EPR parameter of order degree in natural kaolinite and its relation to weathering

Abstract

In studying the degree of order (or disorder) in kaolinite, X-ray diffraction and DTA are commonly used, but spectroscopic method (as EPR, IR)has become a useful and additional tool now. The total iron content and the intensity of Fe3+(I) line are not always correlated negatively with order degree in natural kaolinite. But in the present case, they show direct correlations. So it appears that they cannot be used as an ideal parameter for measuring the order degree in kaolinite. The ratio of Fe3+(E)line and Fe3+(I)line intensities obtained directly from EPR spectrum of Fe3+at geff=4 appears to be a better EPR parameter for measuring the magnitude of order degree in kaolinite and for determining the intensity of some geological processes (such as weathering, hydrothermal alteration and so on) with aid of kaolinite. However, EPR data can only be used to qualitatively estimate the degree of order in kaolinite and related geological process for the present. There is still much work to be done in order to make EPR a method of quantitative estimation in the field.