科希斯坦-拉达克弧及其周缘地块的古地磁学研究进展  

Paleomagnetic constraints on paleogeography for the Kohistan-Ladakh arc and its surrounding terranes

作　　者：袁杰 邓成龙[1,2] 杨振宇 Jie Yuan;Chenglong Deng;Zhenyu Yang(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;College of Resources,Environment and Tourism,Capital Normal University,Beijing 100048,China)

机构地区：[1]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 [2]中国科学院大学地球与行星科学学院,北京100049 [3]首都师范大学资源环境与旅游学院,北京100048

出　　处：《科学通报》2024年第11期1461-1474,共14页Chinese Science Bulletin

基　　金：国家自然科学基金(41888101,42104067,91855216);中国博士后科学基金(2021M693152,2023T160638)资助。

摘　　要：对于科希斯坦-拉达克弧在印度-亚洲碰撞前的构造属性,学界存在两种不同的认识:陆缘弧和洋内弧.厘定其构造属性,将直接关联新特提斯洋古地理重建方案,对进一步解析印度-亚洲碰撞时间、位置和方式,以及恢复亚洲大陆构造变形历史等具有重要科学意义.本文在总结白垩纪至古新世科希斯坦-拉达克弧及其周缘地块古地磁数据的基础上,主要从古地磁学的视角,重建科希斯坦-拉达克弧及周缘地块的时空构造格局,厘定科希斯坦-拉达克弧的构造属性.在晚白垩世,喀喇昆仑地块与拉萨地块西缘的古纬度一致,两者基本稳定位于亚洲大陆南缘;科希斯坦-拉达克弧在90 Ma位于南半球赤道附近,而在64 Ma已经向北漂移到北半球低纬度地区;特提斯喜马拉雅在75 Ma左右作为印度被动大陆边缘,其中部和东部分别位于16.7°和19.4°S.在64 Ma科希斯坦-拉达克弧与拉萨地块西缘之间仍然被南北向宽度约为900 km的洋盆所分隔,意味着科希斯坦-拉达克弧为洋内弧.在重建印度-亚洲碰撞系统时,综合考虑特提斯喜马拉雅及科希斯坦-拉达克弧的古地磁数据,构建了印度-亚洲三阶段碰撞模型.该模型不仅协调了一系列地质证据,还为新特提斯洋古地理重建及亚洲陆内变形提供重要约束.例如,什约克缝合带与雅鲁藏布江缝合带曾经相连并可对比,据此推断,喀喇昆仑断裂至少具有400 km的位移量.Understanding the nature of the Kohistan-Ladakh arc before the India-Asia collision is crucial for reconstructing the Tethyan paleogeography,deciphering geodynamic process of the India-Asia collision,and restoring Asia’s history of intracontinental deformation.However,there are two opposing views dealing with nature of the Kohistan-Ladakh arc:The continental marginal arc and intra-oceanic island arc.Based on the accumulated published paleomagnetic data for the Kohistan-Ladakh arc and its surrounding terranes during the Cretaceous-Paleocene,we reconstruct paleogeography of the Kohistan-Ladakh arc and its surrounding terranes,and explore the nature of the Kohistan-Ladakh arc.The Karakoram terrane was situated on the southern edge of Asia at a paleolatitude consistent with that of the western Lhasa terrane in the late Cretaceous.The Kohistan-Ladakh arc was situated in the equatorial Neo-Tethys Ocean(southern hemisphere)in the early Late Cretaceous(ca.90 Ma)before drifting northward to reach the low-latitude northern hemisphere in the early Paleocene(ca.64 Ma).The central and eastern parts of the Tethyan Himalaya,as the northern margin of India prior to the collision,were located at paleolatitudes of 16.7°and 19.4°S at ca.75 Ma,respectively.The Kohistan-Ladakh arc was separated from the western Lhasa terrane by an ocean basin with a north-south extent of~900 km at ca.64 Ma.The above analyses suggest that the Kohistan-Ladakh arc demonstrated intra-oceanic characteristics prior to the India-Asia collision.Therefore,the Kohistan-Ladakh arc should be considered in the India-Asian collision system.Recently published paleomagnetic data obtained from the Tethyan Himalaya terrane,data obtained from the Kohistan-Ladakh arc,and the apparent polar wander path of India inspired us to propose a triple-stage India-Asia collision model.The first collision occurred at ca.64 Ma between the Tibetan Himalaya terrane and the Kohistan-Ladakh arc.The second collision occurred at ca.61 Ma between the Tibetan Himalaya terrane(including

关 键 词：科希斯坦-拉达克弧 拉萨地块 喀喇昆仑地块 特提斯喜马拉雅 印度-亚洲碰撞系统 喀喇昆仑断裂 

分 类 号：P318.44[天文地球—固体地球物理学]