Brannerite Crystallization Pattern and Its Indicating Significance for Uranium-polymetallic Mineralization in Black Rock Series of Northwestern Hunan
Because of its special mineralogical properties,brannerite is basically produced in nature by metamorphosis,so its original structure data is difficult to measure accurately.By the integrated methods of α-particle track etching,SEM backscatter image,energy spectrum analysis,element mapping and so on,most of the brannerite in the black rock series in northwestern Hunan was found crystallizing directly from the mineralization solution,with a high degree of idiomorphic,mainly in the shape of needles and slats.A small part brannerite was formed by metasomatic rutile,ilmenite and other earlier minerals,the brannerite crystal form formed in this way is poor and the degree of idiomorphic is low,in most cases the residual crystalline form of replaced minerals can be examined.A few brannerite was formed by hydroxides or oxides containing uranium and titanium which hydrothermal transformation and recrystallization by ore-bearing solution,the mineral particles of brannerite formed in this way are small,mostly in the form of needles,sometimes in the form of radial aggregates.The above findings not only provide more detailed physical samples for the study of branneritein natural conditions,but also provide mineralogical basis for the development and utilization of uranium polymetallic mining technology in black rockseries.The statistical research found that the average organic carbon content of oolitic apatite is 21.18%,the average organic carbon content of partially dissolved apatite is 11.49%,and most of the recrystallized apatite does not contain organic carbon.Combining with the mineralogical study of black rock series,it was believed that the mineralized elements carried in the submarine exhalation hot water precipitated and enriched in the micro-voids,micro-cracks and mineral gaps of black rock series through exsolution and reduction,generated different types of uranium polymetallic minerals such as brannerite,pitchblende,gersdorffite and galena.
branneriteblack rock seriesapatiteexsolutionnorthwestern Hunan
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