Geological Characteristics And Uranium Enrichment Regularity Of Uranium-rich Phosphorite In Bahuang, Tongren, Guizhou Province

Uranium is enriched in phosphorite of Tongren Bahuang,Guizhou Province,and are short of systematically research at present.The phosphorite-type uranium deposits are also lack of research over the world,and the relevant data and literature are few.Therefore,exploring the enrichment characteristics of uranium in the phosphate rock in the Bahuang area and further summarizing the enrichment regularity of uranium in the phosphate rock will help to further study of the genesis mechanism of phosphate rock type uranium deposits in the future,thus laying a theoretical foundation for the comprehensive utilization of mineral resources.By means of rock and mineral identification,geochemical analysis and stepwise chemical extraction,the petrology,mineralogy and element geochemistry,Bahuang phosphorite series are mainly studied.The geological characteristics and mineral characteristics of uranium-rich phosphorite are systematically studied,the enrichment characteristics of uranium are analyzed,and the enrichment regularity of uranium is summarized.Major achievements are as follows:?1?Uranium enrichment layer has obvious regularity in vertical direction.The uranium-rich phosphorite series occurs at the bottom of the Niutitang Formation of the Lower Cambrian,with the siliceous rock of the Laobao Formation as its floor;the uranium-rich strata are mainly phosphorite strata at the bottom of the phosphorite series and a thicker strata of phosphorus rock in the middle part of the phosphorite series.?2?Strong tectonic activity is conducive to th enrichment of uranium.The Bapan anticline has obvious controlling the uranium-rich phosphorite series,and the enrichment of uranium in the eastern wing of the anticline is more strongly than that in the western wing;the uranium-rich section has more strong structural activity traces,such as faults,secondary folds,wrinkling structures,joints,mirror scratches and"cleavage"structures.?3?Uranium-rich rocks have specific mineral assemblages.Uranium-rich phosphorite is composed of apatite-clay mineral-siliceous mineral assemblage and collophanite-clay mineral assemblage,which contains a small amount of fine-grained pyrite.Uranium-rich phosphorus rock is rich in clay minerals,organic matter and fine-grained,strawberry-shaped pyrite.The enrichment of uranium in phosphorite is related to apatite,collophanite and other phosphorous minerals,in which the main occurrence state of uranium is isomorphic,while in phosphorus rock,uranium is more related to clay minerals,pyrite,organic matter and so on,in which uranium exists in the form of adsorption.?4?There are three different types of pyrite in the phosphorite series in the study area,fine granular pyrite,strawberry pyrite and vein pyrite.Compared with coarse-grained crystals,fine-grained pyrite has larger specific surface area,which is more conducive to the effective adsorption of uranium.Uranium-rich phosphorus rocks are rich in fine-grained and strawberry-like pyrite,and the specific surface area of pyrite increases.They can adsorb and enrich uranium on the surface for many times,which is conducive to the enrichment of adsorbed uranium in uranium-rich phosphorus rocks.?5?The enrichment characteristics of uranium are closely related to the occurrence state of uranium in phosphorite series.Through the stepwise extraction andelectron probe analysis,it is proved that the uranium minerals corresponding to the carbonate state and the residual state and the isomorphic forms corresponding to the acid extraction state are the main forms of uranium in the phosphorite series in Bahuang,Tongren.Water-soluble,exchangeable ionic state,iron-manganese oxide state and organic pyrite state,which corresponding to the adsorption state is a secondary form of uranium occurrence.In uranium-rich phosphorite,the content of acid-extracted uranium is high,which accounts for a large proportion.Therefore,it is considered that uranium in the form of isomorphism occurs in the lattice defects of apatite and collophanite;Uranium-rich phosphorous rocks are rich in clay minerals and pyrite,and uranium mainly exists on the surface of clay minerals and pyrite particles in the form of adsorption.Due to the low content of phosphorus and uranium in carbonaceous shale,uranium is the main form of uranium element.?6?Uranium-rich rocks are highly enriched in U,Mo,Ni,V and Ba,and there is a significant negative correlation between uranium and SiO₂ content in minerals,silica is not conducive to uranium enrichment.Uranium in phosphorite samples is positively correlated with P₂O₅ and CaO content,but not with Al₂O₃,K₂O,Na₂O and Fe₂O₃.Uranium occurs in apatite and collophanite in the form of isomorphism.-The content of uranium in phosphorus rock is correlated with clay minerals such as Al₂O₃,K₂O,Na₂O and Fe₂O₃,while the content of P₂O₅ is low and the content of CaO is very low.Uranium mainly exists in clay minerals and pyrite in adsorption state.?7?Frequent hydrothermal activities have helped enrich uranium.The alteration of ore-bearing strata is strong,pyrite veins,quartz veins and calcite veins are developed,the mirror features of uranium-rich rock development,the enrichment of hydrothermal characteristic elements such as U,Sb and Ba,negative Ce anomalies and positive Eu anomalies,mantle-derived sulfur dominated by sulfur isotopes,crustal-derived sulfur or sea-water sulfur mixing,and many other characteristics reveal that hydrothermal activities are frequent,and tectonic hydrothermal activities strongly affect the activation and migration of uranium.