| 青藏高原东缘新生代早期古应力环境:来自四川盆地西南缘磁组构的记录 |
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| 引用本文： | 张帅,田云涛,田野,刘一珉,唐苑,秦咏辉,颜照坤,李仕虎,沈中山,张增杰.青藏高原东缘新生代早期古应力环境:来自四川盆地西南缘磁组构的记录[J].地球物理学报,2021,64(5):1643-1653. |
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| 作者姓名： | 张帅 田云涛 田野 刘一珉 唐苑 秦咏辉 颜照坤 李仕虎 沈中山 张增杰 |
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| 作者单位： | 中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广州 510275;中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广州 510275;南方海洋科学与工程广东省实验室(珠海),广东珠海519082;东华理工大学核资源与环境国家重点实验室,南昌 330013;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京 100029 |
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| 基金项目： | 国家自然科学基金项目(417772211,41888101);广东省引进人才创新创业团队(2016ZT06N331)联合资助. |
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| 摘 要： | 四川盆地西南缘紧邻龙门山褶皱冲断带(青藏高原东边界)南段.该地区的新生代早期红层沉积记录了青藏高原东缘的隆升历史及构造演变.本研究选取四川盆地西南缘芦山地区古新统—下渐新统名山组—芦山组地层剖面为研究对象,利用磁组构方法,结合前人对研究区古地磁及构造变形的研究,恢复了该地区新生代早期的古应力方向.本研究获取了548块样品的磁组构数据,这些磁组构的磁面理与层面平行,产状校正后磁线理呈NE-SW方向(39°/219°),K3主轴方向相对集中(为120.9°±1.3°),为弱应变背景下平行层缩短之前初始变形磁组构类型,主要形成于地层成岩阶段,未受到后期褶皱等构造变形的强烈改造.本研究认为芦山剖面磁组构结果记录了研究区新生代早期的构造变形信息:新生代早期龙门山褶皱冲断带南段及川西南盆地受NW-SE向的最大主应力控制.该地区新生代晚期及现今应力场与新生代早期一致,可能继承了新生代早期的应力体制,暗示龙门山作为青藏高原的东边界可能在新生代早期已经形成.
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| 关 键 词： | 川西南前陆盆地 古地磁 龙门山褶皱冲断带 磁组构 古应力 |
Early Cenozoic paleo-stress field in the eastern margin of the Tibetan Plateau: Magnetic fabric records in the southwestern part of Sichuan Basin |
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| ZHANG Shuai,TIAN YunTao,TIAN Ye,LIU YiMin,TANG Yuan,QIN YongHui,YAN ZhaoKun,LI ShiHu,SHEN ZhongShan,ZHANG ZengJie.Early Cenozoic paleo-stress field in the eastern margin of the Tibetan Plateau: Magnetic fabric records in the southwestern part of Sichuan Basin[J].Chinese Journal of Geophysics,2021,64(5):1643-1653. |
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| Authors: | ZHANG Shuai TIAN YunTao TIAN Ye LIU YiMin TANG Yuan QIN YongHui YAN ZhaoKun LI ShiHu SHEN ZhongShan ZHANG ZengJie |
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| Institution: | (Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-Sen University,Guangzhou 510275,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai Guangdong 519082,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China) |
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| Abstract: | The southwestern part of the Sichuan Basin is located on the eastern margin of the Tibetan Plateau,adjacent to the southern segment of the Longmenshan fold-thrust belt.The early Cenozoic red beds in this area recorded the uplift history and tectonic evolution of the eastern margin of the Tibetan Plateau.In this study,we applied magnetic fabric(i.e.,anisotropy of magnetic susceptibility)analyses to the lower Paleogene stratigraphic section(including the Mingshan and Lushan formations)in Lushan area.A total of 548 samples were analyzed.Results show that magnetic foliations of the samples are parallel to the bedding,with magnetic lineations in a direction of NE-SW(39°/219°)and clustered K3(120.9°±1.3°).Such a fabric is the type of initial deformation magnetic fabric,which was formed in the diagenetic stage of the strata and has not been overprinted by later folding and faulting.We therefore suggest that these magnetic fabric results recorded the early Cenozoic paleo-stress field of the study area,where deformation was dominated by shortening with a NW-SE maximum principal stress,perpendicular to the magnetic lineation.The late Cenozoic and present stress field of this area,revealed by structural,GPS and earthquake focal mechanism studies,is similar to that of the early Cenozoic,suggesting that the Longmenshan plateau margin may have been formed in the early Cenozoic. |
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| Keywords: | Southwestern Sichuan foreland basin Paleomagnetism Longmen Shan fold-thrust belt Magnetic fabric Paleo-stress |
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