Illite-Smectite Mixed-Layer Minerals in the Hydrothermal Alteration of Volcanic Rocks: I. One-Dimensional XRD Structure Analysis and Characterization of Component Layers

Abstract

For a series of mixed-layer illite-smectite (I-S) minerals from a drillhole near the Kakkonda geothermal field, one-dimensional structure analysis by X-ray diffraction (XRD) was performed using Casaturated specimens in both air-dried and ethylene glycol-solvated states. The expandability characteristics of component layers were also examined by means of alkylammonium exchange and Li saturation. The K content in the illite layers was 1.5–1.7/O20(OH)4 in the I-S series from 3 to 85% of I-layer content (% I). The layer charge of the smectite layer varied slightly within the range of 0.3–0.5/O10(OH)2 by alkylammonium exchange experiments and the expandability was independent of the beidellite content within a range of 0–0.5 by the Li-saturation test. The degree of long-range ordering represented by Reichweite (R) parameters varied from R0 to R3 via R1 and R2 with increase in % I. The I-S samples contained <10% vermiculite as the third component and the vermiculite content tended to decrease with progressive illitization.In contrast to the smectitic R0 samples (<10% I), more illitic R0 (e.g. 35% I) and >R1 I-S samples showed complicated expandability with alkylammonium exchange. The XRD patterns of dodecylammonium-exchanged I-S samples can be interpreted by random interstratification of several types of sub-units such as layer-doublets, layer-triplets and layer-quartets present in the crystallites. This interpretation is consistent with the variation in the occurrence probabilities of layer-multiplets calculated from the junction probabilities and the proportions of layers. Because the interpretation indicates that I-S is a stack of various types of the sub-units, the smectite illitization can be described by a systematic change in the type and proportion of the sub-units constituting crystallites.

Characterization of smectite to NH4-illite conversion series in the fossil hydrothermal system of Harghita Bai, East Carpathians, Romania

“…14). This is similar to other I-S samples described in hydrothermal environments (Ylagan et al 2000), where direct illite precipitation from high-temperature solutions was inferred (Eberl et al 1987;Inoue and Utada 1983;Inoue et al 2005;Ylagan et al 2000). The formation mechanism of the NH 4 -I series (Fig.…”

Unraveling complex <2 m clay mineralogy from soils using X-ray diffraction profile modeling on particle-size sub-fractions: Implications for soil pedogenesis and reactivity

“…A solid arrow indicates a significant misfit between the experimental and calculated patterns as compared to the optimum fit reported in Figure 2. Other notations and labels are as in Figure 2. samples collected at different depths and temperatures (Drits et al 1997a(Drits et al , 2002a(Drits et al , 2002bSakharov et al 1999aSakharov et al , 1999bSakharov et al , 2004Lindgreen et al 2000Lindgreen et al , 2002Claret et al 2004;McCarty et al 2004McCarty et al , 2008McCarty et al , 2009Inoue et al 2005;Aplin et al 2006;Lanson et al 2009;Ferrage et al 2011b). Similarly, the behavior of smectitic layers can be assessed as a function of relative humidity (Cases et al 1992(Cases et al , 1997Bérend et al 1995;Ferrage et al 2005aFerrage et al , 2007cFerrage et al , 2010, temperature (Ferrage et al 2007a(Ferrage et al , 2007b, or chemical medium (Claret et al 2002;Ferrage et al 2005cFerrage et al , 2005d.…”

“…Over the last decade, this approach has proved to be successful in the characterization of complex clay parageneses as well as in the understanding of the transformation mechanisms involved in diagenetic and hydrothermal series (Drits et al 1997a(Drits et al , 2002a(Drits et al , 2002bSakharov et al 1999aSakharov et al , 1999bSakharov et al , 2004Lindgreen et al 2000Lindgreen et al , 2002Claret et al 2004;McCarty et al 2004McCarty et al , 2008McCarty et al , 2009Inoue et al 2005;Aplin et al 2006;Lanson et al 2009). Because several structural models may fit a given experimental pattern equally well, the best solution is given by the multispecimen method (Sakharov et al 1999a).…”

X-ray Identification of Mixed-Layer Structures: Modelling of Diffraction Effects

“…In addition, the profiles of the diffraction lines, which are strongly affected by interstratification effects, are not taken into account by these peak-position methods. Consistently, all structural characterizations of natural samples performed with calculation algorithms allowing the calculation of their XRD patterns have led to the identification of mixed-layer structures that include more than two components owing to the systematic heterogeneity of the swelling/hydration behaviour of expandable layers (Drits et al, 1997b(Drits et al, , 2002aSakharov et al, 1999aSakharov et al, ,b, 2004aLindgreen et al, 2000Lindgreen et al, , 2002Lindgreen et al, , 2008Claret et al, 2004;McCarty et al, 2004McCarty et al, , 2008Inoue et al, 2005;Aplin et al, 2006;Hubert et al, 2009;Lanson et al, 2009). -Other limitations are linked to those of the programs used to calculate diffraction effects arising from mixed-layer structures, and the limited range used for variable parameters in order to (over)simplify the identification process.…”

“…In addition, Drits et al (1997cDrits et al ( , 1998 have derived a unique relation linking the a and b 2 parameters of the coherent scattering domain (CSD) size lognormal distribution reported for these clay minerals to the average thickness of the crystals (N): that is, a ¼ 0:9485lnN À 0:017 and b 2 ¼ 0:1032 lnN þ 0:034 A lognormal distribution of CSD sizes, with the above a and b 2 parameters, allowed a satisfactory fitting of the XRD data of various periodic and mixedlayer clay minerals (Drits et al, 1997b(Drits et al, , 2002aSakharov et al, 1999a, b;Lindgreen et al, 2000Lindgreen et al, , 2002Lindgreen et al, , 2008Claret et al, 2004;McCarty et al, Chapter 2.3 X-ray Identification of Mixed-Layer Structures 2004Ferrage et al, 2005bFerrage et al, , 2007Ferrage et al, , 2011bInoue et al, 2005;Lanson et al, 2009). With the lognormal distribution, the contribution of very thick crystals to the diffracted intensity becomes rapidly insignificant because of their negligible proportion, and the maximum number of layers in crystals (N max ) may be set to $ 5N for practical purposes.…”