Microanalysis of occurrences of thorium minerals in mica-type ore of the main orebody in the Bayan Obo deposit
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(RE2O3)of 1.15%,and thorium grade(ThO2)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 50pm,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.
AMICSScanning electron microscopeBayan Obothoriumoccurrence state