Special Issue "Smectite Illitization"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Clays and Engineered Mineral Materials".

Deadline for manuscript submissions: closed (15 June 2021).

Special Issue Editor

Dr. Javier Arostegi García
E-Mail Website
Guest Editor
Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/EHU, Apdo. 644, 48080 Bilbao, Spain
Interests: clay minerals; X-ray diffraction; electron microscopy; diagenesis; paleoenvironments; paleoclimate

Special Issue Information

Dear Colleagues,

Smectite illitization has been a widely researched process in different geological contexts: burial diagenesis, low-grade and contact metamorphism, hydrothermal and pedogenic alteration, etc. This process has been used as a prograde and retrograde marker in siliciclastic rocks and as a paleoenvironment and paleoclimatic proxy in various geological contexts. It has also been useful in soil fertility management research, in hydrocarbon exploration or in research on the long-term performance of bentonite barriers in radioactive waste deposits.

The illitization reaction produces, in general terms, an increase in the TOT layer charge and the subsequent K fixation in the interlayer space. Therefore, structural adjustments are needed which affect not only the magnitude of the charge of the 2:1 expandable layers, but also their localization in the octahedral or tetrahedral layers. The process comprises a series of chemical reactions and structural changes that give rise to coherent domains intermediate between smectite and illite. These are the so-called I/S mixed-layer minerals, which consist of different stacking sequences of the 2:1 layers of illite and smectite.

This process leads to a greater structural order and compositional homogeneity of the phases involved, such as the reaction progresses. The nature, structure, composition, and textural relationships of the different phases involved in the process can be revealed using XRD and TEM techniques in various forms, among others.

The mechanism advocated to explain smectite illitization more frequently, are solid state transformation, dissolution–recrystalization, and grain coarsening by Ostwald’s step rule.

Although contributions from several of these is possible in different environments, solid state transformation seems to predominate in close-systems, while dissolution–recrystallization and grain coarsening seem more efficient in fluid-dominated open systems. Microbially-promoted smectite illitization represents a relevant mechanism and should be considered in more detail.

We encourage you to submit original papers on identification, description, modeling, applications, and any other subject related to smectite illitization.

Dr. Javier Arostegi García
Guest Editor

Manuscript Submission Information

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  • Clay minerals
  • Mixed layers
  • Geological environments
  • Reaction mechanisms
  • Proxy
  • Applications

Published Papers (1 paper)

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Mixed-Layer Illite-Smectite in Pennsylvanian-Aged Paleosols: Assessing Sources of Illitization in the Illinois Basin
Minerals 2021, 11(2), 108; https://doi.org/10.3390/min11020108 - 22 Jan 2021
Cited by 1 | Viewed by 547
Mixed-layer illite-smectite (I-S) from a new set of Pennsylvanian-aged Illinois Basin underclays, identified as paleosols, are investigated to assess the impact of (1) regional diagenesis across the basin and (2) the extent to which ancient environments promoted illitization during episodes of soil formation. [...] Read more.
Mixed-layer illite-smectite (I-S) from a new set of Pennsylvanian-aged Illinois Basin underclays, identified as paleosols, are investigated to assess the impact of (1) regional diagenesis across the basin and (2) the extent to which ancient environments promoted illitization during episodes of soil formation. Interpretations from Reichweite Ordering and Δ° 2θ metrics applied to X-ray diffraction patterns suggest that most I-S in Illinois Basin paleosols are likely the product of burial diagenetic processes and not ancient soil formation processes. Acid leaching from abundant coal units and hydrothermal brines are likely diagenetic mechanisms that may have impacted I-S in Pennsylvanian paleosols. These findings also suggest that shallowly buried basins (<3 km) such as the Illinois Basin may still promote clay mineral alteration through illitization pathways if maximum burial occurred in the deep past and remained within the diagenetic window for extended periods of time. More importantly, since many pedogenic clay minerals may have been geochemically reset during illitization, sources of diagenetic alteration in the Illinois Basin should be better understood if Pennsylvanian paleosol minerals are to be utilized for paleoclimate reconstructions. Full article
(This article belongs to the Special Issue Smectite Illitization)
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