钙稀土氟碳酸盐系列矿物新规则堆垛结构的透射电镜研究

TRANSMISSION ELECTRON MICROSCOPE STUDY OF THE NEW REGULAR STACKING STRUCTURE IN THE CALCIUM RARE-EARTH FLUOROCARBONATE MINERAL SERIES FROM SOUTHWEST CHINA

采用现代透射电镜，研究我国西南某地产出的钙稀土氟碳酸盐矿物，又发现８种新的ＢｍＳｎ型规则混层组分和４种未曾报道的微多型。电子衍射和高分辨晶格象研究揭示了新规则堆垛结构特征及衍生体之间的结构取向关系。阐明了它们是由两个端员矿物－氟碳铈矿（Ｂ）和直氟碳钙铈矿（Ｓ）的结构单元层沿ｃ轴方向以不同比例有序堆垛而成，因而导致了矿物组分和结构的不均一性。

Microstructural characteristics of minerals in the calcium rare earth fluorocarbonate series from southwest China have been studied using transmission electron microscope. In the series the following minerals were found: bastnaesite (B), parisite (BS), roentgenite (BS2), and regular mixed-layer compounds of the B3S2 type as well as eight unreported regular mixed-layer compounds of the BmSn type andfour new micro polytypes. These mixed-layer phases are usually found co-existing in one natural grain of parisite as the syntactic intergrowths. The studies revealed the structural characteristics of them which can be considered to be composed of unit layers of two end members bastnaesite and synthisite in the series by ordered stacking of them in varied proportions along c axis. The studies showed that the microstructure variation of the syntactic intergrowths is very complicated. It is an essential cause that leads inhomogeneity of such minerals.