Difference of shortening strain for the crustal deformation model in the eastern and western Qaidam Basin and their implications, northern Tibetan Plateau, China

Abstract

To recognize the differences in the west–east crustal deformation model of the Qaidam Basin, we presented the shortening amount of each fold and fault along 12 sections. According to the eastward weakening trend of shortening strain in the southwestern part of the basin and the non‐continuous trend in the northeastern part of the basin, the Qaidam Basin can be divided by a new line into the western Qaidam Basin (WQB) and the eastern Qaidam Basin (EQB). The WQB is characterized by a maximum shortening strain of 25%, transpressional structures, and crust–mantle decoupling, which is possibly weakened by the eastward extension of the crust–mantle mix zone caused by upwelling material along the Altyn Tagh Fault (ATF). In contrast, the EQB is characterized by a minimum shortening strain of 2%, pure thrust boundary faults, and gentle folds, which is defined as a rigid craton basin. The crust–mantle mix zone beneath ATF and the low‐velocity zone beneath the eastern Kunlun Shan show the limited impact of the lithospheric weakening on the EQB. The Miocene reorganization of the ATF is the key tectonic event that accounts for the differences in the east–west crustal deformation model of the Qaidam Basin, as it weakened the lithosphere and facilitated the transpressional structures of the WQB. The WQB was originally a rigid craton basin like the EQB, but it became a destabilized craton after the a forementioned tectonic event.