Uplift, exhumation, and deformation in the Chinese Tian Shan

Abstract

The terranes composing the basement of the Tian Shan were originally sutured together during two collisions in Late Devonian-Early Carboniferous and Late Carboniferous-Early Permian time. Since then, the range has repeatedly been uplifted and structurally reactivated, apparently as a result of the collision of island arcs and continental blocks with the southern margin of Asia far to the south of the range. Evidence for these deformational episodes is recorded in the sedimentary histories of the Junggar and Tarim foreland basins to the north and south of the range and by the cooling and exhumation histories of rocks in the interior of the range. Reconnaissance apatite fission-track cooling ages from the Chinese part of the range cluster in three general time periods, latest Paleozoic, late Mesozoic, and late Cenozoic. Latest Paleozoic cooling is recorded at Aksu (east of Kalpin) on the southern flank of the range, at two areas in the central Tian Shan block along the Dushanzi-Kuqa Highway, and by detrital apatites at Kuqa that retain fission-track ages of their sediment source areas. Available 40 Ar/ 39 Ar cooling ages from the range also cluster within this time interval, with very few younger ages. These cooling ages may record exhumation and deformation caused by the second basement suturing collision between the Tarim-central Tian Shan composite block and the north Tian Shan. Apatite data from three areas record late Mesozoic cooling, at Kuqa on the southern flank of the range and at two areas in the central Tian Shan block. Sedimentary sections in the Junggar and Tarim foreland basins contain major unconformities, thick intervals of alluvial conglomerate, and increased subsidence rates between about 140 and 100 Ma. These data may reflect deformation and uplift induced by collision of the Lhasa block with the southern margin of Asia in latest Jurassic-Early Cretaceous time. Large Jurassic intermontane basins are preserved within the interior of the Tian Shan and in conjunction with the fission-track data suggest that the late Mesozoic Tian Shan was subdivided into a complex of generally east-west-trending, structurally controlled subranges and basins.Apatite data from five areas record major late Cenozoic cooling, at sites in the basin-vergent thrust belts on the northern and southern margins of the range, and along the north Tian Shan fault system in the interior of the range. The thrust belts

Late-Paleozoic emplacement and Meso-Cenozoic reactivation of the southern Kazakhstan granitoid basement

“…Due to the closure of the Paleo-Tethys Ocean, several accretion-collision events took place at the southern Eurasian margin resulting in the creation of the Mesozoic Tien Shan (e.g. De Grave et al, 2013;Dumitru et al, 2001;Jolivet, in press;Yang et al, 2013). These events are often grouped as the Cimmerian Orogeny and include a) b) c) (Metelkin et al, 2010(Metelkin et al, , 2012Wilhem et al, 2012 and references therein;Zorin, 1999).…”

“…Evidence for these reactivation episodes is often documented in the cooling histories of the exhumed basement rocks and in the sediments of the intervening basins, but the extent of these reactivation events is still under discussion (e.g. De Dumitru et al, 2001;Glorie and De Grave, in press;Jolivet et al, 2013a,b;Vandoorne et al, 2011;Yang et al, 2015). Due to the closure of the Paleo-Tethys Ocean, several accretion-collision events took place at the southern Eurasian margin resulting in the creation of the Mesozoic Tien Shan (e.g.…”

“…Our results will be placed in a broader thermo-tectonic framework based on available data from studies of e.g. Bullen et al (2001, Glorie et al (2010), Macaulay et al (2014) for the northern Kyrgyz Tien Shan; Dumitru et al (2001), Jolivet et al (2010), Hendrix et al (1992Hendrix et al ( , 1994, Q. Wang et al (2009) for the Chinese Central and Northern Tien Shan; De Grave et al (2007, 2008, 2011b), De Grave and Van den haute (2002); Glorie et al (2012a), Yuan et al (2006) for the southern Altai mountains.…”

“…During the Mesozoic and Cenozoic, parts of the CAOB were periodically reactivated in response to distal tectonic events, with a final (and still active) late Cenozoic shortening phase related to the India-Eurasia collision (e.g. De Dumitru et al, 2001;Jolivet et al, 2010). Hence, as a consequence of the large-scale reactivation of the CAOB, the presentday topography is dominated by intracontinental mountain ranges (mainly consisting of deformed Precambrian and Paleozoic basement) separated by intramontane and foreland basins which are mainly characterized by Meso-Cenozoic sedimentary deposits.…”

Insights on the kinematics of the India‐Eurasia collision from global geodynamic models

“…Additionally, studies of sediments near Mt Everest indicate a marine depositional setting prevailing as late as 34 Ma [Wang et al, 2002], suggesting that suturing was likely diachronous along the margin and that final collision between India and Eurasia occurred much later than India's initial slowdown. Reactivation of the major Altyn Tagh fault by 40 Ma [Liu et al, 2007], strike-slip motion along the Ailao Shan-Red River shear zone by 35 Ma [Leloup et al, 2007[Leloup et al, , 2001] and postcollisional deformation propagating north with shortening and exhumation in the Tian Shan at $25 Ma [Dumitru et al, 2001] suggest an early Paleogene continent-continent collision would require a $20 Myr time lag in regional geological responses. The absence of volcanic activity along southern Lhasa, at least in the late Cretaceous [Chung et al, 2005], also casts doubt on continuous Andean-style subduction in the NeoTethys.…”