SHRIMP dating of the Bangong Lake SSZ-type ophiolite: Constraints on the closure time of ocean in the Bangong Lake-Nujiang River,northwestern Tibet  

作　　者：SHI RenDeng1,2 1 School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China 2 Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China (email: [e-mail]) 

出　　处：《Chinese Science Bulletin》2007年第7期936-941,共6页

基　　金：Supported by the Ministry of Land and Resources (Grant No. 20010101);the National Natural Science Foundation of China (Grant No. 40572036 and 40610104005)

摘　　要：The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic mélange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The SHRIMP U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke (Sample 01Y-155) range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma (n = 12, MSWD = 1.2), suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area.The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic mélange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The SHRIMP U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke （Sample 01Y-155） range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma （n = 12, MSWD = 1.2）, suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area.

关 键 词：西藏 班公湖怒江缝合带 古海洋闭合时期 SSZ型蛇绿岩 SHRIMP 测年 

分 类 号：P588.1[天文地球—岩石学]