地学前缘 ›› 2009, Vol. 16 ›› Issue (1): 125-133.

• 论文 • 上一篇    下一篇

1.5 GPa、950 ℃下块状斜长角闪岩部分熔融微量元素的分配特征

  

  1. 1中国科学院 贵阳地球化学研究所 地球深部物质与流体作用地球化学实验室, 贵州 贵阳 550002
    2中国科学院 研究生院, 北京 100049
    3中国科学院 地质与地球物理研究所, 北京 100029
    4中国地质大学 地质过程与矿产资源国家重点实验室, 湖北 武汉 430074

  • 出版日期:2009-02-02 发布日期:2009-02-02
  • 通讯作者: 周文戈。 E-mail: wengezhou@163.com
  • 作者简介:万方(1983—),男,硕士,实验岩石学专业。
  • 基金资助:

    国家自然科学基金项目(40873052);中国科学院知识创新工程重要方向项目(KJCX2SWN20)和西部之光联合学者项目(2008年度)

The partition characteristic of trace elements in the partial melting massive amphibolite at 15 GPa and 950 ℃

  1. 1Laboratory of Earths Interior and Geofluid Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
    2Graduate School, Chinese Academy of Sciences, Beijing  100049, China
    3Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
    4State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China

  • Online:2009-02-02 Published:2009-02-02

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摘要：

在1.5 GPa,950 ℃,恒温101 h条件下对华北北缘太古宙地体中的斜长角闪岩块状样品进行了脱水部分熔融实验,实验产物组合为Hb+Cpx+Gt+Gl,获得的熔体为花岗闪长质成分。利用LAICPMS测试了矿物和熔体的微量元素,获得该体系内各矿物/熔体的微量元素分配系数。角闪石、单斜辉石和石榴石的分配系数与前人在类似条件下的实验结果基本一致。这说明无论实验的初始物质是粉末状还是块状,对元素的分配没有太大的影响。各矿物的REE分配系数对离子半径的拟合曲线很好地符合晶格应变弹性模型。整体特征上,角闪石、单斜辉石和石榴石的LILE,LREE分配系数较低,而HREE的分配系数较高,石榴石具有强烈富集HREE的特征。由此,造成实验熔体表现出LILE、LREE富集而HREE亏损的特征。残留相中无金红石,使得熔体中没有明显的Nb、Ta负异常。熔体的主微量元素特征符合华北北缘中生代埃达克质岩石的基本特征,进一步支持了该类岩石“可能起源于古老下地壳的部分熔融”的成因模式。

关键词: 斜长角闪岩; 块状; 部分熔融; 分配系数; 花岗闪长质

Abstract:

Abstract:  We have performed partial melting experiments on a massive amphibolite sample under 1.5 GPa and 950 ℃ for 101 hours: the sample was collected from Archaean terrain in the northern margin of the North China craton. Experimental products consisted of Hb+Cpx+Gt+Gl and the melt is granodioritic in composition. Trace element compositions of melt and minerals were measured by LAICPMS to get the partition coefficients (Ds) between minerals and melt in the system. The Ds of amphibole, clinopyroxene and garnet are consistent with the previous studies under similar conditions, which indicates that the state of the starting material has little effect on the Ds between minerals and melt. The curve of Ds of REE versus ionic radius for each mineral is coincident with the lattice strain elastic moduli very well. On the whole, the Ds of LILE and LREE for amphibole, clinopyroxene and garnet are lower; the Ds of HREE are higher relatively; garnet is enriched in HREE intensively. Thus, the melt is enriched in LILE, LREE and depleted in HREE. Since there is no rutile in restites, the melt does not show negative Nb and Ta anomaly obviously. The major and trace element characteristics of melt are consistent with the Mesozoic adakitic rocks in the eastern North China craton, which approves the hypothesis that these rocks “could have been derived from the partial melting of ancient lower crust”.

Key words:

Key words: amphibolite; massive; partial melting; partition coefficients; granodioritic

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