石榴石对稀有金属伟晶岩岩浆-热液演化过程的指示：以湘北仁里矿床为例

稀有金属伟晶岩浆由于高度富H2O，经历了复杂的岩浆-热液分异过程，对该过程的完整解读是研究稀有金属成矿机制的关键。已有研究多重视岩浆阶段，而伟晶岩演化晚期的热液体系作为稀有金属成矿的重要阶段，缺乏足够重视和充分研究。石榴石由于良好的元素封闭性、稳定性及高灵敏度，可有效指示伟晶岩岩浆-热液分异演化过程。本申请拟选择具有多阶段演化-多稀有金属矿化组合的湘北仁里矿床，以伟晶岩岩浆-热液分异演化过程为主线，对各演化阶段的石榴石样品开展系统的显微结构观察、红外光谱分析和矿物原位微区分析。通过石榴石中OH含量和主微量元素组成，揭示伟晶岩岩浆-热液演化过程中流体的出溶和元素的迁移，建立指示流体大量出溶、划分各演化阶段的石榴石标型特征，研究各阶段中稀有金属元素的迁移、富集特征，以完善稀有金属伟晶岩岩浆-热液成矿理论。

The magma of rare metal pegmatite has experienced a complex magmatic-hydrothermal evolution process due to its high H2O content. The comprehensive study of magmatic-hydrothermal evolution process is the key to understand the rare metal metallogenic mechanism of pegmatite. Much attention has been paid to the magmatic stage, while the hydrothermal system in the late stage of pegmatite evolution, as an important stage of rare metal mineralization, lacks sufficient attention and research. Because of the characteristics of good elementary closure, stability and high sensitivity, garnet can effectively indicate the magma hydrothermal evolution process of pegmatite. This proposal takes the Renli deposit in north Hunan province as the research topic due to its characteristics of multi-stage evolution and different rare metal mineralization combination. Taking the magmatic-hydrothermal evolution process as the principal line, we plan to carry out systematic microstructure observation, Fourier transform infrared spectroscopy analysis and in-situ analysis of major, trace element compositions of garnets. Based on the OH content and the composition of major and trace elements in garnet, the evolution of water activity and the migration of elements during the magmatic-hydrothermal evolution will be revealed. And the typomorphic characteristics of garnet indicating the dissolution of fluids and the division of each evolution stage will be established. Based on these studies, we discuss the characteristics of migration and enrichment of rare metal elements in each evolution stage. This work will improve the magmatic-hydrothermal metallogenic theory of rare metal pegmatite.