Tectonic Thermal Evolution Characteristics Of The Datong Basin

This paper mainly studies the characteristics of tectonic thermal evolution in Datong basin since the Carboniferous-Permian period.In the process of research,through field observation,data collection and literature research,the tectonic background,stratigraphic deposits,faults and magmatic activities,geothermal field changes and other characteristics of the study area are gradually clarified and sorted out.Then,basin simulation technology is used to restore the burial of Datong basin and its western Datong coal basin.The tectonic evolution characteristics of Datong basin are analyzed by comparing the burial history of the two basins and combining the balanced profile technique.Finally,the thermal evolution process of Datong basin is restored by the data of the burial history and the geothermal field of the basin.Since the Carboniferous-Permian,there have been three uplift and denudation events in Datong basin,which occurred in the late Indosinian,late Yanshanian and Himalayan periods.The denudation rates of the three uplift events are 111.35m/Ma,105.15 m/Ma and 14.28 m/Ma,respectively.Rapid deposition of Datong Basin since Neogene.The maximum deposition thickness of the Huairen block depression is over 1900 m,and the maximum deposition rate is over 370m/Ma.The maximum deposition thickness of the Housuo block depression is over 3000 m and the maximum deposition rate is over 575.2m/Ma.The Indosinian and previous tectonic activities had little influence on the formation of the basin,but the basin reached a deeper depth before the Indosinian uplift,and the source rocks reached a low maturity stage.The Indosinian played a decisive role in the thermal evolution of the basin.The folds and faults produced by strong Yanshanian activities are of great significance to the formation of Datong basin,but at the same time,they also resulted in the loss of Carboniferous-Permian source rock strata in Datong basin.The depositional depth of Yanshanian period and the activity of Kouquan fault zone have little influence on the overall thermal evolution of the basin.The change of tectonic stress field in Himalayan period directly led to the formation of Datong Cenozoic fault basin.The rapid subsidence of Datong basin since Neogene can reach 100 ?and 150 ? near the sedimentary centers of the Huairen block depression and the Housuo block depression,respectively,which can promote the local thermal evolution of the basin.Through thermal evolution simulation technology,the thermal evolution of Paleozoic source rocks near well DY1 is restored.It is found that the normal burial depth of Paleozoic source rocks is far less than the condition of gas generation.Combined with the tectonic evolution and magmatic activity of the basin,it is presumed that magmatic activity resulted in abnormal thermal evolution of source rocks near well DY1.