Sequential structure transformation of illite-smectite-vermiculite during diagenesis of Upper Jurassic shales from the North Sea and Denmark

Abstract

For mixed-layer clay fractions from the North Sea and Denmark, X-ray diffractograms have been recorded for specimens saturated with Mg, Ca, Na and NH4, both airdry and intercalated with ethylene glycol, and the patterns have been computer-simulated with a multicomponent program. The mixed-layer fractions consist of an illite-smectite-vermiculite (I-S-V) phase constituting -90% of the fraction and a kaolinite-illite-vermiculite (K-I-V) phase. For each I-S-V, the degree of swelling in swelling interlayers depends on both interlayer cation and glycolation, whereas the amount of non-swelling illite and swelling interlayers and the interstratification parameters are constant. Based on structural characteristics and the degree of diagenetic transformation, the samples investigated can be divided into three groups. The I-S-V of group one is predominantly detrital and has 0.69-0.73 illite, 0.26-0.20 smectite and 0.04-0.07 vermiculite interlayers, the illite, smectite and vermiculite interlayers being segregated. The I-S-V of group two has been diagenetically transformed and has 0.80 illite, 0.12 smectite and 0.08 vermiculite interlayers, the vermiculite interlayers being segregated whereas the illite and smectite have the maximum ordering possible for R = 1. The I-S-V of group three has been further transformed during diagenesis and has 0.84 illite, 0.08 smectite and 0.08 vermiculite interlayers. Statistical calculations demonstrate that the I-S-V transformation can be described as a single interlayer transformation (SIT) within the crystallites.

Hydration Properties and Interlayer Organization of Water and Ions in Synthetic Na-Smectite with Tetrahedral Layer Charge. Part 1. Results from X-ray Diffraction Profile Modeling

“…28 Additional variable parameters include the layer-to-layer distance, which is hereafter referred to as layer thickness, and the coherent scattering domain size (CSDS) along the c* axis, which was characterized by a maximum CSDS value, set to 50 layers, and by a variable mean value (N). 56 The layer thickness was allowed to deviate from its mean value by introducing a variance parameter σ z to account for this "disorder of the second type". 20,57,58 The z-coordinates of all atoms building up the 2:1 layer were set as determined for vermiculite minerals.…”

Cs–sorption in weathered biotite from Fukushima granitic soil

“…This program enables the comparison between the experimental and calculated XRD patterns with proposed models (e.g., Drits et al, 1997;Sakharov et al, 1999;Hubert et al, 2009 2 , respectively. For the Z-coordinates of the atomic sites in the biotite and Ca-vermiculite layers, the atomic parameters from X-ray structure analyses by Brigatti et al (1991) and Slade et al (1985) were used, respectively.…”

Influence of pH on the interlayer cationic composition and hydration state of Ca-montmorillonite: Analytical chemistry, chemical modelling and XRD profile modelling study

“…The algorithms developed initially by Sakharov and Drits (1973), Drits and Sakharov 153 (1976) and more recently by Drits et al (1997a) and Sakharov et al (1999) were used to fit 154 experimental XRD profiles over the 2-50° 2θ CuKα range using a trial-and-error approach. 155…”