Evidence for Mesozoic shear along the western Kunlun and Altyn‐Tagh fault, northern Tibet (China)

Abstract

The strike‐slip faults of north Tibet accommodate part of the Cenozoic convergence between India and Asia. Along the Karakax valley south of Yecheng and near the Xidatan trough south of Golmud, the active traces of the Altyn‐Tagh and Kunlun faults follow narrow belts of metamorphic rocks. The deformation recorded in those mylonites is sinistral strike‐slip. Rb/Sr and 40Ar/39Ar ages of deformation from syntectonic fabrics formed at 350–400°C 120 Ma. Argon loss suggests that deformation was associated to a 250–300°C thermal pulse that lasted 5–20 Ma after the onset of movement. Unroofing occurred much later, around 25 Ma when sudden cooling suggests a component of thrusting or more likely normal faulting. The Cretaceous shear may be related to collision between the Qiantang and the Lhasa blocks. The Karakax and Xidatan shear zones may have formed a unique, continuous boundary in the Cretaceous, which was later reused by the Tertiary strike‐slip faults, leading to potentially calculable offsets along the Altyn‐Tagh fault.

Geochronology of the initiation and displacement of the Altyn Strike-Slip Fault, western China

“…Recently there have been increasing reports of isotopic age data from the Altyn Tagh area Guo et al, 1999;Sobel and Arnaud, 1999;Zhang et al, 2000;Chen et al, 2001;Jolivet et al, 2001;Liu et al, 2001b;Sobel et al, 2001;Wang et al, 2001;Chen et al, 2002bChen et al, , 2003Li et al, 2002;Arnaud et al, 2003;Cowgill et al, 2003;Yue et al, 2004) (Figs. 1 and 2).…”

“…In recent years the Altyn Strike-Slip Fault (ASSF) has been become a hot-spot for Tibetan Plateau geological research. A large amount of research work related to the ASSF have been carried out, predominantly dealing with radiometric isotope age dating (Liu et al, , 2001bSobel and Arnaud, 1999;Zhang et al, 2000Chen et al, 2001Chen et al, , 2002bChen et al, , 2003Jolivet et al, 2001;Sobel et al, 2001;Wang et al, 2001;Li et al, 2002;Cowgill et al, 2003;Yue et al, 2004) and the reconstruction of tectonic belts on both sides of the ASSF and estimations of the amount of offset (Cui et al, 1997;Guo et al, 1999;Cowgill et al, 2000;Delville et al, 2001;Meng et al, 2001;Sobel et al, 2001;Yang et al, 2001;Yue et al, 2001;Ge et al, 2002;Arnaud et al, 2003;Jolivet et al, 2003). An estimate of cumulated offset 350-400 km along the ASSF has been accepted by most of researchers, but the age of initiation of the ASSF is still the subject of dissention.…”

Cooling history and tectonic exhumation stages of the south-central Tibetan Plateau (China): Constrained by 40Ar/39Ar and apatite fission track thermochronology

“…K-feldspar cooling ages and muscovite-biotite 40 Ar/ 39 Ar ages from granitic intrusions in this belt, indicate that a rapid cooling event also occurred at this time. Regionally, in the Qiangtang and Lhasa blocks, in the Kunlun Orogenic Belt (Mock et al, 1999;Arnaud et al, 2003), in the Altyn Tagh fault system (Wang et al, 2005), as well as along the Bangong-Nujiang Suture Zone, Jurassic sediments were folded, and in the Cretaceous faulted sedimentary basins opened up. Meanwhile, southward-directed thrusting developed .…”

A short-lived but significant Mongol–Okhotsk collisional orogeny in latest Jurassic–earliest Cretaceous

“…To the east of these faults, a series of sinistral strike-slip faults developed in East Asia and the Tibet Plateau (Fig. 11C), such as the western segment of the Altyn-Tagh Fault (ATF) (Arnaud et al, 2003), the eastern segment of the Altyn-Tagh Fault (ATF) Tang et al, 2012), North Zuunbayan Fault (NZF) (Johnson, 2004), Nenjiang-Balihan Fault (NBF) (Han et al, 2012), strike-slip faults in the Qinling-Dabie orogen Ratschbacher et al, 2000;Wang et al, 2003), and the Kunlun Fault (Arnaud et al, 2003). In eastern China, eastern Mongolia, and Transbaikalia, regional strike-slip faulting triggered gravitational collapse of upper crust thickened during the SiberiaAmuria collision, resulting in the formation of rift basins (e.g., Traynor and Sladen, 1995;Zorin, 1999;Graham et al, 2001;Johnson et al, 2001;Meng, 2003) and metamorphic core complexes (e.g., Zorin, 1999;Donskaya et al, 2008;Wang et al, 2011;Daoudene et al, 2013) (Fig.…”