Analysis On The Tectonic Event And Palaeo-geothermal Feature Of Yanshanian In The Northern Junggar Basin

The tectonic thermal evolution history of northern margin of junggar basin is always a hot field in the research of the oil and gas exploration, but there are many controversies about tectonic event and palaeo-geothermal feature. The northern region in junggar basin where the tectonic event is relatively week is resaerched. Based on regional geologic structure and unconformity tectonic events, by using methods of tectonic thermal chronology analysis, thermal history modeling and vitrinite reflectance (Ro), the peak age distribution of the tectonic thermal events and palaeogeothermal field characteristics in the middle of Yanshanian is analyzed.(1) By analysis regional geological structure and sedimentary built, the layer tectonic sequence is divided into four periods of Hercynian, Indosinian, Yanshanian and Himalayan, and corresponding nine sublayer. By comparative analysis characteristic of three tectonic sublayer of Yanshanian, the Shishugou formation of Yanshanian has relative activities tectonic sedimentary build composition.(2) Through the field of outcrop, seismic profiles and unconformity tectonic events distribute in the middle of Yanshanian, we introduced the tectonic event characteristics of Yanshanian in Junggar Basin. It shows that the late Jurassic in the middle of Yanshanian experienced significant structural deformation unconformity events.(3) Through the zircon U-Pb dating and its spectrum analysis,we abtained the170 Ma±and 140 Ma±peak age, it shows there were existed a magma activity in the middle of Yanshanian,it implies in the northern of Junggar Basin in this period has a significant structural hydrothermal activity background.(4) zircon and apatite fission track (FT) analysis and its statistical distribution characteristics shows the tectonic thermal events in the middle of Yanshanian happens in 160Ma,130Ma and 90Ma. It also shows that the tectonic uplift deformation function in Junggar Basin mainly happened in the middle of Yanshanian in 160-90Ma. (5) Through the sandstone samples of Mesozoic AFT thermal history simulation and fluid inclusions (Fl) and Vitrinite reflectance (Ro) analysis, thinks research area exists tectonic thermal events in late Jurassic and the early cretaceous of the middle Yanshanian, the ancient geothermal gradient is mainly distributed in the 3.5 to 4.0℃/100m, average closer to 3.7℃/100m, shows high ancient geothermal field characteristic.