Zircon U-Pb Age,Geochemical Data:Constraints on the Origin and Tectonic Evolution of the Metamafic Rocks from Longmuco-Shuanghu-Lancang Suture Zone,Tibet  

作　　者：Yanwang Wu Cai Li Mengjing Xu Chaoming Xie Ming Wang 

机构地区：[1]School of Geology and Geomatics, Tianjin Chengjian University [2]College of Earth Science, Jilin University

出　　处：《Journal of Earth Science》2017年第3期422-432,共11页地球科学学刊（英文版）

基　　金：supported by the Postdoctoral Science Foundation of China (No. 2014M561023);the National Natural Science Foundation of China (Nos. 40872146, 41072166, 41503022);the Project of China Geological Survey (Nos. 1212011086061, 1212011221093, 1212011087009)

摘　　要：Bulk-rock major and trace elements and zircon U-Pb data are reported for Permian metamafic rocks from Guoganjianan, in the western part of Longmuco-Shuanghu-Lancang suture zone. These results offer new insights into mantle source characteristics and geodynamic setting of Permian ophiolitic fragments. U-Pb isotopic dating using SHRIMP II method reveals that the metamafic rocks were formed at 274.7± 3.9 and 279.8± 3.6 Ma. The metamafic rocks mostly show N-MORB-typed rare earth element patterns and are enrichment in large-ion lithophile elements, indicating that they are probably derived from partial melting of a depleted mantle in a back-arc basin. Our new data, together with recent studied results on Paleozoic ophiolitic fragments suggest the Paleo-Tethys Ocean in Central Qiangtang opened at Cambrian and widened between Ordovician and Devonian. Northward subduction started in the Late Devonian–Early Carboniferous and a back-arc basin developed during Permian.Bulk-rock major and trace elements and zircon U-Pb data are reported for Permian metamafic rocks from Guoganjianan, in the western part of Longmuco-Shuanghu-Lancang suture zone. These results offer new insights into mantle source characteristics and geodynamic setting of Permian ophiolitic fragments. U-Pb isotopic dating using SHRIMP II method reveals that the metamafic rocks were formed at 274.7± 3.9 and 279.8± 3.6 Ma. The metamafic rocks mostly show N-MORB-typed rare earth element patterns and are enrichment in large-ion lithophile elements, indicating that they are probably derived from partial melting of a depleted mantle in a back-arc basin. Our new data, together with recent studied results on Paleozoic ophiolitic fragments suggest the Paleo-Tethys Ocean in Central Qiangtang opened at Cambrian and widened between Ordovician and Devonian. Northward subduction started in the Late Devonian–Early Carboniferous and a back-arc basin developed during Permian.

关 键 词：Tibet Longmuco-Shuanghu-Lancang suture zone metamafic rock zircon SHRIMP U-Pb dating geochemistry 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]