Tectonic-Thermal History Reconstruction of Ordovician in the Weibei Uplift of Ordos Basin
Tectonic-Thermal History Reconstruction of Ordovician in the Weibei Uplift of Ordos Basin
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发表时间：
2014
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通讯作者：
Ren Zhanl
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作者：
Ren Zhanl
鄂尔多斯盆地渭北隆起具有独特的构造位置和复杂的演化历史，该区下古生界奥陶系碳酸盐岩有机质丰度高，是天然气勘探的最有利地区，但由于奥陶系碳酸盐岩缺乏有效的热指标，根据大量实测的奥陶系碳酸盐岩沥青反射率数据，结合其它热指标数据，如镜质体反射率、上覆古生界和中生界地层中的磷灰石和锆石裂变径迹，恢复了渭北隆起的构造-热演化史，模拟结果表明，古生界奥陶系热演化程度北高西低，南低东低，奥陶系等效镜质体反射率在超热演化阶段普遍大于2.00%，古生界奥陶系镜质体反射率在超热演化阶段普遍大于2.00%，古生界奥陶系镜质体反射率在超热演化阶段普遍大于2.00%。磷灰石裂变径迹资料表明，渭北隆起隆升冷却时间具有南早北晚的特点，奥陶系-下二叠统隆升冷却时间早南部约102~107 Ma，北部约65 Ma开始隆升，渭北隆起的隆升-冷却时间开始于早白垩世晚期（102~107 Ma），热演化史研究结果表明，奥陶纪地层在早白垩世早期经历了最高古地温白垩纪发生构造热事件，古地温梯度达4.60℃/100 m，早白垩世是奥陶系烃源岩的主要生气期，主生气期主要受构造控制，研究渭北隆起奥陶系的热演化程度和热演化史对研究天然气成藏条件具有重要意义天然气勘探。
Weibei uplift in Ordos Basin has a unique tectonic position and complex evolution history.In this area,the organic matter abundance of carbonate rocks in Ordovician of Lower Paleozoic is high and it is the most favorable area for natural gas exploration.However,due to the lack of effective thermal indicators in carbonate rocks of Ordovician,it is difficult to determine the thermal evolution degree and reconstruction thermal history.Based on a number of measured bitumen reflectance data in carbonate rocks of Ordovician and combined with other thermal indicators data such as vitrinite reflectance,apatite and zircon fission track in the overlying Paleozoic and Mesozoic strata,this paper reconstructs the tectonic-thermal history of Weibei uplift.The simulation results show that the thermal evolution degree of Paleozoic Ordovician is high in the north and west and low in south and east.The equivalent vitrinite reflectance of Ordovician is generally greater than 2.00%in the stage of over-mature dry gas.The apatite fission track data indicate that the uplift-cooling time of Weibei Uplift is characteristic of early in the south and late in the north.The uplift-cooling time of Ordovician-lower Permian is early(about 102~107 Ma)in the southern area,started to uplift in the north around 65 Ma,with the main period of uplift in 40 Ma.The uplift-cooling time of Weibei uplift began at the late Early Cretaceous(102~107 Ma),rapid overall uplift happened around40 Ma.The thermal evolution history study results show that the Ordovician strata experienced maximum Paleotemperature in the Early Cretaceous which occurred a tectonic-thermal event,and paleogeothermal gradient reached 4.60℃/100 m.The early Cretaceous was the main gas generation period of Ordovician source rocks,and main gas generation period was controlled mainly by tectonic-thermal event of early Cretaceous.The research on thermal evolution degree and history of the Ordovician in the Weibei uplift has an important significance in the study of gas accumulation conditions and natural gas exploration.