藏南冲巴雍错淡色花岗岩体热年代学及其对藏南拆离系和亚东裂谷构造活动时限的制约  

Thermochronology of the Chumba Yumco leucogranite,southern Tibet:Constraints on the onset time of the STDS and the Yadong rift

作　　者：李开玉 CHEVALIER Marie-Luce 李海兵[1,2] 潘家伟 王世广[1,3] 白明坤 刘富财 王平[1] LI KaiYu;CHEVALIER Marie-Luce;LI HaiBing;PAN JiaWei;WANG ShiGuang;BAI MingKun;LIU FuCai;WANG Ping(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;School of Earth Science and Mineral Resources,China University of Geosciences,Beijing 100083,China;School of Earth and Space Sciences,Peking University,Beijing 100871,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 [2]南方海洋科学与工程广东省实验室(广州),广州511458 [3]中国地质大学地球科学与资源学院,北京100083 [4]北京大学地球与空间科学学院,北京100871

出　　处：《岩石学报》2020年第10期3097-3116,共20页Acta Petrologica Sinica

基　　金：科技部国家重点研发计划项目(2016YFC0600310);国家自然科学基金项目(41672211);中国地质科学院基本科研业务费项目(JYYWF201810);中国地质调查局项目(DD20190057、DD20190059)联合资助。

摘　　要：藏南拆离系和亚东裂谷是藏南地区重要的伸展构造,与青藏高原的隆升和生长密切相关,其新生代以来的构造热-年代学研究,对探讨高原的生长过程和大陆变形动力学具有重要意义。本文对西藏南部亚东地区的冲巴雍错花岗岩进行了U-Pb定年和低温热年代学分析,结果表明,岩体自22Ma侵位后经历了5个不同的冷却阶段:18~15.6Ma期间岩体的冷却速率为125℃/Myr;15.6~11Ma期间,平均冷却速率约94℃/Myr;11~7Ma期间,平均冷却速率约24℃/Myr;7~3Ma平均冷却速率约5℃/Myr;3Ma以后平均冷却速率约为14℃/Myr。因岩体位于藏南拆离系内,又被亚东断层切过,认为藏南拆离系的活动时限为22~11Ma,亚东正断层的起始活动时间为11Ma,且热历史模拟结果显示岩体在~3Ma发生了快速冷却,可能指示了亚东裂谷的一次强烈活动。The South Tibetan Detachment System(STDS)and the Yadong-Gulu Rift(YGR)are important extensional structures in the southern Tibet,which are closely related to the uplift of the Tibetan Plateau.The chronological information of the tectonic uplift in southern Tibet since the Cenozoic is of great significance for the discussion of the uplift mechanism of the Tibetan Plateau and the dynamics of continental deformation.We conducted zircon U-Pb dating and low-temperature thermochronology analysis of apatite fission tracks on the Chumba Yumco leucogranite in the Yadong area of the southern Tibet.The results show that the Chumba Yumco leucogranite have gone through five different uplift-cooling stages within 22 Ma:the cooling rate during 18~15.6 Ma is 125℃/Myr;during 15.6~11 Ma,the average cooling rate was about 94℃/Myr;11~7 Ma,the average cooling rate is about 24℃/Myr;the average cooling rate of 7~3 Ma is about 5℃/Myr;after 3 Ma,the average cooling rate was about 14℃/Myr.Because the studied pluton is located in the STDS and has been cut by the Yadong fault,we conclude that the activity time of the STDS is 22~11 Ma and the onset time of the Yadong rift is 11 Ma.Thermal history modeling results indicate a fast cooling stage at^3 Ma,which represent strong activity of the Yadong rift.

关 键 词：藏南拆离系 亚东裂谷 淡色花岗岩 U-PB定年 低温热年代学 

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