应用电子探针分析技术研究某铌-稀土矿中铌和稀土元素的赋存状态

铌是一种战略金属,在现代钢铁技术中发挥着非常重要的作用。某铌-稀土矿矿石中的Nb_2O_5平均含量达0.0855%,稀土总量(REO)含量达1.03%,接近铌矿最低工业品位要求,并伴生有稀土矿,因此查明铌和稀土的赋存状态至关重要。由于铌矿物、稀土矿物具有颗粒细小且嵌布特征复杂的特点,在偏光显微镜下不容易发现,而且定名困难,很难达到研究目的,一直是地质分析测试的难点。为查明铌和稀土元素的存在形式以及铌、稀土元素的赋存矿物,本文应用电子探针背散射图像、能谱分析及电子探针波谱定量分析技术对某铌、稀土矿矿石进行分析,主要研究铌矿物和稀土矿物的种类、嵌布关系及化学成分等特征,更准确地分析铌和稀土元素的赋存状态。结果表明:(1)铌元素主要以铌铁矿、含铌金红石的形式存在,其中铌铁矿中Nb_2O_5的平均含量为78.26%,含铌金红石中Nb_2O_5的平均含量为5.26%。(2)稀土元素主要以独居石、氟碳钙铈矿和氟碳铈矿的形式存在,其中独居石中稀土总量(REO)的平均含量为64.84%,氟碳钙铈矿中稀土总量(REO)的平均含量为57.52%,氟碳铈矿中稀土总量(REO)的平均含量为70.61%。(3)铌矿物、稀土矿物分布分散,多包裹于钾长石、方解石及黑云母等脉石矿物中。本研究实现了常规岩矿鉴定手段难以完成的矿物识别和鉴定,查明该矿床矿石中主要的铌矿物和稀土矿物的种类及特征,为后续铌-稀土矿的综合利用提供了科学依据。

Occurrence of Niobium and Rare Earth Elements in Related Ores by Electron Microprobe

BACKGROUND: Niobium is a strategic metal with wide applications and plays a very important role in modern steel technology. The average content of Nb₂O₅ in a niobium-rare earth ore is 0.0855%, and the content of total rare earth (REO) is 1.03%, which is close to the minimum industrial grade requirement of niobium ore. Niobium minerals and rare earth minerals have the characteristics of small particles and complex intergrowths, which makes them difficult to find under a polarized microscope.OBJECTIVES: To investigate the forms of niobium and rare earth elements.METHODS: Electron probe backscatter image, energy spectrum analysis and electron probe spectrum quantitative analysis were used to analyze niobium and rare-earth ore.RESULTS: Niobium mainly existed in the form of niobite and niobium-bearing rutile. The average content of Nb₂O₅ in niobite was 78.26% and that in niobium-bearing rutile was 5.26%. Rare earth elements mainly existed in the form of monazite, bastnaite and bastnaesite. The average content of rare earth elements (REO) in monazite, bastnaite and bastnaesite was 64.84%, 57.52% and 70.61%, respectively. Niobium and rare-earth minerals were distributed and dispersed. They were mostly trapped in the gangue minerals such as potassium feldspar, calcite and biotite.CONCLUSIONS: The types and characteristics of the main niobium and rare earth minerals in the ore deposit were identified. This study has important guiding significance for the comprehensive utilization of niobium and rare earth deposits in the future.