Characteristics, timing, and offsets of the middle-southern segment of the western boundary strike-slip fault of the Songliao Basin in Northeast China

As the west boundary fault of the Songliao Basin and the eastern margin of the Da Hinggan Mountains, the Nenjiang-Balihan fault is located in the central part of Northeast China. It is traditionally considered to be a huge deep-seated NNE-striking fault, characterized by a normal fault or detachment fault displacement. The field investigation resulted in the finding of ductile shear zones in the Lingxia and Louzidian areas, the middle and southern sectors of the fault system. The authors conducted measurements of structural elements in the field, micro-structural studies, finite strain measurements, a study on preferred crystal orientations of quartz determined by Electron Back Scatter Diffraction and muscovite 40Ar/39Ar chronology of the deformed rocks in the ductile shear zone. The results show that the deformation features of the Lingxia and Louzidian ductile shear zones are similar, and that they represent one continuous fault, i.e., the middle-southern segment of the Nenjiang-Balihan Fault, which experienced a sinistral strike-slip ductile shearing in the Early Cretaceous (similar to 130 Ma). By measuring the displacement of the Xar Moron River suture and Wolegen Group on both sides of the Nenjiang-Balihan Fault, it is found that the cumulative strike-slip offset of the fault is about 40-50 km.