Extended Data Fig. 5: Comparison between XRD patterns of minerals affected for rotational disorder and the resulting in MB from the Le Bail method.

(a), Top and bottom, XRD patterns (red) of rotationally disordered non-ferric illites showing the broadening effect of n·120° rotations over the set of reflections verifying the condition k = 3n. The upper pattern corresponds to a cis-vacant structure (cv-1Md), as is marked by the diagnostic (111) peak. The bottom pattern corresponds to a trans-vacant disposition (tv-1Md), marked by the absence of (111) peak. In both cases, low iron content is reflected by the diagnostic presence of (002). The blue curve shows the intensity’s profile of MB resulting from the Le Bail method. Here, the absence of (002) corresponds to a clay mineral with high-iron content. The ratio (111) < (−112) is indicative of a tv/cv interstratification, a typical feature of interstratified G-S. The extensive broadening of the set of k = 3n reflections, not affecting the (001) peak is indicative of n·120° rotational disorder. All these features are diagnostic of a mixed layer G-S evolution. (b), Broadening of k = 3n reflections due to random stratification of layers or when rotational disorder of n 60° kind dominates. Upper curve (Blue) correspond to data from MB and the bottom curve (red) correspond to a 4.5 wt. % K₂O glauconite, without rotational disorder. The intensities are in arbitrary units.