青藏高原近南北向裂谷的时空分布特征及动力学机制  

Spatiotemporal distribution and geodynamic mechanism of the nearly NS-trending rifts in the Tibetan Plateau

作　　者：卞爽 于志泉 龚俊峰 杨蓉[1,2] 程晓敢 林秀斌[1,2] 陈汉林[1,2] BIAN Shuang;YU Zhiquan;GONG Junfeng;YANG Rong;CHENG Xiaogan;LIN Xiubin;CHEN Hanlin(Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province,School of Earth Sciences,Zhejiang University,Hangzhou 310027,Zhejiang,China;Research Center for Structures in Oil and Gas-bearing Basins,Ministry of Education,Hangzhou 310027,Zhejiang,China)

机构地区：[1]浙江大学地球科学学院,浙江省地学大数据与地球深部资源重点实验室,浙江杭州310027 [2]教育部含油气盆地构造研究中心,浙江杭州310027

出　　处：《地质力学学报》2021年第2期178-194,共17页Journal of Geomechanics

基　　金：国家自然科学基金项目(41472182);科技部第二次青藏高原综合科学考察研究项目(2019QZKK0708)。

摘　　要：青藏高原南部发育的一系列近南北向裂谷是印度-欧亚大陆持续挤压作用下的大型伸展构造,也是揭示高原后碰撞构造演化过程的重要对象。目前,关于南北向裂谷的形成机制存在多种假说模型,并对裂谷时空分布特征做出了不同的预测,这成为约束裂谷成因机制的关键条件。综合关于裂谷启动时间的已有研究成果,进一步梳理了南北向裂谷的时空分布特征,结果表明近南北向裂谷的启动时间似乎具有自西向东逐步减小的趋势,这与拉萨地体广泛出露的后碰撞岩浆作用演化过程一致。在此基础上,结合地球物理观测,推断近南北向裂谷的动力学机制与印度板片向东拆离假说最为契合。印度板片自西向东的拆离建立了向东传播的重力势能梯度,从而驱动岩石圈向东流动,最终导致南北向裂谷依次向东发育。A set of nearly NS-trending rifts developed in the Himalayan orogen and southern Tibet,which are the large-scale extensional structures formed under the continuous compression of the Indo-Eurasia continent,playing a significant role in revealing the post-collisional evolution of the Tibetan Plateau.Different predictions have been made on the spatiotemporal distribution of these rifts through the existing hypothesis models,constituting the key factors constraining the formation system of the rifts.In this study we synthesized previous studies on the initiation time of rifting,and further clarified the spatiotemporal trend.The analysis results showed that the rifting initiated progressively earlier westward,which is consistent with the evolution of post-collisional magmatism in the Lhasa Terrain.Moreover,combined with the geophysical observations,it is inferred that the geodynamic mechanism of the nearly NS-trending rifts accords closely with the hypothesis model concerning the eastward-propagating lateral detachment of the subducted Indian slab.The Indian slab detachment resulted in asynchronous gravitational potential energy gradients,which drove the lithosphere flow eastward and eventually caused the eastward development of the rifting.

关 键 词：青藏高原 近南北向裂谷 东西向伸展 时空分布特征 动力学机制 

分 类 号：P541[天文地球—构造地质学]