Application of the Finite Element Numerical Simulation Method to the Study on Formation Mechanism of the Central Inverted Structure Zone, Xihu Depression

On the basis of study on regional geological settings for the formation of the central inverted structure zone in Xihu Depression, the finite element numerical simulation method has been used for designing the reasonable finite element model to analyze the stress field and boundary conditions, and simulate the tectonic evolution history of the central inverted structure zone in Xihu Depression, and make cleat about its genetic model. The tectonic evolution of the central inverted structure zone in Xihu Depression can be divided into three stages. (1) The initial formation stage of anticline belt(late Eocene at about 35 Ma). During this stage, under the control of Pacific plate subduction in the direction of NWW-SEE, two anticline belts with different height formed in northern and central regions in Xihu Depression, namely "A" anticline belt and "B" anticline belt; (2) The growth stage of anticline belt(late Oligocene at about 25 Ma). During this stage, by the continuous subduction of Pacific plate, "A" anticline belt in northern part started to expand northward and uplifted continuously until to Fujiang lower uplift, and the area of "A" anticline belt has been enlarged continuously. While "B" anticline belt in central started to expand southward and uplifted continuously until to southern region of Xihu depression,then "C" anticline belt and "D" anticline belt developed; (3) The final formation stage of anticline belt(late Miocene at about 10 Ma). During this stage, "A" anticline belt in northern stopped expanding but uplifted continuously, and the uplift height was larger than other anticline belts. While, "B","C" and "D" anticline belt in central and southern parts connected to each other, and a single large anticline belt formed, thus the central inverted structure zone was finally shaped during this stage.