New Varieties of Na-Ca-Ba-RE Fluorocarbonate Series Minerals

来自 : en.cnki.com.cn/Article_en/CJFD 发布时间：2021-03-25

Yang Zhu-Ming; Zhang Pei-Shan;Tao Ke-Jie(Institute of Geology,Academia Sinica,Beijing 100029,China) The unnamed Sr rich mineral and Ca-rich baiyunehoite-(Ce) were found in the Khibina alkali massif Kola Peninsula, and the Baiyun Ebo Nb- Ta- REE deposits, Inner Mongolia, respectively. Their chemical formulas based on electron microprobe analysis are and (Ca(0.46),Na(0.28) 0.16)0.09Ba(1.03)(Ce0.82,Sr0.38La0.35,Nd0.32,Pr0.09,Sm0.01)1.97(CO3)4F and (Na0.44,Ca0.32,0.24)1.00Ba1.07(Ce1.03,La0.46,Nd0.26,Pr0.08,Sr0.08,Sm0.02)1.93(CO3)4)F respectively. X-ray diffraction study yields the unit-cell parameters: a=0.5091 nm, c=2.302 nm for the unnamed Sr- rich mineral and a=0.5110 nm, c=2.313 nm for Ca-rich baiyuneboite (Ce). Both minerals are the intermediate member of the isomorphous series minerals between the unnamed mineral(Ca0.5,0.5)BaCe2(CO3)4 F and baiyune- boite-(Ce)NaBaCe2(CO3)4 F. The ionic radius analysis and the bond valence calculation on the basis of the structure of baiyuneboite- (Ce) indicate that Sr2+ occupies the Ce site preferentially. while Ca2+ occupies the Na site preferentially. The charge balance is maintained by a combinalion of Na++RE3+= Ca2++ Sr2+ and 2Na+=Ca2++ Download(CAJ format) Download(PDF format)
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