摘要
印度与亚洲大陆碰撞形成了喜马拉雅造山带.该造山带是当今固体地球科学研究的重点和热点,是建立新的大陆动力学理论的最佳天然实验室.印度与亚洲大陆碰撞时限是正确认识和理解该造山带形成与演化、高原隆升的动力学过程等的起点.近南北向陆陆碰撞的最直接证据是碰撞带两侧块体在古纬度上的相互重叠.本文拟通过对相关古地磁资料的分析,结合近年来在拉萨地块南缘林子宗群火山岩和沉积岩夹层上获得的最新古地磁结果,探索当今占地磁数据所限定的印度和亚洲大陆发生初始碰撞的时间和古地理位置.结果表明,拉萨地块林子宗群形成时期(约64～44 Ma)古亚洲大陆最南缘的古地理位置(～10°N)限定了印度与亚洲大陆的初始碰撞最可能发生在65～50 Ma之间;如果以由印度洋海底地形所限定的东冈瓦纳大陆裂解前的印度板块形状为大印度模型,则印度与亚洲大陆的初始碰撞很可能发生在60～55 Ma之间.
The India-Asia collision was responsible for creating the Himalaya-Tibetan orogen which is a focus of today＇s solid Earth sciences and is considered to be the best natural laboratory for establishing new theory of continental dynamics. Timing of the India-Asia collision is not only the key boundary condition in all models for the evolution of the Himalaya-Tibetan orogenic system, but also the starting point of all discussions in the formation and evolution of the orogenic system, as well as the dynamics of plateau uplift. Collision between two north- southward moving continents is generally defined as a contact between continental lithospheres accompanied with the disappearance of oceanic lithosphere, and its most direct evidence is whether blocks distributed in both sides of the collision zone had compatible paleolatitudes. This paper aims to explore constraints to the initial timing and paleopositions of the India-Asia collision by analyzing presently available paleomagnetic data from the Lhasa Block and Himalayas. The newly obtained paleomagnetic results from the Linzizong Group （about 64-44 Ma） imply that the southern leading edge of the Asian continent was situated at paleolatitndes of -10°N in the Northern Hemisphere during the period of about 64-44 Ma and the initial contact between India and Asia was most likely occurred at 65-50 Ma. Given that Greater India comprised the present Indian continent and a -950 km northern extension, which was determined from its pre break-up position within East Oondwana and the bathymetry of the Indian Ocean west of Australia, we argue that the initial India-Asia collision most probably occurred between -55 and 60 Ma.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第9期2045-2058,共14页
Chinese Journal of Geophysics
基金
中国科学院知识创新工程重要方向项目(KZCX2-YW-Q09-01)
国家杰出青年基金项目(40525013)联合资助
