Smectite Minerals Research Articles

IDENTIFIKASI GUGUS FUNGSI DAN KANDUNGAN MINERAL LEMPUNG PACITAN DENGAN SPEKTROSKOPI INFRA RED (IR) X-RAY DIFFRACTION (XRD)

Clay is natural mineral from silicate family like crystal which has approximately 2 micrometer. There are two component unit of atom in clay mineral. One consists of oxygen or hidroksida with alumunium, iron or magnesium that coordinated in octahedral system. Others, it is tetrahedral system from silicon with oxygen or hidroksida. Based on IR analysis, it can be known that metal─OH bending vibrations it can be seen at 912,3 cm─1 wavelength. On the other bands between 694,3 and 754,1 cm─1 that are Si─O bending vibrations. X-Ray Diffraction (X-RD) analysis be seen main peak at 2 = 5,70o (d001=15,48 Å) and 2 = 20,02o (d001=4,43 Å). That are for smectite mineral kind montmorillonite as main unit in clay from Pacitan

Experimental studies on the gold-in-calcrete anomaly at Edoldeh Tank Gold Prospect, Gawler Craton, South Australia

Calcrete sampling is the near-surface exploration method of choice for Au in many drier parts of the world, particularly southern Australia. Edoldeh Tank is a weakly mineralised Au prospect in calcrete terrain that lies at the eastern edge of the Great Victoria Desert dunefield (South Australia). At Edoldeh Tank a variety of calcretes occur but the dominant form is a laminated calcrete horizon (LCH). The mineralogy of the near-surface soil is relatively simple and consists of calcite, dolomite, quartz, kaolinite and minor smectite; quartz dominates the unconsolidated overlying sandy soil, and carbonate minerals dominate the LCH. We determine the distribution and nature of the Au at a small scale using a variety of techniques, including SEM, LA-ICP-MS and SXRF and dated sediments to understand calcrete genesis. In a series of thirty excavated soil pits, Ca and Au concentrations increased with depth, markedly so at the LCH. We provide multiple lines of evidence to show there is a general association of Au with calcrete but not a strong correlation as seen with soil profiles elsewhere that have younger, recently formed powdery calcrete. Experiments suggest Au and Ag are currently mobile in this environment despite the low rainfall and that Au occurs in two forms: Au (possibly ionic) occurs throughout the sample with some regions having higher concentrations than others; particulate Au occurs randomly but is more common where the general level of Au is higher. The laminated nature of the calcrete suggests it has formed episodically. An association of Ag with Au in calcrete suggests a means to distinguish anomalies that have developed in residual regolith from those that have dispersed into adjacent sediments. Laminated calcrete is just as effective an exploration sample medium as powdery calcrete. Mobilised Ca, Au and Ag in calcrete can extend the lateral extent and distance from the source of the geochemical anomaly thus providing an effective vector to target for sampling. A landscape dispersion model of Au in calcrete is presented, which requires further testing, to assist the mineral explorer in covered terrains.

A late-stage hydrothermal phosphate-bearing montmorillonite argillitization from the tourmaline-bearing pegmatite of Alto dos Quintos Mine, northeast Brazil

AbstractThe Alto dos Quintos Mine, Rio Grande do Norte, northeast region of Brazil, is one of the few mines where a LCT (Li-Cs-Ta-enriched) pegmatite is exploited for the deep blue gemstone called “Paraiba Tourmaline (PT)”. Blue cuprian elbaite, a fault-bound pink montmorillonite bearing some relict apatite and newly-formed Ca-Al-phosphate of the Al-P-sulphate group (APS minerals) also occur in the underground mine. The montmorillonite was studied using extended clay mineralogical tools (XRD, IR spectroscopy, XRF, SEM-EDX, cation exchange capacity (CEC), DTA). The structural formula method for calculation of the smectite formula based on EDX data yielded an extremely Fe-poor montmorillonite: (Ca0.22+)(Al1.7Fe0.0Mg0.4)(Si3.8Al0.2). The charge on the tetrahedral sheets accounts for approximately 30% of the total permanent negative charge. However, based on the more precise Hofmann & Klemen test, tetrahedral charge values of 11% to 13% were calculated. This is indicative of the dominance of montmorillonite rather than beidellite among the smectite minerals, which is independently proved by a pronounced IR band at 630 cm-1. The formation of pink montmorillonite is not directly related to the emplacement of the Li-bearing PT pegmatite. The sheet silicate developed after a considerable hiatus (Mesozoic?), when the Neoproterozoic pegmatites had already undergone different stages of hypogene (cookeite) and supergene (illite, kaolinite) alteration, during which Li was flushed out to a degree that formation conditions of expandable Li-bearing phyllosilicates were no longer favoured. The nature of the pinkish tint is not yet clarified. The montmorillonite formed in a temperature regime close to 250°C, when apatite was transformed into Ca-bearing APS minerals under acidic conditions. Cainozoic volcanic activity and the reactivation of deep-seated fault zones are considered to be responsible for the formation of this pink P-bearing montmorillonitic clay.

Aflatoxin Toxicity Reduction in Feed by Enhanced Binding to Surface-Modified Clay Additives

Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (Kd = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (Kd = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (Kd = 13,800) and carnitine (Kd = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (Kd = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (Kd = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (Kd = 1340) or the untreated montmorillonite (Kd = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity.

Studying the stress-suction coupling in soils using an oedometer equipped with a high capacity tensiometer

In the context of research into deep nuclear waste disposal, various works have concerned the hydromechanical behavior of Boom clay, a stiff plastic clay extracted in the SCK-CEN Underground Research Laboratory near the Mol City (Belgium), at a depth of 223 m. Due to some amount of smectite minerals in the clay fraction, Boom clay exhibits swelling properties when hydrated under low stresses. To investigate some aspects of the hydromechanical behavior of Boom clay, oedometer compression tests were carried out on samples of Boom clay close to saturation and submitted to an initial suction. During oedometer compression, the changes in suction with increased vertical stress are monitored by means of a high capacity tensiometer installed at the bottom of the sample. Some aspects related to hydromechanical couplings are examined through the investigation of the changes in suction during oedometer compression, a somewhat delicate and poorly documented experimental approach. A comparison is also made with a completely different soil sample under suction, i.e. a statically compacted unsaturated low plasticity silt. Some technical difficulties typical of this new experimental approach are first described in detail so as to optimize the interpretation of the data obtained. The experiment allows the determination of the point at which suction is changed to positive pressure during compression. Below this point, the ratio between the vertical stress and the change in suction are determined. Above this point, the data show that positive pore pressures are dissipated in a common way. The suction/stress behavior during unloading is also described and discussed. Finally, an interpretation in terms of microstructure effects is provided for both samples. The experimental approach initiated here seems to provide interesting further application to better understand hydromechanical couplings in natural soils in relation with suction increase during stress release.

Spatial arrangement of soil mantle in Glacis de Buenavista, Mexico as a product and record of landscape evolution

Factors controlling spatial soil organization have recently attracted the attention of soil scientists because they can contribute to regional management of soil resources. We present here a case study in the Glacis de Buenavista (Mexico), an extended volcanic piedmont, in order to develop an integral understanding of its soil cover as a product and, at the same time, as a record of the main stages of landscape evolution. Three phenomena were considered: Luvisol and Vertisol type soils, and pedosediments, all of them analyzed in terms of their development degree (clay content, macro and micromorphology, selective extractions of Fe (Fe d, Fe o), silicon (Si o) and aluminum (Al o), weathering index and clay mineralogy). Luvisols, represented in the Ahuatenco, Mexicapa and Buenavista sections, are located in the northern and central part of the area. They are red-clayey, polygenetic soils that show strong weathering (with high kaolinitic clay content and high weathering index values), clay illuviation, and reductomorphic processes, combined with vertic features in some parts of the profiles. Vertisols dominate the central and southern portion of the Glacis. They exhibit cracking, angular blocks with wedge-like shapes, slickensides and stress-cutans. The pedogenesis of the Vertisol type is clearly associated with the presence of smectitic minerals in the clay fraction as a product of neoformation. Factors controlling this pedodiversity are: relief, which affects bioclimatic differentiation within the studied landsurface and defines the lateral redistribution of moisture and dissolved substances; and time. Luvisols represent a longer pedogenetic phase that started in the Late Pleistocene, according to the age of buried paleosols, while Vertisols mainly originated in the Late Holocene (according to the age of buried organic horizons). Pedosediments are located in the central area of the Glacis. Here, past and present geomorphic processes interact to produce the greatest soil diversity. The recent human-induced erosion partly destroyed polycyclic Luvisols and exposed ancient subsurface pedosedimentary strata. At the same time it produced patches of unconsolidated pedosediments consisting mostly of redeposited Luvisol materials.

Mixed-layer illite–smectite reactivity in acidified solutions: Implications for clayey caprock stability in CO 2 geological storage

The reactivity of mixed-layer illite–smectite was investigated in batch and mixed-flow reactors in the presence of K-bearing mineral impurities (K-feldspar) in order to determine the reaction pathways and the kinetic rate of the reactions in a range of pH conditions pertinent to the context of CO 2 geological storage. The mixed-layered illite–smectite (I–S) mineral was extracted from a natural clayey caprock and was studied at 80 °C, with a solution salinity of 0.1 M NaCl and over a pH range from 3 to 8.5. The experimental results show that the most important process taking place is illitization of the initial I–S. In the most acidic conditions, an intense illitization is observed, which was interpreted as a new proton-promoted illitization process. At neutral pH, illitization is less intense and is attributed to a classical thermal effect. In terms of the overall reaction rate (I/S and K-feldspar dissolution in a mixed flow experiment), the values calculated from the evolution of SiO 2 concentrations fall in the range of the experimental values reported in the literature for smectites and illites. Implications of illitization processes on CO 2 storage and clayey caprock integrity are also discussed.

Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil

Lime and cement are widely used in stabilization and improvement of the expansive subsoils that support pavement infrastructure. In this research, an attempt is made to stabilize a highly expansive soil rich with smectite minerals with an aim to understand the mechanisms that result in soil property improvements. Influences of both the type of stabilizer and their dosages were studied for modifying expansive clay from the north-central region of Saudi Arabia. Al-Qatif soil is known for its highly expansive nature, and it is known to induce major damage to low-volume roads built on untreated to unbound sandy bases. This research was performed by first characterizing and classifying Al-Qatif clayey soil by means of routine index properties, X-ray diffraction studies, and swell and shrinkage tests. Next, lime and cement were used to stabilize control clayey soils, and the treated soils were then subjected to the same soil tests. Effects of lime and cement treatments on Atterberg limits, swell, and linear shrinkage strain properties are addressed. Major conclusions and findings from experimental investigations are presented.

DISTRIBUTION PATTERN AND ASSEMBLAGE FEATURE OF CLAY MINERALS IN SURFACE SEDIMENTS FROM THE COASTAL AREA OF SHANDONG PENINSULA

By analyzing the clay minerals in 200samples of surface sediments from the Coastal area of Shandong Peninsula,the distribution pattern of clay minerals(illite,chlorite,smectite,and kaolinite)was constructed.Results show that illite is the dominant clay mineral(61%),followed by smectite(16%),chlorite(13%),and kaolinite(10%).There are two areas in accordance with clay minerals assemblage.The first one,characterized by illite-smectite-chlorite-kaolinite assemblage and extensively distributed in the north,east and southeast offshore areas,was defined as the area dominated by the Huanghe-derived sediments.The other one located at the southern offshore area and characterized by a clay minerals assemblage of kaolinite-illite-smectite-chlorite or illite-kaolinite-smectite-chlorite,was defined as the area with Peninsula-source sediments dominating.The distribution pattern and assemblage features of clay minerals indicate that the transport and dispersal processes of sediments around the Shandong Peninsula were strongly controlled by the near shore circle currents.

Caracterização dos argilominerais usados em matéria-prima cerâmica, da formação Rio do Rasto, Bacia do Paraná, no município de Turvo, SC

No sudeste de Santa Catarina existem inúmeras minas de exploração de argilas destinadas à indústria cerâmica da região. Para o conhecimento desta matéria prima foi realizada a caracterização em detalhe de uma frente de lavra em atividade. A exploração é realizada em terrenos sedimentares da Formação Rio do Rasto (Permiano Superior) na Bacia do Paraná que afloram como morros testemunho. Foram coletadas quatorze amostras representativas dos níveis desta mina composta de argilitos com intercalação de siltitos de pequena espessura. As amostras foram analisadas por difratometria de raios X pelo método do pó na rocha total e na fração < 4 µm. A composição química foi determinada por fluorescência de raios X. Foram realizadas observações ao microscópio eletrônico de varredura (elétrons secundários) de fragmentos das amostras e microanálises por microssonda eletrônica de lâminas delgadas. Os resultados mostraram uma grande variação vertical da mineralogia, tendo sido identificados três níveis diferentes. Até 2,00 m há predomínio de esmectita. Entre 2,00 m e 5,50 m a esmectita é o principal argilomineral, mas com quantidade significativa de ilita/mica, e acima de 5,50 m há grande aumento do feldspato potássico e mica detrítica. Estudos de detalhe por difratometria de raios X (determinação do parâmetro b) e microanálises WDS por microssonda eletrônica permitiram identificar como montmorilonita a espécie argilomineral do grupo das esmectitas.

Comparative influence of burial depth on the clay mineral assemblage of the Agadir-Essaouira basin (western High Atlas, Morocco)

AbstractIn the western High Atlas basin, the evolution of the clay assemblage of the Upper Jurassic–Cretaceous sedimentary series is controlled by palaeogeographic changes of the basin and by burial diagenesis.The effects of burial are expressed by an increase in the proportions of illite and chlorite with depth, a decrease of expandability of smectite minerals and by a decrease in the Kübler Index.Kaolinite is preserved at greater depths than smectite, but also tends to diminish in abundance. TEM observations show that idiomorphic pseudo-hexagonal crystals of illite increase in size and abundance downwards, especially in the sandy levels.In the Agadir section, the main change in the clay mineral evolution related to late diagenesis occurs at the Mid-Albian, corresponding to a burial depth of about 1800 m; in the Essaouira section it occurs at the Lower Tithonian at a burial depth of about 2100 m.Considering the different geothermal gradient between Agadir (36ºC km–1) and Essaouira (27ºC km–1), the disappearance of smectite occurs at the same temperature in these two sites (60 to 65ºC).

Delamination of smectite in river-borne suspensions at the fluvial/marine interface – An experimental study

Fine fractions (<2 μm) from smectite-rich flood-plain sediments from the Elbe and Weser rivers in Germany were treated in the laboratory with synthetic sea salt solutions at different concentrations and for different periods of time to document sheet delamination of smectite particles at the fluvial/marine interface and thus simulate changes in clay minerals at the mouth of a river. The project consisted of two steps: (1) Pilot tests were made in 0.5% salt solutions (brackish environment) showing a nearly 2-min delay of the clearing of the clayey suspensions, when the suspension was redispersed 15 and 30 min later after the first measurement. This was due to an obviously increased number of fine laminae from disintegrated smectite particles. (2) X-ray diffraction studies (XRD) of the clayey material from suspensions in 0.0, 0.5, 1.0, and 3.0% salt solutions after standing 10 min, and one and three weeks were made to document alteration reactions of smectite. An aliquot was pipetted periodically from each series, and oriented clay-mineral specimens were analyzed by XRD in air-dried, glycol- and glycerin-solvated states. The peak intensities in the XRD patterns of the clay minerals smectite, random-ordered mixed-layer illite/smectite (I–S), kaolinite, chlorite, and illite did not change in the salt-free series during the experiments. In contrast the peak intensities of smectite and I–S mineral in the air-dried and glycerin-solvated states after suspension in saline solutions decreased significantly. The d-values of the smectitic materials in the air-dried state also decreased after contact with the saline solutions, and in the glycerin-solvated state the full-width-at-half-maximum (FWHM) of the 001 smectite reflection increased by about 20%, indicating a reduction in grain size. The variations in FWHM, d-values and peak intensity of the smectitic material are assumed to be caused by an exchange of Na for Ca in the interlayer spaces and subsequent delamination of the particles along the Na-activated interlayers. Only those smectite particles in which adjacent sheets are still stabilized by the remaining Ca are preserved after contact with seawater. The experiments show that delamination of smectite and I–S mixed-layer minerals is likely to occur in the brackish environment at the mouth of a river. However, formation of these fine laminae is expected to be a transitional stage in the development of clay particle size, owing to the formation of flocs and aggregates in the higher salt concentrations of seawater.

Terminal C≡C triple bond hydrogenation using immobilized Wilkinson’s catalyst

In this work, we try to hydrogenate selectively phenylacetylene to styrene and 3-phenylpropyne to allylbenzene using immobilized or pure Wilkinson’s catalyst. The catalyst was immobilized using two approaches—immobilization using ionic exchange and immobilization using covalent bonding. In the first case, the smectite minerals (hectorite and montmorillonite) were used as the supports. In the second case, MCM-41 and SBA-15 were used as the supports. Both types of immobilization were successful and the solid products were characterized. For the covalent bond formation, it was necessary to first modify the surface of the silica material. The modification was carried out using two substances, one adding an amino group to the silica material, and the second adding a phenyl group to the material. The selectivity of hydrogenation of both substances was higher using heterogeneous catalyst in the case of phenylacetylene. In the case of phenylpropyne, no difference in selectivity using Wilkinson’s catalyst in homogeneous or heterogeneous arrangement was observed. The type of immobilization has no influence on either activity or selectivity of catalyst.

FTIR and XRD Investigations of Tetracycline Intercalation in Smectites

AbstractDue to swelling, smectite minerals are capable of intercalating many organic molecules in their interlayer space. Tetracycline (TC) is a group of antibiotics used extensively in human and veterinary medicine. The great aqueous solubility and long environmental half life of TC mean that the study of interactions between swelling clay minerals and TC are of great importance in TC transport and retention in subsurface soils. In the present study, the intercalation of TC molecules at different levels into smectites was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The shift of the FTIR bands of amide I and II in comparison to crystalline TC suggested a strong interaction between the amide groups and the clay surfaces. The band at 1455 cm−1 remained the same after TC intercalation into SAz-1, SWy-2, and SYn-1, suggesting that complexation was not a dominant mechanism of TC uptake by these minerals. With cation exchange as the major mechanism of TC intercalation into these minerals, simultaneous removal of H+ from solution protonated the TC molecules and provided a positive charge to interact with negatively charged mineral surfaces even in neutral to slightly alkaline conditions. The increase in interlayer distance after intercalation by TC, as revealed by XRD, suggested a tilted orientation of the intercalated TC molecules in both twisted conformation in acidic condition and extended conformation in alkaline condition.

Modelling the chemical weathering fluxes at the watershed scale in the Tropics (Mule Hole, South India): Relative contribution of the smectite/kaolinite assemblage versus primary minerals

We investigate the chemical weathering processes and fluxes in a small experimental watershed (SEW) through a modelling approach. The study site is the Mule Hole SEW developed on a gneissic basement located in the climatic gradient of the Western Ghats, South India. The model couples a lumped hydrological model simulating the water budget at the watershed scale to the WITCH model estimating the dissolution/precipitation rates of minerals using laboratory kinetic laws. Forcing functions and parameters of the simulation are defined by the field data. The coupled model is calibrated with stream and groundwater compositions through the testing of a large range of smectite solubility and abundance in the soil horizons. We found that, despite the low abundance of smectite in the dominant soil type of the watershed (4 vol.%), their net dissolution provides 75% of the export of dissolved silica, while primary silicate mineral dissolution releases only 15% of this flux. Overall, smectites (modelled as montmorillonites) are not stable under the present day climatic conditions. Furthermore, the dissolution of trace carbonates in the saprolitic horizon provides 50% of the calcium export at the watershed scale. Modelling results show the contrasted behavior of the two main soil types of the watershed: red soils (88% of the surface) are provider of calcium, while black soils (smectite-rich and characterized by a lower drainage) consumes calcium through overall carbonate precipitation. Our model results stress the key role played by minor/accessory minerals and by the thermodynamic properties of smectite minerals, and by the drainage of the weathering profiles on the weathering budget of a tropical watershed.

Pedogenic chlorites in podzolic soils with different intensities of hydromorphism: Origin, properties, and conditions of their formation

Minerals of the pedogenic chlorite group were studied in the clay fractions isolated from the mineral horizons of podzolic and gleyic peat-podzolic soils. In the AE and E horizons of the podzolic soil, pedogenic chlorites are thought to develop from vermiculite, whereas in the E horizon of the gleyic peat-podzolic soil, they can be formed from smectite minerals. For estimating the degree of chloritization (the degree of filling of the interlayer space of 2: 1 minerals with Al hydroxides), a numerical criterion was is proposed. The difference between the values of this criterion before and after the treatment of the preparations with NH4F indicated that the degree of chloritization in the pedogenic chlorites decreases in the following sequence: the E horizon of the podzolic soil > the AE horizon of the podzolic soil > the E horizon of the gleyic peat-podzolic soil. Another numerical criterion was proposed to estimate the degree of polymerization of Al-hydroxy complexes in pedogenic chlorites. This criterion was based on the thermal stability of soil chlorites and represented the temperature at which an increase in the intensity of the 1.0-nm peak after heating the K-saturated preparations exceeds 50% of its initial value. According to this criterion, the degree of polymerization of the Al-hydroxy interlayers in pedogenic chlorites decreases in the following sequence: the E horizon of the podzolic soil > the E horizon of the gleyic peat-podzolic soil ≥ the AE horizon of the podzolic soil. The distinct interrelation between the soil properties and the degrees of chloritization and polymerization of the Al-hydroxy interlayers attests to the modern origin of the pedogenic chlorites.

Treatment of waters containing uranium with saponite clay

The article has investigated sorption of U(VI) on a smectite mineral—saponite from the Tashkinsk deposit in the Khmelnitsk region. The equilibrium in the U(VI)-saponite system sets in within 8 h. The relationship between sorption and the pH has a clear-cut maximum characteristic of uranium sorption on aluminum-silicates at the pH values 5.5–7. The U(VI) sorption isotherm on saponite is described by the Langmuir empirical equation. We have established the influence on the sorption process of complexation reagents (EDTA, carbonate ions, fulvic acids). Based on experimental data the possibility of using the sorption method with the employment of saponite for water treatment containing uranium is shown.

Synthesis and characterization of low dimensional ZnS- and PbS-semiconductor particles on a montmorillonite template

Low dimensional metal sulfide particles have been prepared in the interlayers of montmorillonites via reactions of the metal ion-exchanged clay minerals in aqueous dispersions with gaseous hydrogen sulfide. The montmorillonites separated from the Wyoming (USA) and Jelšový Potok (Slovakia) bentonites were saturated with Pb(2+) or Zn(2+). In the final nanohybrids, the smectite mineral can be incorporated with metal sulfide pillars and/or nanoparticles. Properties of the prepared materials were investigated by various analytical techniques. The formation of metal sulfide nanoparticles in the interlayer galleries was indicated by X-ray diffraction and energy dispersive X-ray analysis. About 50% of Pb(2+) or Zn(2+) present in montmorillonite has formed metal sulfide semiconducting units. Infrared spectroscopy and thermogravimetric analysis were used for characterization of starting materials and products. Ultraviolet-visible absorption and photoluminescence spectroscopies confirmed that final composite systems acquired the optical properties of the incorporated quantum low dimensional systems exhibiting blue shift of the energy gap and higher oscillator strength excitonic peaks. Larger amounts of metal sulfide nanoparticles were formed in montmorillonite Jelšový Potok probably as a consequence of its higher cation exchange capacity.

Genetic implications of a retransported loess profile near Córdoba, Argentina

Abstract This paper deals with a loess profile located southeast of Cordoba (64° 05′ 30 W to 31°30′ S) that was dated in Beijing University using the OSL method according to Simple Aliquot Regeneration Protocol. This study provides some inferences regarding climatic and environmental features, such as transport agents and probable sources of the materials. The profile, located inside Llanura Pampeana, is approximately 6.80 m in depth and comprises ages between 22.4 ± 3.2 and 9.9 ± 0.3 ka. Throughout the profile, and for all grain sizes, major minerals are quartz and feldspar, with micas, and opaques as subordinates. Illite and chlorite appear as traces, though the last one was not confirmed in the finest fraction analysis. Calcite is abundant in the uppermost sample and decreases downwards. In the base of the profile, and in the clay fraction, XRD showed illite, swellable clay minerals (smectite + mixed layers) and kaolinite traces. It was concluded that the profile would have been derived from the accumulation of sediments, along several events very similar in transport conditions, even though there are some indications that about 21 ka BP, water availability was slightly smaller than for the rest of the profile. This change was also established in some other places, allowing some regional correlations. According to the analyzed data, about 19 ka BP, water availability again increased.

Polish clayey raw materials for the production of ceramic tiles

AbstractDevelopment of the Polish ceramic industry over the last ten years has resulted in a sharp increase in demand for basic raw materials, especially for ceramic clays – both white- and light-firing as well as red-firing varieties. Polish sources of white-firing clays are rather scarce. Their production is based on Santonian sandy-clayey sediments of the North-Sudetic Trough (Lower Silesia, SW Poland). Light-firing varieties occur mainly in Lower Jurassic sediments on the northern margin of the Holy Cross Mountains (central Poland). Red-firing well-sintering clays of Triassic age are known in the northern margin of the Holy Cross Mountains as well as in the Cracow-Silesian Monocline.The white-firing Santonian clays contain mainly highly-ordered kaolinite (~50%) and quartz (~30%) with minor amounts of illite. Their grain-size median ranges between 1.9 and 2.5 μm. They show moderate plasticity (bending strength after drying at 1.7–1.9 MPa) and weak sinterability (water absorption after firing ~12%), but greater lightness after firing (L parameter ~86%). The light-firing Jurassic clays are kaolinitic-illitic in character, with a variable content of quartz. Kaolinite is represented by the low-ordered variety. The grain-size median is also variable, ranging between 1.1 and 3.4 μm. They show good plasticity (bending strength after drying 2.6–2.8 MPa), good or very good sinterability (water absorption after firing &lt;6%) but moderate lightness (L ~79%).Triassic red clays are highly polymineralic, with illite, kaolinite, smectite, chlorite and mixed-layered minerals occurring in variable amounts. Their specific features are: large hematite content (5–12%), commonly small CaO content (&lt;0.5 wt.%) and an extremely small organic matter content (⩽0.1 wt.%). Their grain-size median usually varies between 2 and 3 mm. Using such clays, sintered ceramics (e.g. stoneware tiles) are obtained after firing in the temperature range 1150–1200ºC.