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丁烁,黄慧,牛耀龄,赵志丹,喻学惠,莫宣学. 2011. 东昆仑高Nb-Ta流纹岩的年代学、地球化学及成因. 岩石学报, 27(12): 3603-3614
东昆仑高Nb-Ta流纹岩的年代学、地球化学及成因
作者单位E-mail
丁烁 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China  
黄慧 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China
Department of Earth Sciences, Durham University, Durham DH1 3LE, UK 
 
牛耀龄 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China
Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
School of Earth Sciences, Lanzhou University, Lanzhou 730000, China 
niuyl@lzu.edu.cn, yaoling.niu@durham.ac.uk 
赵志丹 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China  
喻学惠 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China  
莫宣学 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China  
基金项目:本文受国家973项目(2011CB403102、2009CB421002)、国家自然科学基金项目(91014003、40830317、41130314)和中国地质调查局工作项目(1212011121260、1212011121066)联合资助.
摘要:
      东昆仑高Nb-Ta流纹岩位于东昆仑造山带东段,其锆石U-Pb年龄为213Ma,该时期东昆仑造山带正处于俯冲-碰撞造山阶段的晚期。与同时期东昆仑地区的其它酸性火山岩及世界其它处于俯冲-碰撞造山阶段的流纹岩相比较,这一套流纹岩显示高硅、高钾,低铝、低钙,高Nb、Ta及强烈亏损Sr、Eu的独特地球化学特征。东昆仑高Nb-Ta流纹岩的Sr、Nd同位素组成显示该流纹岩可能具有分别来源于地幔和上地壳的两个端元组分。通过讨论,本文认为这套高Nb-Ta流纹岩可能由以下机制形成:地幔碱性玄武岩浆(具有高Nb-Ta的特征)侵入花岗闪长质地壳,并在上地壳某处停留,大量斜长石发生分离结晶,导致岩浆Eu-Sr的极度亏损;同时,幔源岩浆的侵入引起上地壳围岩部分熔融,从而受到上地壳混染。新生壳源岩浆与幔源岩浆混合,并进一步结晶分异演化,最终导致东昆仑高Nb-Ta流纹岩的形成。
英文摘要:
      The East Kunlun high Nb-Ta rhyolite is located at the eastern end of the Kunlun orogenic belt. Zircon U-Pb analysis gives a magmatic age of about 213Ma, corresponding to the subduction/collision stage of the Kunlun Orogeny. Compared to the felsic volcanic rocks of similar ages in the region and rhyolites associated with subduction and collision zones worldwide, the rhyolite has high SiO2 and K2O, and low CaO and Al2O3. For trace elements, the rhyolite is enriched in Nb and Ta (with only a very weak negative Nb-Ta anomaly), but strongly depleted in Sr and Eu. Bulk rock samples are characterized by high initial Sr isotopic ratios and low initial Nd isotopic ratios with εNd(t)≈-3. Taken together, all these data are best interpreted as resulting from mixing of Nb-Ta rich mantle-derived melt with a crustal component. We propose that the East Kunlun high Nb-Ta rhyolites may be generated as follows: mantle-derived alkali basaltic melts (with inherited high Nb-Ta and εNd(t)>0) intruded the crust and developed a magma chamber, where the melt evolved through fractional crystallization with significant plagioclase separation (strongly depleted Sr and Eu) while assimilating the crustal material characterized by εNd(t)<0 and relatively low Nb and Ta before eruption.
关键词:流纹岩  高Nb-Ta  东昆仑
投稿时间:2011-05-01  修订日期:2011-06-28
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主办单位:中国矿物岩石地球化学学会
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