bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Solution Chemistry on the Hydrothermal Synthesis of Kaolinite
Authors: Miyawaki Ritsuro , Tomura Shinji , Samejima Soichiro , Okazaki Masaharu , Mizuta Hiroyuki , Maruyama Shin-Ichi , Shibasaki Yasuo 
Published: August 2006

AbstractThe hydrothermal synthesis of kaolinite was examined in the Al2O3-SiO2-H2O system to study inhibitory effects of additional ions on the formation of kaolinite. Syntheses were carried out with amorphous starting materials and salt solutions of various concentrations in Teflon pressure vessels at 220°C for 5 days. The reaction products were characterized by XRD, IR, DTA-TG, NMR and TEM. In all of the runs using solutions with cation concentrations less than 0.001 M, no significant effect on the formation of kaolinite was observed. The inhibitory effect of the univalent cations Li+, Na+ or K+ was less than that of divalent cations such as Mg2+ or Ca2+. The addition of trivalent Fe3+ or excess Al3+ ions interfered with the formation of kaolinite significantly. Sulfate and acetate solutions interfered with the formation of kaolinite more than chlorides and nitrates. No crystalline product was obtained using a 1.0 M basic solution of carbonate or hydroxide. The addition of the lithium ion to the system affected the crystallization of kaolinite only slightly. The use of 0.1 M LiCl and LiNO3 solutions for the syntheses improved crystallization of kaolinite along the [001] direction.
Synthetic Allophane and Layer-Silicate Formation in SiO2-Al2O3-FeO-Fe2O3-MgO-H2O Systems at 23°C and 89°C in a Calcareous Environment
Authors: Farmer V. C. , Krishnamurti G. S. R. , Huang P. M. 
Published: August 2006

AbstractSolutions containing AlCl3 and Si(OH)4 (concentrations ≤ 1.5 mM with molar Si:Al ratios of 1:2, 1:1 and 3:1) and FeCl2 (0, 0.5 and 1.0 mM) were adjusted to pH 8 with Ca(OH)2, and incubated at 23°C and 89°C without exclusion of air in the presence of CaCO3 for 8–12 weeks. The products were characterized by infrared spectroscopy and X-ray diffraction. Systems with 3:1 and 1:1 Si:Al ratios without Fe gave hydrous feldspathoids at 23° and 89°C. Systems with 3:1 Si:Al ratios containing Fe gave aluminous nontronites at 89°C and noncrystalline, nontronite-like products at 23°C. Systems with 1:1 Si:Al ratios with added Fe gave Fe(III)-substituted hydrous feldspathoids at 23°C. At 89°C, the system with 1:1 Si:Al ratios and 0.5 mM Fe produced a “protohalloysite,” while that with 1.0 mM Fe gave a poorly ordered nontronite-like layer silicate. In systems with 1:2 Si:Al ratios, the formation of “protoimogolite” at 23°C was little affected by additions of Fe. At 89°C, the “protoimogolite” decomposed to boehmite and poorly-ordered layer silicate phases. Inclusion of 1 mM MgCl2 in the above systems had no effect on the products at 23°C, but at 89°C produced saponites and a mixed layer saponite-chlorite in the 3:1 Si:Al systems, and saponite-like layer structures in the 1:1 and 1:2 Si:Al systems.
Mixed-Layer Clay Geothermometry in the Wairakei Geothermal Field, New Zealand
Authors: Harvey Colin Charles , Browne Patrick R. L. 
Published: August 2006

AbstractMixed-layer clays of variable composition and structure occur in core samples from two drillholes (WK207 and WK210) drilled into the Te Mihi sector of the Wairakei geothermal field. These were identified by X-ray diffraction analysis of glycolated and oriented sample fractions at less than 2 μm and less than 0.2 μm.Low permeability lacustrine sediments encountered by drillhole WK207 contain a well-developed sequence of mixed-layer clays. The shallowest downhole appearance of mixed-layered illite/smectite (I0.6/Sm) occurs at 146 m depth where temperature is only 100°C. Discrete illite is present only below 297 m (200°C) in the finer size fraction (less than 0.2 ¼m). Chlorite first appears downhole, in association with illite-smectite, at 177 m depth (110°C).Drillhole WK210 encountered predominantly ignimbrites and rhyolites, and fluid flow here is mainly in channels. Within these rocks, a sequence of interlayered clays is poorly developed. Discrete illite and chlorite are present in core from only 244 m (180°), but the measured temperatures where interlayer clays occur ranges from 140 to 209°C.Differences in the identity of clay minerals present in the Wairakei reservoir, where conditions are otherwise the same, demonstrate the strong control that the type of fluid flow has on their formation. In poorly-permeable sediments, where diffuse fluid flow prevails, a clearly-defined sequence of mixed-layer clays occurs. These are absent where channel flow dominates, the discrete chlorite and illite deposit directly from solution.
Saponite and Vermiculite in Amygdales of the Granby Basaltic Tuff, Connecticut Valley
Authors: April Richard H. , Keller Dianne M. 
Published: August 2006

AbstractClay of apparent hydrothermal origin that fills amygdales in the Granby Basaltic Tuff (Lower Jurassic) of the Connecticut Valley was analyzed and found to consist of two exceptionally well-crystallized Fe-rich, trioctahedral 2:1 layer expandable phyllosilicates. Based on chemical and XRD analyses, the minerals were tentatively identified as saponite and vermiculite. The saponite exists predominately in the two-water hydration state, but also displays one- and three-water layer hydration states, which suggests heterogeneous layer charge distribution—a phenomenon not uncommon in smectites. The identity of the second clay remains equivocal, but XRD analyses, especially with regard to the swelling properties of the clay, indicate that it is a vermiculite. The well-crystallized nature of the Granby clay and the large size of the clay flakes (up to 1 mm) allowed us to use SEM/EDS X-ray imaging and spot analysis techniques in an attempt to detect chemical differences between the saponite and vermiculite. Results showed that the chemistry of individual crystals, within and among amygdales, was essentially uniform. This suggests that the saponite and vermiculite are chemically similar and that variations in their swelling properties result from other factors, such as crystal size, layer charge density, or charge localization within the unit layers. Crystal size differences in the Granby clay were observed with both the petrographic and scanning electron microscope. Changes in layer charge density or charge localization within unit layers could have been affected by the oxidation of Fe2+ to Fe3+, a transformation inferred from the green-to-brown color changes observed in the larger amygdales. The Granby clay is of special importance, because it is one of the few examples of a naturally occurring mixture of two well-crystallized, Fe-rich trioctahedral 2:1 layer expandable phyllosilicates with crystallochemical and swelling properties that appear to bridge the operational definitions for the smectite and vermiculite groups.
Characterization of the End of Smectite-to-Illite Transformation: Decomposition of X-Ray Patterns
Authors: Lanson Bruno , Besson Gérard 
Published: August 2006

AbstractComplex X-ray diffraction (XRD) profiles are described crystallographically by simulating XRD peaks for each phase, and adding the various elementary patterns to fit the experimental X-ray pattern. X-ray patterns of a ground muscovite and three polyphasic diagenetic I/S samples are fitted with this powerful, but time-consuming, technique. In the 6°–10°2θ CuKα range, the asymmetry of the muscovite peak is related to a very broad coherent scattering domain size (CSDS) distribution; for the I/S samples the even greater asymmetry is due to the presence of several phases with close, but distinct crystallographic characteristics (I/S, illite, and detrital mica).A simulation-decomposition approach for modelling XRD patterns is introduced to describe quickly and accurately the various clay minerals (essentially mixed-layer illite/smectite and illite) present in a sedimentary series, and to follow their individual evolution during diagenesis. The theory for these simulations is described briefly. The influence of mixed-layer heterogeneity (the distribution of CSDS, and the distribution of smectite content) on the shape of X-ray peaks is shown theoretically to be minimal. Indeed, for both CSDS and smectite content, the important parameter for peak shape appears to be the mean value of the distribution and not its width and/or its shape. The theoretical limitations of the decomposition method are presented. Minor experimental limitations (reproducibility, experimental peak shape, discrimination) make this method a powerful and reliable tool to describe X-ray patterns. The method is used to show the simultaneous occurrence of three “illitic” phases in a sedimentary series from the Paris Basin. The respective evolution of the three phases is clearly evidenced by using this decomposition method. However, the precise identification of these different phases remains difficult to determine because of the difference in peak width between simulated and experimental X-ray patterns.
Smectite-to-Illite Conversion in a Geothermally and Lithologically Complex Permian Sedimentary Sequence
Authors: Bühmann C. 
Published: August 2006

AbstractThe <0.5-μm fraction of 120 samples from a lithologically complex Permian sedimentary sequence, underlying dolerite intrusive sheets, has been characterized by means of X-ray diffraction to establish I/S compositions as a function of temperature, lithology and time duration. Illitization has been active over the entire 210 m depth range and the clay data reflect both the local pattern of contact metamorphism and the more regional trend of heat flow during burial. A continuum exists in the illite proportions of the illite/smectite interstratifications with increasing distance from the intrusive sheet ranging from R = 3 with less than 5% smectite via R = 2 and R = 1 to R = 0 with up to 70% smectite. In the mixed-lithology section, individual component layers in the I/S within similar distance levels, but between contrasting lithologies, appear to vary only within a very restricted compositional range. In the massive mudstone strata, however, more silty parts contain I/S of a higher degree of ordering and lower expandability. Calcite contents are reflected in a higher rate of chlorite formation, but not in the I/S composition. A satisfactory inverse correlation was found between percent smectite in I/S and vitrinite reflectance in the lithologically complex section. R = 1 interstratifications are associated with a maximum vitrinite reflectance of 1.07–1.29 and R > 1 phases with 1.93–2.7, indicating that time duration is not a controlling factor in the illitization process in this facies. R = 0 interstratifications are present in a massive mudstone/siltstone sequence situated furthest from the igneous intrusives, and display vitrinite reflectance values of 1.42–1.52. No satisfactory explanations for this finding can be offered.
Microtopography of Regularly-Interstratified Mica and Smectite
Authors: Kitagawa Ryuji , Matsuda Toshihiko 
Published: August 2006

AbstractThe gold decoration technique of electron microscopy was used to observe the microtopography of natural (001) surfaces of 1:1 regularly-interstratified mica/smectite minerals (expandable layer: 40–45%) collected from four different pyrophyllite deposits in Japan. The specimens are characterized by parallel growth steps of malformed, circular or polygonal forms with varying step separations. Many particles exhibit paired steps that seem to show spiral growth. Microtopographic observations suggest that the growth of regular interstratification (at least for the specimens investigated in this study) normally takes place by an interlacing of paired steps. If the height of a single step corresponds to that of a mica or a smectite layer, the particles are estimated to be normally 40–300 Å in thickness. If the particles on which a spiral center is observed are single crystals of interstratified mica and smectite, then some crystals investigated in this study are far thicker than fundamental particles. The results of this study are interpreted to suggest that these regularly-interstratified mica/smectites were formed by hydrothermal metasomatism from their respective host rocks.
The Crystal Structure of Bannisterite
Authors: Heaney Peter J. , Post Jeffrey E. , Evans Howard T. 
Published: August 2006

AbstractThe crystal structure of bannisterite, a modulated, mica-like mineral species, of general composition Ca0.5(K,Na)0.5(Mn,Fe,Mg,Zn)10(Si,Al)16O38(OH)8·nH2O, has been solved and refined for specimens from Franklin Furnace, New Jersey (FF), and Broken Hill, Australia (BH). The crystals are mono-clinic in space group A2/a, with (for FF) a = 22.265(1) Å, b = 16.368(1) Å, c = 24.668(2) Å, β = 94.285(5)°; and (for BH) a = 22.286(1) Å, b = 16.386(1) Å, c = 24.575(2) Å, β = 94.355(7)°; Z = 8. Refinement with anisotropic thermal factors reached Rw = 0.034 (FF) and 0.039 (BH). Like stilpnomelane and ganophyllite, bannisterite has a modified 2:1 trioctahedral layer structure in which some of the tetrahedra are inverted towards the interlayer region and linked to inverted tetrahedra in the opposite layer. The octahedral sheet is strongly corrugated along b. The tetrahedral sheet consists of 5-, 6-, and 7-fold rings, and bond distance calculations indicate that Al is concentrated into two of the four inverted tetrahedra. The interlayer Ca, K, and H2O species are highly disordered, as indicated by anomalously large temperature factors and partial occupancies. Localized differences in the Al/Si arrangements in the inverted tetrahedra induce disorder among the interlayer cations.
Montmorillonite-Salt Interactions at 550°C
Authors: Natale I. M. , Helmy A. K. 
Published: August 2006

AbstractThe reactions between montmorillonite and carbonates and hydroxides of Na, K and Li were studied at 550°C as a function of salt content and time. The reactions were found to be rapid with a half-time of 20–30 minutes. Good agreement was obtained between theoretical and experimental stoichiometric values for the clay-carbonate reaction. The 001 and 02,11 reflections of the products of the clay-salt reactions diminished in intensity and/or disappeared at and above the stoichiometric concentrations of the reactants.
The Thermodynamic Status of Compositionally-Variable Clay Minerals: A Discussion
Authors: Aja Stephen U. , Rosenberg Philip E. 
Published: August 2006

AbstractAccording to Lippmann (1977, 1982) wide compositional variations and excess enthalpies of mixing calculated with electrostatic models imply that clay minerals of variable composition are dis-equilibrium solids. However, recent ATEM analyses of illite samples indicate compositional homogeneity of single illite grains and limited compositional variations in sedimentary basins. Moreover, Lippmann's electrostatic model may be inadequate inasmuch as it neglects polarization energy which is known to be a significant component of lattice energy even in dominantly ionic structures. Contrary to the assumptions of Lippmann, I/S minerals have also been shown to undergo Ostwald ripening.May et al. (1986) reported that smectites do not reversibly control equilibria and further argued that conceptual and experimental deficiencies inherent in the solubility method prevent the attainment and demonstration of equilibrium in experiments with complex aluminosilicates of variable composition. However, equilibrium may be assumed if: (1) steady states are approached from both under- and over-saturation, (2) the slopes of univariant lines representing mineral-solution equilibria are rational over a wide range of solution compositions and temperature, and (3) results are reproducible in experiments of long duration. Recent solubility studies of smectites, chlorites, and illites meet these criteria indicating that clay minerals of variable composition are true phases capable of attaining equilibrium.
Application of Rietveld Refinement Techniques to a Disordered IIb Mg-Chamosite
Authors: Walker Jeffrey R. , Bish David L. 
Published: August 2006

AbstractThe structure of a disordered IIb Mg-chamosite was studied using Rietveld refinement techniques and powder X-ray diffraction (CuKα, 18–120° 2θ in 0.02° 2θ increments). The refinement in space group CĪ yielded high precision lattice parameters (a = 5.36982(5)Å, b = 9.3031(9)Å, c = 14.2610(6)Å, α = 90.315(5)°, β = 97.234(7)°, γ = 90.022(9)°) and atomic coordinates very similar to previous studies. However, the presence of semi-random stacking in this specimen created a situation in which not all atoms could be precisely located: the positions of the octahedral cations and anions which repeat at intervals of ±b/3 could be uniquely determined in three dimensions whereas only the z parameter of the other atoms could be refined. The reasonable appearance of the final model, despite the fact that many of the atom positions could be located in only one dimension, may have resulted because all of the atoms in this structure except O(5) repeat at intervals which are very nearly ±b/3.
X-Ray Diffraction Studies of Illite/Smectite from Rocks, < 1 μm Randomly Oriented Powders, and < 1 μm Oriented Powder Aggregates: The Absence of Laboratory-Induced Artifacts
Authors: Reynolds R. C. 
Published: August 2006

AbstractX-ray diffraction patterns were obtained from rock fragments, < 1 μm randomly oriented freeze-dried powders, and < 1 μm oriented aggregates for 11 mixed-layered illite/smectite samples (K-bentonites) that cover the range from 14 to 100 percent expandable. In all cases, 00l and hkl comparisons show no evidence of laboratory induced artifacts. Either the laboratory procedures caused no disaggregation of fundamental illite particles, or, if they did, fundamental particle reaggregation during sample preparation duplicated the one and three-dimensional structures of the illite/smectite in the original, untreated rock.Demodulation of the 20l, 13l reflections into a two-dimensional band shape occurred with increasing percent expandable layers in illite/smectite. This result strongly supports the contention that turbostratic displacements occur at the expandable interfaces between fundamental particles, and are limited to those sites.A comparison of the quantities measured by powder X-ray diffraction and high resolution transmission electron microscope (TEM) lattice fringe image techniques for disordered crystals suggests that meaningful comparisons between the two methods can be made only if a sufficient number of images are recorded to define the statistical parameters of the disorder.
Electrophoretic Behavior of Imogolite under Alkaline Conditions
Authors: Karube Jutaro , Nakaishi Katsuya , Sugimoto Hideo , Fujihira Masami 
Published: August 2006

AbstractElectrophoretic mobility of imogolite has been reported as positive (migration toward the negative electrode) below pH 9, and zero above pH 9. However, when mobility of dilute imogolite suspensions (5 × 10−3 kg/m3) was measured, it was found to be negative above pH 9. The reason that imogolite does not behave as a negative colloid when the clay concentration is not very dilute is because the imogolite forms floccules large enough to prevent migration. Imogolite has a PZNC at about pH 6, and has a PZC at pH 8.5–9.0 showing a relatively low absolute mobility under alkaline conditions compared to that under acid conditions. The fact that imogolite behaves like this is understandable given the location of negative charge appearing on the inside surface of the thin fibrous tube, according to the structural model of imogolite.
Decomposition of X-Ray Diffraction Patterns: A Convenient Way to Describe Complex I/S Diagenetic Evolution
Authors: Lanson Bruno , Velde Bruce 
Published: August 2006

AbstractDecomposition of complex X-ray diffraction profiles is used on well characterized (image analysis of transmission electron micrographs, X-ray fluorescence chemical analyses) diagenetic samples from the Paris basin. The simultaneous occurrence of three “illitic” phases (mixed-layer illite/smectite or I/S, poorly crystallized illite, and mica-like phase) is shown on the various diffraction peaks of the 2–50 °2θ CuKα (44–1.8 Å) range. However, because of theoretical and experimental constraints, it is easier to perform the decomposition routine in the 5–11 °2θ CuKα (17.6–8.0 Å) range. The identification (i.e., illite content and mean coherent scattering domain size) of the various phases is performed by comparing the associated elementary peak characteristics (position, full width at half maximum intensity) with simulated X-ray patterns. When available, the characteristics obtained from the various angular regions are mutually consistent; however, the precise structures of smectite and illite end-members, on the one hand, and the structure of I/S crystallites, on the other hand, are not well known. Consequently, on some angular regions, there is a discrepancy between the characteristics obtained on experimental and calculated X-ray profiles. The definition of more realistic simulation hypotheses for I/S minerals, and for other interstratified clay minerals, would make this powerful and reliable tool to describe X-ray patterns a precise and sensitive identification tool even for complex clay parageneses.
A Structural Model for Natural Siliceous Ferrihydrite
Authors: Parfitt R. L. , Van der Gaast S. J. , Childs C. W. 
Published: August 2006

AbstractX-ray diffraction of four natural samples of ferrihydrite indicates the presence of crystalline domains within the primary particles. The average diameter of the primary particles (determined from low-angle powder patterns) decreases from 4.1 nm to 2.5 nm as the domain size in the xy-plane (determined by applying the Scherrer equation to the broad [110] XRD peak at 0.26–0.27 nm) decreases from 1.0 nm to 0.77 nm. The Si content (measured by acid-oxalate extraction) increases from 4.1% to 6.1% as both the domain and particle sizes decrease; other factors, however, are likely to be important in influencing particle size. For one sample of ferrihydrite, the smallest possible domain (i.e., c = 0.94 nm in the z-direction) contains 36 O atoms and three Si atoms. A model for ferrihydrite is suggested in which silicate bonds to, and bridges, the surfaces of the domains. The model can account for several aspects of the behavior of siliceous ferrihydrites.
Illite from the Potsdam Sandstone of New York: A Probable Noncentrosymmetric Mica Structure
Authors: Reynolds R. C. , Thomson C. H. 
Published: August 2006

AbstractIllite from the Potsdam Sandstone (lower Ordovician) of Northwestern New York was studied by powder X-ray diffraction, scanning electron microscopy, and chemically analyzed and dated by the K/Ar method. The texture and ages of 360 and 392 Ma on two samples establish that the mineral is authigenic and relatively uncontaminated by Precambrian detritus. Random powder X-ray diffraction patterns show sharp and relatively intense 02l and 11l reflections, indicating an ordered structure. Comparisons with calculated patterns demonstrated that the mineral is not the common 1M or 2M1 polytype. Instead, the experimental pattern is very similar to that of a 3T polytype, but it agrees better with the calculated pattern of the octahedral cis-vacant, noncentrosymmetric (space group C2) structure found by Méring and Oberlin (1967) and Tsipursky and Drits (1984) in smectites, proposed for mica by Drits et al. (1984) and found by Zvyagin et al. (1985).