Fig. 5
From: Diagenesis and very low grade metamorphism in a 7,012 m-deep well Hongcan 1, eastern Tibetan plateau
Measurement of illite polytype parameter P = 2M 1(I 025)/[1M(I 112) + 2M 1(I 025)]. There is a major difference between 1M and 2M 1 structures of illite, that is, d 112 (3.66 Å) of 1M illite and d 025 (2.988Å) of 2M 1 illite (according to ICDD 2005). Because d 114 of 2M 1 structure is often interfered by feldspar’s major reflections specially by the main reflection (3.19 Å) of albite and d −113 is too weak, the amount of 2M 1 in the mixture of 1M + 2M 1 is measured and calculated using the integrated intensities of reflection (112) of 1M and (025) of 2M 1 illite for the sake of simplification. When other reflection appears the deconvolution technique was used and this way the pure reflections of 025 and 112 can be obtained