The Kubler Index (KI) is defined as the full width at half-maximum
height (FWHM) of the 10-Angstrom X-ray diffraction peak of
illite-smectite interstratified (I-S) clay minerals, The only parameters
controlling the Kubler index are assumed to be the mean number of layers
(N) in the coherent scattering domains (CSD). the variance of the
distribution of the number of layers of the CSB, the mean percentage of
smectite layers in I-S (%S), and the probability of layer stocking
(Reichweite).
The Kubler-Index measurements on ah-dried (KIAD) and ethylene-glycolated
(KIEG) samples were compared to N and %S using the NEWMOD computer
program to simulate X-ray diffraction patterns. Charts of KIAD versus
KIEG corrected for instrumental broadening were made and isolines were
mapped for constant N and CLS. Isolines allow a direct and rapid
determination of N and RS from KI measurements.
The method allows quantification of the metamorphic anchizone limits by
considering mean thickness of fundamental particles in MacEwan
crystallites. The transition from diagenesis to the anchizone and from
the anchizone to the epizone of low-grade metamorphism corresponds to
thicknesses of 20- and 70-layer fundamental particles, respectively.