碳酸盐团簇同位素约束下塔中隆起奥陶系热历史

碳酸盐团簇同位素是近年来兴起的一种新型古温标, 其有效地解决了碳酸盐岩沉积盆地缺乏常用古温标的现状, 对于沉积盆地热史恢复具有重要意义.本文采集了塔中地区奥陶系碳酸盐岩钻井取芯样品, 利用一阶近似模型模拟了塔中隆起碳酸盐团簇同位素温度(T_Δ47)热演化路径, 并结合等效镜质体反射率约束了塔中隆起的热历史.塔中隆起大地热流自奥陶纪到现今总体呈降低趋势, 自60~70 mW·m^-2降低至40~50 mW·m^-2, 二叠纪由于火成岩入侵造成热流短暂升高至60~70 mW·m^-2.模拟结果认为, 北部斜坡带及潜山构造带受火成岩影响显著, 北部斜坡带及潜山构造带在二叠纪最高温度分别达到160~170 ℃及180~190 ℃; 而塔中南缘未受影响, 中生代或者现今为最高温度130~140 ℃.总的来说, 碳酸盐团簇同位素在热史领域的研究目前还处于探索阶段, 未来有望在重排规律、T_Δ47影响因素以及模型理论方面有待进一步完善, 团簇同位素也将在热史领域的研究中产生愈加重大的影响力.

Thermal history of the Ordovician in the Tazhong uplift under the constraint of carbonate clumped isotope

Carbonate clumped isotope is a new type of geologic thermometer that has developed in recent years. It can effectively solve the problem that the carbonate sedimentary basins lack commonly used geologic thermometer. Therefore, it takes an important part in the thermal history reconstruction of sedimentary basins. This paper collects the drill cores of Ordovician carbonate rocks in the Tazhong uplift. The thermal evolution paths of the carbonate clumped isotope temperature (TΔ47) in the Tazhong uplift are simulated using the first order rate approximation model, and the thermal history of the Tazhong uplift is constrained by the carbonate clumped isotope as well as the equivalent vitrinite reflectance. From this study, it shows that the heat flow in the Tazhong uplift has generally decreased from 60~70 mW·m-2 in the Ordovician to 40~50 mW·m-2 in the present. During the Permian, the heat flow peaked briefly to 60~70 mW·m-2 due to the intrusion of igneous rocks. According to the simulation, the Lower Ordovician in the northern slope belt and the Middle Ordovician in the buried hill structural belt reached the temperature peaks at 160~170 ℃ and 180~190 ℃ in the Permian, respectively. While the southern margin of Tazhong uplift only reached the temperature peak at 130~140 ℃ in the Mesozoic or the present. All of these simulation results reveal that the northern slope belt and the buried hill belt have been significantly affected by the intrusion of igneous rocks, but the southern margin of Tazhong uplift. In general, the research of carbonate clumped isotopes in the field of thermal history is still in an exploratory stage, and it is expected to be further improved in terms of carbonate clumped isotopic rearrangement laws, TΔ47 influencing factors and model theory in the future. The application of carbonate clumped isotope will have an increasingly significant impact in the field of thermal history research.