The Lòn Ostatoin stream section, Trotternish Peninsula, Isle of Skye, exposes a sequence of Middle Jurassic mudstones and limestones which have been locally metasomatized by a transgressive sill of Tertiary age. Limestones in the sequence, including some previously reported as bentonite, have been altered to an unusual assemblage of grossular garnet and saponite clay. The mudstones also contain large proportions of saponite together with pyroxene and zeolites. Saponite also occurs within the basalt intrusion. Grossular and pyroxene represent artifacts of relatively high-temperature assemblages that formed during an early phase of alteration. As the intrusion and adjacent altered country rocks cooled, lower-temperature fluids flowed through a late set of contraction (micro)fractures. Back-reacted saponite, analcime and clinoptilolite were formed, possibly as alteration products of the unstable higher-temperature minerals. The lower-temperature mineral assemblage eventually sealed the late fracture system.

This paper highlights an important concept for the study of analogue sites used to investigate thermal effects on engineered liners or barrier host rocks for the landfill and radioactive-waste industries. This is that the original thermally altered mineral assemblage may be overprinted by later, lower-temperature back-reactions. A detailed understanding of both processes is necessary in order to construct a sensible model for the thermal and mineralogical evolution of the site.

Kaolinite deposits, hosted by rhyolitic tuffs, are found in the SE of the ‘Los Menucos’ area (Province of Rio Negro, Argentina). The most representative examples are from the Blanquita and Equivocada mines. To discover the origin of these deposits, a mineralogical, geochemical (major and trace element) and stable isotope study (O and H) of kaolinite was carried out. Mineralogically, Blanquita mine is characterized by the presence of dickite, kaolinite, alunite and pyrophyllite, whereas in Equivocada mine, kaolinite is accompanied by dickite and traces of alunite (without pyrophyllite). The trace element contents and ratios of kaolin samples (P vs. S, Zr vs. Ti, (Cr + Nb) vs. (Ti + Fe), and (Ce + Y + La) vs. (Ba + Sr)) suggest that they formed from the hydrothermal alteration of the enclosing rhyolites although a possible contribution of kaolinite from residual processes cannot be discounted. δ18O values of kaolinite range from +4.8 to +10.3‰, and δD varies from −88 to −116‰. The presence of pyrophyllite in Blanquita mine suggests temperatures of formation >350°C. The calculated isotopic composition of the fluid in equilibrium with kaolinite at 350°C varies from +3.6 to +9.2‰ for O and from −74 to −103‰ for H. These values are compatible with fluids of magmatic origin or with fluids of surficial origin isotopically equilibrated with a rhyolitic magma at high temperatures. The isotope composition of kaolinite from the Blanquita and Equivocada mines is clearly different from kaolinite of residual origin from deposits in the Chubut and Santa Cruz provinces. The isotopic signature has proved to be a useful tool in discriminating between different genetic processes in the formation of kaolin deposits.

The results of EPR, UV-VIS and IR spectral studies show that benzimidazole forms various complexes with Cu(II) exchanged in the interlayer space of montmorillonite, depending on the acidity of the reaction medium during synthesis. In a nearly neutral solution a bis(benzimidazole)bis(aqua) Cu(II) cationic complex is formed. In a strongly basic solution, benzimidazole is bound to Cu(II) in the form of an anionic bifunctional ligand and a planar intercalated bis(benzimidazolate) Cu(II) complex is formed, where the benzimidazolate anion acts as a bridging ligand in the polymeric complex. The treatment in basic solution leads to partial illitization of the smectite. In a strongly acid solution, a nearly stoichiometric ionic exchange of benzimidazolium ion for Cu(II) ions takes place in the interlayer space of montmorillonite.

The chemical and mineralogical compositions, the pore-diameter distribution, and the X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy of kaolin from Suzhou, China, and the physicochemical and catalytic properties of a catalyst prepared from that kaolin, are presented in this paper. Crystallized microspheres (CMR) containing ~30% NaY zeolite can be prepared from the Suzhou kaolin. The catalyst produced performs better than a standard commercial catalyst in terms of activity, attrition resistance, resistance to passivation by Ni and V and better gasoline and coke selectivity.

The performance of a fluidized cracking catalyst additive prepared from caustic-modified kaolin microspheres for gasoline S reduction was investigated using N2 adsorption, infrared acid-site characterization, X-ray diffraction and small-scale fluid bed reactor tests. The additive exhibited improved coke selectivity and yield distribution, and the S content of cracked gasoline was reduced significantly. The results indicated that a reactive mesoporous structure was formed in the modified kaolin.

Mica-chlorite mixed-layering was identified by X-ray diffraction (XRD) as a major or subordinate constituent in several slates of the Puncoviscana Formation from Sierra de Mojotoro (Eastern Cordillera, NW Argentina). In order to determine the crystallochemical characteristics of these mixed-layered sequences and interpret their petrological meaning, anchizonal slate P90 was chosen for TEM observations. In this slate, dioctahedral mica and chlorite form interleaved phyllosilicate grains (IPG) or stacks, up to 110 um long, preferentially oriented with (001) planes at a high angle to the slaty cleavage but also oblique to S0.

In agreement with XRD results, the main phyllosilicates identified by transmission electron microscopy (TEM) were dioctahedral mica and random mixed-layer muscovite-chlorite, with chlorite in subordinate amounts and scarce smectite. In the lattice-fringe images of mixed-layer packets, a sequence of irregular stacking that produced apparent 24 Å (10 + 14) layers was observed, but it was frequently possible to distinguish the 10 Å layers from adjacent 14 Å layers. In nearly all packets, 14 Å layers prevail, exhibiting 14 Å:10 Å ratios between 1:1 and 3:1. Some elongated lenticular fissures which are probably a consequence of layer collapse caused by the TEM vacuum were identified in these packets. The straight, continuous appearance of lattice fringes plus the scarce evidence of collapsed layers identified suggest that these packets correspond principally to mixed-layer muscovite-chlorite, which is confirmed by analytical electron microscopy analyses. However, smectite-like layers are probably the third component of some of these mixed-layer sequences, which may account for their high Si and low (Fe + Mg) contents, their low interlayer charge in relation to theoretical interlayer muscovite-chlorite, and for the presence of Ca in the interlayer site.

Textural relationships between chlorite and muscovite packets in IPG along with the observed transformations from 14 Å to 10 Å along the layer, is compatible with a prograde metamorphic replacement of chlorite in stacks by dioctahedral mica layers, probably in the presence of an aqueous fluid.

The Kawasaki and Dobuyama bentonite deposits in northeastern Japan show contrasting properties even though they are only 5 km apart in a sequence of Neogene sedimentary and pyroclastic rocks. The Kawasaki deposit consists of stratiform bentonite layers up to >50 m thick, and its wall rocks are unaltered shallow marine sedimentary rocks. In contrast, the Dobuyama deposit consists of a funnel-shaped ore body 200 m across, and its wall rocks are hydrothermally altered terrestrial rhyolitic pyroclastic rocks. The Kawasaki and Dobuyama bentonites mainly consist of Na-Ca smectite and Ca smectite, respectively, with subordinate opal-CT, quartz and zeolite. The geological occurrences of the deposits and wall-rock properties suggest that the Kawasaki and Dobuyama deposits were probably formed by diagenesis and low-temperature hydrothermal alteration, respectively. The difference in exchangeable cation ratios of the smectite between the two deposits is attributable to the difference in their sedimentary environments and/or burial depth.

The smectite-bearing red bed series of the Palaeogene Ergeliin zoo Formation in Mongolia is part of an alluvial-fluvial fan prograding over prodelta/mudflat deposits. The series was investigated in the field (mapping and portable infrared (IR) spectrometry in the short wavelength (SW) range) and samples were analysed in the laboratory using thin sections, X-ray diffraction, X-ray fluorescence, cation exchange capacity and Fourier transform infrared spectrometry in the mid-IR range. Two reference sections are treated in more detail as to the environment of deposition and concentration of smectite. The deposits at Ulaan uul are representative of a distal fan section with prevalent mudflats, whereas Ulaan buur offers insight into a braided river drainage system. Metabasic rocks in the hinterland delivered mica and chlorite from which smectite originated during diagenesis under semi-arid climatic and surface-near conditions. Towards the basin edge, smectite is replaced by kaolinite. The prime area in which we were interested in the smectite is the most distal part of the alluvial-fluvial fan, which was the subject of a field-based IR survey. This exploration method is a valuable tool to obtain a quick overview of the mineral composition and reduce the number of samples in the field for follow-up analyses. Its weak and strong points are discussed.

Syntheses of Na-magadiite were performed under hydrothermal conditions in a water/alcohol medium. It is only possible to obtain a pure and well crystallized magadiite sample using a water/ethanol medium at a water/ethanol molar ratio of ∼0.12. As shown by thermal analysis and 1H liquid nuclear magnetic resonance spectroscopy, ethanol is not incorporated into the magadiite. Intercalation of dodecyl- and hexadecyltrimethylammonium cations in the interlayer space of Na-magadiite at different theoretical ion-exchange rates shows that the experimental ion-exchange rates are in good agreement with the theoretical ones. However, scanning electron micrographs of the sample having a theoretical ion exchange rate of 25–75% shows that the exchanges are not homogeneous (both thin and thick platelets are present). Attempts to obtain a Si-pillared compound starting from C16TMA-magadiite as the host material leads to a microporous compound having a BET surface area of 778 m2g-1.