| 三江地区澜沧江带南段半坡杂岩体锆石U-Pb年龄、岩石地球化学特征及板块构造环境 |
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| 引用本文： | 李钢柱,苏尚国,段向东.三江地区澜沧江带南段半坡杂岩体锆石U-Pb年龄、岩石地球化学特征及板块构造环境[J].地学前缘,2012,19(4):96-109. |
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| 作者姓名： | 李钢柱 苏尚国 段向东 |
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| 作者单位： | 1. 地质过程与矿产资源国家重点实验室； 中国地质大学 （北京） 地球科学与资源学院， 北京 100083
2. 武警黄金第二支队， 内蒙古 呼和浩特 010010
3. 云南省地质调查局， 云南 昆明 650051 |
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| 基金项目： | 国家重点基础研究发展计划“973”项目，中国地质大学(北京)特聘教授科研启动基金项目(51900902006)野外调查采样得到云南省地质调查院王外全所长、杨清标高工、胡永兴和米云川工程师的大力协助;锆石定年由加拿大多伦多大学Sandra L.Kamo完成;同位素实验得到中国科学院地质与地球物理研究所储著银研究员指导;成文过程中莫宣学院士和牛耀龄教授提出了宝贵的建议;导师 |
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| 摘 要： | 半坡杂岩体位于滇西澜沧江构造岩浆带南段，岩体主要由橄榄岩、辉石岩、辉长岩和辉长闪长岩等镁铁 超镁铁质岩组成。通过ID-TIMS锆石U-Pb年代学方法对半坡杂岩体中辉长闪长岩进行精确定年，获得其结晶年龄为(294.9±2.6) Ma，表明半坡杂岩体的形成时代为早二叠世。半坡杂岩体中不同类型岩石微量元素、稀土元素和同位素组成相似，均呈现轻稀土元素(LREEs)相对于重稀土元素(HREEs)弱到中等富集，高场强元素Nb、Ta、Zr和Hf相对亏损的特征，εNd(t=295 Ma)为正值，在+3.4~+6.6，接近亏损地幔值，这些特征与典型的大洋岛弧玄武岩的特征相似。混合计算表明，半坡杂岩体母岩浆为地幔楔部分熔融，加上约2%~7%源于大洋俯冲沉积物的富硅熔浆和蚀变洋壳流体形成的岛弧玄武质岩浆。上述年龄和同位素数据提供了早二叠世早期南澜沧江地区洋内俯冲的可靠证据。
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| 关 键 词： | U-Pb年龄 锆石 ID-TIMS 弧岩浆作用 半坡杂岩体 澜沧江 |
| 收稿时间： | 2011-09-25 |
| 修稿时间： | 2011-11-16 |
Precise ID-TIMS zircon U-Pb age,whole-rock geochemistry and plate tectonic setting of the Banpo Complex in the southern Lancangjiang arc terrane,Sanjiang area,SW China |
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| Li Gangzhu,Su Shangguo,Duan Xiangdong.Precise ID-TIMS zircon U-Pb age,whole-rock geochemistry and plate tectonic setting of the Banpo Complex in the southern Lancangjiang arc terrane,Sanjiang area,SW China[J].Earth Science Frontiers,2012,19(4):96-109. |
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| Authors: | Li Gangzhu Su Shangguo Duan Xiangdong |
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| Institution: | 1.State Key Laboratory of Geological Processes and Mineral Resources;School of Earth Sciences and Resources,China University ofGeosciences(Beijing),Beijing100083,China2.No.2 Gold Geological Party of CAPF,Huhhot 010010,China3.Yunnan Geological Survey,Kunming,650051,China |
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| Abstract: | The Banpo Complex is located in the southern Lancangjiang arc terrane,Sanjiang region,SW China.It mainly consists of wehrlite,clinopyroxenite,gabbro and gabbrodiorite.The U-Pb age of zircons from the gabbrodiorite determined by ID-TIMS is(294.9±2.6) Ma.The rock samples are all characterized by slight-moderate enrichment of light rare-earth elements relative to heavy rare-earth elements and depletion of some high field strength elements such as Nb,Ta,Zr,Hf.These characteristics are similar to those of island arc magmas produced by flux melting in the mantle wedge.Whole rock εNd values for the Banpo Complex vary between +3.4 and +6.6,similar to the values of modern island arc magmas.Positive εNd values coupled by significant negative Nb,Ta,Zr and Hf anomalies for the Banpo Complex can be explained by mixing of magma derived from the mantle wedge with 2%-7% of a partial melt derived from subducted sediments,plus slab fluids from altered oceanic crust.The data from the Banpo Complex provide convincing evidence for Early Permian intra-oceanic subduction in the region. |
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| Keywords: | U-Pb dating zircon ID-TIMS arc magmatism Banpo Complex Lancangjiang |
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