Showing papers on "Clay minerals published in 2012"
TL;DR: In this paper, a series of CH 4 adsorption experiments on clay-rich rocks were conducted at 35, 50, and 65°C and at CH 4 pressure up to 15 MPa under dry conditions.
518 citations
TL;DR: In this paper, the authors reported new data on the petrological, mineralogical, and geochemical compositions of 13 bench samples of the high-Ge No 6 coal from the Wulantuga deposit, and provided new insight into the origin and modes of occurrence of the minerals and elements present.
239 citations
TL;DR: Li et al. as discussed by the authors reported new results on 48 bench samples of the CP2 coal from the adjacent Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, and provided new insights into the origin and modes of occurrence of the minerals and elements present in the coal.
221 citations
TL;DR: Based on observation of the outcrops and cores of the Late Ordovician to the Early Silurian Wufeng-Longmaxi shale, developed in the deep water shelf environment, in the southeast of the Sichuan Basin, the mineralogical features, lithofacies characteristics and reservoir space types were studied and the factors affecting reservoir capacity were analyzed by observation of eletron microscope and analysis of mineral content.
155 citations
TL;DR: In this paper, a set of clay-rich saprolites developed on the Neogene tholeiitic basalt from Hainan Island in southern China have been measured in order to document the behavior of Mg isotopes during continental weathering.
146 citations
TL;DR: A review of the active areas of research on clay-microbe interactions can be found in this article, where the authors provide perspectives for future work and discuss the role of microbes in clay mineral transformations.
Abstract: Clay minerals are ubiquitous in soils, sediments, and sedimentary rocks, and they play important roles in environmental processes. Microbes are also abundant in these geological media, and they interact with clays via a variety of mechanisms, such as reduction and oxidation of structural iron and mineral dissolution and precipitation through the production of siderophores and organic acids. These interactions greatly accelerate clay mineral reaction rates. While it is certain that microbes play important roles in clay mineral transformations, quantitative assessment of these roles is limited. This paper reviews some active areas of research on clay–microbe interactions and provides perspectives for future work.
126 citations
125 citations
TL;DR: One-electron-transfer mediating compounds are used to facilitate electron transfer between structural Fe in clay minerals and a vitreous carbon working electrode in an electrochemical cell to demonstrate reliable quantification of Fe content and redox state.
Abstract: Clay minerals often contain redox-active structural iron that participates in electron transfer reactions with environmental pollutants, bacteria, and biological nutrients. Measuring the redox properties of structural Fe in clay minerals using electrochemical approaches, however, has proven to be difficult due to a lack of reactivity between clay minerals and electrodes. Here, we overcome this limitation by using one-electron-transfer mediating compounds to facilitate electron transfer between structural Fe in clay minerals and a vitreous carbon working electrode in an electrochemical cell. Using this approach, the electron-accepting and -donating capacities (QEAC and QEDC) were quantified at applied potentials (EH) of −0.60 V and +0.61 V (vs SHE), respectively, for four natural Fe-bearing smectites (i.e., SWa-1, SWy-2, NAu-1, and NAu-2) having different total Fe contents (Fetotal = 2.3 to 21.2 wt % Fe) and varied initial Fe2+/Fetotal states. For every SWa-1 and SWy-2 sample, all the structural Fe was red...
123 citations
TL;DR: In this article, the authors investigated radiocesium in the natural sample (soil and sediment) from Fukushima Prefecture was investigated through sequential extraction experiment (modified BCR method), which showed that more than 94% of 137 Cs was fixed in the residual phase.
Abstract: Previous studies have shown that radiocesium (mainly 137 Cs) was retained at the very surface of soils in Fukushima Prefecture. Clay minerals and micas are assumed as the main sorbents for cesium (Cs) in Fukushima, but direct evidence is lacking for this hypothesis. In this study, radiocesium in the natural sample (soil and sediment) from Fukushima Prefecture was investigated through sequential extraction experiment (modified BCR method), which showed that more than 94% of 137 Cs was fixed in the residual phase. The results indicated that most of Cs occurred in the interlayer of phyllosilicate minerals. Furthermore, Cs LIII-edge extended X-ray absorption fine structure (EXAFS) showed that the Cs species adsorbed on the natural samples were very similar to those adsorbed on clay minerals and micas. This finding provided the direct evidence on the significant contribution of clay minerals or micas to Cs retention in soils from Fukushima Prefecture.
TL;DR: In this paper, isotopic variations in bulk soils and clay fractions relative to their parent andesite in three soil weatheringsequences from Guadeloupe formed under contrasting climatic conditions were investigated.
TL;DR: In this paper, the authors studied the time-dependent changes in the structure of lime stabilized montmorillonitic and lateritic clays using solid state nuclear magnetic resonance (SS-NMR) and Fourier transform infrared (FTIR) spectroscopy.
TL;DR: In this article, a comparative study was conducted using standard clays, namely kaolinite KGa-2, smectite SWy-1 and illite IMt-2.
TL;DR: A review of the role of clay minerals in crude oil formation, migration and accumulation can be found in this article, where the authors present a detailed analysis of the chemical interactions and reaction mechanisms between clay minerals and crude oil.
TL;DR: In this paper, an artificial soil incubation experiment was carried out to study the effect of microbial activity and mineral interactions on the aggregation occurring during incubation, and the results of density fractionation indicate that OM was mainly associated with the clay minerals, probably due to the neutral pH of the artificial soils, leading to a low or negative surface charge of the oxides.
TL;DR: In this paper, the capability of mesophilic methanogen, Methanosarcina mazei, in reducing structural Fe(III) in illite-smectite clay minerals and its potential role in inducing mineralogical changes was investigated.
TL;DR: In this article, a study of laboratory-treated Na+-smectite and Pierre Shale and natural thermo-mature gas shale indicate that, large quantities of silica are released during clay mineral transformation to form quartz cement (within a closed shale system).
TL;DR: Bioreduction experiments showed that D. vulgaris could promote smectite illitization through reduction of structural Fe(III) in clay minerals and AQDS enhanced the reduction rate and extent.
Abstract: Clay minerals are ubiquitous in soils, sediments, and sedimentary rocks and could coexist with sulfate-reducing bacteria (SRB) in anoxic environments, however, the interactions of clay minerals and SRB are not well understood. The objective of this study was to understand the reduction rate and capacity of structural Fe(III) in dioctahedral clay minerals by a mesophilic SRB, Desulfovibrio vulgaris and the potential role in catalyzing smectite illitization. Bioreduction experiments were performed in batch systems, where four different clay minerals (nontronite NAu-2, mixed-layer illite-smectite RAr-1 and ISCz-1, and illite IMt-1) were exposed to D. vulgaris in a non-growth medium with and without anthraquinone-2,6-disulfonate (AQDS) and sulfate. Our results demonstrated that D. vulgaris was able to reduce structural Fe(III) in these clay minerals, and AQDS enhanced the reduction rate and extent. In the presence of AQDS, sulfate had little effect on Fe(III) bioreduction. In the absence of AQDS, sulfate increased the reduction rate and capacity, suggesting that sulfide produced during sulfate reduction reacted with the phyllosilicate Fe(III). The extent of bioreduction of structural Fe(III) in the clay minerals was positively correlated with the percentage of smectite and mineral surface area of these minerals. X-ray diffraction, and scanning and transmission electron microscopy results confirmed formation of illite after bioreduction. These data collectively showed that D. vulgaris could promote smectite illitization through reduction of structural Fe(III) in clay minerals.
TL;DR: In this article, chemical and physical properties of natural and organically modified clay minerals to understand the nanometre-scale structure, surface characteristics, and application in functional materials are discussed.
Abstract: Clay minerals find a wide range of application in composites, paints, drilling liquids, cosmetics, and medicine. This article reviews chemical and physical properties of natural and organically modified clay minerals to understand the nanometre-scale structure, surface characteristics, and application in functional materials. The relation between fundamental properties and materials design is emphasized and illustrated by examples. The discussion comprises the following: an overview; surface structure and cation density; solubility and solubility reversal by surface modification; the degree of covalent and ionic bonding represented by atomic charges; the distribution of metal substitution sites; measurements and simulations of interfacial properties at the nanometre scale; self-assembly, packing density, and orientation of alkylammonium surfactants on the clay mineral surface; the density and chain conformation of surfactants in organic interlayer spaces; the free energy of exfoliation in polymer matrices and modifications by tuning the cleavage energy; thermal transitions, diffusion, and optical responses of surfactants on the mineral surface; elastic moduli and bending stability of clay layers; and the adsorption mechanism of peptides onto clay mineral surfaces in aqueous solution. Potential applications in biotechnology and other future uses are described.
TL;DR: In this paper, the adsorption behaviors of fulvic acid (FA) and humic acid (HA) on kaolinite, smectite and vermiculite were investigated.
TL;DR: In this paper, the authors used various techniques, including X-ray diffraction, Xray fluorescence, and thin-section analysis, and found that most of the clay minerals were derived from weathering of rock.
Abstract: The Dumre Besi landslide is one of the largest and most problematic failures on the Mugling–Narayanghat Highway in central Nepal. Though it was triggered by the monsoon rain of 2003, geological structures and rock weathering have played a key role in its initiation and further aggravation. The slide is also controlled to some extent by the groundwater and rugged topography with high slope angles. The landslide zone comprises thinly laminated light grey siltstone with numerous crosscutting quartz veins, grey metasandstone (quartzite), bluish grey to white phyllite, black carbonaceous slate, and dolomite. A thrust fault passes through the centre of the landslide, creating a thick deposit of loose, weathered rock material, and the fault has developed a very thick shattered zone where weathering is very intense. Using field and laboratory analyses, the rocks in the landslide zone can be divided into five zones based on the severity of weathering: none, slight, moderate, severe, and complete. Laboratory analyses showed that the chemically weathered rocks are significantly rich in smectite and vermiculite. Out of these, smectite is the most critical one, as it swells when wet. The formation mechanism of the clay minerals was analysed by various techniques, including X-ray diffraction, X-ray fluorescence, and thin-section analysis, and it was found that most of them were derived from weathering of rock. The clay minerals significantly reduced the rock strength and facilitated the extensive failure of Dumre Besi. The wide fault zone with deeply weathered and clay-rich debris is also responsible for the formation of debris flows in the monsoon season.
TL;DR: In this article, the authors used a CSIRO Hy-Logging™ system from 180 reverse circulation and 14 diamond drill cores spanning a depth from surface to 55 m below surface, intersecting the Rocklea deposit.
Abstract: Visible-near to shortwave infrared reflectance spectra (VNIR-SWIR—400–2,500 nm wavelength region) provide quantitative measurements of mineral abundances and mineral physicochemistries from drill core samples of channel iron ore. The infrared spectral reflectance measurements of drill core samples from the Rocklea channel iron deposit, located in the Hamersley Basin of Western Australia, were validated against X-ray flouresence (XRF) and X-ray diffraction (XRD). The reflectance data were collected using a CSIRO Hy-Logging™ system from 180 reverse circulation and 14 diamond drill cores spanning a depth from surface to 55 m below surface, intersecting the Rocklea deposit. The mineralogy of this channel iron deposit comprises chiefly goethite (both vitreous and ochreous forms) with lesser amounts of hematite and variable amounts of quartz, kaolinite, smectite (both dioctahedral and trioctahedral varieties), and carbonate (both dolomite and calcite). Iron ore and waste rock mineralogy were extracted from the infrared spectroscopic reflectance data using the geometry (depth/wavelength) of continuum-removed reflectance spectra, with depths of absorption features proportional to mineral abundance and wavelength positions proportional to chemical composition. For any one mineral, a number of its diagnostic spectral features are used to determine its mineral abundance and composition, in order to avoid complications with minerals that spectrally overlap with part of the diagnostic spectral features of the mineral of interest. This method that combines multiple spectral features to identify and quantify minerals is transferable to all types of infrared reflectance spectroscopic data collected from drill core to satellites. Final products include: iron (oxyhydr-)oxide content (root mean square error (RMSE) 9.1 wt % Fe); Al clay content (RMSE 3.9 wt % Al 2 O 3 ); hematite/goethite ratio (RMSE 9.0 wt % goethite); vitreous versus ochreous goethite (not easily measured using other analytical techniques); clay mineral type (kaolinite, montmorillonite and nontronite); and carbonate composition (dolomite vs. calcite). The Rocklea infrared reflectance spectroscopy-based mineral abundance and composition results have been used in an associated study to characterize the architecture of the Rocklea channel iron deposit, with implications for exploration, mining, and ore genesis.
TL;DR: In this paper, a revised pedotransfer function (PTF) was proposed to predict water sorption isotherms for dry soils based on the clay content of the soils.
TL;DR: In this article, the authors present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low-angle normal faults in the American Cordillera to demonstrate the range and type of clay transformations in natural fault gouges.
TL;DR: In this paper, the authors employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and flood plains since 14.5 years, spanning a period of strong climatic change.
TL;DR: The most efficient method comprised a high phosphate solution introduced at the cell-lysing step in DNA extraction, to promote chemical competition with DNA for adsorption sites, and proved suitable for the recovery of low molecular weight DNA (< 1.5 kb).
12 Sep 2012
TL;DR: In this article, the authors investigate how Si depletion in soils and associated clay mineralogy influence the Si isotope fractionation associated with clay mineral formation and provide new insights to better define Si isotopes as a proxy for environmental conditions for clay formation.
TL;DR: Analysis of experimental data and simulation results suggest that structurally incorporated Zn preferentially substitutes for Al(III) in the trans-symmetric sites of the octahedral layer of montmorillonite, a dioctahedral clay.
Abstract: Clay minerals are efficient sinks for heavy metals in the geosphere. Knowing the uptake mechanism of these elements on clays can help to protect the natural environment from industrial pollution. In this study ab initio molecular dynamics (MD) calculations were applied to simulate the uptake of Zn on the edge surfaces of montmorillonite, a dioctahedral clay, and to explain the measured K-edge extended X-ray absorption fine structure (EXAFS) spectra of adsorbed Zn. These experiments were carried out using a high ionic strength Na background electrolyte that enables one to block cation exchange processes and to restrict the Zn uptake to the sorption complexation at the edge sites of clay. The analysis of the experimental data and simulation results suggest that structurally incorporated Zn preferentially substitutes for Al(III) in the trans-symmetric sites of the octahedral layer. At low loading, Zn is incorporated into the outermost trans-octahedra on (010) and (110) edges. At medium loading, Zn forms mono...