bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiogenic and stable isotope evidence for age and origin of authigenic illites in the Rotliegend, southern North Sea
Authors: Ziegler K. , Sellwood B. W. , Fallick A. E. 
Published: December 2006

AbstractAeolian sandstones of the Lower Permian Leman Formation (Rotliegend Group) provide the best gas reservoir in the southern North Sea, but permeability is greatly reduced by the presence of authigenic fibrous illites. New radiogenic (K/Ar) and stable (oxygen and hydrogen) isotope data are presented for fibrous illite cements (<0.1 µm), so that the absolute timing and controlling diagenetic factors for their formation can be more fully evaluated. Thus, the expected quality of gas reservoirs in the southern North Sea might be better predicted. Samples have been analysed from five wells in areas with contrasting structural evolution: the Sole Pit Basin, and the Indefatigable Shelf. The K/Ar ages of between 160 and 190 Ma have been obtained from the Indefatigable Shelf illites, and between 120 and 160 Ma for those from the Sole Pit Basin, reflecting different times of basin inversion. These K/Ar ages are interpreted by reference to burial/thermal models for each well. The temperature of illite precipitation falls between 88 and 140°C. Calculated pore-fluid compositions derived from oxygen and hydrogen isotopic analyses give values of ∼ + 1 to +9‰ (SMOW) δ18O and +1 to −50‰ (SMOW) δD. The illite δD values have probably been affected by isotopic exchange and fractionation with the surrounding gaseous hydrocarbon. The δ18O values reflect the degree to which evaporative concentration had affected Zechstein marine waters which subsequently invaded the Leman Sandstone. Comparisons between δ18O and δD values in clays and in formation water for the Leman Field suggest that oxygen isotope exchange might have taken place, and that the initial K+ and radiogenic 40Ar contents within illites may have been modified.
Variation in kaolinite morphology with growth temperature in isotopically mixed pore-fluids, Brent Group, UK North Sea
Authors: Osborne M. , Haszeldine R. S. , Fallick A. E. 
Published: December 2006

AbstractDiagenetic kaolinite in reservoir sandstones of the Brent Group precipitated following the dissolution of detrial feldspar. Two distinct morphologies of kaolinite occur: (1) early diagenetic vermiform kaolinite which is often associated with expanded detrital micas; (2) later diagenetic ‘blocky’ kaolinite. Combined hydrogen and oxygen isotopic studies suggest that vermiform kaolinite precipitated at 25–50°C, and blocky kaolinite at 50–80°C, from pore-waters of a similar isotopic composition (δ18O = −6.5 to −3.5‰). These pore-waters are interpreted to be either a mixture of meteoric and compactional waters, or alternatively a meteoric water that had evolved isotopically due to water-rock interaction. Kaolinite precipitation occurred predominantly during the late Cretaceous to early Eocene. Influx of meteoric water into the Brent Group, probably occurred during the Palaeocene. Fluid flow across the entire basin was driven by a hydrostatic head on the East Shetland Platform palaeo-landmass to the west. The development of the two kaolinite morphologies is possibly related to the degree of supersaturation at the time of precipitation. At low degrees of supersaturation, vermiform kaolinite precipitated slowly upon detrital mica surfaces. Blocky kaolinite precipitated more rapidly into open pore-space at higher degrees of supersaturation. Precipitation of blocky kaolinite was perhaps triggered by the decay of oxalate.
Petrographic and isotopic evidence for diagenetic processes in Middle Jurassic sandstones and mudrocks from the Brae Area, North Sea
Authors: Greenwood P. J. , Shaw H. F. , Fallick A. E. 
Published: December 2006

AbstractThe diagenetic history of an interbedded sequence of Middle Jurassic Sleipner (or Pentland), Hugin and Heather Formation sandstones and mudrocks from the Brae Area has been investigated using petrographic, stable isotope, fluid inclusion and K-Ar dating techniques. Generally, similar diagenetic processes affected both the mudrocks and sandstones resulting in the formation of carbonate, quartz and clay cements and evidence of dissolution and secondary porosity except for the absence of kaolinite in the Hugin Formation. The mudrocks were possible sources of some components involved in sandstone diagenesis but were not passive exporters of such reactants as similar reactions also occurred in the mudrocks. The stable isotope data indicate that most of the diagenetic processes occurred in the presence of marine or evolved marine pore-waters.
The case of the missing clay, aluminium loss and secondary porosity, South Brae Oilfield, North Sea
Authors: McLaughlin Ó. M. , Haszeldine R. S. , Fallick A. E. , Rogers G. 
Published: December 2006

AbstractUpper Jurassic sandstones of the South Brae Field were deposited as a submarine fan complex. The earliest formed concretionary ferroan calcite cement passively encloses detrital feldspars which originally formed more than 10% of the rock. Later non-ferroan calcite at the concretion margins was precipitated from a more aggressive fluid. This fluid dissolved up to half of the feldspars and micas originally present, but little or no clay was precipitated. Aluminium must have been lost from the system.A late dissolution event has enhanced porosity by up to 8%. Feldspar was again reduced in volume by about half, leaving only ∼2% in the rock today. Very minor amounts of fibrous illite and kaolinite (<1%) form the last diagenetic cement. Aluminium must have again been lost from the system.As the Kimmeridge Clay Formation (KCF) encloses and interdigitates with the South Brae sandstones, a local source of organic acids is quite possible. These acid solutions may have increased the mobility of Al. The Al from the feldspars must have therefore been transported vertically into the KCF, or more probably transported laterally by compactional flows out of the basin (up to 10 km) during release of overpressured basinal water.
Pore-lining chlorites in siliciclastic reservoir sandstones: electron microprobe, SEM and XRD data, and implications for their origin
Authors: Hillier S. 
Published: December 2006

AbstractPore-lining chlorites are often responsible for the preservation of porosity in deeply buried sandstones because they inhibit the formation of quartz overgrowths, but little is understood about when and how they form. Chemical analyses and XRD data indicate that there are at least two common types: Fe-rich, and Mg-rich. The Fe-rich examples occur as individual euhedral crystals, are invariably interstratified with 7 Å layers (probably berthierine) and form as the Ib β = 90° polytype at low temperatures. With increasing temperature, their chemistry changes, 7 Å layers are lost, crystal size increases, and eventually they transform to the high temperature IIb β = 97° polytype. The Mg-rich examples occur as boxwork arrangements of crystals, are not interstratified with 7 Å layers and are exclusively the IIb β = 97° polytype. The Fe-rich examples occur most frequently in sandstones that were deposited at the transition between marine and non-marine environments and the presence of Fe-rich oolites in many samples suggests a link to the ironstone facies. They probably formed originally at surface or near-surface conditions as a 7 Å mineral, such as berthierine or even odinite, in a fresh water/marine water mixing zone in tropical regions. The Mg-rich varieties tend to be found in aeolian or sabkha sandstones in close association with evaporites. They are probably replacements of Mg-rich smectites via the intermediate mineral corrensite. Precursor Mg-rich smectites formed originally from evaporite brines at near-surface conditions; chlorite itself was not formed until temperatures were high enough to crystallize the IIb β = 97° polytype.
Mineralogical and geochemical characterization of palygorskite from Gabasa (NE Spain). Evidence of a detrital precursor
Authors: Lopez-Galindo A. , Ben Aboud A. , Fenoll Hach-Ali P. , Casas Ruiz J. 
Published: December 2006

AbstractA mineralogical and geochemical study of the Gabasa outcrop (Huesca, NE Spain) was undertaken. It consists of Early Oligocene marly and clayey fluvial and lacustrine (playa-lake) sediments. The phases detected were quartz, amorphous silica, calcite, dolomite, palygorskite, illite, interstratified illite-smectite, Al-smectite and Mg-smectite. The palygorskite expands with ethyleneglycol. Statistical analysis of the geochemical data shows that the rare earth elements and transition trace elements are basically associated with the detrital phyllosilicates, although a considerable amount of the latter is contained in the palygorskite (ΣREE = 60–70 ppm, Cr+Co+Ni+V+Zn+Cu = 120–150 ppm), in contrast to the normally low values for neoformed minerals. This fact, together with the significant presence of Al and Fe in the palygorskite, suggest genesis involving alteration by dissolution of the 2:1 structure of the illite and/or Al-smectite, followed by re-ordering in a fibrous structure.
Processus d'adsorption du dinoseb sur l'hectorite-et la vermiculite-decylammonium
Authors: Vimond-Laboudigue A. , Baron M-H. , Merlin J-C. , Prost R. 
Published: December 2006

ResumeLes substrats argile-alkylammonium sont utilisés dans ce travail comme des modèles de sol, dans le but d'étudier les interactions entre un pesticide neutre peu soluble dans l'eau, le dinoseb, et des substrats dont les surfaces ont été rendues hydrophobes. Les spectrométries infrarouge (IR), Raman et de réflexion diffuse dans l'UV-visible sont utilisées de façon complémentaire aux isothermes d'adsorption pour préciser la localisation et l'état des molécules pesticide retenues sur les substrats. Dans le cas de la vermiculite-décylammonium, la fixation du dinoseb est observée à la fois sur les surfaces externes et dans les espaces interfoliaires, les molécules de pesticide sont directement en interaction avec les atomes d'oxygène de la surface des feuillets et avec les cations ammonium, par liaisons hydrogène. Le taux de molécules de dinoseb retenues sur l'hectorite-décylammonium est beaucoup plus faible. Les molécules fixées ont alors une structure voisine de celle des molécules libres. Ces analyses montrent que le caractère hydrophobe de la surface des complexes organominéraux est une condition nécessaire, mais non suffisante, pour la fixation de molécules peu solubles dans l'eau. Notre étude souligne l'importance des interactions spécifiques par liaison hydrogène entre le pesticide et le feuillet de vermiculite dans le processus de rétention.
Genesis and transformation of dickite in Permo-Triassic sediments (Betic Cordilleras, Spain)
Authors: Ruiz Cruz M. D. , Andreo B. 
Published: December 2006

AbstractIn the Maláiguide Complex (Betic Cordilleras, Spain), dickite is widely developed in clastic Permo-Triassic sequences. The lateral extent stretches at least 300 km along the Betic range, whilst vertical extent is variable and appears limited to the lowest 20–150 m of these sequences. Textural, chemical and crystallochemical characteristics of the dickite, illite/mica and chlorite in dickite-bearing rocks and in the overlying (Permo-Triassic) and underlying (Carboniferous) rocks have been investigated to determine the approximate conditions in which dickite has developed. Using the chlorite geothermometer (based on A1IV contents), temperatures of 146±28°C and 169±12°C have been deduced for two Permo-Triassic members, and 305±12°C for Carboniferous. The Si content in illites has been used as a geobarometer, and pressures of 4.8±2 kbar have been estimated in Carboniferous rocks and tentative pressures of 2.7±3 and 2.1±2 kbar in Permo-Triassic members. Chemical evolution of phyllosilicates is accompanied by increasing illite crystallinity and % 2M1 polytype.
Occurrence and genesis of palygorskite and associated clay minerals in a Pleistocene calcrete complex, Sde Boqer, Negev Desert, Israel
Authors: Verrecchia E. P. , Le Coustumer M-N. 
Published: December 2006

AbstractPalygorskite and associated clay minerals have been studied in a Pleistocene calcrete complex from the Negev desert (Sde Boqer, Israel). This complex is divided into five main parts: the chalky and marly bedrock overlain by its weathered product, a brecciated calcrete hardpan; the laminar crust; loess pockets trapped in the calcrete; and the overlying soft surficial soil. The distribution of clay minerals is directly dependent on the position of the sample in the calcrete complex. Smectite is inherited from the bedrock in the calcrete with an aeolian enrichment in loess pockets and upper soft soil. The source of kaolinite is mainly detrital, related to desert dust. Illite is partly inherited and partly neoformed in loess pockets and desert surficial soil. The origin of palygorskite is clearly related to precipitation processes from soil solutions, Si and Al ions being provided by the slope and detrital grains trapped in the calcrete, with Mg being provided by the parent rock, the slope and aeolian detrital dolomite. This neoformation occurs mainly around detrital grains such as quartz in the hardpan and along textural transitions in loess pockets and is associated with gypsum in the lower part of the toposequence where the evaporation fluxes are the most important. The existence as coatings around grains and the delicate structure of the fibres are incompatible with a detrital origin. Moreover, no evidence was found to support any transformation of smectite into palygorskite in the solid state. Palygorskite is the last step of the cycle of mobile silica and seems to be a product of late diagenesis in Sde Boqer calcrete.
Mineral quantification in sepiolite-palygorskite deposits using X-ray diffraction and chemical data
Authors: Lopez Galindo A. , Torres Ruiz J. , Gonzalez Lopez J. M. 
Published: December 2006

AbstractA quantification technique useful in analysis of clay-rich deposits containing sepiolite and/or palygorskite has been developed by combining diffractometric and chemical data and represents a considerable improvement on classic quantification based on X-ray diffraction. The required data are: intensity ratios between certain diffraction peaks of calcite-dolomite and sepiolite-palygorskite-smectites, and also the CaO, MgO, K2O, Al2O3 and SiO2 contents. The validity of this method was tested by analysis of artificial mixtures of pure phases of the minerals found in such deposits.
Ferriferous and vanadiferous kaolinites from the hydrothermal alteration halo of the Cigar Lake uranium deposit (Canada)
Authors: Mosser C. , Boudeulle M. , Weber F. , Pacquet A. 
Published: December 2006

AbstractThe uranium deposit (1350 Ma) of Cigar Lake (Canada) is surrounded by a late hydrothermal alteration halo (330 Ma) containing Fe-illites and kaolinites. Crystallochemical characterization of the kaolinites has been carried on the microscale using XRD, electron microscopy (SEM and TEM) coupled with EDX spectrometry and EPR. The large, well-crystallized particles show large amounts of Fe (0.9–1.8%) and V (0.3–0.5%). According to EPR measurements performed on both random powders and oriented samples, V occurs as the vanadyl ion VO2+, in substitution within the octahedral sheet of the kaolinite structure in the same way as Fe3+. Kaolinite growth proceeded through the hydrothermal alteration of anterior phyllosilicates devoid of V, induced by fluids which leached V-rich titano-magnetites in the surrounding sandstones.
Mica weathering in acidic soils by analytical electron microscopy
Authors: Aoudjit H. , Elsass F. , Righi D. , Robert M. 
Published: December 2006

AbstractThe mineralogy, crystallochemistry and microfabric of clay minerals from acidic soils were studied using transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Soil profiles, developed on saprolites, sampled in the main crystalline massifs of France represent different pedological environments. The study focused on the microsystem of mica weathering, which appeared to be the main source of secondary clay minerals, and involves microdivision, transformation and dissolution. Microdivision begins with the splitting of large particles along layer planes and their shearing normal to the layers. This induces the breakdown of particles of one hundred layers into particles having only a few layers. The transformation of micas follows two steps: they first transform into 1–1.4 nm mixed-layer minerals and then into hydroxy-Al interlayered vermiculite. The formation of hydroxy-Al interlayered vermiculite derived from micas is dominant in acidic soils; particles are generally small, consisting of only three to seven layers, and always have a dioctahedral composition, whatever the type of the original mica (trioctahedral or dioctahedral). Dissolution affects the surface layers or large domains of the core of the particles and leads to the formation of multi-elementary gels rich in Fe and Al.
Effect of non-swelling layers on the dissolution of reduced-charge montmorillonite in hydrochloric acid
Authors: Komadel P. , Bujdák J. , Madejová J. , Šucha V. , Elsass F. 
Published: December 2006

AbstractA series of reduced-charge montmorillonites (RCM), prepared from the same parent Li-montmorillonite (Jelšový Potok, Slovakia) by heating at various temperatures (105–210°C) for 24 h, was treated with 6 m HCl at 95°C for periods up to 30 h. Reaction solutions obtained were analysed for Al, Fe, Mg and Li and the solid reaction products were investigated by FTIR spectroscopy. Both analyses provided evidence that the extent of dissolution decreased with increased amounts of Li fixed within the montmorillonite structure, i.e. with increased heating temperature. Differences in the acid dissolution process were reflected in the structural changes which occurred within the RCM samples, due presumably to different positions of fixed Li. The ethylene glycol monoethyl ether (EGME) surface areas, and XRD and HRTEM analyses of the RCM series revealed an increased amount of non-swelling layers in the samples prepared at higher temperatures, which caused a substantially slower decomposition of M7 and M8 in HCl. The calculated XRD patterns of M6 and M7 confirmed the presence of 20% and 45% pyrophyllite-like layers, respectively, in these samples. Mixed-layer pyrophyllite-like-smectite and pyrophyllite-like crystals, containing only non-swelling layers, were found in sample M8. The results confirmed that the amount of swelling layers in RCM significantly affects their dissolution rate in HCl.
Parallel reaction kinetics of smectite to illite conversion
Authors: Wei H. , Roaldset E. , Bjorøy M. 
Published: December 2006

AbstractA parallel reaction model is developed for describing the conversion of smectite to illite. Each reaction represents a group of similar smectite layers that require the same activation energy and have the same illitization rate. The model considers that the rate-determining reactant is smectite itself which follows first-order Arrhenius kinetics. By modelling the data from hydrothermal illitization experiments and from a Gulf Coast well, the activation energies are found to be distributed in the range of 11–24 kcal/mol with a maximum reaction at 18 kcal/mol, which involves 65% of reactive smectite. A frequency factor in the order of 10−3–10−4/s, obtained from the data fitting, appears to be adequate for modelling natural diagenesis in sedimentary basins. The distribution pattern of activation energies is considered to be controlled by the degree of heterogeneity of the initial smectite and the degree of electrostatic interactions between smectite layers and the newly formed illite layers during reaction.
Mineralogical and chemical heterogeneity of three standard clay mineral samples
Authors: Köster H. M. 
Published: December 2006

AbstractMineralogical and chemical heterogeneity within three standard clay mineral samples have been identified by X-ray diffraction and chemical analysis of various size-fractions. This heterogeneity is partly attributed to accessory minerals, but mostly to structural and compositional variations in the 2:1 layer minerals of different particle size in the same specimen.
Properties and applications of palygorskite-sepiolite clays
Authors: Galan E. 
Published: December 2006

AbstractThe palygorskite-sepiolite group of clay minerals has a wide range of industrial applications derived mainly from its sorptive, rheological and catalytic properties which are based on the fabric, surface area, porosity, crystal morphology, structure and composition of these minerals. For assessing potential industrial uses, the mineralogical and chemical composition of the clay and its basic physical and physico-chemical parameters must be determined. Then some particular properties of commercial interest can be modified and improved by appropriate thermal, mechanical and acid treatments, surface active agents, organo-mineral derivatives formation, etc. In this paper, a revision of the principal characteristics of commercial palygorskite-sepiolite clays is presented, and potential uses are suggested according to these data. New products and applications are being investigated and those concerning environmental protection in particular, are noted. Finally, possible health effects of these elongate clay minerals are discussed.
Preparation and characterization of Ti-pillared acid-activated clay catalysts
Authors: Bovey J. , Kooli F. , Jones W. 
Published: December 2006

AbstractThe preparation and characterization of Ti-pillared acid-activated clays (designated Ti PAACs) and conventional Ti-pillared clays (designated Ti PILCs) are described. Preliminary catalytic results show that these materials possess remarkably enhanced abilities to catalyse the dehydration of pentanol compared with their Al counterparts (in excess of 200% in the case of the PILCs and up to 82% for the PAACs). These activities approach those previously reported for non-pillared acid-activated clays.
Electric birefringence for monitoring size changes in clay suspensions
Authors: Hinds I. C. , Ridler P. J. , Jennings B. R. 
Published: December 2006

AbstractThe growth and decay rates of rapid, induced electro-optical phenomena in dilute colloidal suspensions are characteristic of the geometry of the solute particles. The speed of measurement renders such methods especially relevant for fast, in situ analyses of the size and size distribution of colloids in practical, industrial situations where these properties may be undergoing continuous change. The principles of the measurement of electrically induced birefringence using pulsed fields is outlined and used to study vermiculite suspensions as they undergo size reduction in an ultrasonic field. The high sensitivity of the method to both the particle size range and the form of the distribution function is indicated. The use of the method for on-line monitoring of dilute mineral suspensions for the indication and control of aggregated, dissolving or growing media is discussed.
Interpretation of orientation polarization in homoionic dry montmorillonite
Authors: Belarbi H. , Haouzi A. , Giuntini J. C. , Zanchetta J. V. , Niezette J. , Vanderschueren J. 
Published: December 2006

AbstractFrom measurements of dielectric losses as a function of frequency and temperature, as well as thermally stimulated depolarization currents, performed on a dry Na-montmorillonite, a qualitative description of the conduction mechanism has been proposed for this type of material. A representative approach related to the polarization phenomenon determined on this material led to the evaluation of the elementary energy Wj, connected with the reorientation of the dipoles during the hopping process. The results show the coherence between the polarization conductivity and the thermally stimulated currents methods.