Deformation characteristics and formation mechanism of NNE-trending strike-slip faults in Tazhong Uplift

In this study, the correlation method of structural factors and structural analysis were used to determine the formation mechanism of NNE-trending strike-slip faults in the Tazhong Uplift. The interpretation of 2D and 3D seismic data revealed deformation characteristics of the NNE-striking faults and determined their formation mechanism. NNE-trending strike-slip faults exhibit vertical superposition of compresso-shear faults and tenso-shear faults in seismic profiles. They have experienced two stages of activities:the late Ordovician compresso-shear faulting and the late Silurian-middle Devonian tenso-shear faulting. The formation of the NNE-trending strike-slip faults was controlled by the pre-existing basement weak zone and the evolution of the orogenic belts around Tarim plate. At the end of Middle Ordovician, a NS-trending compressive stress was generated by the subduction and closure of the ocean basin on the south margin of Tarim plate, and it acted on the NE-trending basement weak zone, resulting in the formation of NNE-trending strike-slip faults.Meanwhile, the compressive stress from the northwest margin of Tarim plate vertically acted on the NNE-striking strike-slip fault, leading to the compresso-shear deformation. In late Silurianmiddle Devonian period, the NS-trending compressive stress continually acted on the strike-slip faults, resulting in continued strike-slip deformation. Moreover, the extensional stress from the northwest margin of Tarim plate vertically acted on the NNEstriking strike-slip fault, leading to the tenso-shar deformation.