钙-铈氟碳酸盐矿物中B_mS_n型新多型的发现及其微结构研究

Discovery of New Polytypes of the B_mS_n in the Calcium-Ceyium Fluoro CarbonaTe Minerals and their Microstructural Study

利用Philips CM-12分析型透射电镜对四川昌北大型稀土矿床中钙铈氟碳酸盐矿物进行了研究。除证实氟碳钙铈矿(BS)存在3R和6R2种多型外,首次发现和研究了氟碳钙铈矿(BS)存在4H、12H、18R、24R、30R和36R6种新多型;伦琴矿(BS_2)1种6R新多型和B_2S新规则混层矿物2H、12R和24R3种中新多型。电子衍射和晶格象分析表明:该类矿物中众多新多型的产生,主要是由于矿物结构单元层沿(?)轴有序堆垛和[CO_3]的定向周期性变化所致。

Transmission electron microscopy has been applied to the study of the calcium-cerium fluoro carbonate min-erals in a rare-earth mineral deposit in northern Xichang, Sichuan Province. We have found the following poly-types: parisite(BS)3R and 6R as well as ten unreported new polytypes of the type B_mS_n, which include six poly-types of BS(4H, 12H, 18R, 24R, 30R and 36R), one polytype of roentgenite(BS_2, 6R), three polytypes of new regular mixed-layer mineral of the type B_2S(2H, 12R and 24R). Electron diffraction and lattice images show that occurring of new polytypes in the calcium-cerium fluoro carbonate minerals are formed by order stacking a-long the c axis of the structural layers of the minerals and periodic orientional variation of the[CO_3].