bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zeolite Mineral Reactions in a Tuff in the Laney Member of the Green River Formation, Wyoming
Authors: Ratterman Nancy G. , Surdam Ronald C. 
Published: August 2006

AbstractTwo diagenetic stages of zeolitic alteration were recognized in a study of a thin bed of rhyolitic ash that was deposited in Eocene Lake Gosiute (Laney Member of the Green River Formation). The ash bed can be traced for 30 km along strike and represents a single volcanic event. The bed was not buried deeply (<100°C), and originally it was compositionally homogeneous. Initially, the bed altered to clino-ptilolite, heulandite, an intermediate phase between these two zeolites, and mordenite. These early reactions involved the hydration and solution of glass by saline, alkaline solutions and the subsequent precipitation of zeolites. The variation in zeolite mineralogy is due to differences in interstitial fluid chemistry that resulted from either fluctuations in lake-water chemistry or the proximity of spring discharge. These reactions, exclusive of the addition of H2O, involved only minor amounts of mass transfer over very small distances. Later, after burial, the early-formed zeolites reacted with upward moving sodium carbonate brines that were produced by dewatering of underlying evaporite deposits. The sodium carbonate brines, in equilibrium with trona and nahcolite, elevated the activity of Na+ and produced analcime. These later dehydration reactions involved significant mass transfer.
Synthesis of a 10-Å Hydrated Kaolinite
Authors: Costanzo P. M. , Giese R. F. , Clemency C. V. 
Published: August 2006

AbstractHydrated kaolinite (d(001) = 10 Å) can be synthesized by mild heating of a kaolinite-organic suspension, allowing time for the clay to be intercalated by the organic solvent, and then dissolving a fluoride salt in the liquid. After mild heating of the suspension, the salt and organic solvent are removed by repeated water washings. The kaolinite retains interlayer water in the form of a 10-Å kaolinite hydrate. The influence of the intercalating agent, type of salt, concentration of salt, and the time of treatment on the synthesis of 10-Å hydrate was examined for several kaolinites. The most effective salt is NH4F; much smaller yields were obtained using KF and RbF. Not all organic molecules gave high yields of the hydrate; dimethyl sulfoxide, formamide, and hydrazine worked well but N-methyl formamide did not. The reaction between clay and salt resulted in the replacement of some hydroxyls by fluoride. This replacement was rapid; after 1 min of fluoride treatment a substantial yield of hydrate was obtained. The intercalation step separated the layers and also disordered the kaolinite, facilitating the F for OH replacement at or near crystallite edges. This replacement weakens the interlayer bonding at the edges and thereby reduces the possibility of layer collapse and attendant dehydration.
Adsorption of Molybdate Anion (MoO42−) by Sodium-Saturated Kaolinite
Authors: Phelan Patrick J. , Mattigod Shas V. 
Published: August 2006

AbstractAdsorption of Mo(VI) on 2-0.2-μm size fraction of sodium-saturated kaolinite at 25 ± 2°C and at a constant pH of 7.00 ± 0.05 was studied. The kaolinite sample was pretreated to remove any surface oxide and hydroxide coatings. The initial concentrations of Mo in solution ranged from 1 to 11 mg/liter in a NaClO4 background electrolyte at a constant ionic strength of 0.09 ± 0.01. Calculations of speciation using the GEOCHEM computer program indicated that under experimental conditions Mo(VI) was mainly in the MoO42− form. The experimental conditions were also shown to fulfill the requirements for applying the Langmuir equation in interpreting adsorption data. The Langmuir parameter for the adsorption maximum, n°, and the affinity parameter, KMoO42−−ClO4− were computed to be 3.33 × 10−4 mole/ mole of adsorbent and 5.969 × 105, respectively. The large affinity parameter indicated that the Na-saturated kaolinite surface has a very high affinity for MoO42− ions relative to ClO4− ions.
Tris(Acetylacetonato)Silicon(IV) Binding to Montmorillonite and Hydrolysis to Interlayer Silicic Acid
Authors: Manos Charles G. , Mortland M. M. , Pinnavaia Thomas J. 
Published: August 2006

AbstractThe reactions of the tris(acetylacetonato)silicone(IV) cation (Si(acac)3+) with Na+-, Mg2+-, and Co2+-exchange forms of hectorite and montmorillonite have been investigated to understand better the formation process of clays pillared by silicic acid. In acetone as the solvating medium, Si(acac)3+ binds to the Na+- and Mg2+-clays with the desorption of only a small fraction (~5%) of the initial exchange cation, suggesting that the complex binds as the ion pair [Si(acac)3+][Cl−]. With the Co2+-clays, however, the exchange cation is desorbed quantitatively, and Si(acac)3+ binding is accompanied by the formation of an acetone-solvated CoCl2 solution complex which helps to drive the ion-exchange reaction. Thus, Co2+-smectites react with Si(acac)3+ in acetone to produce homoionic Si(acac)3+ intercalates, whereas Na+-and Mg2+-smectites produce mixed-ion intercalates. The interlayer hydrolysis of Si(acac)3+ to silicic acid in the homoionic Si(acac)3+- and mixed-ion Na+/Si(acac)3+- and Mg2+/Si(acac)3+-exchange forms of montmorillonite films is diffusion controlled. In water as the solvating medium, the reaction of Si(acac)3+ with Mg2+- or Co2+-montmorillonite results in the desorption of the exchange cations on a time scale which is comparable to that observed for the solution hydrolysis of Si(acac)3+. Thus, the precipitation of silicic acid from aqueous solution competes strongly with the formation of interlayer silicic acid. With aqueous Na+-montmorillonite dispersions, however, a significant fraction of the exchange cations desorbed rapidly upon Si(acac)3+ binding, and the formation of interlayer silicic acid is favored over the precipitation of Si(OH)4.
Saponite from Near Ballarat, California
Authors: Post J. L. 
Published: August 2006

AbstractWhite saponite occurs in joints and open fracture zones in metamorphosed dolomitic limestone near Ballarat, California. The saponite appears to have formed by hydrothermal alteration, possibly during Pliocene times. The material shows a 06l X-ray powder diffraction peak at 1.529 Å, A12O3 and MgO contents of about 4.4 and 23.5%, respectively, and a half-cell octahedral atoms summation value of about 2.82. The saponite appears to consist of a single, uniform clay species; the main impurities are fine shards of diopside and tremolite. The infrared and thermal properties of the Ballarat saponite are similar to those of the Allt Ribhein saponite. It has a lower water-holding capacity than montmorillonite and is characterized by lower Atterberg limits and expansion pressures and higher compaction densities. The apparent density of the saponite, 2.865 g/cm3, is greater than that of montmorillonite. This saponite is available from the Source Clays Repository of The Clay Minerals Society.
Influence of Chloride on the Formation of Iron Oxides From Fe(II) Chloride. I. Effect of [Cl]/[Fe] on the Formation of Magnetite
Authors: Taylor R. M. 
Published: August 2006

AbstractThe formation of fine-grained magnetite (~0.1 μm) at pH 7 and 25°C from aeration of Fe(II) chloride solutions is presented. The magnetite converted at 105°C to maghemite with poorly developed superstructure lines. Under the experimental conditions employed, as the initial [Cl]/[Fe] ratio was increased from the stoichiometric value of 2, the final product contained increasing amounts of lepidocrocite. The degree of crystallinity of this phase, as measured by the width at half height of the 020 X-ray diffraction peak, also increased with this ratio. The hydrolysis rate (base consumption to maintain pH) showed a plateau whose position and extent changed with the initial [Cl]/[Fe] ratio. Through this plateau region the Eh decreased to a minimum value the position of which was directly related to the [Cl]/[Fe] value. The formation of lepidocrocite rather than magnetite is likely due to the high [Cl] where there would be increased difficulty for neighboring OH to condense and eliminate H2O. The formation of Fe-O-Fe bonds in this condensation would be impeded by Cl substitution for OH either in the first formed green rust stage or during its oxidation.
Regular Solution Site-Mixing Model for Chlorites
Authors: Stoessell R. K. 
Published: August 2006

AbstractActivity expressions are presented for a six end-member, regular solution, site-mixing model for chlorites. The end members are ideal 14-Å chlorites for which experimental stability data are lacking. Estimates were made of the standard state 25°C and 1 bar molar 3rd law entropies, volumes, and the Maier-Kelley heat capacity coefficients. Experimental stability data from the literature for 14-Å chlorites were used with different sets of exchange energies, for cations on adjacent sites, to compute estimates of the standard state chemical potentials of the end members at 25°C and 1 bar. More experimental data are needed for an adequate definition of the exchange energies and the standard state chemical potentials. The model was applied to diagenesis in clastic reservoirs. Aqueous activity ratios of Mg2+:Fe2+ were computed as an equilibrium function of the corresponding molar ratios in authigenic chlorites. The aqueous activity ratio was independent of the chlorite Al content at a constant molar ratio of Mg2+:Fe2+ in the chlorite. The model predicts a wide range of molar Mg2+:Fe2+ ratios in authigenic chlorites in equilibrium with reservoir fluids. Trends in these molar ratios should be independent of the Al content in the chlorites. The model can be applied directly to 7-Å chlorites when experimental data become available to estimate the various thermodynamic parameters of the 7-Å end members.
Mineralogy and Genetic Relationships of Tonstein, Bentonite, and Lignitic Strata in the Eocene Yegua Formation of East-Central Texas
Authors: Senkayi A. L. , Dixon J. B. , Hossner L. R. , Abder-Ruhman M. , Fanning D. S. 
Published: August 2006

AbstractA kaolinite-rich bed (tonstein) and an associated bentonite in the upper part of Yegua Formation at College Station, east-central Texas, were formed by in situ weathering processes in a late Eocene swamp. X-ray powder diffraction, infrared spectroscopy, petrographic studies, and scanning and transmission electron microscopy not only show that dioctahedral smectite and coarsely crystalline kaolinite are the dominant minerals in the bentonite and tonstein, respectively, but that cryptocrystalline halloysite and kaolinite are localized along the weathering front (transitional zone) between the tonstein and the bentonite. As weathering progressed, the cryptocrystalline minerals gradually recrystallized to yield the coarse books and vermicular growths of kaolinite characteristic of the tonstein.Small amounts of cristobalite, sanidine, and euhedral zircon crystals with liquid or gaseous inclusions accord with the formation of the bentonite by alteration of volcanic ash. Clinoptilolite in the lignitic layer and sandstone below the bentonite probably formed from ions that were released during alteration of the volcanic materials to smectite, but clinoptilolite in the tonstein and overlying strata appear to have formed after kaolinization of the bentonite.
Chemisorption of Cu(II) and Co(II) on Allophane and Imogolite
Authors: Clark C. J. , McBride M. B. 
Published: August 2006

AbstractAdsorption of Cu2+ and Co2+ by synthetic imogolite, synthetic allophanes with a range of SiO2/ Al2O3 ratios, and allophanic clay fractions from volcanic ash soils was measured in an ionic medium of 0.05 M Ca(NO3)2. The effect of pH (and metal concentration) on adsorption was qualitatively similar for the synthetic and natural allophanes with relatively minor changes in behavior caused by variable SiO2/Al2O3 ratios. Cu and Co were chemisorbed by allophane at pH 5.0–5.5 and 6.9–7.2 (pH values for 50% adsorption level), respectively, with concomitant release of 1.6–1.9 protons/metal ion adsorbed. Quantitatively, adsorption by imogolite was less than that by the allophanes, presumably because of fewer sites available for chemisorption on the tubular structure of imogolite. Electron spin resonance studies of the imogolite and allophanes revealed that Cu2+ was adsorbed as a monomer on two types of surface sites. The preferred sites were likely adjacent AlOH groups binding Cu2+ by a binuclear mechanism; weaker bonding occurred at isolated AlOH or SiOH groups. These chemisorbed forms of Cu2+ were readily extracted by EDTA, CH3COOH, and metals capable of specific adsorption, but were not exchangeable. In addition, the H2O and/or OH− ligands of chemisorbed Cu2+ were readily displaced by NH3, with the formation of ternary Cu-ammonia-surface complexes.
Effects of Reduction and Reoxidation of Structural Iron on the Surface Charge and Dissolution of Dioctahedral Smectites
Authors: Stucki Joseph W. , Golden D. C. , Roth Charles B. 
Published: August 2006

AbstractThe effect of Fe oxidation state on the surface charge (CEC) and solubility of smectites were studied using the <2-μm, Na+-saturated fraction of an Upton, Wyoming; a Czechoslovakian; and a New Zealand montmorillonite; and a Garfield, Washington, nontronite. The reduction of structural Fe3+ in the octahedral sheet of each clay produced a net increase in the negative surface charge of the clay. The observed cation-exchange capacities deviated from the linear relationship predicted by charge-deficit calculations, assuming changes only in the Fe2+/Fe3+ ratio, and reversibly followed Fe reduction according to a 2nd-degree polynomial function. The deviations suggest reversible changes in mineral structure and composition during Fe reduction.These clays were susceptible to partial dissolution in citrate bicarbonate (CB) and citrate-bicarbonate-dithionite (CBD) solutions. Small amounts of Fe and Si dissolved as a result of Fe reduction in CBD, but affected <1% of the total clay mass except for the Czechoslovakian clay in which 2% of the clay dissolved. Although slightly more Fe dissolved than Si, no change in surface charge was noted. Almost no dissolution of these elements was detected in CB solution. In contrast, significant Al was detected in the CB solution, suggesting a heterogeneous dissolution mechanism. The CEC, however, was unchanged by the CB treatment. These results may be explained by the adsorption of hydrogen ions into the vacated Al3+ sites in the mineral structure. Dissolution seems to have been independent of the effects of Fe oxidation state on surface charge.
Nontronite in a Deep-Sea Core from the South Pacific
Authors: Singer A. , Stoffers P. , Heller-Kallai L. , Szafranek D. 
Published: August 2006

AbstractSmectite close to the pure Fe end member of the nontronite-beidellite series was found in the fine clay separated from a 354-cm deep sediment core in the southwestern Pacific Basin. The mineral has a b-axis of 9.09 Å and an unusually low dehydroxylation temperature of 454°C and is composed of sheaves of fibers less than 50 Å wide. Its charge density is 5.09 × 10~4 esu/cm2. The charge originates mainly from the presence of 18% of the total Fe in tetrahedral positions, as determined by Mössbauer analysis. Slight deviations of the infrared spectra from those reported for nontronites are probably due to the presence of more octahedral Mg. The presence of authigenic quartz in the same sample permits some speculation on the concentration of dissolved silicon during nontronite genesis. A δ18O value of 26 ± 0.3‰ indicates a temperature of formation of about 22°C. The Sr isotope ratio suggests that the nontronite formed at least 12 million years ago.
Static and Dynamic Structure of Water in Hydrated Kaolinites. I. The Static Structure
Authors: Costanzo P. M. , Giese R. F. , Lipsicas M. 
Published: August 2006

AbstractFour hydrates with d(001) = 8.4, 8.6, and 10 Å (two types) were synthesized by intercalating kaolinite with dimethylsulfoxide and treating the intercalated clay with fluoride ions. X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, and kinetics of dehydration experiments have led to the identification of two types of interlayer water. One type of water (hole water) is situated in the ditrigonal holes of the silica tetrahedral surface; the second type (associated water) forms a discontinuous layer of mobile water. The 8.4-Å and 8.6-Å hydrates have only hole water, whereas the two synthetic 10-Å hydrates and halloysite(10Å) contain both hole and associated water. The hole water is probably hydrogen bonded to the basal oxygens of the silica tetrahedra or, in the 8-Å hydrates when fluorine exchanges for inner-surface hydroxyls, the water molecules may reorient and form stronger hydrogen bonds to the fluorine. Associated water forms water-water hydrogen bonds approximately equal in strength to liquid water but is less strongly bonded to the clay surfaces than hole water. At room temperature the hole and associated water in the 10-Å hydrates do not form an ice-like structure.
Polytypism of Micas. II. Classification and Abundance of MDO Polytypes
Authors: Ďurovič S. , Weiss Z. , Backhaus K.-O. 
Published: August 2006

AbstractThe maximum-degree-of-order (MDO) polytypes in all three mica families have been classified into two subfamilies and five homomorphous MDO groups according to their superposition structure and the YZ projection of their structure, respectively. This classification, which is closely related to the diffraction pattern of micas, can be derived directly from the fully descriptive polytype symbols and facilitates the calculation of the identification diagrams as well as the recognition of the relations of homomorphy between the three mica families. All mica structures refined so far by the least-squares method according to the present standards, are those of MDO polytypes.
Relation of Infrared, Crystallochemical, and Morphological Properties of Al-Substituted Hematites
Authors: Barron V. , Rendon J. L. , Torrent J. , Serna C. J. 
Published: August 2006

AbstractSynthetic Al-hematites prepared from ferrihydrites, at low (∼ 100°C) and high (400° and 800°C) temperatures were studied for their morphological, crystallochemical, and infrared (IR) characteristics. Low-temperature Al-hematites had a platy morphology (the plate thickness was inversely related to amount of Al substitution), and the high temperature Al-hematites showed a poorly defined morphology due to interparticle sintering. In the low-temperature Al-hematites shifts in the IR mode frequencies were noted and could be partly explained by a shape factor that was deduced from particle morphology. The intrinsic effect of Al substitution, however, was to produce shifts of as much as 10–15 cm−1 for the highest Al substitution (∼ 16%). Similar shifts were observed for the high-temperature hematites in which morphology was not appreciably affected by Al substitution.
Pillaring Processes of Smectites with and Without Tetrahedral Substitution
Authors: Plee D. , Gatineau L. , Fripiat J. J. 
Published: August 2006

AbstractPillaring of montmorillonite and beidellite with aluminum polyhydroxypolymer takes place first by the saturation of the cation-exchange capacity by monomeric and/or dimeric aluminum hydroxide species and then the intercalation of the so-called Al13-polyhydroxypolymer. The clay slurry must have a solid concentration greater than 0.01% (w/w) to produce a basal spacing of about 18 Å. Sizeable clay tactoids must therefore exist in the slurry in order to produce a turbostratic structure ordered along the c axis. The main difference between pillared montmorillonite and pillared beidellite seems to be a more ordered distribution of pillars within the interlamellar space of the clays that are rich in tetrahedral substitutions. Recent 27Al and 21Si high-resolution nuclear magnetic resonance data suggest that this higher degree of ordering results from the reaction of the aluminic pillars and the clay sheet near the sites of the tetrahedral substitutions.
Chemical and Morphological Evidence for the Conversion of Smectite to Illite
Authors: Inoue Atsuyuki , Kohyama Norihiko , Kitagawa Ryuji , Watanabe Takashi 
Published: August 2006

AbstractThe continuous conversion of smectite to illite in samples from the Shinzan hydrothermal alteration area of Japan has been examined by X-ray powder diffraction (XRD) and transmission (TEM) and analytical transmission electron microscopy (AEM). TEM shows that randomly interstratified illite/ smectite (I/S) containing 100-50% expandable layers exhibits a flakey shape, whereas regularly and partially ordered interstratified I/S having 50-0% expandable layers exhibits a lath-like habit. An early- formed lath of regularly interstratified I/S is typically <35 Å in thickness and 300–500 Å in width; these dimensions gradually increase with decreasing percentage of expandable layers. XRD shows that the lathshaped I/S has a 1M polytype mica structure. AEM shows that the interlayer K content of flakey I/S increases monotonously with decreasing percentage of expandable layers in the range 100-50% expandable layers, whereas the interlayer K content of lath-shaped I/S increases along a different trend from that for the flakey I/S in the range 50-0% expandable layers. These observations suggest that randomly interstratified I/S is fundamentally smectite that is undergoing K-fixation and dissolution and that regularly and partially ordered interstratified I/S are immature illite which is still growing. Consequently, they suggest a mechanism for the hydrothermal smectite-to-illite conversion that is based on the K-fixation in and dissolution of smectite and the precipitation and growth of thin illite particles. Furthermore, these data suggest that the kinetics of smectite dissolution and illite growth are the most important factors controlling the smectite-to-illite conversion.
Alteration of Phlogopite to Corrensite at Sharbot Lake, Ontario
Authors: De Kimpe C. R. , Miles N. , Kodama H. , Dejou J. 
Published: August 2006

AbstractA low-charge corrensite, i.e., a regular 1:1 interstratified smectite/chlorite was found in veins and fissures of an extensively fractured dolomite south of Perth, Ontario, Canada. Total chemical analysis indicated that the mineral was trioctahedral, having a structural formula corresponding to:
(Ca0.17)(Mg7.36Al0.90Fe3+ 0.45Fe2+ 0.42)VI(Si6.06Al1.94)IVO20(OH)10.The coefficient of variation (CV) of the d(00l) spacings calculated for the mineral from X-ray powder diffraction data was 0.42, well below the maximum recommended value for corrensite, 0.75. The corrensite coexists with phlogopite, which is present as small (~0.5 mm) crystals throughout the rock and locally as large (~5 cm) crystals in pegmatitic veins. Microscopic observatiofls of large phlogopite crystals partially altered to corrensite suggest that corrensite formed at the expense of phlogopite by hydrothermal alteration.
Preparation and Characterization of Bidimensional Zeolitic Structures Obtained from Synthetic Beidellite and Hydroxy-Aluminum Solutions
Authors: Schutz A. , Stone W. E. E. , Poncelet G. , Fripiat J. J. 
Published: August 2006

AbstractBeidellite was synthesized hydrothermally from a noncrystalline gel at 320°C and 130 bar pressure. The beidellitic character of the product was verified by infrared spectroscopy on the NH4+-exchanged form. Intercalation was achieved with hydroxy-aluminum solutions having different OH/Al molar ratios. The solutions were investigated by several methods, including 27Al nuclear magnetic resonance. Essentially, two Al species were detected: monomelic Al and a polymerized form containing Al in four-fold coordination. This latter species was found to be selectively fixed in the interlamellar region, which resulted in a stable spacing of 18 Å at 110°C and 16.2 Å at 700°C. The pillared beidellites had specific surface areas of > 300 m2/g, mainly due to micropores. Both Brönsted and Lewis acid sites were evidenced by infrared spectroscopy using pyridine as a probe molecule.