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This article examines the clay mineralogy of twelve representative soils developed from gypsum-rich parent materials on several geomorphic positions. These soils were classified as Haploxerept, plus one profile as Humixerept and another as Xerorthent. The clay mineralogy, determined by X-ray diffraction, showed quite a similar clay composition in all profiles, with mica, chlorite, and smectite, from most to less abundant. Mica and chlorite are deemed inherited, while smectite—appearing in minor proportions—could result from both transformation and/or neoformation, because the leaching of bases by free drainage does not favor the transformation of mica to smectite. Therefore, the differences in clay mineralogy appeared to be lithogenic rather than pedogenic. These compositional data are an advance in the basic knowledge of the studied soils. [ABSTRACT FROM AUTHOR]

Ryugu asteroid grains brought back to the Earth by the Hayabusa2 space mission are pristine samples containing hydrated minerals and organic compounds. Here, we investigate the mineralogy of their phyllosilicate‐rich matrix with four‐dimensional scanning transmission electron microscopy (4D‐STEM). We have identified and mapped the mineral phases at the nanometer scale (serpentine, smectite, pyrrhotite), observed the presence of Ni‐bearing pyrrhotite, and identified the serpentine polymorph as lizardite, in agreement with the reported aqueous alteration history of Ryugu. Furthermore, we have mapped the d‐spacings of smectite and observed a broad distribution of values, ranging from 1 to 2 nm, with an average d‐spacing of 1.24 nm, indicating significant heterogeneity within the sample. Such d‐spacing variability could be the result of either the presence of organic matter trapped in the interlayers or the influence of various geochemical conditions at the submicrometer scale, suggestive of a range of organic compounds and/or changes in smectite crystal chemistry. [ABSTRACT FROM AUTHOR]

Sedimentary rock–hosted stratiform copper deposits are the world's second largest source of copper and the largest source of cobalt, with about 73% of the copper occurring in two basins: the Katangan Basin (Central African Copperbelt) and the Permian Basin (Kupferschiefer). Why these two sedimentary basins are so highly endowed in copper is puzzling because sedimentary rock–hosted stratiform copper deposits have formed since the Paleoproterozoic and they all share remarkably similar ore mineralogy, host-rock characteristics and basin settings. We suggest that this discrepancy is due to the development of these two basins close to the bases of ~ 8000-km-long supermountain belts. The supermountain belts were instrumental in raising oxygen levels in Earth's atmosphere, as well as providing a voluminous source of groundwater and a powerful and long-lived driver for the fluid-flow system. The elevated oxygen levels facilitated the diagenetic processes that converted copper-bearing labile minerals to amorphous iron-oxides and smectite and then in turn to hematite and illite. When oxidized brines flushed through the basin successions, the liberated copper was transported to units containing carbon-rich mudstone and the metals were deposited. For the Katangan Basin, development of the Transgondwanan supermountain belt along its margins between about 525 and 510 Ma explains the delay of several hundreds of millions of years between basin formation and mineralization in the Central African Copperbelt. In contrast, development of the Mid-Pangean supermountain belt formed penecontemporaneous with the Permian Basin explains the similarity in timing between basin formation and mineralization in the Kupferschiefer. [ABSTRACT FROM AUTHOR]

The mineralogical composition of Bobov Dol sub-bituminous coals from the lower part of the coal-bearing formation, was studied using optical microscopy, XRD and SEM-EDS analyses. Clay minerals (smectite, illite and kaolinite) and quartz, are the dominant minerals. Their characteristics indicate predominant terrigenous origin and argue for major detrital input from intermediate to mafic rocks. Accessory epigenetic barite-celestine mineralization, substituting almost completely oxidized siderite crystals and spheroidal aggregates, denotes circulation of meteoric aqueous solutions in the absence of other fracture-filing minerals. Finite glass spheres from the top of the coal seam I indicate synchronous volcanic activity, which did not influence peat formation. [ABSTRACT FROM AUTHOR]

A geological, mineralogical, and geochemical characterization of the Tamame de Sayago (Zamora, Spain) deposit was carried out with the aim of knowing the conditions that facilitated the genesis in the same deposit of kaolinite and smectites. The alteration processes affecting a Variscan granite were deduced throughout the study of a very wide group of representative samples by X-ray diffraction (XRD), scanning electron microscopy (SEM), chemical analyses of major, minor, and trace elements, as well as δ18O, δ34S stable isotope and K/Ar dating analyses. In addition, 2D and 2.5D graphs of the kaolinite and smectite isoconcentrations were obtained from core data. According to the color and texture, two different clayey rock types were identified and named as homogeneous alteration zones (ZAHO) and heterogeneous alteration zones (ZAHE). The ZAHO are regoliths in which the granite texture is preserved, and the feldspars are almost completely kaolinized. In the ZAHE, the original texture of the granitic rock is lost, and the main clay mineral is smectite. The mineralogical composition is similar, with kaolinite, smectite, mica, quartz, scarce feldspar, and occasionally natroalunite and APS (aluminum-phosphate-sulphate); however, the mineral concentration varies considerably because ZAHO are rich in kaolin areas whereas ZAHE are bentonitic areas. Both rock types contain numerous veins and nodules. The weathering of the Paleozoic granite alongside the absence of sedimentation during the Mesozoic led to the formation of kaolinite that is preserved in ZAHO materials. Nonetheless, during the Cretaceous–Tertiary transit, the conditions of tectonic stability varied. Late Variscan faults reactivated which allowed the percolation of Mg- and Ca-rich hydrothermal fluids through the already kaolinized granite, increasing the alteration of the primary silicates and leading to the formation of smectites in ZAHE materials. The amount of smectites is greater closer to the faults. The stable isotopes indicate the meteoric nature of the low-temperature hydrothermal fluids. The K/Ar data obtained from the natroalunite of veins indicate that those hydrothermal fluids circulated in different pulses from 66.4 ± 1.7 to 58.8 ± 1.5 Ma, as a minimum. Those ages are coincident with the first formation stages of the Duero Basin. [ABSTRACT FROM AUTHOR]

The mineralogical, structural and crystal-chemical features of seven samples of globular phyllosilicates of the glauconite–illite series (GPS) from the Lower Cambrian sequences of Northern Estonia and Western Lithuania, from the Middle Cambrian sequences of Western Latvia, and also from the Lower Ordovician sequences of Northern Estonia and Western Latvia are considered for the first time. Based on Al index (KAl = VIAl/[VIFe3+ + VIAl]) varying from 0.27 to 0.59, the globular phyllosilicates are attributed to the glauconite–illite series, most of which are represented by glauconites (the Al index is KAl = 0.27–0.46) and one sample, by Al-glauconite (KAl = 0.59). The K2O content in minerals is from 7.12 to 7.90%. The content of expandable layers (4–13%), their types (smectite, vermiculite), and the character of their alternation (R = 0, R = 2) were determined for the first time in the studied samples by simulation of experimental X-ray diffraction patterns from oriented specimens. Simulation of X-ray diffraction patterns obtained from unoriented specimens made it possible to determine the degree of three-dimensional order and mean values of the unit-cell parameter b (9.056–9.094 Å), as well as the distribution of their individual micaceous varieties. Based on these data, the microheterogeneity of the Cambrian and Ordovician GPSs was established and compared with the heterogeneity in the previously studied Riphean GPS (Drits et al., 2013). The obtained Rb-Sr и K‑Ar ages for the studied Middle Cambrian and Lower Ordovician samples, as well as the earlier published dates for the Lower Cambrian samples, are "rejuvenated" relative to age limits accepted for the Cambrian and Lower Ordovician (Gradstein et al., 2020). The relationship of the Cambrian and Lower Ordovician "rejuvenated" isotopic dates and the discovered GPS heterogeneity, as well as possible reasons for its occurrence, are discussed. [ABSTRACT FROM AUTHOR]

A quantitative understanding of the molecular-scale mechanisms of radionuclide sorption on different clay minerals is crucial for the development and safe implementation of geological nuclear waste disposal technologies. We apply classical molecular dynamics (MD) computer simulations to study the adsorption of uranyl on the external basal surfaces of two typical clay models. In the illite model, negative charge is primarily localized in the tetrahedral sheets, while in the lower-charge smectite model, the isomorphic substitutions are introduced in the octahedral sheet. The comparison of atomic density distributions at the clay surfaces and adsorption-free energies profiles as a function of distance from these surfaces demonstrates that overall U behavior at the basal clay surface is quite similar for illite and smectite. Uranyl is sorbed as a mixture of outer-sphere aqua complexes [UO2(H2O)5]2+ and hydrolyzed aqua complexes [UO2(H2O)4–5OH]+ on both surfaces. The structural and compositional differences between the models do not greatly affect the uranyl’s nearest coordination environment and are mainly reflected in the specific localization and orientation of the uranyl ions at both surfaces and in the magnitude of the adsorption-free energies. The observed quantitative characteristics of uranyl interactions with illite and smectite surfaces will help to better understand U behavior during the sorption process on clay minerals for the entire range of mixed-layer illite–smectite structures. A comparison of two versions of the ClayFF force field in the simulations made it possible to more accurately and quantitatively evaluate some subtle features of the uranyl–clay interactions and to obtain a more precise composition of uranyl complex with the modified ClayFF force field (ClayFF-MOH).

Numerous experiments have verified that smectites can adsorb aflatoxin B1 (AfB1) effectively and the efficiency of this process depends heavily on the chemical, physical, and mineralogical characteristics of the smectite. Several relationships between these characteristics and AfB1 sorption have been determined experimentally, but the molecular mechanisms underlying these were not investigated. In the current study the effects of charge density, type of exchange cation, and charge origin (octahedral vs. tetrahedral) on AfB1 sorption on smectites were analyzed by a series of molecular simulations. The calculations confirmed the formation of water bridges between carbonyl groups of AfB1 molecules and interlayer cations. Flat orientation of AfB1 molecules on smectite surfaces was also confirmed. For larger amounts of AfB1 molecules in the intercalates, self-association of two AfB1 molecules bound by π–π interaction was shown. The thermodynamics of AfB1 sorption depends heavily on the water content in the structure, being optimal for basal distances corresponding to two layers of water. A clear preference for sorption of AfB1 on smectites with bivalent cations (Ba2+, Ca2+) and an octahedral origin of its layer charge was confirmed and this was explained as steric hindrance between hydrated ions and AfB1 molecules, which tend to lie flat on smectite surfaces devoid of ions. Ba-montmorillonite with a charge of 0.4 per half unit cell was shown to have the smallest and thus the best potential energy of adsorption compared to the other layer charges. [ABSTRACT FROM AUTHOR]

The Ni-laterite deposit at the San Felipe plateau, located 30 km northwest of Camagüey, in central Cuba, is the best example of a clay-type deposit in the Caribbean region. San Felipe resulted from the weathering of mantle peridotites of the Cretaceous Camagüey ophiolites. In this study, a geochemical and mineralogical characterization of two profiles (83 and 84) from the San Felipe deposit has been performed by XRF, ICP-MS, quantitative XRPD, oriented aggregate mount XRD, SEM, FE-SEM, and EMPA. Core 83, with a length of 23 m and drilled in the central part of the plateau, presents a notable concentration of cryptocrystalline quartz fragments and a rather poor content of NiO, averaging 0.87 wt.%. Core 84, which is 12 m long and drilled at the border of the plateau, lacks silica fragments and presents a higher NiO content, averaging 1.79 wt.%. The smectite structural formulae reveal that they evolve from trioctahedral to dioctahedral towards the top of the laterite profiles. Quantitative XRD analyses indicate that smectite is a dominant Ni-bearing phase, accompanied by serpentine and minor chlorite. Serpentine, as smectite, is enriched in the less soluble elements Fe3+, Al, and Ni towards the top of the profiles. Core 83 seems to have been affected by collapses and replenishments, whereas core 84 may have remained undisturbed.

In this study, raw smectite (Sm), from the Guarapuava–Parana–Brasil region, was saturated with copper ions (Cu-Sm) by ion exchange and the samples Sm and Cu-Sm were used in crystal violet (CV) adsorption and applied as an antimicrobial and antifungal hybrid pigment. Samples (Sm and Cu-Sm) were used to remove crystal violet (CV) dye from aqueous media, simulating wastewater. Samples after use as adsorbents were characterized and named smectite/adsorbed dye (Sm/Dye) and copper smectite/adsorbed dye (Cu-Sm/Dye); and they were applied as hybrid pigments with antimicrobial action. The Sm and Cu-Sm were characterized by X-ray diffractometry (XRD), energy dispersive X-ray fluorescence (EDXRF), vibrational spectroscopy (FTIR), Zeta potential (ζ), scanning electron microscopy (SEM), and colorimetry (CIE L*a*b*), enabling the identification of the presence of intercalated copper ions and on the smectite surface. The adsorption assays were carried out to evaluate the effects of initial dye concentration and contact time. Tests for application as a hybrid pigment showed good compatibility with commercial white paint being applied on plaster blocks and later photoaging and chemical stability tests were performed in acid and basic environments, both were discussed by colorimetry (CIE L*a*b*), thus being able to relate it to the color variation (∆E). The samples (Sm, Cu-Sm, Sm/Dye, and Cu-Sm/Dye) were dispersed in white paint at 10% and 20% (% w/w) to evaluate the ability to inhibit different microorganisms. The modification with copper ions promoted an increase in the adsorptive capacity relative to the raw smectite and provided antibacterial and antifungal action to the hybrid pigment against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Candida albicans. The Cu-Sm and Cu-Sm/Dye samples showed excellent results against all studied microorganisms and reveal successful materials that can be used in environments that require microbiological protection.

The Sinanpaşa basin, one of the Neogene basins formed in the extensional tectonic regime in Western Anatolia, is located on the eastern margin of Western Anatolia basins containing different types of evaporites, lignite, uranium and clay minerals. Miocene sequence was initiated with alluvial fan- fluvial units and followed by lacustrine sediments. River floodplains and lakeshore marshes locally contain economic coal levels. Since middle-late Miocene, the products of Afyon volcanism were deposited into a subaerial or a subaqueous environment alternating with lake sediments. Dominant clay minerals are illite and smectite within the sediments coexistence with the volcanics. These minerals were accompanied by chlorite, kaolinite, and zeolite in some samples. Feldspar, dolomite, thenardite, and gypsum are locally observed too. Sepiolite mineral enrichments are also noteworthy in shallow-coastal lacustrine environments where organic matter is abundant. Clay minerals are mostly detritic and developed due to the weathering of volcaniclastics and sedimentary rocks in temperate/humid climatic conditions. In particular, smectite and kaolinite minerals were formed in situ/authigenic under subaqueous conditions due to the acidic/basic character of tuffs. As a result, different clay mineral types have been developed due to the mineralogical composition of source rocks, climatic factors (humid/semi-humid, arid), paleotopography, depositional environment and diagenetic factors.

The fate of chemical pollutants in the environment is determined by various factors including the type and strength of their interactions with reactive surfaces in soils and sediments. In the present work the interactions of hexachlorobenzene (HCB) with the surface of a common clay mineral belonging to the smectite group montmorillonite (MNT) is studied by means of the density functional theory method. The MNT net surface charge, induced by isomorphic substitutions, is systematically varied and compensated by Ca2+ cations. Based on the calculated electron densities, conclusions are drawn revealing the nature of their mutual interactions, the related stability of such surface complexes as well as possible molecular arrangements. It becomes apparent that the dominant contribution to the stability of HCB-MNT complexes arises from the cation-π interactions between the HCB molecule and the nearest compensating Ca2+ cation and thus besides the MNT net surface charge the type and size of the compensating cations are expected to play a crucial role in understanding the HCB adsorption on MNT. This systematic study aims to contribute to a better mechanistic understanding of the interactions between hydrophobic organic compounds and reactive mineral surfaces.

The Mallorca coastal caves present large amounts of speleothems that have been studied for decades. However, the sedimentary deposits also present in these cases have not been given the same attention. This work is the first study entirely focused on these deposits, specifically the ones found in the Ases cave. These deposits are formed by clay minerals (illitic phases, kaolinite, smectite, and chlorite), calcite and quartz, and minor proportions of dolomite, albite, orthoclase, hematite, and goethite. The grain size and the electron microscopy studies suggested the presence of different sedimentation processes (bedrock degradation, creep or saltation, and suspension) and different origins (authigenic and detrital origins) for the different sediments. Based on these differences, two types of deposits were characterized: autochthonous and allochthonous deposits. The first ones are located on the floor of chambers and corridors in subaqueous zones, indicating the stability of the mixing zone (and therefore the sea level) over time. The second ones appear filling voids on the walls and the ceiling in the terrestrial zone, evidencing the filling of the cavity in the presence of water (during a wet period). These results are very important to complete the understanding of the caves and their evolution and support the relevance of these materials in paleoenvironmental studies.

New magnetic nanocomposite sorbents were obtained by doping natural bentonite with nanosized CoFe2O4 spinel (10 and 20 wt.%). Nanocrystals of cobalt ferrite were synthesized by a citrate burning method. The structure and physical-chemical properties of the composites were characterized by XRD, XRF, TEM, BET, FTIR and Faraday balance magnetometry. During the formation of nanocomposites, 10–30 nm particles of cobalt ferrite occupied mainly the interparticle space of Fe-aluminosilicate that significantly changed the particle morphology and composite porosity, but at the same time retained the structure of the 2:1 smectite layer. A combination of two functional properties of composites, adsorption and magnetism has been found. The adsorption capacity of magnetic nanosorbents exceeded this parameter for bentonite and spinel. Despite the decrease in the adsorption volume, pore size and specific surface area of the composite material relative to bentonite, the sorption activity of the composite increases by 12%, which indicated the influence of the magnetic component on the sorption process. FTIR data confirmed the mechanism of formaldehyde sorption by the composite sorbent. The production of a magnetic nanosorbent opens up new possibilities for controlling the sorption processes and makes it possible to selectively separate the sorbent from the adsorption medium by the action of a magnetic field.

This study reveals mineral and deformation processes associated with faulting of lacustrine unconsolidated sediments in the Guadix-Baza Basin (Betic Cordillera, S Spain) affected by the Baza Fault. Brittle carbonate and silt sediments develop deformation bands frequently sealed by dolomite crystallization, whereas ductile clay-rich sediments form clay smearing bands where late crystallization of gypsum can be observed. Granular flow and local cataclasis were the main deformation mechanisms in the brittle deformation bands. Flow alignment, grain-boundary sliding, and extrusion were predominant in the clay smearing bands. These water and clay-rich bands reduced shear strength of the faulting process due to their lubricating effect. Beidellitic smectite defines shear foliation of the smeared bands, but Mg-Fe, a K-rich smectite (Fe + Mg > 1 and K content up to 0.8 a.p.f.u), crystallizes in the micropores surrounding brittle clasts produced by deformation pressure shadows. These data suggest that the interaction of micromechanical events, which increased sediment porosity by the generation of pressure shadows, and the flow and concentration of saline fluids in these pores promoted structural diagenesis processes that favoured the beginning of local illitization.

A calcium bentonite clay from Boane region (Mozambique) was subjected to an Na2CO3 activation process. The methylene blue test together with energy-dispersive X-ray spectroscopy (EDX) analysis indicated the successful ion exchange of Ca2+ by Na+ ions since the cation exchange capacity (CEC) increased from 67.5 to 74 meq/100 g and the Na/Ca ratio from 2.91 up to 15.8, as the concentration of Na2CO3, activation temperature, and activation time were varied from 2 to 6 wt.%, from 25 to 65 °C, and from 2 to 4 h, respectively. However, the increase in the CEC did not follow the same trend as the increase in the Na/Ca ratio, and for the case of Na2CO3 concentration, the increase in the CEC was limited. The X-ray diffraction (XRD) patterns also confirmed that Ca-rich bentonite was effectively modified into Na-bentonite since after the activation, the d(001) decreased from 1.52 nm to 1.30 nm. The statistical design of the experiments showed that as well as the time and the temperature × time linear interactive effect, all the other independent factors and their interactive effects had a significant influence on the CEC. The response surface methodology (RSM) indicated that higher values of the CEC can be obtained under the optimal activation conditions of 4 wt.% Na2CO3, at a temperature of 45 °C, and with an activation time of 3 h. A statistical model was used to predict the CEC, and the R2 value was 0.99529, which denotes a satisfactory result in predicting the CEC.

We present the formation of shrink–swell (SS) soils on the shale geology of Chhattisgarh basin (CB), India, and its implications on sustainable agriculture management. In this study, four pedons (P1, P2, P3, and P4) were studied in a 10 km transact for their morphological, physical, chemical and mineralogical properties. Pedons P1 and P3 have more than 50 % clay, developed from shale and have both di- and tri-octahedral smectite in their fine clay fractions, and classified as Vertic Inceptisols. The pedons P2 and P4 with 65 % clay were developed from basaltic alluvium, with well-developed slickenside horizons and classified as Typic/Sodic Haplusterts. Based on the drainage line analysis, we attribute the formation of these SS soils to the riverine deposits of Deccan basalt (DB) from the higher elevation to valley portions, transported from the Maikal range of Central India. The presence of low-charge di-octahedral smectite of Vertisols and di- and trioctahedral nature of smectite in Inceptisols combinations are rare, but this possibility arises from mica (biotite) in the shale. These clays play a vital role in edaphological aspects, specifically rice-based agro-management (particularly in potassium and nitrogen) practices in this basin. High exchangeable magnesium per cent (EMP) and low exchangeable sodium per cent (ESP) in subsoil enhance the water storage in subsoils and its utilization during dry spell by the rice crop. Such kind of edaphological studies with decoding the pedological data is minimum. This research decodes the current information and paves a role in rationalizing the rice production system using the scientific methods of input usage. [ABSTRACT FROM AUTHOR]

In the past years an increasing demand for bentonites resulted in the opening of new bentonite deposits in the Jastrabá Formation. The shortage of information, in particular analytical data, on the bentonites from the newly opened Jastrabá Fm. deposits was the motivation for the current study. Smectite is the predominant mineral in all bulk bentonites from the new deposits. Its amount varied between 43 and 90 wt. %. The bulk bentonites also contain variable amounts (10–57 wt. %) of mineral admixtures such as feldspars, mica, opal-CT, kaolinite, quartz and sometimes goethite. The smectite mineral comprising the studied bentonites was montmorillonite. The octahedral Al in the structure of montmorillonite was partially substituted by Mg, and to a lesser extent by Fe. The interlayer space of montmorillonite is occupied predominantly by divalent exchangeable cations (Ca2+ and Mg2+). The dehydroxylation temperature of smectites (>600 °C) determined on the DTG curves indicates the presence of the cis-vacant variety of montmorillonites. The mean crystallite thicknesses of smectites (TMEAN) calculated by BWA analyses ranges from 7.2 to 11.5 nm. The shape of the crystallite thickness distributions (CTDs) for smectites is lognormal in all cases. Cation exchange capacity (CEC) and total specific surface area (TSSA) increases with increasing amount of smectite. The CEC of 101 meq/100g and TSSA of 616 m2/g correspond to bulk bentonite from the Stará Kremnička III deposit containing 89 wt. % of smectite.

Lithofacies belonging to mud-flat and palustrine deposits (lake margin) in the Miocene of the Madrid Basin (Spain) have been studied. Four lithofacies corresponding to mud flat (1 and 3) and palustrine (2 and 4) deposits have been differentiated. Units 1 and 3 consist mainly of mudstones and carbonates (calcretes and diolocretes). The clay fraction is dominated by trioctahedral smectite (up to 79%) with illite and kaolinite as minor components. The d(060) spacing value shows reflections at 1.52 and 1.50 Å indicating also the presence of dioctahedral phyllosilicates. Unit 2 consists predominantly of lutites (claystones), locally with carbonate and chert nodules. The clay fraction is dominated by sepiolite (up to 96%) with variable contents of smectite and subordinate illite. The d(060) spacing value shows reflections at 1.51 and 1.52 Å indicating trioctahedral clay minerals. Unit 4 consists mostly of carbonates (limestones) with mudstone and lutite inserts. The clay fraction shows different contents of sepiolite, palygorskite and dioctahedral smectite. The analysis of a selection of trace elements (Cr, Co, Th, La, Sc) has allowed us to determine the characteristics of the source area as dioritic, somewhat different from those of the nearby materials from the Batallones sector. Sepiolite shows FWHM values ranging between 0.68 and 1.10 (2θ), indicating “low crystallinity sepiolite”. Differences in the conditions of formation of magnesian smectite and palygorskite have been observed in the mud-flat and palustrine deposits. The formation of sepiolite mainly by neoformation in palustrine deposits with different hydrochemistry is remarkable, leading to differences in fibre size and crystallinity of the fibrous clay mineral. Authigenic transformation processes from previous Al-rich phases would be responsible for the formation of saponite and palygorskite in mud flat and palustrine environments, with different pH conditions.

The mineralogical composition of nano-clays (NCs), and their potential implications in soil bulk properties of Indian Vertisols are unexplored. In this study, we have isolated NCs (<100 nm) from Deccan basalt (DB) alluvium derived Vertisols (Typic Haplusterts) of central India and characterized them for their mineralogy and crystalline behavior. The soils are clayey (>60%) in texture, rich in smectite mineral (60–80% in <2 μm fraction), alkaline (pH 7.8–8.5), calcareous, and contain <1.0% organic carbon. The clay fraction (<2 μm) is dominated by smectitic NC (40–60%) followed by hydroxy-interlayered vermiculite (HIV), pedogenic chlorite (PCh), kaolinite, and mica. The smectite is little hydroxy-interlayered (HIS), and hydroxy-interlayering is less pronounced in NC smectites than in the coarser clay smectites. The NC smectites are of smaller crystallite size (3.5–5.5 nm) and higher in crystal strain (15–22%) than coarser size clays because of its low lattice charge. The abundance of smectitic NCs considerably reduces the saturated hydraulic conductivity (<1 cm hr–1) of the soils due to high dispersion and swelling (COLE ≥ 0.20) of smectite clays even at the low level of exchangeable sodium percentage (ESP ≤ 5) and a moderate amount of exchangeable magnesium. The report on nano clays (<0.1 μm) highlights the unique role of nano smectites in some selected soil properties, as well as in the origin of SAT Vertisols of the Indian subcontinent. [ABSTRACT FROM AUTHOR]

Although the Mesozoic rocks of the Transdanubian Range have been the subject of a multitude of different studies, mineralogical research is largely underrepresented. The clay mineralogy of Lower Jurassic (especially the Pliensbachian and Toarcian) strata was broadly investigated earlier; however, systematic high-resolution clay mineralogical studies remain scarce. Here we present a mineralogical study focusing on the Upper Pliensbachian strata of the Lókút-Hosszúárok section, located near the Eplény Manganese Ore Field. We identified dioctahedral smectite, randomly interstratified illite/smectite, illite as 10 Å phyllosilicate, quartz and cristobalite. Based on our new results we propose that the smectite was formed by aging of Mg or Fe hydroxide-silica precipitates. The smectite and cristobalite were presumably formed from the siliceous tests of radiolarians, whose abundance was controlled by a local upwelling system. The occurrence of Pliensbachian smectite in the Lókút outcrop shows similarities with the Úrkút smectites known from both Pliensbachian and Toarcian strata, which implies that similar processes controlled the sedimentation during the Pliensbachian as well as during the black (gray) shale-hosted ore accumulation in the Eplény and Úrkút basins. [ABSTRACT FROM AUTHOR]

The Sinanpaşa basin, one of the Neogene basins formed in the extensional tectonic regime in Western Anatolia, is located on the eastern margin of Western Anatolia basins containing different types of evaporites, lignite, uranium and clay minerals. Miocene sequence was initiated with alluvial fanfluvial units and followed by lacustrine sediments. River floodplains and lakeshore marshes locally contain economic coal levels. Since middle-late Miocene, the products of Afyon volcanism were deposited into a subaerial or a subaqueous environment alternating with lake sediments. Dominant clay minerals are illite and smectite within the sediments coexistence with the volcanics. These minerals were accompanied by chlorite, kaolinite, and zeolite in some samples. Feldspar, dolomite, thenardite, and gypsum are locally observed too. Sepiolite mineral enrichments are also noteworthy in shallow-coastal lacustrine environments where organic matter is abundant. Clay minerals are mostly detritic and developed due to the weathering of volcaniclastics and sedimentary rocks in temperate/humid climatic conditions. In particular, smectite and kaolinite minerals were formed in situ/authigenic under subaqueous conditions due to the acidic/basic character of tuffs. As a result, different clay mineral types have been developed due to the mineralogical composition of source rocks, climatic factors (humid/semi-humid, arid), paleotopography, depositional environment and diagenetic factors. [ABSTRACT FROM AUTHOR]

Lakes are particularly sensitive to environmental fluctuations, which are recorded in their facies and stratigraphy. Ephemeral lakes reveal their sensitivity to palaeoenvironmental changes in the overprinting of the sedimentary features in every single bed. Tetrapod‐track taphonomic‐modes and ichnological taphonomic‐pathways can be used as sensitive indicators of environmental conditions of the track‐bearing beds during deposition and imprinting. The Middle Triassic Cerro de las Cabras succession (Cuyana Basin, Argentina) provides an excellent opportunity to these environmental indicators in an underfilled palaeolake. A model of ichnological preservation for underfilled lake systems is proposed and the role of the ichnology record in the sequence stratigraphy analysis is evaluated, based on the integration of tetrapod‐track modes, taphonomic‐pathways of playa‐lake ichnofauna, mineralogy and physical data. Soft‐ground suites include those dominated by invertebrate grazing traces and arthropod locomotion traces (Suite 1), and those overprinted by horizontal‐vertical dwelling burrows with tetrapod tracks preserved in taphonomic modes B and C (Suite 2). The firm‐ground suite (Suite 3) comprises tetrapod‐tracks with the best preservation styles (modes A and B) along less abundant invertebrate dwelling and feeding traces as found in Suite 2. Clay mineralogy (dominated by illite with subordinate smectite) suggests low plasticity of the layers, in agreement with low‐relief deformation structures observed in tetrapod‐track taphonomic‐modes. The well‐preserved track tetrapod features documented in the Cerro de las Cabras succession, together with the absence of pedogenic disturbance, trampling obliterating the footprints, and/or evidence of strong disturbance by wind, desiccation and/or precipitation, supports short periods of exposure of the imprinted surface particular to this succession. An integrated multiproxy approach is proposed to evaluate the evolutionary interpretation and identification of autogenic versus allogenic controls in underfilled lake‐basin histories. The observed aggradational‐trend suggests an equilibrium between rates of accommodation change and sediment supply, and that the basin‐centre did not experience prolonged sediment‐starved conditions. [ABSTRACT FROM AUTHOR]

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Widespread alteration in the Early-Middle Triassic volcanic ash of the Xiejiacao section, south China, has resulted in significant occurrences of lithium-rich K-bentonite deposits with economic potential. Detailed mineralogical and geochemical investigations of Li-rich K-bentonite deposits from the Xiejiacao section of Guangan city, South China, are presented here. The X-ray diffraction (XRD) data and major element chemistry indicates that the Li-rich K-bentonite deposits contain quartz, clay minerals, feldspar, calcite and dolomite, and the clay minerals are dominated by illite and ordered (R3) illite/smectite (I/S). The concentrations of major and trace elements in Li-rich K-bentonite deposits altered from volcanic ashes are most likely derived from felsic magmas, associated with intense volcanic arc activity. The composition of the clay components suggests that the Li-rich K-bentonite deposits are probably altered from the smectite during diagenesis, whereas smectite is mainly formed by submarine alterations of volcanic materials and subsequently the I/S derived from the volcanogenic smectite illitization. Moreover, accurate determination of the structure in I/S reveals that the temperatures reached by the sedimentary series are around 180 °C with a burial depth of ~6000 m. The widely distributed lithium-rich clay deposits strongly indicate widespread eruptions of volcanic ashes in the Early-Middle Triassic, which released huge amounts of volcanic ash. Lithium fixed in the illite and I/S is considered to have leached from the volcanogenic products by a mixed fluid source (i.e., meteoric, porewater and hydrothermal fluids). These Li-rich clay minerals in the marine basin contain economically extractable levels of metal and are a promising new target for lithium exploration. [ABSTRACT FROM AUTHOR]

Lithium deposits in tuffaceous sediments of the McDermitt caldera constitute possibly the world's largest Li clay resource, yet their characteristics and origin are not established. The 40 × 25 km McDermitt caldera collapsed during the eruption of ~1000 km3 of a 16.4 Ma, zoned peralkaline to metaluminous tuff; minor caldera magmatism ceased by 16.1 Ma. About 200 m of sediments mostly composed of glass from regional pyroclastic eruptions accumulated in the caldera until about 15.7 Ma. Closed hydrologic system diagenesis (CHSD) altered the tuffaceous sediments to a consistent vertical mineral zonation of clay, analcime, K-feldspar, and albite. Entire sedimentary sections in the southern and western parts of the caldera basin have ≥1500 ppm Li. Lithium-rich intervals are dominantly claystone. The most thoroughly studied deposit is a laterally continuous, ~3000 ppm Li zone in the lower sedimentary section that also has high K, Rb, Mo, As, and Sb (and partly Mg and F). Lithium occurs as an illitic clay (tainiolite?). The overlying, upper sedimentary section averages <2000 ppm Li which resides in smectite (hectorite). A transitional zone has variably mixed smectite-illite clay and averages ~2000 ppm Li. An 40Ar/39Ar age of ~14.9 Ma on authigenic K-feldspar in the illite zone is ~1.2 Ma younger than the 16.1 Ma end of magmatism in the caldera, which mitigates against a simple hydrothermal origin. Closed hydrologic system diagenesis was essential to Li mineralization, but Li budget calculations suggest a source of Li in addition to the tuffaceous sediments is required. This additional source could be Li originally in highly enriched magma that entered the diagenetic system through either (1) Li in magma exsolved into a hydrous volatile phase during eruption. The Li-rich volatile phase coated glass shards or was trapped in pumice and was quickly leached by surface or groundwater upon deposition in the caldera. (2) Residual magma immediately following ash-flow eruption and caldera collapse generated Li-rich hydrothermal fluids that mixed with meteoric water in the closed caldera basin, generating a hybrid diagenetic fluid. The hydrothermal fluid and hybrid diagenetic fluids would have existed only during initial basin sedimentation between about 16.4 and 16.1 Ma. [ABSTRACT FROM AUTHOR]

The Weaklaw vent in SE Scotland (East Lothian coast), inferred to be Namurian, produced lava spatter and volcanic bombs. The latter commonly contained ultramafic xenoliths. All were metasomatised by carbonic fluids rich in incompatible elements. The lavas and xenoliths are inferred to have been basanites and lherzolites prior to metasomatism. The abundance and size of (carbonated) peridotite xenoliths at Weaklaw denotes unusual rapidity of magma ascent and high-energy eruption making Weaklaw exceptional in the British Isles. The lavas and xenoliths were altered subsequently by low-temperature (<200°C) carbo-hydrous fluids to carbonate, clay and quartz assemblages. A small irregular tuffisite 'dyke' that transects the ejecta is also composed dominantly of carbonates and clays. The peridotitic xenoliths are typically foliated, interpreted as originating as pre-entrainment mantle shear-planes. Analyses of the relic spinels shows them to be compositionally similar to spinels in local unaltered lherzolites from near-by basanitic occurrences. Chromium showed neither significant loss nor gain but was concentrated in a di-octahedral smectite allied to volkonskoite. It is in the complex association of smectite with other clays, chlorite and possibly fuchsite that the diverse incompatible elements are concentrated. We conclude that late Palaeozoic trans-tensional fault movement caused mantle shearing. Rapid ascent of basanite magma entrained large quantities of sheared lithospheric mantle. This was followed by ascent of an aggressive carbonate-/ hydroxyl-rich fluid causing pervasive metasomatism. The vent is unique in several ways: in its remarkable clay mineralogy and in displaying such high Cr-clays in a continental intra-plate setting; in being more productive in terms of its 'cargo' of peridotite xenoliths; in presenting an essentially un-eroded sequence of Namurian extrusives; and, not least, for giving evidence for post-eruptive, surface release of small-melt, deep-source fluids. [ABSTRACT FROM AUTHOR]

Interactions of bioorganic moieties with clay minerals have attracted attention not only from the perspective of novel bioclay materials but also because they play a crucial role in our understanding of physical and chemical processes in soils. The aim of the present article is to explore the interactions responsible for the formation of a phosphatidylcholine-kaolinite bioclay by employing a series of classical molecular dynamic simulations. Detailed analysis of the structure and energies of the resulting bioclays reveals that the phosphatidylcholine molecules bind to the kaolinite surface either via their zwitterionic heads or hydrophobic aliphatic tails, depending on the kaolinite surface characteristics and the density of organic coating. The phosphatidylcholine molecules have a tendency to form irregular layers with a preferred parallel orientation of molecules with respect to the kaolinite surface. The tails exhibit varying degrees of flexibility and disorder depending on their distance from the surface and the density of surface coating. Significant differences in the binding can be spotted with respect to the two types of kaolinite basal surfaces, i.e., the hydrophobic siloxane surface, which possesses a considerable dispersion character, and the hydrophilic alumina surface, polarized by the surface hydroxyl groups.

The mineral alteration patterns in high- to low-temperature geothermal fields affect the induced polarization (electrical conductivity and chargeability) properties of volcanic rocks. Indeed, these properties are sensitive to the cation exchange capacity and the porosity of the rock, which are both dependent on the alteration path, temperature, and depth of burial. Therefore induced polarization tomography appears as a powerful non-intrusive geophysical method to investigate alteration patterns in geothermal fields. Among clay minerals, the production of smectite through prograde reactions occurs progressively in volcanic rocks up to 220 °C. The presence of smectite dominates the induced polarization response of the volcanic rocks because of its very large cation exchange capacity. It follows that induced polarization can be used as a non-intrusive temperature proxy up to 220 °C for both active and inactive geothermal fields, recording the highest temperatures reached in the past. The influence of magnetite and pyrite, two semi-conductors, also has a strong influence regarding the induced polarization properties of volcanic rocks. Various field examples are discussed to show how induced polarization can be used to image volcanic conduits and smectite-rich clay caps in volcanic areas for both stratovolcanoes and shield volcanoes.

Compacted bentonite is currently being considered as a suitable backfill material for sealing underground repositories for radioactive waste as part of a multi-barrier concept. Although showing favorable properties for this purpose (swelling capability, low permeability, and high adsorption capacity), the best choice of material remains unclear. The goal of this study was to examine and compare the hydration behavior of a Milos (Greek) Ca-bentonite sample (SD80) in two types of simulated ground water: (i) Opalinus clay pore water, and (ii) a diluted saline cap rock brine using a confined volume, flow-through reaction cell adapted for in situ monitoring by X-ray diffraction. Based on wet-cell X-ray diffractometry (XRD) and calculations with the software CALCMIX of the smectite d(001) reflection, it was possible to quantify the abundance of water layers (WL) in the interlayer spaces and the amount of non-interlayer water uptake during hydration using the two types of solutions. This was done by varying WL distributions to fit the CALCMIX-simulated XRD model to the observed data. Hydrating SD80 bentonite with Opalinus clay pore water resulted in the formation of a dominant mixture of 3- and 4-WLs. The preservation of ca. 10% 1-WLs and the apparent disappearance of 2-WLs in this hydrated sample are attributed to small quantities of interlayer K (ca. 8% of exchangeable cations). The SD80 bentonite of equivalent packing density that was hydrated in diluted cap rock brine also contained ca. 15% 1-WLs, associated with a slightly higher concentration of interlayer K. However, this sample showed notable suppression of WL thickness with 2- and 3-WLs dominating in the steady-state condition. This effect is to be expected for the higher salt content of the brine but the observed generation of CO2 gas in this experiment, derived from enhanced dissolution of calcite, may have contributed to the suppression of WL thickness. Based on a comparison with all published wet-cell bentonite hydration experiments, the ratio of packing density to the total layer charge of smectite is suggested as a useful proxy for predicting the relative amounts of interlayer and non-interlayer water incorporated during hydration. Such information is important for assessing the subsequent rates of chemical transport through the bentonite barrier.

Bentonites are considered to be the most suitable materials for the multibarrier system of high-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representative of Czech Ca-Mg bentonites in this respect, it has been included in the Czech Radioactive Waste Repository Authority (SÚRAO) buffer and backfill R&D programme. Detailed knowledge of processes in the material induced by thermal loading provides invaluable assistance regarding the evolution of the material under repository conditions. Samples of both original BCV 2017 bentonite and the same material thermally treated at 200 °C were characterised by means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, thermal analysis, cation exchange capacity, specific surface area (BET) measurements, the determination of the swell index, the liquid limit, the swelling pressure and water retention curves. The smectite in BCV 2017 bentonite comprises Ca-Mg montmorillonite with a significant degree of Fe3+ substitution in the octahedral sheet. Two main transformation processes were observed following heating at 200 °C over 27 months, the first of which comprised the dehydration of the montmorillonite and the subsequent reduction of the 001 basal distance from 14.5 Å (the original BCV 2017) to 9.8 Å, thus indicating the absence of water molecules in the interlayer space. The second concerned the dehydration and partial dehydroxylation of goethite. With the exception of the dehydration of the interlayer space, the PXRD and FTIR study revealed the crystallochemical stability of the montmorillonite in BCV 2017 bentonite under the selected experimental conditions. The geotechnical tests indicated no major changes in the mechanical properties of the thermally treated BCV 2017 bentonite, as demonstrated by the similar swelling pressure values. However, the variation in the swell index and the gradual increase in the liquid limit with the wetting time indicated a lower hydration rate. The retention curves consistently showed the lower retention capacity of the thermally treated samples, thus indicating the incomplete re-hydration of the thermally treated BCV 2017 exposed to air humidity and the difference in its behaviour compared to the material exposed to liquid water.

Bentonite is currently proposed as a potential backfill material for sealing high-level radioactive waste in underground repositories due to its low hydraulic conductivity, self-sealing ability and high adsorption capability. However, saline pore waters, high temperatures and the influence of microbes may cause mineralogical changes and affect the long-term performance of the bentonite barrier system. In this study, long-term static batch experiments were carried out at 25 °C and 90 °C for one and two years using two different industrial bentonites (SD80 from Greece, B36 from Slovakia) and two types of aqueous solutions, which simulated (a) Opalinus clay pore water with a salinity of 19 g·L−1, and (b) diluted cap rock solution with a salinity of 155 g·L−1. The bentonites were prepared with and without organic substrates to study the microbial community and their potential influence on bentonite mineralogy. Smectite alteration was dominated by metal ion substitutions, changes in layer charge and delamination during water–clay interaction. The degree of smectite alteration and changes in the microbial diversity depended largely on the respective bentonite and the experimental conditions. Thus, the low charged SD80 with 17% tetrahedral charge showed nearly no structural change in either of the aqueous solutions, whereas B36 as a medium charged smectite with 56% tetrahedral charge became more beidellitic with increasing temperature when reacted in the diluted cap rock solution. Based on these experiments, the alteration of the smectite is mainly attributed to the nature of the bentonite, pore water chemistry and temperature. A significant microbial influence on the here analyzed parameters was not observed within the two years of experimentation. However, as the detected genera are known to potentially influence geochemical processes, microbial-driven alteration occurring over longer time periods cannot be ruled out if organic nutrients are available at appropriate concentrations.

First-order relationships between organic matter content and mineral surface area have been widely reported and are implicated in stabilization and long-term preservation of organic matter. However, the nature and stability of organomineral interactions and their connection with mineralogical composition have remained uncertain. In this study, we find that continentally derived organic matter of pedogenic origin is stripped from smectite mineral surfaces upon discharge, dispersal, and sedimentation in distal ocean settings. In contrast, organic matter sourced from ancient rocks that is tightly associated with mica and chlorite endures in the marine realm. These results imply that the persistence of continentally derived organic matter in ocean sediments is controlled to a first order by phyllosilicate mineralogy. [ABSTRACT FROM AUTHOR]

Kruger 2 is unique among Late Paleoindian sites of eastern Canada because of the presence of a potential hearth (feature #1) characterized by a concentration of blackened fire‐cracked rock and burnt bone embedded in a thick Ae horizon. Comparative mineralogical analysis (X‐ray diffraction) of Ae samples collected inside and outside the feature reveal the absence of calcite and apatite, two minerals commonly found in ashes, and the presence of smectite in the Ae inside feature #1. Smectite genesis is attributed to the weathering of mica and chlorite under geochemical conditions (high base cations, Si and pH; low Al) that are unique in time and space. We hypothesize that these conditions were created by the dissolution, 10,000 years ago, of a layer of hearth ashes resting on an incipient soil. Results confirm the intense weathering of mica and chlorite. We also show that ash dissolution could generate the conditions for smectite formation in the presence of altered mica and chlorite, allowing the development of a chronology explaining this finding. The data largely support our hypothesis and constitute a strong basis for future investigations on the links between hearth ash weathering and smectite genesis in acidic soils. [ABSTRACT FROM AUTHOR]

Lemon (Citrus limon), a species of the genus Citrus, is an economically significant crop and extensively cultivated in Iran, especially in Fars Province. Very little information is currently available on the changes in the different forms of soil potassium under the influence of lemon tree plantations or the associated mineralogical changes. The objective of this study was to investigate the status of different forms of K and the transformation of K-bearing minerals in the rhizosphere in lemon orchards of varying ages. Results demonstrated that the amounts of soluble, available, exchangeable, and nonexchangeable K in the control were higher than those in the lemon orchards of all the age range studied. The highest reduction in the different forms of soil K was measured for the 50-year-old orchard. The nonexchangeable K was significantly lower in the 20- and 50-year-old lemon orchards as compared with the control soil. Soil potassium concentration was observed to decrease with increasing soil depth. Our findings also indicated that vermiculitization of illitic clay minerals occurred due to both root potassium uptake and root activities in the rhizosphere of lemon trees. Shallower soil depths in the orchards were found to contain a higher illite content, while the vermiculite and interstratified I/S content increased with depth, except in the case of the 5-year-old orchard. Our findings also show that soils under lemon orchards of different ages exhibit differences in their K availability and, further, that vermiculitization might take place as a result of long-term cultivation despite the application of potassium fertilizers. [ABSTRACT FROM AUTHOR]

Niquelândia is a nickel-lateritic ore deposit located in the State of Goiás, Brazil. This deposit is one of the best-known nickel-lateritic orebodies in Brazil and contains both oxidized and silicate ores. In the oxidized ores, nickel is essentially associated with goethite, while in the silicate ores, it is associated with clay minerals, especially smectites. Two types of smectites were found: a nickel-magnesium-rich trioctahedral and an aluminium‑iron-rich dioctahedral structure. Nickel was produced at Niquelândia by the Caron process, a reduction roasting operation followed by ammoniacal leaching; however, due to the collapse of the nickel prices, Niquelândia mine interrupted its activities in 2016. Usually, the Caron process is able to extracts over 90% of Ni from the oxidized ore and less than 60-70% from the silicate ore. At Niquelândia the nickel recoveries varied from 70 to 75% of nickel from the Run of Mine (oxidized+silicate ores). A detailed study of the mineralogy from the silicate ore residues of the Caron process was conducted in order to find out why nickel extraction is not properly performed in this type of ore. The results revealed: 1) higher nickel extraction is assigned to iron-rich dioctahedral smectites and 2) lower nickel extraction is assigned to nickel-rich trioctahedral smectites; finally, 3) the low Fe content of Ni-rich trioctahedral smectites does not allow forming Ni-Fe phases which can be dissolved by the ammoniacal leaching. • In the silicate ore, nickel is associated with di and trioctahedral smectites. • Residues from roasting and ammoniacal leaching of Ni-silicate ore were studied. • Fe-Ni phases were not formed from roasted residues of trioctahedral smectite. • High Ni recovery was noted for Fe-rich dioctahedral smectites. [ABSTRACT FROM AUTHOR]

Abstract Although influence of organic matter (OM) on smectite illitization has received considerable attention in previous studies, the effect of different OM types on smectite illitization mechanism has rarely been examined. In the present study, hydrothermal experiments were conducted with N , N -dimethylhexadecylamine (16DMA)-smectite (M2) and lysine-smectite (M3) complexes to explore the effect of OM types on smectite illitization mechanisms. X-ray diffraction (XRD) analysis showed that mineral contents, illite percentage in mixed-layer illite-smectite (I% in I Sm), the average number of layers (N ave), and stacking mode of I Sm changed weakly at <300 °C while changed greatly at >300 °C. The changes varied obviously between M2 and M3 at >300 °C, indicating characteristics of solid-state transformation illitization mechanism in M2 and dissolution crystallization mechanism in M3. Moreover, the mid-infrared and thermo-XRD analyses indicated that the OM was mainly adsorbed in smectite interlayers at <300 °C, which delayed the exchange of K+ by interlayer cations and thus suppressed the smectite illitization. Above 300 °C, the OM was largely desorbed and the resulting changes of solution properties led to the acceleration of illitization and difference in illitization mechanisms in M2 and M3. The bulk mineralogy, element, and infrared analyses showed that illitization was accompanied by formation of new minerals and more minerals were formed in M2 than M3. The new minerals were further increased above 300 °C, especially the ankerite in M2. The binding mechanisms and strength varied in M2 and M3 because of differences in OM types, resulting in differences in bulk mineralogy evolution. This demonstrated the effect of organic-inorganic interactions on smectite illitization and mineral formation. The disparities in smectite illitization between M2 and M3, therefore, were linked to differences in mineral evolution of water-rock-OM systems with different OM types in natural environments. The insights obtained in the present study should be of high importance in understanding organic-inorganic interactions, hydrocarbon generation, and the carbon cycle. Highlights • Smectite illitization shows two-stage characteristics due to the release of OM • Illitization mechanisms varies under the influence of different OM • Cracking of OM enables the formation of ankerite which demonstrates the organic-inorganic interactions • Forming of new minerals during illitization is affected by the released OM [ABSTRACT FROM AUTHOR]

Abstract As an important geological archive, paleosols have been widely used in reconstruction of paleoenvironmental and paleoclimatic conditions. In this study, we undertook detailed analyses of the clay mineralogy and carbon and oxygen isotopic compositions of pedogenic carbonates in a series of 13 paleosol horizons within a fluvial section of the Eocene (~52–44 Ma) Lulehe Formation in the Qaidam Basin. Pedogenic smectite and illite/smectite (I/S) mixed-layer minerals are the predominant clay minerals in the paleosols, suggesting that the early Eocene paleoclimate of the Qaidam Basin was strongly seasonal with warm-wet summers. The high levels of pedogenic smectite production and high atmospheric p CO 2 reconstructed from soil carbonate nodule δ13C (mean −7.1 ± 0.8‰) are consistent with elevated temperatures during the Early Eocene Climatic Optimum (EECO). Coeval paleosol carbonate nodules yield estimated paleo-surface water compositions (δ18O psw) of −7.9‰ to −6.0‰ (VSMOW), which are significantly higher than the δ18O value of modern summer precipitation in the Qaidam Basin. The estimated temperature difference (~5.0 °C cooling) implies uplift of the study area by nearly 1000 m to its current average elevation of ~3000 m above sea level. This paleoelevation estimate agrees with modern meteoric water isotopes of Global Network of Isotopes in Precipitation (GNIP) sites in Asia in the same elevation range. Highlights • Multiple well-exposed paleosol horizons present in lower Eocene Lulehe Formation, Qaidam Basin, northern Tibetan Plateau. • These paleosols formed at 51.3–49.7 Ma during the Early Eocene Climatic Optimum (EECO). • Abundant pedogenic smectite indicates a strongly seasonal climate with warm-wet summers during early Eocene. • Soil nodule δ13C carb values (mean − 7.1 ± 0.8‰) reflect high atmospheric p CO 2 and elevated paleo-temperatures. • High paleo-precipitation δ18O psw values reflect low paleo-elevations (<2000 m) of Qaidam Basin in the early Eocene. [ABSTRACT FROM AUTHOR]

The adsorption of two pharmaceuticals, carbamazepine and paracetamol, onto the expandable clay mineral saponite has been studied through the combination of kinetic experiments, X-ray diffraction, and theoretical modeling. Kinetic experiments indicate low adsorption for carbamazepine and paracetamol on expandable smectite clay. Accordingly, X-ray diffraction experiments show that neither compound enters smectite interlayer space. Molecular dynamics simulations were carried out to understand the interactions between the two pharmaceuticals and the saponite basal surface in the presence of Na+ cations. Calculations reveal that paracetamol almost does not coordinate solution cations, whereas a rather low coordination to cation is observed for carbamazepine. As a result, the adsorption onto the clay surface results mainly from van der Waals interactions for both pharmaceuticals. Carbamazepine does adsorb the surface via two configurations, one involving cation coordination, which corresponds to a rather stable adsorption compared to paracetamol. This is confirmed by structural analyses completed with desorption free energy profile.

Mudstone samples from the Moreno (Upper Cretaceous-Paleocene) and Kreyenhagen (Eocene) formations are analysed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) to determine their mineralogy. Smectite (Reichweite R0) is the predominant phyllosilicate present, 48% to 71.7% bulk rock mineralogy (excluding carbonate cemented and highly bio siliceous samples) and 70% to 98% of the

In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (14C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments.

A series of clay minerals and clay-based materials have been tested to eliminate one of the most dangerous bacteria we can find in the water: Salmonella. It has been proven that the use of clays and their PCH materials can be a suitable method for removing Salmonella from water. The results of this initial study show that all the materials analyzed have great salmonella adsorption capacities ranging from the lowest value observed in the mont-PCH sample (0.29 × 1010 CFU g−1) to the highest value observed in the natural palygorskite sample (1.52 × 1010 CFU g−1). Macroporosity, accessible external surface area, and the presence of silanol groups in the external surface of the particles appears to be the controlling factors for Salmonella adsorption capacity while it seems that the structural characteristics of the clay minerals and their respective PCH does not affect the adsorption capacity.