The Altun Fault: Its Geometry, Nature and Mode of Growth

AbstractThe Altun (or Altyn Tagh) fault displays a geometry of overlapping of linear and arcuate segments and shows strong inhomogeneity in time and space. It is a gigantic fault system with complex mechanical behaviours including thrusting, sinistral strike slip and normal slip. The strike slip and normal slip mainly occurred in the Cretaceous—Cenozoic and Plio‐Quaternary respectively, whereas the thrusting was a deformation event that has played a dominant role since the late Palaeozoic (for a duration of about 305 Ma). The formation of the Altun fault was related to strong inhomogeneous deformation of the massifs on its two sides (in the hinterland of the Altun Mountains contractional deformation predominated and in the Qilian massif thrust propagation was dominant). The fault experienced a dynamic process of successive break‐up and connection of its segments and gradual propagation, which was synchronous with the development of an overstep thrust sequence in the Qilian massif and the uplift of the Qinghai‐Tibet plateau. With southward propagation of the thrust sequence and continued uplift of the plateau, the NE tip of the Altun fault moved in a NE direction, while the SW tip grew in a SW direction.