Smectite Group Clay Minerals Research Articles

Enhanced Identification of Fracture Smectites and Other Alteration Minerals Via Short-Wave Infrared Reflectance at Two Finnish Crystalline Sites, Olkiluoto and Hyrkkölä

Fracture filling minerals and the smectite-group clay minerals in particular play a significant role in the geotechnical stability of the fractured rock mass. Smectites have multiple uses as geomaterials in waste management solutions, of which the most technically demanding is the geological disposal of radioactive waste. Here, the stability and occurrence of smectites as fracture filling minerals were studied with two main objectives: 1) to test the capability of short-wave infrared spectroscopy as a tool to streamline the site assessment where clay mineralogy needs to be characterised in detail, and 2) to provide a first assessment of naturally occurring smectites in various sample types collected from two Finnish sites (Olkiluoto and Hyrkkölä) and their potential as natural analogues of smectite stability for bentonite used in the engineered barrier systems of geological disposal repositories. The short-wave infrared (SWIR) method has been validated to be a useful tool in fracture mineral characterisation, specifically due to its fast acquisition and interpretation time compared to the conventional methods. The study confirms the in situ occurrence of smectites at both sites studied showing that, especially in Hyrkkölä, the smectite-group member is close to montmorillonite, the main constituent of bentonite. At Olkiluoto, the smectites studied show more interstratified features. The differences in the mode of occurrence are related to the history of their formation, especially hydrothermal alteration, and parent rock composition.

Determination of elemental concentrations of radionuclides in Turkish bentonite and calculation of radiogenic heat generation

ABSTRACT Bentonite containing smectite group clay minerals is an industrial raw material with a wide range of uses. In this study, the concentration of uranium, thorium, and radioactive potassium in ninety bentonite samples collected from quarries in Turkey was determined using an energy-dispersive X-ray fluorescence spectrometer. The concentrations of uranium, thorium and potassium varied from 0.4 to 18.2 with an average of 4.3 mg/kg, 5.4 to 53.4 with an average of 22.7 mg/kg and 0.3 to 3.4 with an average of 1.4 mg/kg, respectively. The radiogenic heat generation caused by the ionising radiation emitted from these radioactive elements in bentonite samples was calculated in the range of 0.9 to 6.6 µW/m3 with an average of 2.8 µW/m3.

Clays and the Origin of Life: The Experiments.

There are three groups of scientists dominating the search for the origin of life: the organic chemists (the Soup), the molecular biologists (RNA world), and the inorganic chemists (metabolism and transient-state metal ions), all of which have experimental adjuncts. It is time for Clays and the Origin of Life to have its experimental adjunct. The clay data coming from Mars and carbonaceous chondrites have necessitated a review of the role that clays played in the origin of life on Earth. The data from Mars have suggested that Fe-clays such as nontronite, ferrous saponites, and several other clays were formed on early Mars when it had sufficient water. This raised the question of the possible role that these clays may have played in the origin of life on Mars. This has put clays front and center in the studies on the origin of life not only on Mars but also here on Earth. One of the major questions is: What was the catalytic role of Fe-clays in the origin and development of metabolism here on Earth? First, there is the recent finding of a chiral amino acid (isovaline) that formed on the surface of a clay mineral on several carbonaceous chondrites. This points to the formation of amino acids on the surface of clay minerals on carbonaceous chondrites from simpler molecules, e.g., CO2, NH3, and HCN. Additionally, there is the catalytic role of small organic molecules, such as dicarboxylic acids and amino acids found on carbonaceous chondrites, in the formation of Fe-clays themselves. Amino acids and nucleotides adsorb on clay surfaces on Earth and subsequently polymerize. All of these observations and more must be subjected to strict experimental analysis. This review provides an overview of what has happened and is now happening in the experimental clay world related to the origin of life. The emphasis is on smectite-group clay minerals, such as montmorillonite and nontronite.

Trends and Composition—A Sedimentological-Chemical-Mineralogical Approach to Constrain the Origin of Quaternary Deposits and Landforms—From a Review to a Manual

In this study, six basic Quaternary landform series (LFS) and their sedimentary deposits (LFS1 aeolian, LFS 2.1 to 2.2 mass wasting, LFS 3 cryogenic-glacial, LFS 4.1 to 4.6 fluvial, LFS 5.1 to 5.2 coastal-marine, LFS 6.1 to 6.3 lacustrine) are subdivided into subtypes and examined with regard to their sedimentological parameters and their mineralogical and chemical compositions. Emphasis is placed on the textural (related to transport and deposition), compositional (sediment load/weight, Eh and pH) and geodynamic maturity of the sedimentary deposits which are influenced by the parent lithology and bedrock tectonic and by the climate during the last 2 Ma. To constrain the development of the LFS and their sediments, composite trend-line diagrams are designed combining sedimentological (x-axis) and chemical/mineralogical dataset (y-axis): (1) sorting vs. heavy mineral content; (2) sphericity of grains vs. silica/carbonate contents; and (3) median vs. Ti/Fe ratios. In addition, the x-y plots showing the log SiO2/Al2O3 vs. log Na2O/K2O are amended by a dataset of the three most common clay minerals, i.e., kaolinite-, mica-, and smectite-group clay minerals. Such joint sedimentological-chemical-mineralogical investigations focused on the depositional environment of unconsolidated clastic sediments of Quaternary age can be used to describe the economic geology and environmental geology of mineral deposits in the pre-Quaternary sedimentary series according to the phrase: “The Present is the key to the Past”. Both trend diagrams and compositional x-y plots can contribute to constraining the development of the full transect of landform series from the fluvial incision and slope retreat to reef islands fringing the coastal zone towards the open sea as far as they are built up of clastic sedimentary deposits enriched in siliceous and/or carbonate minerals. Climate zonation and crustal maturity are the exogenous and endogenous “drivers”, as can be deduced from the compositional (mineralogy and chemistry) and physical (transport and deposition) variations observed in the Quaternary sediments. The current study bridges the gap between a review only based on literature and a hybrid manual generated by practical field studies devoted to applied geosciences in economic and environmental geology (“E & E issue”).

Discontinuity Nomenclature and Its Significance in Geotechnics

The trinity of the water-discontinuity-clay is the main cause behind most geotechnical problems involving rock slopes. The water molecule is unique to have a dipole property and is a common reactant in numerous chemical reactions. Discontinuity controls the slope stability. The planarity, continuity, and clay mineral infill are particularly important in the areas where outslope bedding dominates. The shear strength of clay mineral approaches zero upon saturation. The discontinuity nomenclature reduces the volume of the geomodel (GM) works, which comprise geology, hydrogeology, engineering geology, geoenvironment, and the geotechnics over 80%. The smectite-group clay minerals have a unit cell with net negative charge. Hence the water is readily captured by the electrically unbalanced mineral causing it to swell by more than 10% of its dry volume and then its shear strength approaches zero. The outsloping bedding, layering, or the basically imbricated thrust faults in places are the common examples of large-scale landslides. The discontinuity survey with the proposed nomenclature and approach is especially important in locating and orienting linear engineering structures. Consequently, this approach enhances the researchers and designers considerably in conducting projects conveniently in terms of timing, environment, safety/security and the cost.

Lithofacies analysis and economic mineral potential of a braided fluvial succession of NW Himalayan foreland basin Pakistan

This study has described detailed lithofacies analysis, clay mineralogy, and depositional setting, and highlighted economic mineral potential of late Miocene to Early Pliocene mid Siwalik Dhok Pathan Formation. The Siwalik fluvial sedimentary succession is 5300 m thick in the NW Himalayan foreland fold-and-thrust belt known as Surghar-Shingar Range (SSR). The middle Siwalik (Dhok Pathan Formation) typically represents cyclic alternation of massive sandstones, siltstones, mudstones, and claystones in repeated fining upward rhythm with varied thicknesses from 807 to 1540 m. Detailed sedimentological investigations resulted in the identification of seven distinct lithofacies (Gt, St, Sh, Ss, Sl, Fm, and Fl) which had been deposited by sand-dominated bed load braided fluvial system. The facies Sh is hosting detrital uraninite identified through a scanning electron microscope (SEM). X-Ray diffraction analyses revealed that kaolinite, smectite (montmorillonite and saponite), illite, vermiculite, and chlorite (clinochlore and chamosite) are the main clay mineral suits present in the formation. The morphology of clay mineral suits is indicative of weathering products or contribution from the source areas. The absence of glass shards and mineral analcimolite evidenced that these smectite group clay minerals were not derived from the devitrification of volcanic ashes. The sedimentological analysis, mineralogical composition, and paleo-flow directions revealed that these sediments had been deposited by NS fluvial system presently known as Indus River system in this area. The rare earth element concentrations of sandstone and heavy minerals laminations (black sand) show enrichment of uranium (662 ppm), thorium (1374 ppm), La (975 ppm), Ce (2831 ppm), Pr (193 ppm), Nd (746 ppm), Gd (98 ppm), and Dy (50.8 ppm), which specify good indicative economic mineral potential of the formation.

Influência da rota alcoólica e razão tensoativo/argila no processo de organofilização de argilas bentoníticas e em suas propriedades reológicas em meios não aquosos

<p>Argilas bentoníticas podem ser definidas como sendo uma argila constituída essencialmente de argilominerais do grupo das esmectitas, especialmente a montmorilonita. Não sendo as argilas bentoníticas naturalmente organofílicas, estas podem ser modificadas através de tratamentos específicos com tensoativos (iônicos ou não-iônicos), passando sua natureza de hidrofílica para hidrofóbica. As argilas organofilicas são amplamente utilizadas como agentes viscosificantes na mistura de componentes usados para a perfuração de poços de petróleo e água entre outros usos. Estudos recentes demonstraram a influência do tipo de argila, tensoativo e presença de defloculante na reologia das dispersões. Neste trabalho verificamos a influência da rota alcoólica, do teor de argila e tensoativo na produção de argilas organofilicas e no comportamento reológico final em meios não aquosos. Para tanto, realizamos a caracterização das amostras de argilas através de análise termogravimétrica, difração de raios X, análise térmica diferencial e análise granulométrica. As argilas organofílicas foram caracterizadas por difração de raios X e fluorescência de raios X. Por fim foram produzidas dispersões de acordo com normatização da Petrobras para realização dos ensaios reológicos. Os resultados evidenciaram que existe influência da razão argila/tensoativo e da rota alcoólica nas propriedades reológicas das dispersões.</p>

Engineering properties of expansive clayey soil stabilized with lime and perlite

There are around 6700 millions tons of perlite reserves in the world. Although perlite possesses pozzolanic properties, it has not been so far used in soil stabilization. In this study, stabilization with perlite and lime of an expansive clayey soil containing smectite group clay minerals such as montmorillonite and nontronite was investigated experimentally. For this purpose, test mixtures were prepared with 8% of lime (optimum lime ratio of the soil) and without lime by adding 0%, 10%, 20%, 30%, 40% and 50% of perlite. Geotechnical properties such as compaction, Atterberg limits, swelling, unconfined compressive strength of the mixtures and changes of these properties depending on perlite ratio and time were determined. The test results show that stabilization of the soil with combination of perlite and lime improves the geotechnical properties better than those of perlite or lime alone. This experimental study unveils that the mixture containing 30% perlite and 8% lime is the optimum solution in stabilization of the soil with respect to strength.

Assessments of swelling anisotropy of Ankara clay

Determination of swelling pressure exerted by expansive soils is important for designing structures such as shallow foundations, shallow tunnels, retaining walls, canal linings and underground conduits in such soils. The axial deformation and swelling pressure under zero lateral deformation can be determined by conventional oedometer using two identical samples. However, this test doesn't permit a synchronized measurement of both the axial and lateral swelling pressures on the same sample. The Ankara clay, which is an overconsolidated clay, rich in smectite group clay minerals, and partly covers the southern part of Ankara, the capital of Turkey, causes damage to light structures located at the surface and at shallow depths. A comprehensive study was conducted (i) to determine the swelling parameters (swelling pressure and swelling percentage) of Ankara clay both in vertical and lateral directions using a thin wall oedometer ring (providing synchronized measurement of swelling parameters in both directions), (ii) to compare lateral and vertical swelling parameters of the clay for the assessment of swelling anisotropy, and (iii) to investigate the effect of microstructure of Ankara clay on its swelling behavior using Scanning Electron Microscope (SEM). The experimental results revealed that the swelling parameters measured in vertical direction were greater than those measured in lateral direction. The ratio between the swelling pressures in lateral and vertical directions was found between 0.34 and 0.98. The results of the SEM analyses suggested that the clay minerals in Ankara clay show horizontal and/or nearly horizontal sheeting and have stepped face-to-face structure. This arrangement indicates that the swelling parameters in vertical direction should be greater than those in lateral direction. It also confirms the experimental results and shows the influence of the microstructure of the clay on swelling anisotropy.

Geotechnical evaluation of Turkish clay deposits: a case study in Northern Turkey

Clay deposits in Oltu-Narman basins (Erzurum, northern Turkey) have been studied to determine their engineering properties and to evaluate their uses for geotechnical applications. These deposits are concentrated in two different stratigraphic horizons namely the Late Oligocene and the Early Miocene sequences. Clay-rich fine-grained sedimentary units are deposited in shallow marine and lagoonar mixed environments. Their clay minerals originated by the alteration of Eocene calc-alkaline island-arc volcanics, preferably from pyroclastics (trachite and andesite flow), which form the basement for the Oltu depression. Smectite group clay minerals are found abundant in clay deposits. The experimental results show that the clay soils have high plasticity behaviors and low hydraulic conductivity properties. The optimum water content, the free swell, and the swelling pressure of clay samples decreased and the maximum dry unit weight of clay samples increased under high temperature. Consequently, it is concluded that the expanding of clay soils is an important soil problem that cannot be avoided in the significant parts of Oltu city and its villages. However, the soils of clay-rich layers in the outcrops-section of clay deposits can be successfully used to build compacted clay liners for landfill systems and to construct vertical and horizontal barriers for protection of ground water and for preventing soil pollution in geotechnical applications.

Microstructural Development on Firing Illite and Smectite Clays Compared with that in Kaolinite

Thermal transformation of illite and smectite group clay minerals was studied using X‐ray diffraction and transmission electron microscopy, and the results were compared with those of kaolinite. Differences were observed in the types and sizes of crystals formed at temperatures between 800° and 1400°C. Spinel‐type phases were formed after 3 h at 1000°C in all three clays, but the morphology and composition of the spinel crystals varied. Mullite crystals reached greater sizes in the illite (>10 μm needles) and smectite (>1 μm) materials than in the kaolinite (0.5 μm). Iron‐rich crystals formed in the illite and smectite materials, and feldspars present as impurities in these clays, along with interlayer cations, resulted in large quantities of liquid being formed above 1000°C. Similar thermal breakdown and phase development schemes are proposed for all three materials, with the major differences observed ascribed to the presence or absence of interlayer cations, substitutional impurities, and accessory minerals. These results provide a basis for predicting phase development on firing a given clay mineral, if its characteristics and impurity levels are known.

FT-IR and FT-Raman spectroscopic investigations of adsorption of 2,2′-biquinoline by smectite group clay minerals from Anatolia

The sorption of 2,2′-biquinoline onto natural and ion-exchanged montmorillonite (Fe-, Co- or Cu-montmorillonite) and saponite from Anatolia have been investigated using FT-IR and FT-Raman Spectrometry. The intercalation of 2,2′-biquinoline within natural and ion-exchanged montmorillonite and saponite has been shown by X-ray diffraction to increase the interlayer spacing. The difference of basal spacing of air-dried clays and biquinoline treated ones shows monolayer arrangement. Raman spectroscopy was particularly useful for investigation of clay-organic interaction. Vibrational spectroscopy indicates that intercalated 2,2′-biquinoline molecules are coordinated to exchangeable cations (directly and indirectly through water bridges) and/or Lewis acid sites or as bidentate ligand.

Adsorption of 2,2?-bipyridyl onto sepiolite, attapulgite and smectite group clay minerals from anatolia: The FT-IR and FT-Raman spectra of surface and intercalated species

The adsorption of 2,2′-bipyridyl by natural sepiolite, attapulgite, hectorite, saponite and natural and ion exchanged (Mn, Fe, Co, Ni, Cu, Zn or Sn) bentonites has been investigated by FT-IR and FT-Raman spectroscopy. Spectroscopic results indicate that most of the adsorbed molecules are coordinated to either exchangeable cations (in the case of smectite group clays) or Lewis acidic centres (in the case of sepiolite and attapulgite) as bidentate ligands. The formation of monoanionic surface species has also been detected, to a relatively small extent. No physisorbed surface species has been observed. XRD patterns and UV-visible spectra of the samples are also recorded for additional information.

A vibrational spectroscopic study of the adsorption of 4,4?-bipyridyl by sepiolite and smectite group clay minerals from Anatolia (Turkey)

The adsorption of 4,4′-bipyridyl by natural sepiolite and smectite group clay minerals (bentonite, hectorite and saponite) from Anatolia (Turkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of adsorbed 4,4′-bipyridyl indicate the presence of chemisorbed species. However, any evidence for the generation of anionic species on the surface of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectite group clays are coordinated to exchangeable cations both directly and also indirectly through water as monodentate ligands. XRD patterns of the clays studied are also recorded.