Thermal History Reconstruction Of Marine Sedimentary Basins Using Carbonate Clumped Isotopes

Carbonate clumped isotope is a new type of geologic thermometer that has emerged in recent years.It effectively solves the lack of common geologic thermometer in marine sedimentary basins and is of great significance for thermal history reconstruction of sedimentary basins.In this paper,Ordovician carbonate rock samples were collected in the Tazhong area,and the thermal evolution models of carbonate clumped isotope temperature(TΔ₄₇)of limestone,dolomite and carbonate rocks with different contents of lime and dolomite were explored.The first order rate approximation model is used to simulate the thermal evolution history of TΔ₄₇ of the typical single wells in the Tazhong uplift,and the current TΔ₄₇ simulated value is fitted with the measured value,so as to further reconstruct the thermal history of the Tazhong uplift.The heat flow in the Tazhong area has generally decreased from the Cambrian to the present.The heat flow of the Cambrian decreased from about 60-70 m W/m² to the present about 40-50 m W/m².During the Permian,the heat flow briefly increased to 60-70m W/m² due to the intrusion of igneous rocks.Through the carbonate clumped isotope simulation,the slope belt in the north and buried hill belt of Tazhong were significantly affected by igneous rock intrusion.It was hardly affected by the invasion of Permian igneous rocks,and the highest temperature in the geological history is about 120-140℃.The thermal evolution of the Tazhong uplift has a significant impact on the maturity evolution of the source rocks.The Ordovician source rocks in the Late Ordovician has entered a low maturity stage.The northern slope belt and buried hill belt are significantly affected by the Permian igneous rocks.The maturity evolves rapidly,entering high maturity in the Permian,and entering the gas generation stage in the Triassic-Jurassic,and then the maturity changes little;the southern margin of Tazhong is less affected by igneous rocks,and it is in the middle-high maturity stage until now.In general,the research of carbonate clumped isotopes in the field of thermal history is still in the exploratory stage.In the future,the reordering kinetic law,TΔ₄₇ influencing factors and the model theory all need to be further improved.Clumped isotopes used in the field of thermal history will have an increasingly significant impact on research.