bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and swelling of fibrous and granular saponitic clay from Orrock Quarry, Fife, Scotland
Authors: Cowking A. , Wilson M. J. , Tait J. M. , Robertson R. H. S. 
Published: December 2006

AbstractVeins of intimately associated fibrous and granular saponitic clay occur in a basalt quarry at Orrock, Fife, Scotland. Preliminary X-ray diffraction studies suggested that both fibrous and granular forms consisted of pure saponite but chemical and thermal studies showed the presence of subsidiary amounts of interstratified chlorite. The fibrous clay, which is strongly oriented around the a axis but with a uniform distribution of the b and c poles, consists mainly of highly-crystalline laths with minor amounts of turbostratically-ordered particles. The granular clay consists of turbostratically-ordered particles only. The swelling behaviour of both types of clay in water and in ethylene glycol is similar to that of pure saponite. With glycerol, only the granular clay swells completely but the fibrous clay behaves similarly if first subjected to grinding or chemical pre-treatment. These observations are accounted for on the basis that the fibrous clay has better order than the granular form, thus enabling the interlamellar constituents to participate more fully in layer-to-layer bonding.
Relation entre le parametre b des smectites et leur contenu en fer et magnesium. Application a l'etude des sediments
Authors: Desprairies A. 
Published: December 2006

ResumeLe paramètrebdes smectites, à charge faible et empilement désordonné, est déterminé dans les diagrammes de diffraction X à partir des maxima d'intensité de la bande (06,33); ce paramètre montre une très bonne corrélation avec la teneur en fer et magnésium des feuillets. Les équations de régression proposées sont applicables à tous les échantillons renfermantune ou plusieursvariétés minéralogiques du groupe. La méthode semble particulièrement bien adaptée aux études des transformations chimiques des sédiments, au cours, par exemple, de leur diagénèse.
Proprietes de reflexion diffuse de pates de kaolinite en fonction de leur teneur en eau
Authors: Prost R. , King C. , D'hellencourt T. Lefebvre 
Published: December 2006

Resume
Le spectre de réflexion diffuse de pâtes de kaolinite obtenues pour des teneurs en eau croissantes a été étudié en séparant la part due au phénomène d'absorption de celle due à d'autres phénomènes comme la diffusion. On montre que l'intensité des bandes d'absorption varie linéairement avec la teneur en eau jusqu'à ce que le point d'entrée d'air dans le système soit atteint. Au-delà du point d'entrée d'air, quand le système est saturé en eau, l'intensité des bandes d'absorption semble tendre vers une limite. On montre de même que l'intensité réfléchie-diffusée en dehors des bandes d'absorption tend elle aussi vers une limite quand le système est saturé en eau. Il en résulte: (i) que la détermination des teneurs en eau à partir des données de réflexion diffuse est possible grâce à l'existence de courbes d'étalonnage linéaires dans le domaine d'hydratation pour lequel le système n'est pas saturé en eau, (ii) que l'analyse quantitative des données de réflexion diffuse est plus facile lorsque le milieu est saturé en eau. Les résultats obtenus montrent en outre que la relation générale proposée par P. F. Low: J = J0
eα/θ;
où où J est une propriété de l'eau associée avec l'argile, J
0 une même propriété pour l'eau liquide, θ; la teneur en eau et α un coefficient, ne s'applique que sur un domaine limité de teneurs en eau.
Genesis of bentonites from Cabo de Gata, Almeria, Spain: a stable isotope study
Authors: Leone G. , Reyes E. , Cortecci G. , Pochini A. , Linares J. 
Published: December 2006

AbstractOxygen (18O/16O) and hydrogen (2H/1H) isotopic ratios were measured on 22 smectite separates from bentonite deposits of the Sierra de Gata and Serrata de Nijar, Almeria, Spain. In addition, 18O/16O and 2H/1H ratios were determined on some waters from springs and wells, and 18O/16O ratios were measured on quartz, plagioclase and biotite samples separated from the bentonites. The smectites displayed two distinct isotopic compositional groups which excluded an origin either by submarine alteration or weathering under normal surface conditions of the associated volcanic rocks. Bentonization processes caused by low-temperature fluids of meteoric origin could account for the stable isotopic contents. Argillization temperatures are estimated at ∼40°C and ∼70°C for the Serrata de Nijar and the Sierra de Gata deposits, respectively.
The nature and origin of authigenic smectites in some recent marine sediments
Authors: Cole T. G. , Shaw H. F. 
Published: December 2006

AbstractThree principal modes of formation are apparent for authigenic smectites in Recent marine sediments: alteration of volcanic rocks and glass, low-temperature combination of biogenic silica and Fe-oxyhydroxides, and direct precipitation from hydrothermal fluids. The latter two mechanisms are discussed with reference to new evidence from studies of sediments from the Bauer Deep of the equatorial eastern Pacific and the Atlantis II Deep in the Red Sea. In the Atlantis II Deep sediments, three sub-environments of smectite formation from hydrothermal fluids are recognized. In two of them nontronites are formed, whilst in the third an Fe-poor smectite, intermediate in composition between beidellite and montmorillonite, occurs.
Sorption and transformation of phenols on clay surfaces: effect of exchangeable cations
Authors: Isaacson P. J. , Sawhney B. L. 
Published: December 2006

AbstractThe sorption and transformation of phenol, 2-methylphenol, 3-methylphenol, 2,6-dimethylphenol, 3,5-dimethylphenol, and 2,4,6-trimethylphenol, by homoionic Na-, H-, Ca-, Cu-, Al-, and Fe(III)-montmorillonite from both vapour and aqueous phases were examined by IR spectroscopy. All the phenols were sorbed by the clays but were modified to different degrees depending on the exchangeable cations and on the amount and type of alkyl substitution of the phenols. Sorption of 2,6-dimethylphenol from aqueous solution was irreversible, and the extent of sorption followed the order Fe- > Al- > Cu- > Ca-clay. Both transition and non-transition metal cations were effective in transforming the phenol sorbates and heating the clay/phenol complexes further enhanced transformation. The results are discussed in terms of the nature of the transformation products and the likely role of radical reactions in their formation.
Evolution des biotites en fonction des conditions d'oxydo-reduction du milieu
Authors: Vicente-Hernandez J. , Vicente M. A. , Robert M. , Goodman B A. 
Published: December 2006

ResumeDes études expérimentales sont réalisées afin de préciser les relations entre la vermiculitisation des biotites (ouverture par NaCl N) et les phénomènes d'oxydation (par l'eau ou par H2O2). Les évolutions sont suivies par diffraction des rayons X et en spectroscopie d'absorption infra-rouge; l'oxydation du fer est appréciée sur l'échantillon par spectroscopie Mössbauer. Les résultats montrent que si une certaine oxydation accompagne normalement la vermiculitisation, une oxydation intense provoque une expulsion de fer et la formation de vermiculite hydroxy ferrique.
The influence of aluminium substitution and crystallinity on the Mössbauer spectra of goethite
Authors: Murad E. , Schwertmann U. 
Published: December 2006

AbstractBoth aluminium substitution and poor crystallinity reduce the magnetic hyperfine field of goethite. Mössbauer spectra taken at 4·2 K show that the effect of poor crystallinity is similar to that of Al substitution, i.e. it reduces the saturation hyperfine field. A multiple correlation was found to exist between the magnetic hyperfine field at 4·2 K as a dependent variable vs Al substitution and crystallinity as independent variables. If a hyperfine field is to be interpreted with respect to either Al substitution or crystallinity, it is therefore necessary to have knowledge of the other variable.
The characterization of clay-organic systems
Authors: Tennakoon D. T. B. , Schlögl R. , Rayment T. , Klinowski J. , Jones W. , Thomas J. M. 
Published: December 2006

AbstractThe importance of a number of techniques (including1H and13C NMR, XRD and IR) in exploring the important catalytic properties of synthetic and natural clays is described. A clear distinction is observed between proven catalytically-active clays (e.g. Al-exchanged) and those which are generally less effective (e.g. Na-exchanged).13C NMR spectroscopy is used to identify directly products formed within the interlayer regions, and temperature-controlled powder XRD serves as a useful tool for identifying whether or not intercalation occurs under variously defined conditions. High-pressure XRD is used to verify the formation of different products during reaction.
Smectite-polymer interactions in aqueous systems
Authors: Burchill S. , Hall P. L. , Harrison R. , Hayes M. H. B. , Langford J. I. , Livingston W. R. , Smedley R. J. , Ross D. K. , Tuck J. J. 
Published: December 2006

AbstractNeutron scattering studies have indicated that the non-coordinated water at smectite surfaces has a similar mobility to that of bulk water, but that the water coordinated to the cations is immobile on the time scale of the neutron measurements. Thus hydrophylic polymers can readily displace the non-coordinated water and bind to the silicate surface, and to the exchangeable cations through a water-bridge mechanism. Poly(ethylene oxide) molecules with molecular weights up to 4000 appear to be bound to Na-montmorillonite in flattened conformations at the clay surface. Poly(vinyl alcohol) is extensively bound by Na-montmorillonite and by Na-Laponite (a synthetic hectorite-like clay); as binding progresses fewer molecule segments can contact the surface and so at the higher levels of adsorption extensive loops of polymer extend away from the silicate surface. Some polyanions provide good protection for smectites against flocculation with salt. The abilities of such polymers to protect the clays is dependent both on the extents of the charges and on the solution conformations which these polymers can assume.
Synthetic imogolite: properties, synthesis and possible applications
Authors: Farmer V. C. , Adams M. J. , Fraser A. R. , Palmieri F. 
Published: December 2006

AbstractThe unique properties of imogolite are closely related to its structure, which is a tube of 23–27 Å outer diameter and ∼10 Å inner diameter, with an AIOH outer surface and SiOH inner surface. Acid dispersions contain the long, positively-charged tubes as isolated units or small bundles, which form bulky gels in alkali, and flocculate with negatively-charged colloids, polyvalent anions, and long-chain anionic detergents. Sorption properties are associated with the 10 Å intra-tube pores and with inter-tube channels of variable dimensions. Surface acidity is less than that of layer-silicate clays. The chemical and mechanical stability, biological activity, film- and fibre-forming characteristics, and conditions of synthesis are reviewed, on the basis of both new and published findings. Areas of potential application are indicated.
Kaolinites ferriferes et oxy-hydroxydes de fer et d'alumine dans les bauxites des Canonnettes (S.E. de la France)
Authors: Cantinolle P. , Didier P. , Meunier J. D. , Parron C. , Guendon J. L. , Bocquier G. , Nahon D. 
Published: December 2006

ResumeL'analyse par diffraction des rayons X, résonance paramagnétique électronique et par spectrométrie infra-rouge des constituants minéraux du profil des Canonnettes (Sud-Est de la France) permet de montrer que les kaolinites sont ferrifères. De plus, au fur et à mesure du développement et de l'accumulation des oxy-hydroxydes de fer et d'alumine dans le profil, on note l'enrichissement progressif des kaolinites en fer en même temps qu'augmente leur désordre et que les taux de substitution en moles % d'AlOOH des goethites alumineuses devient plus important. Finalement, les kaolinites disparaissent remplacées par les oxy-hydroxydes de fer et d'aluminium, là ou leur accumulation est maximum.
Ferrous-iron-bearing vermiculite-smectite series formed during alteration of chlorite to kaolinite, Otago Schist, New Zealand
Authors: Craw D. 
Published: December 2006

AbstractInterlayered (<20 µm scale) vermiculite-smectite minerals were found in drill-cores from altered Otago schist basement up to 2 m from the contact with the overlying sediment. Mineral compositions defined a series from Fe2+-rich trioctahedral vermiculite to Fe2+-bearing dioctahedral smectite; in these, tetrahedral substitution of Al for Si was unusually high (up to 3·3/8 in the formula unit). The minerals formed as intermediates during the alteration of chlorite to kaolinite under non-oxidizing, possibly acid conditions. The source of the altering solutions may have been overlying lignite seams.
Comportement des ions aluminiques et de la silice en solution: Etude de la formation de la kaolinite
Authors: Espiau P. , Pedro G. 
Published: December 2006

ResumeL'intérêt porté à la synthèse de la kaolinite a été suscité par des préoccupations d'ordre pédologique, qui nous ont amenés à comparer les expériences réalisées en laboratoire aux situations naturelles considérées comme propices à la formation de la phyllite 1/1. Il apparaît essentiel, pour le succès des synthèses, de privilégier la formation d'ions hydroxylés monomères de Al, pouvant réagir avec l'acide orthosilicique. La neutralisation lente et partielle de solutions très diluées semble garantir ces conditions. Deux séries d'essais ont été entrepris. Les résultats expérimentaux tendent à démontrer la possibilité d'obtenir une précipitation de kaolinite à partir des ions en solution et par simple neutralisation. Le mécanisme proposé par Siffert (1962), mettant en jeu la formation d'éléments T-O, semble le plus probable. Ces éléments prendraient naissance par réaction de l'acide orthosilicique et de l'ion Al(OH)2+. Le rapprochement entre l'importance du rôle joué ici par ce monomère hydroxylé et la place qu'il occupe dans le schéma de dissolution établi par Sarazin (1979) peut permettre de comprendre que les néoformations de kaolinite correspondent à des sols relativement bien drainés.
The significance of clay minerals in studies of the evolution of the jurassic deposits of the Betic Cordillera, SE Spain
Authors: Delgado I. Palomo , Huertas M. Ortega , Hach-Ali P. Fenoll 
Published: December 2006

AbstractA detailed study of the mineralogy of the Jurassic detrital sediments of the Betic Cordillera (SE Spain) was needed to resolve problems relating to the environment of deposition. The choice of the marly limestone and marl facies for such a study was appropriate, because these are well represented throughout the Cordillera and consist of the earliest materials deposited after the break-down of the Liassic carbonate platform. Quantitative mineralogical analyses and crystallochemical studies enabled the source area to be defined, as well as indicating the likely erosion and weathering processes undergone by the minerals during transport and deposition, and the degree of diagenesis. Four mineral associations were distinguished, permitting a temporal and spatial analysis of the environment of deposition, and the relationship between its mineralogy and the different lithological facies.
Physico-chemical characterization of Cu2+-exchanged sepiolite
Authors: Corma A. , Pérez-Pariente J. , Soria J. 
Published: December 2006

AbstractCopper-sepiolites exchanged at different levels have been studied by ESR, IR, and TG. The results indicate that in the unheated samples the Cu2+ ions are located in octahedral edge positions. After dehydration, the Cu2+ ions occur in two positions with different environments. Some of the Cu2+ ions lose the two molecules of coordinated water in one step, at low dehydration temperatures, and adopt a square pyramidal geometry. Other Cu2+ ions lose the coordination water in two steps, at lower temperature than the natural sepiolite, and adopt a tetrahedral symmetry.
29Si- and27Al-MAS/NMR study of the thermal transformations of kaolinite
Authors: Watanabe T. , Shimizu H. , Nagasawa K. , Masuda A. , Saito H. 
Published: December 2006

AbstractThermal transformations of kaolinite were studied by29Si- and27Al-MAS/NMR and ESR techniques. In metakaolin, Si is still dominantly in theQ3state (three Si atoms bonded to an Si-O4tetrahedron) and Al detectable by NMR is in both 4-coordination and 6-coordination. Coordination polyhedra around Al or Fe replacing Al are much distorted. Metakaolin crystallizes into γ-alumina and mullite exothermically at ∼980°C, this crystallization being preceded by a faint endothermic reaction. The latter is due to segregation of SiO2and Al2O3, which results in an increase of Si in theQ4state and an increase of 6-coordinated Al2O3.
Simulation of soil reactions: aluminium-iron(III) hydroxy species react with silica to give deposits on particle surfaces
Authors: Taylor R. M. , Raupach M. , Chartres C. J. 
Published: December 2006

AbstractIn solutions of three different, stable, Al-Fe(III) hydroxy species, reaction with silica particles for one month decreased the solution pH and gave deposits containing Fe, Al and Si over the surfaces of the particles, joining them together. Infrared difference spectroscopy showed the deposits to be similar to imogolite or feldspathoid phases, depending on the composition of the initial solution. Comparative SEM and EDXA elemental analysis profiles supported the conclusion that these laboratory products were similar to naturally occurring soil cementing agents. An explanation is given for the observed reactions and the formation of materials likely to act as cementing agents in soil.
27Al Satellite Transition MAS-NMR Spectroscopy of Kaolinite
Authors: Rocha J. , Pedrosa De Jesus J. D. 
Published: December 2006

AbstractHighly crystalline kaolinite has been studied by 27Al satellite transition magic angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. This technique provides an additional narrowing of the MAS spectral lines by a factor of more than three compared with the width of the prominent central transition. Evidence for the presence of two crystallographically inequivalent hexacoordinated Al sites has been found. The results support the kaolinite crystal structure proposed by Bish & Von Dreele (1989).
Fluid composition, mineralogy and morphological changes associated with the smectite-to-illite reaction: an experimental investigation of the effect of organic acid anions
Authors: Small J. S. 
Published: December 2006

AbstractThe smectite-to-illite reaction (illitization) was examined in a dilute suspension of Wyoming bentonite in the presence of oxalate and acetate. Experiments were performed using fluidsampling apparatus at 200°C, 50 MPa, in which progressive changes in both clay mineralogy and fluid composition were monitored. The presence of K-oxalate and K-acetate under neutral-alkaline conditions produced significant reaction of smectite to either R1 or R2 ordered illite-smectite with 60–70% illite layers. Experiments at the same temperature with KCl, or oxalic acid plus KCl, produced no reaction. Fluid chemistry showed that K-oxalate and K-acetate resulted in the establishment of aK+/aH+ conditions within the muscovite stability field, favouring the formation of illite. The extent of dissolution and precipitation indicated by fluid data is insufficient to account for the amount of illitization evident in the mineralogy. This implies that a localized dissolution-precipitation process occurs, perhaps on the scale of a single clay particle. These experiments highlight the importance of pH as a control over illitization and show that organic anions can buffer fluid composition into the optimum aK+/aH+ condition for illitization. These findings are highly significant for the smectite-to-illite reaction occurring in organic bearing sediments where organic acid anions are generated during kerogen maturation.
Micropore formation in heated synthetic Al-goethites from a ferrous system
Authors: Ruan H. D. , Gilkes R. J. 
Published: December 2006

AbstractNitrogen adsorption and desorption isotherms were obtained for microcrystalline, platy crystals of synthetic Al-substituted goethites synthesized from the ferrous system and heated to 260°C. Specific surface area, cumulative pore area and frequency of mesopore wall-separations of 2–15 nm in size increased as Al substitution increased. Nanometre-size micropores developed at heating temperatures between 200 and 240°C and decreased during the growth of hematite crystals between 240 and 260°C. Aluminium substitution had little effect on micropore development and a moderate effect on mesopore development. The increases in micropore volume and specific surface area due to heating are much smaller than is reported in the literature for large, lath-like crystals of goethite that develop abundant slit-shaped micropores.
Effects of hydrothermal activity on clay mineral diagenesis in Miocene shales and sandstones from the Ulleung (Tsushima) back-arc basin, East Sea (Sea of Japan), Korea
Authors: Hillier S. , Son B. K. , Velde B. 
Published: December 2006

AbstractClay mineral assemblages in both shales and sandstones of Miocene age have been studied in a well from the Ulleung Basin, a back-arc basin in the East Sea. Samples were examined from burial depths of ~800 to 3000 m. At the shallowest depths the shales contain assemblages dominated by R0 mixed-layer illite-smectite (I-S) together with illite, kaolinite and minor chlorite. The sandstones also contain I-S, but are dominated by large amounts of authigenic kaolinite. In both shales and sandstones I-S becomes R1 ordered at ~ 1000 m depth and at 2000 m depth, and deeper, I-S expandabilities are <20%. At ~ 2400 m depth, kaolinite in the sandstones is replaced by abundant Li-tosudite, indicating that clay mineral diagenesis has been affected by a hydrothermal episode. Furthermore, organic maturity data indicate that much of the succession has experienced considerably higher temperatures in the past. Vitrinite reflectance data are best modelled by a short lived (0.1–0.01 Ma) heating event in the Pliocene. This suggests that the shallow depths over which the smectite to illite reaction is completed and the extensive kaolinitization of the Miocene sandstones may also be related to the hydrothermal event.
Palygorskite occurrences in the Portuguese sector of the Tagus basin: a preliminary report
Authors: Dias I. , Gonzalez I. , Prates S. , Galan E. 
Published: December 2006

Palygorskite and sepiolite occurrences and deposits are frequent in the Iberian Peninsula, mainly in the Tagus basin, in central Spain and Portugal (Galán & Castillo, 1984).In Portugal, the first palygorskite occurrence was reported by Carvalho (1964) in the region of Ponte do Sor, Tagus basin, in Paleogene sediments. Later, Carvalho (1968) reported palygorskite occurrences in coarse detrital sediments that were occasionally carbonatic or hardened by silicification, and built up the Cenozoic base for the Tagus and Sado basins. Carvalho referred to such formations as the 'Attapulgite complex'. Overlying this attapulgite complex is the 'Montmorillonite complex', probably of Miocene age.