The Landshut bentonites that formed from Ca- and Mg-poor rhyolitic tuffs in a fluviatile-lacustrine depositional environment of the Miocene Upper Freshwater Molasse, southern Germany, contain abundant palustrine, pedogenic and groundwater carbonates. Geochemical analyses of dolomites, calcites and smectites from bentonites of various environments by X-ray diffraction, thermal ionization mass spectrometry, inductively coupled plasma-mass spectrometry, and handheld X-ray fluorescence yield new insights into the compositions of fluids and sources of imported components involved in carbonate formation and bentonitization, as well as the timing of bentonite formation. Evaporated, Sr-rich brackish surface water with a molar Mg/Ca ratio of 2–5, derived mostly from the weathering of detrital carbonates, was involved in dolomite and bentonite formation in palustrine and some pedogenic environments. However, Sr-poor groundwater with a molar Mg/Ca ratio of ∼ 1 and a stronger silicate weathering component caused bentonite and calcite formation in strictly pedogenic and groundwater settings. The 87Sr/86Sr and molar Mg/Ca in the smectite interlayers indicate later cation exchange with water having more radiogenic Sr sources and smaller molar Mg/Ca ratios. The Rb-Sr data indicate the common presence of detrital illitic phases in the <0.2 μm fractions of the bentonites. Cogenetic palustrine dolomite and a single smectite residue sample which lacks this detrital illitic phase provide an age constraint for bentonitization at 14.7 ± 4.1 Ma identical to primary ash deposition. Thus a rapid onset of bentonitization of accumulated ash and dolomite formation in evaporation-driven wetland environments is indicated for the genesis of the Landshut bentonites.

This study focused on the mineralogical and physico-chemical properties of heulandite/clinoptilolite (Heu/Cpt)-rich zeolitic tuffs SE of Ankara (Turkey) and evaluated their potential for use as adsorbents. The main Heu/Cpt minerals correspond to the intermediate type and the Cpt-type of the heulandite series. Minor chabazite, erionite and rarely analcime and accessory feldspars, mica, smectite, and quartz were also detected. Three types of Heu were recognized according to their thermal behaviour. Cpt (type-III Heu) was thermally stable at 600°C, whereas type-I Heu collapsed and type-II Heu partially collapsed. The Si/Al ratios of the Hul/Cpt ranged from 3.54 to 5.03, the Γ parameter (Γ = Ca/Al + 0.115*Al) varied between 0.78 and 1.85 and Al + Fe3+ varied between 6.27 and 8.00. The Na, K and Ca contents of Heu/Cpt varied widely and the Heu had an intermediate composition between types II and III. The Mg + Ca content is greater than the Na + K content in Heu-type II and smaller in Heu-type III zeolites. The BET surface area and the pore-size of the samples varied between 10.15 and 194.27 m2/g, and between 1.41 and 12.42 nm, respectively. The N2 adsorption and desorption isotherms were comparable, but the adsorption/desorption capacity is greater in type III than in type II Heu zeolites. The cation exchange capacities of the Heu/Cpt-rich samples ranged from 185 to 280 meq/100 g.

[Zn-Al] layered double hydroxides (LDH) with cationic molar ratios of R = Zn/Al 1–5 were synthesized by the coprecipitation method at constant pH = 10. The samples synthesized and their derived forms obtained after calcination at 500°C and at 900°C (denoted Zn-Al-R, Zn-Al-R-500 and Zn-Al-R-900, respectively), were characterized by X-ray diffraction (XRD), inductively coupled plasmamass spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, diffuse reflectance spectroscopy and nitrogen physisorption at −196°C. The XRD study showed: (1) the presence of accessory ZnO with the LDH in samples synthesized with R ≥ 3; and (2) the lamellar structure was destroyed at 500°C which made room for a poorly ordered ZnO phase, while calcination at 900°C yielded well crystallized ZnO and ZnAl2O4. The photocatalytic activity of the calcined and the unheated samples was evaluated for the decolourization of methylene blue. The photocatalytic activity was dependent on the cationic ratio R and on the calcination temperature. The sample Zn-Al-3 displayed maximum photocatalytic activity. Calcination at 500 and 900°C improved the photocatalytic activity of LDH synthesized at R = 1 and 2.

The present study examines the characteristics of clay minerals in shale gas reservoirs and their influence on reservoir properties based on X-ray diffraction and scanning electron microscopy. These analyses were combined with optical microscopy observations and core and well-log data to investigate the genesis, distribution characteristics, main controlling factors and pore features of clay minerals of the Lower Silurian Longmaxi Formation in the East Sichuan area, China. The clay mineral assemblage consists of illite + mixed-layer illite-smectite (I-S) + chlorite. This assemblage includes three sources of clay minerals: detrital, authigenic and diagenetic minerals. The lower section of the Longmaxi Formation in the Jiaoshiba area has sealing ability which resulted in abnormal high pressures during hydrocarbon generation which inhibited illitization. Therefore, an anomalous transformation sequence is present in which the mixed-layer I-S content increases with depth. This anomalous transformation sequence can be used to infer the existence of abnormal high pressures. The detrital components of the formation also affect the clay-minerals content indirectly, especially the abundance of K-feldspar. The transformation of mixed-layer I-S to illite is limited due to the limited availability of K+, which determines the extent of transformation. Three types of pores were observed in the shale reservoir rocks of the Longmaxi Formation: interparticle (interP) pores, intraparticle (intraP) pores and organic-matter pores. The clay-mineral content controls the development of intraP pores, which are dominated by pores within clay particles. For a given clay mineral content, smectite and mixed-layer I-S were more conducive to the development of shale-gas reservoirs than other clay minerals.

Interest in mineral–microbe interaction has grown enormously over recent decades, providing information in a puzzle-like manner which points towards an ever increasingly intimate relationship between the two; a relationship that can be truly termed co-evolution. Clay minerals play a very central role in this co-evolving system. Some 20 years ago, clay scientists looked at clay mineral–microbe studies as a peripheral interest only. Now, can clay scientists think that they understand the formation of clay minerals throughout geological history if they do not include life in their models? The answer is probably no, but we do not yet know the relative weight of biological and inorganic factors involved in driving clay-mineral formation and transformation. Similarly, microbiologists are missing out important information if they do not investigate the influence and modifications that minerals, particularly clay minerals, have on microbial activity and evolution. This review attempts to describe the several points relating clay minerals and microorganisms that have been discovered so far. The information obtained is still very incomplete and many opportunities exist for clay scientists to help to write the real history of the biosphere.

Resonance energy transfer (RET) in hybrid polymer/inorganic/organic layers in saponite films, prepared using the ‘layer-by-layer’ (LBL) method, was studied. This method allows the fabrication of a multicomposite molecular assembly based on electrostatic and/or other intermolecular interactions between the interacting species. The LBL films were designed by sequential deposition including positively charged polycations ( poly(diallyldimethyl ammonium), PDDA) and negatively charged saponite dispersions with donor molecules (rhodamine 6G) and saponite dispersions with acceptor molecules (rhodamine 3B). In this sequence, the layer of saponite donor molecules was placed on an adjacent layer of saponite acceptor molecules, while the layers were separated by inserting a PDDA polycationic layer. The adsorption process was studied using absorption spectroscopy. The linear deposition regime was completed when ten layers had been deposited. The process of REF was studied by fluorescence spectroscopy. In this case the donor molecules – rhodamine 6G – play the role of lightharvesting antennae and transfer the energy to the next layer covered by energy acceptor, i.e. rhodamine 3B molecules. The insertion of polycation layers is rationalized by the adhesion of negatively charged underlying layers and the stabilization of multicomponent systems. The energy transfer efficiency was affected heavily by changing the distances between the adjacent layers.