeposition and deformation during the subduction of the North Tianshan oceanic basin. The Yili arc-type granitoids are constained by single zircon U-Pb radiochronology between 361 and 309 Ma. The first-hand kinematic results on the deformed turbidite suggest that this suture zone was reworked by a Permian ductile dextral strike-slip fault. An evolutionary model of the study area allows three events to be distinguished: 1) Late Devonian to Carboniferous subduction of the oceanic basin below the Yili Block producing Yili magmatic rocks and subduction complex, 2) Late Carboniferous complete closure of this basin, 3) Permian right-lateral strike-slip faulting generating pull-apart basins and alkaline magmatism. A prominent reactivation during the Indo-Eurasia collision provoked the northward thrusting of the Paleozoic units upon the Cenozoic sediments of the Junggar Basin, consequently, hiding the bulk of this Late Paleozoic suture.

Late Paleozoic paleogeographic reconstruction of Western Central Asia based upon paleomagnetic data and its geodynamic implications

“…Dextral criteria can be observed along these faults (Laurent-Charvet et al, 2002;2003;Wang et al, 2006Wang et al, , 2007 and Ar-Ar dating yield ages ranging from 290 Ma to 240 Ma for the deformation (Yin and Nie, 1996;Zhou et al, 2001;Laurent-Charvet et al, 2002, 2003. The center of the best fitting small circle intercepting this curved shear zone is around 50°N, 92°E, with a radius of about 880km.…”

“…North-verging folds and top-to-the north kinematic criteria observed in these series argue for a deformation associated with a south-dipping subduction (Wang et al, 2006). Superimposed Permian dextral strike-slip faults affected the accretionary complex and the magmatic arc as well (Laurent-Charvet et al, 2002, 2003Wang et al, 2006). Post-collisional pull-apart basins, with bimodal magmatism (e.g.…”

“…The boundary between Yili and South Junggar is characterized by a dextral long-lived shear zone called the Chingiz-Alakol-North Tian Shan Shear zone, merging in the Main Tian Shan Shear zone to the east (Zhou et al, 2001;Zhao et al, 2003;Wang et al, 2006Wang et al, , 2007. Dextral criteria can be observed along these faults (Laurent-Charvet et al, 2002;2003;Wang et al, 2006Wang et al, , 2007 and Ar-Ar dating yield ages ranging from 290 Ma to 240 Ma for the deformation (Yin and Nie, 1996;Zhou et al, 2001;Laurent-Charvet et al, 2002, 2003.…”

“…The Junggar Ocean was enclosed in the Kazakhstan orocline extending from Tian Shan to Kazakhstan . Arc magmatism associated with subduction was still active in Kazakhstan, Yili, Bogda Shan and West Junggar, while accretionary wedge developed along the margins (Wang et al, 2006). The Kazakhstan oroclinal bending is marked by a clockwise rotation of North Kazakhstan with respect to Siberia (Grishin et al, 1997 ;Levashova et al, 2003a ;Abrajevitch et al, 2008) and forwards to the closure of this oceanic basin.…”

“…2), which consists of a Devonian to Carboniferous accretionary complex and a volcanic arc, largely exposed in the Bogda Shan (e.g. Wang et al, 2006;Charvet et al, 2007). Accreted rocks are coarse and finegrained turbidite, associated with an ophiolitic mélange.…”