Rare earth elements are mobilized, fractionated and precipitated during weathering processes of basaltic rocks of the Lisbon Volcanic Complex. In general there is an increase in the REE contents in the whole samples with increasing weathering and fractionation between LREE and HREE. Cerium is partially oxidized and Ce4+ is retained resulting in negative Ce anomalies in the whole samples of the base and middle profile zones. In the clay fraction there is an increase in the REE contents from the top to the bottom of the profiles, except for Ce, giving rise to positive Ce anomalies in the top and negative anomalies of this element in the middle and bottom of the profiles. Significant positive Ce anomalies occur in the finer fractions of palaeoweathered (Upper Cretaceous/ Lower Eocene) basalts associated with low REE contents relative to the whole samples indicating more intense leaching conditions in the Upper Cretaceous/Lower Eocene than at the present day. However, in both cases no positive Ce anomalies were found in the whole samples. There appears to be a negative correlation between the (La/Yb)ch ratio variation and the clay mineralogy/drainage conditions.

L'altération latéritique débutante des orthopyroxènes et clinopyroxènes de Niquelandia, Brésil, montre plusieurs stades. Le premier stade facultatif est la formation de produits ‘amorphes’ dont la composition chimique proche de celle des minéraux parentaux, montre déjà un enrichissement en nickel. Le deuxième stade est marqué par l'apparition de phyllosilicates dont la nature et la composition chimique varient selon le degré de porosité de la roche parentale. Cette porosité contrôle également la distribution du nickel dans les différents phyllosilicates, (saponite, talc, pimélite). Les pyroxènes ne contenant pas ou très peu de nickel, il est clair que le nickel qui s'accumule dans les produits de l'altération est totalement importé avec les eaux de percolation. L'origine de ce nickel est à rechercher plus haut dans les profils ou plus en amont dans la séquence, là où les dunites sont présentes.

The clay mineralogy of Upper Permian–Lower Cretaceous mudstones from East Greenland has been investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and thermal analysis in order to evaluate long-term trends in provenance and palaeoclimate and to detect possible volcanic events. The Upper Permian–Lower Triassic mudstones contain illite, chlorite, vermiculite, kaolinite and illite-smectite (I-S), whereas the Rhaetian–Sinemurian mudstones are dominated by kaolinite. Aalenian–Albian mudstones contain kaolinite and large amounts of I-S with ˜80% illite layers. Exceptions are three Kimmeridgian samples, which contain mainly I-S with 30% illite layers, and three Upper Barremian–Lower Aptian samples with large amounts of smectite layers. Discrete clay minerals in the Upper Permian–Jurassic mudstones are largely detrital. The smectite-rich I-S probably reflects episodes of volcanic activity in late Jurassic and late Barremian–early Aptian times. This is the first indication of Mesozoic volcanism from the Mesozoic rift basin of East Greenland. The main sediment source during late Permian–early Cretaceous times was weathered Precambrian and Caledonian crystalline basement. The only possibly climate-induced change is a change from chlorite, illite, vermiculite and kaolinite in Upper Permian–Lower Triassic mudstones to kaolinite and I-S in the Jurassic mudstones and is probably due to an increase in precipitation.

Desautelsite, a Mg(II)Mn(III) hydroxy carbonate first described in 1979 and represented by the general formula Mg(8−x)Mn(III)x(OH)16(CO3)x/2 (in which 2 < x < 2·67), has been synthesized under controlled pH conditions (induced hydrolysis) and coprecipitation techniques. In the pH-stat syntheses, the desautelsite is formed by aerial oxidation of MnCO3 in 0·05–0·15 m Mg(NO3)2 solutions at ∼pH 9 and temperatures of 35°C where, in the absence of Mg, manganite would normally form. The synthesis product from this technique is generally more crystalline than that formed by the coprecipitation method. Composition, particle shape and aggregation may be controlled through variations of the Mg concentration, pH, aeration rate or temperature. Indirect evidence suggests Mn to be present in the +3 oxidation state in the desautelsite.

Mineralogical and geochemical studies of Cretaceous segments of Argille Varicolori and Flysch Rosso successions from the southern Apennines allow their provenance and history to be evaluated.

The occurrence of detrital kaolinite and fine-grained Fe-oxyhydroxides, the strong depletion of Na2O, K2O and CaO, and the enrichment in the transition elements document severe alteration in the source areas. Nevertheless, mineralogical and geochemical features able to discriminate the shale families are still preserved. The presence/absence of rock fragments derived from a ‘crystalline’ source, the significant chemical differences as well as the characteristics of clay minerals, discriminate the studied shales. The absence of indications suggestive of mixing of the detrital components favour the hypothesis that the two shales were deposited in distinct basins which probably received contributions from continent-ocean convergent areas (Argille Varicolori) and from more stable areas (Flysch Rosso).

The adsorption of acrylonitrile (AN) monomer vapour in the interlamellar space of smectites exchanged with different cations (Na or Y or hexylammonium) was monitored and used to yield macromolecular layers. Polymerization in the presence or absence of a free-radical initiator was obtained by heating at 100°C for 72 h. Cyclization can already be obtained at this stage, and is completed by heating the polyacrylonitrile (PAN)-complexes at 220°C for 48 h.

Continuous nodular limestone beds in north-west European shale sequences developed during early diagenesis via anaerobic, bacterial catabolysis of organic matter which yielded both carbonate and sulphide. The high carbonate content of the nodular limestones (50–90%) demonstrates that they developed in the upper tens of metres of the sediment column. In addition, each of the nodular limestones displays a centrifugal decrease in carbonate, indicating that growth was synchronous with compaction of the host ooze. The chemistry of the carbonate changed with time, becoming more rich in magnesium and iron and reflecting a progressive change in the porewater chemistry from its initially marine composition. The earliest precipitate was calcite containing < 1 mole% MgO; later precipitates contained several percent MgO and ultimately dolomite was precipitated. Similarly, iron content of the carbonate increased as precipitation continued and sulphate reduction, and thus pyrite production, declined. The early diagenetic cementation of many marine sandstones followed a pattern similar to that of nodular limestones and much of the carbonate was also derived from organic matter via bacterial oxidation. Thus, early diagenetic bacterial oxidation of organic matter may not only reduce the source potential of shales but also reduce the reservoir potential of associated sandstones, or those more distant which lie along compactional-fluid pathways.

An experimental investigation was conducted on the alkali activation of a kaolinitic clay using an alkaline mixture composed of hydrated lime (Ca(OH)2) and sodium carbonate (Na2CO3) solution. The Ca(OH)2/Na2CO3 alkaline mixture was developed to overcome the high cost and chemical aggression associated with classical alkaline solutions. The mineralogical composition and microstructure of the alkaline mixture and alkali-activation products were studied using X-ray diffraction, attenuated total reflectance-Fourier transform infrared spectroscopy, thermogravimetric analysis and energy-dispersive X-ray-scanning electron microscopy techniques. Pirssonite (Na2Ca(CO3)2·2H2O), calcite (CaCO3), and sodium hydroxide (NaOH) formed as a result of mixing of Ca(OH)2 with Na2CO3. The alkali activation of natural clay with the Ca(OH)2/Na2CO3 alkaline mixture produced a binding agent identified as hydroxysodalite phase (Na8Al6Si6O24(OH)2·4H2O) when pure kaolinite was used, and cancrinite carbonate (Na6Ca1.5[Al6Si6O24](CO3)1.5·1.8H2O) when kaolinitic clay with high a calcite content was used. The mechanical strength of the binder developed was evaluated on cylindrical specimens containing granite waste as a filler material under dry and soaked conditions. The classical NaOH activator was used for comparison. For specimens produced using a Ca(OH)2/Na2CO3 mixture as the alkaline activator, the recorded strength valuewas 21 MPa which was 35% less than that achieved by the classical NaOH solution. Durability tests on samples soaked in water for 24 h showed a reduction in strength from 34 to 22 MPa for specimens prepared with NaOH solution, and from 21 to 11 MPa for the specimens prepared with a Ca(OH)2/Na2CO3 alkaline mixture.

Dans les encroûtements calcaires sous galet de la Plaine Poitevine, nous avons mis en évidence, par des méthodes microscopiques, une séquence minéralogique évolutive de la calcite. Par spectrométrie d'absorption infrarouge des éléments de la séquence prélevés en hiver, nous caractérisons, à côté de la calcite (bande à 1420 cm−1), du carbonate amorphe hydraté (bandes à 1405 et 1485 cm−1 et un autre type de calcite (bande à 1445 cm−1). Les résultats d'essais de laboratoire nous permettent d'envisager une évolution du carbonate amorphe vers la calcite par l'intermédiaire d'une phase calcitique transitoire, et d'aragonite toujours en faible proportion. La formation de ces carbonates est liée aux conditions bio-physico-chimiques du sol.

The morphology of volcanic glass particles in rhyolitic and andesitic tephra of central North Island and Taranaki areas of New Zealand has been studied by scanning electron microscopy. Electron probe analyses of the glasses are compared with those of the clays to which they weather. Loss of silica characterizes the weathering of both glasses. The rapid rate of weathering of andesitic glass is attributed to its occurrence as fine, soft microlites and extensive substitution of Al for Si in the structure. Rhyolitic glass weathers more slowly because it occurs as hard and brittle particles containing relatively little alumina. It is suggested that the structure, chemical composition and chemical activity of allophane is governed largely by the chemical composition and bonding characteristics of the parent glass.

Intercalation of an ammonium amphiphile having an azobenzene chromophore, 4-dodecyloxy-4 ‘-(trimethylammoniopentyloxy)azobenzene and 4-(ω-trimethylammoniodecyloxy) -p’- (octyloxy)azobenzene bromide, into the layered silicate magadiite (ideal formula Na2Si14O29·nH2O) was carried out by a conventional ion exchange reaction in an aqueous medium. An intercalation compound with the ideal formula {(C12AzoC5N+)1.4H0.6·Si14O29·nH2O} was obtained. Based on the change in the basal spacing (to 4.21 nm) after the reaction and the visible absorption spectrum of the product, the intercalated azo dyes appear to form a J-aggregate in the interlayer space of magadiite. Under UV and visible light irradiation, the intercalated azo chromophore exhibited reversible transcis isomerization in the interlayer space of magadiite. This is the first successful report of photochemical reactions of guest species in the interlayer space of magadiite.

Iron-rich dioctahedral 2:1 clays were sampled in metalliferous sediments from Atlantis II Deep (Red Sea), and studied by XRD, TEM, FTIR and Mössbauer spectroscopy. One sample with the structural formula (Si3·94Fe3+0·06)(Fe3+1·90Mg0·10)K0·1(Mg, Ca)0·03 is closer to the theoretical end-member ferripyrophyllite Si4Fe3+2O10(OH)2 than any other Fe-rich clay previously described. Other samples appear as mixed-layered clays: ferripyrophyllite-hydroferripyrophyllite or hydroferripyrophyllite-celadonite.

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been used to determine the nature of acid sites present in Na+-, Ni2+- and Al3+-exchanged montmorillonite using the diagnostic base, pyridine. The pyridine additions were performed in situ at 25°C in the presence of liquid benzene or deuterated 1,4-dioxan to ascertain whether the acidity profile was influenced by the presence of either the non-polar or oxygenated solvent. Pyridine treated Ni2+-montmorillonite exhibited absorption bands characteristic of Lewis bound base in both benzene and deuterated 1,4-dioxan indicating that the Lewis acid sites were present at low temperature and were accessible in both solvents. The presence of a strong 1537 cm−1 band in pyridine-saturated Al3+-montmorillonite confirmed that this clay acted as a Brønsted acid in benzene. However, this diagnostic band was significantly reduced in the presence of deuterated 1,4-dioxan.

Measurements of the kinetics of acid dissolution of synthetic aluminous goethites and corresponding hematites produced by heating of parent Al-goethites at various temperatures were carried out in 1 M HC1 at 30, 40 and 50°C. Dissolution-time curves show sigmoidal shapes for the goethites (110°C), whereas deceleratory shapes were obtained for most of the partly and fully dehydroxylated samples. The dissolution rate for all materials decreased with increasing Al substitution and increased with increasing dissolution temperature, specific surface area and heating temperature. On a unit surface area basis, hematite dissolved ∼ 2–8 times faster than goethite. Dissolution kinetics of most heated goethite samples (200–260°C) were quite well described (R2 > 0.96) by the modified first-order Kabai equation. The activation energy and frequency factor for dissolution increased with increasing Al substitution.

Aggregation of colloidal clay particles (Na-montmorillonite) by CaCl2 and anionic polysaccharide (succinoglycan) in turbulent conditions was investigated using time-resolved size measurements by laser diffraction on diluted (50 mg l –1) and stirred suspensions. Excess of Ca2+ ions promotes coagulation of the clay, reducing interparticle repulsions, and allows adsorption of succinoglycan, inducing bridging flocculation. Growth/breakage cycles, characteristic of the turbulent conditions, cause the macromolecules to be incorporated in the innermost of the flocs, where the morphological units are shown by confocal microscopy to be the micrometric Ca-clay particles. Such incorporation results in an increased floc tensile strength, depending on the amount of macromolecules adsorbed, with a maximum at polysaccharide concentrations of 2 wt.% with respect to clay mass.

Resonance Raman spectroscopy has been used to observe the formation of cation radicals in the adsorption of N,N,N',N'-tetramethylbenzidine (TMBD), benzidine, N,Ndimethylaniline (DMA) and aniline on Na-, Cu- and Fe-montmorillonites. Cation radicals of benzidine and TMBD, and their dications were formed at acid sites on the montmorillonite surface, or through the reduction of Cu or Fe interlayer ions, and were adsorbed in the interlayer. Their structures are represented by biphenoquinone type structure, where the inter-ring CC bond and the ring C-N bond have double bond characters. It was demonstrated from Raman spectra that DMA and aniline adsorbed on Cu-montmorillonite from the vapour phase dimerize to form TMBD and benzidine dications.

The Boom Clay is an important raw material for the Belgian structural clay products industry. It can be divided into several lithological sub-units. In order to obtain an insight in the parameters which characterize these different units, and which affect the overall properties of the clay, a detailed chemical, physical and mineralogical analysis was carried out. Pearson correlation coefficients were calculated between the variables, which were then placed in four correlation groups: a quartz/clay mineral group, a reducing component group, a carbonate group and a feldspar group. This treatment of the data allowed three analysis parameters to be selected: <2 µm fraction, organic carbon and CO2. The other variables could be calculated fairly accurately from these by means of regression lines.

Previous attempts to use illite as a geothermometer have failed: no general relation between the mineral's chemical composition and temperature of crystallization has been found. Here, chemical compositions of 27 illite samples from five different geothermal fields (the data on four of which were drawn from the literature) were compared with their crystallization temperatures. As previously reported by Cathelineau (1988), the K content was found to be the only variable yielding a suitable correlation, but only when applied to one geothermal field; when various geothermal systems were considered, the correlation weakened considerably. Introduction of a correction algorithm to the K content of the illite has made it possible to draw a single line to fit the data from all the studied samples, yielding a good correlation coefficient (r = 0.84).

Microstructural (fabric, forces and composition) changes due to hydrocarbon contamination in a clayey soil (glacial till) were studied using scanning electron microscopy (microfabric analysis), atomic force microscopy (force measurement) and a sedimentation bench test (particle size measurements). Non-polluted and polluted glacial till from NE Poland (in the area of a fuel terminal) were used for the study. Electrostatic repulsive forces in the polluted samples were much lower than in non-polluted samples. In comparison with non-polluted samples, the polluted samples exhibited lower electric charge, attractive forces on approach and strong adhesion on withdrawal. The results of the sedimentation tests indicate that clay particles form larger aggregates and settle out of the suspension rapidly in diesel oil. In non-polluted soil, the fabric is strongly aggregated – dense packing, dominating face-to-face and edge-to-edge types of contacts, clay film tightly adhering to the surface of larger grains and interparticle pores are more common. In polluted soil the clay matrix is less aggregated – loose packing, dominating edge-to-face types of contacts and inter-micro-aggregate pores are more frequent. Substantial differences were observed in the morphometric and geometrical parameters of the pore space. The polluted soil micro-fabric proved to be more isotropic and less oriented than in non-polluted soil. The polluted soil, in which electrostatic forces were suppressed by hydrocarbon interaction, displays more open porosity and larger voids than non-polluted soil, which is characterized by the occurrence of strong electrostatic interaction between the clay particles.