| 四川甲基卡锂矿床花岗岩体Li同位素组成及其对稀有金属成矿的制约 |
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| 引用本文： | 侯江龙,李建康,张玉洁,李超.四川甲基卡锂矿床花岗岩体Li同位素组成及其对稀有金属成矿的制约[J].地球科学,2018,43(6):2042-2054. |
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| 作者姓名： | 侯江龙 李建康 张玉洁 李超 |
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| 作者单位： | 1.中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室, 北京 100037 |
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| 基金项目： | 华南重点矿集区稀有稀散和稀土矿产调查项目DD20160056川西甲基卡大型锂矿资源基地综合调查评价项目DD20160055中国矿产地质与成矿规律综合集成和服务（矿产地质志）项目DD20160346 |
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| 摘 要： | 四川康定甲基卡超大型锂矿是我国最大的硬岩型锂矿床之一，矿区中南部呈岩株状出露的二云母花岗岩常被认为是成矿伟晶岩的"矿源岩"，对其开展Li同位素地球化学研究，对探讨矿区稀有金属的来源与演化具有重要意义.研究工作基于详细的野外地质调查，采用MC-ICP-MS方法对岩体锂同位素组成开展了研究.研究结果显示，岩体Li含量介于192×10-6~470×10-6，均值为309×10-6，δ7Li值介于-1.56‰~+0.90‰，均值为-0.24‰，与平均上地壳值基本一致，具有高Li低δ7Li的特征.δ7Li与Li、Rb、Ga、SiO2及εNd（t）不存在明显的相关性，岩体锂同位素组成反映了其形成时的源区特征，未受岩浆结晶分异作用和蚀变作用的影响.岩体岩石地球化学、同位素地球化学资料表明，岩浆来源以三叠系西康群砂泥岩的部分熔融为主，可能有部分深源物质的加入.此外，岩体Li同位素的变化规律表明伟晶岩的成矿流体来源于二云母花岗岩.岩体Li含量与Li同位素组合不仅可用来划分锂矿床类型，而且对稀有金属找矿具有一定的指导意义.
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| 关 键 词： | 二云母花岗岩 伟晶岩 锂同位素 甲基卡 矿床 岩石学 |
| 收稿时间： | 2018-01-15 |
Li Isotopic Composition and Its Constrains on Rare Metal Mineralization of Jiajika Two-Mica Granite,Sichuan Province |
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| Abstract: | Jiajika superlarge hard rock type lithium deposit is one of the most abundant lithium mineral resouces in China. The two-mica granite outcropped in the southern Jiajika orefield is generally regarded as source rocks of the ore-bearing pegmatites. Li isotopic composition is a useful tool to explore the origin and evolution of rare metal. Based on the detailed field work, the lithium isotopic composition of granite was tested by MC-ICP-MS in this study. The results show that the lithium content of the granite is from 192×10-6 to 470×10-6, and the mean value is 309×10-6; the value of δ7Li ranges from -1.56‰ to 0.90‰, and the mean value is -0.24‰, which is closed to the average value of upper crust. Jiajika two-mica granite apparently has higher content of lithium and lower value of δ7Li, and the δ7Li and Li, Rb, Ga, SiO2 and εNd(t) have no obvious correlation. Lithium isotopic composition of granite reflects its characteristics of source rock, and it has not been influenced by crystallization differentiation of magma and alteration. The geochemical and isotope geochemistry data indicate that the source of magma is mainly composed of partial melting of Triassic Xikang sand-mudstone, which may have been mixed with materials from deep source. In addition, variations of lithium content and Li isotopic composition show that the fluid of magma migrated from center to the north and south, and the metallogenic fluid of pegmatite is derived from Jiajika two-mica granite. The content of lithium and Li isotopic composition can not only be used to classify the types of lithium deposits, but also can facilitate the prospecting of rare metals. |
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