卓奥友峰藏南拆离系的活动历史:来自淡色花岗岩年代学的制约  

The slip history of the South Tibetan Detachment System in the Cho Oyu region:Constraints from leucogranite geochronology

作　　者：杨雷 高成 刘小驰[3] 王佳敏[3] 周梁杰 刘志超 吴福元[3] YANG Lei;GAO Cheng;LIU XiaoChi;WANG JiaMin;ZHOU LiangJie;LIU ZhiChao;WU FuYuan(College of Earth Science,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330302,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;School of Earth Sciences and Engineering,SunYat-sen University,Guangzhou 510275,China)

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]东华理工大学核资源与环境国家重点实验室,南昌330302 [3]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 [4]中山大学地球科学与工程学院,广州510275

出　　处：《岩石学报》2022年第9期2709-2722,I0001-I0004,共18页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察研究(2019QZKK0802);国家自然科学基金项目(41888101)联合资助.

摘　　要：作为喜马拉雅造山过程中的重要产物,藏南拆离系的发展和喜马拉雅山脉的隆升紧密相关。因此,对藏南拆离系的研究可以帮助我们理解喜马拉雅造山带的演化过程和历史。虽然学术界对于藏南拆离系进行了大量的研究,但关于其形成机制仍然存在争议。本次研究选择藏南中部卓奥友峰地区进行研究,对侵入藏南拆离系下部的淡色花岗岩进行独居石和锆石U-(Th)-Pb定年。结果表明,该区域淡色花岗岩的活动时代为18~17Ma。前人分析得到这些淡色花岗岩的锆石和磷灰石裂变径迹年龄分别为~15Ma和~13Ma。结合前人热年代学工作,本文研究表明卓奥友峰淡色花岗岩在很短的时间间隔内(~4Myr)从~700℃冷却到~120℃,平均冷却速度超过100℃/Myr。在13Ma以后,淡色花岗岩经历了较为缓慢的冷却过程(~10℃/Myr)。这些研究结果可能指示了卓奥友峰地区藏南拆离系在17Ma或之前已经开始,一直持续到13Ma左右。结合高喜马拉雅变质作用和淡色花岗岩研究,本文认为藏南拆离系的启动和发展可能主要受到高喜马拉雅结晶岩系在峰期变质作用的影响。As the product of Himalayan orogeny,the development of the South Tibetan Detachment System(STDS)is closely related to the rise of Himalaya.Therefore,we can understand the evolution process of Himalayan orogeny through the study of STDS.Although many studies have been carried out on the STDS,there is still controversy about its formation mechanism.In this study,we processed U-(Th)-Pb geochronology of zircon and monazite in leucogranite which intruded below the STDS of Cho Oyu Himalaya.The results show that the leucogranites crystallized at 18~17Ma.A previous study reported the fission track ages of zircon and apatite in these leucogranites of~15Ma and~13Ma,respectively.Combining with the thermochronology and our research,it suggests that the Cho Oyu leucogranite has been cooled from~700℃to~120℃in a tight time interval(about 4Myr)with a cooling rate beyond 100℃/Myr.After~13Ma,the leucogranite has experienced a relatively slow cooling history(~10℃/Myr).It indicated that the development of the STDS in the Cho Oyu region initiated before 17Ma and ended at about 13Ma.Combining with the study of metamorphism and leucogranite in the Great Himalayan Crystalline(GHC),we suggest that the initiation and development of the STDS may be related to the peak metamorphism of the GHC.

关 键 词：藏南拆离系 卓奥友峰 淡色花岗岩 喜马拉雅 年代学 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]