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以四川盆地东南缘武隆地区为例,系统采集下古生界—中生界层系样品并进行镜质体反射率测试,在区域构造沉积演化史分析的基础上,对镜质体反射率异常带进行划分与成因分析,分别利用镜质体反射率梯度法及最大埋藏温度法恢复各层系地质历史过程中地温梯度及最大埋藏温度。四川盆地东南缘下古生界—中生界存在4个镜质体反射率异常带,从上至下分别为上三叠统须家河组底部异常高值带、中二叠统栖霞组顶部—上二叠统龙潭组异常高值带、五峰组—龙马溪组底部页岩段异常高值带及其以下层系异常低值带,形成机制分别为油气运移带来的热流体活动、晚海西期峨眉玄武岩喷发、热液流体屏蔽层底部增温及地质流体高压封存箱。利用最大埋藏温度法恢复的古地温具有更高的可信度,恢复结果显示:受地质流体封存箱控制,下古生界地温梯度变化较大,寒武系地温梯度总体较低,志留系平均地温梯度可达41.47℃/km,上古生界—中生界古地温梯度为25.10~28.01℃/km,平均为26.18℃/km,大地热流背景值为66.78mW/m2。
Taking the Wulong area in the southeastern margin of Sichuan Basin as an example, samples of Paleozoic-Mesozoic strata were collected and tested for vitrinite reflectance. Based on the analysis of regional structural sedimentary evolution history, the reflectance of vitrinite The anomalous zones were divided and genesis analyzed. The geothermal gradients and the maximum burial temperature during the geological history of each strata were restored by the vitrinite reflectance gradient method and the maximum burial temperature method respectively. There are four vitrinite reflectance anomalies in the Lower Paleozoic-Mesozoic in the southeastern margin of the Sichuan Basin. From the top to the bottom are abnormally high values at the bottom of the Upper Triassic Xujiahe Formation and the top of the Middle Permian Qixia Formation - the anomaly high value zone of the Upper Permian Longtan Formation, the anomalous high value zone of the shale section of the bottom of the Wufeng Formation-Longmaxi Formation and the anomalous low value zones below it, and the formation mechanisms are respectively the thermal fluid activities brought by hydrocarbon migration, Late Hercynian Emei basalt eruption, the bottom of the hydrothermal fluid shield warming and high-pressure geological storage tank. The restoration of paleo-geothermal temperature using the method of maximum burial temperature shows that the geothermal fluid temperature gradient of the Lower Paleozoic varies greatly under the control of the geofluidic enclosure, and the geothermal gradient of the Cambrian is generally low, The average geothermal gradient is 41.47 ℃ / km. The Paleozoic-Mesozoic paleo-geothermal gradient is 25.10 ~ 28.01 ℃ / km with an average of 26.18 ℃ / km and the background value of geothermal flow is 66.78mW / m2.