碱性长石Al-Si有序化进程中微结构和^(29)Si NMR谱的表现

MICROSTRUCTURES AND ^(29)Si NMR SPCTRA OF ALKALINE FELDSPARS IN Al-Si ORDERING

笔者用X射线粉末衍射技术，对六个天然钾长石中的铝在T1o四面体位置的占位率进行了测定，它们的T1o值从0．28变化到0．79。对它们的透射电子显微镜研究表明，两个T1o为0．28和0．31的高透长石有对电子束异常过敏的调制结构，无法记录到它们的衍衬像。在另外三个样品中，都见到了芦席状结构，并夹杂着具一定宽度的片晶组成的格子双晶。片晶宽度随T1o的变大而增加。而在产于一个霞石正长岩中的正长石中没有观察到任何微结构。六个样品的29SiMASNMR谱随T1o值由小变大的变化规律是：随T1o值增大，29Si谱由两个峰变为宽阔重叠的三个峰，再变为分裂明显的三个峰。

Al occupancy in T1o site for six natural alkaline feldspars was determined by means of Xray powder diffraction. Their T1o values range from 0. 28 to 0. 79. Two high sanidines with the T1o values of 0. 28 and 0. 31 respectively show modulation structure, but it cannot be recorded because it is very much sensitive to electron beam. For three of the alkaline feldspar samples the tweed texture mixing with M twin can be seen by the TEM method. The width of the twin lamellae increases with increasing T1o value. No microstructure can be seen with the TEM method for one of the samples occurring in nepheline syenite. The 29Si MAS NMR spectra of all the samples change regularly. That is to say, the spectra with two peaks tend to evolve into three narrow peaks with increasing T1o value.