Altyn Tagh fault

The Altyn Tagh Fault (ATF) is a >1200 km long,active, sinistral (left lateral) strike-slip fault that forms the northwestern boundary of the Tibetan Plateau with the Tarim Basin. It is one of the major sinistral strike-slip structures that together help to accommodate the eastward motion of this zone of thickened crust, relative to the Eurasian Plate. A total displacement of about ~475 km has been estimated for this fault zone since the middle Oligocene, although the amount of displacement, age of initiation and slip rate are disputed.

The Tibetan Plateau is an area of thickened continental crust, a result of the ongoing collision of the Indo-Australian Plate with the Eurasian Plate. The way in which this zone accommodates the collision remains unclear with two end-member models being proposed. The first regards the crust as being made up of a mosaic of strong blocks separated by weak fault zones, the 'microplate' model. The second regards the deformation as being continuous within the mid to lower crust, the 'continuum' model. The change in width of the deformed zone along the collisional belt, with the narrow zone of western Tibet compared to the main part of the Tibetan Plateau, is explained as either lateral escape to the east along the Altyn Tagh and Karakorum faults in the microplate model or as the effect of the rigid Tarim Basin block causing heterogeneous deformation within a generally weaker lithosphere in the continuum model. The rate of displacement along the major fault zones such as the Altyn Tagh and Kunlun faults compared to the degree of distributed deformation of the intervening crust is critical to discriminating between these two models.

The Altyn Tagh Fault extends for at least 1,500 km and possibly for as much as 2,500 km from the West Kunlun thrust zone in the southwest to the edge of the Qilian Mountains in the northeast (and possibly well beyond). It is divided into three main sections: southwestern, central and northeastern. There is one major splay fault, the North Altyn Fault. The main active fault trace of the ATF lies within a zone of secondary structures that is about 100 km wide in the central section.

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