Chemistry and Evolution of Fergusonite—Group Minerals,Bayan Obo,Inner Mongolia
摘要
A new classification scheme of the fergusnoite-group minerals is suggested on the basis of mineral chem.-istry and high temperature XRD.A number of new varieties such as M-thorian fergusonite-(Ce),M-neodymian fergusonite-(Ce),T-titanian fergusonite-(Nd) and T-yttrian fergusonite-(Nd) have been rec-ognized in the light of detailed chemical studies,particularly with reference to REE,SRE and solid solution relationship.The results indicate strong REE and SRE differentiation and evolution in the fergusonite group,which can be interpretated by differences in the stability of various REE complexes in response to vari-ations in physicochemical conditions during the multi-stage mineralization process in the Bayan Bbo ore de-posit.The crystallization of the minerals is closely related to hydrolysis of REE and Nb complexes,REE(OH)3 ·Nb(OH)5 coprecipitation,dehydration,polymerization and nucleation.The significance of SRE(Eu) in the western part of the deposit is emphasized.