白云鄂博主矿云母型矿石中钍矿物的赋存状态微观分析

Microanalysis of occurrences of thorium minerals in mica-type ore of the main orebody in the Bayan Obo deposit

白云鄂博矿床赋存有丰富地钍资源,为更好地开发利用钍资源,本文采用SEM-EDS-AMICS联合分析测试技术结合化学分析法对主矿云母型矿石的化学成分、矿物组成、钍矿物赋存状态等进行系统研究。结果表明,云母型矿石化学成分和矿物组成复杂,矿石中铁品位为8.19%,稀土(RE_(2)O_(3))品位为1.15%,钍(ThO_(2))品位达到0.21%,Th以独立矿物为主,少量呈类质同象形式赋存于独居石中。Th主要以独立矿物钍石的形式存在,矿物粒径分布在5~50μm之间不等,呈浑圆状、他形粒状结构,主要嵌布于云母、方解石等脉石矿物粒间,部分钍石与稀土矿物紧密共生,赋存于独居石颗粒边界,少量呈现包裹与被包裹的特征或以细脉状充填于独居石裂隙中。矿区钍石与稀土矿物独居石及晚期硫化物方铅矿、磁黄铁矿脉体的复杂共伴生关系表明,矿区经历了多期次的热液作用从而导致了现今复杂的钍矿化现象。

There is abundant thorium resource in the Bayan Obo deposit.In order to better develop and utilize the thorium resource,the chemical composition,mineral composition,and thorium mineral occurrence states of the mica-type ore of the main orebody in the mine have been systematically studied by using the SEM-EDS-AMICS technique combined with chemical analysis in this paper.The results show that the mica-type ores have complicated chemical compositions and mineral components,with iron grade of 8.19%,rare earth grade(RE_(2)O_(3))of 1.15%,and thorium grade(ThO_(2))of 0.21%,respectively.Th occurred mainly in form of independent minerals.A small amount of Th occurred in form of isomorphism in monazite.Th mainly occurred in the form of independent mineral of thorite.Its particles have sizes ranging from 5μm to 50μm,with round and anhedral granular textures.Its particles were mainly embedded in the intergranular of gangue minerals such as mica and calcite.Some thorite particles are closely associated with rare earth minerals as they occured in the boundary of monazite grains,with a small amount of them encapsulated and enclosed in monzite or infilled in form of veinlets in monazite fissures.The complicated intergrowth and associated relationships among thorite,monazite and late stage sulfide veins of galena and pyrrhotite in the deposit indicated that the complicated thorium mineralization phenomena in the deposit were resulted from multi-stages hydrothermal fluids.