藏南错那拆离断层的活动时间限定及其构造意义  

Activity time constraints and tectonic significance of the Cuona Detachment,southern Tibet

作　　者：唐灼 董汉文[1] 王亚莹[1] 李广旭[1] 费镕泽 TANG Zhuo;DONG HanWen;WANG YaYing;LI GuangXu;FEI RongZe(Key Laboratory of Deep-Earth Dynamics,Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,自然资源部深地动力学重点实验室,北京100037

出　　处：《岩石学报》2023年第12期3572-3584,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42172261、92055202);国家重点研发计划(2021YFC2901901);第二次青藏高原科学考察项目(2019QZKK0702);中国地质调查局地质调查项目(DD20221630、DD20221817)联合资助.

摘　　要：藏南拆离系(South Tibet Detachment System,STDS)是沿喜马拉雅造山带走向发育的一套伸展拆离系统,其形成过程与喜马拉雅造山带的隆升历史和演化过程密切相关,是研究印度-欧亚大陆碰撞造山过程中构造变形作用的重要对象。错那拆离断层(Cuona Detachment,CD)为STDS在错那地区的出露部分,其为一数千米宽的韧性剪切带,带内发育大量不同类型的淡色花岗岩,本文在野外大比例尺填图的基础上,在CD内识别出两期淡色花岗岩:早期同构造淡色花岗岩和晚期构造后淡色花岗岩,并分别对两期淡色花岗岩进行锆石LA MC-ICP-MS U-Pb分析测试。锆石U-Pb定年结果表明,CD在20Ma仍在持续活动,直到14.8~16.5Ma左右停止活动。同时结合前人研究结果,进一步探讨错那地区STDS演化过程以及其沿造山带走向上的差异性规律。沿着喜马拉雅造山带走向,不同地区的STDS的活动时间呈现出明显的差异性,本文认为STDS停止时间主要表现出由西构造结向东(如错那地区)逐渐变年轻的趋势。The South Tibet Detachment System(STDS)is a set of stretched dissociation systems developed along the Himalayan orogenic belt,and its formation process is closely related to the uplift history and evolution process of the Himalayan orogenic belt,which is an important object for studying the tectonic deformation in the process of Indo-Eurasian collision and orogeny.Cuona Detachment(CD)is a ductile shear zone several kilometers wide in which a large number of different types of leucogranites develop,and on the basis of large-scale field mapping,two phases of leucogranites are identified in CD:early syn-tectonic leucogranites and late post-tectonic leucogranites.In this paper,zircon LA MC-ICP-MS U-Pb analysis tests were performed on three early leucogranites bodies and two late leucogranites bodies.Zircon U-Pb dating results showed that CD continued to be active at 20Ma until it stopped around 14.8~16.5Ma.At the same time,combined with the results of previous research,the evolution process of STDS in the Cuona region and its difference along the orogenic belt were further explored.Along the Himalayan orogenic belt,the activity time of STDS in different regions showed obvious differences,and this paper believes that the STDS cessation time mainly shows a trend of gradually becoming younger from the western tectonic junction to the east(such as the Cuona area).

关 键 词：喜马拉雅造山带 错那拆离断层 淡色花岗岩 变形 锆石U-PB年代学 

分 类 号：P541[天文地球—构造地质学] P588.121[天文地球—地质学] P597.3