Swelling, shrinking and physical breakdown processes are reviewed with reference to well-known mudrock and overconsolidated clay formations in the UK and USA. Swelling results from two processes: the equilibration of depressed porewater pressures following stress relief, and the physico-chemical (osmotic) response of component clay minerals. Expansion in Na-smectite, and to a lesser extent Ca-smectite, clays is governed by double-layer swelling, whereas in kaolinites it is purely a mechanical unloading phenomenon; illites show an intermediate response. Intraparticle swelling in mudrocks older than the Silurian in the UK, or Upper Mississippian in the USA, can be expected to be reduced because of the removal of expandable layers by burial diagenesis. Shrinkage, like mudrock breakdown, is restricted to the partly saturated zone. Suction pressure-moisture content curves of indurated mudrocks are shown to be different from mudrocks and clays with high proportions of expandable clay minerals. Classification of expansion potential based on activity ratio poses problems with indurated types, but with some modification of method reasonable predictions can be made. Controls on physical disintegration are identified as: (i) incidence of sedimentary structures and discontinuities, (ii) slaking (air breakage), (iii) expandable clay mineral content, especially smectite, and (iv) clay mineral fabric orientation. Exceptionally high exchangeable sodium percentages have been measured in Coal Measures rocks susceptible to breakdown.

Nous décrivons un montage expérimental permettant d'obtenir, avec une bonne précision, des diagrammes de diffraction X de poudre d'argile dans un état hydraté homogène et de suivre la cinétique du processus d'hydratation. Nous avons pu déterminer, dans le cas de l'état homogène à une couche d'eau d'une beidellite sodique, la position des cations échangeables, le nombre total de molécules d'eau par maille et leurs coordonnées z, en utilisant une méthode de modèle basée sur la comparaison des profils expérimentaux et calculés des réflexions 00l. De plus nous avons comparé les caractéristiques structurales et en particulier le mode d'empilement des feuillets de l'état monocouche avec celui des états anhydre et bicouche. L'analyse du profil des réflexions 00l montre l'existence de fluctuations autour d'un espacement basal moyen . Ces fluctuations sont interprétées comme provenant de l'hétérogénéité de la distribution des charges dans le feuillet. Enfin, un processus théorique d'hydratation et de déshydratation est proposé.

The intercalation process of crown-ethers and cryptands into Ba2+- and Na+-montmorillonites leads to H-type adsorption isotherms according to the Giles et al. classification. The experimental monolayer capacity shows that 1:1 or 2:1 macrocyclic ligand/interlayer cation complexes can be produced. Kinetic experiments at different temperatures indicate that the intercalation is diffusion-controlled. The activation energies deduced from Arrhenius plots are 25–38 kJ mol−1.

Expanding and non-expanding layers of interstratified clay minerals have been examined by high-resolution transmission electron microscopy. Permanent expansion of swelling layers under the electron beam was achieved by intercalation of n-alkylammonium ions, especially the octadecylammonium ion. Oriented flakes of clay minerals were prepared by embedding the expanded or non-expanded clay minerals in epoxy resin, followed by centrifugation before hardening of the resin. The minerals were then cut perpendicular to 001 using an ultramicrotome. Crystals of macroscopic trioctahedral vermiculites show homogeneous interplanar distances of 24 Å after intercalation of octadecylammonium ions. Crystals of dioctahedral soil vermiculites often show a central zone with non-expanding 10 Å layers; the outer zone shows a disturbed layer sequence extensively expanded by n-alkylammonium ions. After embedding in epoxy resin, vermiculites show stable 9·2 Å interplanar spacings but smectites expand to 13 Å. Montmorillonites of the Wyoming type show curved stacks of layers. Most of the layer stacks of montmorillonites of the Cheto type are split and disordered aggregates of single layers are formed. Crystals of illites and glauconites are built up of aggregated small stacks of 10 Å layers, the layer stacks consisting of 10 layers. Mostly the boundaries of the layer stacks are parallel to their 001 planes; sometimes low-angle boundaries are found. The dimensions of the layer stacks, ∼ 100 Å thick and some hundreds of Å in plane, are equal to the dimensions of the domains of coherent scattering of X-rays. The border layers between the layer stacks are identical with those 5 to 10% of layers which swell with glycerol or ethylene glycol during X-ray analysis. Some of the layer stacks of illite and glauconite crystals are expanded by octadecylammonium ions within a fortnight. The other stacks show unchanged 10 Å spacings. The different expanding behaviour of different layer stacks reflects the heterogeneity of the layer-charge distribution in the mica clay minerals. K-bentonites show the same expanding behaviour as illites and glauconites but the number of layers expanding with octadecylammonium ions is greater in K-bentonites than in illite crystals. Expanded mixed-layered minerals of the illite-smectite type show a different layer stacking sequence from illites. Random irregular stacking of mica layers with expanded layers are recognized rather than coherent stacks of mica layers. The crystals have a stepped morphology, perhaps effected by translations along the 001 plane. After reaction of the rectorite from Garland County with octadecylammonium ions, the non-expanded mica layers and the expanded smectite-like layers can be distinguished. The heterogeneity of the interlayer charges of the smectite layers is documented by the formation of alkyl double-layers with 17 Å spacings and alkyl triple-layers with 21 Å spaces in irregular sequence. The ‘rectorite’ from the Goto Mine expands nearly homogeneously in comparison with the rectorite from Garland County. After reaction with octadecylammonium ions, interplanar spacings of mostly 31 Å are observed but rarely spacings of 27 Å. The smectite layers of the corrensite from Kaubenheim are expanded by tetradecyl-ammonium ions to 18 Å spacings by formation of alkyl double-layers. A regular 1 : 1 layer structure of 14 Å chlorite layers and expanded 18 Å smectite layers with total spacing of 32 Å can be observed. Muscovite and pyrophyllite are not expandable by n-alkyl-ammonium ions within a fortnight. However, sporadic layers of celadonite crystals are expanded. Generally the 10 Å or 9·2 Å layers extend over the whole crystals of the three minerals. In celadonite crystals, disorder is caused sporadically by interrupted layers or slightly enlarged layer spacings.

Clay minerals are almost ubiquitous in soil and rock and are among the most reactive silicates. They affect the engineering behaviour of soil and rock both as materials of construction and as foundation materials. In the petroleum industry, clay affects the permeability of reservoir formations, it is a common cap-rock, and it is also a constituent of the fluids used in drilling operations. Engineering behaviour almost always involves clay-water interaction and in turn this depends on the nature of water and solutions and on the composition and microstructure of the clay. The importance of clay to specific problems from each of these areas is discussed. In foundation engineering its role in soil-moisture interaction is illustrated by reference to problems resulting from the geological history of some North American soils and from engineering activities. In building materials, reference is made to its effect on concrete durability in aggregate-related problems. The importance of clay in petroleum engineering refers to authigenic clays in reservoir rocks, to clay behaviour in the Alberta oil sands and to the use of clay minerals as a geothermal thermometer.

K-depleted phlogopite mica was used as a topotactic precursor and treated with alkali (Li+, K+, , Rb+, Cs+), alkaline-earth (Mg2+, Ca2+, Sr2+, Ba2+) and trivalent (Al3+) cations under hydrothermal conditions of 200°C and 30 MPa pressure. K-, NH4-, Rb- and Cs-aluminosilicate micas were synthesised at 200°C in one day. The synthesis of Cs-aluminosilicate mica, with potential applications in the management of nuclear wastes, has been achieved for the first time by this approach. Ion exchange by Li+, Na+ and alkaline-earth cations under hydrothermal conditions did not produce anhydrous mica phases but resulted in hydrous phases with one or two layers of water molecules between the clay layers. The formation of hydrous phases may be attributed to the high hydration energy of the above cations compared to K+, , RB+ and Cs+. Ion exchange with Al3+ produced a chlorite-like phase because of the hydrolysis of Al3+ under these hydrothermal conditions. These studies are of relevance in the immobilization of wastes where hazardous ions can be fixed in highly stable insoluble phases like mica or chlorite.

Syntheses of ferric smectites were performed at low temperature (75° C by aging coprecipitated gels of silica and Fe2+-sulphate under initially reducing then oxidizing conditions. Under strictly reducing conditions only nuclei of a trioctahedral ferrous stevensite were observed and crystal growth did not take place. When a spontaneous oxidization, in contact with air, was effected, the ferrous smectite nuclei transformed rapidly into a ferric, nontronite-like, smectite. Crystallogenesis of the ferric smectite was studied by XRD, IR, DTA, Mössbauer and EPR spectroscopies. The end-synthesis smectite contained only Fe3+ ions, all located in the octahedral sheet. This clay was mixed with a cryptocrystalline iron oxide phase containing one-third of the iron atoms and undetectable by XRD.

L'évolution structurale et texturale ainsi que le comportement hydrique de deux montmorillonites-Ca (Wyoming et grecque) ont été éudiés par microscopic électronique à transmission (MET) et plus précisément par analyse de la diffusion aux petits angles des rayons X (DPAX). L'étude au MET a permis de montrer qu'à faible contrainte, le matériau est formé par un réseau de particules déformables délimitant des pores de grandes dimensions (~2 μm). L'étude en DPAX des mêmes systèmes soumis à une contrainte de type succion a montré que: 1. Lors de la première dessiceation il y a d'abord déformation du réseau sans regroupement des particules (p ⩽ 1 bar), puis regroupement des particules face-face pour former des particules de plus grande épalsseur (p > 1 bar). On montre aussi que l'eau est essentiellement extraite de la porosité interparticulaire. 2. Lors de la réhydratation, on met en évidence qu'après dessiccation le système perd une grande partie de son aptitude à, reprendre de l'eau et que cette perte est d'autant plus importante que le niveau de dessiccation préalable a été élevé. Ceci est dû au falt qu'une partie de la porosité est réduite fi des espaces ayant la propriété de l'espace interfoliaire.

L'étude concerne 225 échantillons d'âge Jurassique à actuel de l'Océan Atlantique. La comparaison de l'abondance des smectites lattées, estimée sur micrographies électroniques, et de divers paramètres des sédiments, apporte des informations nouvelles sur la genèse et la signification de ces minéraux dans des sédiments non volcanoclastiques et non remainés. L'élaboration des smectites lattées par recristallisation diagénétique de smectites détritiques est favorisée lorsque la microperméabilité du sédiment est réduite (argiles fibreuses et particules calcaires, surtout les foraminifères, peu abondantes); lorsque les échanges chimiques à bilan constant avec le milieu interstitiel sont facilités (smectites abondantes) et lorsque la vitesse de dépôt est faible à moyenne. Dans les autres cas, la recristallisation de smectites lattées est très réduite ou absente. L'identification de ces minéraux dans les sédiments permet de préciser les conditions paléogéographiques de dépôt. La rareté des smectites lattées au Plio—Quaternaire pourrait être liée à l'extension des grands refroidissements mondiaux du climat.

Deeply buried (> 3·5 km) Rotliegend aeolian sandstones in the Southern North Sea Basin display a number of interesting diagenetic features including (i) zoned iron-rich carbonate cements, (ii) anhydrite, halite and baryte cements, (iii) at least two generations of authigenic illite, and (iv) significant secondary porosity created by cement and framework-grain dissolution. The creation and destruction of secondary porosity is the result of changes in porewater chemistry during burial and subsequent uplift. Three pore-fluid regimes can be identified: (1) alkaline, oxidizing conditions during shallow to intermediate burial; (2) acid, reducing conditions during intermediate to deep burial; (3) alkaline, reducing conditions during deep burial and uplift. The transition from stage 1 to stage 2 was probably caused by expulsion of waters from the underlying Carboniferous shales. The transition to stage 3 probably began when faulting associated with uplift allowed invasion by alkaline fluids derived from Zechstein sediments.

The structure of synthetic aluminosilicates prepared at pH 6 has been investigated by 29Si and 27Al high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. Fourier transform infrared (FTIR) spectroscopy and electron microscopy have also been used to characterize the products. The amount of Si and Al in protoimogolite, disordered allophane and other structures has been measured. There is a fair correlation between the intensity of the 349 cm−1 band in the FTIR spectra and the proportion by weight of protoimogolite Si measured by NMR. It is shown that disordered allophanes have similar structures to those proposed by van Reeuwijk and de Villiers (Soil Sci. Soc. Am. Proc. 32 (1968) 238–240), i.e. octahedral Al surrounding a tetrahedral core. Moreover, it is clear that at high Al:Si ratios (⩾1:1), protoimogolite can compete with disordered allophane precursors for aluminum. The driving forces for formation of protoimogolite rather than allophane appear to be long range Al-Al repulsive forces through oxygen.

Mineralogical analysis of Devonian Red Marl using XRD, TEM, SEM and EDAX showed that it consisted of illite, quartz, and feldspar with minor amounts of chlorite and hematite. Physico-chemical changes in the soil minerals on reaction with lime (calcium hydroxide) from one day up to two years were investigated by these techniques to gain information on the soil-lime reaction mechanism. Significant reaction of the soil minerals and lime was found to occur only at elevated temperatures (50–75°C) in a moist environment. At these temperatures, formation, growth and development of fibrous and foil-like cementitious material was observed. XRD analysis provided no strong evidence for the formation of new phases. TEM analysis and EDAX, however, showed that the newly-formed fibrous and foil-like material consisted of an amorphous calcium silicate aluminate hydrate gel, similar to the gels formed during hydrothermal treatment of lime-silica, but with lower calcium to silicon ratios than previously reported for such gels. The morphological development of the gel suggested that it formed as a result of the progressive breakdown of the clay component in the soil by reaction with the calcium ions from the lime.

Fine clay, coarse clay, and silt fractions of four Bangladesh soils were studied using XRD, ion exchange, and selective dissolution techniques. Constants for the XRD intensity-weight proportion relationships were derived using these techniques. Smectite and mica were found to be dominant in Batra and Ghior soils, whereas kaolinite and mica were dominant in the Naraibag and Ghatail soils. Other minerals present were vermiculite, vermiculite with hydroxyaluminium interlayers, chlorite, randomly interstratified chlorite-mica, feldspar, quartz, and trace amounts of amphibole. The amorphous material content varied between 1 and 11% and decreased with increasing particle size. No crystalline iron oxides were detected in untreated clay fractions.

On a étudié les transformations minéralogiques des argiles et des biotites isolées d'un sol cryptopodzolique humifère du Plateau de Millevaches, France. Pour les argiles, la diffraction de rayons X fait apparaître un comportement intergrade de plus en plus prononcé de l'horizon C vers l'horizon A1. La nature des éléments extraits par les traitements citratedithionite et Tamura indique que ce comportement est lié à la présence d'aluminium interfoliaire pour les argiles de l'horizon A1Bh, mais également à des résidus de chlorite altérée pour celles de l'horizon A1. Pour les biotites, on observe un comportement aux RX très voisin de celui de la fraction argileuse. On peut mettre en évidence dans l'espace interfoliaire des biotites altérées la présence d'ions alumineux et de composés organiques.

The diagenetic history of the Rotliegendes Sandstone reservoir in the Rough Gas Field was studied using thin-sections, XRD analyses and SEM. The Rotliegendes comprises a sequence of fine-grained fluvial sheet-flood sandstones and coarse, gravelly, low-sinuosity channel sandstones, with thin aeolian interbeds, overlain by a sequence of aeolian dune and interdune sandstones. Early, environmentally-related diagnesis (eogenesis) shows a marked variability with sedimentary facies. Within aeolian sandstones, poikilotopic anhydrite and fine, rhombic dolomite are preserved. Fluvially-derived sandstones typically contain infiltrated detrital clays and early authigenic mixed-layer clays, together with coarse, framework-displacive dolomite. Feldspars show varying degrees of alteration within all facies. These eogenetic features reflect patterns of groundwater movement during the Rotliegendes and early Zechstein. Mineral dissolution and precipitation were controlled by the chemistry of the groundwaters. Burial diagenetic (mesogenetic) features are superimposed on eogenetic cements. Authigenic clays have been converted to illitic clays. In addition, mesogenetic chlorite has formed and quartz and strongly ferroan dolomite cements are recognized. These minerals may be related to clay diagenesis within the underlying Carboniferous Coal Measures. Early, framework-supporting anyhdrite, and both phases of dolomite, have been partially dissolved, creating secondary porosity. This is attributed to the action of acidic porewaters, generated by the maturation of organic material within the Carboniferous. Post-dissolution kaolinite, gypsum and minor pyrite infill secondary pores. Gas emplacement from the Late Cretaceous onwards effectively halted further diagenetic reactions.

Biotites from three peaty gleyed podzol soil profiles on ranite bedrock were examined to investigate the oxidation of the octahedral Fe during weathering. Oxidation of these biotites as determined by Mössbauer spectroscopy shows a good correlation with the in situ measured soil Eh values of the sampled horizons. In every soil profile the highest Eh measured is in the A horizon and the lowest in the C horizon. Similarly, biotites from the A horizons are the most oxidized compared with those from the lower horizons. In most of the samples the oxidation is accompanied by loss of K+ from the lattice, as demonstrated by a moderate degree of vermiculitization.

The surface free energy of Ca-montmorillonite has been determined from measurement of the contact angle of water on an oriented deposit immersed in n-alkanes; the oriented deposits were equilibrated at different relative humidities. These experiments provided the polar, γSP, and dispersive, γSD, components of the surface free energy γs. The results indicate that: (1) γs is mainly due to dispersive forces (γSD ≃ 145 mJ.m−2) and, to a lesser degree, polar forces (γSP ≃ 35 mJ.m−2). (2) The value of the apparent surface free energy of the clay, γα, tends towards that measured for water when the solid water content exceeds 50 wt%. (3) The sorption of water molecules substantially modifies the surface free energy of the solid; γs decreases from 180 mJ.m−2 to 60 mJ.m−2 when the water content increases from 0 to 50%. These results agree with other observations made on solids whose surface characteristics are similar to montmorillonite, i.e. micas, silicates and glasses. In addition, variations of γs with water content can be related to the hydration processes of smectites. Finally, these results show that the silicate no longer influences the surface properties when the montmorillonite water content exceeds 60%.

Clay from the Fuller's Earth formation is shown to contain mainly illite, kaolinite and calcite, in contrast to the Fuller's Earth Bed in which montmorillonite is the main clay mineral. A negative correlation has been demonstrated between the calcite content and the plasticity as measured by the Atterberg limits. Fresh samples from the Fuller's Earth Bed have a higher plasticity than those of the fuller's earth clay with similar calcite percentages, due to the relative increases in the expanding lattice clay mineral. Weathering of the fuller's earth clay typically reduces the calcite content and increases the percentage of montmorillonite, resulting in a higher plasticity.