A study has been made of the relative abundance of clay minerals in about a hundred samples of sedimentary rocks of Pre-Cambrian, Cambrian, Upper Carboniferous, Permian, Triassic, Jurassic, Lower and Upper Cretaceous and Tertiary formations in the geosynclinal basin of the (Tethys) Himalayan zone. Chlorite predominates in the Cambrian sediments and illite in the Permo-Carboniferous to Tertiary sediments; kaolinite is a minor variable component and montmorillonite is scarce. The high-chlorite Cambrian sediments are rich in dolomite and gypsum and contain predominantly plagioclase felspars, whereas the high-illite Triassic and Eocene sediments are rich in alkali felspars, the dolomite is low and gypsum is absent. In the (newer) Tertiaries of the Middle Miocene age (fluviatile deposits in shallow freshwater basin) illite, kaolinite and montmorillonite are present in almost equal amounts but chlorite is undetectable. The predominance of kaolinite and montmorillonite in the sediments of the Lower Pleistocene period indicates the existence of a distinctly fluviatile facies in the basin of deposition. Interstratified illite-montmorillonite and montmorillonite are characteristic of Siwalik (Miocene) sediments and of Spiti-shale type Jurassic sediments.

The anthropogenic accidents in the world (including the underground emergency nuclear explosion at the site “Kraton-3” (Yakutiya) and also the recent Fukushima accident) resulted in significant environmental pollution by radionuclides, mainly long-lived 90Sr and 137Cs. One of the ways to solve this problem is the creation of “permeable reactive barriers” (PRBs). High selectivity of clinoptilolite-containing tuffs (CLT) towards Sr2+ and Cs+ radionuclides, together with their availability and reasonable cost, make possible their use as PRBs. The scales of the ion-exchange processes taking place on PRBs indicate the necessity of mathematical modelling. In this connection, Sr2+ and Cs+ ion-exchange sorption on Khonguruu CLT (Yakutiya) from solutions of various mineralizations was studied under equilibrium and non-equilibrium conditions. The physicochemical and mathematical models of the dynamic ion-exchange process and also the computer program considering both structural features of CLT (two-stage particle diffusion kinetics) and possible periodic interruptions of the process were developed. The breakthrough time of CLT as a geochemical barrier was calculated by such mathematical modelling.

Electron microscopy was used to study swollen samples of n-butylammonium vermiculite prepared in dilute aqueous solutions of n-butylammonium chloride. Three electrolyte concentrations were studied, 0.1 M, 0.01 M and 0.001 M. The 0.1 M samples studied were in a taetoid phase, exhibiting crystalline legions of about ten layers separated by large irregular aqueous regions. The dilute samples were studied in their gel phase, exhibiting regular spacings of 85 nm and 55 nm in the 0.001 M and 0.01 M solutions, respectively. These spacings are much larger than those measured previously by neutron scattering, probably due to an additional expansion of the interlayers during the freezing process employed in preparing the replicas. In all examples, the structures were found to be lamellar over regions of several microns.

Clay mineral assemblages from a Quaternary sequence, sampled near the estuary of the Arno River, commonly contain some intergrade minerals, associated with other 14 Å phases and with illite and subordinate amounts of a kaolin mineral. The X-ray diffraction characteristics of such intergrade phases and their thermal modifications (100–600°C) are analysed and described.

The effectiveness of some chemical treatments for removal of interlayer material is investigated and the results discussed on the basis of X-ray diffraction pattern and C.E.C. changes. Finally the properties of these intergrades are compared with those of the 14 Å phases present in the sediments carried by the Arno River and its tributary the Era River as well as with those of a soil from the Era watershed. Hypotheses are expressed about the probable relationships between degree of chloritization and characteristics of the depositional environments.

The influence of kaolinite and montmorillonite on the identification of pseudoboehmite was studied by X-ray diffraction (XRD), differential thermal analysis (DTA), infrared absorption (IR), and transmission electron microscopy (TEM). In the randomly oriented samples containing different proportions of the clay minerals and pseudoboehmite, pseudoboehmite was not easily detectable by XRD even in a sample containing 40% of pseudoboehmite. Preheating of the samples at 110-300°C improved the detection limit to 30%. In samples obtained by mixing suitable amounts of the suspensions of the clay minerals (<2 μm) and pseudoboehmite, the identification of pseudoboehmite was even more difficult. In oriented samples, pseudoboehmite was detectable only when present in amounts >30%, at low full-scale counts per second (1000-400 cps), on preheated samples in the presence of kaolinite, or on the samples that were Mg-saturated and solvated with ethylene glycol in the presence of montmorillonite. Identification of pseudoboehmite in the presence of kaolinite or montmorillonite by DTA, IR or TEM failed, even in samples containing 50% pseudoboehmite. In the presence of both kaolinite and montmorillonite (1:1 w/w), the identification of pseudoboehmite became much more difficult than in the presence of either mineral alone. The presence of pseudoboehmite in soils may, thus, be undetectable by standard clay mineralogical analyses.

Dolerites from the Sierra de San Pedro (Betic Cordillera, southern Spain) develop three main types of microsystems during hydrothermal alteration: (1) centimetre-sized veins cross-cutting the dolerites; (2) microfractures in feldspar and diopside grains; and (3) alterations involving primary-igneous mafic phyllosilicate grains. The vein and microfracture sites developed alteration assemblages of randomly oriented smectites (saponite and beidellite) and halloysite. At these sites, the alteration mechanism was governed by complete dissolution of the parent material with subsequent crystallization of the products, with no parent-mineral crystallographic control. Pseudomorphed mafic phyllosilicate sites are characterized by oriented complex mineral assemblages made of chlorite, chlorite/smectite mixed layers, corrensite, saponite and relicts of biotite. These assemblages formed during the initial high-temperature stage of the hydrothermal process. In these microsites, the alteration sequence was controlled by the parent-mineral structure and chemistry, with products determined by structural relations with the parent phyllosilicate. Alteration of one phyllosilicate to the next most stable proceeds via interstratification of the parent and product phyllosilicates.

Organo-bentonites were prepared using a bentonite and an aqueous cetyltrimethylammonium hydroxide solution. The ratio of the surfactant (in mmoles) to the cation exchange capacity varied from 0.5 to 20, with 20 being the highest ratio ever reported in the literature. At high surfactant to cation exchange capacity ratios, the interlayer spacing increased to 3.75 nm due to the formation of a paraffin-type bilayer of surfactant cations, which was shown to be mainly in gauche conformations using solid state 13C CP/NMR. When the exchange reaction was carried out in a methanol-water mixture, the expansion of the organo-bentonites depended on the concentration of methanol (% by volume). The decomposition temperatures of the organic cations depended on the basal spacing of the organo-bentonites, and in situ X-ray diffraction revealed that the basal spacing of our organo-bentonites was stable up to 210°C. Above this temperature, the basal spacing shrunk to 1.47 nm due to decomposition of the surfactants.

Early Copper Age pottery sherds discovered in a cave within the crystalline dolomites of the Southern Carpathians (Romania) were investigated by polarized light optical microscopy (OM), X-ray powder diffraction (XRPD) and electron microprobe analysis (EMPA) to obtain information on the pottery production in the Copper Age in the territory of present-day Romania. Microscopically, the clayey matrix of the ceramic body is highly birefringent or consists of low-birefringent and isotropic parts mixed together, containing fragments of quartz, muscovite, alkali feldspar, plagioclase, biotite, chlorite, heavy minerals and metamorphic and magmatic rocks, as well as an opaque material. The EMPA data revealed an Fe-rich illite-like matrix and helped to identify the mineral nature of the inclusions. Local pottery production in bonfires or surface clamps is envisaged. Miocene illitic clays may have been used as raw materials, mixed with a small amount of sandy temper. The thermal changes revealed by OM, the modification of the XRPD peaks and the EMPA data suggest firing temperatures of between 800 and 850°C.

Modelling of experimental X-ray diffraction (XRD) patterns is used to determine the phase composition of partially dehydroxylated kaolinite samples. To identify unambiguously the presence of two or three phases in the heated kaolinite samples, the full range of their XRD patterns has to be analysed. Two different kaolinites, from Imerys (UK) and from Georgia (USA; KGa-21), were studied. The heating temperatures were selected to cover the entire range of dehydroxylation for both kaolinites (400–550°C for Imerys and 400–495°C for KGa-21). Two different dehydroxylation pathways were observed. At each stage of partial dehydroxylation, the kaolinite from Imerys consisted of the original, non-dehydroxylated kaolinite and of a fully dehydroxylated phase, metakaolinite. During partial dehydroxylation of kaolinite KGa-21, each product formed at a given heating temperature consisted of three phases: the original kaolinite; a dehydroxylated phase, metakaolinite; and a phase with diffraction features corresponding to a defective kaolinite-like structure. To determine the content of metakaolinite in a partially dehydroxylated specimen, its experimental XRD pattern was reproduced by the optimal summation of the diffraction patterns of the initial kaolinite and metakaolinite. A procedure that reveals the basic diffraction features of the third phase is suggested. The XRD patterns and thus the structures of the metakaolinites formed after dehydroxylation of the Imerys and KGa-21 samples differ substantially. The conventional determination of the initial kaolinite and metakaolinite contents in partially dehydroxylated kaolinite based on the analysis of basal reflections and weight losses may lead to overlooking the formation of the intermediate phases.

In deep geological repositories, compacted bentonites have been proposed for use as barrier materials for isolating nuclear waste. The prevailing thermo-hydro-mechanical boundary conditions in the repositories may affect the swelling capacity and permeability of the compacted bentonites. In this study, the effect of preliminary desiccation on the subsequent hydro-mechanical behaviour (swelling pressure and hydraulic conductivity) of compacted Calcigel bentonite was investigated experimentally at 22°C and 80°C. In the first stage of the test, the compacted specimens were subjected to suction-controlled desiccation at 22°C and 80°C using the vapour-equilibrium technique. After the water content reached equilibrium at a given suction, the axial, radial and volumetric shrinkage strains were measured. Afterwards, constant-volume swelling-pressure tests were performed on the desiccated specimens (second test stage) by saturating the dried specimens with deionized water at 22°C and 80°C. At the end of the swelling-pressure test, the hydraulic conductivities of four saturated specimens were measured at each temperature. The volumetric shrinkage strain of the compacted bentonite during desiccation is controlled by suction instead of temperature. In addition, the preliminary desiccation increases both the swelling pressure and hydraulic conductivity of compacted bentonite, particularly if compacted bentonite undergoes extreme desiccation at an applied suction of >700 MPa.

K-Ar isotopic dating of very low-grade metamorphism affecting Triassic-Jurassic rocks in the Coastal Range of central Chile was carried out on whole rocks and their <2 mm size fractions. In the study area, a regional-burial low-grade metamorphism at anchizone conditions (T ≤190°C) and low-pressure conditions (P ≥1.3 kbar) has been described. The highest observed temperatures are related to a contact metamorphism produced by nearby Jurassic intrusions, with a P-T estimate at the immediate contact zone of ~650–690°C and 4 kbar.

The whole-rock K-Ar age of 174±5 Ma is interpreted as belonging to the contact metamorphism due to the intrusion of Jurassic plutons (165±5 Ma to 175±5 Ma). A time-interval of ~20 Ma between the diagenesis (206 Ma) and the anchizonal very low-grade metamorphism (181–184 Ma) is obtained, and a rate of subsidence of ~120 m/Ma is proposed for these Triassic-Jurassic basins. A thermal influence on the burial, very low-grade, regional metamorphism is invoked.

The morphology and fabric of kaolin weathered from a non-feldspathic mica-phyllite in Znojmo, Moravia, are illustrated in scanning electron micrographs. In contrast to accordion-like kaolinite books, or elongate halloysite(?) crystals, commonly developed from feldspar, the kaolinite from the mica-phyllite tends to be individually platy, with highly irregular edges resulting from multiple adjacent crystal comers and re-entrants. Irregular or impaired crystal growth of kaolinite from mica may be due to ‘poisoning’ of kaolinite crystals by vanadium that is common in mica.

In a study of sandstones from the Coal Measures (Westphalian A and B) of the East Midlands, UK, fibrous illites exhibiting random core and lath structures were observed during SEM examination of material dried in air, but not during TEM examination of ultrathin sections made from the same material. Previous studies have reported random core and lath structures during TEM examination of extracted clay material and it is suggested that they are an artefact of the specimen preparation technique.

L'eau présente dans les divers types de pores que contiennent des solides divisés a été étudiée par calorimétrie à balayage entre 200 et 270° K et sa chaleur spécifique a été mesurée entre 100 et 260° K. Les solides étudiés sont des argiles de la famille des smectites, l'endellite, des zéolites et une opale.

Les informations obtenues à l'aide de ces techniques sont comparées à celles dérivées d'autres techniques notamment la résonance magnétique nucléaire et la spectroscopie infra-rouge.

Des différences intéressantes sont observées entre des agrégats tri et bidimensionnels de molécules d'eau.

Trachyandesite rocks, occurring over an area of about 1 km2 in the southwest part of Limnos Island, Greece, are altered mainly to halloysite. The samples were collected and analysed by polarizing microscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analysis. The alteration of plagioclase to halloysite follows seven discrete stages that are described in detail. The geochemical evaluation of the data shows enrichment of the light REE (LREE) over heavy REE (HREE) as expressed by the (La/Yb)n ratio. The ΣLREE range from 206.44 to 272.30, while the sum of HREE varies from 11.01 to 26.26. The (La/Yb)n ratio ranges from 9.72 to 27.64. Fractionation among LREE expressed as (La/Sm)n and between middle REE (MREE) and HREE is shown as (Tb/Yb)n ratios. The most altered rocks close to the fault zone have high (Tb/Yb)n ratios and low (La/Sm)n and Eu/Eu* ratios. Although mineralogy and clay mineral textures indicate hydrothermal genesis of halloysite, the geochemical data are not conclusive due to a secondary weathering effect.

The desorption of tetrahydropyran (THP), tetrahydrofuran (THF) and 1,4-dioxan (DIOX) from Na+-, Ca2+-, Al3+- and Cr3+-exchanged montmorillonite has been studied using variable temperature infrared spectroscopy and thermogravimetric analysis. The derivative thermograms for the desorption of each cyclic ether exhibited three maxima but there was little uniformity in the temperatures at which these maxima occurred. Nonetheless, the desorption of both THP and THF occurred at lower temperatures in the Cr3+-exchanged form than in the Al3+-form. The desorption of DIOX showed little cationic dependence. Mass spectroscopic analysis of the thermally evolved vapours indicated that no transformation products were desorbed at temperatures ⩽230°C.

Des montmorillonites cuivriques ont été exposées à des vapeurs de benzène, au cours de cycles de déshydratation, adsorption, désorption de l'excès et réhydratation. La fixation du benzène et sa transformation dans les espaces interfoliaires ont été suivies au moyen d'analyses thermogravimétriques, radiocristallographiques et spectrophotométriques infrarouges. Celles-ci ont permis de mettre en évidence deux réactions, correspondant l'une à l'adsorption d'une molécule de benzène par ion Cu2+, l'autre à trois molécules de benzène. Ce dernier se polymérise dans les espaces interfoliaires avec formation tout d'abord de poly (p-phénylène) puis d'un composé qui pourrait s'apparenter à du graphite.

Rheological, porosimetric, and SEM studies of cements with additions of natural zeolites (chabazite, mordenite and clinoptilolite) were investigated. The addition of 5% zeolite to cement pastes had a plastifying effect. The increase in the rheological parameters of aqueous cement–zeolite suspensions began after additions of more than 10% zeolite. At a water/solid ratio (w/s) = 0.5 all compositions exhibited similar rheological behaviour for yield stress and maximum shear stress values. At lower w/s values the rheology depended on the zeolite used, decreasing in the order Sl (clinoptilolite, Nižny Hrabovec deposit, Slovakia), M (mordenite, Philipines), Bp (clinoptilolite, Beli Plast deposit, Bulgaria), NM (clinoptilolite, Saint Cloud deposit, New Mexico) and Ch (chabazite, Nasm Yan deposit, Korea).

After 28 days of hydration the mixtures containing 10% Bp clinoptilolite, mordenite, and Sl clinoptilolite (up to 30%) had unchanged specific pore volumes but additions of 10% and 30% of chabazite and NM clinoptilolite and of 30% mordenite and Bp clinoptilolite lead to increases in the total specific pore volume compared to the neat cement paste. Between the 28th and 180th days of hydration the specific volume of the pores in all the cement-zeolite pastes decreased due to the filling of the pores with products from the pozzolanic reaction between the zeolites and the hydration products of the cement.

The pozzolanic reaction between zeolite and the hydration products of cement is enhanced by the zeolite content in the samples and depends on the Si/Al ratio (clinoptilolite (Si/Al >4.5), mordenite (Si/Al >5), chabazite (Si/Al <2.5)) and the surface area (clinoptilolite from Slovakia has the smallest crystallites and, hence, the greatest reactive surface area).