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    全球淡色花岗岩的地球化学特征及其与稀有金属的成矿联系

    Geochemical characteristics of global leucogranite and their mineralized relationship with rare metals

      摘要
    • 摘要:
      研究目的 近年来，淡色花岗岩成为岩石学和稀有金属成矿学研究的热点，但全球淡色花岗岩的时空分布特征尚不明确。本文旨在探讨全球淡色花岗岩的时空分布特征及其成矿专属性，进而指导勘查实践。
      研究方法 文章系统梳理了全球115个淡色花岗岩体1155组地球化学数据，并结合项目组在南岭、川西、藏南、阿尔泰等地的工作，对数据开展综合分析研究。
      研究结果 在成分上，淡色花岗岩的SiO2含量较全球花岗岩平均值高1%以上，发生稀有金属矿化的岩体稀土含量极低。在空间上，中西欧海西造山带淡色花岗岩的SiO2和ALK（Na2O+K2O）含量低于喜马拉雅淡色花岗岩，也低于中国西部淡色花岗岩，而中国西部淡色花岗岩的SiO2和ALK含量又低于中国东部的淡色花岗岩，中西欧和北美地区的淡色花岗岩富集P2O5；样品中Li、Be、Nb、Ta、Ga、Rb和Sn含量的最高平均值均出现在中西欧地区，W含量最高平均值出现在中国东部。在时间上，新生代淡色花岗岩的SiO2和ALK含量高于古生代，低于中生代；古生代淡色花岗岩富集P2O5；电气石是新元古代淡色花岗岩的一个重要矿物特征。
      结论 成矿的淡色花岗岩一般不含岩浆型石榴子石，A/CNK>1.2，与Sn–W–Nb–Ta成矿有关的淡色花岗岩的Rb/Sr>1，ΣREE>10×10−6，与Li–Sn–Nb–Ta–Be成矿有关的淡色花岗岩的Rb/Sr>1，ΣREE<10×10−6。相比之下，中国东部中生代淡色花岗岩演化程度最高，成矿潜力最好。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective Recently, leucogranites have become a hot spot in the study of petrogenesis and rare metal metallogeny. However, the spatiotemporal distribution characteristics of global leucogranite are still unclear. For further prospecting of rare metals in China, it is essentially to clarify the spatiotemporal distribution of leucogranite and the metallogenic specialization between leucogranite and rare metal deposits.
      Methods We collect 1155 geochemical data from 115 leucogranites worldwide, and combine with our recently achievements from the Nanling Region, Western Sichuan, Southern Tibet, and Altai.
      Results In reference to the composition, this study reveals that the content of SiO2 in leucogranite is exceed 1% higher than the global average value of granite, while the REE content of the rocks with rare metal mineralization is extremely low. Spatially, the content of SiO2 and ALK (Na2O+K2O) of leucogranites in the Hercynian orogenic belt in Central and Western Europe are lower than those of the Himalayan leucogranites, as well as those of Western China. Meanwhile, the SiO2 and ALK content of leucogranite in Western China are lower than Eastern China. Both leucogranites in Central and Western Europe and North America are rich in P2O5. The highest values of Li, Be, Nb, Ta, Ga, Rb and Sn in the samples appear in Central and Western Europe, while the highest values of W present in eastern China. Cenozoic SiO2 and ALK content of leucogranite were higher than Paleozoic but lower than Mesozoic. Notablely, Paleozoic leucogranite are enriched in P2O5. Besides, tourmaline is a vital indicator of Neoproterozoic leucogranite.
      Conclusions The mineralized leucogranite are generally lack of magmatic garnet. Those leucogranite with feature of A/CNK>1.2. Rb/Sr>1, ΣREE>10×10−6 are mostly related to Sn–W–Nb–Ta mineralization, while Rb/Sr>1, ΣREE<10×10−6 of leucogranite more akin to Li–Sn–Nb–Ta–Be mineralization. All the data indicate that the Mesozoic leucogranites in Eastern China are the most evolved leucogranites worldwide and the best mineralization potential.

       

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