The transformation of the Altyn Tagh fault in its intersections with the Qilian Shan and Eastern Kunlun Shan explained by triple junction analysis

The Altyn Tagh fault (ATF) is a large lithospheric left-lateral strike-slip fault, marking the northwestern boundary of the Tibetan Plateau. Understanding the tectonic history of the ATF provides insights into the growth pattern of the Tibetan plateau, as well as the deformation mechanism of complex fault systems.

However, despite numerous research efforts, the deformation of the ATF is still a subject of discussion, especially its interaction with the other two major faults in the northeast Tibetan Plateau: the strike-slip Eastern Kunlun fault and the Qilian Shan fold-thrust belt. The triple junction analysis has proven successful in explaining the spatial-temporal variations of fault kinematics. Therefore, here we use the principles of triple junctions to discuss the transformation of the ATF in its intersections with the Qilian Shan and Eastern Kunlun Shan, with the assistance of geological evidence from fieldwork and satellite images. We propose that the initiation of the left-lateral motion of the Eastern Kunlun fault led to an FFF triple junction in the former western end of the ATF. Meanwhile, the deformation on the southern Qilian Shan forms an TFF triple junction with the splays of the ATF. The unstable triple junctions will trigger the growth of the ATF and complicate the deformation the Qilian Shan and the Eastern Kunlun Shan. Our research firstly applies triple junction principles to both ends of the ATF, and presents a new model of the evolution of the ATF and its surrounding orogens, shedding lights on the history of Tibetan Plateau.