囊谦盆地渐新世古地磁旋转变形研究及其对区域构造演化的启示  

Oligocene paleomagnetic rotation study of the Nangqian Basin and its implications on regional tectonic evolution

作　　者：徐万龙 颜茂都[1,2] 牛智超 于亮 徐尊铂 申苗苗 关冲 付强 张大文 栗兵帅 XU Wanlong;YAN Maodu;NIU Zhichao;YU Liang;XU Zunbo;SHEN Miaomiao;GUAN Chong;FU Qiang;ZHANG Dawen;LI Bingshuai(Key Laboratory of Tibetan Plateau Earth System,Environment and Resources(TPESER),Institute of Tibetan Plateau Research,Beijing 100101;University of Chinese Academy of Sciences,Beijing 100049;School of Ecology,Resources and Environment,Dezhou University,Dezhou 253023,Shandong;Xi'an Center of Geological Survey,China Geological Survey,Xi'an 710054,Shaanxi;Department of Earth Sciences,Utrecht University,Utrecht 3584CS,Netherlands;College of Tourism and Resources Environment,Zaozhuang University,Zaozhuang 277160,Shandong;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi)

机构地区：[1]中国科学院青藏高原研究所,青藏高原地球系统与资源环境重点实验室,北京100101 [2]中国科学院大学,北京100049 [3]德州学院,生态与资源环境学院,山东德州253023 [4]中国地质调查局,西安地质调查中心,陕西西安710054 [5]乌德勒支大学,地球科学学院,荷兰乌德勒支3584CS [6]枣庄学院,旅游与资源环境学院,山东枣庄277160 [7]东华理工大学,地球科学学院,江西南昌330013

出　　处：《第四纪研究》2024年第6期1649-1661,共13页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:42430807、41974080、42204087和42404084);国家重点研发计划项目(批准号:2022YFF0800502);科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0707)共同资助。

摘　　要：青藏高原东南缘新生代期间响应印度与欧亚板块碰撞发生了顺时针旋转及东南向逃逸,这个过程在调节高原内部隆升变形等方面起到重要作用。但目前关于青藏高原东南缘旋转变形,东南向逃逸变形等构造变形过程之间的相互关系的认识仍不清楚。本研究选择青藏高原东南缘北部囊谦盆地渐新世地层开展了详细的古地磁旋转变形研究,共获得25个采点225个古地磁样品。系统的热退磁分析共分离出188个特征剩磁方向,得到21个有效采点,矫正前的平均方向为D_(g)=168.1°±10.8°, I_(g)=-21.1°±19.1°, α_(95)=11.8°, k=8.3,校正后为Ds=171.0°±7.4°, I_(s)=-33.3°±10.8°, α_(95)=6.8°, k=22.7。详细的岩石磁学和野外检验表明上述特征剩磁方向是原生特征剩磁。通过与相应欧亚参考极对比,上述磁偏角显示囊谦盆地渐新世地层记录了17.2°±8.1°的逆时针旋转变形。结合弯山构造分析和其他地质证据,本研究认为囊谦盆地与南部的贡觉、芒康和兰坪盆地在晚始新世后响应印度-欧亚板块碰撞而发生了弯山构造变形,顺时针旋转幅度自北至南逐渐增加,囊谦盆地新近纪以来还叠加了局部逆时针旋转变形。The southeastern Tibetan Plateau has undergone clockwise rotation and southeastward extrusion in response to the India-Eurasia collision during the Cenozoic.This process has played a crucial role in accommodating the uplift and deformation of the plateau.However,the relationship between these tectonic deformation processes,such as rotation and southeastward extrusion,remains unclear.To gain better insight into the Cenozoic tectonic deformation of the southeastern Tibetan Plateau,we conducted a new paleomagnetic study in the Nangqian Basin,located in the northern part of this region.We set up two sampling sections,Baerqu(BEQ:32.2°N,96.0°E)and Tuotuohe(TTH:32.0°N,59.9°E),in the western part of the Nangqian Basin,from which we collected a total of 225 paleomagnetic samples from 25 sampling sites.Rock magnetic analysis indicates that the main magnetic carriers are pseudo-single domain(PSD)magnetite and single domain(SD)hematite.Through detailed thermal demagnetization analysis,we successfully isolated 188 characteristic remanent magnetic directions from 21 sites.Their mean direction is D_(g)=168.1°±10.8°,I_(g)=-21.1°±19.1°,α_(95)=11.8°,k=8.3 in geographic coordinate,and Ds=171.0°±7.4°,I_(s)=-33.3°±10.8°,α_(95)=6.8°,k=22.7 in stratigraphic coordinate.Detailed rock magnetic and field test analyses indicated that this mean direction is likely primary magnetization.The studied strata are speculated to be Oligocene based on comparisons of lithology and spores with strata from adjacent areas.Compared with the Eurasian apparent polar wander path reference pole,this paleomagnetic declination yields a 17.2°±8.1°counterclockwise rotation of the Nangqian Basin since the Oligocene.Combined with oroclinal analysis and other geological evidence,this study proposes that the Nangqian,Gonjo,Mangkang and Lanping basins have exhibited an increasing degree of clockwise rotation from north to south in an oroclinal bending manner since the Late Eocene.Additionally,the Nangqian Basin has experienced a superimposed co

关 键 词：青藏高原东南缘 囊谦 古地磁 弯山构造演化 

分 类 号：P534.614[天文地球—古生物学与地层学] P318.21[天文地球—地质学]