bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Diagenetic to Low-Grade Metamorphic Evolution of Matrix White Micas in the System Muscovite-Paragonite in a Mudrock from Central Wales, United Kingdom
Authors: Li Gejing , Peacor Donald R. , Merriman R. J. , Roberts B. 
Published: August 2006

AbstractTwo orientations of white micas with subordinate chlorite have been observed in a fine-grained (50 Å to 2 μm) matrix of a Silurian lower anchizonal mudrock from central Wales: one parallel to bedding and one parallel to cleavage that is approximately 30°-50° to bedding. Bedding-parallel micas consist of small (50-200 Å thick) deformed packets (1Md polytype) and larger (100 Å-2 μm) strain-free grains (2M1 polytype). All strained micas and some strain-free grains have compositions varying from Mu86Pg14 to Mu58Pg42, intermediate to muscovite and paragonite, and falling within the Mu-Pg solvus. Individual packets of layers are chemically homogeneous and some of them give only one set of 00l reflections (d ≈ 19.6 Å). Micas with such intermediate compositions are metastable. Some packets of coarse, strain-free micas have compositions of approximately Mu93Pg7 or Mu11Pg89. Split pairs of 00l reflections with d-values of 20 Å and 19.6 Å, and 20 Å and 19.2 Å, respectively, were observed in some SAED patterns, suggesting coexistence of muscovite and intermediate Na/K mica (∼Mu60Pg40), and of discrete muscovite and paragonite, consistent with the splitting of the basal reflections of micas as observed in bulk-rock XRD patterns. Cleavage-parallel micas (2M1 and 3T polytypes) occur as strain-free large grains (200 Å to 2 μm) of discrete muscovite (Mu100Pg0) and paragonite (Mu6Pg94), often with subhedral to euhedral cross-sections.The data suggest that bedding-parallel metastable micas with disordered interlayer K and Na were initially derived from alteration of smectite during burial diagenesis. They subsequently underwent dissolution, with crystallization of more evolved bedding-parallel micas during deep burial. Discrete grains of stable muscovite and paragonite then crystallized in the cleavage orientation through tectonic stress-induced dissolution of bedding-parallel matrix micas. Combined XRD and TEM/AEM data further show that the so-called 6:4 ordered mixed-layer paragonite/muscovite actually corresponds to cation-disordered, homogeneous mica of intermediate composition.
A Simple Technique for Identification of One-Dimensional Powder X-Ray Diffraction Patterns for Mixed-Layer Illite-Smectites and other Interstratified Minerals
Authors: Drits V. A. , Varaxina T. V. , Sakharov B. A. , Plançon A. 
Published: August 2006

AbstractA very simple technique is proposed for a quantitative or semiquantitative interpretation of X-ray diffraction (XRD) patterns for two-component mixed-layer structures. It is suitable for a determination of the Reichweite (R) values and proportions of component layers from graphical simulations of basal peak positions for mixed-layer structures with definite layer types. This technique can be successfully used for illite-smectites, but the accuracy of the results obtained for other mixed-layer structures is somewhat lower. In addition to the graphical technique, simple linear relationships are proposed for the calculation of layer proportions. Such relationships can be easily obtained for any mixed-layer structure with any R and any thicknesses of interstratified layers.Structural parameters reported in the literature for mixed-layer illite-smectites, kaolinite-smectites, etc., were used to check the reliability of the method presented. It is concluded that the technique works well and produces parameters that are in agreement with those published.
The Composition and Origin of Vanadium-Rich Clay Minerals in Colorado Plateau Jurassic Sandstones
Authors: Meunier J. D. 
Published: August 2006

AbstractThe composition and origin of vanadium-bearing clay minerals in the Jurassic (Morrison and Entrada Formations) sandstones of the Colorado Plateau are reassessed using microanalyses (microprobe and scanning electron microscope). The main V-clays are authigenic illite and chlorite of various petrologic habits: clay casts and matrix, pore lining, replacement of detrital grains. The chemical composition of the V-clays is similar in three different localities in the Morrison Formation separated by about 50 km, suggesting that the V-clays are the result of a large regional event. In both illite and chlorite, Al and V are inversely correlated, showing that V replaces Al in the octahedral position. The chlorite contains a complex mixture of divalent and trivalent cations that cannot fit within a sudoite structure. A classification of V-micas is proposed that employs V3+/sum of the octahedral cations vs. the sum of the interlayer charges. V-illite and roscoelite from the Colorado Plateau are characteristic of diagenetic/hydrothermal environments. For a given locality the composition of the V-clays does not vary with habit, showing that these minerals formed at thermodynamic equilibrium.
Clay Aerosols and Arctic Ice Algae
Authors: Tazaki Kazue , Fyfe William S. , Iizumi Shigeru , Sampei Yoshikazu , Watanabe Hiroaki , Goto Masatoshi , Miyake Yasuyuki , Noda Shuji 
Published: August 2006

AbstractThe red snow algae species found in snow at Resolute, Canadian Arctic, is a unicellular Chlamydomonas nivalis. Investigations by SEM-EDX, TEM, FT-IR, GC and GC-MS suggest that clay aerosols may provide nutrients for these unique systems. The clays provide P, S, K, Si, Ca, and Mg. Soot is also present and halite is very common. This salt probably plays a significant role in lowering the freezing temperature. The red snow algae is coated by a sticky thin film composed of both organic membrane material and inorganics consisting of mica and smectite. Green algae rich in Ca are involved in active photosynthesis while red algae are in a resting stage. Protamine, stearic acid, and decanoic acid were found at Ca-rich green cells while carminic acid and nopalcol BR-13 were found at Ca-poor red cells. The cell wall of red algae is composed of protein with cellulose. The major fatty acides in cells are all of even-carbon species with maximum concentrations of palmitic acid, stearic acid, and behenic acid, suggesting normal chemistry of algae species without C22. High concentration of n-alkanes with n-C24 is a characteristic component in this red snow algae, suggesting the presence of hydrocarbons that could be derived from the Arctic cold desert and/or organic debris of wind-transported bacteria. It is likely that such organic and inorganic matter provide the nutrient sources for the red snow algae in ice.
Study of the Nature of Acid Sites of Montmorillonites Pillared with Aluminium and Oligosilsesquioxane Complex Cations. 1. Brönsted Acidity
Authors: Zubkov S. A. , Kustov L. M. , Kazansky V. B. , Fetter G. , Tichit D. , Figueras F. 
Published: August 2006

AbstractTwo samples, obtained by pillaring a Wyoming montmorillonite with hydroxy aluminium and oligosilsesquioxane cations, were studied by stepwise thermal desorption of ammonia and by highly sensitive diffuse reflectance IR-spectroscopy. For both clays, the adsorption of ammonia shows a total number of acid sites equal to 0.35 meq/g, with acid strengths comparable to that of HY zeolites. By IR reflectance spectroscopy, Brönsted acid sites with an acid strength comparable to that of bridging hydroxyls in zeolites were found in Al samples but not on Si-montmorillonites. These sites were characterized by an overtone band at 7100 cm-1 and an activity for ethylene oligomerization at 300 K.
Microfabric of Altered Ash Layers, ODP Leg 131, Nankai Trough
Authors: Tribble Jane S. , Wilkens Roy H. 
Published: August 2006

AbstractSamples of ash layers and associated background sediments from Site 808 of ODP Leg 131 in the Nankai Trough accretionary prism were analyzed for changes in mineralogy, porosity and micro-fabric associated with alteration of volcanic ash. Ash layers range from incipient stages of alteration and dissolution to complete alteration to clay minerals and clinoptilolite. Ash layers contain greater abundances of total clay minerals and lower percentages of quartz than do surrounding background hemipelagic sediments. The clay-sized fraction of ash layers is dominated by pure dioctahedral smectite, whereas the background sediments contain primarily illite and chlorite with minor amounts of smectite. Analysis of microfabric revealed dramatic changes in the distributions and abundances of grains and pores during ash alteration. The relative abundances of large pores, grains, and matrix material were quantified on digital back-scattered electron images (BSEI) of ash layer and background sediment samples. During burial, the abundant glass shards of shallow ash layers are initially altered, presumably to smectite. Subsequent dissolution of the glass leaves open, shard-shaped pores, resulting in increased porosities. With greater burial, these pores are filled with clinoptilolite. Although the presence of ash and its alteration products clearly influences sediment physical properties, there is no apparent correlation of the abundance of ash or its alteration products with the formation of thrust faults or other structures within the Nankai Trough accretionary prism.
Comparison of Four Elemental Mass Balance Methods for Clay Mineral Quantification
Authors: Kolka Randall K. , Laird David A. , Nater Edward A. 
Published: August 2006

AbstractThe quantification of the relative mineralogical composition of clay mixtures by powder X-ray diffraction or chemical mass balance methods has been severely hampered by a lack of representative standards. The recent development of elemental mass balance models that do not require standards for all minerals in the mixture may help circumvent this problem. These methods, which are based on the numerical optimization of systems of non-linear equations using the Marquardt algorithm, show promise for mineral quantification. The objective of this study is to make a preliminary assessment of the accuracy of these methods and to compare them to linear models that require standards for all mineral phases. Methods 1 and 2 are based on weighted average solutions to simultaneous linear equations solved for single samples with known standards. Solutions were achieved by a matrix decomposition algorithm and the Marquardt algorithm, respectively. Methods 3 and 4 are based on a set of simultaneous non-linear equations with reduced non-linearity solved by least squares optimization based on the Marquardt algorithm for multiple samples. Illite and halloysite compositions were fixed in Method 3, only the halloysite composition was fixed in Method 4. All models yielded relative weight fractions of the three mineral components; additionally, Methods 3 and 4 yielded compositions of smectite, and smectite and illite, respectively. Ten clay mixtures with varying proportions of the <0.2μm size fraction of three different reference clays (Wyoming bentonite, Fithian illite, and New Bedford halloysite) were prepared gravi-metrically and analyzed by inductively coupled plasma-atomic emission spectroscopy. Accuracy of the four methods was evaluated by comparing the known mineralogical compositions of the mixtures with those predicted by the models. Relative errors of 5 and 10% (randomly +/-) were imposed on the elemental composition of the smectite standard to simulate errors due to lack of good standards. Not surprisingly, the accuracy of Methods 1 and 2 decreased rapidly with increasing error. Because Methods 3 and 4 optimized for the smectite composition and only used it for an initial guess, they were unaffected by the level of introduced error. They accurately quantified the mineralogical compositions of the mixtures and the elemental compositions of smectite, and smectite and illite, respectively.
Comparison of Pedogenic and Sedimentary Greigite by X-ray Diffraction and Mössbauer Spectroscopy
Authors: Stanjek Helge , Murad Enver 
Published: August 2006

AbstractGreigites from a gley and a Tertiary sediment were investigated by X-ray diffraction and Mössbauer spectroscopy. The cell-edge length a of 9.8639 Å ± 0.0003 Å for the soil greigite was significantly smaller than that of the sedimentary greigite (9.8737 Å ± 0.0004 Å), but both cell-edge lengths were smaller than the value given on JCPDS card #16-713 (9.876 Å). Both greigites had 440 as strongest peak rather than 311 (as indicated on JCPDS card #16-713), but the other relative intensities did not deviate from the values given on this card within experimental error. Mean X-ray diffraction coherence lengths of 23 ± 2 nm for the soil greigite and of 60 ± 5 nm for the sedimentary greigite suggest superparamagnetic behavior. Mössbauer spectra nevertheless comprised two sextets with hyperfine fields of about 31.2 T (tetrahedral sites) and 30.7 T (octahedral sites), which resemble published values. It is postulated that aggregation may play an important role in determining the magnetic properties of the described samples.
Preparation and Characterization of an 8.4 Å Hydrate of Kaolinite
Authors: Tunney Jim , Detellier Christian 
Published: August 2006

AbstractA stable 8.4 Å hydrate of kaolinite was prepared by exchanging ethylene glycol for water in the 10.8 Å intercalate of ethylene glycol in kaolinite. The hydrate of kaolinite was characterized by XRD, FTIR and TGA/DSC. From the TGA data, one can estimate that there is 0.60 water molecule per Al2Si2O5(OH)4 units. The IR data suggest a similarity of the local environment of the intercalated water in this 8.4 Å hydrate of kaolinite and the 8.4 Å hydrate of nacrite previously described by Wada (1965).
Gas Chromatographic Separation of Linear Hydrocarbons on Microporous Organo-Smectites
Authors: Lao Hongbai , Detellier Christian 
Published: August 2006

AbstractA series of organo-montmorillonites and organo-hectorites was prepared by complete ion-exchange from the pure sodium form of the parent smectites. The organic cations were tetramethylammonium, trimethylated quaternary ammonium derivatives of the lysine and of the ornithine methyl esters, quaternarized polyammonium cations, or tetraphenylphosphonium (TPP). These organo-smectites were used as packing material for gas chromatography columns. Mixtures of light hydrocarbons (methane to n-butane; “C1” to “C4”) could be separated. The degree of separation depends on the presence of micropores or of organophilic mesopores. The BET surface area, the micropore and mesopore volumes, as well as the size distribution of micropores and mesopores were measured for several systems. As a general trend, the retention times of the light hydrocarbons decrease with an increase of the micropore volume. In the case of TPP-montmorillonite, characterized by a large mesopore volume but for which no microporosity could be detected, separation of longer linear hydrocarbons (n-pentane to n-octane) could also be achieved.
The Al Pillaring of Clays. Part II. Pillaring with [Al13O4(OH)24(H2O)12]7+
Authors: Schoonheydt Robert A. , Leeman Hugo , Scorpion Anita , Lenotte Ingrid , Grobet P. 
Published: August 2006

AbstractHectorite and saponite are exchanged with [Al13O4(OH)24(H2O)12]7+ and the amount of Al3+ adsorbed and Na+ released are followed as a function of the exchange conditions. On saponite the reaction is a pure ion exchange with 2–2.15 mmol Al3+/g adsorbed and release of 0.80 mmol Na+/g. On hectorite the ion exchange is accompanied by supplementary hydrolysis-polymerization of Al13. When excess Al is offered in the form of Al13, ion exchange is incomplete and is accompanied by precipitation and polymerization of Al13 on the surface of both hectorite and saponite. The typical spacing of 1.8 nm is developed after washing, when at least 1.3–1.4 mmol Al3+/g is adsorbed. Above a loading of 2.2–2.5 mmol/g the 1.8 nm spacing is obtained without washing. Only pillared saponite with a loading of at least 1.9 mmol Al3+/g is thermally stable up to 550°C.
Formation of Hydrotalcite-like Compounds During R7T7 Nuclear Waste Glass and Basaltic Glass Alteration
Authors: Abdelouas A. , Crovisier J. L. , Lutze W. , Fritz B. , Mosser A. , Müller R. 
Published: August 2006

AbstractAlteration experiments have been performed using RTT7 and synthetic basaltic glasses in MgCl2−CaCl2 salt solution at 190°C. The duration of experiments ranged from 0.25 to 463 days. The alteration products were studied by Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD) and Electron Spectrometry for Chemical Analysis (ESCA). For both glasses, the early alteration product is a hydrotalcite-like compound [Mg6Al2CO3(OH)16·4H2O] in which HPO42−, SO42− and Cl− substitutes for CO32−. The measured basal spacing is 7.68 Å for the hydrotalcite formed from R7T7 glass and 7.62 Å for the hydrotalcite formed from basaltic glass which reflect the high Al/Al + Mg ratios x (0.34 ≤ x ≤ 0.46). The chemical microanalyses show that the hydrotalcite is subsequently covered by a silica-rich gel which evolves into saponite after a few months. These results support the use of basaltic glasses alteration patterns in Mg-rich solution, to understand the long-term behavior of R7T7 nuclear waste glass.
Surface Diffusion: Is It an Important Transport Mechanism in Compacted Clays?
Authors: Oscarson Dennis W. 
Published: August 2006

AbstractSurface diffusion, or migration within the electrical double layer next to mineral surfaces, is often invoked as a significant contributor to the overall diffusion coefficient in compacted clays, particularly where model predictions underestimate measured diffusion coefficients. The potential for surface diffusion of Sr2+, Ca2+and Na+on three clays compacted to dry bulk densities of 1.25 and 1.60 Mg/m3was examined. The clays were a bentonite, an illite/smectite, and a glacial lake clay (composed mainly of smectite, illite, kaolinite and quartz). The clays were saturated with a Na-Ca-Cl-dominated synthetic groundwater solution with an effective ionic strength of 220 mol/m3. Total intrinsic diffusion coefficients for the cations were determined from their steady-state flux through compacted clays, and apparent diffusion coefficients were obtained from the time-lag technique. Models of diffusive transport in compacted clays, based only on diffusion in the pore solution, adequately described the diffusion data for all clays and diffusants, and there was no need to invoke other transport mechanisms, like surface diffusion. The data indicate that surface diffusion is not a significant transport mechanism in compacted clays at least to a clay density of 1.60 Mg/m3.
Preparation and Characterization of Two Distinct Ethylene Glycol Derivatives of Kaolinite
Authors: Tunney James J. , Detellier Christian 
Published: August 2006

AbstractA new, well-ordered, thermally robust ethylene glycol intercalate of kaolinite was formed by refluxing the dimethyl sulfoxide intercalate of kaolinite (Kao-DMSO) with dry ethylene glycol (EG). This new phase (Kao-EG 9.4 Å) which is characterized by a d001 of 9.4 Å is distinct from a previously reported ethylene glycol intercalated phase of kaolinite (Kao-EG 10.8 Å) which has a d001 of 10.8 Å. The characterization of these two phases was studied by XRD, NMR, FTIR, and TGA/DSC. It was found that the concentration of water in the ethylene glycol reaction media played a crucial role in governing which of the phases predominated. Water favored Kao-EG 10.8 Å formation, while anhydrous conditions favored the formation of Kao-EG 9.4 Å. It is hypothesized that Kao-EG 9.4 Å is a grafted phase resulting from the product of the condensation reaction between an aluminol group on the interlamenar surface of kaolinite and the alcohol group of ethylene glycol. Ethylene glycol units would be attached to the interlamellar surface of kaolinite via Al-O-C bonds. The Kao-EG 9.4 Å phase was found to be resistant to both thermal decomposition up to 330°C and also, once formed, in the absence of interlamellar water molecules, to decomposition by hydrolysis in refluxing water.
2H NMR Study of Hydrogen Bonding in Deuterated Kaolinite
Authors: Hayashi Shigenobu , Akiba Etsuo , Miyawaki Ritsuro , Tomura Shinji 
Published: August 2006

Abstract2H NMR spectra of synthetic deuterated kaolinite have been collected in the temperature range from 150 K to 350 K. Hydroxyl groups show a Pake doublet pattern with an asymmetry factor of 0. They are almost fixed spatially, and undergo a wobbling motion with increasing temperature. The quadrupole coupling constant is 273 ± 3 kHz at 150 K, which indicates that interlayer hydrogen bonding is relatively weak.
Alteration of Ilmenite in the Manavalakurichi Deposit, India
Authors: Babu D. S. Suresh , Thomas K. A. , Mohan Das P. N. , Damodaran A. D. 
Published: August 2006

AbstractMagnetic fractionation, chemical, and structural analyses prove that alteration of ilmenite from Manavalakurichi deposit extends only up to the formation of pseudorutile with traces of rutile. The data indicate that ferrous to ferric iron transformation, ferric iron oxide formation, and iron removal contribute to the alteration sequence. The first two highly magnetic fractions are not unaltered ilmenite. A reduction in ilmenite unit cell volume indicates the ferrous-ferric conversion occurred during alteration.
Oxygen Isotopic Constraints on the Origin of Nodular Silica-Apatite from the Har Peres Pyroclastics, Golan Heights, Israel
Authors: Mizota C. , Yoshida N. 
Published: August 2006

AbstractOxygen isotope composition of three types of unique nodules which consist of amorphous silica-apatite, cristobalite-apatite and tridymite-apatite associations interspersed amidst basaltic pyroclastics from the Har Peres volcano, Golan Heights, Israel is reported. Unusual isotopic temperature (75°C estimated from oxygen isotope fractionation between cristobalite (δ18O = +25.5‰)-apatite (δ18O = +12.9‰) pair suggests that the nodule was not formed by present-day pedogenesis as has been previously proposed, but was a xenolith incorporated probably from the underlying siliceous phosphorites at a higher temperature. An observed negative oxygen isotopic fractionation (δ18O = −5.1‰) between tridymite (δ18O = +9.9‰) and associated apatite (δ18O = +15.0‰) is indicative of the nodular formation under disequilibrium conditions. A plausible mechanism of formation of the apatite (and calcite) associated with tridymite is an epitaxial overgrowth on template tridymite of magmatic origin under the current weathering regime. Oxygen isotopic evidence indicates a complicated origin for the nodules.
Palagonite Reconsidered: Paracrystalline Illite-Smectites From Regoliths on Basic Pyroclastics
Authors: Berkgaut Vadim , Singer Arieh , Stahr Karl 
Published: August 2006

AbstractPoorly crystalline authigenic alteration products of basic pyroclastics from the Golan Heights, Israel, were investigated by XRD, DTA, TGA, FTIR and chemical analysis. Modeling XRD patterns with the use of NEWMOD code provided a way to identify these clays as random interstratified illite/smectites (I/S) with ∼70% of illitic interlayers. Their characteristic features were very poor basal reflections, distinct hk bands, high CEC and low (∼2%) K2O content. Crystallite thickness distribution was found to follow Ergun's model with a weight-average thickness of 2.7–2.8 layers. A new method was proposed to calculate the proportion of kaolinite and 2:1 minerals in their mixtures and the average crystallochemical formula of 2:1 minerals in the presence of kaolinite. The method starts from data of chemical analysis and TGA and assumes that the anionic frameworks of kaolinite and 2:1 minerals are exactly O10(OH)8 and O10(OH)2 respectively. The number of OH-groups per ten oxygens not bonded to H in the empirical formula of the mixture is used to evaluate the proportion of kaolinite. Formation of I/S in well-drained environments under humid mediterranean climatic conditions was attributed to long dry seasons. Interstitial water composition was shown to be consistent with authigenic formation of I/S.