Influence Of Preexisting Salt Diapirs On The Structural Characteristics Of Contractional Deformation: Insights From Discrete Element Modeling

The study of salt structures has important guiding significance for oil and gas exploration and production in salt-bearing sedimentary basins.Previous studies have mainly focused on exploring the main driving forces and influencing factors such as syntectonic sedimentation,preexisting faults and preexisting salt diapirs of salt tectonic deformation.However,there is still a lack of systematic research on the geometric properties of preexisting salt diapirs on the later stage shortening deformation.In this thesis,discrete element method is used to systematically investigate the geometric properties of preexisting salt diapirs such as its geometry,depth,width,distance with the shortening boundary and the combination styles of preexisting salt diapirs on the kinematics and evolution of salt-related structures during shortening.The model results show that the preexisting salt diapirs play an important role in kinematics and dynamics of salt-related structures.During shortening,salt bearing structures are prone to plastic flow,local accumulation and thickening,which affect the structural style of the overlying salt layers.The structural styles mainly include reverse faults and fault-related folds,box-folds,salt nappe structures and salt welding structures.The preexisting salt diapirs follow a kinematic evolution pattern.The geometry of preexisting salt diapirs not only controls the developmental morphology and temporal evolution of reverse faults and folds generated within the hanging wall of the reverse faults,but also affects the amplitude,wavelength and symmetry of box-folds formed close to the shortening boundary..The depth(thickness of overlying layer)is important for controlling the growth of diapirs.The width is decisive for the amount of shortening,which can be accommodated by extruded diapirs.The closer to the shortening boudary,the earlier and greater the diapirs can be shortened.The combination style of preexisting salt diapirs has a certain impact on the deformation of overlying salt tectonics.In addition,the reliability of the simulation is further verified by comparing the model results with the typical seismic profiles of salt tectonics in the Tarim Basin and the Zagros fold thrust belt in Iran.