SI-29 AND AL-27 MAS NMR-STUDY OF ALKALI FELDSPARS

IH natural alkali feldspars have;been studied by Si-29 and Al-27 MAS N MR as well as XRD, IR, EPMA and chemical analysis. Three kinds of Si-2 9 NMR spectra, i.e. the spectra of microcline, perthite and perthite w ith minor plagioclase, have been obtained. There are two types of Al-2 7 NMR spectra. The Al-27 spectrum. of microcline is the same as-that o f perthite, but is different from the spectrum for perthite containing plagioclase. Through this study, we found that the results of NMR and IR are inconsistent with that of XRD, which shows that the transition of alkali feldspar from monoclinic to triclinic system might be a rat her complicated process.