bluuebunny/crossref_metadata_2025_split huggingface dataset:
Le césium, revelateur de structure des smectites
Authors: Besson G. , Glaeser R. , Tchoubar C. 
Published: December 2006

ResuméEn utilisant des méthodes diffractométriques avec des smectites mal cristallisées, il n'est pas possible de déterminer de façon précise la répartition des atomes dans le feuillet. Il est particulièrement difficile de confirmer si le mineral est di- ou trioctaédrique, ou de déterminer la position de la vacance (position cis ou trans) dans la couche octaédrique. De même la nature polytypique de ces minéraux est difficile à preciser. La détermination de ces paramètres est difficile car les modulations (hkl) obtenues par diffraction des rayons X avec les smectites sont faibles et très peu marquées. Ce travail montre qu'en utilisant le césium comme cation interfoliaire, il y a non seulement augmentation de l'ordre dans l'empilement des feuillets mais aussi que son grand facteur de diffusion augmente l'intensité des modulations (hkl). En supposant que la substitution par du césium ne modifie pas la répartition des atomes dans le feuillet (il affecte seulement la distorsion de la couche tétraédrique), il est alors possible de déterminer cette répartition.
The in Vitro cytotoxicity of some standard clay mineral dusts in the respirable size range
Authors: Gormley I. P. , Addison J. 
Published: December 2006

Abstract
Seven natural clay minerals (two kaolinites, three montmorillonites, a hectorite and a palygorskite) were tested for their cytotoxicity in vitro using an established cytotoxicity assay. Cellular viability, levels of lactate dehydrogenase, N-acetyl-β-d-glucosaminidase, lactic acid and total cellular protein were measured in cells of the macrophage-like cell line, P388D1, after 48 h incubation with each clay. There was a significant relationship between BET/N2 surface area of the clays and cytotoxicity but in two cases the level of cytotoxicity was apparently influenced by the presence of quartz or cristobalite in the samples. Results are discussed in the light of the available animal and epidemiological data relating to clay minerals.
‘Corrensite-like minerals’ in the Taro and Ceno Valleys, Italy
Authors: Brigatti M. F. , Poppi L. 
Published: December 2006

AbstractMineralogical properties (XRD, DTG) and chemical compositions of some chlorite-smectite interlayer minerals in alteration products of ophiolitic rocks from the Northern Apennines are presented and discussed. The presence of iron hydroxides and the continuous variation in Al2O3 content suggest that the corrensites are intermediate stages in the process of alteration of chlorite to smectite in an environment characterized by high element mobility. A thermal test to characterize the swelling component of the interlayer species is proposed.
Interstratified XRD characteristics of physical mixtures of elementary clay particles
Authors: Nadeau P. H. , Tait J. M. , McHardy W. J. , Wilson M. J. 
Published: December 2006

AbstractTransmission electron microscopic (TEM) examination of the <0·1-µm fraction of montmorillonite and regularly interstratified illite-smectite (I-S) shows that these clays, when dried from suspension, consist primarily of particles 10 Å and 20 Å thick respectively. However, X-ray diffraction (XRD) examination of sedimented aggregates of montmorillonite indicate that the effective number of unit cells that are diffracting coherently is ∼9. This discrepancy can be reconciled by postulating an interparticle diffraction effect from the sedimented aggregates of oriented particles. The interfaces of these particles are capable of adsorbing water, ethylene glycol etc. so that on this basis smectite is composed of elementary silicate particles 10 Å thick, and regularly interstratified I-S is primarily composed of elementary ‘illite’ particles 20 Å thick, values which are in agreement with the TEM observations. This concept is confirmed experimentally by XRD examination of sedimented aggregates from mixed suspensions of both materials; the resulting patterns are identical to those of randomly interstratified illite and smectite layers, which indicates that the layer sequence examined by XRD has been entirely rearranged. It is concluded that the use of XRD peak breadth to determine mean crystal thickness cannot be reliably applied to these systems. Standard XRD data from sedimented aggregates may not be able to distinguish between true interstratification and interparticle diffraction effects of intimate physical mixtures.
The distribution of octahedral cations in the 2:1 layers of dioctahedral smectites studied by oblique-texture electron diffraction
Authors: Tsipursky S. I. , Drits V. A. 
Published: December 2006

AbstractOlique-texture electron diffraction examination of K-saturated dioctahedral smectites after 70–100 wetting-drying cycles allows the determination of cation distribution betweentransandcisoctahedra of the 2:1 layers. Studies of smectites with different compositions has revealed a wide variety of occupancies of the available octahedral sites.
29Si and 27Al nuclear magnetic resonance spectroscopy of 2:1 clay minerals
Authors: Thompson J. G. 
Published: December 2006

AbstractSolid-state 29Si and 27Al NMR spectroscopy with magic-angle spinning was used to study two smectites, two illites and a vermiculite. 27Al NMR was able to directly observe the coordination of aluminium. 29Si NMR was sensitive to both the chemical nature of the interlayer species and the presence of aluminium in the tetrahedral sheet. Well-resolved resonances in the vermiculite at δ = −84·6, −88·7 and −92·9 (ppm relative to TMS) were assigned to Q3(2Al), Q3(1Al) and Q3(0Al) respectively. The smectites exhibited single resonances centred at δ = −93 (Q3(0Al)). The illites displayed broad resonances between δ = −80 and −105. The 29Si spectrum of a smectite complexed with alkylammonium cations showed a shielding of up to 1 ppm relative to the untreated sample.
Electron microprobe analysis of clay minerals
Authors: Velde B. 
Published: December 2006

The electron microprobe has been used in petrographic research for almost 20 years and more recently as a tool for investigations of clay minerals. However, to the author's knowledge no information has been published concerning the reliability of such analyses―especially those of the alkali elements. Since the alkali contents of clays are often critical, e.g. in determining the smectite content of mixed-layered minerals, it is important to have some idea of the reliability of an analysis made using an electron microprobe.Three variables can be controlled in electron microprobe analysis—time, beam-current intensity and beam size (the diameter of the beam which excites the sample). Exaggerated conditions of any one of these variables tend to diminish the signal received by the detectors for the alkali elements, especially sodium. As an example, the effect of varying two of these parameters on the intensity of sodium radiation for sodium-aluminumsilicon glass is shown in Fig. 1. The signal decreases (% loss Na) over a 200 s counting time. Beam intensity and beam diameter were varied in this example.
Organic reactions as indicators of the burial and temperature histories of sedimentary sequences
Authors: Mackenzie A. S. 
Published: December 2006

AbstractThree organic reactions which affect individual compounds present in most organic-rich sedimentary rocks have been identified—configurational isomerization and aromatization of steroid hydrocarbons, and configurational isomerization of hopanes. The extents to which these reactions have occurred can be assessed by gas chromatographic-mass spectrometric analysis of the organic extracts of the sediment samples; they provide sensitive indicators of thermal maturation. When combined with the model of sedimentary basin formation by extension of the lithosphere, this molecular approach to the maturation of organic material can be used to constrain the temperature-time histories of sedimentary sequences. This temperature history may be used to integrate the relevant Arrhenius’ and rate equations governing the reaction rates. Each rate equation has three constants—the activation energy, frequency factor and the ratio of forward reaction to backward reaction. These have been estimated using analyses of samples whose temperature-time history is well constrained. The resulting estimates can then be used to reconstruct the temperature-time histories of other samples from organic geochemical data, e.g. calculation of the amount and timing of uplift.
Stability of detrital heavy minerals in Tertiary sandstones from the North Sea Basin
Authors: Morton A. C. 
Published: December 2006

AbstractIntrastratal solution of detrital heavy minerals in North Sea Tertiary sandstones takes place in two different diagenetic settings, deep burial and acidic weathering. These are characterized by different orders of mineral stability: apatite, chloritoid, garnet, sphene and spinel are less stable in acidic weathering than in deep burial, whereas the reverse is true for andalusite, kyanite and sillimanite. Heavy-mineral dissolution patterns, therefore, do not follow one single order of stability but several, depending on the diagenetic environment in which the dissolution occurs. It seems from this that the relativeorder of stabilityfor detrital heavy minerals is controlled by the chemistry of the interstitial waters, whereas thelimits of persistencedepend on pore-fluid temperature, rate of water throughput, and geological age. Because different diagenetic environments lead to differing orders of mineral stability, it may prove possible to elucidate certain aspects of the diagenetic history of a sandstone by heavy-mineral dissolution patterns.
Quartz diagenesis and convective fluid movement: Beatrice Oilfield, UK North Sea
Authors: Haszeldine R. S. , Samson I. M. , Cornford C. 
Published: December 2006

AbstractThe extent of diagenesis in Lower Jurassic shoreline sandstones of the Beatrice oilfield was controlled primarily by their detrital clay content. Sandstones rich in detrital clay had low depositional permeabilities; these show preservation of detrital feldspars to the present day and have no extensive diagenetic quartz overgrowths. Sandstones poor in detrital clay had high permeabilities and show large quartz overgrowths as part of a normal sub-arkosic diagenetic sequence. Such quartz occurs preferentially below, but not above, impermeable mudstones. These low- and high-permeability features suggest that pore-fluid flow was important during diagenesis. Fluid inclusions trapped in diagenetic quartz overgrowths formed between 68° and 94°C. This silica was probably supplied in solution from the temperature-driven illitization of smectitic clays surrounding these sandstones deeper in the basin. Fluid volumes from clay dewatering, from mechanical compaction, or from influx of overlying seawater were too small to transport diagenetic silica volumes. Silica-rich fluids were probably transported up-dip by convective cells within the sandstones and authigenic quartz precipitated as these fluids cooled. This episode of quartz diagenesis could have been completed within 1·6 × 106 yr if fluid velocities were 3·1 m/yr. Similar convective fluid flows could have transported the fluids responsible for secondary porosity development and the hydrocarbons expelled from mudstones later in the basin burial history.
Volcaniclastics as potential hydrocarbon reservoirs
Authors: Seemann U. , Scherer M. 
Published: December 2006

AbstractVolcaniclastics have not as yet been considered prime hydrocarbon exploration targets. This is because they contain a high proportion of mechanically and mineralogically unstable components which generally cause a faster deterioration in reservoir quality upon burial than is found in siliciclastics. Also, their complex mineralogical composition makes the burial-related diagenesis more difficult to understand. However, under favourable circumstances—such as devitrification at shallow depth, leaching of unstable particles, fracturing, or reworking—volcaniclastics may act as good reservoir rocks. Both favourable and unfavourable case histories are discussed.
Diffraction effects calculated for structural models of K-saturated montmorillonite containing different types of defects
Authors: Rits V. A. D. , Plançon A. , Sakharov B. A. , Besson G. , Tsipursky S. I. , Tchoubar C. 
Published: December 2006

AbstractThe general approach to the problem of the real structure of smectites requires an analysis based on the relationship between structural characteristics and diffraction patterns. This paper, which considers only the models corresponding to dioctahedral smectites saturated by K-cations and collapsed, includes: 1. Successive consideration of all models which are crystallochemically possible. These models may differ in (i) the structure and chemical composition of layers and interlayer spaces; (ii) the azimuthal orientations, translations and the mode of alternation of the layers; (iii) independent parameters which describe quantitatively the models (e.g. abundance of each type of layer, probability parameters defining the succession of layers, …). 2. Calculation, in all accessible domains of reciprocal space, of the distribution of intensities and profile variations, obtained by changing only one parameter at a time, that defines one type of structural feature (e.g. cation distribution in individual layers, stacking of the layers, nature of stacking faults, …). 3. A systematical analysis of the calculated diffraction patterns to establish the diffraction criteria which will help to interpret the experimental data explicitly.
The rapid formation of crystalline double hydroxy salts and other compounds by controlled hydrolysis
Authors: Taylor R. M. 
Published: December 2006

AbstractDouble-cation hydroxy compounds, generally with the pyroaurite-type structure, were synthesized by a reaction involving the hydrolysis of a cation in solution by a fully hydrolysed and precipitated hydroxide of a second metallic cation. Synthesis of this type of compound is not limited to reactions between di- and trivalent cations as previously thought but can, in this process, involve divalent-divalent, divalent-tetravalent and trivalent-trivalent cations. Crystalline compounds with reasonably sharp XRD patterns formed generally within a few hours at 25°C at pH 4–8·5 depending on the cations involved. The technique presents a more rapid method of formation of these compounds than previously described syntheses, and has been called induced hydrolysis because the fully hydrolysed cation causes complete hydrolysis of the second cation at a pH below that at which this would normally occur. The minerals takovite, Ni6Al2(OH)16CO3·H2O, and hydrotalcite, Mg6Al2(OH)16CO3·H2O, were amongst some of the compounds formed and the reaction is considered to be more realistic in terms of conditions encountered in natural environments than previous syntheses. The reactions described could also be expected to affect the mobility of heavy elements in the environment. These double hydroxy compounds convert on heating between 300–500°C to double-metal oxides with the spinel structure.
Etude par spectrographie infrarouge d'un encroutement calcaire sous galet. Mise en evidence et modelisation experimentale d'une suite minerale evolutive a partir de carbonate de calcium amorphe
Authors: Dupuis T. , Ducloux J. , Butel P. , Nahon D. 
Published: December 2006

ResumeDans les encroûtements calcaires sous galet de la Plaine Poitevine, nous avons mis en évidence, par des méthodes microscopiques, une séquence minéralogique évolutive de la calcite. Par spectrométrie d'absorption infrarouge des éléments de la séquence prélevés en hiver, nous caractérisons, à côté de la calcite (bande à 1420 cm−1), du carbonate amorphe hydraté (bandes à 1405 et 1485 cm−1 et un autre type de calcite (bande à 1445 cm−1). Les résultats d'essais de laboratoire nous permettent d'envisager une évolution du carbonate amorphe vers la calcite par l'intermédiaire d'une phase calcitique transitoire, et d'aragonite toujours en faible proportion. La formation de ces carbonates est liée aux conditions bio-physico-chimiques du sol.
High-gradient magnetic separation (HGMS) in soil clay mineral studies
Authors: Russell J. D. , Birnie A. , Fraser A. R. 
Published: December 2006

AbstractA modified HGMS system is described in which the inclusion of a peristaltic pump to continuously circulate a suspension of a soil clay through the magnetic trap greatly facilitates the operation of the technique. Application of this purely physical method of mineral separation to a variety of soil clays—using IR spectroscopy to monitor the progress of the separation—illustrates the ease with which magnetic fractions comprising different iron-containing clay minerals may be separated from a single soil clay, thereby making these minerals more accessible for further study by other techniques.
The effect of various clay minerals on the thermal decomposition of stearic acid under ‘bulk Flow’ conditions
Authors: Heller-Kallai L. , Aizenshtat Z. , Miloslavski I. 
Published: December 2006

AbstractThe thermal decomposition of stearic acid in the presence of various clay minerals was studied in an open, inert system under isothermal (250°C) conditions. The distribution of hydrocarbons and the amount of CO2 evolved were determined. The degree of decarboxylation depended on the composition of the octahedral sheets of the clays. It was greater with trioctahedral than with dioctahedral minerals. The presence of dioctahedral minerals tended to reduce the amount of CO2 produced below that obtained with the neat acid. The nature of the hydrocarbons formed depended on the structure of the minerals. Different products were obtained with minerals that have accessible interlayers and channels (smectites, palygorskitesepiolite) than with the 1:1 clays and pyrophyllite or talc. Some minerals caused cracking to light-weight hydrocarbons. Higher surface acidity of the clay interlayers enhanced this process but was not the only decisive factor. In the systems studied, evolution of CO2 did not necessarily precede the formation of light- or medium-weight hydrocarbons from the parent acid.
Mineralogy and origin of Tertiary interbasaltic clays from the Faeroe Islands, Northeastern Atlantic
Authors: Parra M. , Delmont P. , Dumon J. C. , Ferragne A. , Pons J. C. 
Published: December 2006

AbstractMineralogical and chemical examination of Tertiary interbasaltic clays from the Faeroe Islands revealed three types of alteration of volcanic tufts and basalts: (1) Argillization of volcanic tuffs within a lacustrine environment resulted in the formation of aluminous beidellites and metahalloysites; these clays are associated with extensive coal layers at Suduroy. (2) Argillization of volcanic tuffs due to hydrothermal action resulted in the formation of thick layers of ferriferous beidellites associated with small amounts of hematite and zeolite (e.g. at Nolsoy). (3) Meteoric alteration of volcanic tufts and basalts, which took place under hot climatic conditions and contrasting seasons, led to the development of ferriferous and aluminous-ferriferous beidellites, metahalloysite, kaolinite, hematite and goethite in low (Høv profile) or high (Øravik profile) topographical positions. The three processes occurred individually or were superimposed.
The influence of aluminium on iron oxides: XIII. Properties of goethites synthesised in 0·3 M KOH at 25°C
Authors: Schulze D. G. , Schwertmann U. 
Published: December 2006

AbstractAluminium-substituted goethites were synthesised in 0·3 M KOH at either 25° or 70°C. The 25°C goethites had unit-cell a and c dimensions about 0·1–0·2% larger than the 70°C goethites of comparable Al substitution. Unit-cell b dimensions were similar regardless of synthesis temperature. The 25°C goethites contained larger amounts of Al in their structures than the 70°C goethites synthesised at the same initial Al/(Al + Fe) mole ratio in solution. The 25°C goethites had lower dehydroxylation temperatures and smaller differences between the two OH-bending bands than comparable 70°C goethites. These differences between the two sets of goethites are believed to be caused by the presence of more structural defects in the 25°C goethites than in the 70°C goethites. Goethites with the lowest Al substitutions consisted of crystals with several coherently diffracting domains, while at high Al substitutions the crystals were mainly monodomainic. Surface areas of the 25°C goethites varied in a complex manner as a function of thickness along [100], character of the domains, and physical size.
The colloidal stability of variable-charge mineral suspensions
Authors: Bartoli F. , Philippy R. 
Published: December 2006

AbstractA method of analysing the colloidal stability of variable-charge mineral suspensions as a function of pH is described, which combines light scattering with soluble element and surface charge measurements. The absorbance of the suspensions closely follows the A = k−m equation, where m = −dlgA/dlgλ is an aggregate light-scattering index which is inversely related to the limiting sedimentation speed v = dA600nm/dt. Usually, suspensions of variable-charge minerals scatter less near their point of zero charge where the aggregation process is a maximum, in contrast to environments where they are charged and well-dispersed. Although the morphology of goethite is that of elongated needles, kaolinite plates, and imogolite tubes, the coalesced sphere approach of the Mie theory allows rapid correlation of the absorbance at 600 nm with aggregate-size distribution, indirectly measured by the light- scattering aggregate-size index m confirmed by electron microscopy experiments. Kaolinite and goethite suspensions obey the diffraction scattering law with a variation in size of 2–20 µm from the dispersed to the aggregated particles. Imogolite and alumina gel suspensions possibly obey the anomalous diffraction scattering law and are present as 0·05–1 µm aggregates of their 50–100 Å structural units. Silica gel and the more dispersed imogolite suspensions possibly obey the anomalous Rayleigh scattering law with a variation of aggregate size from 700–3000 Å.
Marine and supergene alteration processes in a chloritized amphibole-schist, Deux-Sevres, France
Authors: Proust D. , Dudoignon P. , Bouchet A. , Meunier A. 
Published: December 2006

AbstractMineralogical examination of a strongly chloritized amphibole-schist indicated that it had been subjected to two alteration episodes of different origin. Structural and petrographic evidence showed that the alteration processes operated per descensum from the bedrock surface down to shallow depth, thus eliminating any hydrothermal episode due to fluid ascension through deep fractures. The rock was first altered into interstratified chlorite-vermiculite minerals with potassic interlayers. These potassic clay minerals occur in an originally K-deficient rock and seem to have been generated by a marine alteration episode; this episode appears to be contemporaneous with the Cenomanian transgression which covered the amphibole-schist with sandy-clayey deposits. The potassic clay minerals were replaced during a later meteoric alteration episode by kaolinites, iron oxides, and smectites with Mg, Ca interlayer cations.
Neoformation of halloysite on volcanic glass in a marine environment
Authors: Imbert T. , Desprairies A. 
Published: December 2006

AbstractTransmission electron microscopy of ultramicrotomed thin-sections of Pleistocene and Eocene glass shards revealed the neoformation of (i) illite and (ii) halloysite at the glass periphery. According to previous experimental studies, halloysite neoformation in marine environments can occur on glass shards deposited in Si-rich sediments; an excess of Ca tends to inhibit the reaction.