bluuebunny/crossref_metadata_2025_split huggingface dataset:
An ideal solid solution model for calculating solubility of clay minerals
Authors: Tardy Y. , Fritz B. 
Published: December 2006

AbstractA method for estimating Gibbs free energies and stabilities of clay minerals is proposed for use with computer programs aimed at calculating the chemical evolution of natural water-rock systems. This is based on (i) a model for ideal solid solutions of a large number of end-member compositions and (ii) a data set of estimated solubility products from 36 end-members. The application of the method to the production of experimental or natural clay stabilities is discussed.
Dehydration-related proton conductivity in kaolinite
Authors: Maiti G.C. , Freund F. 
Published: December 2006

AbstractWell-crystallized kaolinite was found to exhibit marked proton conductivity at pre-dehydration temperatures. Direct current conductivity and thermopotential measurements were performed. By comparing the results obtained with Au electrodes (proton blocking) to those obtained with Pd electrodes (proton injecting), non-protonic contributions could be separated from proton conductivity. The majority charge carriers appeared to be defect proton (negative sign), corresponding chemically to an O2−replacing OH−in the lattice, but excess protons were also noted (positive sign). Below 275°C the activation energy was of the order of 7–8 kcal mole−1; between 275–450°C it was about 18–20 kcal mole−1. This indicated a two-step defect proton-excess proton conductivity mechanism involving, in succession, the two kinds of OH−in the kaolinite structure: (i) OH−located within the six-membered ring formed by the SiO4tetrahedral sheet, (ii) the close OH−array formed by the octahedral sheet. The conductivity results were supported by IR spectroscopic measurements.
The role of clay minerals in influencing porosity and permeability characteristics in the Bridport Sands of Wytch Farm, Dorset
Authors: Morris K. A. , Shepperd C. M. 
Published: December 2006

AbstractThe Bridport Sands is a widespread marine sandstone of Lower Jurassic age found in much of southern England. It is a very fine grained, moderately sorted quartz-arenite and is characterized by the alternation of friable and hard calcareous-cemented layers. The sands form the upper reservoir in the Wytch Farm Field, Dorset, which is currently producing at the rate of around 4000 barrels per day. Investigation of core material to assess the suitability of water injection for gas/oil recovery has shown that significant reductions of liquid permeability compared to air permeability occur. These reductions vary from 30% or less in the best quality reservoir to more than 70% in low-permeability sandstones. Clay minerals in the Bridport Sands comprise mainly kaolinite and mixed-layer clays of both the illite-chlorite and illite-smectite types. Small amounts of vermiculite and chlorite also occur. The kaolinite is found as loosely-attached, discrete particles, whilst the mixed-layer clays form patchy pore linings. The permeability reductions may be explained by: (i) the adsorption of water and expansion of poorly-crystalline mixed-layer illite-smectites causing blockage of pore space (this reduction is largely reversible) and (ii) the physical movement of authigenic kaolinite crystal aggregates blocking pore-throats (this reduction is largely non-reversible). The pore-size distribution, clay particle sizes, the distribution of the clays within the pore space, and the composition of the clays are all important factors in controlling porosity/permeability relationships and permeability reductions in the friable reservoir intervals in the Bridport Sands.
Significance of clays in the petroleum geology of the Niger Delta
Authors: Lambert-Aikhionbare D. O. , Shaw H. F. 
Published: December 2006

AbstractSediments of the Tertiary Akata and Agbada Formations have been studied by mineralogical and petrographic techniques. In the Akata and Agbada shales the clays are largely detrital, with only minimal alteration attributable to the effects of burial diagenesis. Clay minerals occur in minor (<10%) amounts in the reservoir sandstones of the Agbada Formation both as detrital and authigenic phases. There are significant differences between the clay assemblages of the water- and hydrocarbon-bearing sandstones. The latter have lower overall clay contents and authigenic kaolinite, whilst authigenic kaolinite and smectite are present in the water-saturated sandstones. These differences are thought to be related to the early migration of hydrocarbons into the reservoir sands. The causes of the poor degree of cementation in the Agbada sandstones are discussed along with the engineering problems posed by their very friable nature.
Presence d'imogolite dans la composition mineralogique des fractions fines extraites des croutes d'alteration observees sur le basalte de roudadou, pres d'Aurillac, Cantal
Authors: Torrent G. , Dejou J. , Manier M. , Larroque P. , Gibert J. P. 
Published: December 2006

ResumeLa composition minéralogique de la phase <2 µm de la croûte d'altération de teinte pâele et de quelques millimétres d'épaisseur, développée sur les faces des prismes basaltiques de Roudadou, près d'Aurillac, Cantal, a été étudiée par plusieurs techniques: RX, analyse thermique différentielle, thermogravimétrie, spectroscopie infra-rouge entre 600 et 200 cm−1, mesure des surfaces totales. Cette phase fine est constituée d'une fraction non cristalline relativement réduite et surtout de minéraux argileux cristallisés, parmi lesquels l'imogolite est largement dominante (50%), accompagnée de l'halloysite (30%). Parfois une smectite compléte ce cortège argileux. A notre connaissance, l'imogolite n'avait jamais été identifiée parmi les produits d'altération superficielle des roches volcaniques du Massif Central.
Observation of longitudinal acoustic phonons in layer-silicates by neutron inelastic scattering
Authors: Cebula D. J. , Owen M. C. , Skinner C. , Stirling W. G. , Thomas R. K. 
Published: December 2006

AbstractThe technique of neutron inelastic scattering has demonstrated the presence of longitudinal acoustic phonons in two layer-silicate minerals. Values of the elastic constants determined from the dispersion curves have established the validity of the technique for this class of materials.
Etude par spectroscopie infrarouge et diffraction X des interactions eau-cation-feuillet dans les phases a 14.6, 12.2 Et 10.1 Å D'une saponite-Li de synthese
Authors: Suquet H. , Prost R. , Pezerat H. 
Published: December 2006

ResumeLa prise en compte simultanée des résultats de diffraction des RX et de spectrométrie infrarouge a permis de préciser la nature des interactions entre l'eau, les cations compensateurs et les feuillets dans les phases à 14.6, 12.2 et 10.1 Å d'une saponite-Li de synthèse. En effet, la diffraction des RX renseigne sur l'espace interfeuillet disponible à l'eau et aux cations compensateurs alors que les perturbations observées sur les fréquences de vibration de valence des hydroxyles de structure apportent des indications sur la nature et la position des atomes situés à l'aplomb des cavités hexagonales. Cette étude a permis de confirmer la présence de cations hydratés (Li-H2O)+ dans les cavités ditrigonales des feuillets de la saponite-Li amené àun état d'hydratation correspondant à la phase à 10.1 Å.
A filtering device for oriented XRD mounts
Authors: Brusewitz Ann Marie 
Published: December 2006

In the laboratories of the Geological Survey of Sweden we have for many years used an acid-resistant, stainless steel filtering funnel to prepare ‘oriented’ clay mounts for X-ray diffractometry. The funnel consists of three parts (left and centre foreground of Fig. 1). The circular plate is porous and made of sintered stainless steel and serves as a support for a 47 mm diameter membrane filter. The cylinder is manufactured in two different sizes, 250 ml and 600 ml. The funnel is generally mounted on a suction flask but when the filtrate has to be analysed a suction cloche is preferable.When many mounts have to be prepared the use of a manifold is practical and time saving. We have adapted the Sartorius six-branch manifold and added a transition tube of stainless steel (right foreground of Fig. 1), threaded to fit the manifold outlet and tightened through a gasket. The funnel itself is mounted on the tube through a rubber stopper. Suction is by a small pump (25 l/min, 0·15 kW). A suction flask is placed between the filter stand and the pump to collect the combined filtrates (Fig. 2).
Reactions of ammonium sulphates with kaolinite and other silicate and oxide minerals
Authors: Bayer G. , Kahr G. , Mueller-Vonmoos M. 
Published: December 2006

AbstractInteractions of ammonium sulphates and various silicate and oxide minerals have been studied by X-ray heating methods and simultaneous TG-DTA. Kaolinite and other clay minerals were found to be very susceptible to these sulphating treatments, (NH4)3Al(SO4)3, (NH4)Al(SO4)2 and Al2(SO4)3 being formed successively with increasing temperature from 350 to ∼550°C. The same reaction products were obtained on heating mixtures of (NH4)2SO4 and γ-Al2O3, Al(OH)3 and bauxite. Fe-, Mg- and Ti-silicates and oxides gave NH4-double sulphates below 400°C and the corresponding metal sulphates above this temperature.
Phengitization, sericitization and potassium-beidellite in a hydrothermally-altered granite
Authors: Meunier A. , Velde B. 
Published: December 2006

AbstractX-ray diffraction, optical and microprobe studies of a kaolinized oligoclase—orthoclase—two-mica—granite (Southern Armorican Massif) indicated that low-temperature metasomatism had produced three series of minerals. 1. Partial alteration of muscovite resulted in the formation of ferrous-magnesium-phengite. Biotite was destabilized to a kaolinite-titanium oxide assemblage. 2. Phengite, unreacted muscovite and feldspars recrystallized to an aluminous, magnesian 1M sericite mineral ranging in composition from mica to illite. 3. Feldspars were entirely destabilized to produce the assemblage potassic-beidellite-kaolinite—Al-illite. Kaolinite was the predominant mineral in the most altered rock. A fourth stage of mineral equilibrium was also observed; this occurred after material from stage 3 had been reworked. In this environment, the potassic-beidellite was replaced by a calcic-montmorillonite. Potassic-beidellite was not stable under weathering conditions.
Utilisation du rayonnement synchrotron en diffusion aux petits angles pour l'etude du gonflement des smectites: II. Etude de différents systÈmes eau-smectites en fonction de la température
Authors: Pons C. H. , Rousseaux F. , Tchoubar D. 
Published: December 2006

RésuméLe mécanisme de dispersion dans l'eau d'une smectite a été étudié en fonction de 2 paramètres: la nature du cation interlamellaire, la nature du feuillet de smectite. Pour cela, on a observé l'évolution du diagramme de diffusion aux petits angles en fonction de la température (entre −15°C et la température ambiante) d'une série de dispersions contenant 20 g d'argile dans 100 g d'eau. La méhode d'interprétation des diagrammes est basée sur la comparaison entre courbes expérimentales et calculées. Les résultats obtenus montrent le rôle, dans l'aptitude au gonflement de la smectite, du cation interlamellaire, de la charge cu feuillet et de sa localisation. Ils montrent également quelles caractéristiques de la structure sont conservées entre la dispersion finale et le solide initial, ce qui permet d'en déduire le mécanisme de dispersion pour chaque smectite.
Cristallochimie des lizardites substituees Mg-Fe-Ni par spectrometrie visible et infrarouge proche
Authors: Cervelle B. D. , Maquet M. 
Published: December 2006

RésuméDes lizardites substituées (Mg,Fe,Ni)3Si2O5(OH)4 ont été étudiées par spectrométrie en réflectance diffuse de 340 à 2500 nm, de manière à déterminer l'environnement de Mg2+, Ni2+ et Fe2+, en particulier la symétrie des sites et les distances métal-ligands. L'examen de la structure de la lizardite sensu stricto ayant conduit à définir pour Mg2+ deux sites hexacoordonnés M1 et M2 non équivalents dans la couche octaédrique du feuillet serpentineux, l'interprétation, à l'aide de la théorie du champ cristallin, des spectres d'absorption de lizardites de compositions chimiques variées a fourni les résultats suivants: 1. Le site M1 a la symétrie C2v: octaèdre orthorhombique. 2. Le site M2 a la symérie C3v: octaèdre rhomboédrique. 3. Fe2+ est hexacoordonné, et occupe les deux sites M1 et M2 si sa teneur est supérieure à environ 2%. Pour une teneur inférieure, Fe2+ n'occupe que M1. 4. Dans une lizardite Mg + Fe + Ni, Ni2+ est hexacoordonné et occupe le site M2. Ce site du nickel est plus grand en présence de Fe2+, que lorsque le nickel y est seul (népouite). Ni2+ y occupe une position plus rapprochée du centre de la couche octaédrique que Mg2+, ce qui contribue à réduire la flexion du plan des cations dans cette couche. 5. Dans une lizardite proche du pôle nickelifère (népouite), il y a réorganisation de la structure autour d'un site hexacoordonné unique de symétrie C3v. Ce site est déformé, et plus petit: distance moyenne métal-ligand r = 2·06 Å dans la népouite, r = 2·11 Å dans la lizardite magnésienne sensu stricto. Cette réduction de la taille du site ne peut se concevoir que par la réduction de l'épaisseur de la couche octaédrique: 2·20 Å (pôle Mg) à 2·16 Å (pôle Ni).
Etude des echanges entre terres rares et cations interfoliaires de deux argiles
Authors: Bonnot-Courtois C. , Jaffrezic-Renault N. 
Published: December 2006

RésuméL'étude expérimentale de l'adsorption d'ions La3+ sur une smectite, successivement saturée en ions K+, Na+ puis Ca2+, montre que la stoechiomérie de l'échange s'effectue dans le rapport des charges des cations participant à la réaction. Dans un domaine de force ionique suffisamment restreint, l'échange a lieu dans les rapports suivants: 1 La3+ pour 3 Na+ ou 3 K+, et 1 La3+ pour 1·4 Ca2+. L'adsorption de toutes les terres rares sur la smectite et une illite s'effectue sans ségrégation notable dans cette famille d'éléments, les terres rares les plus lourdes étant un peu plus adsorbées que les terres rares légères. La désorption des terres rares est plus difficile, leur charge trivalente devant les stabiliser en position interfoliaire dans les minéraux argileux.
Etude thermodynamique des echanges d'ions entre gels silicates (A,B)O-SiO2-nH2O et solutions aqueuses (A2+B2+) d'elements de transition
Authors: Perruchot A. , Delbove F. 
Published: December 2006

ResumeOn étudie les équilibres de distribution de deux éléments de transition divalents A,B, entre gels silicatés inorganiques de formule SiO2-(A,B)O-nH2O et solutions aqueuses A2+,B2+(A.B = Mg, Mn, Ni, Co, Cu, Zn). On montre que l'enthalpie libre molaire standard d'échangede deux éléments A,B entre gel et solution est une fonction linéaire de l'enthalpie libre d'échangecalculée en considérant un échange théorique entre hydroxyde et solution. Les relations obtenues permettent de prévoir le comportement d'autres éléments divalents.
Quelques aspects de l'action des termites du sol sur les argiles
Authors: Boyer Ph. 
Published: December 2006

ResumeLa majorité des termites sont en rapport avec le sol et utilisent l'argile de ses horizons, pour édiffer leurs termitières. Pour les termites du sol, dont la plupart sont des maçons, l'argile est avant tout le matériau de base offrant les propriétés de rétention d'eau, de plasticité et d'ahésivité, leur permettant de confectionner les mortiers et les microbétons de leurs unités de constructions. Si les termites humivores absorbent toujours une quantité relativement importante d'éléments argileux avec leurs aliments, les termites lignivores n'ingérent qu'occasionnellement une fraction minime d'argile. Leur action sur l'évolution des silicates se traduit par des néoformations de minéraux argileux au sein de leurs constructions: illite ‘artificielle’, hydrobiotite, vermiculite, halloysite, montmorillonite, et parfoils sépiolite et attapulgite. Ces néoformations résultent de l'action conjugée du travail de broyage et de trituration salivaire de minéraux encore peu altérés de la profondeur du sol, et des conditions physico-chimiques de milieu particulières aux termites.
Crystallization of Fe(III)-Oxides from ferrihydrite in salt solutions: osmotic and specific ion effects
Authors: Torrent J. , Guzman R. 
Published: December 2006

AbstractFerrihydrite transformed to crystalline Fe(III)-oxides in salt solutions but the degree of transformation generally decreased with increasing concentration (decreasing water activity) and haematite was favoured over goethite. More transformation occurred for chloride than for nitrate or sulphate and more for calcium than for magnesium or sodium. Calcium and magnesium favoured haematite over goethite. The results support the hypothesis that haematite not only can be formed but will be favoured over goethite in natural environments with low water activity, for instance dry or saline soils or sediments. The ionic environment modifies the general water activity effect.
Relationships between chemical, physical and mineralogical characteristics of the Rupelian Boom Clay, Belgium
Authors: Decleer J. , Viaene W. , Vandenberghe N. 
Published: December 2006

AbstractThe Boom Clay is an important raw material for the Belgian structural clay products industry. It can be divided into several lithological sub-units. In order to obtain an insight in the parameters which characterize these different units, and which affect the overall properties of the clay, a detailed chemical, physical and mineralogical analysis was carried out. Pearson correlation coefficients were calculated between the variables, which were then placed in four correlation groups: a quartz/clay mineral group, a reducing component group, a carbonate group and a feldspar group. This treatment of the data allowed three analysis parameters to be selected: <2 µm fraction, organic carbon and CO2. The other variables could be calculated fairly accurately from these by means of regression lines.
Clay minerals as indicators of wind and current contribution to post-glacial sedimentation on the Azores/Iceland Ridge
Authors: Grousset F. , Latouche C. , Maillet N. 
Published: December 2006

AbstractClay mineral and trace element data indicate that sediments in the vicinity of the North Mid-Atlantic Ridge derive from material of both Icelandic and Canadian origin. These sources agree with the marine and atmospheric circulation patterns observed in this area.
Tarasovite, a mixed-layer illite-smectite which approaches an ordered 3:1 layer ratio
Authors: Brindley G. W. , Suzuki Tetsuya 
Published: December 2006

AbstractBasal X-ray peaks from normal and ethylene glycol-saturated tarasovite have been measured to 0.0.36 and 0.0.38, respectively; the mean basal spacings were 43·73 ± 0·44 and 46·05 ± 0·33 Å, withCVvalues of 1·31 and 0·97. The spacings indicate a near approach to a 3 : 1 illite-smectite but theCVvalues indicate a greater variability than is normally consistent with the allocation of a special name. Comparison of the observed spacings with those for illite showed that the more deviant values were always adjacent to positions of illite reflections. A modified Mering treatment of diffraction by mixed-layer sequences was used to estimate the proportion of illite layers; the average result was 79·9 ± 2·0%. The mineral is considered to have 3 : 1 illite-smectite units with randomly added illite layers, bringing the ratio from 75% for the ideally ordered sequence to near 80%.
Origin of bauxite at Eufaula, Alabama, USA
Authors: Lukas T. C. , Loughnan F. C. , Eades J. L. 
Published: December 2006

Abstract
An autochthonous origin for the bauxite deposits of the Eufaula district, south-eastern Alabama, appears to have received general acceptance but, compared with younger residual bauxites of the present day tropical regions of the world, the Eufaula deposits have a number of features that are difficult to reconcile with development in situ. In an attempt to resolve the enigma, a detailed study was undertaken of cores from three drill holes that intersected a complete succession through one of the Eufaula deposits. Although the results are not conclusive, it is believed that much of the observed phenomena can be explained on the basis of an essentially transported origin for the deposits.
Relationships between composition and structure in Fe-rich smectites
Authors: Brigatti Maria Franca 
Published: December 2006

Abstract
Chemical and crystallochemical properties of natural dioctahedral Fe-rich smectites formed by weathering of basaltic rocks in the Berici-Euganei Area, northern Italy, were investigated. It was found that: (i) the b-dimension could be correlated both to Fe3+/Σ ratio (Σ = octahedral occupancy) and to dehydroxylation peak temperature in the range 400–600°C; (ii) it is not correct to impose a total octahedral occupancy strictly equal to 2 for dioctahedral smectites; (iii) in the smectite group there is not a continuous isomorphous series as would appear on the basis of chemical features only.
NMR applied to minerals: IV. Local order in the octahedral sheet of micas: Fe-F avoidance
Authors: Sanz J. , Stone W. E. E. 
Published: December 2006

Abstract
A series of phlogopite and biotite samples were examined by wide-line NMR spectroscopy. Monitoring of the fluorine signal revealed the presence of homogeneous fluorine domains. The importance of these domains increased with increase in F and Fe contents. A model for the distribution of anions and cations in the octahedral sheet of micas is presented and discussed.
Water sorption on Ca-saturated clays: II. Internal and external surfaces of montmorillonite
Authors: Ormerod E. C. , Newman A. C. D. 
Published: December 2006

AbstractWater-sorption isotherms and interlamellar spacings were measured for Ca montmorillonite (from Redhill. UK) over the relative pressure range 1 >P/P0> 0. By taking account of the change in interlamellar volume with relative pressure, it is shown that internal and external surfaces can be calculated by a modifiedt-plot analysis. The results also show that sorption on the external surfaces of the montmorillonite is quantitatively similar to that on reference oxide surfaces. Desorption-sorption hysteresis occurred and was apparently caused by an ageing process in which the interlamellar volume increased at the expense of the external surfaces.
The properties and uses of clays which swell in organic solvents
Authors: Jones T. R. 
Published: December 2006

AbstractThe exchangable cations present on certain montmorillonites can be replaced by long-chain quarternary ammonium cations, and the resulting clays have the important property of being able to swell and disperse in a variety of organic solvents. Organophilic clays have a wide range of industrial applications and are, for example, important constituents of oil-well drilling fluids, paints, plastics and greases; their role in these is discussed. Organophilic clays have been extensively studied for about 50 years, but neither the structure nor the mechanisms by which they swell and disperse in organic solvents are clearly understood. An attempt is made to interpret the industrial applicatons in terms of published ideas concerning the structure and swelling properties of organophilic clays.
Montmorillonite catalysts for ethylene hydration
Authors: Atkins M. P. , Smith D. J. H. , Westlake D. J. 
Published: December 2006

AbstractIon-exchanged montmorillonites behave as solid acid catalysts and are effective and selective catalysts for the hydration of ethylene. The reaction proceeds predominantly in the interlamellar environment of the clay catalyst. Ethylene conversions were found to be markedly dependent on the choice of exchangeable cation, with Al being the best of those examined.