西藏措勤晚白垩世英安岩的厘定与地球化学特征  

Geochemical characteristics of the Late-Cretaceous dacite in Coqen,western Gangdese batholith,Tibet

作　　者：王伟[1,2] 曾令森 刘静[4] 肖萍[4] 高利娥[3] 

机构地区：[1]中国科学院青藏高原研究所大陆碰撞与高原隆升重点实验室,北京100101 [2]中国科学院大学,北京100049 [3]中国地质科学院地质研究所大陆构造与动力学国家重点实验室,北京100037 [4]中国地震局地质研究所,北京100029

出　　处：《地质科学》2013年第2期484-500,共17页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划"973"项目(编号:2011CB403102);国家自然科学基金项目(编号:41073024;41273034)资助

摘　　要：野外地质调查和SHRIMP锆石U／Pb地质年代学研究表明，拉萨地块中带措勤地区发育一套形成于晚白垩世中期的英安岩（88．5±1．2Ma）。该套火山岩具有岛弧火山岩的地球化学特征，为地壳深部岩浆岩部分熔融形成的I型岩浆岩，经历了明显的斜长石分离结晶作用。与同时代的侵入岩相比，该套火山岩为高度演化的岩浆，Rb／Sr比值较高，但Sr／Y比值较低。在拉萨地块内部，广泛发育的90～85Ma的岩浆作用与新特提斯洋的北向俯冲作用相关。Field investigations and zircon SHRIMP U-Pb dating show that a suite of dacite formed at Late Cretaceous （ 88.5± 1.2 Ma） occurred in the southeast of Coqen, western Gangdese Batholith,Tibet. This suite of volcanic rocks is characterized by trace element geochemistry similar to those formed in the arc environment. Geochmical and isotopic data indicate that they are I-type igneous rocks and have experienced high degrees of plagioclase fractional crystallization. As compared to those intrusive rocks of similar ages, this suite of rocks represents highly evolved magmas drieved from partial melting of deep crustal mafic rocks and is characterized by elevated Rb/Sr but lower Sr/Y ratios. Our new data as well as those from the literature further indicate that the Lhasa terrane had experinecd extensive magmatism at 90-85 Ma due to northward subduction the Lhasa terrane Neo-Tethyan oceanic lithosphere beneath the

关 键 词：岛弧岩浆作用 火山岩拉萨地块 锆石U Pb定年 Hf同位素地球化学 

分 类 号：P588[天文地球—岩石学]