Special Issue "Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications"

A special issue of Minerals (ISSN 2075-163X).

Deadline for manuscript submissions: closed (30 June 2018).

Special Issue Editor

Prof. Dr. Manuel Pozo Rodríguez
Website1 Website2 SciProfiles
Guest Editor
Department of Geology and Geochemistry, Universidad Autónoma of Madrid, 28049 Madrid, Spain
Interests: geology and geochemistry of clays; special clays applications; sepiolite–palygorskite; bentonite; Talc–kerolite; clays and health; mineral characterization
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Special Issue Information

Dear Colleagues,

Clay minerals are fine-grained materials with interesting physical-chemical properties that are highly dependent of their structure and composition. Both layer charge and small particle size of clay minerals result in suitable properties such as plasticity, sorption, rheology and ion exchange, among many others. Moreover, these properties can change in clays showing similar clay mineral assemblages but different origin. From a genetic point of view, clay minerals are authigenic or detrital (inherited). Authigenic clay minerals are “formed or generated in place” in the broader sense, whether related to soil processes, sedimentary deposition or diagenesis, but also formed under low grade metamorphic conditions and/or the influence of hydrothermal events. Authigenic clay minerals form in or react at the depositional environment so that they are indicators of specific aspects of the chemistry of that environment. In addition, some authigenic clay minerals are included in the so-named “special clays” forming bentonite, kerolite-Mg smectite, sepiolite and palygorskite deposits, which are economically relevant because of their wide industrial applications.

This Special Issue aims to publish papers providing recent advances on mineralogy and geochemistry of the authigenic clay minerals, their genetic pathways and applications.

Prof. Dr. Manuel Pozo Rodríguez
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Authigenic clay minerals
  • Bentonite
  • Sepiolite
  • Palygorskite
  • Kerolite/Mg-smectite mixed layers
  • Geochemistry
  • Genesis
  • Applications

Published Papers (7 papers)

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Research

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Open AccessArticle
Authigenic Mg-Clay Minerals Formation in Lake Margin Deposits (the Cerro de los Batallones, Madrid Basin, Spain)
Minerals 2018, 8(10), 418; https://doi.org/10.3390/min8100418 - 20 Sep 2018
Cited by 2
Abstract
The Madrid Basin contains large and well developed deposits of Mg-clays of Miocene age. These were developed in an environment controlled by a lacustrine saline-alkaline environment with an arid or semi-arid climate, leading to large deposits of Mg-clays. This paper summarizes the study [...] Read more.
The Madrid Basin contains large and well developed deposits of Mg-clays of Miocene age. These were developed in an environment controlled by a lacustrine saline-alkaline environment with an arid or semi-arid climate, leading to large deposits of Mg-clays. This paper summarizes the study about the formation of Mg-clay minerals in the transition from mudflat lithofacies made-up of Mg-smectite to palustrine lithofacies where sepiolite is predominant. The samples collected in the field were characterized by XRD (X-Ray Diffaction) (bulk sample and clay fraction), examined using SEM (Scanning Electron Microscopy) and analyzed by XRF (X-Ray Fluorescence) and FTIR (Fourier Transform Infrared Spectroscopy). The results suggest that during the formation of these materials dissolution-precipitation, direct precipitation and recrystallization mechanisms intervened. The type of water present (runoff, lake and/or groundwater) is a key factor for the development of the different mineral phases. In the case of the study, the analyzed series goes from mudflat conditions with influence of runoff water to a palustrine environment. During this evolution, the influence of groundwater increases with time. This is reflected in the affinity between the samples analyzed and the presence of certain elements that could serve as indicators of changes between different media. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Open AccessArticle
Microwave-Assisted Acid Activation of Clays Composed of 2:1 Clay Minerals: A Comparative Study
Minerals 2018, 8(9), 376; https://doi.org/10.3390/min8090376 - 30 Aug 2018
Cited by 2
Abstract
The effect of the microwave-assisted acid treatment (MAT) on the structure and texture of dioctahedral (montmorillonite) and trioctahedral (saponite) smectites, kerolitic clays and sepiolites were studied by scanning electron microscopy, nitrogen adsorption, X-ray fluorescence, X-ray diffraction and Fourier transform infrared spectroscopy. This study [...] Read more.
The effect of the microwave-assisted acid treatment (MAT) on the structure and texture of dioctahedral (montmorillonite) and trioctahedral (saponite) smectites, kerolitic clays and sepiolites were studied by scanning electron microscopy, nitrogen adsorption, X-ray fluorescence, X-ray diffraction and Fourier transform infrared spectroscopy. This study shows that in the smectite group of minerals the effectiveness of MAT is notably influenced by the chemical composition of the octahedral sheet, whereas in kerolitic clays it is influenced by the proportion of the expandable phase in the mixed layer sequence. On the other hand, the reactivity of sepiolites depends on the width of the natural fibres. With these treatments, extremely high specific surface area (SSA) increments are achieved in just 16 min. The SSA increments reach values up to 231 m2/g (%ΔSBET = 80) in sepiolites, 198 m2/g (%ΔSBET = 155) in Mg-smectites, and 161 m2/g (%ΔSBET = 61) in kerolitic clays. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Open AccessArticle
Authigenic Clay Minerals from Interface Reactions of Concrete-Clay Engineered Barriers: A New Perspective on Mg-Clays Formation in Alkaline Environments
Minerals 2018, 8(9), 362; https://doi.org/10.3390/min8090362 - 21 Aug 2018
Cited by 6
Abstract
Artificial and singular geochemical environments are created around the engineered barrier systems (EBS) designed to isolate high level nuclear wastes in deep geological repositories. A concrete-bentonite interface takes place within the EBS and it builds a significant chemical gradient (pH), approximately from pH [...] Read more.
Artificial and singular geochemical environments are created around the engineered barrier systems (EBS) designed to isolate high level nuclear wastes in deep geological repositories. A concrete-bentonite interface takes place within the EBS and it builds a significant chemical gradient (pH), approximately from pH 8 (bentonite) to pH 12 (low alkali concrete), in a few millimetre thickness. This disequilibrium triggers dissolution and precipitation reactions and form a thin altered region. In this area, poorly ordered authigenic clay minerals, mainly hydrated magnesium silicates, are formed adjacent to hydrated calcium silicates and calcite precipitates adhered to the interface with concrete. This paper presents the development of this authigenic mineral layer comparing 6–18 months to 13 years interfaces. Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) morphological and chemical characterization with the aid of ternary plots, X-ray diffraction (XRD) and infrared (IR) data show the young to old interface evolution from single brucite layers to stevensite-saponite silicates composition. Geochemical calculations indicate that this layer acts as a pH~11 buffer useful to minimize bentonite alteration and to favour the retention of amphoteric metal ions. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Open AccessArticle
Influence of the Structure and Experimental Surfaces Modifications of 2:1 Clay Minerals on the Adsorption Properties of Methylene Blue
Minerals 2018, 8(8), 359; https://doi.org/10.3390/min8080359 - 19 Aug 2018
Cited by 2
Abstract
In this work the adsorption capacities of methylene blue on Mg-smectite and sepiolite and its derived material obtained after acid treatment and/or the addition of Fe at its surfaces are studied. Natural smectite with high Mg-content in its octahedral sheet (Mg-smectite) displays higher [...] Read more.
In this work the adsorption capacities of methylene blue on Mg-smectite and sepiolite and its derived material obtained after acid treatment and/or the addition of Fe at its surfaces are studied. Natural smectite with high Mg-content in its octahedral sheet (Mg-smectite) displays higher adsorption capacity than the sepiolite due to the ability of Mg-smectite to expand the basal spacing to accommodate methylene blue cations between adjacent layers and the inability of sepiolite to adsorb these cations within the structural channels. The acid-activation of Mg-smectite causes a clear decrease in the adsorption capacity attributed to the partial loss of the interlayer positions by the loss of the octahedral sheet and subsequent formation of amorphous silica. Moreover, the adsorption of the Mg-smectite decreases even more when iron oxohydroxides species are incorporated in its interlayer spacing making inaccessible the interlayer active sites for the adsorption of methylene blue cations. On the contrary, the microwave-assisted acid treatment of sepiolite causes a slight increase in the adsorption capacity related with the dispersion of fibers. Nevertheless, contrary to that observed with Mg-smectite, higher increasing of adsorption capacities are obtained after the formation of new adsorption centers due to the incorporation of iron oxohydroxides species at the external surfaces of sepiolite. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Open AccessArticle
The Nature of Laponite: Pure Hectorite or a Mixture of Different Trioctahedral Phases?
Minerals 2018, 8(8), 314; https://doi.org/10.3390/min8080314 - 26 Jul 2018
Cited by 7
Abstract
A series of laponites and synthetic OH- and fluorinated hectorites prepared from hydrothermal and melting experiments at both industrial and laboratory scale were examined with XRD and FTIR (MIR and NIR) to determine their mineralogical composition and possible compositional heterogeneity. The end materials [...] Read more.
A series of laponites and synthetic OH- and fluorinated hectorites prepared from hydrothermal and melting experiments at both industrial and laboratory scale were examined with XRD and FTIR (MIR and NIR) to determine their mineralogical composition and possible compositional heterogeneity. The end materials contained both Li- and Na-bearing phases. The industrial hydrothermal OH-smectites prepared at low temperatures consist of random mixed layer hectorite-stevensite-kerolite with about 40–50% hectorite layers, the remaining being stevensite and kerolite at roughly equal proportions. The FTIR spectra of these smectites contain, besides the main Mg3OH stretching/overtone bands at 3695–3690 and 7225–7214 cm−1, respectively, additional OH overtone bands at ~3716 and 7265 cm−1 (hydrated state). These bands might be linked to Mg2LiOH stretching modes. The melt-derived smectites are kerolite-free but still contain stevensite layers, although the preparation methods involved heating in the excess of 1000 °C. In these smectites Li might be partitioned to both octahedral and interlayer sites. Subsequent annealing of the melt-derived Mg-Li smectites caused migration of the exchangeable Li to the vacant octahedral due to the Hofmann-Klemen effect and thus decrease of the layer charge, as was indicated by the νO-D method. Hydrothermal synthesis of Mg-Li smectites at high temperature (400 °C) and pressure (1 kbar), yielded pure hectorite without stevensite or kerolite domains. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Open AccessArticle
Geochemistry and Biomarker Analysis of the Bentonites from Esquivias (Toledo, Spain)
Minerals 2018, 8(7), 291; https://doi.org/10.3390/min8070291 - 09 Jul 2018
Cited by 1
Abstract
The Tajo Basin is one of the richest in Mg-clays known around the world. Mg-bentonites, kwon as pink clays and green clays, alter in the Intermediate Unit of the Miocene sediments. In this work, a new approach to the genesis of these bentonites [...] Read more.
The Tajo Basin is one of the richest in Mg-clays known around the world. Mg-bentonites, kwon as pink clays and green clays, alter in the Intermediate Unit of the Miocene sediments. In this work, a new approach to the genesis of these bentonites is performed by studying for the first time the biomarkers present in these clays in relation to the mineralogy and geochemistry, as well as using discriminatory criteria between green and pink clays. Samples were collected at a quarry of Mg-bentonites, in the proximities of Esquivias (Toledo, Spain). Mineralogical characterization and semi-quantification (X-ray diffraction (XRD)) allowed a well-defined classification according to the mineralogical content of the samples to be established, differentiating four associations. Geochemical analyses are clearly linked to the mineralogy and provide criteria to differentiate the genesis of the materials studied. In this regard, green clays are interpreted as having a more detrital character than pink clays, which present a more authigenic character. Biomarkers (n-alkanes and n-alkanoic acids) were studied, not showing a clear link with the mineralogy as in the case of the geochemistry, but providing interesting information about the origin and degradation of the organic matter. Pink clays have higher contents in biomarkers than green clays, providing a discriminative criterion. Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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Review

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Open AccessReview
An Overview of Authigenic Magnesian Clays
Minerals 2018, 8(11), 520; https://doi.org/10.3390/min8110520 - 09 Nov 2018
Cited by 13
Abstract
Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is [...] Read more.
Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is not inherited. Transformation of precursor detrital minerals, a process also termed “neoformation by addition”, can be conducted whether throughout precipitation on pre-existing natural surfaces or transformation and reaction on pre-existing surfaces. Both processes have been recognized as effective mechanisms in the formation of Mg-clays, which mostly include 2:1 clay minerals, such as talc-kerolite and Mg-smectites, as well as fibrous clays (sepiolite, palygorskite). Authigenic Mg-clay minerals occur in both modern and ancient marine and non-marine depositional environments, although formation of these clays in hydrothermal continental and seafloor settings must be also outlined. Most favourable conditions for the formation of Mg-clays on earth surface are found in evaporitic depositional environments, especially where parent rocks are enriched in ferromagnesian minerals. In these settings, Mg-clays are important constituent of weathering profiles and soils and can form thick deposits of significant economic interest. Based on this review of authigenic clay deposits, we propose three geochemical pathways, mainly related to continental environments, for the origin of authigenic Mg-clays: formation of Al-bearing Mg-clays (pathway 1), formation of Al-free Mg clays (pathway 2) and formation of sepiolite from other Mg-clay minerals (pathway 3). Full article
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
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