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首页> 外文期刊>Journal of Asian earth sciences >Evidence for crustal contamination in intra-continental OIB-like basalts from West Qinling, central China: A Re-Os perspective
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Evidence for crustal contamination in intra-continental OIB-like basalts from West Qinling, central China: A Re-Os perspective

机译：来自中国中西部秦岭的陆缘类OIB玄武岩中地壳污染的证据：Re-Os观点

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摘要

The magnitude of crustal contamination in intra-continental OIB-like basalts is commonly difficult to assess in terms of major, trace-element and Pb-Sr-Nd isotopes. However, the Re-Os isotope system is a very sensitive tracer of the crustal component during formation of basaltic rocks. Here we report new Sr-Nd-Pb-Os geochemical and isotopic data from the Cretaceous Duofutun Volcanic Rocks (DVRs) of West Qinling, central China. The DVRs exhibit low Os abundances (4.46-42.02 ppt) with Re abundances ranging from 45.58 to 812.98 ppt, variably high Re/Os (3-126), and high initial ~(187)Os/~(188)Os ratios (0.2112-0.6784). We propose that the degree of partial melting is responsible for the first-order control on the variation of Os concentrations. Even the least radiogenic sample still possesses a higher initial ~(187)Os/~(188)Os ratio than the primitive upper mantle, implying a non-negligible contribution from high Re/Os and ~(187)Os/~(188)Os reservoir(s). Both the crust and pyroxenite-rich mantle are reliable candidates, but the latter cannot be reconciled with the Os mass balance between pyroxenite and ambient peridotite. Hence, we contend that these rocks were contaminated by crustal materials en route to the surface. Assimilation/fractional crystallization modeling manifests the observed isotopic variations can be produced by minor assimilation of the Proterozoic mafic lower crust. In addition, the intra-continental OIB-like basalts show a relatively wider range of ~(187)Os/~(188)Os ratios in comparison with MORB and OIB, confirming the continental crust can have a higher concentration of radioactive Os, which is induced by time-integrated growth.
机译：就主要，痕量元素和Pb-Sr-Nd同位素而言，陆上OIB样玄武岩中地壳污染的大小通常很难评估。但是，Re-Os同位素系统是玄武岩形成过程中地壳成分的非常灵敏的示踪剂。在这里，我们报告了来自中国中西部西秦岭白垩纪多福屯火山岩（DVR）的新Sr-Nd-Pb-Os地球化学和同位素数据。 DVR的Os丰度低（4.46-42.02 ppt），Re丰度范围从45.58至812.98 ppt，可变的Re / Os（3-126）高，初始〜（187）Os /〜（188）Os比率高（0.2112） -0.6784）。我们建议部分熔化的程度负责对Os浓度变化的一阶控制。甚至最不放射源的样品仍具有比原始上地幔更高的初始〜（187）Os /〜（188）Os比，这意味着高Re / Os和〜（187）Os /〜（188）的贡献不可忽略。 Os水库。地壳和富含辉石的地幔都是可靠的候选者，但是后者不能与辉石和周围橄榄岩之间的Os质量平衡相一致。因此，我们认为这些岩石在到达地面的过程中受到地壳物质的污染。同化/分数结晶模型表明，观察到的同位素变化可以由元古代的铁镁质下部地壳的少量同化产生。此外，与MORB和OIB相比，陆内类OIB类玄武岩的〜（187）Os /〜（188）Os比范围相对较大，这证实了陆壳中放射性Os的浓度较高。是由时间整合的生长诱导的。

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  • 来源
    《Journal of Asian earth sciences》 |2015年第2期|436-445|共10页
  • 作者

    Xiaowei Li; Jie Li; Thomas Bader; Xuanxue Mo; Mark Scheltens; Zhenyu Chen; Jifeng Xu; Xuehui Yu; Xiongfei Huang;

  • 作者单位

    State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China,Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China,School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China;

    School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;

    State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China;

    School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;

    MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, PR China;

    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China;

    State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China;

    State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China;

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  • 正文语种 eng
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  • 关键词

    Re-Os isotopes; West Qinling; Intra-continental basalts; Crustal contamination;

    机译：Re-Os同位素;西秦岭陆内玄武岩;地壳污染;

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