Controls of a strike-slip fault system on the tectonic inversion of the Mahu depression at the northwestern margin of the Junggar Basin, NW China

The marginal fault system, which is represented by the Hong-Che (Hongshanzui-Chepaizi), Ke-Bai (Karamay-Baikouquan), and Wu-Xia (Wuerhe-Xiazijie) sub-systems and developed in the northwestern margin of the Junggar Basin, NW China, is a key factor affecting the development characteristics of the Permian-Triassic strata and controlling the hydrocarbon accumulation in the area. In this study, based on the latest two-dimensional and three-dimensional seismic exploration data, regional geological background, and previous research results, the attributes and timing of this structural belt of the NW margin as well as the basin type related to it are clarified. The result shows that the above marginal fault system has dextral strike-slip features and is characterized by a high-angle master fault, branch faults, and short-axis plunging anticlines in an en echelon arrangement. The tectonic deformation is classified into two main periods: late Permian tectonic inversion and late Triassic reactivation. It is found that the late Permian tectonic inversion led to the migration of the depocenter in the Mahu Depression and was induced by the counterclockwise rotation of the Junggar block and West Junggar area relative to the western part of the Chingiz range in the late Paleozoic. The nose structures, fault blocks, and en echelon anticlines derived from the relevant thrust faulting and folding may account for the development of the main structural traps, which play an important role in the hydrocarbon accumulation in the NW margin of the Junggar Basin.