bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Microtopography of Lath-Shaped Hydrothermal Illite by Tapping-Mode™ and Contact-Mode AFM
Authors: Kuwahara Yoshihiro , Uehara Seiichiro , Aoki Yoshikazu 
Published: August 2006

AbstractLath-shaped hydrothermal illite particles in Izumiyama pottery stone were examined by contact-mode atomic force microscopy (CMAFM) and tapping-mode AFM (TMAFM) in air. With CMAFM, the lath-shaped particles showed interlacing patterns on the (001) surface in deflection images, while in height images such patterns were unclear. Also, evidence of artifacts caused by frictional forces between the surface and tip and/or edge effects were found in the CMAFM height images of the particle and Si substrate surfaces. In contrast, TMAFM showed interlacing patterns clearly in both amplitude and height images, and artifacts were barely evident. The TMAFM height images permitted the accurate measurement of 1.0- or 2.0-nm height steps corresponding to single or double mica layers, as well.Many lath-shaped particles in the Izumiyama hydrothermal illite exhibit interlacing patterns on their (001) surface, as shown by these AFM observations. The interlacing patterns are characterized by polygonal spirals with comparatively wide spacings and steps having a height of 1.0 or 2.0 nm. Generally a single lath-shaped particle has a single spiral center on the (001) surface, and 2 mica layers rotated 120° originate from the dislocation point. These support the view that lath-shaped illites belong to the 2M1 polytype. It is likely that these illite particles were formed by a uniform process of development that is characterized by very slow growth, spiral mechanisms in that growth and low supersaturation conditions.
Nomenclature of the Micas
Authors: Rieder Milan , Cavazzini Giancarlo , D'yakonov Yurii S. , Frank-Kamenetskii Viktor A. , Gottardi Glauco , Guggenheim Stephen , Koval’ Pavel W. , Müller Georg , Neiva Ana M. R. , Radoslovich Edward W. , Robert Jean-Louis , Sassi Francesco P. , Takeda Hiroshi , Weiss Zdeněk , Wones David R. 
Published: August 2006

AbstractEnd members and species defined with permissible ranges of composition are presented for the true micas, the brittle micas and the interlayer-cation-deficient micas. The determination of the crystallochemical formula for different available chemical data is outlined, and a system of modifiers and suffixes is given to allow the expression of unusual chemical substitutions or polytypic stacking arrangements. Tables of mica synonyms, varieties, ill-defined materials and a list of names formerly or erroneously used for micas are presented. The Mica Subcommittee was appointed by the Commission on New Minerals and Mineral Names (“Commission”) of the International Mineralogical Association (IMA). The definitions and recommendations presented were approved by the Commission.
Modification of Sepiolite by Treatment with Fluorides: Structural and Textural Changes
Authors: Belzunce María Jesús , Mendioroz Sagrario , Haber Jerzy 
Published: August 2006

AbstractIn the search for new applications of natural silicates, various F− treatments have been applied to sepiolite to increase its acidic properties and for use as a catalyst in reactions occurring via carbonium ions. Two types of treatments including hydrofluoric acid (HF) at different concentrations and 2 N NH4F have been utilized and the physicochemical characteristics of the resulting materials studied using standard techniques. The X-ray diffractogram (XRD) patterns indicate a decrease in crystallinity of the original material as well as the appearance of amorphous silica. SEM micrographs showed a shortening and aggregation of the sepiolitic fibers. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), thermogravimetric analysis/differential thermal analysis (TGA/DTA), N2 adsorption-desorption isotherms and Hg intrusion were used to study the changes occurring in the structure, surface area and pore distribution of samples and acidity was evaluated by IR and thermoprogrammed desorption (TPD) of adsorbed ammonia and pyridine. It was found that acidity increased in most of the samples after anionic and cationic interchange between the activating agents and the surface sites, or extralattice cations. Additionally, structural changes induced by treatments modified the Brönsted and Lewis acidity. Mild treatments with ammonium fluoride are more effective than HF treatments in acidity generation.
Chemical Variations in Chlorite at the Los Humeros Geothermal System, Mexico
Authors: Martínez-Serrano Raymundo G. , Dubois Michel 
Published: August 2006

AbstractThe chemical composition of hydrothermal chlorite was determined by means of more than 200 electron microprobe analyses (EMPA) in almost all of the 70 chlorite-bearing samples taken from 5 boreholes in a study of the active geothermal system of Los Humeros, Mexico. Bulk rock composition of 6 different volcanic lithologies, as well as available in situ temperatures and chemical compositions of chlorite, were analyzed by principal component analysis (PCA) in order to test the dependence of chlorite composition on physicochemical parameters. The results show that chlorite minerals display a wide range of chemical compositions in this hydrothermal system that reflect the particular conditions of crystallization episodes: The Na + K + 2Ca values are low (from 0 to 0.6) and they show no correlation patterns with octahedral vacancies (¤) in chlorite, indicating that compositional variations are not due to the intergrowth of smectite and/or illite. The octahedral occupancy of most chlorite is relatively high (from 11.3 to 11.95), especially that from a high-temperature range, as is the case of metamorphic chlorite. The octahedral occupancy seems not to be related to other chemical variables of chlorite from the G3, G4 and G5 lithologic units, suggesting that the lack of complete occupancy is not dependent on “contamination” by other silicates (such as quartz). Cationic substitution in tetrahedral sites in chlorite is small and via a Tschermak exchange (MgVISiIV ↔ AlVIAlIV). To preserve a charge balance in the structure, an octahedral substitution of R2+ by Al3+ accompanies the Tschermak exchange. The chemical composition of hydrothermal chlorite is very similar to that of metamorphic chlorite but slightly different from equivalent phases found in diagenetic environments. In hydrothermal chlorite the SiVI, AlVI and ¤ decrease, whereas the AlIV and Fe2+ contents increase with the degree of alteration and depth, the same way as in chlorite formed in diagenetic high-temperature environments. The ferrous iron content, in general, increases with depth and temperature; however, whole-rock chemistry affects the iron distribution in chlorite of Los Humeros. Changes in the oxygen fugacity of fluids at depth also affect the iron distribution in chlorite, XFe = Fe/(Fe + Mg), which ranges from 0.30 to 0.38 in oxidizing conditions and from 0.39 to 0.60 in reducing conditions. Finally, the chemical composition of chlorite in Los Humeros appears to change with temperature, but the correlations of ¤ and AlIV with temperature are more variable than in another nearby active geothermal system located in Los Azufres, Mexico. This implies that geothermometers based on chlorite composition and empirically calibrated in some geothermal systems cannot be generalized and it is necessary to consider other physicochemical variables.
Structural Organization of Na- and K-Montmorillonite Suspensions in Response to Osmotic and Thermal Stresses
Authors: Faisandier K. , Pons C. H. , Tchoubar D. , Thomas F. 
Published: August 2006

AbstractIn order to understand the influence of salt concentration and temperature on the behavior and properties of clays used in drilling muds, we studied montmorillonite supensions (4 g clay/100 g solution) in 0.1, 0.5 and 1 M NaCl and KCl solutions. A fraction of each sample was heated to 200 °C in a closed vessel for 7 d, then cooled at room temperature (RT, 25 °C). Small-angle X-ray scattering (SAXS) spectra were recorded, for all the samples, at RT. The structure of the clay particles was determined by comparing the experimental intensity with the theoretical intensity computed from a model that took into account the number of layers per particle, the hydration state of the layers (0, l, 2, 3 or 4 water layers) and the order in the succession of these states. With this set of parameters, we can compute the mean statistical parameters M¯ (mean number of layers per particle), d¯ (mean interlayer distance) and δ¯2/d¯2 (parameter describing the disorder of the distribution of interlayer distances). The evolution of these parameters shows that:1)At low concentration (0.1 M NaCl or KCl), the samples do not consist of particles but of isolated layers (M = 1). The suspensions form gel-like structures. The difference between Na and K suspensions, or between heated and nonheated samples, is unnoticeable at the studied scale (5–500 Å).2)An increase in salt concentration (from 0.1 to 0.5 M) brings the sample in a granular state: we notice the appearance of particles at 0.5 M (M¯ ≥ 25). Differences appear between NaCl and KCl suspensions, and the temperature effect becomes visible. Thus, we noticed that in NaCl suspensions, particles are composed of hydrated layers (1, 2, 3 or 4 water layers) and internal porosity (d > 30 Å), whereas suspensions in KCl are characterized by the presence of interlayer distances of 10 Å, that is, of collapsed layers. Particles in the KCl suspensions are much thicker than in the NaCl corresponding ones, and also less hydrated at the interlayer level as well as at the internal porosity level. Further increase in salt concentration (0.5 to 1 M) amplifies this effect. As far as temperature is concerned, its effect is to promote the clay dispersion by breaking up the particles, dehydrating and disordering them. This effect is more important for low salt concentration, that is, when the system is less stressed.
The Formation of Sulfides During Alteration of Biotite to Chlorite-Corrensite
Authors: Li Gejing , Peacor Donald R. , Essene Eric J. 
Published: August 2006

AbstractTransmission electron microscopy/analytical electron microscopy (TEM/AEM) were utilized to study pyrite and sphalerite inclusions in chlorite or mixed-layer chlorite-corrensite from an analcimized ash bed in the Etalian stage (Middle Triassic), South Otago, New Zealand. These sulfide inclusions occur as elongated crystals up to 1 × 15 µm in size, within lens-shaped voids between separated, deformed (001) layers of (primarily) chlorite and mixed-layer chlorite-corrensite grains of typical detrital shape or chlorite packets in chlorite-mica stacks (intergrowths of chlorite and phengite packets) up to 40 × 150 µm in size. Relict biotite layers within chlorite, mixed-layer chlorite-corrensite and berthierine have textures implying replacement of the former by the latter, whereas in other unaltered samples only fresh biotite was observed. Anatase occurs in otherwise Ti-free chlorite, whereas relict biotite contains significant Ti (0.3 moles per 22 oxygen atoms). No sulfide minerals have been found in fresh biotite and phengite.Mass balance considerations indicate that S and Zn were introduced via pore fluids and that the Fe was provided by the decomposition of biotite to secondary phyllosilicates. The alteration of biotite and the reaction of biotite to form chlorite and pyrite is controlled by aH+/aK+ as well as oxidation of reduced S species or reduction of oxidized S species from solution. Simple calculations with the observed compositions of chlorite and biotite suggest that some of the Fe in biotite was actually removed in solution rather than precipitated in pyrite and chlorite. Similar textures are abundant in ferroan phyllosilicates elsewhere, implying that the mechanism may apply widely to precipitation of sulfides in phyllosilicates during early diagenesis of sediments.
Burial Diagenetic Processes and Clay Mineral Formation in the Molasse Zone of Upper Austria
Authors: Gier Susanne 
Published: August 2006

AbstractCores of pelitic sediments (Eocene-Miocene) of the drillings Puchkirchen 1 and Geretsberg 1 (Molasse Basin, Upper Austria) have been studied to determine the mineralogical and chemical changes taking place during burial diagenesis. Mineralogical and chemical investigations of the bulk samples show that the deepest samples of the profiles are derived from a different source area. In particular, there is an increase in kaolinite and chlorite with depth and a decrease in quartz related to the initial sedimentology and provenance.Investigations of the <2 µm and <0.2 µm fractions of the profiles Puchkirchen 1 and Geretsberg 1 reveal the diagenetic overprint of the mineral constituents: The gradual illitization of mixed-layer illite-smectite, also reflected in an increase of K2O and Al2O3, is displayed most prominently in the <0.2 µm fraction. The source for the Al and K is the dissolution of K-feldspar (<2 µm fraction), as indicated in many previous studies.The I-S mixed-layer phases are randomly interlayered to a depth of 1600 m; from there on a regular interstratified I-S phase appears in coexistence with the randomly interlayered I-S mixed layer. The randomly oriented phase is still present in major amounts to depths of 2500 m, presumably as a result of the low geothermal gradient (2.9 °C/100 m) in the Molasse Basin.The calculation of the structural formula of the end members illite and smectite from this series of I-S mixed-layer phases gave the following results: Smectite: $${K_{0.14}}{X^ + }_{0.44}\left( {A{l_{1.10}}M{g_{0.46}}F{e_{0.36}}T{i_{0.01}}} \right)S{i_{4.03}}{O_{10}}{\left( {OH} \right)_2}$$Illite: $${K_{0.44}}{X^ + }_{0.19}\left( {A{l_{1.26}}M{g_{0.42}}F{e_{0.38}}T{i_{0.01}}} \right)\left( {S{i_{3.52}}A{l_{0.48}}} \right){O_{10}}{\left( {OH} \right)_2}$$The end-member interlayer charge for the smectite component (+0.58) is higher than reported for typical smectites (+0.32 to +0.47). It is suggested that the I-S phases of the Molasse Basin are probably intergrowths of 3 layer-silicate members: illite, low-charged smectite and high-charged smectite. The determined smectite end-member composition represents, therefore, an average for a variable 2-component smectite system. The charge-differences of the 2 smectites would likely reflect the differences in source material, which in turn would have led to the formation of different early, highly smectitic I-S phases in the sedimentary basin.
Layer-Charge Heterogeneity in Smectites of I-S Phases in Pelitic Sediments from the Molasse Basin, Austria
Authors: Gier Susanne , Ottner F. , Johns W. D. 
Published: August 2006

AbstractThe purpose of this study was to characterize more fully the surface charge characteristics of the end-member smectite in illite-smectite (I-S) mixed-layer phases found previously in pelitic sediments of the Molasse Basin in Austria. The smectite end member was shown to have an unusually high interlayer charge (0.58). Based on earlier work on pure smectites, it was hypothesized that this high charge represents the mean of a mixture of a higher- and lower-charged smectite component intermixed with illite. To test this hypothesis, the magnitude of the interlayer charge of the smectites was evaluated using 2 different methods: alkylammonium ion orientation and K-fixation by wetting and drying.Using 2 I-S samples of different I-S ratios, saturated with alkyammonium ions of chain lengths nc = 5–18, X-ray diffraction patterns (XRD) could be interpreted as representing a 3-component system, consisting of randomly interlayered high- and low-charged smectite and illite.K-fixation, carried out by K-treatment and followed by 100 wetting and drying (WD) cycles, confirmed the presence of a high-charged smectite component admixed with low-charged smectite, both interlayered with illite. The wetting and drying of the K-treated samples led to interlayer collapse of the high-charged smectite component and to the production of illite layers stable against exchange with 0.1 N SrCl2. The 2 smectites occur in the ratio of about 1:1 and consist of 1 phase with an interlayer charge of about 0.76 and another phase with a normal charge of about 0.40. During diagenesis, the 2 kinds of smectite are altering simultaneously to the same end-member illite along 2 different reaction paths.
X-Ray Diffraction Intensity Ratios I(111)/I(3¯11) of Natural Heulandites and Clinoptilolites
Authors: Esenli Fahri , Kumbasar Isik 
Published: August 2006

AbstractHeulandite-group zeolites are abundant in the Miocene pyroclastics from Western Anatolia, Turkey. We investigated the relation between the I(111)/I(3¯11) intensity ratios measured by X-ray diffraction (XRD) and the content of exchangeable cations for 15 samples of natural heulandite-group minerals gathered from the Gördes and Bigadiç regions of Western Anatolia. The intensity ratios range from 0.77 to 0.94 in natural heulandites and from 1.38 to 1.80 in natural clinoptilolites. The data obtained from Na-, K- and Ca-exchanged forms of a heulandite and clinoptilolite show that the intensity ratio increases with Na-, K- and Ca-exchange in heulandite and also with Na- and K-exchange in clinoptilolite, whereas it decreases with Ca-exchange in clinoptilolite. The intensity ratios were calculated using the known structural data of clinoptilolites to understand the effect of positions, amounts and kinds of exchangeable cations and water molecules. An increase in Na and Ca may increase or decrease the intensity ratio, depending on their sites and occupancies. Potassium causes a significant increase in the intensity ratio and an increase in Mg decreases the intensity ratio. There is a strong correlation between the intensity ratio I(111)/I(3¯11) and (Na + K)/(Ca + Mg) ratio and thermal stability, both of which have been used to characterize heulandite-group minerals.
Solid State NMR Characterization of the Thermal Transformation of an Illite-Rich Clay
Authors: Roch G. E. , Smith M. E. , Drachman S. R. 
Published: August 2006

AbstractLode, a dioctahedral illite-rich clay from Latvia belonging to the mica group of clay minerals, undergoes thermal transformation via a series of structurally disordered intermediate phases. Despite containing high levels of paramagnetic Fe substituted into the octahedral sites, 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra of sufficient quality are obtained to resolve different structural units, showing clearly defined structural changes which occur in the sample during calcination to 1200 °C. However, Fe plays a significant role in broadening the Al signal, with integrated peak intensities decreasing as temperature increases. Significant differences are revealed in the thermal decomposition process by NMR spectra between pyrophyllite, Ca-montmorillonite and illite clays, possibly due to the different cations present in the interlayer. It has also been shown for illite that no structural differences at the atomic level occur when the dwell time at a particular temperature is varied and no difference is observed between samples that have different thermal histories; however, a minor effect of particle size and surface area is visible in the NMR data.
Destinezite (“Diadochite”), Fe2(PO4)(SO4)(OH)·6H2O: Its Crystal Structure and Role as a Soil Mineral at Alum Cave Bluff, Tennessee
Authors: Peacor Donald R. , Rouse Roland C. , Coskren T. Dennis , Essene Eric J. 
Published: August 2006

AbstractA new occurrence of destinezite (diadochite), ideally Fe2(PO4)(SO4)(OH)·6H2O, is described from Alum Cave Bluff, Great Smoky Mountains National Park, Tennessee, where it occurs in soil and in a weathered Precambrian phyllite in unusually large crystals associated with other hydrated sulfates such as pickeringite-apjohnite. Destinezite is triclinic, P1̄, with a = 9.570(1), b = 9.716(1), c = 7.313(1) Å, α = 98.74(1)°, β = 107.90(1)°, γ = 63.86(1)° and Z = 2. Its crystal structure consists of infinite chains of Fe(O,OH,H2O)6 octahedra, sulfate tetrahedra and phosphate tetrahedra linked by a unique system of vertex sharing. The chains are weakly bonded into slabs by hydrogen bonding between OH and H2O of the Fe(III) octahedra and oxygen ions of the sulfate tetrahedra. Slabs of tetrahedral/octahedral chains alternate with sheets of H2O molecules. The structure thus somewhat resembles hydrated clay minerals, with H2O molecules that act as hydrogen bond donors and acceptors to oxygen atoms of adjacent slabs. Destinezite and diadochite occur at numerous localities worldwide and have been assumed to be identical, but this identity has never been proven. It is proposed that the name “destinezite” be applied to visibly crystalline, triclinic Fe2(PO4)(SO4)(OH)·6H2O and “diadochite” to massive to earthy, poorly ordered, X-ray amorphous materials that approximate destinezite in composition. Diadochite/destinezite may be an unrecognized component of soils where weathering of pyrite and apatite has occurred and pH is low. It may thus be a significant sink for phosphorus and sulfur in such soils.
Mineralogical Interference on Kaolinite Crystallinity Index Measurements
Authors: Aparicio Patricia , Galán Emilio 
Published: August 2006

AbstractThis study examines the influence of minerals and amorphous phases associated with kaolin and kaolinitic rocks on kaolinite crystallinity indices (KCI) derived from X-ray diffraction (XRD) data in order to select the best index for systematic studies of commercial kaolins or geological sequences. For this purpose, 8 kaolins of differing structural order were chosen and used to prepare mixtures containing different weight fractions of quartz, feldspar, illite, smectite, chlorite, halloysite and iron hydroxide and silica gels. An additional 17 samples of kaolin were also studied to test the results and evaluate the restrictions. KCIs used included Hinckley (HI), Range and Weiss (QF), Liètard (R2), Stoch (IK), Hughes and Brown (H&B) and Amigó et al. (full width at half maximum, FWHM), and the “expert system” of Plançon and Zacharie.Based on more than 15,000 KCI determinations, the HI and QF are influenced by quartz, feldspar, iron hydroxide gels, illite, smectite and halloysite. IK can be used in the presence of quartz, feldspar and iron hydroxide and silica gels. Also, R2 is the only KCI that could be measured in the presence of halloysite; FWHM indices should not be used in the presence of chlorite and/or halloysite; and H&B should only be used with pure kaolinite samples. The “expert system” of Plançon and Zacharie is strongly affected by the presence of other mineral phases, particularly with more than 25% of well-ordered kaolinite. Their system is less sensitive to other mineral phases when only disordered kaolinite is present, and it should not be used with kaolinite of medium order-disorder because the well-ordered phase is present in an inappreciable proportion (<10%). KCI is only measurable in kaolinitic rocks if kaolinite is >20 wt% and the precision increases with an increase in the quantity of kaolinite. In all cases, the reliability will depend on the other minerals present. When a KCI can be measured accurately, the others can be obtained by using the empirical relationships reported in this paper.
Colloid Chemical Control of Kaolinite Properties Related to Ceramic Processing
Authors: Pavlova Lyudmyla A. , Wilson Michael J. 
Published: August 2006

AbstractExperimental data on structure formation in highly concentrated aqueous dispersions of kaolinite were analyzed using rheological models. The physicochemical properties of the clay mineral surface were studied during heating at a range of temperatures, and correlation of acid-base properties with physicomechanical characteristics of the spatial structures formed during heating was obtained. It was shown that interparticle interactions and plastic yield mechanisms under load are dependent upon interfacial phenomena. A method for estimating optimal structural parameters was developed for semidry dispersions, enabling regulation of physicochemical and mechanical properties of ceramic mixtures during processing.