西藏南冈底斯带拢布村花岗岩LA-ICP-MS锆石U-Pb年龄及其成因  

LA-ICP-MS zircon U-Pb age and genesis of Longbucun granite in Southern Gangdise Belt,Tibet

作　　者：钟云[1] 夏斌[1,2] 刘维亮[1] 夏连泽[3] 夏中宇[1] 王利红[1] 

机构地区：[1]中山大学海洋学院海洋石油勘探开发广东省普通高校重点实验室,广东广州510275 [2]中国科学院广州地球化学研究所,广东广州510640 [3]中山大学地球科学系,广东广州510275

出　　处：《地质通报》2013年第9期1362-1370,共9页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011120978;1212011121259和1212011221105);国家973计划项目课题(编号:2012CB214705)

摘　　要：在一定条件下,花岗岩对于研究古大洋板块俯冲消减及陆-陆碰撞等板块演化过程具有重要的意义。拢布村花岗岩体位于西藏南冈底斯带中段,有关南冈底斯带花岗岩类形成年代仍存在不同认识。通过LA-ICP-MS锆石U-Pb测年获得拢布村花岗岩的形成年龄为157.0Ma±2.9Ma,表明南冈底斯带存在晚侏罗世岩浆活动。拢布村花岗岩富集Rb、Ba、Th、U、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,显示出岛弧岩浆岩的特征,指示晚侏罗世南冈底斯带存在新特提斯洋北向欧亚大陆的早期俯冲运动。研究表明,拢布村花岗岩为洋壳板块俯冲消减作用背景之下上覆地幔楔部分熔融的产物。Granite has important significance for the study of ocean plate subduction and continent-continent collision under certain conditions. Longbucun granite belongs to the middle part of Southern Gangdise Belt, and the formation age of the granitoids in this belt is a subject of much controversy. The LA-ICP-MS U-Pb zircon age of Longbucun granite is 157.0Ma±2.9Ma, which shows that there existed granitic magmation in the Late Jurassic in Southern Gangdise Belt. Longbucun granite is enriched in such large-ion lithophile elements as kb, Ba, Th, U and K and depleted in the high field strength elements like Nb, Ta and Ti, suggesting the fea- tures of island arc magmatic rocks and indicating that there existed an early-stage northward subduction of the Neo-Tethys Ocean to the Eurasian Plate in the Late Jurassic period. Longbucun granite was formed by partial melting of the mantle wedge under the sub- duction of the Neo-Tethys plate.

关 键 词：拢布村花岗岩 锆石U-PB LA-ICP-MS 新特提斯洋 南冈底斯带 

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