藏南亚东地区花岗质片麻岩LA-ICP-MS锆石U-Pb定年及其地球化学特征  

LA-ICP-MS Zircon U-Pb Dating of Granitic Gneiss from Yadong Area in South Tibet and Its Geochemical Characteristics

作　　者：吕鹏瑞[1,2] 张海迪 罗彦军[1] 姚文光[1] Lu Pengrui;Zhang Haidi;Luo Yanjun;Yao Wenguang(Xi'an Center of Geological Survey,China Geological Survey,Xi'an 710054,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits ,Ministry of Natural Resources ,Xi'an 710054,China)

机构地区：[1]中国地质调查局西安地质调查中心,陕西西安710054 [2]自然资源部岩浆作用成矿与找矿重点实验室,陕西西安710054

出　　处：《地球科学》2018年第12期4459-4474,共16页Earth Science

基　　金：中国地质调查局地质调查项目(No.DD20160105)

摘　　要：亚东地区出露高喜马拉雅结晶岩系,是研究喜马拉雅造山带地质演化的理想地区.为探讨该区花岗质片麻岩的成因类型、岩浆源区、形成时代以及大地构造意义,对其进行了LA-ICP-MS锆石定年和地球化学特征研究.结果显示,该区的花岗质片麻岩具有高SiO2、Al2O3、Na2O、K2O含量和低Fe2O3、MgO、MnO含量,轻、重稀土明显分馏,相对富集LREE和LILE元素(Rb、Th、U、K),亏损HFSE元素(Ba、Nb、Ta、Sr、P、Ti),锆石表面年龄介于498.5±14.7Ma^480.0±11.7Ma.总体显示未分异的钙碱性强铝质S型花岗岩类的特征,可能是后碰撞造山阶段陆源杂砂岩经历高温深熔作用的产物.The high Himalaya crystalline rock series occurred in Yadong area, which is an ideal area for studying the tectonic evolution of the Himalayan orogenic belt. In order to discuss the genetic type, magmatic source,formation age and tectonic significance of granitic gneiss in the Yadong area, the LA-ICP-MS zircon dating and geochemical characteristics of these granitic gneisses were studied. The results show that the granite gneisses have high SiO2,Al2O3, Na2O and K2O contents, while they are low in Fe2O3, MgO and MnO contents. The granitic gneisses have experienced obvious REE fractionation, which are relatively enriched in LREE and LILE (Rb, Th, U and K elements) but are depleted in HFSE (Ba, Nb, Ta, Sr, P and Ti elements), and their zircon 206Pb/238U ages vary from 498.5±14.7 Ma to 480.0±11.7 Ma. Thus, the granitic gneisses generally show the geochemical characteristics of undifferentiated S-type granites with calcium-alkaline and strong peraluminous properties, which might be formed by the high-temperature anatexis of terrigenous greywacke during the post-collision orogeny stage.

关 键 词：花岗质片麻岩 锆石定年 亚东 藏南 地球化学 

分 类 号：P581[天文地球—岩石学]