Study On REE Enrichment Mechanism Of Xinmin Bauxite Bottom In The WZD Area,Northern Guizhou,China

It is REE that have important strategic and economic significance.Bauxite is abundant in China and is mainly distributed in the Shanxi,Guangxi,Henan and Guizhou provinces.The bauxite deposits in the WZD area have attracted much attention as an important part of the Southern Chongqing-Central Guizhou bauxite metallogenic belt.Many works have been attributed to the geological features,material source,sedimentary environment.However,the host minerals and the enrichment mechanism for REE are still controversial.Xinmin bauxite is selected to utilized in this article.scanning electron microscopy,electron probe,ICP-MS,stepwise chemical extraction are used to carried out the occurrence of REE at the bottom of the mining layer in this area,combined with mineralization conditions to explore the enrichment mechanism of REE at the bottom of the ore bed.Based on the above methods,combined with previous research results,the following achievements have been mainly obtained:In terms of REE distribution characteristics: The analysis results of the element content of the bauxite profile show that REE is mainly enriched in the chlorite rock at the bottom of the ore layer.Its ?REE content is extremely high,with an average of 1826 ppm and a maximum of 4390 ppm.The LREE content is controlled by content of La,Ce,Nd,and HREE content is controlled by content of Y.In terms of REE occurrence: The REE stepwise chemical extraction results of chlorite claystone shows that REE mainly exists in the residue state,and there is almost no water-soluble state and exchangeable state.The mineral composition in the residue state is mainly clay minerals,followed by heavy minerals,iron minerals and REE independent minerals.A large amount of La,Ce,Nd and Y are found in chlorite.The independent minerals in the residue state are mainly xenotime,parasite,and bastnaesite.REE independent minerals and isomorphism are the main occurrence states of REE at the bottom of the Xinmin bauxite.In terms of REE enrichment mechanism:(1)The analysis of microelements shows that the geochemical process of the Xinmin bauxite is a process of desiliciation and aluminum-rich.During the weathering process,REE migrates and finally enriches at the bottom of bauxite;(2)The study of p H in the ancient media,combined with the formation conditions of REE independent minerals and the alkaline characteristics of REE show that the change of p H in the media restricts the formation of different REE independent minerals.The adsorption of REE is also determined by p H;(3)The ratio of the characteristic trace elements in the Xinmin bauxite mine profile shows that Xinmin bauxite was formed in the complicated environment.REE is easier to be enriched in the environments of reduction,moist and marine;(4)The study of weathering and lithofacies paleogeography shows that the crustal ups caused by tectonic movement and sedimentary environment provide a rich source of Xinmin bauxite and REE.After experiencing four stages and six stages,REE enriched at the bottom of the Xinmin bauxite.