A 65 m thick altered volcanic profile was studied in the Cava di Caolino (Lipari Island) in order to (1) identify the alteration event(s), (2) model these events, and (3) propose estimates of the degree of chemical alteration (CIA, chemical index of alteration). Two mineral parageneses were identified: one comprising silico-aluminous phases, with well crystallized kaolinite (type 1), and the other comprising sulphates, with kaolinite as fracture infilling (type 2). The geochemistry of fluids analysed from a local hot spring (40°C, pH ≈ 8) allowed modelling of the observed silico-aluminous paragenesis. A later fumarolic event is suggested to be responsible for the sulphate paragenesis. The main stage of hydrothermal alteration lasted for ~50 ky, was marked by an increase in the CIA from the protolith (~52) to the alterites (~98), and resulted in the alteration of a 65 m thick series. Such data could be used to predict the alteration of volcanic rocks around underground nuclear waste repositories.

K-Ar ages of Eocene glauconite pellets from the Isle of Wight are related to quantified amounts of older glauconite pellets and to occurrences of detrital mica/illite particles that might have been added to synsedimentary pellets during reworking processes. Addition of older glauconite did not significantly bias the K-Ar dates, as the results most often provide the expected stratigraphic reference ages or even significantly lower ages. Alternatively, K-Ar dates significantly greater than those suggested by the stratigraphy appear to result from non-glauconized detrital mica in the pellets which is not always removable, even by high-gradient magnetic separation.

Unexpected ‘old’ K-Ar glauconite ages do not result from misapplication of the method, but from inability to systematically identify and remove the `contaminant' particles from glauconite splits. Analysis of highly evolved glauconite separates is definitely appropriate for reliable isotopic age determinations, but it might not be enough for the final selection, as long-lasting diagenesis might have taken over the synsedimentary process. Much if not all depends on the separation and characterization of the separates, but also on the completion of the glauconitization process which effects cannot always be anticipated.

The fluorine route is thoroughly investigated for the hydrothermal synthesis of montmorillonite in the Na2O-MgO-Al2O3-SiO2-H2O system. Using the optimal conditions suggested by Reinholdt et al. (2001) for the crystallization of pure montmorillonites with the formula Na2x(Al2(1-x)Mg2x☐)Si4O10(OH)2, several parameters (x, Mg content, duration of crystallization, F/Si atomic ratio, pH, nature of counterbalance cation) are varied independently from their ideal values. The products are analysed by various techniques (X-ray diffraction, thermogravimetric analysis-differential thermal analysis, 29Si, 27Al and 19F magic angle spinning-nuclear magnetic resonance). It appears that a pure montmorillonite can only be obtained within a narrow x range (0.10 ≤ x ≤ 0.20). The presence of F in the starting hydrogel and the crystallization time also have significant effects on the purity of the final products. It is shown that a small amount of fluorine is needed for the crystallization of pure montmorillonite phyllosilicates.

Clay minerals of calcareous sedimentary rocks of southern Iran, part of the old Tethys area, were investigated in order to determine their origin and distribution, and to reconstruct the palaeoclimate of the area. Chemical analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and thin-section studies were performed on the 16 major sedimentary rocks of the Fars and Kuhgiluyeh Boyerahmad Provinces.

Kaolinite, smectite, chlorite, illite, palygorskite and illite-smectite interstratified minerals were detected in the rocks studied. The results revealed that detrital input is possibly the main source of kaolinite, smectite, chlorite and illite, while in situ neoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks.

The presence of a large amount of kaolinite in the Lower Cretaceous sediments and the absence or rare occurrence of chlorite, smectite, palygorskite and illite are in accordance with the warm and humid climate of that period. Smaller amounts of kaolinite and the occurrence of smectite in Upper Cretaceous sediments indicate the gradual shift from warm and humid to more seasonal climate. The occurrence of palygorskite and smectite and the disappearance of kaolinite in the late Palaeocene sediments indicate the increase in aridity which has probably continued to the present time.

Clay materials play a key role in determining the retention capacity of a soil, and are widely used in waste treatments. One of the most commonly used clays is palygorskite. The aim of this research is to determine the chemical species formed by Zn when retained in a palygorskitic clay material. Adsorption isotherm analysis is useful in studying the retention process, because it provides a macroscopic view of the retention phenomena. Complementary techniques are needed in order to study the different retention processes. Sorption isotherms of Zn on palygorskitic clay were carried out; the supernatant was analysed by means of dynamic light scattering (DLS) and the residues by using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive angle X-ray (SEM-EDAX)analysis and extended X-ray absorption fine structure (EXAFS). Isotherm analysis shows that the global retention process could be due to the sum of two separate processes, adsorption and surface precipitation via solid-solution. This is supported by DLS, which shows that ζ potential increases as the Zn(II) is retained onto clay surfaces but remains constant during the precipitation process. The XRD pattern corresponding to the Zn-clay system showed weak new peaks, probably from zincite. The microanalysis by X-ray fluorescence of several spots selected for their different electronic densities indicated that the retained Zn was randomly distributed across the clay surface. Analysis by EXAFS supports the hypothesis of retention via adsorption and solid-solution surface precipitation.

CP (Cetylpyridinium)-exchanged smectite was manufactured by the cationic exchange reaction of Na-smectite with CP. The adsorption behaviour shows a typical L-type isotherm representing continuous and stable adsorption in excess of twice the cation exchange capacity of CP. CP-smectite shows a strong interlayer (d001) expansion to 40.2 Å when an amount of CP equivalent to 140% of the CEC is exchanged into smectite. CP-smectite is characterized by strong alkalinity (pH 9.3), low swelling (4.5 ml/2 g), low viscosity (3.9 mPa s), and strong and fast flocculation. These characteristics are in striking contrast to Na-smectite except for the alkalinity. CP-smectite shows no signs of desorption of the organic species under varying pH conditions (pH 2–12). Desorption is slight even when washed three times with DH2O (distilled water). Pyrolysis of CP-smectite begins at 250°C and ends at 400°C. These stable and persistent characteristics and the relatively low price of CP point to the likely increased use of CP-smectite as an organoclay.

The adsorption of the large cationic alkaloid berberine by montmorillonite in aqueous suspensions was investigated. An adsorption isotherm of berberine and desorption isotherms of exchangeable Na+, K+, Mg2+ and Ca2+ were determined by chemical analysis of the non-adsorbed berberine and the released cations in the supernatants. The isotherms suggest that the adsorption of berberine takes place in two different types of reaction mechanism: (1) cation exchange, and (2) a secondary organophyllic adsorption. The cation exchange occurring first is followed by the secondary adsorption which is accompanied by Cl- adsorption. Monovalent cations are exchanged before the divalent cations.

Samples loaded with increasing amounts of berberine were examined by X-ray diffraction at room temperature, and after gradual heating up to 420°C. The basal spacing of the loaded samples after the thermal treatment became 1.28 nm, indicating the formation of carbon in the interlayer, thus proving that the adsorbed berberine was located in the interlayer space. At room temperature the basal spacing of samples loaded with 8 and 15 mmol of berberine per 100 g of clay was 1.28–1.30 nm indicating that in the interlayer space berberine cations were lying parallel to the alumino-silicate layers. The basal spacing of a sample with 36 mmol of berberine per 100 g of clay was 1.48 nm. This spacing does not give conclusive information on the arrangement of berberine in the interlayer. The spacing of samples with 57–147 mmol of berberine per 100 g of clay was 1.59 nm, suggesting the presence of bilayers of berberine in the interlayers. During thermal dehydration, the spacing of samples with 36–73 mmol of berberine per 100 g of clay decreased, but that of samples with 105–147 mmol of berberine per 100 g of clay increased to 1.66 nm. These samples contain organophilic adsorbed berberine and it is suggested that due to the thermal treatment berberine was tilted relative to the TOT lamellae, with anhydrous Cl- between the berberine cations.

The intercalation of the cationic surfactant cetyltrimethylammonium (C16TMA) into the interlayer of an acid-activated clay in the presence of different anions has been studied in detail. When Br or OH anions were used, the basal spacing increased significantly, the increase being related to the loading concentration of the surfactant solution. For intercalated compounds prepared from the hydroxide form, the basal spacing at room temperature varied from 1.6 to 3.8 nm. However, for organoclays prepared from the surfactant bromide, the basal spacing is almost loading- independent (1.9 nm). The use of hydroxide and bromide at higher pH is crucial to intercalating larger amounts of C16TMA cations and, hence, to improving the exfoliation of the silicate sheets. Magic-angle spinning 13C nuclear magnetic resonance spectroscopy indicates that the intercalated surfactants exhibit a significant degree of gauche conformation. According to in situ powder X-ray diffraction, an increase of the basal spacing to 4.08 nm is observed at intermediate temperatures of 50 to 150°C for organoclay with an initial basal spacing of 3.7 nm. At higher temperatures, decomposition of the surfactant occurs and the basal spacing decreases to ~1.4 nm.

In a study of wall-rock alteration in the 1.4 km long Würmtal adit at the Käfersteige hydrothermal vein deposit (northern Black Forest, Germany) illite was found to be the only clay mineral within the Bunter sandstone and intercalated claystone. Illite occurs mainly as a detrital mineral in the claystone, whereas it is hydrothermally neoformed in the sandstone, either in the pores or as an alteration product of K-feldspar. The extensive occurrence of authigenic illite along the entire 1.4 km long profile confirms that the fluids migrated far into the sandstone.

The authigenic illite formed during a first pulse of high-temperature fluids (Th of ~220°C) with a low salinity (~1 wt.% NaCleq). These fluids also dissolved Sr and Rb from detrital illite of the claystones at the vein. A later hydrothermal pulse with a lower temperature (~70–150°C) and higher salinity (21–28 wt.% NaCleq) silicified the sandstone adjacent to the vein and caused partial substitution of OH- by F- in the structure of the detrital and neoformed illite along the profile.

Within analytical error, the K-Ar dates for the neoformed illite of the <2 µm fraction are the same along the profile (~150 Ma). During this hydrothermal process, the age of the detrital illite within the claystone was reset from 310 to 190 Ma. The illite-rich <0.2 µm fractions yield ages of ~142 Ma (sandstone) indicating a Jurassic origin. The uniform age data for illite in the sandstone and in the claystone are probably due to extensive migration of hot fluids through the wall rocks.

The hydrothermal fluids are attributed to recycled meteoric water and brines that ascended from the basement into the cover rocks during the opening of the North Atlantic and/or the nearby Tethys area.