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首页> 外文期刊>Journal of Asian earth sciences >The compositional variation of I-type granites: Constraints from geochemical analyses and phase equilibrium calculations for granites from the Qinling orogen, central China
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The compositional variation of I-type granites: Constraints from geochemical analyses and phase equilibrium calculations for granites from the Qinling orogen, central China

机译：I型花岗岩的组成变化：来自中国中部秦岭奥根原的地球化学分析及相平衡计算的约束

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摘要

There is a large compositional variation of I-type granites. Although partial melting and fractional crystallization are the two primary mechanisms for the variation, it is intriguing to know how they jointly work. This issue is addressed by a combined study of geochemistry and phase equilibrium modelling for a Triassic pluton from the Qinling orogen. The pluton consists of high-K, calc-alkaline I-type granites. Geochemical results suggest that the granites are likely sourced from Triassic mafic-intermediate igneous rocks. Compared with experimental melts, it is inferred that the natural granites are not the crystallized product from pure magmatic melts. This is confirmed by phase equilibrium calculations that have utilized the Triassic mafic-intermediate igneous rocks as the source, yielding modelled melts that contain too low FeOt, MgO and Mg# to match the target granites. The addition of restitic mineral assemblages to melts can relieve the discrepancy, but the modelled magmas have much higher CaO than the granites. Replacing equilibrium melting by disequilibrium melting in terms of the plagioclase behavior can lead to a satisfactory match. Furthermore, by taking the average of the target granites as a parental magma, the modelled crystalline products can well reproduce the variation trends in the high-K, calc-alkaline I-type granites from the Qinling orogen. In this regard, the crustal anatexis would produce the parental magma at first, which experienced fractional crystallization to form the granitic pluton with the compositional variation as observed. Therefore, these two processes would jointly lead to the compositional variation of I-type granites in nature.
机译：I型花岗岩存在大的组成变化。虽然部分熔化和分数结晶是变化的两个主要机制，但知道它们是如何联合工作的兴趣。从秦岭造型的地球化学和相均衡建模的组合研究解决了这个问题。芦苇由高k，钙碱I型花岗岩组成。地球化学结果表明，花岗岩可能来自三叠系麦克风中间火岩石。与实验熔体相比，推断天然花岗岩不是来自纯岩浆熔体的结晶产物。这通过相位平衡计算确认，所述相位平衡计算利用Triassic Mafic-中间体的火岩作为源，产生含有太低的熔体，含有太低的感光，MgO和Mg＃以匹配目标花岗岩。添加腰部矿物组合以融化可以缓解差异，但是模型的岩浆比花岗岩更高的曹米。通过普拉基酶行为的不平衡熔化更换平衡熔化可导致令人满意的匹配。此外，通过将目标花岗岩的平均值作为父母岩浆，所建模的结晶产品可以很好地再现来自秦岭造山的高k，钙碱I型花岗岩中的变化趋势。在这方面，结壳anatexis首先产生父母岩浆，其经历了分数结晶，以形成花岗岩芦苇，以与观察到的组成变异。因此，这两种方法将共同导致I型花岗岩的组成变化性质。

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  • 来源
    《Journal of Asian earth sciences》 |2020年第15期|104471.1-104471.14|共14页
  • 作者

    Gao Peng; Lu Ying-Hui; Zhao Zi-Fu; Zheng Yong-Fei;

  • 作者单位

    Univ Sci & Technol China Sch Earth & Space Sci CAS Key Lab Crust Mantle Mat & Environm Hefei 230026 Peoples R China|Chinese Acad Sci Ctr Excellence Comparat Planetol Hefei 230026 Peoples R China;

    Univ Sci & Technol China Sch Earth & Space Sci CAS Key Lab Crust Mantle Mat & Environm Hefei 230026 Peoples R China;

    Univ Sci & Technol China Sch Earth & Space Sci CAS Key Lab Crust Mantle Mat & Environm Hefei 230026 Peoples R China|Chinese Acad Sci Ctr Excellence Comparat Planetol Hefei 230026 Peoples R China;

    Univ Sci & Technol China Sch Earth & Space Sci CAS Key Lab Crust Mantle Mat & Environm Hefei 230026 Peoples R China|Chinese Acad Sci Ctr Excellence Comparat Planetol Hefei 230026 Peoples R China;

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  • 正文语种 eng
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  • 关键词

    I-type granites; Crustal source; Partial melting; Fractional crystallization; Phase equilibrium; Chemical variation;

    机译：I型花岗岩;地壳源;部分熔化;分数结晶;相平衡;化学变化;

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