Material Composition Characteristics Of Rare Earth Deposits In Longnan City,Jiangxi Province

China is rich in rare earth resources,especially ion-adsorbed rare earths,which are mainly produced in Gannan.Longnan City occupies an important position in the Gannan ion adsorption rare earth ore collection area,not only producing a large ion adsorption type light rare earth deposit,but also producing the world’s rare Zudong extra-large ion adsorption heavy rare earth deposit.Ashidong heavy rare earth deposits and Guanxi light rare earth deposits can be used as representatives of two types of ion-adsorption rare earth deposits.(1)The two deposits are different.The Zudong deposit is dominated by medium and fine-grained black mica granite and medium and coarse-grained alkali-length granite with hydrothermal alteration such as silicification and chloritization;while the Guanxi deposit is dominated by medium-grained potassium-length granite with minor hydrothermal alteration such as chloritization.(2)There are differences between the two rare earth minerals.Although both are ion-adsorbed rare-earth deposits,many rare-earth minerals are visible.Two types of rare earth minerals in ore deposits,particle size of about 10～100μm,mainly adsorbed state,see a small amount of crystal minerals.The heavy rare earth minerals of the Zudong deposit are mainly titanium yttriumite and arsenopyrite,and a small amount of phosphoric yttriumite,hydrophobic ceriumite and silica-beryllium yttriumite exist;The light rare earth minerals of the Guanxi deposit are mainly fluorocerium cerium ore.The rare earth elements in both deposits are mainly in ionic state in clay minerals.(3)Comparison of rare earth content between the two deposits.The Y,HREE andΣREE contents of the Zudong deposit are significantly higher than those of the Guanxi deposit,while the LREE content and(La/Yb)_N are significantly lower than those of the Guanxi deposit.The HREE of the Zudong deposit shows significant positive correlation with LREE,ΣREE,Ba and Sr;and the LREE of the Guanxi deposit shows significant positive correlation withΣREE.(4)Both are affected by weathering differently.The heavy rare earth enrichment of the Zudong deposit is more affected by weathering,and the heavy rare earth content is highest in the semi-weathered layer and similar in the weakly weathered layer and the fully weathered layer;while the light rare earth enrichment of the Guanxi deposit is less affected by weathering,and the light rare earth content is similar in the slightly weathered layer,semi-weathered layer and fully weathered layer.(5)Discussion on the genesis of rare earth enrichment.The magmatic evolution formed rare earth-rich granite,hydrothermal alteration made REE generally enriched,providing the material source of weathering crust rare earth enrichment into mineralization,and weathering dissolved rare earth minerals into ionic rare earth,and then adsorbed by clay into mineralization.Through relevant research,it is preliminarily believed that the different enrichment of light and heavy rare earths mainly stems from the different degrees of evolution of their magmas.