方解石原位U-Pb测年结合磷灰石裂变径迹方法约束鄂尔多斯盆地西南部构造演化  

Tectonic evolution analysis constrained jointly by in-situ calcite U-Pb dating and apatite fission track for southwestern Ordos Basin

作　　者：杨鹏 任战利[3,4] Jianxin Zhao[5] Ai Duc Nguyen[5] Yuexing Feng 祁凯 王琨 Yang Pang;Ren Zhanli;Jianxin Zhao;Ai Duc Nguyen;Yuexing Feng;Qi Kai;Wang Kun(State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing 102206,China;Key Laboratory of Petroleum Accumulation Mechanisms,SINOPEC,Wuxi,Jiangsu 214216,China;State Key Laboratory of Continental Dynamics,Northwest University,Xi'an,Shaanxi 710069,China;Department of Geology,Northwest University,Xi'an,Shaanxi 710069,China;Radiogenic Isotope Facility,School of Earth and Environmental Sciences,The University of Queensland,Brisbane,QLD 4072,Australia)

机构地区：[1]页岩油气富集机理与有效开发国家重点实验室,北京102206 [2]中国石化油气成藏重点实验室,江苏无锡214126 [3]西北大学大陆动力学国家重点实验室,陕西西安710069 [4]西北大学地质学系,陕西西安710069 [5]Radiogenic Isotope Facility,School of Earth and Environmental Sciences,The University of Queensland,Brisbane,QLD 4072,Australia

出　　处：《石油与天然气地质》2021年第5期1189-1201,共13页Oil & Gas Geology

基　　金：国家自然科学基金项目(41630312,42102164);中国石化油气成藏重点实验室开放基金项目(KL21033);国家重点研发计划项目(2017YFC0603106);国家科技重大专项(2017ZX05005002-008)。

摘　　要：鄂尔多斯盆地下古生界油气资源丰富,盆地西南部下古生界海相碳酸盐岩地层沉积厚度大、有机质丰度较高,烃源岩热演化达到过成熟生干气阶段,但是构造演化缺乏深入研究,早期构造事件具体时限是一个亟待解决的关键科学问题。在详细的野外调查、显微结构特征、原位微量元素分析和区域沉积-埋藏演化历史的约束下,结合下古生界碳酸盐岩地层及其断裂破碎带内次生方解石原位U-Pb测年与磷灰石裂变径迹时间-温度曲线模拟结果,揭示了鄂尔多斯盆地西南部晚奥陶世、晚三叠世、晚侏罗世和早白垩世末期—新生代以来的4期构造事件。结果表明研究区晚奥陶世(452±13)Ma存在一期热液改造事件,可能与加里东期原特提斯洋俯冲闭合密切相关;印支期(214±22)Ma的断裂活动是引起区域构造-热事件的重要原因,印支期构造事件规模有限;燕山期和喜马拉雅期构造活动强烈,造成鄂尔多斯盆地西南部大幅度隆升和强烈剥蚀。盆地西南部多阶段复杂的构造演化历史导致油气保存条件破坏严重,对寻找古生界天然气藏不利,应重视盆地天然气保存条件的研究。研究结果对鄂尔多斯盆地古生界油气勘探工作有重要指导意义。将低温热年代学与断裂带方解石原位U-Pb定年相结合分析构造演化的新思路,为解析复杂叠合盆地盆缘带构造演化及其后期改造过程的研究提供了新途径。The lower Paleozoic strata of Ordos Basin is rich in oil and gas resources.The Lower Paleozoic marine carbonate in the southwestern Ordos Basin is characterized by large thickness and high abundance of organic matter.The source rocks are in dry gas window.However,the tectonic evolution has not been well evaluated.The timing of the earlier tectonic events is a key scientific problem and needs to be addressed timely.In this study,under the constraints of detailed field investigations,microstructure characteristics,in-situ trace element analysis and regional deposition-burial evolution history,the secondary calcite in-situ U-Pb dating is combined with apatite fission-track time-temperature simulation curves of the Lower Paleozoic carbonate strata and its fault facture zone to reveal four tectonic events including the Late Ordovician,Late Triassic,Late Jurassic and end of the Early Cretaceous-Cenozoic.A hydrothermal event occurred at the Late Ordovician 452±13 Ma,which might be linked to the subduction and closure of the Proto-Tethys Ocean during the Caledonian period.A limited Indosinian tectono-thermal event occurred at 214±22 Ma,which might be caused by the regional fault movement.The intense tectonic activities during the Yanshanian and Himalayan periods induced a strong uplift and denudation.The southwestern Ordos Basin experienced multi-stage complex tectonic evolution and the caprock was seriously damaged,leaving rather unfavorable preservation conditions for hydrocarbon.This study conducts a novel tectonic evolution analysis by combining low-temperature thermochronology with in-situ U-Pb dating of fault-related calcite,providing a new way to analyze tectonic evolution and later transformation process at the margin of complex superimposed basins.

关 键 词：方解石U-Pb定年 裂变径迹 构造演化 下古生界 鄂尔多斯盆地 

分 类 号：TE121.2[石油与天然气工程—油气勘探]