西藏长青温池-波弄贡变质带片麻岩锆石ELA-ICP-MS U-Pb年龄及地质意义  

ELA-ICP-MS zircon U-Pb dating for gneisses from Changqing Wenchi-Bolongong metamorphic zone,Xizang(Tibet) and its geological significances

作　　者：梁华英[1] 喻亨祥[2] 莫测辉[3] 曾提[1] 谢应雯[1] Charlotte M. Allen 莫济海[1] 

机构地区：[1]中国科学院广州地球化学研究所成矿动力学重点实验室,广东广州510640 [2]桂林工学院资源与环境工程系,广西桂林541004 [3]暨南大学环境工程系,广东广州510632 [4]澳大利亚国立大学地球科学研究所

出　　处：《地球化学》2006年第5期472-478,共7页Geochimica

基　　金：国家自然科学基金(40472049);国家重点基础研究发展计划项目(G19999043203);中国科学院广州地球化学研究所知识创新工程领域前沿项目(GIGCX-04-03)

摘　　要：西藏林芝至通麦一带出露大面积变质岩,变质岩中含长柱状锆石。长柱状锆石晶体形态特征、矿物包裹体、CL图像及Th/U比值在0.1～0.4之间,表明锆石主要来自火山岩,受后期变质流体改造。长柱状锆石ELA-ICP-MSU-Th-Pb年龄为(40.7±0.3)Ma,MSWD=2.35。变质流体改造边缘部分年龄和核部年龄基本一致。长柱状锆石特征及年龄表明长青温池至通麦一带片麻岩原岩为新生代含火山物质的沉积岩而不是元古宙变质基底。The metamorphic gneisses in the Lizhi-Tongmai region, Xizang （Tibet） host aciculate zircon grains. The morphologic features such as euhedral crystal form of zircon grains, inclusion minerals such as mica, potassic feldspar, albite, quartz and glass in zircon grains, together with cathodoluminescence （CL） photos showing the oscillatory zoning and high Th/U ratios indicate that the aciculate zircon grains are not formed by metamorphic processes but derived from volcanic rocks. The zircon grains are affected by metamorphic fluids. ELA-ICP-MS U-Pb ages of the aciculate zircon grains from the gneisses are （40.7±0.3） Ma with MSWD = 2. 35. The rim, which were affected by the metamorphic fluids, and the core of the zircon grains have almost the same ages. The features of the zircon grains together with their U-Pb age suggest that the protolith of the metamorphic rocks are Cenozoic volcanic sedimentary rocks, rather than the Proterozoic base.

关 键 词：U-PB年龄 ELA-ICP-MS 锆石 变质岩 西藏 

分 类 号：P597[天文地球—地球化学]