白云鄂博Fe-REE-Nb矿床铌矿物学和地球化学研究

白云鄂博Fe-REE-Nb矿床是世界上最大的稀土矿床，同时赋存大量铌矿资源，铌矿储量占中国铌储量的63.4%。矿床中铌品位低，铌矿物种类复杂，迄今为止白云鄂博铌矿物研究相对薄弱。查明铌赋存状态和铌矿物成因期次对了解白云鄂博矿床铌矿化过程至关重要，对开采和冶炼也能提供重要科学指导。本项目选取白云鄂博各类铌-稀土矿石，开展系统的铌矿物学和地球化学研究。白云鄂博铌矿化不仅受到碳酸岩浆过程的制约，更受到热液过程的控制，多期铌矿化是白云鄂博矿床最显著的特点。烧绿石作为白云鄂博铌载体之一，对示踪多期热液流体性质具有明显优势。铌铁矿、易解石高精度定年有效地限定了铌成矿年龄。通过扫描电镜、阴极发光、电子探针及LA-ICP-MS等微区系统分析不同阶段铌矿物组成、对比烧绿石、易解石等铌载体的不同结晶域上成分差异，有效解译铌成矿热液性质，厘定铌矿化时代，深入理解白云鄂博多期热液过程中铌迁移-富集-再活化机制。

The Bayan Obo REE-Nb-Fe deposit, which reserves the current largest REE resources globally, also hosts 63.4% of China’s Nb resources. The grade of niobium ores in the Bayan Obo deposit is relatively low and the niobium mineral generations are extremely complex. However, the basic researches of niobium mineralogy are comparatively insufficient. Identifying the occurrence state of niobium, niobium minerals paragenetic association contributes to the deeper understanding of niobium anomalous enrichment mechanism and also provides a solid scientific basis for regional prospecting potential and mineral smelting. We conduct the detailed observations and comparative mineralogical and geochemical analyses on varied Nb-REEs bearing ores from the Bayan Obo deposit. Previous studies confirmed that niobium mineralization is not merely restricted by carbonatite magmatic processes, but directly affected by multiple hydrothermal fluids. The multi-stage Nb mineralization is the most prominent characteristic of Bayan Obo deposit. As one of the niobium carriers in Bayan Obo deposit, pyrochlore is susceptible to hydrothermal alteration and served as a superb tool to fingerprint the physical and chemical properties of multi-stage metasomatic fluids. The niobium mineralization age can be accurately restricted by high precision isotopic dating of columbite and aeschynite. By systematically observing and micro analyzing on varied niobium minerals in different types of ores and contrasting the differences on element and isotopic compositions of distinct domains in individual mineral particle, such as aeschynite, pyrochlore and columbite, using scanning electron microscope (SEM), cathodoluminescence (CL), EPMA and LA-ICPMS techniques, we emphasize the coordinated variations of element contents and isotopes during the mineral alteration processes, trace the physical and chemical properties of multi-stage metasomatic hydrothermal fluids, determine the age of niobium mineralization and decipher the anomalous enrichment and reactivation mechanism of Nb element in Bayan Obo deposit.