碱性闪石12种阳离子占位度的X射线衍射测定

对所收集的４７个碱性闪石结构数据计算出理论Ｘ射线粉末图，同时实测出５个碱 性闪石样品的粉末图及其晶体化学占位，从这５２个样品的Ｘ射线衍射圈中选出１８条特征衍射 强度，将强度比值与各晶位各阳离子占位用多元统计分析统计出经验公式，以之作为估算未知 样品各阳离子占位的线性模型。回代实践表明，本线性模型具有较钙质闪石更高的可靠性与精 确度。预测５个实测样品的晶体化学类型与原定名对比完全符合，准确度达１００％。按国际分 类表纠正个别样品原定名的错误。在１２种阳离子占位中，估算的准确度有８种大于９０％，３种 近于９０％！唯有Ｔ位Ｓｉ的准确度仅６６％，这可能是因为所选样品中Ｔ位基本上为Ｓｉ占位，其 占位数均超过 ７．５，占位度均大于 ０.９，总变化幅度小从而降低其相关性。因 ５２个样品中，也包 含钠钙闪石亚族，故对整个闪石族用Ｘ射线衍射估算阳离子占位的问题已基本解决。

X-RAY DIFFRACTION DETERMINATION OF 12 CATION SITE OCCUYPANCIES OF ALKALINE AMPHIBOLES

Based on studies on theoretical X-ray powder diffraction patterns obtained from structure data of 47 collected alkaline amphiboles and also on measured powedr patterns and crystallochemical site occupancies of 5 amphibole samples, empirical formulas were deduced after pluristic statistical analyses had been done to intensity ratios and canon site occupancies. Those formulas were then used to estimate linear models of canon site occupancies for new samples to be measured. It has been tested through re-substitution that the established models are more reliable and accurate than those for calcium amphiboles. Crystalic-chemical types predicted for 5 samples to be measured are totally coincident with the nominated, showing a 100% accuracy. According to the international classification, some errors on nomination were corrected. Among the 12 types of canon occupancies, 8 showed an accuracy better than 90%, while 3 reached 90% ! Only Si site occupancy in T site showed a lower accuracy of 66%. It may be caused by the total Si occupancies in T site in the selected sample. Its site occupancies are all alove 7.5 and occupancy degree higher than 0.9. The correlation decreased done to little change in the total occupants. As Na-Ca sub-amphiboles appeared among the 52 samples, the method of estimating canon occupancied by X-ray diffraction is suitable to all amphiboles.