拉萨地体与特提斯喜马拉雅白垩纪古地磁学和年代学研究

发布时间：2018-01-10 05:33

本文关键词：拉萨地体与特提斯喜马拉雅白垩纪古地磁学和年代学研究　出处：《中国地质大学(北京)》2016年博士论文　论文类型：学位论文

【摘要】：印度?亚洲的碰撞过程及其造成的陆内变形一直是国内外地学工作者研究的前沿和热点课题,雅鲁藏布江缝合带两侧的特提斯喜马拉雅和拉萨地体自白垩纪以来分别是印度板块与亚洲大陆的最前缘,其白垩纪以来的古地理演化对理解上述课题至关重要。本论文通过对雅鲁藏布江缝合带两侧地体开展白垩纪古地磁学及U-Pb锆石年代学等的综合研究,并结合已有的地质及地球物理数据,获得如下几点新成果及认识:(1)拉萨地体西部措勤地区和狮泉河地区所采火山岩的U-Pb锆石年龄分别为早白垩世(?117 121 Ma)和晚白垩世(?67.7 Ma),而特提斯喜马拉雅浪卡子县工布学乡地区桑秀组火山岩的U-Pb锆石年龄为?124 135 Ma;(2)在拉萨地体西部地区获得3个白垩纪古地磁极,表明亚洲大陆南缘(29.8°N,84.0°E)在白垩纪期间一直位于北纬?16.8°,且近于目前的东西向排列;(3)在特提斯喜马拉雅山南地区新获得2个早白垩世火山岩古地磁极证实了山南地区(28.5°N,92.0°E)在?130 Ma位于南纬50.5°左右,支持特提斯喜马拉雅是印度次大陆的延伸部分;(4)确定早白垩世(?135-125 Ma)期间,宽约几千公里的新特提斯大洋位于拉萨地体和特提斯喜马拉雅之间;(5)推断印度克拉通北缘与特提斯喜马拉雅南缘之间在晚白垩世很可能存在一个小的洋盆伸展;(6)推断印度-亚洲碰撞过程很可能是复杂的“双陆-陆碰撞模式”,并提出特提斯喜马拉雅北缘首先沿现今的雅鲁藏布江缝合带在?54.8 Ma与亚洲大陆(拉萨地体)南缘发生碰撞,而印度克拉通北缘在?41.7 Ma与特提斯喜马拉雅南缘发生碰撞;(7)约束印度-亚洲的碰撞及随后的持续挤压导致拉萨地体和河西走廊之间发生了近800 1000 km的南北向地壳缩短。
[Abstract]:India? The collision process in Asia and the intracontinental deformation caused by it have always been the frontier and hot topic of geoscientists at home and abroad. The Tethys Himalayan and Lhasa terrains on both sides of the Brahmaputra suture belt have been the leading edge between the Indian plate and the Asian continent since the Cretaceous. The paleogeographic evolution since Cretaceous is very important to understand the above problems. In this paper, the paleomagnetism and U-Pb zircon geochronology of the Cretaceous are studied comprehensively on the two sides of the Yalu Zangbo River suture belt. Combined with existing geological and geophysical data. The U-Pb zircon ages of volcanic rocks in the western Lhasa terrane and Shiquanhe area are early Cretaceous? 117 ~ 121 Ma) and late Cretaceous? 67.7 Mahe, and U-Pb zircon age of the Sangxiu formation volcanic rocks in Gongbuxue Xiang area, Langkazi County, Himalayas, Tethys? 124 + 135 Ma; (2) three Cretaceous paleomagnetic poles were obtained in the western Lhasa terrane, indicating that the southern margin of the Asian continent is 29.8 掳Nu 84.0 掳E) and has been located in the northern latitude during the Cretaceous. 16.8 掳, and close to the current east-west alignment; 3) two new early Cretaceous volcanic rock paleomagnetic poles obtained in the southern part of the Tethys Himalayas confirm the presence of 28.5 掳Nu 92.0 掳E in Shannan area. 130Ma is located at about 50.5 掳south latitude, supporting the Tethys Himalaya as an extension of the Indian subcontinent. During 135-125 Ma, the Neo-Tethys Ocean, some several thousand kilometres wide, was located between the Lhasa terrane and the Tethys Himalayas; It is inferred that between the northern margin of the Indian craton and the southern margin of the Tethys Himalayas there may be a small ocean basin extension in the late Cretaceous. We infer that the India-Asia collision process is probably a complex "double continent collision model", and suggest that the northern margin of the Tethys Himalayas was first located along the present-day Brahmaputra suture zone? 54.8 Ma collided with the southern margin of the Asian continent (Lhasa terrace), while the northern margin of the Indian craton lies in? 41.7 Ma collided with the southern edge of the Tethys Himalayas; The collision between Lhasa and Hexi Corridor resulted in the shortening of the crust from the south to the north of the Lhasa area and between the Hexi Corridor and the collision between India and Asia.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P597.3;P318.44

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