Tectonic-thermal Evolution Modeling In Superposition Basin With The JiangHan Basin As An Example

Currently, most of the tectonic- thermal evolution researches for sedimentary basins in China are focused on the rift basins in the east of China. Jianghan basin is a superposed basin formed by multiple extensional and compressional tectonic deformation on Pre-Sinian crystallized continental crust. The researches of tectonic-thermal evolution of Jianghan basin are few,and most of them are focused on Cenozoic extensional rift basin stage, or used palaeo-temperature indicator method.Tectonic-thermal evolution modeling, witch are based on geodynamics, is useful to study the thermal history of sedimentary basins based on the thermal structure of the Lithosphere scale. The method can combine the effects of deep-dynamics, the tectonic activity, rapid sedimentation and erosion, etc.In this paper, tectonic modeling of four geological profiles (Yihong , Yisui , Jianying , Linhuang) in Jianghan Basin were carried out based on geodynamics setting. From late Indo-Chinese epoch to mid-Yanshanian epoch,Jianghan basin was deformed intensively by compressional tectonic activity. The shortening rate was 23.9% in the central region, and 25.9% in the south. After late-Yanshanian, Jianghan basin entered extensional period and deposited thick sedimentary strata.Long time series models of tectonic-thermal evolution about Jianghan Basin were set up by strain rate method. The basal heat flow densites and temperature fields of Yihong, Yisui, Jianying profiles were inversed for different historical stages, which are important for maturity studies of source rocks in Jianghan Basin. The results of the thermal evolution modeling showed that HF (heat flow) increased slowly before 390Ma from about 57mW/m2 at 570Ma, decreased to 55mW/m2 at 240Ma, and increased rapidly from 240Ma to 159Ma, when the heat flow achieved the historical maximum value at the northern area of JiangHan basin. Subsequently, it changed significantly and showed different regional characteristics. The method combines the thermal model of the lithosphere scale and that of the basin scale. The process flow for modeling tectonic-thermal evolution is established for multi-period extensional and compressional tectonic cycles, which provides a new way for study of the thermal history of pre-Cenozoic marine facies sedimentary basins in China.