The Geodynamic Modeling Of The NCC Lithosphere Evolution In Jurassic

The thesis takes the North China Craton(NCC) as the main research area.Taking tectonics and geodynamics as the fundamental basic theories,the recently pubilished plate tectonic reconstruction results as the data source, combining the Intraplate deformation details reflected by geological research projects,converting the source data into suitable boundary conditions with the help of both CitcomS and Gplates softwares, we have built a data assimilation geodynamic model on a high performance supercomputing cluster. We want to simulate and reproduce the evolution of NCC lithosphere. Searching for the possible mechanic relationship between the activity of subductions all around, the deformation and any phenomenons.In building the model, we assimilate the thermal structure of both lithosphere and subduction slabs and take the surface kinematic velocity fields which comes from tectonic reconstruction and intraplate deformation reconstruction as the velocity boundary condition.To get the point, we cut two cross sections through Beijing in both North South direction and East West direction, We plot the temperature fields,viscosity fields and the mass fields on the sections to see if the Izanigi subduction zone and the Mongolia Okhotsk subduction zone have anything to do with lithosphere evolution of NCC in Jurassic.Finally, we get conclusions listed as follows:(1)The subduction of Mongolia-Okhotsk subduction zone doesn’t directly influence on the NCC lithosphere evolution.During the early and middle Jurassic,this subduction zone subducts northward in a high angle, down deep under the Siberia craton. The subduction slab may not lead to the instabilities or the destruction of the NCC lithosphere.(2)Izanigi subduction zone subducts in northwest direction under the NCC, the results shows the subduction dip angle,slab morphology and the substitution between the old and new subduction zones may leave instabilities in the lithosphere.(3)During Jurassic, the North China Craton experienced an compressive intraplate deformation process. The cross sections also shows that under this compressive tectonic environment, the NCC lithosphere generally gets thicken, which is consistent with the main idea among the structural geologists.