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

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±14.7 Ma~480.0±11.7 Ma.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. 

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

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.