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| 西藏雅鲁藏布蛇绿岩形成构造环境的地球化学鉴别 | |
| 引用本文： | 李文霞,赵志丹,朱弟成,董国臣,周肃,莫宣学,DePAOLO Don,DILEK Yildirim.西藏雅鲁藏布蛇绿岩形成构造环境的地球化学鉴别[J].岩石学报,2012,28(5):1663-1673. |
| 作者姓名： | 李文霞 赵志丹 朱弟成 董国臣 周肃 莫宣学 DePAOLO Don DILEK Yildirim |
| 作者单位： | 1. 中国地质大学地质过程与矿产资源国家重点实验室,中国地质大学地球科学与资源学院,北京100083 2. 加利福尼亚大学地球与行星科学系,伯克利CA 94720 3. 迈阿密大学地质系,牛津OH 45056 |
| 基金项目： | 本文受国家重点基础研究发展规划项目(2009CB421002、2011CB403102)、国家自然科学基金项目(40830317、40873023、40973062、40973026)、中国地质调查局综合研究项目(1212011121260)、深部探测技术与实验研究专项课题(Sinoprobe-04-02)、美国自然科学基金(EAR1111959)和长江学者和创新团队发展计划资助(IRT1083)联合资助. |
| 摘 要： | 本文对西藏雅鲁藏布蛇绿岩带中部日喀则地区夏鲁蛇绿岩中的基性岩石进行了元素地球化学研究。岩石为低钾亚碱性玄武质岩石,具有低TiO2(0.64%～1.5%)、低K2O(<0.69%)、富Na2O(2.5%～6.0%)、烧失量普遍较高(2.0%～7.5%)的特征,表明样品普遍遭受蚀变。岩石具有与N-MORB类似的稀土元素和总体一致的微量元素特征,但是岩石明显富集大离子亲石元素和亏损高场强元素,显示了洋脊玄武岩向着岛弧岩浆作用的过渡趋势。日喀则蛇绿岩不是典型的洋中脊成因,应为SSZ型蛇绿岩,可能形成于与洋内俯冲有关的SSZ型的弧后或者弧前盆地中。对东西延伸超过1500km的雅鲁藏布蛇绿岩246套基性岩石形成的构造环境进行的地球化学判别,表明至少存在大陆岛弧型、地幔柱-洋内热点型、洋中脊-大洋岛弧型和典型大洋岛弧型等四种类型洋壳,揭示了特提斯洋存在多种构造环境的特征,有利于恢复和还原一个长期演化的、丰富的特提斯洋。 |
| 关 键 词： | 玄武岩 夏鲁蛇绿岩 地球化学判别 构造环境 雅鲁藏布蛇绿岩 |
| 收稿时间： | 2012/2/20 0:00:00 |
| 修稿时间： | 2012/4/26 0:00:00 |
Geochemical discrimination of tectonic environments of the Yalung Zangpo ophiolite in southern Tibet |
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| LI WenXi,ZHAO ZhiDan,ZHU DiCheng,DONG GuoChen,ZHOU Su,MO XuanXue,DePAOLO Don and DILEK Yildirim.Geochemical discrimination of tectonic environments of the Yalung Zangpo ophiolite in southern Tibet[J].Acta Petrologica Sinica,2012,28(5):1663-1673. | |
| Authors: | LI WenXi ZHAO ZhiDan ZHU DiCheng DONG GuoChen ZHOU Su MO XuanXue DePAOLO Don and DILEK Yildirim |
| Institution: | State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;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 and Planetary Science, University of California, Berkeley, CA 94720, USA;Department of Geology, Miami University, Oxford, OH 45056, USA |
| Abstract: | Elemental compositions for the basaltic rocks from Xialu ophiolite,Xigaze,central Yalung Zangpo ophiolite in southern Tibet were studied in this paper.The rocks are low-K tholeiitic basaltic rocks,with low TiO2(0.64% ～ 1.5%),K2O(< 0.69%),high Na2O(2.5% ～ 6.0%) and LOI(2.0% ～ 7.5%),implying a metasomatic processes after the rocks formed in the ocean.Their chondrite-normalized Rare Earth Elements(REEs) and primitive mantle-normalized multi-element patterns are very similar to the normal Mid-Ocean Ridge Basalt(N-MORB),with depletion in light REEs.But they show significant enrichment of Large Ion Lithophile Elements(LILEs;Rb,Ba,U,K) and depletion of High Field Stretch Elements(HFSEs;Nb,Ta,P,Ti,Zr,and Hf),suggesting arc-related components have been added to the source regions.The Xialu ophiolite is SSZ-type(Supra Subduction Zone) oceanic crust,instead of the typical N-MOR type ophiolite.It may have occurred in back-arc or fore-arc tectonic settings in an oceanic subduction-related system.A detailed geochemical discrimination of selected elements from 246 samples from literature and this work,allowed us to identify at least four different types of tectonic settings within the 1500km-long Yalung Zangpo ophiolite.The four-type basalts are(1) continental arc,(2) mantle plume or hot spot,(3) MORB and oceanic arc,and(4) typical oceanic arc.The presence of multiple tectonic settings seen from geochemical signatures of associated basalts within the Yalung Zangpo suture zone reconstructs a long-evolutional history of the Tethyan Ocean. |
| Keywords: | Basalt Xialu ophiolite Geochemical discrimination Tectonic settings Yalung Zangpo ophiolite |
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