新疆阿尔泰卡鲁安锂矿床锂的富集机制：来自包裹体、矿物学和锂同位素的限定

Li is one of the newly developing national strategic resources. High quality Li resource exploration is imminent under the global new situation that energy metal mineral resources are in urgent need. Granitic pegmatitic Li deposits, which are in high grade and easy to exploit, play an important role in Chinese Li resources. Kaluan granitic pegmatitic Li deposit is unique and is different from other deposits with multiple rare-metal mineralization in Altay, Xinjiang, because of its large scale, simple structural zone, and Li-dominated mineralization. The internal connection and main controlling factors of the separated Li mineralization and multiple rare-metal mineralization are important scientific problems to be solved. This project chooses Kaluan to study, and focus on the pegmatite structural zoning, evolution and property of melt stage to melt-fluid stage to fluid stage, based on systematic field geological investigation and micro-observation. On the basis of melt-fluid evolution, mineralogy, mineral chemistry, and Li isotope geochemistry, we can propose the metallogenic model, the enrichment mechanism of Li, and summarize the metallogenic regularity. This project is helpful to guide further prospecting work, and provide theoretical basis for Li deposit exploration in Altay.

锂是新兴的国家战略性资源之一，在能源金属矿产急需的全球新形势下，寻找高品质的锂矿资源迫在眉睫。花岗伟晶岩型锂矿以其品位高、易于开采等优势，占有我国锂矿资源的重要地位。新疆阿尔泰卡鲁安花岗伟晶岩型锂矿床以其大型规模、伟晶岩结构带简单、以Li矿化为主等特征区别于阿尔泰其它具有多种稀有金属矿化的矿床，具有独特性。单独Li矿化和多种稀有金属组合矿化的内在联系和主要控制因素是一个有待查明的重要科学问题。申请书选择卡鲁安为重点研究对象，拟在系统的野外地质调查和显微观察基础上，重点对伟晶岩分带、熔体-熔流体-流体的性质和演化开展研究，结合各结构带矿物学、矿物化学和锂同位素地球化学研究，探讨锂的富集沉淀机制，建立矿床模型，总结成矿规律。该申请有助于进一步指导找矿勘查工作，为阿尔泰锂矿找矿工作提供理论基础。

卡鲁安是新疆阿尔泰具有代表性的大型锂辉石矿床。本项目开展了矿区地质特征、年代学、矿物化学、成矿流体性质及Li同位素研究，探讨了成矿作用，建立了成矿模式。矿区已发现15条锂矿化伟晶岩脉，规模较大的有807、806和805号脉。卡鲁安伟晶岩结构带简单，以锂辉石-石英-钠长石带为主，边部发育白云母-石英（-钠长石）带和细粒伟晶岩带，矿化以锂为主，含有少量铌钽。利用LA-ICP-MS锆石U-Pb定年获得矿区红柱堇青黑云石英片岩年龄为502.4±4.2Ma，为晚寒武世，不属于前人划定的库鲁木提群；806号脉年龄为204.7±5.3Ma，形成于晚三叠世。卡鲁安含锂伟晶岩分异演化晚期阶段的成矿流体中高温（集中于240~320℃）、中低盐度（2~10wt.% NaCleq）的H2O+NaCl+CO2（±CH4/N2）体系，形成深度约为10~11km。卡鲁安矿区主要伟晶岩脉中的钠长石、钾长石、云母、锂辉石、石榴石、铌钽矿物的主微量元素特征表明，这些伟晶岩脉形成于相对平衡条件下的结晶环境，各内部相带均达到了较高的演化程度，其中807号脉的演化程度最高。锂辉石的δ7Li为-4.64‰~5.44‰，平均值为0.14‰，暗示成矿物质来源于古老壳源。综上，结合前人研究成果，探讨了卡鲁安锂辉石伟晶岩的形成过程，构建了成矿模式。