基于流体包裹体原位卤族元素分析探讨白云鄂博稀土矿床海西期岩浆热事件与稀土成矿的关系

白云鄂博是世界上已知最大的稀土矿床，矿区经历了从元古宙至显生宙多期构造演化和岩浆热事件，并导致前人对成矿过程认识的差异。当前，中元古代火成碳酸岩的成因观点得到众多学者的支持，显生宙加里东期的年代数据亦被证实为受碳酸岩岩浆后期的热扰动的结果。但显生宙海西期岩浆活动与稀土矿化的关系却依然存在争议，成为白云鄂博矿床稀土成矿过程研究中亟待解决的关键问题。卤族元素作为可靠的流体示踪计，在区分不同源区岩浆流体方面具有很好的效果。本项目拟在详细的野外地质考察和岩矿鉴定的基础上，分别选取碳酸岩稀土矿体及海西期岩体中蚀变-矿化脉内的流体包裹体作为研究对象，通过流体包裹体岩相学、显微测温、激光拉曼探针、固相组分的电子探针和扫描电镜/能谱、原位LA-ICP-MS传统主微量和卤族元素分析，精确厘定白云鄂博矿床海西期岩浆流体的包裹体记录，查明其物理化学特征及矿化相关性，揭示白云鄂博海西期岩浆热事件与稀土成矿的关系。

The giant Bayan Obo REE-Nb-Fe deposit in Inner Mongolia is the largest REE deposit in the world. Multi-stage tectonism and magmatism developed from Mesoproterozoic to Phanerozoic, leading to complex metamorphism, alteration and deformation of the orebodies and thus hindering our understanding of the REE mineralization process. It is widely accepted that the ore formation was mainly the product of Mesoproterozoic carbonatite magmatism, and the Caledonian geochronologic data was the result of thermal disturbances of the Mesoproterozoic carbonatite magmatism. But the roles of Hercynian magmatism and related hydrothermal event in REE mineralization remain controversy. Halogens as reliable fluid tracers can effectively discriminate magmatic fluids with varying origins. In this proposal, based on detailed field geological investigation and observation of fluid inclusion petrology, in-situ LA-ICP-MS halogen analyses of fluid inclusions from different hydrothermal veins will be carried to distinguish the Hercynian magmatic fluid and reveal its geochemical characteristics. These will be then used as baselines to evaluate the contributions of the Hercynian magmatic events in REE mineralization of the Bayan Obo REE-Nb-Fe deposit, combined with results of microthermometry, laser-Raman spectrum, EMPA, SEM/EDS and traditional single fluid inclusion LA-ICP-MS analyses.