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1

Clay Mineral: Radiological Characterization  

NASA Astrophysics Data System (ADS)

Since the early days, clays have been used for therapeutic purposes. Nowadays, most minerals applied as anti-inflammatory, pharmaceutics and cosmetic are the clay minerals that are used as the active ingredient or, as the excipient, in formulations. Although their large use, few information is available in literature on the content of the radionuclide concentrations of uranium and thorium natural series and 40K in these clay minerals. The objective of this work is to determine the concentrations of 238U, 232Th, 226Ra, 228Ra, 210Pb and 40K in commercial samples of clay minerals used for pharmaceutical or cosmetic purposes. Two kinds of clays samples were obtained in pharmacies, named green clay and white clay. Measurement for the determination of 238U and 232Th activity concentration was made by alpha spectrometry and gamma spectrometry was used for 226Ra, 228Ra, 210Pb and 40K determination. Some physical-chemical parameters were also determined as organic carbon and pH. The average activity concentration obtained was 906+/-340 Bq kg-1 for 40K, 40+/-9 Bq kg-1 for 226Ra, 75+/-9 Bq kg-1 for 228Ra, 197+/-38 Bq kg-1 for 210Pb, 51+/-26 Bq kg-1 for 238U and 55+/-24 Bq kg-1 for 232Th, considering both kinds of clay.

Cotomácio, J. G.; Silva, P. S. C.; Mazzilli, B. P.

2008-08-01

2

Clay minerals in animal nutrition  

Microsoft Academic Search

Clay minerals are important in many facets of our society. Their properties such as structure and chemical composition, type of exchangeable ion and particle size determine their various uses. The healing powers of clay were known for centuries and are now being rediscovered. The practice of eating clay by animals in the wild for the detoxification of the body and

R. Slamova; M. Trckova; H. Vondruskova; Z. Zraly; I. Pavlik

2011-01-01

3

Clay mineralogy of weathering rinds and possible implications concerning the sources of clay minerals in soils.  

USGS Publications Warehouse

Weathering rinds on volcanic clasts in Quaternary deposits in the western US contain only very fine-grained and poorly crystalline clay minerals. Rinds were sampled from soils containing well-developed argillic B horizons in deposits approx 105 yr old or more. The clay-size fraction of the rinds is dominated by allophane and iron hydroxy-oxides, whereas the B horizons contain abundant well-crystallized clay minerals. The contrast between the clay mineralogy of the weathering rinds, in which weathering is isolated from other soil processes, and that of the associated soil matrices suggests a need to reassess assumptions concerning the rates at which clay minerals form and the sources of clay minerals in argillic B horizons. It seems that crystalline clay minerals form more slowly in weathering rinds than is generally assumed for soil environments and that the weathering of primary minerals may not be the dominant source of crystalline clay minerals in Middle to Late Pleistocene soil.-A.P.

Colman, S. M.

1982-01-01

4

Scanning electron microscopy of clays and clay minerals  

USGS Publications Warehouse

The scanning electron microscope (SEM) proves to be ideally suited for studying the configuration, texture, and fabric of clay samples. Growth mechanics of crystalline units-interpenetration and interlocking of crystallites, crystal habits, twinning, helical growth, and topotaxis-also are uniquely revealed by the SEM. Authigenic kaolins make up the bulk of the examples because their larger crystallite size, better crystallinity, and open texture make them more suited to examination by the SEM than most other clay mineral types. ?? 1971.

Bohor, B. F.; Hughes, R. E.

1971-01-01

5

Clay Minerals are controlled by the environment - Clay Minerals control the environment  

NASA Astrophysics Data System (ADS)

Where clay minerals are analyzed in soils, often there is some confusion, because in the widespread loess-affected and moraine landscapes of Europe quite a variety of clay minerals is found. The sources of these minerals are inherited from the local solid rock, transported through different processes, transformed through mineral changes and inherited from paleo-environments. Very often a miserable assemblage in the clay fraction is found with mica clay, smectite, kaolinite, chlorite and also some quartz. In order to understand the current dynamic of clay mineral formation, very detailed and quantitative analysis in comparison of horizons and landscape are necessary. It is much easier to through light on the development, if conditions are looked for where a single specific mineral can be formed like short range order minerals from volcanic ashes or smectites from basaltic parent material. Old leaching land surfaces will form kaolinitic and in tropical areas gibbsitic clay fractions. In arid environments of deserts and desert fringes, palygorskite and sepiolite can dominate. In general, clay minerals buffer the environment. This is mainly due to the extraordinary large interfaces between mineral surface and pore systems. In the last years mainly the processes of buffering through charging soil solution and of buffering through mineral organic compounds have been analyzed. Development of new microscopic and spectromethods have brought great progress in understanding the role of clays in soil environments.

Stahr, K.; Zarei, M.

2012-04-01

6

Role of clay minerals in UK coal combustion  

Microsoft Academic Search

Clay minerals are the dominant minerals in coals delivered to UK power stations and are therefore major ash contributors. Clay content carries an economic penalty in loss of calorific value of the coal and in costs associated with coal and ash handling and ash disposal, but clays also play a more direct role. A geographic distribution of clay minerals in

D. A Spears

2000-01-01

7

Radiation-induced defects in clay minerals: A review  

NASA Astrophysics Data System (ADS)

Extensive information has been collected on radiation effects on clay minerals over the last 35 years, providing a wealth of information on environmental and geological processes. The fields of applications include the reconstruction of past radioelement migrations, the dating of clay minerals or the evolution of the physico-chemical properties under irradiation. The investigation of several clay minerals, namely kaolinite, dickite, montmorillonite, illite and sudoite, by Electron Paramagnetic Resonance Spectroscopy has shown the presence of defects produced by natural or artificial radiations. These defects consist mostly of electron holes located on oxygen atoms of the structure. The various radiation-induced defects are differentiated through their nature and their thermal stability. Most of them are associated with a ? orbital on a Si-O bond. The most abundant defect in clay minerals is oriented perpendicular to the silicate layer. Thermal annealing indicates this defect in kaolinite (A-center) to be stable over geological periods at ambient temperature. Besides, electron or heavy ion irradiation easily leads to an amorphization in smectites, depending on the type of interlayer cation. The amorphization dose exhibits a bell-shaped variation as a function of temperature, with a decreasing part that indicates the influence of thermal dehydroxylation. Two main applications of the knowledge of radiation-induced defects in clay minerals are derived: (i) The use of defects as tracers of past radioactivity. In geological systems where the age of the clay can be constrained, ancient migrations of radioelements can be reconstructed in natural analogues of high level nuclear waste repositories. When the dose rate may be assumed constant over time, the paleodose is used to date clay populations, an approach applied to fault gouges or laterites of the Amazon basin. (ii) The influence of irradiation over physico-chemical properties of clay minerals. An environmental application concerns the performance assessment of the engineered barrier of nuclear waste disposals. In case of a leakage of transuranic elements from the radioactive waste form, alpha recoil nuclei can amorphize smectite after periods of the order of 1000 years according to a worst case scenario, whereas amorphization from ionizing radiation is unlikely. As amorphization greatly enhances the dissolution kinetics of smectite, the sensitivity of the smectites must be taken into account in the prediction of the long term behavior of engineered barriers.

Allard, Th.; Balan, E.; Calas, G.; Fourdrin, C.; Morichon, E.; Sorieul, S.

2012-04-01

8

Sorption Energy Maps of Clay Mineral Surfaces  

SciTech Connect

A molecular-level understanding of mineral-water interactions is critical for the evaluation and prediction of the sorption properties of clay minerals that may be used in various chemical and radioactive waste disposal methods. Molecular models of metal sorption incorporate empirical energy force fields, based on molecular orbital calculations and spectroscopic data, that account for Coulombic, van der Waals attractive, and short-range repulsive energies. The summation of the non-bonded energy terms at equally-spaced grid points surrounding a mineral substrate provides a three dimensional potential energy grid. The energy map can be used to determine the optimal sorption sites of metal ions on the exposed surfaces of the mineral. By using this approach, we have evaluated the crystallographic and compositional control of metal sorption on the surfaces of kaolinite and illite. Estimates of the relative sorption energy and most stable sorption sites are derived based on a rigid ion approximation.

Cygan, Randall T.; Kirkpatrick, R. James

1999-07-19

9

Clay Mineral Formation and Transformation in Rocks and Soils  

Microsoft Academic Search

Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for the origin of clay minerals in nature. Several of these possibilities are discussed in terms of the rock cycle. The mineralogy of clays neoformed in the weathering environment is a function of solution chemistry, with the most

D. D. Eberl; V. C. Farmer; R. M. Barrer

1984-01-01

10

Diagenetic clays as pore-lining minerals in coalbed methane reservoirs  

SciTech Connect

Cleat surfaces from Mary Lee and Black Creek coal seams in the Black Warrior Basin and Fruitland coal from the San Juan Basin show significant amounts of diagenetic quartz, illite, kaolinite, carbonate minerals, barite, gypsum and iron sulfides and sulfates. SEM, XRD, thin section and reflected light microscopy analyses were used to identify and describe diagenetic minerals and surface textures observed along permeable cleat surfaces. SEM-EDS analysis reveals a variety of pore-lining diagenetic minerals with complex crystal morphologies in permeable cleats of preserved core and mine samples. Surface textures were varied from smooth and vitreous, dull and pitted, to rough and irregular with imbedded diagenetic minerals, often clays or sulfides. Illite is the most abundant clay and occurs as surface coatings, aggregates, authigenic crystals embedded in the coal surface, or oriented subparallel to the fracture face. Kaolinite is also abundant and occurs as abraded platelets and loosely attached aggregates packed against steps, as meniscus shapes on smooth fracture faces, and as a thick crust of anhedral crystals. Chlorite, the least abundant clay, appears as sheets of small crystals. Locally abundant sulfate, sulfide and carbonate minerals are present in masses of euhedral crystals or concentrated as thick crusts. Surface irregularities sometimes control the distribution of diagenetic minerals. Coal fines of unambiguous internal origin and masses of clays are often concentrated at surface irregularities such as steps, laminations of interbedded clays, or sulfides and coal and rough areas of fractures. Their distribution suggests mobility within fractures.

Fowler, K.S.; Nick, K.E. (STIM-LAB, Inc., Duncan, OK (United States))

1996-01-01

11

Prolonged triboluminescence in clays and other minerals  

NASA Technical Reports Server (NTRS)

Samples of various clays and minerals were ground or fractured and monitored with a liquid scintillation spectrometer in order to obtain triboluminescent decay curves. Kaolinite samples displayed several million counts/min after grinding, with a surface area emission estimated at tens of billions of photons/sq cm of surface. The photon production rates varied with the origin of the sample, and kaolinite continually yielded higher production rates than bentonite. The addition of water to the samples slightly increased the count rate of emitted light, while the addition of the fluorescent molecule substance tryptofan significantly enhanced the count rate. Freezing smears of kaolinite and montmorillonite in liquid nitrogen and in a salt ice mixture also induced triboluminescence in the montmorillonite. A possible connection between powdery triboluminescent materials formed in mining industries and respiratory disorders among miners is suggested.

Lahav, N.; Coyne, L. M.; Lawless, J. G.

1982-01-01

12

Geochemistry of clay minerals for uranium exploration in the Grants mineral belt, New Mexico  

Microsoft Academic Search

Clay mineralogy studies of ore rocks versus barren rocks in the Grants mineral belt, New Mexico, show that some combination of chlorite (rosette form), illite, mixed-layer illite-montmorillonite, (±Mg-montmorillonite) are penecontemporaneous with uranium minerals in trend ore; these same clay minerals plus kaolinite are related to the roll-type ore near the main redox front of the Grants mineral belt. Clay minerals

D. G. Brookins

1982-01-01

13

Clay minerals of sediments in the Yatsushiro bay  

Microsoft Academic Search

Since three decades ago it has been established by numerous investigators,, that the general Process of formation of clay minerals is different between the marine and terrestrial conditions, and that the clays of the marine origin are, in general, of illitic type, whereas those of the terrestrial are of kaolin group. In previous communications,, it was reported that clay fractions

Shigenori Aomine; Toshio Higashi

1955-01-01

14

[Mechanism of tritium persistence in porous media like clay minerals].  

PubMed

To investigate the mechanisms of tritium persistence in clay minerals, three types of clay soils (montmorillonite, kaolinite and illite) and tritiated water were used in this study to conduct the tritium sorption tests and the other related tests. Firstly, the ingredients, metal elements and heat properties of clay minerals were studied with some instrumental analysis methods, such as ICP and TG. Secondly, with a specially designed fractionation and condensation experiment, the adsorbed water, the interlayer water and the structural water in the clay minerals separated from the tritium sorption tests were fractionated for investigating the tritium distributions in the different types of adsorptive waters. Thirdly, the location and configuration of tritium adsorbed into the structure of clay minerals were studied with infrared spectrometry (IR) tests. And finally, the forces and mechanisms for driving tritium into the clay minerals were analyzed on the basis of the isotope effect of tritium and the above tests. Following conclusions have been reached: (1) The main reason for tritium persistence in clay minerals is the entrance of tritium into the adsorbed water, the interlayer water and the structural water in clay minerals. The percentage of tritium distributed in these three types of adsorptive water are in the range of 13.65% - 38.71%, 0.32% - 5.96%, 1.28% - 4.37% of the total tritium used in the corresponding test, respectively. The percentages are different for different types of clay minerals. (2) Tritium adsorbed onto clay minerals are existed in the forms of the tritiated hydroxyl radical (OT) and the tritiated water molecule (HTO). Tritium mainly exists in tritiated water molecule for adsorbed water and interlayer water, and in tritiated hydroxyl radical for structural water. (3) The forces and effects driving tritium into the clay minerals may include molecular dispersion, electric charge sorption, isotope exchange and tritium isotope effect. PMID:21634173

Wu, Dong-Jie; Wang, Jin-Sheng; Teng, Yan-Guo; Zhang, Ke-Ni

2011-03-01

15

Microbe-Clay Mineral Reactions and Characterization Techniques  

NASA Astrophysics Data System (ADS)

Clays and clay minerals are ubiquitous in soils, sediments, and sedimentary rocks. They play an important role in environmental processes such as nutrient cycling, plant growth, contaminant migration, organic matter maturation, and petroleum production. The changes in the oxidation state of the structural iron in clay minerals, in part, control their physical and chemical properties in natural environments, such as clay particle flocculation, dispersion, swelling, hydraulic conductivity, surface area, cation and anion exchange capacity, and reactivity towards organic and inorganic contaminants. The structural ferric iron [Fe(III)] in clay minerals can be reduced either chemically or biologically. Many different chemical reductants have been tried, but the most commonly used agent is dithionite. Biological reductants are bacteria, including dissimilatory iron reducing prokaryotes (DIRP) and sulfate-reducing bacteria (SRB). A wide variety of DIRP have been used to reduce ferric iron in clay minerals, including mesophilic, thermophilic, and hyperthermophilic prokaryotes. Multiple clay minerals have been used for microbial reduction studies, including smectite, nontronite (iron-rich smectite variety), illite, illite/smectite, chlorite, and their various mixtures. All these clay minerals are reducible by microorganisms under various conditions with smectite (nontronite) being the most reducible. The reduction extent and rate of ferric iron in clay minerals are measured by wet chemistry, and the reduced clay mineral products are typically characterized with chemical methods, X-ray diffraction, scanning and transmission electron microscopy, Mössbauer spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), UV-vis spectroscopy, and synchrotron-based techniques (such as EXAFS). Microbially reduced smectites (nontronites) have been found to be reactive in reducing a variety of organic and inorganic contaminants. Degradable organic contaminants include pesticides, solvents, explosives, and nitroaromatic and polychlorinated compounds. Inorganic contaminants include Cr(VI), U(VI), and Tc(VII). Despite significant efforts, our understanding of mechanisms of chemical and microbial reduction of ferric iron in clay minerals is still limited. While some studies have presented evidence for a solid-state reduction mechanism, others argue that the clay mineral structure dissolves when the extent of reduction is higher (greater than 30 percent). The electron transfer process is also dependent on the reducing agent. While chemical reduction of ferric iron appears to occur at the basal surfaces, bacteria appear to attack clay minerals at the edges.

Dong, H.; Zhang, G.; Ji, S.; Jaisi, D.; Kim, J.

2008-12-01

16

WEATHERING OF IRONBEARING MINERALS IN SOILS AND SAPROLITE ON THE NORTH CAROLINA BLUE RIDGE FRONT: II. CLAY MINERALOGY  

Microsoft Academic Search

The mineralogy of the clay fraction was studied for soils and saprolite on two Blue Ridge Front mountain slopes. The clay fraction contained the weathering products of primary minerals in the mica gneiss and schist parent rocks. Gibbsite is most abundant in the saprolite and residual soil horizons, where only chemical weathering has been operable. In colluvial soil horizons, where

D. D. AMARASIRIWARDENA; S. W. BUOL

17

Flouride Content of Clay Minerals and Argillaceous Earth Materials  

Microsoft Academic Search

A reliable method, utilizing a fluoride ion-selective electrode, is described for the determina- tion of fluoride in clays and shales. Interference by aluminum and iron is minimal. The reproducibility of the method is about ___5~0 at different levels of fluoride concentration. Data are presented for various clay minerals and for the <2-\\/~m fractions of marine and nonmarine clays and shales.

Josephus Thomas; H. D. GLASS; W. A. WHITE; R. M. TRANDEL

1977-01-01

18

Amino acid adsorption by clay minerals in distilled water  

NASA Astrophysics Data System (ADS)

The adsorption of 15 protein amino acids from dilute (~ 10 ?M) distilled water solutions onto organic-free kaolinite and montmorillonite clay minerals (1 wt% suspensions) was determined at room temperature over a 48 hour period. The systems came to steady state within 2 hours. Basic (positively charged) amino acids were strongly adsorbed (40-80% removal) by both clay minerals. Neutral (uncharged) amino acids were taken up appreciably (10-15%) by montmorillonite, but little if any (<5%) by kaolinite. Acidic (negatively charged) amino acids were adsorbed (20-35%) only by kaolinite. These adsorption patterns appear to be related in part to electrostatic interactions between the clay mineral surfaces and the different amino acid types. The measured extents and selectivities of adsorption onto these clay minerals are sufficiently great to potentially affect the distributions and reactions of free amino acids in natural environments.

Hedges, John I.; Hare, P. E.

1987-02-01

19

Clay Minerals in Mixtures: Sample Preparation, Analysis, and Statistical Interpretation  

Microsoft Academic Search

A method of clay mineral sample preparation for electron microprobe analysis has been devel- oped in which a film of clay plus 10-12 wt. % colloidal graphite is deposited on a porous ceramic disc using a specially designed suction device. Correction procedures are used to obtain quantitative elemental anal- yses representing the average chemical composition of the prepared sample. A

C. M. Gold; P. A. CAVELL; D. G. W. SMITH

1983-01-01

20

Imprints of post-glacial climates and palaeogeography in the detrital clay mineral assemblages of an Upper Permian fluviolacustrine Gondwana deposit from northern Malawi  

Microsoft Academic Search

Detailed quantitative clay mineral studies on an Upper Permian fluviolacustrine Gondwana deposit (?55°S) from northern Malawi (9°S, 32°E) in central-southern Africa show imprints of Late Permian climates on the clay mineral assemblages. The clay mineral assemblage in the bottom 75 m is characterised by abundant illite, chlorite, regular smectite-chlorite (corrensite), regular illite-smectite, and vermiculite (Zone I). Between 75–240 m, illite

Keddy Yemane; Gunther Kahr; Kerry Kelts

1996-01-01

21

Geochemistry of clay minerals for uranium exploration in the Grants mineral belt, New Mexico  

NASA Astrophysics Data System (ADS)

Clay mineralogy studies of ore rocks versus barren rocks in the Grants mineral belt, New Mexico, show that some combination of chlorite (rosette form), illite, mixed-layer illite-montmorillonite, (±Mg-montmorillonite) are penecontemporaneous with uranium minerals in trend ore; these same clay minerals plus kaolinite are related to the roll-type ore near the main redox front of the Grants mineral belt. Clay minerals from barren rocks are characterized by a greater abundance of Na-montmorillonite, kaolinite, and face-to-edge form chlorite. Chlorites from ore zones contain much more vanadium than do chlorites from barren rocks. Trend orr probably formed from southeasterly flowing waters following paleochannels in the Late Jurassic. These deposits are found almost entirely in reduced rocks, and organic carbon may have been an important reductant to remove U-V-U-V-Se-Mo from solution as carbonate from ore zones contains some organic carbon based on stable isotope studies. Uplift, remobilization, and reprecipitation of some of the trend ore resulted in the formation of redistributed ore, some of which possesses a roll-type geometry. Mineralization for the roll-type ore was apparently controlled by sulfide-sulfate equilibria at or near the main redox front in the Grants mineral belt. Trend and roll-type ore possess different assemblages of clay minerals and different trace element abundances. Laramide-age faults cut both trend ore and some roll-type ores. Stack ore is found in Laramide-age fault zones. Limited oxygen isotopic data from clay minerals collected from two mines at Ambrosia Lake in reduced rocks indicate probable preservation of ancient, formational waters and show no evidence of infiltration by young meteoric waters. This information, plus the pre-Laramide-age faults, suggest, but do not unequivocally prove, that the main redox front has been relatively stable since its formation, probably some time in the Cretaceous. Younger encroachment of the redox front in post-Laramide time is proposed by others, however, and the problem is unresolved. Uranium for the deposits was most likely carried in solution as an oxyion, probably as (UO2(CO3)2·2H2O2- or (UO2(HPO4)2)2-, although organic transport cannot be entirely ruled out. Oxyions of vanadium, selenium, molybdenum and possible arsenic and antimony, are interpreted from Eh-pH diagrams to have been segregated and transported with U6+ soluble species and precipitated when a chemically reducing environment was reached. The rare-earth elements are also enriched in ore zones, but is it not clear if they were transported with the U-V-Se-Mo-(As)-(Sb) suite or derived from a more local source.

Brookins, D. G.

1982-03-01

22

Clay Mineral Assemblages as Proxies for Reconstructing Messinian Paleoenvironments in the Western Mediterranean  

NASA Astrophysics Data System (ADS)

Significant tectonic and climate changes at time of the Messinian Salinity Crisis (MSC) led to a complex sedimentation involving marked changes in sediment composition, particularly in clay mineral assemblages. One of the noticeable mineralogical changes across this time interval is the strong smectite increase in Messinian deposits in comparison to the underlying Tortonian and overlaying Pliocene sediments. As no break in the clay mineralogy is recognized in the open ocean (Chamley et al., 1978), such changes are also distinctive of the Mediterranean basins. Since the early discoveries of the giant Messinian evaporite formation (DSDP Legs 13 and 42A), a vast literature contributed, during the last decades, to the continuous debate and re-examination of the actual Messinian paleoenvironment. Drilled records in the westernmost Mediterranean (Alboran Sea) have shown significant changes in the mineralogical assemblages associated to the Messinian events. This basin is depleted of significant salt deposits. Site 976 (ODP Leg 161) recovered a 670-m-thick, middle Miocene (Serravallian) to Pleistocene/Holocene sedimentary sequence, including a thin interval of Messinian sediment, lying directly upon the metamorphic basement. Analysis of clay mineral assemblages from the sedimentary cover of Hole 976B revealed an homogeneous clay association composed of illite, smectite, chlorite and kaolinite with no major changes in clay mineral abundances except for the sediment interval dated as Messinian, which is characterized by a sharp smectite increase (Martinez-Ruiz et al., 1999). Transmission Electron Microscope analyses of clay minerals revealed that smectite composition corresponds to Al-rich beidellites, which supports the existence of such smectites in peri-Mediterranean soils. Smectite formation was favored by the climate conditions at that time, comprising progressive aridification and the alternation of wet and dry climatic episodes. Diagenesis in these smectites is negligible, further evidencing a detrital origin. However, a closer look at clay mineral associations provides an alternate understanding of clay mineral origin, including the possibility of smectite authigenesis in a Mg-rich paleoenvironment. Furthermore, fibrous clays could have originated in such environments. Relationships between Mg-rich clays and carbonates in Messinian sediments should be a next step to explore further constraints on depositional conditions. Chamley, H., Dunoyer-de-Segonzac, G., & Melieres, F. (1978). Clay minerals in Messinian sediments of the Mediterranean Sea. Initial Reports of the Deep Sea Drilling Project, Vol. 42, Part 1, pp. 389-395. Martinez-Ruiz, F., Comas, M. C., & Alonso, B. (1999). Mineral associations and geochemical indicators in Upper Miocene to Pleistocene sediments in the Alboran Basin. In: Proceedings of the Ocean Drilling Program, Scientific Reports, Vol. 161, pp. 21-37.

Martinez-Ruiz, Francisca; Comas, Menchu; Vasconcelos, Crisogono

2014-05-01

23

Immersion Freezing of Clay Minerals and its Temperature Dependence  

NASA Astrophysics Data System (ADS)

The immersion mode ice nucleation efficiency of clay minerals was investigated using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Both monodisperse and polydisperse populations of various clay dust samples as well as hematite and Snomax were examined in the temperature range between -4 ?C and -35 ?C. We observed the immersion mode ice nucleation activity of clay minerals to be strongly depended on the temperature. The time dependence of ice formation inferred by the INAS (Ice Nucleation Active Surface-Site) density is investigated and discussed as a function of cooling rates and by comparing to predicted nucleation rates (i.e., classical nucleation theory with ?-probability density function nucleation scheme). Ice residuals collected through a newly developed pumped counterflow virtual impactor have also been examined by electron microscope analyses to seek the chemical and physical identity of ice nuclei in clay minerals. Brief comparisons of AIDA measurement to the measurements with mobile ice nucleation counters are also presented.

Hiranuma, Naruki; Möhler, Ottmar; Bingemer, Heinz; Bundke, Ulrich; Cziczo, Daniel; Danielczok, Anja; Ebert, Martin; Garimella, Sarvesh; Hoffmann, Nadine; Höhler, Kristina; Kanji, Zamin; Kiselev, Alexei; Raddatz, Michael; Stetzer, Olaf

2013-04-01

24

Environmental applications of radiation-induced defects in clay minerals  

NASA Astrophysics Data System (ADS)

Radiation effects on clay minerals have been studied over the last 35 years, providing a wealth of information on environmental and geological processes. They have been applied to the reconstruction of past radioelement migrations in the geosphere, the dating of clay minerals from soils or the evolution of the physico-chemical properties under irradiation. All known radiation-induced point defects in clay minerals are detected using Electron Paramagnetic Resonance Spectroscopy. They mostly consist in electron holes located on oxygen atoms of the structure, and can be differentiated through their nature and their thermal stability. For instance, several are associated to a ? orbital on a Si-O bond. One defect, namely the A-center, is stable over geological periods at ambiant temperature. These point defects are produced mainly by ionizing radiations. By contrast to point defects, it was shown that electron or heavy ion irradiation easily produces amorphization in smectites. Two main applications of radiation-induced defects in clay minerals are derived : (i) the use of defects as tracers of past radioactivity. In geosystems where the age of the clay can be constrained, migrations of radioelements can be reconstructed in natural analogues of the far field of high level nuclear waste repositories. When the dose rate may be assumed constant over time, the paleodose is used to date clay populations, an approach applied to laterites of the Amazon basin. (ii) The influence of radiation on clay mineral properties that remains poorly documented, although it is an important issue in various domains such as the safety assessment of the high level nuclear waste repositories. In case of a leakage of transuranic elements from the radioactive wasteform, alpha recoil nuclei would amorphize smectite after a period much lower than the disposal lifetime. By contrast, amorphisation from ionizing radiation is unlikely over 1 million years. Furthermore, it was shown that amorphization greatly enhances the dissolution kinetics of smectite, a result that must be taken into account in the safety assessment of engineered barriers.

Allard, T.

2011-12-01

25

Immersion Freezing of Clay Minerals and its Time Dependence  

NASA Astrophysics Data System (ADS)

Immersion ice nucleation efficiency of clay minerals has been investigated using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Various clay dust samples, including two illite as well as three kaolinite standards, have been examined in the temperature range between 238 K and 255 K. We observed two trends in immersion ice nucleation properties as cloud expansion conditions in the AIDA are varied. First, as previously described in the literature, the supersaturation required for the immersion freezing of clay minerals decreased with decreasing temperature and increasing inferred ice-active surface site densities. Second, the ice nucleation activity of clay minerals strongly depended on the solo-parameter, which is the rate change in temperature (i.e., dNice/dT = ?Nice/?t ÷ ?T/?t). Further time dependence of ice formation is investigated and discussed as a function of cooling rates, ice nuclei (IN), and aerosol concentrations. Ice residuals collected through a pumped counterflow virtual impactor are examined by electron microprobe analyses to seek the true chemical and physical identity of IN in clay minerals. Brief comparisons of AIDA measurement to the measurements with other ice nucleation chambers (e.g., ETH-PINC, FINCH, and commercially available DMT-SPIN) are also presented.

Hiranuma, N.; Moehler, O.; Bundke, U.; Cziczo, D. J.; Danielczok, A.; Ebert, M.; Garimella, S.; Hoffmann, N.; Kanji, Z. A.; Kiselev, A. A.; Raddatz, M.; Stetzer, O.

2012-12-01

26

Iodide interactions with clay minerals: Batch and diffusion studies  

NASA Astrophysics Data System (ADS)

Clay minerals are likely candidates to aid in nuclear waste isolation due to their low permeability, favorable swelling properties, and high cation sorption capacities. Iodine-129 is often the major driver of exposure risk from nuclear waste repositories at timescales >10,000 years. Therefore, understanding the geochemical cycling of iodine in clays is critical in developing defensible quantitative descriptions of nuclear waste disposal. Anions are not typically considered to interact with most clays as it is assumed that the fixed negative charge of clays actively repels the dissoloved anion. This is corroborated by many batch studies, but diffusion experiments in compacted clays have shown iodide retardation relative to chloride. The reasons for this are unknown; however, several possible hypotheses include: redox transformation controls on sorption behavior, complex surface charge environments due to overlapping charge domains, and sorption to ancillary minerals or weathering products. Seven different clay minerals have been examined using several techniques to chracterize the surface charge environment and iodide uptake. The use of a series of clays shifts the independent variable away from water chemistry characteristics (pH, contaminant concentration), and toward structural characterisitics of clay minerals including isomorphous substitution and clay texture. Iodide uptake batch experiments were completed with the clay minerals in a range of swamping electrolytes. The results give evidence for a novel uptake mechanism involving ion pair formation and iodide concentration within nano-confined environments. These results were further tested using diffusional columns where nano-confined regimes make up a larger proportion of the total porosity. These columns were compacted to different hydrostatic pressures and saturated with different ionic compositions. Porosity distributions were characterized with a fluoride tracer. Iodide diffusion characteristics were found to be dependent on ionic composition and confining pressure. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corperation, for the U.S. Department of Energy's Nation Nuclear Security Administration under contract DE-AC04-94AL85000.

Miller, A. W.; Kruichak, J.; Mills, M.; Wang, Y.

2012-12-01

27

First direct detection of clay minerals on Mars  

NASA Technical Reports Server (NTRS)

Magnesian clays or clay-type minerals were conclusively detected in the martian regolith. Near-IR spectral observations of Mars using the Mauna Kea 2.2-m telescope show weak but definite absorption bands near microns. The absorption band positions and widths match those produced by combined OH stretch and Mg-OH lattice modes and are diagnostic of minerals with structural OH such as clays and amphiboles. Likely candidate minerals include serpentine, talc, hectorite, and sponite. There is no spectral evidence for aluminous hydroxylated minerals. No distinct band occurs at 2.55 microns, as would be expected if carbonates were responsible for the 2.35 micron absorption. High-albedo regions such as Elysium and Utopia have the strongest bands near 2.35 microns, as would be expected for heavily weathered soils. Low-albedo regions such as Iapygia show weaker but distinct bands, consistent with moderate coatings, streaks, and splotches of bright weathered material. In all areas observed, the 2.35-micron absorption is at least three times weaker than would be expected if well-crystallized clay minerals made up the bulk of bright soils on Mars.

Singer, R. B.; Owensby, P. D.; Clark, R. N.

1985-01-01

28

Reactivity of clay minerals with acids and alkalies  

USGS Publications Warehouse

One-g samples of a montmorillonite, a metabentonite, an illite, two kaolinites, and three halloysites were treated with 50 ml of hydrochloric acid (6??45 N, 1:1), acetic acid (4??5 N, 1:3), sodium hydroxide (2??8 N), sodium chloride solution (pH 6??10; Na = 35???; Cl = 21??5???), and natural sea water (pH 7??85; Na = 35??5???; Cl = 21??5???) for a 10-day period in stoppered plastic vials. The supernatant solutions were removed from the clay minerals and analyzed for SiO2, Al2O3, CaO, MgO, Na2O, and K2O. All the solutions removed some SiO2, Al2O3, and Fe2O3 from the samples, but the quantities were small. Sodium hydroxide attacked the kaolin group minerals more strongly than it did montmorillonite, metabentonite, or illite. Halloysite was more strongly attacked by hydrochloric acid than was any of the other experimental minerals. Hydrochloric acid removed iron oxide coatings from soil clay minerals, but acetic acid did not remove them completely. The samples most strongly attacked by HCl and NaOH were examined by X-ray diffraction. Acid treatment did not destroy the structure of the clays, but the halloysite structure was partially destroyed. Sodium hydroxide attacked the halloysite structure, as shown by chemical analysis and X-ray diffraction. These experiments show that treatment in dilute acids has no harmful effect in the preparation of clays for X-ray diffraction. Acetic acid is preferred to hydrochloric acid for this purpose. Hydrochloric acid cleans clay minerals by removing free iron oxide from the surface; acetic acid is less effective. ?? 1971.

Carroll, D.; Starkey, H. C.

1971-01-01

29

The Effect of Mechanochemical Treatments on Clay Minerals and the Mechanochemical Adsorption of Organic Materials onto Clay Minerals  

Microsoft Academic Search

The present paper reviews investigations on the mechanochemical reactions occurring during the grinding of kaolinite and the mechanochemical adsorption of polar organic compounds by expanding and nonexpanding clay minerals, carried out in our laboratory by IR spectroscopy, supplemented by XRD and TG-DTA techniques. Kaolinite was ground in the absence and presence of diluents (alkali halides) and IR spectra were recorded

S. Yariv; I. Lapides

2000-01-01

30

Sorption of tylosin on clay minerals.  

PubMed

The equilibrium sorption of tylosin (TYL) on kaolinite and montmorillonite was measured at different solution pH using batch reactor systems. The results showed that all the sorption isotherms were nonlinear and that the nonlinearity decreased as the solution pH increased for a given clay. At a specific aqueous concentration, the single-point sorption distribution coefficient (KD) of TYL decreased rapidly as the solution pH increased. A speciation-dependent sorption model that accounted for the contributions of the cationic and neutral forms of TYL fit the data well, suggesting that the sorption may be dominated by both ion exchange and hydrophobic interactions. The isotherm data also fit well to a dual mode model that quantifies the contributions of a site-limiting Langmuir component (ion exchange) and a non-specific linear partitioning component (hydrophobic interactions). X-ray diffraction analyses revealed that the interlayers of montmorillonite were expanded due to the uptake of TYL. TYL molecules likely form a monolayer surface coverage. PMID:24007614

Zhang, Qian; Yang, Chen; Huang, Weilin; Dang, Zhi; Shu, Xiaohua

2013-11-01

31

Immersion freezing of clay minerals and bacterial ice nuclei  

NASA Astrophysics Data System (ADS)

The immersion mode ice nucleation efficiency of clay minerals and biological aerosols has been investigated using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Both monodisperse and polydisperse populations of (1) various clay dust samples as well as (2) Snomax® (a proxy for bacterial ice nucleators) and (3) hematite are examined in the temperature range between -4°C and -35°C. The temperature dependence of ice formation inferred by the INAS (Ice Nucleation Active Surface-Site) density is investigated and discussed as a function of cooling rate and by comparing to predicted nucleation rates (i.e., classical nucleation theory with ?-probability density function nucleation scheme). To date, we observe that maintaining constant AIDA temperature does not trigger any new ice formation during the immersion freezing experiments with clay dust samples and Snomax®, implying strong temperature dependency (and weak time dependency) within our time scales and conditions of experiments. Ice residuals collected through a newly developed PCVI (Pumped ounter-flow Virtual Impactor) with the 50% cut size diameter of 10 to 20 ?m have also been examined by electron microscope analyses to seek the chemical and physical identity of ice nuclei in clay minerals. In addition to the AIDA results, complementary measurements with mobile ice nucleation counters are also presented.

Hiranuma, Naruki; Möhler, Ottmar; Bingemer, Heinz; Bundke, Ulrich; Cziczo, Daniel J.; Danielczok, Anja; Ebert, Martin; Garimella, Sarvesh; Hoffmann, Nadine; Höhler, Kristina; Kanji, Zamin A.; Kiselev, Alexei; Raddatz, Michael; Stetzer, Olaf

2013-05-01

32

Magnesium isotope fractionation during extreme weathering of basalt controlled by clay mineral formation  

NASA Astrophysics Data System (ADS)

Chemical weathering of silicate rocks is considered to be one of the major processes that affects the chemical composition of the continental crust and the carbon cycle. More recently, application of Mg isotopes as geochemical proxy of chemical weathering has attracted considerable attention. Primary mineral dissolution and secondary mineral formation are considered as the two principal processes controlling Mg isotope fractionation during chemical weathering, but the impact of the mineralogy of secondary phases on Mg isotope fractionation is still unclear. To better understand the role of secondary mineral formation in the fractionation of Mg isotopes during extreme weathering, we have determined the chemical compositions and Mg isotopic ratios of a set of well-characterized saprolites developed on Neogene basalt in Hainan island, south China. The weathering products are dominated by kaolin-group minerals and Al- and Fe-oxy-hydroxides and the primary minerals of the parent rocks are almost absent due to the extreme weathering. Relative to the fresh basalts, magnesium is completely depleted in the saprolites, the values of percentage change of Mg ratios to Th relative to parent rock (?Th,Mg) range between -92.91% and -99.10%. The ?26Mg of saprolites vary from -0.51 to +0.34 % relative to the reference material DSM3. The unaltered basalt has a ?26Mg isotopic composition of -0.33%, similar to fresh oceanic basalt samples. Saprolite at the top has the lowest ?26Mg value of -0.51% and the heaviest ?26Mg value occur at 3.65m depth, where most mobile elements (eg. Al, Mg, Mn) are enriched. Except three samples at the upper section of the profile, the ?26Mg value of the fresh basalt is lighter than that of the overlying saprolites. These observations are consistent with release of light Mg to the hydrosphere and concentration of isotopically heavier Mg in the weathered products. A linear correlation between ?26Mg and the abundance of clay minerals is observed in this weathering profile. ?26Mg values negatively correlate with kaolinite modal abundance and positively correlates with halloysite modal abundance. These results suggest that the formation of halloysite during basalt weathering preferentially incorporates heavy Mg isotopes whereas formation of kaolinite preferentially incorporates light Mg isotopes. Our results highlight that the formation of secondary clay minerals controls Mg isotope fractionation during weathering, and this fractionation is highly dependent on clay mineral type and the Mg crystalline site in the minerals.

Huang, K.; Teng, F.; Ma, J.; Wei, G.; Bao, Z.

2011-12-01

33

Program and Abstracts for Clay Minerals Society 28th Annual Meeting  

NASA Technical Reports Server (NTRS)

This volume contains abstracts that were accepted for presentation at the annual meeting. Some of the main topics covered include: (1) fundamental properties of minerals and methods of mineral analysis; (2) surface chemistry; (3) extraterrestrial clay minerals; (4) geothermometers and geochronometers; (5) smectite, vermiculite, illite, and related reactions; (6) soils and clays in environmental research; (7) kaolinite, halloysite, iron oxides, and mineral transformations; and (8) clays in lakes, basins, and reservoirs.

1991-01-01

34

Role of clay minerals in the physicomechanical deterioration of sandstone  

NASA Astrophysics Data System (ADS)

Extensive weathering suffered by sandstone in natural outcrops as well as in historical buildings could be attributed among other mechanisms to the action of wetting and drying cycles. We have recently shown how to quantify the stresses generated during such cycles to determine whether damage can take place. This procedure is further developed in this paper and applied to the Tarifa sandstone, a sandstone with a 7 wt % content of clay minerals and used in the main façade of the church of San Mateo in Tarifa (Cádiz, Spain) for which the relevant material properties are measured. It is shown that tensile stresses during drying can cause cracking of thin elements and that shear forces can cause buckling of wetted surfaces more generally, eventually resulting in scaling and/or contour scaling. These predictions are supported by visual observations on the monument showing degradation patterns characteristic of those types of damage. Similar weathering forms have been observed in natural sandstone landscapes. Application of swelling inhibitors (e.g., cationic surfactants) that selectively adsorb on the clay basal planes, results in a substantial swelling reduction. This confirms that the swelling clays typically present in sandstone are pivotal for its weathering and indicates that swelling inhibitors are a potentially valuable treatment to prevent or minimize damage to stone. The circumstances that would lead to weathering are discussed in relation to sandstone material properties in the wet and dry state. Clay-bearing stones are shown to exhibit softening during wetting, as well as viscoelastic stress relaxation, which is expected to limit the extent of damage. These results may aid in the better understanding of sandstone weathering both in nature and in urban environment and may help develop conservation methods to mitigate wetting/drying damage in ornamental sandstone or to prevent pore plugging in reservoir sandstones.

JiméNez-GonzáLez, Inmaculada; RodríGuez-Navarro, Carlos; Scherer, George W.

2008-06-01

35

Kinetic Study of Denatonium Sorption to Smectite Clay Minerals  

PubMed Central

Abstract The denatonium cation, as a benzoate salt, is the most bitter cation known to modern society and is frequently added to consumer products to reduce accidental and intentional consumption by humans and animals. Denatonium can enter the environment by accidental discharges, potentially rendering water supplies undrinkable. Interactions of denatonium with soil components (i.e., smectite minerals) ultimately control the environmental fate of denatonium, but the current literature is devoid of studies that evaluate denatonium sorption to smectite minerals. This study investigated the mechanism and kinetics of denatonium sorption to smectite clay minerals as a function of smectite type, temperature, pH and ionic strength. Uptake by synthetic mica montmorillonite (Syn-1), Wyoming montmorillonite (SWy-2), and Texas montmorillonite (STx-1b) at 305K was rapid, with equilibrium being reached within 2?min for all clays. Complete removal of denatonium was observed for STx-1b at pH 6.9, while partial removal was observed for Syn-1 and SWy-2. Kinetic behavior of SWy-2 and Syn-1 is consistent with a pseudo–second-order model at 305K. An activation energy of +25.9 kJ/mol was obtained for sorption to Syn-1 and was independent of temperature between 286K and 338K. Activation-free energy (?G*), activation enthalpy (?H*), and activation entropy (?S*) for Syn-1 were found to be +62.91 kJ/mol, +23.36 kJ/mol, and ?0.130 kJ/(K·mol), respectively. Sorption capacities at pH 3.6, 6.9, and 8.2 were constant at 1.3×10?2 g denatonium/g clay; however, the kinetic rate constant increased by 56%, going from acidic to basic solution conditions. Distribution coefficients were negatively correlated with ionic strength, suggesting cation exchange. Collectively, results suggested that smectite minerals can serve as efficient sinks for denatonium cations. This is much-needed information for agencies developing regulations regarding denatonium usage and for water treatment professionals who may ultimately have to treat denatonium-impacted water supplies.

Crosson, Garry S.; Sandmann, Emily

2013-01-01

36

Soft X-ray Spectromicroscopy Study of Mineral-Organic Matter Associations in Pasture Soil Clay Fractions.  

PubMed

There is a growing acceptance that associations with soil minerals may be the most important overarching stabilization mechanism for soil organic matter. However, direct investigation of organo-mineral associations has been hampered by a lack of methods that can simultaneously characterize organic matter (OM) and soil minerals. In this study, STXM-NEXAFS spectroscopy at the C 1s, Ca 2p, Fe 2p, Al 1s, and Si 1s edges was used to investigate C associations with Ca, Fe, Al, and Si species in soil clay fractions from an upland pasture hillslope. Bulk techniques including C and N NEXAFS, Fe K-edge EXAFS spectroscopy, and XRD were applied to provide additional information. Results demonstrated that C was associated with Ca, Fe, Al, and Si with no separate phase in soil clay particles. In soil clay particles, the pervasive C forms were aromatic C, carboxyl C, and polysaccharides with the relative abundance of carboxyl C and polysaccharides varying spatially at the submicrometer scale. Only limited regions in the soil clay particles had aliphatic C. Good C-Ca spatial correlations were found for soil clay particles with no CaCO3, suggesting a strong role of Ca in organo-mineral assemblage formation. Fe EXAFS showed that about 50% of the total Fe in soils was contained in Fe oxides, whereas Fe-bearing aluminosilicates (vermiculite and Illite) accounted for another 50%. Fe oxides in the soil were mainly crystalline goethite and hematite, with lesser amounts of poorly crystalline ferrihydrite. XRD revealed that soil clay aluminosilicates were hydroxy-interlayered vermiculite, Illite, and kaolinite. C showed similar correlation with Fe to Al and Si, implying a similar association of Fe oxides and aluminosilicates with organic matter in organo-mineral associations. These direct microscopic determinations can help improve understanding of organo-mineral interactions in soils. PMID:24837340

Chen, Chunmei; Dynes, James J; Wang, Jian; Karunakaran, Chithra; Sparks, Donald L

2014-06-17

37

Metachromasy as an indicator of photostabilization of methylene blue adsorbed to clays and minerals.  

PubMed

The influence of methylene blue adsorption to different clays on its photodegradation was studied. Methylene blue in solution was decomposed by sunlight in a zero-order process. Adsorption to some clay minerals (sepiolite and vermiculite) and a zeolite (clinoptilolite) accelerated the degradation process, and converted it to a first-order reaction. On the other hand, adsorption to other clay minerals (palygorskite and montmorillonite) stabilized the dye and prevented its degradation. Interestingly, in the clay-dye complexes that exhibited stability, clear metachromasy of the adsorbed methylene blue occurred, whereas the effect was not observed in the clay-dye complexes that underwent photodegradation. PMID:23474529

Samuels, Maya; Mor, Omer; Rytwo, Giora

2013-04-01

38

Qualitative color test for rapid identification of the clay mineral groups  

Microsoft Academic Search

A color test based on the adsorption and oxidation of p-amino phenol on clay mineral surfaces has been developed for routine identification of the principal clay mineral groups, the montmorillonoid, illite or hydrous mica, and kaolin families. The new test has been found to compare favorably with other staining and color tests currently in use. The test procedure involves the

W. W. Hambleton; C. G. Dodd

1953-01-01

39

An Overview of the High-Pressure Vibrational Spectra of Clays and Related Minerals  

Microsoft Academic Search

An overview of the effect of high external pressures on clays and related minerals is presented. The results show that this is an area that will welcome further investigation in the future, especially in view of the importance of clay minerals in the Earths's mantle and, possibly, even in prebiotic chemistry in the formation of amino acids and the mineralogy

Ian S. Butler; Ray L. Frost

2006-01-01

40

Use of energy-dispersive x-ray fluorescence analysis in clay mineral ion exchange studies  

Microsoft Academic Search

A rapid, reliable, semiquantitative method for following ion exchange processes in clay minerals is described. An energy-dispersive x-ray fluorescence technique is used. The completeness of the exchange process for the clay mineral montmorillonite was investigated for the ions Rb\\/sup +1\\/, Sr\\/sup +2\\/, and Y\\/sup +3\\/. Samples of clay, suspended on asbestos, were packed in an ion exchange column and solutions

J. F. Mucci; R. L. Stearns

1977-01-01

41

Review of XRD-based quantitative analyses of clay minerals in soils: the suitability of mineral intensity factors  

Microsoft Academic Search

The determination of the types and relative amounts of the minerals present in soil forms an essential component of most soil characterization efforts. This paper reviews protocols for XRD-based quantitative clay mineral analysis in soils, with emphasis on methods using mineral intensity factors in combination with the so-called 100% approach. We summarize methodological differences and characteristic features and give information

Maren Kahle; Markus Kleber; Reinhold Jahn

2002-01-01

42

Formation of replicating saponite from a gel in the presence of oxalate: implications for the formation of clay minerals in carbonaceous chondrites and the origin of life.  

PubMed

The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth. PMID:22794298

Schumann, Dirk; Hartman, Hyman; Eberl, Dennis D; Sears, S Kelly; Hesse, Reinhard; Vali, Hojatollah

2012-06-01

43

Occurrence and Alteration of Clay Minerals in the Caribbean Sea.  

National Technical Information Service (NTIS)

Both vertical and horizontal trends in clay mineralogy are examined in six cores from the southwestern and central Caribbean. An additional sample is analyzed for clay mineralogy from the Magdalena River in Colombia. X-ray diffraction, differential therma...

C. N. Johnson

1973-01-01

44

Basaltic andesite, altered basalt, and a TES-based search for smectite clay minerals on Mars  

NASA Astrophysics Data System (ADS)

The global-scale surface type 2 unit first identified with the Mars Global Surveyor Thermal Emission Spectrometer (TES) remains enigmatic. Competing hypotheses suggest that it represents either basaltic andesite or some form of altered basalt rich in dioctahedral smectite clay minerals and/or spectrally similar amorphous silica phases. Common dioctahedral smectites contain a diagnostic feature in a portion of TES spectra that has been excluded in previous studies because of atmospheric CO2 absorption. We exploit the relative transparency of this spectral region to develop two indices that in tandem, distinguish between certain smectites and amorphous phases. Smectites are not detected in northern lowlands type 2 settings, consistent with other datasets, but the case for primary or secondary amorphous silica phases is strengthened. Separately, one index reveals an abundance of isolated type 2 occurrences in the southern high-latitudes (>50°) associated with dunes, the other shows olivine concentrations between -40° and +30°.

Ruff, S. W.; Christensen, P. R.

2007-05-01

45

Transport and selective uptake of radium into natural clay minerals  

NASA Astrophysics Data System (ADS)

Understanding of the environmental behavior of Ra is important from the viewpoint of the long-termed repository safety of radioactive waste, but investigation of Ra behavior in natural environment is difficult to detect. We found isotopic evidence of Ra transportation and its selective uptake into clay minerals from Pb isotopic analyses. Illite grains found in calcite veins included in sandstone near the Oklo uranium deposit, Republic of Gabon, show extremely low 207Pb/ 206Pb (˜ 0.0158) isotopic ratios. Although the Pb isotopic ratios of calcite and quartz coexisting with illite indicate the formation age of each component, those of illite do not. In addition, illite grains having low 207Pb/ 206Pb isotopic ratios contain a strongly large amount of Ba (1230 to 6010 ppm) in contrast with low contents of Ba in calcite and quartz (< 0.26 ppm). Considering the chemical similarity between Ba and Ra, the 207Pb/ 206Pb isotopic data suggest an excess of 206Pb due to selective adsorption of 226Ra (and also Ba) into illite grains. This is a very rare example to show evidence of the selective adsorption behavior of Ra from the isotopic excesses of 206Pb, although the adsorption ability of Ra itself in nature was largely reported.

Hidaka, Hiroshi; Horie, Kenji; Gauthier-Lafaye, Françoise

2007-12-01

46

Lithium, a preliminary survey of its mineral occurrence in flint clay and related rock types in the United States  

USGS Publications Warehouse

Maximum concentrations of lithium found in samples of flint clay and associated rocks of Pennsylvanian age in different States, in parts per million (ppm), are: Missouri, 5100; Pennsylvania-Maryland, 2100; Kentucky, 890; Ohio, 660; Alabama, 750; and Illinois, 160. Lithium-bearing kaolin deposits are distributed in the Coastal Plain province from New Jersey to Texas, and one occurs in Idaho; maximum lithium concentrations in samples from these deposits range from 64 to 180 ppm. The maximum concentration found in the Arkansas bauxite region is 460 ppm and that in flint clay in Colorado is 370 ppm. Samples from areas other than Pennsylvania, Maryland, Kentucky and Missouri are relatively few in number, represent mostly commercially valuable clays, and represent only a part of the refractory clay deposits in the United States. Data are not available on the clays associated with these deposits that may be unusable because they contain too much lithium as well as other deleterious elements. In both Pennsylvania and Missouri, lithium contents vary regionally between districts and locally between deposits. In samples containing more than 2000 ppm lithium, the lithium occurs in a dioctahedral chlorite mineral very similar to cookeite, which previously has not been recognized in sedimentary clays. The associated clays consist chiefly of well-crystallized kaolinite. The dioctahedral chlorite, however, seems to be most abundant where diaspore and boehmite occur along with the kaolinite. Barium, chromium, copper, phosphorus and strontium are present in some samples in amounts of several hundred pans per million or more, and may contribute to the failure of some clays to perform satisfactorily in firing tests. Lithium-rich clays could serve as a significant lithium resource in the very distant future. Clays that contain as much as 1% lithium may be common enough in Missouri or in Pennsylvania to be produced as a by-product to help support benefication costs for refractory clays. Sufficient amounts of lithium-rich clay may be found in deposits that have been explored, found unsatisfactory for normal refractory uses, and not developed. The lithium-rich clay in some deposits presently being worked may be worth stockpiling for eventual use. ?? 1978.

Tourtelot, H. A.; Brenner-Tourtelot, E. F.

1978-01-01

47

Determination of the composition of the organic matter chemically stabilized by agricultural soil clay minerals: Spectroscopy and Density Fractionation  

NASA Astrophysics Data System (ADS)

The interactions between soil organic matter and clay minerals are considered important processes because of their ability to sequester C in soil for long periods of time, and hence control C in the global C cycle when present. However, differing results have been reported regarding the composition of the soil organic matter - aromatic fractions versus aliphatic fractions - associated with clay minerals. To clarify this critical issue and better understand the C sequestration process in soils, we aimed to determine the nature of the chemically bound natural organic matter on clay surfaces, and to probe the speciation and spatial distribution of C in the soil clay nanoparticles using direct spectroscopic measurements namely solid-state CP-MAS and DP-MAS 13C NMR spectroscopy, x-ray diffraction spectroscopy (XRD), and scanning transmission x-ray microscopy (STXM). We tested the hypotheses that peptides and polysaccharides are stabilized by the smectite-illite clay while the lipids and black carbon are a separate phase; and that they are evenly distributed on clay surfaces. A soil clay fraction (5.5% organic C) was isolated from the surface of a prairie soil (Mollisol) in southwestern Minnesota, characterized by a pH 6.0, 32.5% clay content, and 3.7% organic carbon, using a sonication-sedimentation-siphoning process in distilled water. Then was subjected to density separation combined with low energy ultrasonic dispersion to separate the free organic and black C (light fraction) from the chemically bound C (heavy fraction). The XRD results indicated a dominance of interstratified smectite-illite clays in soil. The 13C-NMR spectra of the soil clay fraction suggested that polysaccharides and polypeptides are the prevailing components of the organic matter associated with the mineral clay, with only a minor component of aromatic C. The light fraction has strong alkyl C-H bands characteristic of fatty acids plus strong C-O bands characteristic of polysaccharides, including the anomeric C band centered at 105 ppm. The aromatic band at 130 ppm and the phenolic C-O band at 150 pm are strong as well indicating the presence of black carbon and lignin-derived components, contrary to the heavy fraction where they are almost absent. STXM results indicated that the proteins are abundant in the soil clay fraction, separate from lipids, and partially associated with saccharides. The black carbon constitutes a separate phase, but is amply present with lipids and lignin-derived compounds in the light fraction. We conclude that (1) the smectite-illite sheets in our soils preferentially retain peptides, and polysaccharides favoring the protection of these normally readily biodegradable fractions relative to the lignin-derived phenolic components; (2) the black carbon constitutes a major component of the light fraction, and is partially attached to the organic matter bonded with the smectitic clays; and (3) the lipids are associated with soil clay fraction as a separate phase, but are not bound to clay minerals.

Oufqir, Sofia; Bloom, Paul; Toner, Brandy; Hatcher, Patrick

2014-05-01

48

Hydrothermal Reactions of Shales and Clay Minerals with Cesium Phases Representative of Spent Reactor Fuel.  

National Technical Information Service (NTIS)

The immobilization of cesium extracted from spent fuel (SF) by ion exchange and direct chemical reaction with clay minerals and shales was investigated under hydrothermal, closed-system conditions. The exact cesium phases in SF are not known with certaint...

S. Komarneni, G. J. McCarthy, W. B. White

1979-01-01

49

The Measurement of the Heat of Reaction between Proteins and Clay Minerals by Microcalorimetry.  

National Technical Information Service (NTIS)

The heat of reaction during the adsorption of proteins by clay minerals was investigated. All measurements were obtained with a Calvet Microcalorimeter modified and calibrated for adequate mixing in the calorimeter cell to allow complete reaction. (Modifi...

B. M. Kilcullen

1973-01-01

50

Sorption-desorption behavior of PCP on soil organic matter and clay minerals.  

PubMed

Pentachlorophenol (PCP) contamination is a severe environmental problem due to its widespread occurrence, toxicity and recalcitrance. In order to gain a better understanding of the fate of PCP in soils, the role of the soil organic matter (SOM) and clay minerals in the PCP sorption-desorption was studied on two bulk field soils, two subsoils (i.e., SOM or clay-removed soil) and two artificial soils. The two field soils used were a silty loam from New Mexico (NM) containing 10% clay and a sandy-clay-loam from Colombia (CO) South America comprised of 18% clay minerals. The bulk CO soil containing kaolinite sorbed significantly less PCP than the NM soil. All soils depicted an apparent hysteresis during sorption. The CO bulk and subsoils desorbed 14-20% and 15-26% of the sorbed PCP respectively whereas the NM bulk and subsoils desorbed only 4-12% and 5-16%, respectively. Experiments conducted with pure clay and artificial soils indicated that the expandable clay minerals were key sorbent material. Additional studies to investigate the interaction between SOM and clay minerals are needed to fully understand sorptive phenomena. PMID:16473390

Pu, Xunchi; Cutright, Teresa J

2006-08-01

51

Subsurface water and clay mineral formation during the early history of Mars  

Microsoft Academic Search

Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter

Bethany L. Ehlmann; John F. Mustard; Scott L. Murchie; Jean-Pierre Bibring; Alain Meunier; Abigail A. Fraeman; Yves Langevin

2011-01-01

52

Use of clay minerals in reconstructing geological processes: recent advances and some perspectives  

Microsoft Academic Search

This article reviews that clay literature from the last ten years, which is devoted to the applications of clay minerals in the interpretation of geological processes in sedimentary basins. The results, selected by the author as being of particular interest, are presented, arranged according to the successive phases of the rock cycle. The research field defined in the title has

J. Srodon

1999-01-01

53

Thermo-IR-spectroscopy analysis of the interactions between organic pollutants and clay minerals  

Microsoft Academic Search

A short description of thermo-IR-spectroscopy analysis is given together with some examples of the interactions between hazardous organic pollutants and clay minerals. Self-supported films of organo-montmorillonite and laponite complexes can be heated in a vacuum cell and the IR spectra of the samples recorded at different temperatures. Organo complexes of other clay minerals can be heated as alkali-halide disks. In

S. Yariv

1996-01-01

54

Evaluation of the medicinal use of clay minerals as antibacterial agents.  

PubMed

Natural clays have been used to heal skin infections since the earliest recorded history. Recently our attention was drawn to a clinical use of French green clay (rich in Fe-smectite) for healing Buruli ulcer, a necrotizing fasciitis ('flesh-eating' infection) caused by Mycobacterium ulcerans. These clays and others like them are interesting as they may reveal an antibacterial mechanism that could provide an inexpensive treatment for this and other skin infections, especially in global areas with limited hospitals and medical resources.Microbiological testing of two French green clays, and other clays used traditionally for healing, identified three samples that were effective at killing a broad-spectrum of human pathogens. A clear distinction must be made between 'healing clays' and those we have identified as antibacterial clays. The highly adsorptive properties of many clays may contribute to healing a variety of ailments, although they are not antibacterial. The antibacterial process displayed by the three identified clays is unknown. Therefore, we have investigated the mineralogical and chemical compositions of the antibacterial clays for comparison with non-antibacterial clays in an attempt to elucidate differences that may lead to identification of the antibacterial mechanism(s).The two French green clays used to treat Buruli ulcer, while similar in mineralogy, crystal size, and major element chemistry, have opposite effects on the bacterial populations tested. One clay deposit promoted bacterial growth whereas another killed the bacteria. The reasons for the difference in antibacterial properties thus far show that the bactericidal mechanism is not physical (e.g., an attraction between clay and bacteria), but by a chemical transfer or reaction. The chemical variables are still under investigation.Cation exchange experiments showed that the antibacterial component of the clay can be removed, implicating exchangeable cations in the antibacterial process. Furthermore, aqueous leachates of the antibacterial clays effectively kill the bacteria. Progressively heating the clay leads first to dehydration (200 degrees C), then dehydroxylation (550 degrees C or more), and finally to destruction of the clay mineral structure by (~900 degrees C). By identifying the elements lost after each heating step, and testing the bactericidal effect of the heated product, we eliminated many toxins from consideration (e.g., microbes, organic compounds, volatile elements) and identified several redox-sensitive refractory metals that are common among antibacterial clays. We conclude that the pH and oxidation state buffered by the clay mineral surfaces is key to controlling the solution chemistry and redox related reactions occurring at the bacterial cell wall. PMID:20640226

Williams, Lynda B; Haydel, Shelley E

2010-07-01

55

Clay Minerals as Solid Acids and Their Catalytic Properties.  

ERIC Educational Resources Information Center

Discusses catalytic properties of clays, attributed to acidity of the clay surface. The formation of carbonium ions on montmorillonite is used as a demonstration of the presence of surface acidity, the enhanced dissociation of water molecules when polarized by cations, and the way the surface can interact with organic substances. (Author/JN)

Helsen, J.

1982-01-01

56

Enhanced cellular preservation by clay minerals in 1 billion-year-old lakes.  

PubMed

Organic-walled microfossils provide the best insights into the composition and evolution of the biosphere through the first 80 percent of Earth history. The mechanism of microfossil preservation affects the quality of biological information retained and informs understanding of early Earth palaeo-environments. We here show that 1 billion-year-old microfossils from the non-marine Torridon Group are remarkably preserved by a combination of clay minerals and phosphate, with clay minerals providing the highest fidelity of preservation. Fe-rich clay mostly occurs in narrow zones in contact with cellular material and is interpreted as an early microbially-mediated phase enclosing and replacing the most labile biological material. K-rich clay occurs within and exterior to cell envelopes, forming where the supply of Fe had been exhausted. Clay minerals inter-finger with calcium phosphate that co-precipitated with the clays in the sub-oxic zone of the lake sediments. This type of preservation was favoured in sulfate-poor environments where Fe-silicate precipitation could outcompete Fe-sulfide formation. This work shows that clay minerals can provide an exceptionally high fidelity of microfossil preservation and extends the known geological range of this fossilization style by almost 500?Ma. It also suggests that the best-preserved microfossils of this time may be found in low-sulfate environments. PMID:25068404

Wacey, David; Saunders, Martin; Roberts, Malcolm; Menon, Sarath; Green, Leonard; Kong, Charlie; Culwick, Timothy; Strother, Paul; Brasier, Martin D

2014-01-01

57

Synthesis and characterization of carbon nanotubes on clay minerals and its application to a hydrogen peroxide biosensor  

Microsoft Academic Search

In this study, we demonstrate the synthesis of carbon nanotubes (CNTs) on clay minerals, and the development of biosensors based on Nafion–CNT\\/Clay–Au and Nafion–CNT\\/Clay–Au–Glucose oxidase (GOD) composite films for the detection of hydrogen peroxide (H2O2) and glucose, respectively. The CNTs are synthesized on nickel cation exchanged clay mineral platelets. From field-emission scanning electron microscope images, X-ray diffraction, Fourier transfer infrared

Hao-Lin Hsu; Jih-Mirn Jehng

2009-01-01

58

Measurement of clay surface areas by polyvinylpyrrolidone (PVP) sorption and its use for quantifying illite and smectite abundance  

USGS Publications Warehouse

A new method has been developed for quantifying smectite abundance by sorbing polyvinylpyrrolidone (PVP) on smectite particles dispersed in aqueous solution. The sorption density of PVP-55K on a wide range of smectites, illites and kaolinites is ???0.99 mg/m2, which corresponds to ???0.72 g of PVP-55K per gram of montmorillonite. Polyvinylpyrrolidone sorption on smectites is independent of layer charge and solution pH. PVP sorption on Si02, Fe 2O3 and ZnO normalized to the BET surface area is similar to the sorption densities on smectites. ??-Al 2O3, amorphous Al(OH)3 and gibbsite have no PVP sorption over a wide range of pH, and sorption of PVP by organics is minimal. The insensitivity of PVP sorption densities to mineral layer charge, solution pH and mineral surface charge indicates that PVP sorption is not localized at charged sites, but is controlled by more broadly distributed sorption mechanisms such as Van der Waals' interactions and/or hydrogen bonding. Smectites have very large surface areas when dispersed as single unit-cell-thick particles (???725 m2/g) and usually dominate the total surface areas of natural samples in which smectites are present. In this case, smectite abundance is directly proportional to PVP sorption. In some cases, however, the accurate quantification of smectite abundance by PVP sorption may require minor corrections for PVP uptake by other phases, principally illite and kaolinite. Quantitative XRD can be combined with PVP uptake measurements to uniquely determine the smectite concentration in such sample. ?? 2004, The Clay Minerals Society.

Blum, A. E.; Eberl, D. D.

2004-01-01

59

The Efficiency of 24 Minerals as Deposition Ice Nuclei: Focus on Feldspars, Clays and Metals  

NASA Astrophysics Data System (ADS)

While the ice nucleating abilities of clay minerals have been extensively studied, those of the more minor mineralogical components of mineral dust have not been as widely examined. As a result, the deposition ice nucleating abilities of 24 atmospherically-relevant mineral samples were investigated using the University of Toronto continuous flow diffusion chamber at -40.0 × 0.3oC, using the same particle size (200nm) and preparation procedure throughout. The pure minerals' ice nucleating efficiencies were compared to those of complex mixtures (Arizona Test Dust and Mojave Desert Dust) and to that of lead iodide, which in the past was a prospective cloud seeding agent. Requiring a relative humidity with respect to ice (RHi) of 122.0 × 2.0% to activate 0.1% of the particles, lead iodide was the most efficient ice nucleus (IN) considered. Mojave Desert Dust (RHi 126.3 × 3.4%) and Arizona Test Dust (RHi 129.5 × 5.1%) exhibited lower but comparable activities. Through the analysis of a series of clay minerals (kaolinite, illite, montmorillonite), non-clay minerals (e.g. hematite, magnetite, calcite, cerussite, quartz, and other metal-containing species), and feldspar minerals (orthoclase, plagioclase) it was found that the feldspar minerals (particularly orthoclase), and not the clays, were the most efficient ice nuclei. Orthoclase and plagioclase were found to have critical RHi values of 127.1 × 6.3% and 136.2 × 1.3%, respectively. The presence of feldspars (most notably orthoclase) may play a large role in the deposition IN efficiencies of mineral dusts in spite of their lower percentage in composition relative to clay minerals. By contrast, most metal oxides, sulfide and sulfates were poor ice nuclei.

Yakobi-Hancock, J.; Ladino Moreno, L.; Abbatt, J.

2013-12-01

60

Reliable Quantitative Mineral Abundances of the Martian Surface using THEMIS  

NASA Astrophysics Data System (ADS)

The following presents a proof of concept that given quality data, Thermal Emission Imaging System (THEMIS) data can be used to derive reliable quantitative mineral abundances of the Martian surface using a limited mineral library. The THEMIS instrument aboard the Mars Odyssey spacecraft is a multispectral thermal infrared imager with a spatial resolution of 100 m/pixel. The relatively high spatial resolution along with global coverage makes THEMIS datasets powerful tools for comprehensive fine scale petrologic analyses. However, the spectral resolution of THEMIS is limited to 8 surface sensitive bands between 6.8 and 14.0 ?m with an average bandwidth of ~ 1 ?m, which complicates atmosphere-surface separation and spectral analysis. This study utilizes the atmospheric correction methods of both Bandfield et al. [2004] and Ryan et al. [2013] joined with the iterative linear deconvolution technique pioneered by Huang et al. [in review] in order to derive fine-scale quantitative mineral abundances of the Martian surface. In general, it can be assumed that surface emissivity combines in a linear fashion in the thermal infrared (TIR) wavelengths such that the emitted energy is proportional to the areal percentage of the minerals present. TIR spectra are unmixed using a set of linear equations involving an endmember library of lab measured mineral spectra. The number of endmembers allowed in a spectral library are restricted to a quantity of n-1 (where n = the number of spectral bands of an instrument), preserving one band for blackbody. Spectral analysis of THEMIS data is thus allowed only seven endmembers. This study attempts to prove that this limitation does not prohibit the derivation of meaningful spectral analyses from THEMIS data. Our study selects THEMIS stamps from a region of Mars that is well characterized in the TIR by the higher spectral resolution, lower spatial resolution Thermal Emission Spectrometer (TES) instrument (143 bands at 10 cm-1 sampling and 3x5 km pixel). Multiple atmospheric corrections are performed for one image using the methods of Bandfield et al. [2004] and Ryan et al. [2013]. 7x7 pixel areas were selected, averaged, and compared using each atmospherically corrected image to ensure consistency. Corrections that provided reliable data were then used for spectral analyses. Linear deconvolution is performed using an iterative spectral analysis method [Huang et al. in review] that takes an endmember spectral library, and creates mineral combinations based on prescribed mineral group selections. The script then performs a spectral mixture analysis on each surface spectrum using all possible mineral combinations, and reports the best modeled fit to the measured spectrum. Here we present initial results from Syrtis Planum where multiple atmospherically corrected THEMIS images were deconvolved to produce similar spectral analysis results, within the detection limit of the instrument. THEMIS mineral abundances are comparable to TES-derived abundances. References: Bandfield, JL et al. [2004], JGR 109, E10008 Huang, J et al., JGR, in review Ryan, AJ et al. [2013], AGU Fall Meeting

Smith, R. J.; Huang, J.; Ryan, A. J.; Christensen, P. R.

2013-12-01

61

Clay minerals from diallage in a warm and humid climate  

Microsoft Academic Search

In the course of chemical weathering, rockforming minerals release constituent ions changing into secondary minerals by alteration or recrystallization. Minerals formed in this way are primarily of colloidal nature, and are the most active portion in soils together with humus. The chemical weathering has dual meaning for soil fertility, that is, it provides soils with nutrients released and inorganic colloids

Shigenori Aomine; Nobufumi Miyauchi

1962-01-01

62

Clay-mineral suites, sources, and inferred dispersal routes: Southern California continental shelf.  

PubMed

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 microm-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Niño years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces. PMID:12648951

Hein, James R; Dowling, Jennifer S; Schuetze, Anthony; Lee, Homa J

2003-01-01

63

Clay-mineral suites, sources, and inferred dispersal routes: Southern California continental shelf  

USGS Publications Warehouse

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 ??m-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Nin??o years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces.

Hein, J. R.; Dowling, J. S.; Schuetze, A.; Lee, H. J.

2003-01-01

64

Modeling of Cation Binding in Hydrated 2:1 Clay Minerals - Final Report  

SciTech Connect

Hydrated 2:1 clay minerals are high surface area, layered silicates that play a unique role in determining the fate of radionuclides in the environment. This project consisted of developing and implementing computer simulation methods for molecular characterization of the swelling and ion exchange properties of Hydrated 2:1 clay minerals, and the subsequent analysis and theoretical modeling with a view toward improving contaminant transport modeling as well as soil remediation and radionuclide containment strategies. Project results included the (a) development of simulation methods to treat clays under environmentally relevant conditions of variable water vapor pressure; (b) calculation of clay swelling thermodynamics as a function of interlayer ion size and charge (calculated quantities include immersion energies, free energies, and entropies of swelling); and (c) calculation of ion exchange free energies, including contributions from changing interlayer water contents and layer spacing.

Smith, David E.

2000-09-14

65

Synthesis and characterization of low-charge sodium fluorophlogopite mica-type clay minerals  

Microsoft Academic Search

This work reports a solid-state synthesis of low-charge mica-type clay minerals using a fluoride flux method. Synthesized mica-type clay samples yielded hydrated phases with d-spacings in the range of 12.1–12.5 Å as revealed by powder X-ray diffraction (XRD). 29Si and 27Al magic angle spinning nuclear magnetic resonance (MASNMR) spectroscopy revealed the Si and Al nearest neighbor environments as well as the

Sridhar Komarneni; Ramesh Ravella; Young Dong Noh; Kenneth J. D. Mackenzie

2009-01-01

66

Molecular dynamics simulations of water, solution, and clay mineral-water systems (Invited)  

NASA Astrophysics Data System (ADS)

Clays and clay minerals together with zeolites are major mineral components in the earth's surface environment. These minerals interact with the atmosphere, natural water, inorganic and organic components in soils, etc. Physicochemical processes in the surface region are generally complex and difficult to understand because of the complicated "molecular" structures and the ambient conditions under wet circumstances. We have investigated the structure and physical/dynamical properties of the mineral-gas/liquid systems by means of molecular simulation methods; molecular dynamics and Metropolis Monte Carlo methods. Swelling of smectite and adsorption of inorganic molecules in clay minerals and zeolites, etc. were simulated and analyzed on the basis of the atomic and molecular processes. We have developed atomic and molecular interaction models of inorganic systems. The models compose of electrostatic, short range repulsive, van der Waals and covalent (radial and angular) terms with respect to all the elements appeared in the mineral-water systems. All of our molecular dynamics simulations (MD) were performed with full degree of freedom of atom motions. Using the model for H2O molecule, the structure and physical properties such as density, diffusion coefficients, etc. of ice polymorphs and water are well reproduced. Alkaliharide aqueous solutions and gas hydrates and their (hydrophobic) solutions are also reasonably simulated. Clay mineral-water interactions are particularly important to understand the mechanical and chemical processes in the environments, in order to develop nano-composite materials, and to use clays in engineering applications. Absorption and swelling are the most remarkable properties of clay minerals, specially smectite. We have investigate these properties by means of molecular simulation methods using various clay minerals-water/solution systems. The swelling curves, the relation between humidity and the basal spacings, were reproduced quantitatively, and nano-scopic structural and dynamic properties of interlayer aqueous solutions were obtained. Wetting of clay mineral surfaces determines the mechanical properties of clays, soils and sedimentary rocks. We investigated the wetting properties of smectite, kaolinite, pyrophyllite, brucite, etc. The wetness of these minerals is quite different with each other. The reson of these difference was demonstrated by our molecular simulations. One of our main purpose of studying clay nano-properties ais to know the fundamental nano-mechanical characteristics of clays, and to apply these properties to predict long term behavior of clay-based materials, such as engineering barriers for radioactive waste disposal. For this purpose, unified nano-micro-macro mechanical approaches should be established (Ichikawa, et al. (1999)“Unified molecular dynamics and homogenization analysis for bentonite behavior: Current results and future possibilities. Engineering Geology, 54, 21-31. Choi, et al. (2008) Transport phenomena in kaolinite clay: Molecular simulation, homogenization analysis. Int.J.Numer. Analy. Meth. Geomech., DOI:10.1002/nag.744.)

Kawamura, K.

2009-12-01

67

Paleoenvironmental significance of clay mineral assemblages in the southeastern Arabian Sea during last 30 kyr  

NASA Astrophysics Data System (ADS)

A gravity core SK-221 recovered from the southeastern Arabian Sea near Laccadive-Chagos Ridge was examined to identify the sources of detrital clay minerals and to decipher paleoenvironmental changes for the last 30 kyr. The clay mineral assemblages predominantly consist of illite, kaolinite and chlorite with small amounts of smectite. Quartz, feldspar and occasionally gibbsite are the clay-sized non-clay minerals present in the examined section. The detrital clay minerals primarily originated from the hinterland and were supplied to the present site by the numerous small rivers draining western India during preglacial and Holocene periods, and partly by the strong reworking of Indian continental shelf during glacial period. The low values of humidity proxies (kaolinite content, kaolinite to illite and smectite to illite ratios) and better illite crystallinity indicate relatively weak summer monsoon condition that resulted in reduced chemical weathering during glacial period, which was interrupted by a discrete event of winter monsoon intensification at ~20-17 ka. The increased kaolinite content, higher values of humidity indices and poorer illite crystallinity reflect high humidity that resulted in strong hydrolysis activity during the preglacial and Holocene periods. The increased CaCO3 during above periods also indicates less terrigenous dilution and intensified southwest monsoon-led upwelling which result in higher surface biogenic productivity. The characteristic clay mineral associations broadly suggest dry to semi-drier conditions during Heinrich Events H1, H2, and H3 and also during Younger Dryas. The low values of biogenic carbonate and organic carbon also indicate low productivity associated with weak summer monsoons during Heinrich Events. Abrupt increased humidity was recorded at 15-12.7 ka (Bølling/Allerød Event) sandwiched between two lows of Heinrich Events. Cycles of millennial timescale variations 2300, 1800, 1300 and 1000 yr have been observed from the clay mineralogical data. All the cycles observed in the monsoonal climate appear to be part of global oscillations.

Das, Siddhartha Sankar; Rai, Ajai K.; Akaram, Vaseem; Verma, Dhananjai; Pandey, A. C.; Dutta, Koushik; Prasad, G. V. Ravi

2013-02-01

68

Alkali Cation Selectivity and Fixation by Clay Minerals  

Microsoft Academic Search

Two variables must be considered when calculating exchange free energies (AG~ for 2:1 clays: (1) anionic field strength, as expressed by equivalent anionic radius (ra), and (2) interlayer water content, as expressed by interlayer molality. For smectites that are in a state of high hydration, interlayer molality is determined by the cations undergoing exchange. Thus AG~ for an exchanging cation

Dennis D. Eberl

1980-01-01

69

Structure of a seafloor hydrothermal system in volcanic sediment: distribution of hydrothermal clay minerals, at the Iheya North Knoll, Okinawa Trough  

NASA Astrophysics Data System (ADS)

Detailed investigation of clay minerals in hydrothermal fields provides fundamental information for understanding the physical and geochemical conditions within a hydrothermal system. Moreover, stable isotope geochemistry of clay minerals provides constraints on formation temperature. We investigated the distribution of clay minerals by XRD and TEM-EDS in a seafloor hydrothermal field at Iheya North Knoll in the Okinawa Trough, using cored sediment obtained from the Integrated Ocean Drilling Program (IODP) Expedition 331. The chemical composition and isotope values of the representative clay minerals were analyzed to obtain information on the hydrothermal system beneath the seafloor. Vertically, two different clay mineral facies are present. The boundary between the facies was identified at 6 mbsf (meters below the seafloor) at Site C0013 (100 m east of hydrothermal mound) and at 23 mbsf at Site C0014 (450 m east of the mound). In the lower facies (6 - 28 mbsf and 45 mbsf at Site C0013, 23 - 114 mbsf at Site C0014), Mg-chlorite and/or Mg-chlorite-smectite mixed layer minerals are dominant. They are associated with sericite in deeper parts (45 mbsf at Site C0013 and 38 - 114 mbsf at Site C0014). The ?18O values of the clays range from +1.5 to +4.7 ‰ (VSMOW) and the formation temperatures of the Mg-chlorite are estimated to be 230 - 300 °C, assuming a value from 0 to +1.5 ‰ for ?18Owater. The original sediment in the Iheya North Knoll is considered to have been volcanic of felsic chemical composition, so alteration to Mg-rich chlorite would require supply of substantial amount of Mg. Abundant formation of Mg-chlorite is attributed to mixing of hydrothermal fluid and seawater. In the upper facies at both sites, Al-rich clay minerals (kaolinite and montmorillonite) dominate. The ?18O values of clays range between +9.6 and +13.3 ‰ and formation temperatures are estimated to range between 120 - 160 °C. As kaolinite formation is favorable under acidic conditions, the kaolinite may be related to the vapor phase component enriched in CO2 and H2S, which would be generated by boiling of the hydrothermal fluid below the seafloor. In summary, occurrence of different facies of hydrothermal clay minerals reflects substantial variation in both temperature and chemical conditions between the upper and lower sediment layer. This difference may be related to discrete fluid flow within these sediment layers.

Miyoshi, Y.; Ishibashi, J.; Faure, K.; Uehara, S.

2012-12-01

70

Toxicological evaluation and metal bioavailability in pregnant rats following exposure to clay minerals in the diet.  

PubMed

Silicate clays are frequently added to animal feeds to bind and reduce the bioavailability of mycotoxins in the gastrointestinal tract. However, the bioavailability of trace metals in these clay feed additives has not been thoroughly investigated. Clays that act nonselectively may interact with nutrients, minerals, and other feedborne chemicals to pose significant hidden risks. In this study, a calcium montmorillonite clay (Novasil Plus, NSP) commonly used as an enterosorbent for aflatoxins and a sodium montmorillonite clay (Swy-2) (Source Clay Minerals Repository, Columbia, MO) were examined. Clays were supplemented in the balanced diet of Sprague-Dawley rats during pregnancy at a level of 2% (w/w). Evaluations of toxicity were performed on gestation d 16 and included maternal body weights, maternal feed intakes, litter weights, and embryonic resorptions. Liver, kidneys, tibia, brain, uterus, pooled placentas, and pooled embryonic mass were collected and weighed. Tissues were lyophilized and neutron activation analysis (NAA) was performed. Elements considered by NAA included Al, Ba, Br, Ca, Ce, Co, Cr, Cs, Cu, Dy, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Ni, Rb, S, Sb, Sc, Se, Sm, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, Yb, Zn, and Zr. Inductively coupled plasma-mass spectroscopy further confirmed that Al was below detection limits (<0.5 ppm) in the brain. Animals supplemented with either NSP or Swy-2 were similar to controls with respect to toxicity evaluations and metal analysis, with the exception of decreased brain Rb following clay supplementation. Overall, the results of this study suggest that neither NSP nor Swy-2, at relatively high dietary concentrations, influences mineral uptake or utilization in the pregnant rat. PMID:15205041

Wiles, Melinda; Huebner, Henry; Afriyie-Gyawu, Evans; Taylor, Robert; Bratton, Gerald; Phillips, Timothy

2004-06-11

71

Reduction and immobilization of hexavalent chromium by microbially reduced Fe-bearing clay minerals  

NASA Astrophysics Data System (ADS)

Hexavalent chromium (Cr6+) is a major contaminant in the environment. As a redox-sensitive element, the fate and toxicity of chromium is controlled by reduction-oxidation (redox) reactions. Previous research has shown the ability of structural Fe(II) in naturally present and chemically reduced clay minerals to reduce Cr6+ to Cr(III) as a way of immobilization and detoxification. However, it is still poorly known whether or not structural Fe(II) in biologically reduced clay minerals exhibits a similar reactivity and if so, what the kinetics and mechanisms of Cr6+ reduction are. The objective of this study was to determine the kinetics and possible mechanisms of Cr6+ reduction by structural Fe(II) in microbially reduced clay minerals and the nature of reduced Cr(III). Structural Fe(III) in nontronite (NAu-2), montmorillonite (SWy-2), chlorite (CCa-2), and clay-rich sediments from the Ringold Formation of the Hanford site of Washington State, USA was first bioreduced to Fe(II) by an iron-reducing bacterium Geobacter sulfurreducens with acetate as the sole electron donor and anthraquinone-2,6-disulfonate (AQDS) as electron shuttle in synthetic groundwater (pH 7). Biogenic Fe(II) was then used to reduce aqueous Cr6+ at three different temperatures, 10, 20, and 30 °C, in order to determine the temperature dependence of the redox reaction between Cr6+ and clay-Fe(II). The results showed that nontronite and montmorillonite were most effective in reducing aqueous Cr6+ at all three temperatures. In contrast, most Fe(II) in chlorite was not reactive towards Cr6+ reduction at 10 °C, though at 30 °C there was some reduction. For all the clay minerals, the ratio of total Fe(II) oxidized to Cr6+ reduced was close to the expected stoichiometric value of 3. Characterization of the Cr-clay reaction product with scanning electron microscopy with focused ion beam and transmission electron microscopy with electron energy loss spectroscopy revealed that reduced chromium was possibly in the form of sub-nanometer Cr2O3 in association with residual clay minerals as micro-aggregates. This textural association was expected to minimize the chance of Cr(III) reoxidation upon exposure to oxidants. These results are important for our understanding of how various clay minerals may be used to reductively immobilize the heavy metal contaminant Cr in the environment.

Bishop, Michael E.; Glasser, Paul; Dong, Hailiang; Arey, Bruce; Kovarik, Libor

2014-05-01

72

Crystallization and textural porosity of synthetic clay minerals.  

SciTech Connect

The crystallization of synthetic layered magnesium silicate hectorite clays from both silica sol and organosilane sources is compared. For the silica sol-derived clays, a templating method is employed wherein organic or polymeric molecules are included during clay crystallization that are then removed from the composites via calcination. The mechanism of silane-derived hectorite formation is followed by XRD, TGA, 29Si MAS NMR, and small angle X-ray scattering (SAXS), and results are compared to those obtained for the sol-derived hectorite. The mechanism appears to be similar but the rate is approximately doubled when the silane is used rather than silica sol. Analytical transmission electron microscopy (TEM) is exploited to glean structural morphology information towards resolving the nature of the resulting pore network structures. Results are compared with nitrogen adsorption-desorption isotherm behavior; dominant hysteresis loops are present in the type IV isotherms. Pore size distributions based on both the adsorption and desorption isotherms are compared. Small angle neutron scattering (SANS) experiments reveal that the average particle size increases as synthetic laponite < sol-derived hectorite < silane-derived hectorite < natural hectorite. Contrast matching SANS studies in aqueous and organic solvents are carried out to extract information about pore accessibility.

Carrado, K. A.; Csencsits, R.; Thiyagarajan, P.; Seifert, S.; Macha, S. M.; Harwood, J.; Univ. of Illinois at Chicago; IIT

2002-12-01

73

Rare earth distributions in clay minerals and in the clay-sized fraction of the Lower Permian Havensville and Eskridge shales of Kansas and Oklahoma  

Microsoft Academic Search

The REE (rare earth element) content of a wide variety of clay mineral groups have been analyzed using radiochemical neutron activation and have been found to be quite variable in absolute REE content (range of REE = 5.4-1732) and less variable in relative REE content (range of chondritenormalized La \\/ Lu = 0.9-16.5). The variable REE content of the clay

Robert L. Cullers; Sambhudas Chaudhuri; Bill Arnold; Moon Lee; Carlton W. Wolf Jr.

1975-01-01

74

Potassium and magnesium in clay minerals of some Brazilian soils as indicated by A sequential extraction procedure  

Microsoft Academic Search

The total contents of potassium (K) and magnesium (Mg) in selected Brazilian soils (Oxisols, Ultisols, Inceptsols, and Alfisols) developed from different parent materials were investigated to estimate the contribution of clay minerals to K and Mg reserves. Total K and Mg contents in the Na-saturated clay were determined by HF total digestion. The contribution of each mineral species to the

V. F. Melo; C. E. G. R. Schaefer; R. F. Novais; B. Singh; M. P. F. Fontes

2002-01-01

75

Chemistry and mineralogy of clay minerals in Asian and Saharan dusts and the implications for iron availability  

NASA Astrophysics Data System (ADS)

Mineral dust supplied to remote ocean regions stimulates phytoplankton growth through delivery of micronutrients, notably iron (Fe). Although attention is usually paid to Fe (hydr)oxides as major sources of available Fe, Fe-bearing clay minerals are typically the dominant phase in mineral dust. The mineralogy and chemistry of clay minerals in dust particles, however, are largely unknown. We conducted microscopic identification and chemical analysis of the clay minerals in Asian and Saharan dust particles. Cross-sectional slices of dust particles were prepared by focused ion beam (FIB) techniques and analyzed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDXS). TEM images of FIB slices revealed that clay minerals occurred as either nano-thin platelets or relatively thick plates. The nano-thin platelets included illite, smectite, illite-smectite mixed layers and their nanoscale mixtures (illite-smectite series clay minerals, ISCMs) which could not be resolved with an electron microbeam. EDXS chemical analysis of the clay mineral grains revealed that the average Fe content was 5.8% in nano-thin ISCM platelets assuming 14% H2O, while the Fe content of illite and chlorite was 2.8 and 14.8%, respectively. In addition, TEM and EDXS analyses were performed on clay mineral grains dispersed and loaded on microgrids. The average Fe content of clay mineral grains was 6.7 and 5.4% in Asian and Saharan dusts, respectively. A comparative X-ray diffraction analysis of bulk dusts showed that Saharan dust was more enriched in clay minerals than in Asian dust, while Asian dust was more enriched in chlorite. The average Fe / Si, Al / Si and Fe / Al molar ratios of the clay minerals, compared to previously reported chemistries of mineral dusts and leached solutions, indicated that dissolved Fe originated from clay minerals. Clay minerals, in particular nanocrystalline ISCMs and Fe-rich chlorite are important sources of available Fe in remote marine ecosystems. Further detailed analyses of the mineralogy and chemistry of clay minerals in global aerosols are required to determine the inputs of Fe available to surface ocean microbial communities.

Jeong, G. Y.; Achterberg, E. P.

2014-06-01

76

Clay minerals in recent sediments of the World Ocean and their relation to types of lithogenesis  

Microsoft Academic Search

Problem of the distribution of clay minerals in water areas of the World Ocean and their relation to different (humid, arid,\\u000a and volcanosedimentary) types of lithogenesis is considered. It is shown that layer silicates can be used as index minerals\\u000a for distinguishing types of lithogenesis under conditions of marine sedimentation. Humid marine lithogenesis is represented\\u000a by sediments of the White,

M. A. Rateev; T. A. Sadchikova; V. P. Shabrova

2008-01-01

77

Networking and rheology of concentrated clay suspensions "matured" in mineral medicinal water.  

PubMed

This work studied the influence of "maturation" conditions (time and agitation) on aggregation states, gel structure and rheological behaviour of a special kind of pharmaceutical semisolid products made of concentrated clay suspensions in mineral medicinal water. Maturation of the samples was carried out in distilled and sulphated mineral medicinal water, both in static conditions (without agitation) and with manual stirring once a week, during a maximum period of three months. At the measured pH interval (7.5-8.0), three-dimensional band-type networks resulting from face/face contacts were predominant in the laminar (disc-like) clay suspensions, whereas the fibrous (rod-like) particles formed micro-aggregates by van der Waals attractions. The high concentration of solids in the studied systems greatly determined their behaviour. Rod-like sepiolite particles tend to align the major axis in aggregates promoted by low shearing maturation, whereas aggregates of disc-like smectite particles did not have a preferential orientation and their complete swelling required long maturation time, being independent of stirring. Maturation of both kinds of suspensions resulted in improved rheological properties. Laminar clay suspensions became more structured with time, independently from static or dynamic maturation conditions, whereas for fibrous clay periodic agitation was also required. Rheological properties of the studied systems have been related to aggregation states and networking mechanisms, depending on the type of clay minerals constituents. Physical stability of the suspensions was not impaired by the specific composition of the Graena medicinal water. PMID:23764616

Aguzzi, Carola; Sánchez-Espejo, Rita; Cerezo, Pilar; Machado, José; Bonferoni, Cristina; Rossi, Silvia; Salcedo, Inmaculada; Viseras, César

2013-09-10

78

Weathering Effects on the Structures of Mica-Type Clay Minerals.  

National Technical Information Service (NTIS)

Mica-type clay minerals are subjected to an intensive weathering process in the basin of the Willard Reservoir, north of Ogden, on the playa margin of Great Salt Lake. Weathering attacks the interlayer region of the layer lattice silicates most intensivel...

N. Guven P. F. Kerr

1965-01-01

79

Clay minerals in nonaqueous extraction of bitumen from Alberta oil sands  

Microsoft Academic Search

Although not used commercially, a nonaqueous extraction process is of great interest to extract bitumen from the Alberta oil sands due to its potential advantages, such as high bitumen recovery even from low grade oil sand ores and the elimination of slow settling, sludge tailings ponds with stable suspensions. While clay minerals have been characterized in water-based bitumen extraction from

Ali Hooshiar; Peter Uhlik; Douglas G. Ivey; Qi Liu; Thomas H. Etsell

80

Estimate of clay minerals amounts from XRD pattern modeling: The Arquant model  

Microsoft Academic Search

This work presents an XRD pattern model applied to the quantification of clay minerals in the <2?m fraction. The model is based on a linear combination of patterns previously simulated with specific codes. The modeling procedure is especially adapted to the oriented deposits performed from a suspension although it can also apply to the oriented pastes. The estimate of mica-like

Philippe Blanc; Olivier Legendre; Eric C. Gaucher

2007-01-01

81

Clay minerals and their beneficial effects upon human health. A review  

Microsoft Academic Search

This work examines the beneficial effects for human health of clay minerals, describing their use in pharmaceutical formulations, spas and aesthetic medicine. Their therapeutic action as active principles in pharmaceutical formulations orally administered (gastrointestinal protectors, laxatives, antidiarrhoeaics) or for topical applications (dermatological protectors and cosmetics) is described. Their use as excipients and their influence in the bioavailability of the organic

M. Isabel Carretero

2002-01-01

82

Modern and late Quaternary clay mineral distribution in the area of the SE Mediterranean Sea  

Microsoft Academic Search

The present-day clay mineral distribution in the southeastern Levantine Sea and its borderlands reveals a complex pattern of different sources and distribution paths. Smectite dominates the suspended load of the Nile River and of rivers in the Near East. Illite sources are dust-bearing winds from the Sahara and southwestern Europe. Kaolinite is prevalent in rivers of the Sinai, in Egyptian

Yvonne Hamann; Werner Ehrmann; Gerhard Schmiedl; Tanja Kuhnt

2009-01-01

83

FINAL REPORT. MODELING OF CATION BINDING IN HYDRATED 2:1 CLAY MINERALS  

EPA Science Inventory

Hydrated 2:1 clay minerals are high surface area, layered silicates that play a unique role in determining the fate of radionuclides in the environment. This project consisted of developing and implementing computer simulation methods for molecular characterization of the swellin...

84

Is the geological concept of clay minerals appropriate for soil science? A literature-based and philosophical analysis  

NASA Astrophysics Data System (ADS)

Data in the literature for soils that are dominated by each of the main types of clay minerals were examined and compared with those for reference clay minerals of the same types to determine the extent to which the nature and properties of clay-size minerals in soils could be explained by those of clay minerals with the same name from non-soil, ‘geological’ environments. Published information on soils from Australia, New Zealand and Iran was sourced for this study. The clay fractions of each of the soils are dominated by either one of the common phyllosilicates: kaolinite, halloysite, illite/mica, vermiculite, smectite, and palygorskite, or by the nanocrystalline mineral, allophane. Data for samples of kaolinite that had been extracted from soils from several countries (Australia, Thailand, Indonesia and Brazil) and purified before characterization have also been examined. In soils, each dominant clay mineral is generally associated with other materials, including iron oxides, other phyllosilicates and/or nanocrystalline minerals and organic matter. As the most studied example of an extracted phyllosilicate, kaolinite shows a wide range of properties in different soils, but a narrower range of properties within a particular locality. However, almost all of the soil kaolinites studied have larger specific surface areas and higher cation exchange capacities than reference kaolinites. The literature also reveals that, among phyllosilicates in soils, illites have a wide range of potassium contents, expandable minerals (vermiculites and smectites) may be interlayered by hydroxy-Al species particularly, and smectitic layers often occur interstratified with other layers, including those of illite, kaolinite and halloysite. The variability of soil phyllosilicates and their common association with other, often poorly crystallized but highly reactive minerals and compounds can be explained by their formation in the highly heterogeneous and dynamic soil environment. Phyllosilicates from non-soil or geological sources are poor models for the representation of secondary clay-size minerals in soils. In philosophical terms, the reduction of soil mineralogy to mineralogy as it is practiced within geology is misleading because of the differences between the minerals formed in soil and geological environments. In other words, clay minerals as they are defined as mineralogical entities for geology are of a different ‘kind’ to clay minerals in soils and cannot serve as ‘types’ or ‘stereotypes’ to enable explanation of the contribution of secondary clay-size minerals to soil properties or behavior. It is more useful to view clay minerals in soils as secondary inorganic compounds of clay-size than to follow their definition for non-soil purposes as plastic phyllosilicate minerals.

Churchman, G. Jock

85

Clay minerals in basin of Mexico lacustrine sediments and their influence on ion mobility in groundwater  

NASA Astrophysics Data System (ADS)

Semiconfined aquifers used as the principal water supply within the Basin of Mexico are overlain by lacustrine deposits that provide a degree of protection from contamination associated with metropolitan Mexico City. Solute transport behavior and the nature of chemical interactions with mineral components in these sediments is poorly understood. The objectives of this paper were to identify the clay mineral phases of the lacustrine sediments and to determine the significance of the exchange properties of the day minerals on contaminant transport processes. Samples obtained from two cores were separated into sand, silt, and clay-size fractions. The clay-size fraction was analyzed by X-ray diffraction and Fourier transform infrared spectroscopy and for specific surface area and pH-dependent cation and anion exchange capacity. The clay-sized fraction averaged 56% of the sediment. Analyses indicated that the clay was predominantly composed of a Si-rich allophane with approximately 30% montmorillonite. Halloysite was also present to a depth of about 1.5 m, but was absent deeper in the sediment. Kaolinite and illite, reported in previous studies, and imogolite were not found in the samples. Solute transport in the sediment was modeled to demonstrate the impact of exchange properties imparted by the allophane compared to other possible clay mineral assemblages. The predominance of allophane in the Basin of Mexico sediments is responsible for many of the fundamental characteristics of the material including: high porosity (0.8-0.9), high water content (200-400%), and an extremely high and pH-dependent cation exchange capacity. The pH of the pore water within the lacustrine sediments of the Basin of Mexico is typically between 6.5 and 12. Measured cation exchange values ranged from ? 450 meq kg -1 at pH 6.5 to ? 650 meq kg -1 at pH 12 which could produce variable cation mobility in the semiconfining aquitard. The simulations illustrated that allophane is very effective for retarding the leaching of cationic metals compared to other possible clay mineral suites, particularly at high pH values. Simulation of long-term infiltration indicated that trace metals will become concentrated in the clay matrix adjacent to fracture faces in the sediment near ground surface. As such, the aquitard behaves as an efficient barrier to the infiltration of cationic metals into the underlying aquifer.

Warren, C. J.; Rudolph, D. L.

1997-09-01

86

Influence of swelling on reaction efficiency in intercalated clay minerals  

SciTech Connect

A lattice model is designed to determine the extent which the efficiency of reaction between a fixed target molecule and a diffusing coreactant is affected when the interlamellar space separating the atomic layers defining a smectite-type clay is expanded (or swollen). The authors consider partially ordered layer lattices of hexagonal symmetry, and for the case where the target molecule is positioned in the basal lattice at the centrosymmetric site exact numerical solution of the underlying stochastic problem shows that in the limit of large planar arrays the reaction efficiency (as calibrated by the mean walklength (n) of the diffusing coreactant) decreases by a factor of approx. 1.7 for a (stacked) two-layer hexagonal structure and by approx. 2.4 for a three-layer structure. The role of initial conditions and system size is explored, and the exponential character of the decay is quantified.

Politowicz, P.A.; Kozak, J.J.

1988-10-20

87

Clay mineral formation on Mars: Chemical constraints and possible contribution of basalt out-gassing  

NASA Astrophysics Data System (ADS)

We focus on processes possibly occurring on Mars that could affect sufficiently large volumes of rocks to be detected by remote sensing techniques. When compared with the chemical modelling of water-rock interactions, the petrographic and mineralogical characteristics of clay deposited in the prismatic joints of a lava flow from the Parana basin (Brazil) suggest that the clay fraction of lava flows may be formed at least partly during an early post-magmatic stage associated with the degassing of acid volatiles. In view of the literature concerning other contexts, such as meteorites or experimental syntheses, we conclude that the crystallization of anhydrous mafic minerals and the formation of clay mineral are not systematically mutually exclusive phenomena. While clay formation is generally related to chemical reaction pathways, it is not necessarily due to the alteration of pre-existing silicates. Such post-magmatic reactions, even if they are likely to represent only a minor contribution to Martian clay formation limited to early Noachian times, require much lower amounts of water compared to conventional hydrothermal alteration or weathering systems. The products of these reactions can be detected over large surface areas, as in the case of the Mars sites, thus allowing us to envisage a greater diversity of paleogeographic scenarios for Early Mars.

Berger, Gilles; Meunier, Alain; Beaufort, Daniel

2014-05-01

88

Formation of clay minerals and exhumation of lower-crustal rocks at Atlantis Massif, Mid-Atlantic Ridge  

NASA Astrophysics Data System (ADS)

Low-temperature alteration products in gabbros from the ocean floor have significant implications for incipient processes of seawater-rock interaction and exhumation tectonics of the lower-crustal rocks. In this paper we report mode of occurrence and mineralogical characteristics of clay minerals in gabbroic rocks recovered from Integrated Ocean Drilling Program (IODP) Hole U1309D at an oceanic core complex, Atlantis Massif, Mid-Atlantic Ridge at 30°N. The clay minerals were identified by optical microscope, electron microprobe, Raman spectrometer, and transmission electron microscope as mainly composed of mixed-layer saponite-talc, saponite, and vermiculite. They are characteristically rich in iron that is significantly oxidized and distributed into the tetrahedral site, suggesting a relatively high-temperature condition for oxidation. They are restricted to domains near the contacts between olivine and talc or form pseudomorphs after olivine near microcracks filled with zeolite or clay minerals. These facts suggest the infiltration of oxidative seawater and reactions to variable fluid/rock ratios at variable temperatures. Close association of vermiculite with microcracks radiated from serpentinized olivine suggests that the deep infiltration of seawater at an off-axis region was caused by fracturing resulting from serpentinization and enhanced by relatively abundant olivine-rich lithology at Atlantis Massif. Compared with gabbroic rocks of an oceanic core complex at ultraslow-spreading ridge (ODP Hole 735B), those of Atlantis Massif substantially lack mixed-layer smectite-chlorite. Mixed-layer smectite-chlorite is a product of prehnite-actinolite to greenschist facies alteration and looks to preserve a record of ambient thermal structure through which the massif passed on rising to a shallow level. The absence of pervasive formation of mixed-layer smectite-chlorite under relatively reducing conditions suggests low permeability and/or limited fluid-rock reactions on the way to shallow levels. From the observation and consideration of the characteristics of clay minerals, sequence and distribution of static alteration related to fracturing, original lithology, and tectonic settings of the oceanic core complexes, we conclude that Atlantis Massif was more rapidly exhumed to the oxidative subseafloor environment than Atlantis Bank. The difference of exhumation rate possibly reflected either the disparity in spreading rate between the whole ridge systems or regional variation of exhumation tectonics between the two oceanic core complexes.

Nozaka, Toshio; Fryer, Patricia; Andreani, Muriel

2008-11-01

89

Bioremediating oil spills in nutrient poor ocean waters using fertilized clay mineral flakes: some experimental constraints.  

PubMed

Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity. PMID:23864952

Warr, Laurence N; Friese, André; Schwarz, Florian; Schauer, Frieder; Portier, Ralph J; Basirico, Laura M; Olson, Gregory M

2013-01-01

90

Leaching of clay minerals in a limestone environment  

USGS Publications Warehouse

Water saturated with CO2 at about 25??C was percolated through mixed beds of limestone or marble fragments and montmorillonite, "illite" and kaolinite in polyethylene tubes for six and fortyfive complete runs. The leachates were analysed for SiO2, A12O3 and Fe2O3, but only SiO2 was found. The minerals lost SiO2 in this order: montmorillonite > kaolinite > "illite". The differential removal of SiO2 during the short period of these experiments suggests a mechanism for the accumulation of bauxite deposits associated with limestones. ?? 1959.

Carroll, D.; Starkey, H. C.

1959-01-01

91

The interactions of humic compounds with electrolytes and three clay minerals under simulated estuarine conditions  

NASA Astrophysics Data System (ADS)

Laboratory studies of the reactions between dissolved humic substances and dissolved sodium, magnesium, calcium, iron and aluminium are described together with studies of the adsorption of humic substances onto the clay minerals illite, kaolinite and montmorillonite under simulated estuarine conditions. It is demonstrated that only minor quantities of humic substances are precipitated in the presence of Na, Mg and Ca up to ca. 1.5 times their seawater concentrations. The total amount of humic substance precipitated is dependent on the cation present and increases in the order Naclay minerals depend not only on the nature of the compounds or minerals but also on the salinity of the reaction medium. There is evidence that interactions with clay minerals can lead to fractionation of different humic components.

Preston, M. R.; Riley, J. P.

1982-05-01

92

Reactive Clay Minerals in a land use sequence of disturbed soils of the Belgian Loam Belt  

NASA Astrophysics Data System (ADS)

Clay minerals play a key role in soil biogeochemistry. They can stabilize organic matter, improve water storage, increase cation exchange capacity of the soil (CEC) and lower nutrient leaching. Phytoliths - the biogenic silica bodies (BSi) deposited in cell walls of plants - are important Si pools in soil horizons due to their higher solubility compared to minerals. They provide the source of Si for plant uptake in short time scales, as litter dissolves within soils. In a recent study, we analyzed the BSi pool differences across a set of different land uses (forests, pastures, croplands) in 6 long-term disturbed (multiple centuries) soil sites in the Belgium Loam Belt. Results from a simultaneous chemical extraction in 0.5M NaOH of Si and Al, showed that soils were depleted in the BSi pool while showing high levels of reactive secondary clay minerals, mainly in the deeper horizons and especially in the forests and the croplands. During the extraction, clays were similar in reactivity to the biogenic pool of phytoliths. In order to study the kinetics in a more natural environment, batch dissolution experiments were conducted. Samples from different soil depths for each land use site (0.5 g) were mixed with 0.5 L of demineralised water modified to pH 4, 7 and 10. Subsamples of 2 ml were taken during 3 months. In the end of the period, results for pH 7 showed that in the pastures, where reactive clays were almost absent, the ratio Si/RSi (defined as the Si concentration in the end of the batch experiment divided by the reactive silica extracted from the soil with the alkaline extraction) was lower than 0.005%. The same ratio was higher in the mineral horizons of forests (Si/RSi>0.01%) and croplands (0.005% < Si/RSi <0.01%) where clay minerals were the dominant fraction. These preliminary results highlight the clay minerals' strong potential for Si mobilization. More attention should be paid to this important fraction as it can contribute strongly to Si availability, in close competition with phytoliths and other soluble amorphous Si forms, strongly interfering with frequently applied methods to quantify biogenic Si in soils.

Barao, Lucia; Vandevenne, Floor; Ronchi, Benedicta; Meire, Patrick; Govers, Gerard; Struyf, Eric

2014-05-01

93

Clay mineral continental amplifier for marine carbon sequestration in a greenhouse ocean  

PubMed Central

The majority of carbon sequestration at the Earth’s surface occurs in marine continental margin settings within fine-grained sediments whose mineral properties are a function of continental climatic conditions. We report very high mineral surface area (MSA) values of 300 and 570 m2 g in Late Cretaceous black shales from Ocean Drilling Program site 959 of the Deep Ivorian Basin that vary on subcentennial time scales corresponding with abrupt increases from approximately 3 to approximately 18% total organic carbon (TOC). The observed MSA changes with TOC across multiple scales of variability and on a sample-by-sample basis (centimeter scale), provides a rigorous test of a hypothesized influence on organic carbon burial by detrital clay mineral controlled MSA. Changes in TOC also correspond with geochemical and sedimentological evidence for water column anoxia. Bioturbated intervals show a lower organic carbon loading on mineral surface area of 0.1 mg-OC m-2 when compared to 0.4 mg-OC m-2 for laminated and sulfidic sediments. Although either anoxia or mineral surface protection may be capable of producing TOC of < 5%, when brought together they produced the very high TOC (10–18%) apparent in these sediments. This nonlinear response in carbon burial resulted from minor precession-driven changes of continental climate influencing clay mineral properties and runoff from the African continent. This study identifies a previously unrecognized land–sea connection among continental weathering, clay mineral production, and anoxia and a nonlinear effect on marine carbon sequestration during the Coniacian-Santonian Oceanic Anoxic Event 3 in the tropical eastern Atlantic.

Kennedy, Martin J.; Wagner, Thomas

2011-01-01

94

Clay-mineral assemblages from some levels of K-118 drill core of Maha Sarakham evaporites, northeastern Thailand  

NASA Astrophysics Data System (ADS)

Clay-mineral assemblages in Middle Clastic, Middle Salt, Lower Clastic, Potash Zone, and Lower Salt, totalling 13 samples from K-118 drill core, in the Maha Sarakham Formation, Khorat Basin, northeastern Thailand were studied. The clay-size particles were separated from the water-soluble salt by water leaching. Then the samples were leached again in the EDTA solution and separated into clay-size particles by using the timing sedimentation. The EDTA-clay residues were divided and analyzed by using the XRD and XRF method. The XRD peaks show that the major-clay minerals are chlorite, illite, and mixed-layer corrensite including traces of rectorite? and paragonite? The other clay-size particles are quartz and potassium feldspar. The XRF results indicate Mg-rich values and moderate Mg?Al atom ratio values in those clay minerals. The variable Fe, Na, and K contents in the clay-mineral assemblages can explain the environment of deposition compared to the positions of the samples from the core. Hypothetically, mineralogy and the chemistry of the residual assemblages strongly indicate that severe alteration and Mg-enrichment of normal clay detritus occurred in the evaporite environment through brine-sediment interaction. The various Mg-enrichment varies along the various members reflecting whether sedimentation is near or far from the hypersaline brine.

Suwanich, Parkorn

95

Influence of swelling on reaction efficiency in intercalated clay minerals. 2. Pillared clays  

SciTech Connect

Methods for intercalating thermally stable, polynuclear hydroxy metal cations and/or metal cluster cations in smectite clays have been developed in recent years as a means of keeping separate the silicate layers in the absence of a swelling solvent. Since the pillaring cations are space filling, the interlamellar reaction space will be broken up into an interconnected set of channels through which a diffusing species can migrate. In this paper, a lattice model is designed to determine how different spatial distributions of pillaring agents and different interlamellar spacings can influence the efficiency of reaction between a fixed target molecule and a diffusing coreactant. The authors study two regular distributions of pillaring cations and calculate the mean reaction time (as calibrated by the mean walklength ) of the diffusing coreactant as a function of the separation between silicate layers. All other factors being held constant, they find a significant increase in the reaction efficiency with increase in the number of channels available to the coreactant. They also find that for each distribution there is a decrease in reaction efficiency as one increases the interlayer spacing, with the surprising result that for large arrays the addition of one or two layers above the basal plane (where the target molecule is anchored at the centrosymmetric site) leads to essentially the same relative changes in the reaction efficiency regardless of the spatial distribution considered.

Politowicz, P.A.; San Leung, L.B.; Kozak, J.J. (Australian National Univ., Canberra)

1989-01-26

96

Hydrogels in aqueous phases of polyvinylalcohol (PVA), surfactants and clay minerals  

Microsoft Academic Search

Aqueous solutions of synthetic clay minerals have been studied in the presence of surfactants and water-soluble polyvinylalcohol (PVA). The PVAs (PVA 1, PVA 2) had a molecular weight of about 10 5 Dalton and a degree of hydrolysis of 82%. The PVA-samples were surface active and lowered the surface tension to 43 mN\\/m. As a consequence of their amphiphilic nature the

Jing Liu; H. Hoffmann

2004-01-01

97

Adsorption and binding of AmpliTaq® DNA polymerase on the clay minerals, montmorillonite and kaolinite  

Microsoft Academic Search

Adsorption at equilibrium and binding of AmpliTaq® DNA polymerase (TDP) on clay minerals, two montmorillonites (W–M and Ap–M) and a kaolinite (K), were studied. Equilibrium adsorption isotherms were of the L type, and a plateau was reached with Ap–M and K, whereas no plateau was obtained with W–M. Adsorption of TDP was most rapid on W–M, maximal at pH 6

C Vettori; L Calamai; M Yoder; G Stotzky; E Gallori

1999-01-01

98

Characterization of oil sands mineral components and clay-organic complexes  

SciTech Connect

Differences in oil sands processability and extraction yields can be dependent upon many factors including the composition of the mineral components and the organic complexes that are associated with certain minerals. These mineral-organic associations help provide the bridge which leads to carry over of bitumen with the tailing as well as carry over of water and mineral matter with the product. The nature of the organic component of clay-organic complexes extracted from various streams in an oil sands recovery process is discussed in relation to the stability of both water-in-oil and oil-in-water emulsions formed. These samples have been studied with nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) as well as with other techniques such as interfacial tension measurements.

Axelson, D.E.; Mikula, R.J.; Potoczny, Z.M. (CRL, Fuel Processing Lab., CANMET, Energy, Mines and Resources Canada, P.O. Bag 1280, Devon, Alberta, T0C 1E0 (CA))

1989-01-01

99

Removal of methylene blue from aqueous solution by fibrous clay minerals.  

PubMed

Kinetics and equilibrium processes of the methylene blue (MB) retention from aqueous solution by a mixture of fibrous clay minerals, which was isolated from a naturally occurring clay, were investigated. For these purposes, the effects of contact time, initial adsorbate concentration, adsorbent content, pH and ionic strength were determined. The results show that the MB retention obeys a pseudo-first order equation and the process is a diffusion controlled solid-state reaction. Moreover, the isotherm data fitted the Langmuir equation and the MB binding process became more energetic with the increase of the adsorbent concentration. In addition, the augmentation of the clay content or the initial MB concentration reduced the adsorption capacity, presumably because of the clay particles microaggregation and/or the occurrence of MB deriving species. On the other hand, it is observed that the MB uptake limit is reduced in low acid pH, particularly below the PZC, as well as in ionic strengthen solutions. These facts are linked to the silanol group protonation and to the reduction of the electrostatic forces induced by the clay particles, respectively. PMID:16388900

Hajjaji, M; Alami, A; El Bouadili, A

2006-07-31

100

Significance of saturation index of certain clay minerals in shallow coastal groundwater, in and around Kalpakkam, Tamil Nadu, India  

NASA Astrophysics Data System (ADS)

The saturation index of clay minerals like Gibbsite, Kaolinite, Illite, Montmorillonite and Chlorite in groundwater were studied in detail by collecting 29 groundwater samples from the shallow coastal aquifers in and around Kalpakkam. The samples collected were analysed for major cations, anions and trace elements by using standard procedures. The study reveals that pH has a significant role in the saturation index (SI) of minerals. It also shows that the relationship of electrical conductivity to the SI of these minerals is not significant than that of the ionic strength, log pCO2 values, and alumina silica ratio have significant relation to the SI of these clay minerals. The SI of these clay minerals was spatially distributed to identify the areas of higher SI. Silica has good correlation to SI of Kaolinite, Gibbsite and Montmorillonite and Al has good correlation to SI of all the minerals except to that of Chlorite.

Chidambaram, S.; Karmegam, U.; Sasidhar, P.; Prasanna, M. V.; Manivannan, R.; Arunachalam, S.; Manikandan, S.; Anandhan, P.

2011-10-01

101

Clay minerals as proxies of the late Quaternary East Asian monsoon evolution in the South China Sea revisited  

NASA Astrophysics Data System (ADS)

Clay minerals have a significant role in sedimentation and paleoenvironment studies of the South China Sea. Many previous studies showed that the time series variation in late Quaternary clay mineral assemblages presents mostly glacial-interglacial cyclicity, and they were interpreted chemical weathering closely related to contemporaneous climatic changes of source areas. It is quite debatable whether clay minerals can directly indicate the East Asian monsoon evolution. To answer this question, we investigated sediment cores collected in various locations in the South China Sea during the MARCO POLO cruise in 2005, MD05-2904 (2066 m water depth, abbreviated w.d.) and MD05-2905 (1198 m w.d.) in the north, MD05-2901 (1254 m w.d.) and MD05-2899 (2393 m w.d.) in the west, and MD05-2895 (1982 m w.d.) in the south. Our results show that provenance supply and current transport directly control the clay mineralogical compositions in core and surface sediments, with various expression forms in different locations. In the north, the clay mineral assemblage indicates a relationship between surface current transport (for smectite) under the significant influence of the Kuroshio intrusion and deep water transport (for illite and chlorite). In the west, the East Asian monsoons forced surface currents and different clay-composition provenances affect the glacial-interglacial cyclicity of clay mineral variations. In the south, land-sea distribution variations controlled by the sea level change determine the sources of clay minerals. Our new studies suggest that the late Quaternary clay minerals in the South China Sea do not bear contemporaneous paleoclimatic features, and their implication for proxies of the East Asian monsoon evolution is realized through both the provenance supply and current transport processes.

Liu, Z.; Li, X.; He, Z.; Colin, C.; Zhao, Y.

2012-12-01

102

Clay mineral records of East Asian monsoon evolution during late Quaternary in the southern South China Sea  

Microsoft Academic Search

High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 190 ka during late Quaternary\\u000a from core MD01-2393 off the Mekong River in the southern South China Sea are reported to reconstruct a history of East Asian\\u000a monsoon evolution. The dominating clay mineral components indicate a strong glacial-interglacial cyclicity, with high glacial\\u000a illite, chlorite, and kaolinite contents and

Zhifei Liu; C. Colin; A. Trentesaux; D. Blamart

2005-01-01

103

DE-FG02-06ER15364: Final Technical Report Nanoscale Reactivity of Clays, Clay Analogues (Micas), and Clay Minerals  

SciTech Connect

The project objectives were to determine the nanoscale to molecular scale structure of the interface between muscovite mica and aqueous solutions containing various sorbates and to explore systematics that control the incorporation of inorganic and organic chemical components during aging of nanoparticles of iron-oxides and aluminosilicate clays. The basal surface of phyllosilicates is a primary sorbent of environmental contaminants, natural organic matter, and nutrients. Micas are also superb atomically-flat substrates used in materials science and surface physics applications. We applied X-ray scattering techniques using high brilliance synchrotron radiation to investigate molecular-scale details of mica’s interface structure in solutions containing common and toxic cations, anions, and natural organic molecules. Nanoparticles are ubiquitous in the environment and have a high capacity for sorbing contaminants through the combined effects of their high surface areas and pH-dependent surface charge. Aging of nanoparticles from metastable to stable phases can be inhibited by sorption of nonstructural components, but exact mechanisms are unknown. We synthesized Fe-oxides and aluminosilicate clay minerals from aqueous solutions in the presence of selected anions, and organic molecules, and quantified the uptake of these additives during aging and some implications for nanoparticle formation.

Nagy, Kathryn L.

2008-07-03

104

[Effect of treatments of hydrogen peroxide and sodium dithionite-citrate-bicarbonate on clay minerals of red earth sediments].  

PubMed

As classical procedures for pretreatment of soil sediments, hydrogen peroxide (H2O2) and sodium dithionite-citrate-bicarbonate (DCB) treatment methods are very important in removing the organic matter and iron oxides acting as cementing agents in the soils. However, both of these methods have less been focused on the effect on the clay minerals when separating. Here, we report the comparable methods between H2O2 and DCB to reveal their effect on clay minerals in red earth sediments using X-ray diffraction (XRD). The XRD results suggested that mineral particles can be totally decentralized by either H2O2 or DCB method in the soils and high purity clay minerals can be obtained by separating quartz and other impurities from clay minerals effectively. However, the XRD data were distorted by the DCB treatment owning to the cation exchange between Na+ and interlayer cation. On the contrary, the authentic data can be obtained by H2O2 treatment. Therefore, the H2O2 treatment seems to be a more appropriate method to obtain authentic information of clay mineralogy when separating of clay minerals from red earth sediments. PMID:23841441

Li, Rong-Biao; Hong, Han-Lie; Yin, Ke; Wang, Chao-Wen; Gao, Wen-Peng; Han, Wen; Wu, Qing-Feng

2013-04-01

105

Molecular dynamics simulations of the adsorption of proteins on clay mineral surfaces  

NASA Astrophysics Data System (ADS)

Some initial results of molecular dynamics simulations of the adsorption of proteins on clay mineral surfaces are being reported. Specifically, the interactions of pyrophyllite surfaces with crambin, rubredoxin, and several oligopeptides were investigated. It is found that clay mineral surfaces can have a denaturing effect on adsorbed proteins for two reasons: (1) they are dehydrating agents, because they perturb the random environment of water molecules that globular proteins need to maintain their native structure; and (2) clay surfaces can establish non-bonded interactions with proteins which compete effectively with the interactions inside a peptide chain. The changes in secondary and tertiary protein structure induced by adsorption to pristine surfaces, or surfaces coated with water, lead to backbone torsions away from the most populated regions of ?,?-space, to regions which are not frequently populated in unperturbed proteins. ?- and ? R-conformations, specifically, are not stable on pyrophyllite but undergo transitions, with some preference, to an area close to C 7eq. Because of the size of the adsorbed systems, unit cells with adsorbed peptides may be distorted, bulging at the site of adsorption, and displaying a continuously varying interlayer space between the empty parts and those that are occupied by an adsorbate. As a result, warped, or S-shaped basal planes are found.

Yu, C. H.; Norman, M. A.; Newton, S. Q.; Miller, D. M.; Teppen, B. J.; Schäfer, L.

2000-12-01

106

Syn- and post-sedimentary controls on clay mineral assemblages in a tectonically active basin, Andean Argentinean foreland  

NASA Astrophysics Data System (ADS)

In the northern part of the Calchaquí Valley (NW Argentina), Palaeogene Andean foreland sediments are represented by a 1400-metre-thick continental succession (QLC: Quebrada de Los Colorados Formation) consisting of claystones, siltstones, sandstones, and conglomerates representing sedimentation in fluvial-alluvial plains and alluvial fan settings. To understand the main syn- and postsedimentary variables controlling the clay mineral assemblages of this succession, we have studied the fine-grained clastic sediments by X-ray diffraction and electron microscopy, along with a detailed sedimentary facies analysis, for two representative sections. In the northern section, the whole succession was sampled and analysed by XRD, whereas in the second section, a control point 15 km to the south, only the basal levels were analysed. The XRD study revealed a strong contrast in clay mineral assemblages between these two sections as well as with sections in the central Calchaquí Valley studied previously. In the northernmost part of the study area, a complete evolution from smectite at the top to R3 illite/smectite mixed-layers plus authigenic kaolinite at the bottom, through R1-type mixed-layers in between, has been recognized, indicating the attainment of late diagenesis. In contrast, the clay mineral assemblages of equivalent foreland sediments cropping out only 15 km to the south contain abundant smectite and micas, subordinate kaolinite and chlorite, and no I/S mixed-layers to the bottom of the sequence. Early diagenetic conditions were also inferred in a previous study for equivalent sediments of the QLC Formation cropping out to the south, in the central Calchaquí Valley, as smectite occurs in basal strata. Burial depths of approximately 3000 m were estimated for the QLC Formation in the central and northern Calchaquí Valley; in addition, an intermediate to slightly low geothermal gradient can be considered likely for both areas as foreland basins are regarded as hypothermal basins. Consequently, the attainment of late diagenesis in the northernmost study area cannot be explained by significant differences in burial depth nor in geothermal gradient in relation to the section 15 km to the south nor with the central Calchaquí Valley. The formation of R3 mixed-layer I/S and authigenic kaolinite in the northern study area was most likely controlled by the circulation of hot, deep fluids along the reverse faults that bounded the Calchaquí valley. These faults were active during the Cenozoic, as evidenced by the syndepositional deformation features preserved in the studied sediments. Stress could also have been a driving force in burial diagenesis at the R3 mixed-layer I/S stage in these young continental sediments.

Do Campo, Margarita; Nieto, Fernando; del Papa, Cecilia; Hongn, Fernando

2014-07-01

107

Molecular simulation of carbon dioxide, brine, and clay mineral interactions and determination of contact angles.  

PubMed

Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via geochemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. We used large-scale molecular dynamics simulations to study the behavior of supercritical CO2 and aqueous fluids on both the hydrophilic and hydrophobic basal surfaces of kaolinite, a common clay mineral. In the presence of a bulk aqueous phase, supercritical CO2 forms a nonwetting droplet above the hydrophilic surface of kaolinite. This CO2 droplet is separated from the mineral surface by distinct layers of water, which prevent the CO2 droplet from interacting directly with the mineral surface. Conversely, both CO2 and H2O molecules interact directly with the hydrophobic surface of kaolinite. In the presence of bulk supercritical CO2, nonwetting aqueous droplets interact with the hydrophobic surface of kaolinite via a mixture of adsorbed CO2 and H2O molecules. Because nucleation and precipitation of minerals should depend strongly on the local distribution of CO2, H2O, and ion species, these nanoscale surface interactions are expected to influence long-term mineralization of injected carbon dioxide. PMID:24410258

Tenney, Craig M; Cygan, Randall T

2014-02-01

108

Efficiency of different clay minerals modified with a cationic surfactant in the adsorption of pesticides: Influence of clay type and pesticide hydrophobicity  

Microsoft Academic Search

In the present work we studied the efficiency of a series of clay minerals (montmorillonite, illite, muscovite, sepiolite and palygorskite) modified with the cationic surfactant octadecyltrimetylammonium bromide (ODTMA) in the adsorption of the pesticides penconazole, linuron, alachlor, atrazine and metalaxyl. A study was also carried out on the effect of the structure (expansible and non-expansible layered, and non-layered), the surface

M. J. Sanchez-Martin; M. S. Rodriguez-Cruz; M. S. Andrades; M. Sanchez-Camazano

2006-01-01

109

Effect of organic matter properties, clay mineral type and thermal maturity on gas adsorption in organic-rich shale systems  

USGS Publications Warehouse

A series of CH4 adsorption experiments on natural organic-rich shales, isolated kerogen, clay-rich rocks, and artificially matured Woodford Shale samples were conducted under dry conditions. Our results indicate that physisorption is a dominant process for CH4 sorption, both on organic-rich shales and clay minerals. The Brunauer–Emmett–Teller (BET) surface area of the investigated samples is linearly correlated with the CH4 sorption capacity in both organic-rich shales and clay-rich rocks. The presence of organic matter is a primary control on gas adsorption in shale-gas systems, and the gas-sorption capacity is determined by total organic carbon (TOC) content, organic-matter type, and thermal maturity. A large number of nanopores, in the 2–50 nm size range, were created during organic-matter thermal decomposition, and they significantly contributed to the surface area. Consequently, methane-sorption capacity increases with increasing thermal maturity due to the presence of nanopores produced during organic-matter decomposition. Furthermore, CH4 sorption on clay minerals is mainly controlled by the type of clay mineral present. In terms of relative CH4 sorption capacity: montmorillonite ? illite – smectite mixed layer > kaolinite > chlorite > illite. The effect of rock properties (organic matter content, type, maturity, and clay minerals) on CH4 adsorption can be quantified with the heat of adsorption and the standard entropy, which are determined from adsorption isotherms at different temperatures. For clay-mineral rich rocks, the heat of adsorption (q) ranges from 9.4 to 16.6 kJ/mol. These values are considerably smaller than those for CH4 adsorption on kerogen (21.9–28 kJ/mol) and organic-rich shales (15.1–18.4 kJ/mol). The standard entropy (?s°) ranges from -64.8 to -79.5 J/mol/K for clay minerals, -68.1 to -111.3 J/mol/K for kerogen, and -76.0 to -84.6 J/mol/K for organic-rich shales. The affinity of CH4 molecules for sorption on organic matter is stronger than for most common clay minerals. Thus, it is expected that CH4 molecules may preferentially occupy surface sites on organic matter. However, active sites on clay mineral surfaces are easily blocked by water. As a consequence, organic-rich shales possess a larger CH4-sorption capacity than clay-rich rocks lacking organic matter. The thermodynamic parameters obtained in this study can be incorporated into model predictions of the maximum Langmuir pressure and CH4- sorption capacity of shales under reservoir temperature and pressure conditions.

Zhang, Tongwei; Ellis, Geoffrey S.; Ruppel, Stephen C.; Milliken, Kitty; Lewan, Mike; Sun, Xun

2013-01-01

110

Sorption of uranium(VI) at the clay mineral–water interface  

Microsoft Academic Search

Batch experiments were conducted to study the sorption of uranium on selected clay minerals (KGa-1b and KGa-2 reference kaolinite,\\u000a SWy-2 and STx-1b reference montmorillonite, and IBECO natural bentonite) as a function of pH (4–9) and 0.001, 0.01, and 0.025 M\\u000a NaCl in equilibrium with the CO2 partial pressure of the atmosphere. Uranium concentrations were kept below 100 ?g L?1 to avoid precipitation of

Samer Bachmaf; Broder J. Merkel

2011-01-01

111

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra  

Microsoft Academic Search

A linear retrieval (spectral deconvolution) algorithm is developed and applied to high-resolution laboratory infrared spectra of particulate mixtures and their end- members. The purpose is to place constraints on, and test the viability of, linear spectral deconvolution of high-resolution emission spectra. The effects of addition of noise, data reproducibility, particle size variation, an increasing number of minerals in the mixtures,

Michael S. Ramsey; Philip R. Christensen

1998-01-01

112

The First X-ray Diffraction Patterns of Clay Minerals from Gale Crater  

NASA Technical Reports Server (NTRS)

The Mars Science Laboratory (MSL) Rover, Curiosity spent approx 150 sols at Yellowknife Bay (YKB) studying a section of fluvio-lacustrine sedimentary rocks (with potential indications of volcanic influence), informally known as the Yellowknife Bay formation. YKB lies in a distal region of the Peace Vallis alluvial fan, which extends from the northern rim of Gale Crater toward the dune field at the base of Mt Sharp. Sedimentological and stratigraphic observations are consistent with the Yellowknife Bay formation being part of a distal fan deposit, which could be as young as middle Hesperian to even early Amazonian in age (approx 3.5 to 2.5 Ga). The Yellowknife Bay formation hosts a unit of mudstone called the Sheepbed member. Curiosity obtained powdered rock samples from two drill holes in the Sheepbed Member, named John Klein and Cumberland, and delivered them to instruments in Curiosity. Data from CheMin, a combined X-ray diffraction (XRD)/X-ray fluorescence instrument (XRF), has allowed detailed mineralogical analysis of mudstone powders revealing a clay mineral component of approx 20 wt.% in each sample. The clay minerals are important indicators of paleoenvironmental conditions and sensitive recorders of post-depositional alteration processes. The XRD pattern of John Klein reveals a 021 band consistent with a trioctahedral phyllosilicate. A broad peak at approx 10A with a slight inflexion at approx 12A indicates the presence of 2:1 type clay minerals in the John Klein sample. The trioctahedral nature of the clay minerals, breadth of the basal reflection, and presence of a minor component with larger basal spacing suggests that John Klein contains a trioctahedral smectite (probably saponite), whose interlayer is largely collapsed because of the low-humidity conditions. The XRD patterns show no evidence of corrensite (mixed-layer chlorite/smectite) or chlorite, which are typical diagenetic products of trioctahedral smectites when subjected to burial and heating >60degC in the presence of water. Given estimated geothermal gradients on Mars temperatures <60 degC might still be consistent with (but do not require) moderate burial. However, our ability to identify interstratified minerals is greatly limited by the lack of access to traditional treatments methods used in the lab (e.g., ethylene glycol solvation). Our preferred explanation for the origin of trioctahedral smectites in Sheepbed mudstone is in situ production via reaction of olivine, water and Si-bearing amorphous material, an important mudstone component detected by XRD. Elevated levels of magnetite in the Sheepbed and the trioctahedral monomineralic nature of the clay minerals support this model. These observations, combined with previous studies of olivine stability, support the persistence of circum-neutral hydrous conditions for thousands of years at YKB.

Bristow, Thomas; Blake, David; Bish, David L.; Vaniman, David; Ming, Douglas W.; Morris, Richard V.; Chipera, Steve; Rampe, Elizabeth B.; Farmer, Jack, D.; Treiman, Allan H; Downs, Robert; Morrison, Shaunna; Achilles, Cherie; DesMarais, David J.; Crisp, Joy A.; Sarrazin, Philippe; Morookian, John Michael; Grotzinger. John P.

2013-01-01

113

Zeolite-clay mineral zonation of volcaniclastic sediments within the McDermitt caldera complex of Nevada and Oregon  

USGS Publications Warehouse

Volcaniclastic sediments deposited in the moat of the collapsed McDermitt caldera complex have been altered chiefly to zeolites and potassium feldspar. The original rhyolitic and peralkaline ash-flow tuffs are included in conglomerates at the caldera rims and grade into a lacustrine series near the center of the collapse. The tuffs show a lateral zeolitic alteration from almost fresh glass to clinoptilolite, clinoptilolite-mordenite, and erionite; to analcime-potassium feldspar; and finally to potassium feldspar. Vertical zonation is in approximately the same order. Clay minerals in associated mudstones, on the other hand, show little lateral variation but a distinct vertical zonation, having a basal dioctahedral smectite, a medial trioctahedral smectite, and an upper dioctahedral smectite. The medial trioctahedral smectite is enriched in lithium (as much as 6,800 ppm Li). Hydrothermal alteration of the volcaniclastic sediments, forming both mercury and uranium deposits, caused a distinct zeolite and clay-mineral zonation within the general lateral zonation. The center of alteration is generally potassium feldspar, commonly associated with alunite. Potassium feldspar grades laterally and vertically to either clinoptilolite or clinoptilolite-mordenite, generally associated with gypsum. This zone then grades vertically and laterally into fresh glass. The clay minerals are a dioctahedral smectite, a mixed-layer clay mineral, and a 7-A clay mineral. The mixed-layer and 7-A clay minerals are associated with the potassium feldspar-alunite zone of alteration, and the dioctahedral smectite is associated with clinoptilolite. This mineralogical zonation may be an exploration guide for mercury and uranium mineralization in the caldera complex environment.

Glanzman, Richard K.; Rytuba, James J.

1979-01-01

114

Preparation of clay mineral samples for high resolution x-ray imaging  

NASA Astrophysics Data System (ADS)

In the development of optimum ceramic materials for plastic forming, it is of fundamental importance to gain insight into the compositions of the clay minerals. Whereas spectroscopic methods are adequate for determining the elemental composition of a given sample, a knowledge of the spatial composition, together with the shape and size of the particles leads to further, valuable insight. This requires an imaging technique such as high resolution X-ray microscopy. In addition, fluorescence spectroscopy provides a viable element mapping technique. Since the fine particle fraction of the materials has a major effect on physical properties like plasticity, the analysis is focused mainly on the smallest particles. To separate these from the bigger agglomerates, the raw material has to pass through several procedures like centrifugation and filtering. After that, one has to deposit a layer of appropriate thickness on to a suitable substrate. These preparative techniques are described here, starting from the clay mineral raw materials and proceeding through to samples that are ready to analyze. First results using high resolution x-ray imaging are shown.

Abbati, Gennaro; Seim, Christian; Legall, Herbert; Stiel, Holger; Thomas, Noel; Wilhein, Thomas

2013-10-01

115

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra  

Microsoft Academic Search

A linear retrieval (spectral deconvolution) algorithm is developed and applied to high-resolution laboratory infrared spectra of particulate mixtures and their end-members. The purpose is to place constraints on, and test the viability of, linear spectral deconvolution of high-resolution emission spectra. The effects of addition of noise, data reproducibility, particle size variation, an increasing number of minerals in the mixtures, and

Michael S. Ramsey; Philip R. Christensen

1998-01-01

116

Improved dewatering behavior of clay minerals dispersions via interfacial chemistry and particle interactions optimization.  

PubMed

Orthokinetic flocculation of clay dispersions at pH 7.5 and 22 degrees C has been investigated to determine the influence of interfacial chemistry and shear on dewatering and particle interactions behavior. Modification of pulp chemistry and behavior was achieved by using kaolinite and Na-exchanged (swelling) smectite clay minerals, divalent metal ions (Ca(II), Mn(II)) as coagulants and anionic polyacrylamide copolymer (PAM A) and non-ionic polyacrylamide homopolymer (PAM N) as flocculants. The pivotal role of shear, provided by a two-blade paddle impeller, was probed as a function of agitation rate (100-500 rpm) and time (15/60 s). Particle zeta potential and adsorption isotherms were measured to quantify the interfacial chemistry, whilst rheology and cryogenic SEM were used to investigate particle interactions and floc structure and aggregate network, respectively. Osmotic swelling, accompanied by the formation of "honeycomb" particle network structure and high yield stress, was produced by the Na-exchanged smectite, but not kaolinite, dispersions. Dispersion of the clay particles in 0.05 M Ca(II) or Mn(II) solution led to a marked reduction in particle zeta potential, complete suppression of swelling, honeycomb network structure collapse and a concomitant reduction in shear yield stress of smectite pulps. Optimum conditions for improved, orthokinetic flocculation performance of negatively charged clay particles, reflecting faster settling flocs comprised (i) coagulation, (ii) moderate agitation rate, (iii) shorter agitation time, and (iv) anionic rather than non-ionic PAM. The optimum dewatering rates were significantly higher than those produced by standard, manual-mixing flocculation techniques (plunging and cylinder inversion) commonly used in industry for flocculant trials. The optimum flocculation conditions did not, however, have a significant impact on the final sediment solid content of 20-22 wt%. Further application of shear to pre-sedimented pulps improved consolidation by 5-7 wt% solid. Higher shear yield stresses and greater settling rates were displayed by PAM A based than PAM N based pulps and this is attributed to the former's more expanded interfacial conformation and greater clay particles bridging ability. It appears that the intrinsic clay particles' physico-chemical properties and interactions limit compact pulp consolidation. PMID:16038921

McFarlane, Angus; Bremmell, Kristen; Addai-Mensah, Jonas

2006-01-01

117

Effects of heavy metals on the electrokinetic properties of bacteria, yeast, and clay minerals  

SciTech Connect

The electrokinetic patterns of four bacteria (Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae, Canida albicans), and two clay minerals (montmorillonite, kaolinite) in the presence of the chloride salts of heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn) and of Na and Mg were determined by microelectrophoresis. The cells and clays were net negatively charged at pH values above their isoelectric point (pI) in solutions of Na, Mg, Hg, and Pb with an ionic strength (..mu..) of 3 x 10/sup -4/. However, at pH values above pH 5.0, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn. The charge of the bacteria and S. cerevisiae also reversed in solution of Ni and Cu with a ..mu.. > 3 x 10/sup -4/, whereas there was no reversal in solutions with a ..mu.. < 3 x 10/sup -4/. The clays became net positively charged when the ..mu.. of Cu was > 3 x 10/sup -4/ and that of Ni was > 1.5 x 10/sup -4/. The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite) (..mu.. = 3 x 10/sup -4/). The pI of the cells in the presence of some heavy metals, especially Ni and Cr, was at higher pH values than in the presence of Na and Mg.

Collins, Y.E.

1987-01-01

118

Patterns of mineral transformations in clay gouge, with examples from low-angle normal fault rocks in the western USA  

NASA Astrophysics Data System (ADS)

Neoformed minerals in shallow fault rocks are increasingly recognized as key to the behavior of faults in the elasto-frictional regime, but neither the conditions nor the processes which wall-rock is transformed into clay minerals are well understood. Yet, understanding of these mineral transformations is required to predict the mechanical and seismogenic behavior of faults. We therefore present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low-angle normal faults (LANF's) in the American Cordillera to demonstrate the range and type of clay transformations in natural fault gouges. The sampled faults juxtapose a wide and representative range of wall rock types, including sedimentary, metamorphic and igneous rocks under shallow-crustal conditions. Clay mineral transformations were observed in all but one of 28 faults; one fault contains only mechanically derived clay-rich gouge, which formed entirely by cataclasis. Clay mineral transformations observed in gouges show four general patterns: 1) growth of authigenic 1Md illite, either by transformation of fragmental 2M1 illite or muscovite, or growth after the dissolution of K-feldspar. Illitization of fragmental illite-smectite is observed in LANF gouges, but is less common than reported from faults with sedimentary wall rocks; 2) 'retrograde diagenesis' of an early mechanically derived chlorite-rich gouge to authigenic chlorite-smectite and saponite (Mg-rich tri-octahedral smectite); 3) reaction of mechanically derived chlorite-rich gouges with Mg-rich fluids at low temperatures (50-150 °C) to produce localized lenses of one of two assemblages: sepiolite + saponite + talc + lizardite or palygorskite +/- chlorite +/- quartz; and 4) growth of authigenic di-octahedral smectite from alteration of acidic volcanic wall rocks. These transformation groups are consistent with patterns observed in fault rocks elsewhere. The main controls for the type of neoformed clay in gouge appear to be wall-rock chemistry and fluid chemistry, and temperatures in the range of 60-180 °C.

Haines, Samuel H.; van der Pluijm, Ben A.

2012-10-01

119

Comparison of three different statistical methods for retrieving the lunar mineral abundance  

NASA Astrophysics Data System (ADS)

Our current work aims to develop the most reliable model for estimating lunar mineral abundances. In our previous studies, partial least squares (PLS) and genetic algorithm - partial least squares (GA-PLS) models have been used. PLS has two limitations: 1) redundant spectral bands cannot be removed effectively; and 2) non-linearity between lunar soil reflectance spectra and lunar mineral abundances cannot be accommodated. GA is an effective tool for selecting a set of spectral bands that are most sensitive to lunar minerals, and to some extent overcomes the first limitation. One objective of this study is to compare the PLS and GA-PLS performances in estimating lunar mineral abundances. Given the fact that GA-PLS is still subjected to the effect of nonlinearity, a hybrid PLS-BPNN model is developed and tested to determine how effective back propagation neural network (BPNN) is for overcoming the two limitations. BPNN accommodates nonlinearity with the sigmoid functions connecting BPNN layers of nodes, and the weights of redundant spectral bands are significantly decreased through the learning process. The lunar soil characterization consortium (LSCC) dataset is the only complete 'ground truth' data of the Moon consisting both soil reflectance spectra and mineral abundances. The LSCC dataset is composed of totally 19 Apollo samples and each sample has four particle size groups (< 10 µm, 10 - 20 µm, 20 - 45 µm, < 45 µm). Although the mineral abundances of the group < 45 µm are not measured, the mineral abundances of this group (validation set) are assumed to be the average of the mineral abundances of samples in other three groups (calibration set). PLS, GA-PLS and PLS-BPNN are assessed based on R-squares and relative root mean square error for the validation. The results indicates that GA-PLS performs better than PLS for retrieving the mineral abundance of agglutinate, plagioclase, pyroxene, and volcanic glasses (Figure 1), but PLS is preferred over GA-PLS for modeling the abundance of olivine and ilmenite (Figure 1). Comparison among the three models indicates that PLS-BPNN performs significantly better than both PLS and GA-PLS for estimating agglutinate, pyroxene, olivine, ilmenite, and volcanic glasses (Figure 1). For estimation of plagioclase, both PLS-BPNN and GA-PLS perform equally well. Overall PLS-BPNN is preferred over both PLS and GA-PLS for quantifying all lunar surface dominant minerals. Figure 1. Comparison of R- squares and relative root mean square errors resulting from the PLS, GA-PLS and PLS-BPNN validation.

Li, L.; Li, S.

2010-12-01

120

Spatial distribution of clay minerals in agrochernozems of erosional and denudational plains in the Stavropol region  

NASA Astrophysics Data System (ADS)

The distribution pattern of the fine fractions (<1.0 and 1-5 ?m) and the mineralogical composition of the agrochernozems formed on the erosional-denudational plains of the Stavropol region have been studied. Erosion and denudation caused the redistribution of the fine material within the catena with its maximal accumulation on the lowermost part of the slope. The same processes favored the formation of surface deposits slightly differing in the composition of the principal mineral phases, i.e., complex disordered mixedlayered micas-smectites with varying combinations of micaceous and smectite layers in crystallites and di- and trioctahedral hydromicas. Imperfect kaolinite and magnesium-ferric chlorite are accompanying minerals. An increase in the amount of mixed-layered minerals with smectite layer is observed down the profile. In addition to the mentioned minerals, the individual smectite and clinoptilolite, which are components of Tertiary deposits, are identified in the lower parts of the agrochernozem profiles. The fine-silt fractions consist of (in decreasing order) di- and tri-octahedral micas, quartz, feldspars, plagioclase, and an admixture of phyllosilicates (kaolinite, chlorite, and mixed-layered chlorite-smectites). The maximal amount of the fine fraction, as well as the maximal amount of mica in it, is registered in the soils in the lower part of the slope. The phyllosilicates are decomposed in this fraction in the upper horizons. The seven-year-long application of mineral fertilizers intensified the peptization of the soil mass in the arable horizons, which increased the content of clay particles in them. A more contrasting distribution of the mixed-layered formations in the profiles, a considerable decrease in their reflection intensities, an increase in the structural disorder of the minerals, and a certain increase in the content of the fine-dispersed quartz are observed.

Chizhikova, N. P.; Godunova, E. I.; Shkabarda, S. N.; Samsonova, A. A.; Malueva, T. I.

2012-09-01

121

Spectroscopic evidence for Fe(II)-Fe(III) electron transfer at clay mineral edge and basal sites.  

PubMed

Despite the importance of Fe redox cycling in clay minerals, the mechanism and location of electron transfer remain unclear. More specifically, there is some controversy whether electron transfer can occur through both basal and edge surfaces. Here we used Mössbauer spectroscopy combined with selective chemical extractions to study electron transfer from Fe(II) sorbed to basal planes and edge OH-groups of clay mineral NAu-1. Fe(II) sorbed predominantly to basal planes at pH values below 6.0 and to edge OH-groups at pH value 7.5. Significant electron transfer occurred from edge OH-group bound Fe(II) at pH 7.5, whereas electron transfer from basal plane-sorbed Fe(II) to structural Fe(III) in clay mineral NAu-1 at pH 4.0 and 6.0 occurred but to a much lower extent than from edge-bound Fe(II). Mössbauer hyperfine parameters for Fe(II)-reacted NAu-1 at pH 7.5 were consistent with structural Fe(II), whereas values found at pH 4.0 and 6.0 were indicative of binding environments similar to basal plane-sorbed Fe(II). Reference experiments with Fe-free synthetic montmorillonite SYn-1 provided supporting evidence for the assignment of the hyperfine parameters to Fe(II) bound to basal planes and edge OH-groups. Our findings demonstrate that electron transfer to structural Fe in clay minerals can occur from Fe(II) sorbed to both basal planes and edge OH-groups. These findings require us to reassess the mechanisms of abiotic and microbial Fe reduction in clay minerals as well as the importance of Fe-bearing clay minerals as a renewable source of redox equivalents in subsurface environments. PMID:23517074

Neumann, Anke; Olson, Tyler L; Scherer, Michelle M

2013-07-01

122

Ionic liquids in soils: effects of different anion species of imidazolium based ionic liquids on wheat ( Triticum aestivum ) as affected by different clay minerals and clay concentrations  

Microsoft Academic Search

This study contributes to a prospective hazard assessment of ionic liquids, focusing on the terrestrial environment. The influence\\u000a of differently composed soils—varying contents of the clay minerals smectite and kaolinite—on the toxicity of different anion\\u000a species of imidazolium based ionic liquids was studied for growth inhibition of wheat (Triticum aestivum). IM14 (CF3SO2)2N appeared the most toxic, independently of the investigated

Marianne Matzke; Stefan Stolte; Jürgen Arning; Ute Uebers; Juliane Filser

2009-01-01

123

Terrestrial Analogs for Clay Minerals at Yellowknife Bay, Gale Crater, Mars  

NASA Technical Reports Server (NTRS)

Sediments of the Sheepbed unit, Gale Crater, were analyzed by the CheMin X-ray diffraction instrument on the Curiosity Rover. The sediments consist of typical basalt minerals (Fe-forsterite, augite, pigeonite, plagioclase), as well as Fe oxide/hydroxides, Fesulfides, amorphous material, and a phyllosilicate. The phyllosilicate has a broad 001 peak at approx 1.0 nm, consistent with a poorly ordered smectite. However, in the absence of diagnostic tests possible on Earth, its identity is not clear. The position of the 06L diffraction band is generally used to distinguish dioctahedral from trioctahedral smectite, but it is beyond CheMin's range of 2 Theta. The measured position of the 02L diffraction band (approx 22.5deg 2 Theta by CheMin), implies that the smectite is trioctahedral. The exact position and shape of the 02L band is determined by the cations in the 'M' sites of the smectite; to constrain those cations, we sought analogs among terrestrial smectites, emphasizing those developed from basaltic precursors. A potential analog for the Sheepbed smectite is 'griffithite,' a variety of trioctahedral smectite in altered basalt of the Topanga formation, Griffith Park, Los Angeles. 'Griffithite' has an 02L diffraction band that is close in position and shape to that of the Sheepbed smectite, although 'griffithite' has a very sharp 001 peak, indicating a high degree of layer ordering not seen in the Sheepbed smectite. A typical chemical formula for 'griffithite,' determined by electron microprobe, is (Ca0.59 Na0.03) (Mg4.28 Fe1.83) (Si6.64 Al1.36) O20 (OH)4, normalized to Si+Al=8. This formula is consistent with a fully trioctahedral Fe-Mg smectite with Ca and Na as interlayer cations. In the Topanga basalt, four types of 'griffithite' are present: fine-grained, filling cracks and vesicles; coarse-grained, filling vesicles; coarse-grained, replacing olivine phenocrysts; and coarse-grained, replacing glassy mesostasis. The fine-grained 'griffithite' formed first, and the last three varieties may be contemporaneous. One sample shows agate (alpha- quartz) that was precipitated between the episodes of deposition of the fine-grained and coarse-grained 'griffithite.' 'Griffithite' is not unique as a possible terrestrial analog - some clay minerals from the Doushantou formation, China, have similar 02L diffraction bands, and many basalts contain smectites in vesicles and as replacements after olivine. Similar trioctahedral smectites occur also in the nakhlite martian meteorites - as veinlets and replacements of olivine. By understanding the formation of these terrestrial clays, we hope to constrain the nature and mechanism of formation of the Sheepbed clay mineral.

Treiman, Allan H; Morris, Richard V.; Bristow, Thomas; Ming, Douglas W.; Achillies, Cherie; Bish, David L.; Blake, David; Vaniman, David; Chipera, Steve

2013-01-01

124

First-principles study of cesium adsorption to weathered micaceous clay minerals  

NASA Astrophysics Data System (ADS)

A large amount of radioactive nuclides was produced into environment due to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Residents near FDNPP were suffering from radioactive cesium and then evacuated, because which has long half-life and is retained by surface soil for long time. The Japanese government has been decontaminating the cesium by removing the surface soil in order to return them to their home. This decontamination method is very effective, but which produces huge amount of waste soil. This becomes another big problem in Fukushima, because it is not easy to find large storage sites. Then effective and economical methods to reduce the volume of the waste soil are needed. However, it has not been invented yet. One of the reasons is lack of knowledge about microscopic process of adsorption/desorption of cesium to/from soil. It is known that weathered micaceous clay minerals play crucial role on adsorption and retention of cesium. They are expected to have special sorption sites, called frayed edge sites (FESs), which adsorb cesium selectively and irreversibly. Properties of FES have been intensely investigated by experiments. But microscopic details of the adsorption process on FES are still unclear. Because direct observation of the process with current experimental techniques is quite difficult. We investigated the adsorption of cesium to FES in muscovite, which is a typical micaceous clay mineral, via first-principles calculations (density functional theory). We made a minimal model of FES and evaluate the energy difference before and after cesium adsorption to FES. This is the first numerical modeling of FES. It was shown that FES does adsorb cesium if the weathering of muscovite has been weathered. In addition, we revealed the mechanism of cesium adsorption to FES, which is competition between ion radius of cesium and the degree of weathering. I plan to discuss volume reduction of the waste soil based on our result. Reference M. Okumura, H. Nakamura, and M. Machida, Mechanism of Strong Affinity of Clay Minerals to Radioactive Cesium : First-Principles Calculation Study for Adsorption of Cesium at Frayed Edge Sites in Muscovite, Journal of the Physical Society of Japan 82, 033802 (2013).

Okumura, Masahiko; Nakamura, Hiroki; Machida, Masahiko

2014-05-01

125

Influence of crop residues on trifluralin mineralization in a silty clay loam soil.  

PubMed

Trifluralin is typically applied onto crop residues (trash, stubble) at the soil surface, or onto the bare soil surface after the incorporation of crop residues into the soil. The objective of this study was to quantify the effect of the type and amount of crop residues in soil on trifluralin mineralization in a Wellwood silty clay loam soil. Leaves and stubble of Potato (Solanum tuberosum) (P); Canola (Brassica napus) (C), Wheat (Triticum aestivum) (W), Oats (Avena sativa), (O), and Alfalfa (Medicago sativa) (A) were added to soil microcosms at rates of 2%, 4%, 8% and 16% of the total soil weight (25 g). The type and amount of crop residues in soil had little influence on the trifluralin first-order mineralization rate constant, which ranged from 3.57E-03 day(-1) in soil with 16% A to 2.89E-02 day(-1) in soil with 8% W. The cumulative trifluralin mineralization at 113 days ranged from 1.15% in soil with 16% P to 3.21% in soil with 4% C, again demonstrating that the observed differences across the treatments are not of agronomic or environmental importance. PMID:17454379

Farenhorst, Annemieke

2007-01-01

126

Separation of patatins and protease inhibitors from potato fruit juice with clay minerals as cation exchangers.  

PubMed

Potato fruit juice as a by-product of the starch industry contains proteins with interesting functionalities such as protease inhibitors or patatin with its high nutritional value. Due to their functional properties, these proteins are principally of industrial interest. A drawback for the application of these potato proteins is the separation and isolation under maintenance of the biological activity. So far, there are no methods in literature, which are satisfying concerning the costs or the separation performance. In this study, we show a chromatographic approach using natural clay minerals as cation exchangers to separate two protein fractions in potato fruit juice. Additionally, the content of glycoalkaloids naturally occurring in potatoes is significantly reduced in a single step together with the separation of the patatins and the protease inhibitors. PMID:22761137

Ralla, Kathrin; Sohling, Ulrich; Suck, Kirstin; Kasper, Cornelia; Ruf, Friedrich; Scheper, Thomas

2012-07-01

127

Wind-blown sandstones cemented by sulfate and clay minerals in Gale Crater, Mars  

NASA Astrophysics Data System (ADS)

Crater contains Mount Sharp, a ~5 km thick stratigraphic record of Mars' early environmental history. The strata comprising Mount Sharp are believed to be sedimentary in origin, but the specific depositional environments recorded by the rocks remain speculative. We present orbital evidence for the occurrence of eolian sandstones within Gale Crater and the lower reaches of Mount Sharp, including preservation of wind-blown sand dune topography in sedimentary strata—a phenomenon that is rare on Earth and typically associated with stabilization, rapid sedimentation, transgression, and submergence of the land surface. The preserved bedforms in Gale are associated with clay minerals and elsewhere accompanied by typical dune cross stratification marked by bounding surfaces whose lateral equivalents contain sulfate salts. These observations extend the range of possible habitable environments that may be recorded within Gale Crater and provide hypotheses that can be tested in situ by the Curiosity rover payload.

Milliken, R. E.; Ewing, R. C.; Fischer, W. W.; Hurowitz, J.

2014-02-01

128

Modern and late Quaternary clay mineral distribution in the area of the SE Mediterranean Sea  

NASA Astrophysics Data System (ADS)

The present-day clay mineral distribution in the southeastern Levantine Sea and its borderlands reveals a complex pattern of different sources and distribution paths. Smectite dominates the suspended load of the Nile River and of rivers in the Near East. Illite sources are dust-bearing winds from the Sahara and southwestern Europe. Kaolinite is prevalent in rivers of the Sinai, in Egyptian wadis, and in Saharan dust. A high-resolution sediment core from the southeastern Levantine Sea spanning the last 27 ka shows that all these sources contributed during the late Quaternary and that the Nile River played a very important role in the supply of clay. Nile influence was reduced during the glacial period but was higher during the African Humid Period. In contrast to the sharp beginning and end of the African Humid Period recorded in West African records (15 and 5.5 ka), our data show a more transitional pattern and slightly lower Nile River discharge rates not starting until 4 ka. The similarity of the smectite concentrations with fluctuations in sea-surface temperatures of the tropical western Indian Ocean indicates a close relationship between the Indian Ocean climate system and the discharge of the Nile River.

Hamann, Yvonne; Ehrmann, Werner; Schmiedl, Gerhard; Kuhnt, Tanja

2009-05-01

129

NMR spectroscopic investigations of surface and interlayer species on minerals, clays and other oxides  

SciTech Connect

The behavior of chemical species adsorbed on solid surfaces and exchanged into clay interlayers plays a significant role in controlling many natural and technologically important processes, including rheological behavior, catalysis, plant growth, transport in natural pore fluids and those near anthropogenic hazardous waste sites, and water-mineral interaction. Adsorption and exchange reactions have been the focus of intense study for many decades. Only more recently, however, have there been extensive spectroscopic studies of surface species. Among the spectroscopic methods useful for studying surface and exchanged species (e.g., infrared, X-ray photoelectron spectroscopy [XPS] and X-ray absorption spectroscopy [XAS]), nuclear magnetic resonance spectroscopy (NMR) has the considerable advantage of providing not only structural information via the chemical shift and quadrupole coupling constant but dynamical information in the Hz-mHz range via lineshape analysis and relaxation rate measurements. It is also possible to obtain data in the presence of a separate fluid phase, which is essential for many applications. This paper illustrates the range of applications of NMR methods to surface and exchanged species through review of recent work from our laboratory on Cs in clay interlayers and Cs, Na and phosphate adsorbed on oxide surfaces. The substrate materials used for these experiments and our long-term objectives are related to problems of geochemical interest, but the principals and techniques are of fundamental interest and applicable to a wide range of technological problems.

Kirkpatrick, R.J.; Yeongkyoo Kim [Univ. of Illinois, Urbana, IL (United States). Department of Geology; Weiss, C.A. [Army Engineer Waterways Experiment Station, Vicksburg, MS (United States). Structures Laboratory; Cygan, R.T. [Sandia National Laboratories, Albuquerque, NM (United States)

1996-07-01

130

Structural charge site influence on the interlayer hydration of expandable three-sheet clay minerals  

USGS Publications Warehouse

Previous investigations have demonstrated the influences of interlayer cation composition, relative humidity, temperature, and magnitude of interlayer surface charge on the interlayer hydration of montmorillonites and vermiculites. It has been suggested that the sites of layer charge deficiencies may also have an influence upon the amount of hydration that can take place in the interlayers of expandable clay minerals. If the interlayer cation-to-layer bonds are considered as ideally electrostatic, the magnitude of the forces resisting expansion may be expressed as a form of Coulomb's law. If this effect is significant, expandable structures in which the charge-deficiency sites are predominantly in the tetrahedral sheet should have less pronounced swelling properties than should structures possessing charge deficiencies located primarily in the octahedral sheet. Three samples that differed in location of layer charge sites were selected for study. An important selection criterion was a non-correlation between tetrahedral charge sites and high surface-charge density, and between octahedral charge sites and low surface-charge density. The effects of differences in interlayer cation composition were eliminated by saturating portions of each sample with the same cations. Equilibrium (001) d values at controlled constant humidities were used as a measure of the relative degree of interlayer hydration. Although no correlation could be made between the degree of interlayer hydration and total surface-charge density, the investigation does not eliminate total surface-charge density as being significant to the swelling properties of three-sheet clay-mineral structures. The results do indicate a correlation between more intense expandability and predominance of charge deficiencies in the octahedral sheet. Conversely, less intense swelling behavior is associated with predominantly tetrahedral charge deficiencies. ?? 1968.

Kerns, Jr. , R. L.; Mankin, C. J.

1968-01-01

131

Removal of organic pollutants in model water and thermal wastewater using clay minerals.  

PubMed

Water treatment method was developed for the removal of different anionic dyes such as methyl orange and indigo carmine, and also for thymol applying sodium bentonite and cationic surfactant - hexadecyltrimethylammonium bromide (HTAB) - or polyelectrolytes (polydiallyldimethylammonium chloride, poly-DADMAC and poly-amines). The removal efficiency of these model substrates was examined in model water using UV-Vis spectrophotometry, HPLC and TOC analysis. The clay mineral and HTAB were added in one step to the polluted model water in Jar-test experiments. The influence of the cation exchange capacity (CEC) of the applied clay mineral and the presence of polyaluminium chloride coagulant (BOPAC) were also tested for the water treatment process. The structures of the in situ produced and pre-prepared organoclay composites were compared by XRD analysis. The rapid formation of organoclay adsorbents provided very efficient removal of the dyes (65-90 % in 3-10 mg/L TOC(0) range) with 200 mg/L sodium bentonite dose, however thymol was less efficiently separated. Adsorption efficiencies of the composites were compared at different levels of ion exchange such as at 40, 60 and 100 %. In the case of thymol, the elimination of inorganic carbon from the model water before the TOC analysis resulted in some loss of the analysed volatile compound therefore the HPLC analysis was found to be the most suitable tool for the evaluation of the process. This one-step adsorption method using in situ formed organoclay was better performing than the conventional process in which the montmorillonite-surfactant composite is pre-preapared and subsequently added to the polluted water. The purification performance of this method was also evaluated on raw and artificially polluted thermal wastewater samples containing added thymol. PMID:21929471

Szabó, Emese; Vajda, Krisztina; Veréb, Gábor; Dombi, András; Mogyorósi, Károly; Ábrahám, Imre; Májer, Marcell

2011-01-01

132

Clay minerals and its influence on soil respiration in southern Brazil  

NASA Astrophysics Data System (ADS)

Carbon dioxide is the greenhouse gas with the highest concentration increases in the last century caused by human activities. Despite all the efforts, new investigations should be conducted in order to understand how agricultural management and its variations would impact on soil respiration and consequently in soils potential for carbon sequestration. Soil iron content is an important aspect of tropical soils, especially in sugarcane fields, that are located in regions where iron content in soil is among the highest concentrations in world. In this work we show that as iron content increases and changes its constitution FCO2 decreases monotonically. A transect was established on an acid oxisol in a direction where soil color changed from a yellow (10 YR), passing to a red (5 YR) and finishing with a dark red latosol (2.5 YR), in just 420 meters. Soil respiration was taken each 10 meters (42 points) while soil samples were extracted (0-20 cm) in each point for further soil property analysis. X-ray analysis shows that the goethite per hematite ratio and kaolinite per gibbsite ratio are directly related to soil respiration rates, and this is confirmed by spectroreflectance analysis performed in the same samples. Also, soils with iron clay minerals having lower degree of cristalinity were the ones having the higher soil respirations. Our study suggests a more complex relationship between clay minerals and biological activity, including soil iron level as an important factor in order to infer the ecological impact of tropical soil management in the biosphere. Due to the distinguishable characteristics of the Brazilian soils in terms of iron level, new experiments are needed to elucidate the relationship of iron content and CO2 loss in different classes of soils.

Marques, José, Jr.; Tadeu Pereira, Gener; La Scala, Newton, Jr.

2010-05-01

133

Simple algorithms for remote determination of mineral abundances and particle sizes from reflectance spectra  

NASA Technical Reports Server (NTRS)

Algorithms were developed, based on Hapke's (1981) equations, for remote determinations of mineral abundances and particle sizes from reflectance spectra. In this method, spectra are modeled as a function of end-member abundances and illumination/viewing geometry. The method was tested on a laboratory data set. It is emphasized that, although there exist more sophisticated models, the present algorithms are particularly suited for remotely sensed data, where little opportunity exists to independently measure reflectance versus article size and phase function.

Johnson, Paul E.; Smith, Milton O.; Adams, John B.

1992-01-01

134

Study on the characteristics of granular clay minerals for the adsorption and recovery of metal ions 2.  

National Technical Information Service (NTIS)

Granular clay mineral(GCM) as new adsorbent for the adsorption and recovery of metal ion in aqueous solution was prepared successfully from various powder-typed Na-bentonite, Ca-bentonite and Kaolinite with high-precision preparation device self-designed ...

C. H. Eum J. T. Park B. I. Choi S. Y. Kim

1995-01-01

135

Sediment dynamics in the Eurasian Arctic Ocean during the last deglaciation — The clay mineral group smectite perspective  

Microsoft Academic Search

This study focuses on sedimentological investigations of sediment cores recovered during the international Arctic?91, expeditions with the German research ice breaker RV “Polarstern” to the European sector of the Arctic Ocean. Here, we deduce the last glacial\\/interglacial changes in transport mechanism and sedimentation from the clay mineral group smectite. We choose the smectites as an example of how sediment mineralogy

Christoph Vogt; Jochen Knies

2008-01-01

136

Is the clogging process in Maqarin natural analogue controlled by accessory clay minerals? A reactive transport study with new data.  

NASA Astrophysics Data System (ADS)

The safety of nuclear waste repositories is based on the functionality of multiple natural and engineered barriers for very long time. The barrier system typically combines geochemically different materials that might interact with each other. One example is the long term alteration of sedimentary host rocks by the interaction with high pH pore water from cement materials used for tunnel support, seals and as backfill material. Within this context the Maqarin site in Jordan was investigated since more than 20 years as a natural analogue for rock alterations and pore clogging due to ingress of high pH solutions. In this work we examine the geochemical evolution of Maqarin marl rock in contact with a fracture through which a hyper-alkaline groundwater is circulating. The new reactive transport calculations were performed with the code OpenGeoSys-GEMS and utilize a state-of-the-art geochemical model for cement-clay interactions. The simulations reveal that the precipitation of ettringite, and to a smaller extent the precipitation of calcium-silicate-hydrate (CSH), is responsible for pore clogging in the rock matrix. Clogging of the pore space effectively seals the rock matrix on a centimeter scale after some hundreds of years and suppresses mass transfer of solutes from the fracture into the adjacent rock. In our Maqarin marl rock model typical clay minerals like kaolinite and illite are present in accessory mineral quantities only. A sensitivity analysis reveals that in this setup clay minerals are the main source for Al, necessary for the formation of ettringite-type solid solutions. It is thus the clay mineral content and the dissolution reactions that to a large degree control the spatial and temporal precipitation of ettringites and the associated pore clogging. Recently collected mineralogy and porosity data will be used to re-calibrate the model and to verify our improved findings that overall Maqarin system is controlled by accessory clay minerals.

Shao, H.; Kosakowski, G.; Berner, U.; Kulik, D.; Mäder, U.; Kolditz, O.

2012-04-01

137

Interplay between cataclasis, clay mineral diagenesis and porosity reduction in deformation bands in unconsolidated arkosic sands  

NASA Astrophysics Data System (ADS)

As a response to tectonic and gravitational stresses, unconsolidated sediments can develop zones of localized deformation, commonly described as deformation bands. These are tabular fault zones in high porosity rocks and sediments characterized by small offsets causing reduction of porosity through grain rotation, translation and fracturing. Classified by deformation mechanism and depth of formation, there are two main types of deformation bands: disaggregation bands, where compaction is achieved only by grain rotation and translation, and cataclastic bands, which show intense grain size reduction by grain fracturing. In various examples the porosity and permeability reduction in these fault zones inhibits the flow of fluids. The timing of deformation band formation relative to diagenesis and fluid migration is relevant in relation to the quality and connectivity of hydrocarbon or groundwater reservoirs. The investigated outcrop in a sandpit near Eisenstadt (Eisenstadt-Sopron Basin, Austria) exposes numerous conjugate deformation bands, which are formed in lower Miocene uncemented, arkosic sands and gravels. These deformation bands formed at shallow burial depth (< 1km) and are kinematically related to the nearby Eisenstadt Fault. This outcrop offers the unique possibility to investigate deformation bands with identical kinematic boundary conditions in highly variable sediments, i.e. with a wide range of different grain sizes from fine sand to coarse gravel, variable porosity and mineral content, different stages of diagenesis and carbonate-free or carbonatic sediments. The fact that cataclasis is one of the dominant mechanisms at these shallow depths (< 1km) is unusual and an exception to most cataclastic bands described in literature. This is probably related to the composition, coarse grain size and the high porosity of the sediments. The coarse host sediment mainly consists of detrital quartz, albite, biotite, sericite, muscovite and metamorphic lithoclasts. The dominant deformation mechanisms and the magnitude of porosity reduction in the carbonate-free lithologies are controlled by the initial mica content, mean grain size, level of alteration and albite content in the host rock. The studied deformation bands show a preferred fracturing of sericitized albite grains and the smearing of micas into the pore space. These processes increase the amount of phyllosilicates in the pore space and facilitate the growth of various authigenic clay minerals like smectite, vermiculite, kaolinite and illite. Because of the changed petrophysical properties the deformation bands show a different diagenetic evolution in comparison with the host rock. We identified 4 steps in the development from a high-porosity host rock to a low porosity deformation band. The measured reduction in porosity by up to 18% is associated with a permeability reduction, reflected in the retention of fluids along the deformation bands with the highest content of authigenic clay minerals.

Lommatzsch, Marco; Exner, Ulrike; Gier, Susanne

2013-04-01

138

Clay Minerals of Suspended Matter and Surficial Sediments of Khor Al-Zubair Estuary, NW Arabian Gulf  

NASA Astrophysics Data System (ADS)

Distribution of clay minerals in the suspended matter and surficial sediments of 36 samples collected from Khor Al-Zubair estuary revealed the presence of montimorillonite, kaolinite, chlorite, illite and palygorskite in wide variations. These variations are interpreted to be due to: different source areas of these minerals, the complex hydrodynamic conditions in the Khor and to flocculation. No regular distribution of clay minerals (except for montimorillonite) was found in the water samples. In the sediments samples montimorillonite and palygorskite showed a trend of increasing values toward the Arabian Gulf, which interpreted to be brought by Shatt Al-Arab River and/or formed diagenetically. Kaolinite and chlorite increased landward due to eolian effect. Illite values showed an increment near Shatt Al-Basrah Canal caused by the sediments brought by the Euphrates River from Hor Al-Hammar Lake.

Al-Mussawy, Sabah N.; Basi, Muzahim A.

1993-02-01

139

Plant Root Responses to Three Abundant Soil Minerals: Silicon, Aluminum and Iron  

Microsoft Academic Search

Silicon (Si), aluminum (Al), and iron (Fe) are the three most abundant minerals in soil; however, their effects on plants differ because they are beneficial, toxic, and essential to plant growth, respectively. High accumulation of silicon in the shoots helps some plants to overcome a range of biotic and abiotic stresses. However, plants vary in their ability to take up

Jian Feng Ma

2005-01-01

140

Determination of mineral abundances in samples from the exploratory studies facility using x-ray diffraction.  

National Technical Information Service (NTIS)

Tuff samples collected from the Exploratory Studies Facility (ESF) were X- rayed to estimate relative mineral abundances. X-ray analysis was performed on sub-samples of specimens collected from both the Single Heater Test (SHT) and Drift Scale Heater Test...

S. Roberts R. Viani

1998-01-01

141

Controls on clay minerals assemblages in an early paleogene nonmarine succession: Implications for the volcanic and paleoclimatic record of extra-andean patagonia, Argentina  

NASA Astrophysics Data System (ADS)

The distribution of the clay minerals of the Banco Negro Inferior-Río Chico Group succession (BNI-RC), a middle Danian-middle Eocene mainly continental epiclastic-pyroclastic succession exposed in the Golfo San Jorge Basin, extra-Andean Patagonia (?46° LS), is assessed in order to determine the possible origin of clay and specific non-clay minerals using X-ray diffraction and scanning electron microscopy analyses. The control over the clay mineralogy of the sedimentary settings, contemporary volcanism, paleoclimate and weathering conditions is considered. A paleoclimatic reconstruction is provided and correlated with the main global warming events that occurred during the early Paleogene. Mineralogical analyses of BNI-RC demonstrate that smectite and kaolin minerals (kaolinite, halloysite and kaolinite/smectite mixed layers) are the main clay minerals, whereas silica polymorphs (volcanic glass and opal) are common non-clay minerals. Throughout the succession, smectite and kaolin minerals are arranged in different proportions in the three clay-mineral assemblages. These show a general vertical trend in which the smectite-dominated assemblage (S1) is replaced by the smectite-dominated assemblage associated with other clays (S2) and the kaolinite-dominated assemblage (K), and finally by S2 up-section. The detailed micromorphological analysis of the clay and non-clay minerals allows us to establish that the origins of these are by volcanic ash weathering, authigenic and pedogenic, and that different stages in the evolution of mineral transformations have occurred. The supply of labile pyroclastic material from an active volcanic area located to the northwest of the study area could have acted as precursor of the authigenic and volcanogenic minerals of the analyzed succession. Diverse fine-grained lithological facies (muddy and tuffaceous facies) and sedimentary settings (coastal swamp and transitional environments, and different fluvial systems) together with variable climate and weathering conditions controlled the mineralogical transformations and the arrangement of clay-mineral assemblages. The paleoclimatic reconstruction suggests a general warm and humid climate. However, the temporal trend of the clay-mineral assemblages, the ratios between smectite and kaolinite and the micromorphological analysis of clay minerals contrasted with evidence from sedimentological analyses suggest a warm and seasonal climate for the basal part of the unit, a warm and humid climate with a relatively more perennial rainfall regime in the middle part of the unit, and a warm and less humid, probably subhumid, climate up-section. Such a reconstruction makes it possible to establish a correlation with some of the hyperthermal events of the Early Paleogene Global Warming (EPGW) and, consequently, constitute one of the most complete time records of the EPGW in South America.

Raigemborn, María Sol; Gómez-Peral, Lucía E.; Krause, Javier Marcelo; Matheos, Sergio Daniel

2014-07-01

142

Orientation and optical properties of methylene blue crystal for better understanding of interactions with clay mineral surface  

NASA Astrophysics Data System (ADS)

The properties of cationic dye Methylene blue (MB) adsorbed on diferent surfaces have been investigated intensively over the years and various models for the orientation of its cations have been proposed (Hang and Brindley, 1970; Bujdak et al., 2003; Li and Zare, 2004; Marr III et al., 1973; Bujdak, 2006).The main objective of this work is to investigate and determine orientation and optical properties of metylene blue crystal upon its crystallization on a glass slate and to use those findings in better understanding of interactions with clay minerals. Cationic dyes have very high affinity for clay surfaces and those interactions are easily detected, therefore these dyes are used to determine several properties of clay surfaces (morphology, layer charge, CEC). For this study, we have selected a group of MB crystal and carried out XRD analysis, polarized absorption spectra measurement (400 - 900 nm) and determination of optical properties (pleochroism, determination of twining and extinction angle) using polarizing microscope. Methylene blue crystals are exhibiting mostly needle like habitus with huge difference in width - length ratio. According to X-ray diffraction it is quite obvious that the y (b) axis is perpendicular to the crystal surface. The x (a) and z (c) axis lie in the crystal plane (010). Crystals exhibit prominent dichroism: from blue (E || elong.) to colorless. In accordance with current interpretation of MB spectra peaks at 647 and 570 nm can be assigned as dimer aggregation and peaks at 475 and 406 nm as higher level of aggregation. All of them exhibit pronounced polarization dependence. The group of peaks at lower energy (700 to 900 nm) do not show significant polarization dependence and they correspond to the J - aggregates. Peak at around 800 nm have been noticed as fluorescence active. In dependence with thickness of the crystals and vibration direction we have observed presence of polysynthetic twinning which can be compared with polysynthetic twinning of feldspar minerals. Final result of molecular polymerization is represented as crystal framework of methylene blue. Model of the MB molecular aggregation in the crystal structure could be used as a way for the interpretation of the thin layer structure and the molecular aggregation on the clay surface. References - Hang P.T. & Brindley G.W., (1970), Clays and Clay Minerals, 18, 203-212. - Bujdak J., Iyi N., Kaneko Y. and Sasai R., (2003), Clay Minerals (2003), 38, 561-572. - Li F. and Zare R.N., (2005), J. Phys. Chem. B 2005, 109, 3330-3333. - Marr III, H.E., Stewart, J.M. and Chiu, M.F., (1973), Acta Cryst. (1973), B29, 847. - Bujdak J., (2006), Applied Clay Science 34 (2006) 58 - 73

Miloševi?, Maja; Logar, Mihovil

2013-04-01

143

Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals  

SciTech Connect

The electrokinetic patterns of four bacterial species (Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae and Candida albicans), and two clay minerals (montmorillonite and kaolinite) in the presence of the chloride salts of the heavy metals, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, and of Na and Mg were determined by microelectrophoresis. The cells and kaolinite were net negatively charged at pH values above their isoelectric points (pI) in the presence of Na, Mg, Hg, and Pb at an ionic strength ([mu]) of 3 [times] 10[sup [minus]4]; montmorillonite has no pI and was net negatively charged at all pH values in the presence of these metals. However, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn at pH values above 5.0 and then at higher pH values, again became negative. The charge of the bacteria and S. cerevisiae also reversed in solutions of Cu and Ni with a [mu] of >3 [times] 10[sup [minus]4], whereas there was no reversal in solutions with a [mu] of <3 [times] 10[sup [minus]4]. The clays became net positively charged when the [mu] of Cu was >3 [times] 10[sup [minus]4] and that of Ni was >1.5 [times] 10[sup [minus]4]. The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite). The pIs of the cells in the presence of the heavy metals were at either higher or lower pH values than in the presence of Na and Mg. Exposure of the cells to the various metals at pH values from 2 to 9 for the short times (ca. 10 min) required to measured the electrophoretic mobility did not affect their viability.

Collins, Y.E.; Stotzky, G. (New York Univ., NY (United States))

1992-05-01

144

Decomposition of clay minerals in model experiments and in soils: Possible mechanisms, rates, and diagnostics (analysis of literature)  

NASA Astrophysics Data System (ADS)

The analysis of model experiments on the dissolution of clay minerals showed that, beginning from a certain moment, this process reaches a steady state and proceeds at a constant rate. The minimum dissolution rate was observed in a neutral environment, where this value varied in the range from n × 10-14- n × 10-12 mol/(m2 s). Under acidic and alkaline conditions, this value increased to n × 10-12 or n × 10-10 mol/(m2s) for most clay minerals. The first stage of the dissolution mechanism involved the formation of protonated (in an acidic environment) and deprotonated (in an alkaline environment) complexes, which destabilized and polarized metal-oxygen (or metal-hydroxyl) bonds in the crystal lattice. At the second stage, the rupture of Si-O and Al-O bonds and the release of these components into the solution occurred at a specific concentration of these complexes, and this stage largely controlled the dissolution rate of the mineral. The presence of organic ligands forming mononuclear polydentate complexes on the surface of the mineral particles at the same solution pH increased the dissolution rate of the minerals by several times and sometimes by an order of magnitude proportionally to the concentration of these complexes on the surface of the particles. It was found that the dissolution rates of kaolinite, illite, and smectite in the podzolic horizon of loamy podzolic soil calculated from the losses of clay minerals in the soil profile with consideration for the soil age exceeded the corresponding values obtained in model laboratory experiments at the same pH values by several orders of magnitude. The revealed differences could be related to the long-term functioning of biota in native soils and the existing uncertainties in the assessment of the active surface of mineral particles.

Sokolova, T. A.

2013-02-01

145

Numerical Simulation of Injectivity Effects of Mineral Scaling and Clay Swelling in a Fractured Geothermal Reservoir  

SciTech Connect

A major concern in the development of hot dry rock (HDR) and hot fractured rock (HFR) reservoirs is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths such as those caused by thermally-induced stress cracking. Past analyses of HDR and HFR reservoirs have tended to focus primarily on the coupling between hydrology (flow), heat transfer, and rock mechanics. Recent studies suggest that rock-fluid interactions and associated mineral dissolution and precipitation effects could have a major impact on the long-term performance of HFR reservoirs. The present paper uses recent European studies as a starting point to explore chemically-induced effects of fluid circulation in HFR systems. We examine ways in which the chemical composition of reinjected waters can be modified to improve reservoir performance by maintaining or even enhancing injectivity. Chemical manipulations considered here include pH modification and dilution with fresh water. We performed coupled thermo-hydrologic-chemical simulations in which the fractured medium was represented by a one-dimensional MINC model (multiple interacting continua), using the non-isothermal multi-phase reactive geochemical transport code TOUGHREACT. Results indicate that modifying the injection water chemistry can enhance mineral dissolution and reduce clay swelling. Chemical interactions between rocks and fluids will change a HFR reservoir over time, with some changes favorable and others not. A detailed, quantitative understanding of processes and mechanisms can suggest chemical methods for reservoir management, which may be employed to improve the performance of the geothermal system.

Xu, Tianfu; Pruess, Karsten

2004-05-10

146

Tectonic?palaeoenvironmental forcing of clay-mineral assemblages in nonmarine settings: the Oligocene?Miocene As Pontes Basin (Spain)  

NASA Astrophysics Data System (ADS)

Two small, alluvial-lacustrine subbasins developed during the early restraining overstep stages of the Oligocene-Miocene As Pontes strike-slip Basin (NW Spain). Later, the basin evolved into a restraining bend stage and an alluvial-swamp-dominated depositional framework developed. The palaeobiological record demonstrates that the Oligocene-Miocene palaeoclimate in NW Spain was subtropical, warm and humid to subhumid. The metamorphic and igneous basin catchment yielded clay assemblages made up by kaolinite, illite and Al-smectite. Illite occurred as an original mineral in the source rock area, whereas kaolinite and Al-smectite resulted mainly from weathering of feldspar and clinochlore, respectively. This detrital primary clay assemblage remained preserved in the colluvial, alluvial fan and shallow lacustrine facies, whose early diagenesis was influenced by diluted, poorly evolved pore waters with neutral to slightly alkaline pH. The original clay assemblage was mildly to strongly transformed under early diagenetic conditions in the lacustrine and swampy environments where significant hydrochemical and Eh-pH changes took place. A fibrous magnesium-rich clay mineral-dominated assemblage (palygorskite and sepiolite) formed in shallow, saline lakes and palustrine zones under the influence of magnesium-rich, alkaline waters. Moreover, kaolinite-enriched assemblages formed in deep lacustrine, swamp and swamp-related alluvial zones under the influence of slightly to highly acidic pore waters. Pore water acidic conditions, characterising environments with organic matter accumulation, led to early diagenetic transformation of Al-smectite into kaolinite. This process was relatively limited in some environments such as organic matter-rich bottoms in meromictic lacustrine zones, whereas it was pervasive in peat-forming swamp zones. The stratigraphic relationships between the diverse clay mineral assemblages in the As Pontes Basin fill demonstrate the coeval development of rather diverse clay compositions. This clearly reflects the influence on clay assemblages of palaeoenvironmental changes forced by the morphological and tectonic evolution of the catchment-basin system. The interplay between climate and tectonic processes in the source areas did not result in major variations of the clay minerals fed into the basin. Conversely, this tectonic-sedimentation interplay influenced the evolution of the drainage and the water balance in the depositional zones, causing a complex environmental-hydrochemical evolution to occur. As a consequence, drastic early diagenetic changes affected the original clay mineral assemblages and resulted in a variety of early diagenetic assemblages. The As Pontes case study emphasises the major influence of palaeogeographical and tectonosedimentary evolution on the clay mineral record in nonmarine depositional systems. The depositional record in As Pontes Basin demonstrates that morphological and tectonically forced environmental and hydrochemical changes can result in variations similar to those forced by low-order climatic changes and that, in some cases, the role of climate can be negligible.

Sáez, A.; Inglès, M.; Cabrera, L.; de las Heras, A.

2003-07-01

147

Clay mineral sedimentation in high northern latitude deep-sea basins since the Middle Miocene (ODP Leg 151, NAAG)  

NASA Astrophysics Data System (ADS)

High-resolution clay mineralogical investigations and their comparison with other sedimentological data from ODP Sites 908 and 909 (central Fram Strait) were used to reconstruct the paleoclimate and paleoceanography in the high northern latitudes since the Middle Miocene. Ice rafting has probably occurred since 15 Ma. The comparison of sand-sized components and clay mineral distribution demonstrate that both were not delivered by the same transport process. The input of the clay fraction is related to transport through sea ice and/or oceanic currents. A provenance change at 11.2 Ma is indicated by variations within clay mineral distribution and increased accumulation rates. This is interpreted as a result of an increase in water mass exchange through the Fram Strait. Decreases of the smectite to illite and chlorite ratio at Site 909 suggest a Middle Miocene cooling phase between 14.8 and 14.6 Ma, and a further cooling phase between 10 and 9 Ma. The intensification of glaciation in the Northern Hemisphere is documented by an increase of illite and chlorite from 3.4 to 3.3 Ma, which is synchronous to the onset of major Northern Hemisphere glaciation as indicated by oxygen isotope data.

Winkler, A.; Wolf-Welling, T.; Stattegger, K.; Thiede, J.

2002-01-01

148

Broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens  

PubMed Central

SYNOPSIS Objectives The capacity to properly address the worldwide incidence of infectious diseases lies in the ability to detect, prevent, and effectively treat these infections. Therefore, identifying and analyzing inhibitory agents are worthwhile endeavors in an era when few new classes of effective antimicrobials have been developed. The use of geological nanomaterials to heal skin infections has been evident since the earliest recorded history, and specific clay minerals may prove valuable in the treatment of bacterial diseases, including infections for which there are no effective antibiotics, such as Buruli ulcer and multi-drug resistant infections. Methods We have subjected two iron-rich clay minerals, which have previously been used to treat Buruli ulcer patients, to broth culture testing of antibiotic-susceptible and -resistant pathogenic bacteria to assess the feasibility of using clay minerals as therapeutic agents. Results One specific mineral, CsAg02, demonstrated bactericidal activity against pathogenic Escherichia coli, extended-spectrum ?-lactamase (ESBL) E. coli, S. enterica serovar Typhimurium, Pseudomonas aeruginosa, and Mycobacterium marinum and a combined bacteriostatic/bactericidal effect against Staphylococcus aureus, penicillin-resistant S. aureus (PRSA), methicillin-resistant S. aureus (MRSA), and Mycobacterium smegmatis, while another mineral with similar structure and bulk crystal chemistry, CsAr02, had no effect on or enhanced bacterial growth. The <0.2 ?m fraction of CsAg02 and CsAg02 heated to 200°C or 550°C retained bactericidal activity, while cation-exchanged CsAg02 and CsAg02 heated to 900°C no longer killed E. coli. Conclusions Our results indicate that specific mineral products have intrinsic, heat-stable antibacterial properties, which could provide an inexpensive treatment against numerous human bacterial infections.

HAYDEL, SHELLEY E.; REMENIH, CHRISTINE M.; WILLIAMS, LYNDA B.

2008-01-01

149

Polyphase metamorphism in the eastern Carnic Alps (N Italy–S Austria): clay minerals and conodont Colour Alteration Index evidence  

Microsoft Academic Search

Thermal evolution of the Palaeozoic–Triassic sequences of the Carnic Alps has been characterized by b cell dimension and Kübler Index (illite “crystallinity”) of K-white micas (KI), Árkai Index (AI) of chlorites, clay mineral\\u000a assemblages and conodont Colour Alteration Index (CAI). Data indicate at least two metamorphic events, Variscan and Alpine.\\u000a In the older event high anchizonal conditions predominated although epizonal

Covadonga Brime; Maria Cristina Perri; Monica Pondrelli; Claudia Spalletta; Corrado Venturini

2008-01-01

150

Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon  

Microsoft Academic Search

Column sorption experiments were conducted at 330°C and 250°C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330°C (r2>0.87), while the sorption

Yuan Gao; Haijun Zhang; Jiping Chen

2010-01-01

151

Stratigraphic and climatic implications of clay mineral changes around the Paleocene\\/Eocene boundary of the northeastern US margin  

Microsoft Academic Search

Kaolinite usually is present in relatively small amounts in most upper Paleocene and lower Eocene neritic deposits of the northern US Atlantic Coastal Plain. However, there is a short period (less than 200,000k.y.) in the latest Paleocene (upper part of calcareous nannoplankton Zone NP 9) when kaolinite-dominated clay mineral suites replaced the usual illite\\/smectite-dominated suites. During this time of global

T. G. Gibson; L. M. Bybell; D. B. Mason

2000-01-01

152

New information on the glacial history of the NW Barents Sea from clay minerals and radiocarbon dates  

NASA Astrophysics Data System (ADS)

Here we present results from new analyses on marine sediment cores that recovered subglacial and postglacial units deposited in the NW Barents Sea during the LGM and the Holocene. We have performed a pilot study on clay-mineral assemblages in three cores collected in palaeo-ice stream troughs surrounding Nordaustlandet (Hinlopen, Erik Eriksen and Kvitøya troughs) to investigate the provenance and pathways of subglacial sediment transported by the Barents Sea Ice Sheet (BSIS) during the LGM and of Holocene marine sediments. In all of the cores there is a clear change in clay mineral composition between the subglacial diamicts and the postglacial muds, and the clay-mineral assemblage in the diamicts is distinctive in each core. This suggests that the clay mineral composition records different pathways of subglacially transported detritus around eastern Svalbard. We interpret these data in relation to local source rocks on the Svalbard archipelago and in the central Barents Sea in order to provide new information regarding the BSIS dynamics during the last glacial period, about which there is still considerable debate for the central-northern Barents Sea sector (cf. Landvik and Ingolfsson, 2013). In addition, new radiocarbon ages from sediment cores around Nordaustlandet suggest that grounded ice had retreated from the shelf break north of Nordaustlandet and in Kvitøya Trough east of Svalbard by 13.3-13.6 14C kyrs BP. This is in line with deglacial dates of 13-13.3 14C kyrs BP from the other major troughs on the northern Barents Sea margin (Saint Anna and Franz Victoria troughs). In Hinlopen Trough our deglacial date confirms that the Polar Front was in the vicinity of the core site on the continental shelf some 20 km landward of the shelf break by 11.0 14C kyrs BP.

Hogan, Kelly; Dowdeswell, Julian; Hillenbrand, Claus-Dieter; Ehrmann, Werner

2014-05-01

153

Controls on detrital sedimentation in the Cariaco Basin during the last climatic cycle: insight from clay minerals  

NASA Astrophysics Data System (ADS)

A high resolution analysis of the clay-mineral content of sediments of the Cariaco Basin spanning the last climatic cycle was performed in order to determine how the detrital sedimentation in the basin records climatic oscillations at various timescales. At the scale of glacial-interglacial cycles, the clay-mineral content records changes in the geographic origin of the detrital supply, from a dominantly kaolinite- and smectite-rich southern source during glacial to a more illite-rich northerly source during interglacials. Though possibly influenced by eustatic variations, these changes mostly reflect the latitudinal fluctuations of the intertropical convergence zone (ITCZ). The Eemian shows an increased contribution from the northern source compared to the Holocene. During MIS3, seasonality modulates the effect of ITCZ position and leads to increased smectite contribution. Fluctuations of the smectite and kaolinite contents during Dansgaard/Oeschger cycles reflect changes of runoff intensity. Enhanced supplies in kaolinite during Heinrich-like events and stadials also suggest remobilizations of sediments deposited on the Unare platform resulting from rapid sea-level variations. The Younger Dryas is characterized by a significantly different clay-mineral association reflecting a drastic modification of terrigenous supply. An eolian contribution would explain this peculiar mineralogy, although local contributions cannot be ruled out. A similar event is noted at the MIS6-5 transition pointing for the occurrence of a Younger Dryas-like episode during Termination II.

Riboulleau, A.; Bout-Roumazeilles, V.; Tribovillard, N.

2014-06-01

154

Li abundances in eclogite minerals: a clue to a crustal or mantle origin?  

Microsoft Academic Search

The mineral phases of 33 eclogite and garnet clinopyroxenite samples from various tectonic settings were analysed for Li by secondary ion mass spectrometry (SIMS). In all samples, Li is preferentially incorporated into clinopyroxene (0.4 to 80 µg\\/g), whereas co-existing garnet contains only minor amounts of Li (0.01 to 3.7 µg\\/g). When present, glaucophane shows Li abundances which are similar to

Alan B. Woodland; Hans-Michael Seitz; Rainer Altherr; Horst Marschall; Bettina Olker; Thomas Ludwig

2002-01-01

155

Mercury: Determining Minerals And Their Abundances With Mid-IR Spectral Deconvolution III  

Microsoft Academic Search

We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W longitude from five slit observations at regions in north-mid and north latitudes. The subtending slit sectors have central coordinates as follows: (1) 11 April 2006#89; 203°W, 13°N 205°W, 47°N (2) 7 April 2006#77; 210°W, 8°N 230°W, 25°N (3) 11 April 2006#96; 212°W, 15°N 219°W, 45°N (4)

Ann L. Sprague; K. Donaldson Hanna; R. W. Kozlowski; J. Helbert; A. Maturilli; F. A. Grosse; T. S. Boop; K. Boccafola

2007-01-01

156

Effects of mineral distribution at mesoscopic scale on solute diffusion in a clay-rich rock: Example of the Callovo-Oxfordian mudstone (Bure, France)  

NASA Astrophysics Data System (ADS)

The mesostructure (millimeter to micrometer scale) of clay-rich sedimentary rocks is generally characterized by a connected fine-grained clay matrix embedding coarser nonclay minerals. We use the Callovo-Oxfordian clay-rich rock formation (France) to illustrate how mesostructure influences solute transfer in clay-rich rocks at larger scales. Using micrometer resolution imaging techniques (SEM and micro-CT) major mineral phases (clay matrix, carbonates, tectosilicates, and heavy minerals) were mapped both in two dimensional (2-D) and three dimensional (3-D) at the mesoscale. Orientation and elongation distributions of carbonate and tectosilicate grains measured on mineral maps reveal an anisotropic mesostructure relative to the bedding plane, in agreement with the geological history of the sedimentary rock. Diffusion simulations were performed based on the 3-D mineral maps using a random walk method thus allowing direct computation of mesoscopic scale-related diffusion anisotropy and tortuosity. Considering an isotropic clay matrix, simulated diffusion anisotropy (1.11-1.26) was found lower than the one experimentally measured on macroscopic samples (1.5 to 2), due to the anisotropy feature of pores within the clay matrix. The effects of the mineral content variations on diffusion properties were then investigated by numerical modifications of a mineral map combined with diffusion simulations. Evolution of the tortuosity and diffusion anisotropy with the clay matrix content were successfully interpreted by the Koponen percolation/diffusion model, whereas the Archie approach fails to reproduce diffusion properties at low clay contents. A comparison of fitting parameters with those obtained experimentally indicates that diffusion coefficient variations observed at a large scale could be mainly controlled by the mesostructure.

Robinet, Jean-Charles; Sardini, Paul; Coelho, Daniel; Parneix, Jean-Claude; Prêt, Dimitri; Sammartino, StéPhane; Boller, Elodie; Altmann, Scott

2012-05-01

157

Geochemical studies of clay minerals III. The determination of free silica and free alumina in montmorillonites  

USGS Publications Warehouse

Determination of free silica by the method proposed made possible the derivation of logical formulas for several specimens of montmorillonites for which the formulas could not be derived from the analyses alone. Other montmorillonites, for which logical formulas could be derived from their analyses, were found to contain small amounts of free silica or free alumina. Others were found to contain neither free silica nor free alumina. The method consists of the following steps: (1) digestion of 1 g of the specimen with 0.5 N NaOH solution in a covered platinum crucible or dish on a steam bath for 4 hrs, stirring the mixture at 30-min intervals, (2) filtration of the undissolved material, followed by washing several times with 1% NaOH solution, (3) neutralization of the filtrate with HCl, addition of 5 ml HCl in excess and determination of SiO and Al2O3 in the usual way and (4) calculation of the amount of free SiO2 or free Al2O3 if any and the amount of attack of the clay structure by the treatment from the ratio of SiO2 to Al2O3 dissolved and the ratio of SiO2 to Al2O3 obtained on analysis. Tests with 5% Na2CO3 solution, the reagent formerly used for the solution of free SiO2 in rocks and minerals, showed that solution of opal by this reagent is always fractional, never complete, no matter how small the amount present or how long the period of treatment. Re-treatment of the sample results in 90-95% solution if 10 mg or less of opal is present, but for larger amounts of opal the percentage dissolved decreases as the amount present increases. On the other hand, 75 ml of 0.5 N NaOH completely dissolves as much as 400 mg of opal in 4 hrs digestion in a covered platinum crucible or dish, on a steam bath. However, a weaker solution or a shorter period of digestion does not effect complete solution. The same amount (75 ml) of 0.5 N NaOH also dissolves 90 mg of cristobalite and 57 mg of quartz having a grain size of less than 2 microns. Use of NaOH also permits determination of the amount of alumina dissolved, and estimation of the extent to which the clay structure was attacked by the treatment. ?? 1953.

Foster, M. D.

1953-01-01

158

Variability of clay-mineral composition on Carolina Slope (NW Atlantic) during marine isotope stages 1^3 and its paleoceanographic signi¢cance  

Microsoft Academic Search

The clay-mineral composition of marine isotope stages 1^3 sediments at the Ocean Drilling program (ODP) Site 1055 on the Carolina Slope consists mainly of illite, kaolinite, chlorite and smectite. Clay-mineral variability is marked by a distinct increase in the relative amounts of kaolinite and smectite during the Holocene and by high illite and to a lesser extent chlorite relative amounts

L. D. Keigwin; N. Okay; E. Sar; O. Algan

2002-01-01

159

Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals  

NASA Astrophysics Data System (ADS)

In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit ?18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The ?18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured ?18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured ?18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the ?18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral-water interactions.

Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

2014-07-01

160

SIMS Analyses for Li Isotope Ratios: From Olivine to Clay Minerals.  

NASA Astrophysics Data System (ADS)

Secondary ion mass spectrometry (SIMS) is an extremely sensitive instrument for Li (up to ~4% of the atoms of Li sputtered from minerals are detected). While precision is high, the accuracy of Li isotope analyses by SIMS is critically dependent on the homogeneity of bulk-analyzed standards. We have used the Cameca ims 3f and 6f SIMS at Arizona State University to analyze crystalline and glassy bulk-analyzed materials and report on their homogeneity and how well the samples compare. We used a 5-20 nA (Ip) primary beam of O- and detected positive secondary ions with 0±20 eV excess kinetic energy. Mass resolving power was sufficient to separate 6LiH from 7Li, but the hydride species was never observed. 7/6 ratios on samples containing 1 ppm Li show precisions of ˜1.3‰ (2 ? ) in a 1 hour analysis. There is a strong positive correlation between Ip and 7/6 ratio in hydrous rhyolite glasses, indicating possible charge-driven Li diffusion. This relation is subtle in low-H basaltic glasses and not observed in olivines and clay minerals. The latter phases show minimal variation in the absolute 7/6 ratio measured by both SIMS instruments over a period of months. Intra-granular Li isotope heterogeneity, apparently related to microstructural imperfections, was observed in some cpx samples, and some olivines from mantle peridotites show strong zoning (>10‰ ). These observations underscore the importance of developing microanalytical techniques of Li isotope analysis. Comparing bulk analyses of San Carlos olivine (Seitz et al., Lithos, in press) with our microanalyses provides a preliminary calibration of the SIMS for 7/6 ratios in olivine. Indirect evidence suggests this calibration applies between Fo80-95. When applied to SIMS analyses of MORB glasses (average ? 7Li ˜+3), the olivine calibration gives a 7/6 ratio ˜4‰ heavier than expected. Using a homogeneous cpx as a standard produces MORB analyses near +3‰ . Whereas studies of more samples are required to understand matrix effects, these appear to be minor for many materials of interest.

Hervig, R. L.; Bell, D. R.; Moore, G.; Williams, L. B.; Yamamoto, J.; Buseck, P. R.

2004-12-01

161

Climatic and stratigraphic implications of clay mineral changes in Paleocene/Eocene boundary strata -- Eastern United States  

SciTech Connect

A major change in the clay mineral suite from predominantly illite/smectite and illite to predominantly kaolinite is present in uppermost Paleocene neritic deposits in the Salisbury embayment of the northeastern US. The clay mineral change occurred during a time of relatively high sea level and is associated with biotic, climatic, and oceanographic changes. This kaolinite increase in middle-latitude areas of the western North Atlantic Ocean, and similar increases in coeval deep-marine sediments off Antarctica and in the eastern North Atlantic Ocean, suggests that intensified weathering due to increased temperature and precipitation was widespread in the latest Paleocene. In the Salisbury embayment, kaolinite proportions rapidly increase from less than 5% in upper Paleocene strata to maximum values of 50 to 60% near the top of the Paleocene (top of calcareous nannofossil Zone NP 9). High kaolinite proportions continue into the lowest Eocene strata (lowermost zone NP 10), but the kaolinite proportion rapidly decreases to 5% or less within the lower part of Zone NP 10. The pattern of kaolinite increasing to maximum values in the latest Paleocene, followed by decreasing values in the earliest Eocene can be used for correlation within the upper Paleocene and lower Eocene units in the Salisbury embayment. On this basis, it is suggested that during the early Eocene, large parts of the uppermost Paleocene and lowermost Eocene clay were eroded from landward parts of the basin.

Gibson, T.G.; Bybell, L.M.; Owens, J.P.; Mason, D.B.; McCartan, L.; Snow, J.N. (Geological Survey, Reston, VA (United States))

1994-03-01

162

Detection of Soluble and Fixed NH4+ in Clay Minerals by DTA and IR Reflectance Spectroscopy : A Potential Tool for Planetary Surface Exploration  

NASA Technical Reports Server (NTRS)

Nitrogen is an essential element for life. It is the only element among the six major biogenic elements, C, O, S, O, P, H, whose presence in the Martian soil has not been positively and directly established. We describe here a study assessing the ability to detect NH4 in soils by two methods: differential thermal analysis (DTA) and infrared (IR) reflectance spectroscopy. Four standard clay minerals (kaolinite, montmorillonite, illite and attapulgite) and an altered tephra sample from Mauna Kea were treated with NH4 in this study. Samples of the NH4-treated and leached clays were analyzed by DTA and infrared (IR) reflectance spectroscopy to quantify the delectability of soluble and sorbed/fixed NH4. An exotherm at 270-280 C was clearly detected in the DTA curves of NH4-treated (non-leached) samples. This feature is assigned to the thermal decomposition reaction of NH4. Spectral bands observed at 1.56, 2.05, 2.12, 3.06, 3.3, 3.5, 5.7 and 7.0 microns in the reflectance spectra of NH4-treated and leached samples are assigned to the sorbed/fixed ammonium in the clays. The montmorillonite has shown the most intense absorbance due to fixed ammonium among the leached samples in this study, as a result of its high cation sorption capacity. It is concluded that the presence of sorbed or fixed NH4 in clays may be detected by infrared (IR) reflectance or emission spectroscopy. Distinction between soluble and sorbed NH4 may be achieved through the presence or absence of several spectral features assigned to the sorbed NH4 moietyi and, specifically, by use of the 4.2 micrometer feature assigned to solution NH4. Thermal analyses furnish supporting evidence of ammonia in our study through detection of N released at temperatures of 270-330 C. Based on these results it is estimated that IR spectra measured from a rover should be able to detect ammonia if present above 20 mg NH4/g sample in the surface layers. Orbital IR spectra and thermal analyses measured on a rover may be able to detect ammonia in soils as well but at higher abundances. The spectral features at 3.06 and 7.0 microns due to bound NH4 in clays and altered Hawaiian tephra appear to be the most promising for detection by orbital spectrometers. If N species are present on Mars the sedimentary deposits may be the best regions to look for them.

Janice, Bishop; Banin, A.; Mancinelli, R. L.; Klovstad, M. R.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

163

Vesta and HED Meteorites: Determining Minerals and their Abundances with Mid-IR Spectral Deconvolution I  

NASA Astrophysics Data System (ADS)

We identify the known mineral compositions and abundances of laboratory samples of Howardite, Eucrite and Diogenite (HED) meteorites (Salisbury et al. 1991, Icarus 9, 280-297) using an established spectral deconvolution algorithm (Ramsey, 1996 Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR 103, 577-596) for mid-infrared spectral libraries of mineral separates of varying grain sizes. Most notably, the spectral deconvolution algorithm fit the known plagioclase and pyroxene compositions for all of the HED meteorite spectra determined by laboratory analysis. Our results for the HED samples, give us a high degree of confidence that our results are valid and that the spectral deconvolution algorithm is viable. Mineral compositions and abundances are also determined using the same technique for one possible HED parent body, Vesta, using mid-infrared spectra that were obtained from ground-based telescopes (Sprague et al. 1993, A.S.P. 41 Lim et al. 2005, Icarus 173, 385-408) and the Infrared Space Observatory (ISO) (Dotto et al. 2000, A&A 358, 1133-1141). Mid-infrared spectra of Vesta come from different areas on its surface. The ISO Vesta spectral deconvolution is suggestive of triolite, olivine, augite, chromite, wollastonite, and sodalite at one location. Modeling of other locations is underway. We also were successful in modeling spectra from locations on the Moon where no Apollo samples are available and for several locations on Mercury's surface using the same techniques (see lunar and mercurian abstracts this meeting). These results demonstrate promise for the spectral deconvolution method to correctly make mineral identifications on remotely observed objects, in particular main-belt asteroids, the Moon, and Mercury. This work was funded by NSF AST0406796.

Hanna, Kerri D.; Sprague, A. L.

2007-10-01

164

Diagenesis of clay mineral assemblages in the Shikoku Basin: Inputs to the Nankai Trough megathrust and seismogenic zone  

NASA Astrophysics Data System (ADS)

One of the essential components of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is to document the composition and diagenetic alteration of sedimentary inputs to the subduction zone of SW Japan. Two sites were drilled seaward of the trench during IODP Expeditions 322 and 333 to demonstrate how those subduction inputs have been influenced by the basement topography of Shikoku Basin. Site C0011 was drilled on the NW flank of Kashinosaki Knoll, and Site C0012 is located near the seamount's summit. The lithostratigraphy expands and condenses from site to site, but the clay mineral assemblages are nearly identical when comparisons are made among coeval units. The early history of sedimentation (middle to late Miocene) was dominated by expandable clay minerals of the smectite group. Contents of smectite in strata older than 5.3 Ma typically exceed 65% of the clay-size fraction, and there are dozens of bentonite layers (altered volcanic ash) interbedded with the hemipelagic mudstones and turbidites. Those percentages amount to >45 wt-% smectite in the bulk mudstone. Volcanic sources for the Miocene clay probably included the ancestral Izu-Bonin island arc, the Izu-Honshu collision zone, and anomalous near-trench magma bodies in the Outer Zone of Honshu and Shikoku Island. As sedimentation progressed into the Pliocene and Pleistocene, mud supplies to the Shikoku Basin shifted increasingly to detrital illite and chlorite eroded from the uplifted accretionary complex (Outer Zone). At Site C0011, the younger hemipelagic-pyroclastic facies (upper Shikoku Basin) contains an average of 43% smectite, 36% illite, and 18% kaolinite + chlorite in the clay-size fraction. At Site C0012, comparable values are S = 51%, I = 32%, and K+C = 14%. XRD results show no evidence of smectite-to-illite diagenesis seaward of the trench, although it is important to note that Site C0011 was abandoned before reaching basaltic basement. We can predict the extent of smectite-to-illite diagenesis using simple kinetic models that account for differences in heat flow from the flank to the summit of Kashinosaki Knoll and rapid burial of Shikoku Basin facies beneath the Quaternary trench wedge. Our modeling results support the notion that illitization does not progress to detectable levels (>20% I in mixed-layer clay) until after the Shikoku Basin deposits are subducted beneath the frontal megathrust. That absence of pre-subduction diagenesis is important to consider when assessing the potential for fluid production and fluid overpressures deeper down-dip along the megathrust, as well as for identifying the potential sources for freshening of interstitial fluids.

Underwood, M.; Guo, J.; Song, C.

2012-12-01

165

[Influence of clay minerals on the oxidative activity of the caprolactam destructors Bacillus subtilis 6 and 21].  

PubMed

By the Warburg manometric method the respiratory activity of the caprolactam destructors--Bacillus subtilis strains 6 and 21 was measured. The bacteria grown on the synthetic nutrient medium with caprolactam as the sole source of carbon and nitrogen oxidized that substrate more intensively than the cells grown on meat-peptone agar. The activity of caprolactam oxidation by the cultures showed strain differences. Clay minerals--montmorillonit, palygorskit, bentonit and vermiculit--stimulated the glucose and caprolactam oxidation by the above bacteria. The highest stimulating effect was produced by montmorillonit. PMID:813198

Rotmistrov, M N; Stavskaya, S S; Garbara, S V; Cvozdyak, P I

1975-01-01

166

Clay Mineral Assemblages from Nankai Trough and Kumano Basin, IODP Expeditions 315 and 316, NanTroSEIZE Stage 1  

NASA Astrophysics Data System (ADS)

As part of the NanTroSEIZE Project (IODP Expeditions 315 and 316), the clay mineral assemblages from 689 samples of hemipelagic mud were characterized by X-ray diffraction. We used oriented aggregates of clay-size fractions to estimate the relative percentages of smectite, illite, chlorite, kaolinite, and quartz. The saddle/peak method was used to show the bulk character of illite/smectite mixed layers. Among all of the clay constituents, smectite content displays the most significant variations across the NanTroSEIZE transect, ranging from 6 to 66%. Compositional changes in the slope apron, accretionary prism, and forearc basin occur largely in response to differences in depositional age. As documented elsewhere on the Nankai margin, the detrital clays shifted gradually from a smectite-rich assemblage during the Miocene to more illite-chlorite rich assemblages during the Pliocene-Pleistocene. In the Kumano forearc basin (Site C0002) and nearby Site C0001, smectite increases abruptly across the basal unconformity into the top of the accretionary prism, from averages of 20% to 40%. At Site C0004 (megasplay fault), a fault-bounded package and underthrust “slope apron” facies in the footwall have the same smectite content (35% average) as older prism strata in the hanging wall of the megasplay. Higher in the hanging wall, a mass-transport complex and uppermost accretionary prism both show lower smectite contents (20% in average), similar to coeval strata in the hanging wall of the frontal thrust (Sites C0006 and C0007). There is no evidence to indicate that any of the shallow faults change stratigraphic position or geometry in response to sediment composition. The expandability of the smectite ranges from 51% to 77% (mean = 65%), with no systematic depth-dependent trends. Therefore, most of the expandable clay is probably detrital in origin with small amounts of inherited interlayered illite. Expandability in the frontal prism decreases across the boundary between accreted trench-wedge and upper Shikoku Basin facies (USB), perhaps in reaction to incipient clay diagenesis. The absence of appreciable shallow-level I/S diagenesis carries important implications for clay dehydration, fluid production, and fluid pressure at greater depths, particularly near the up-dip limit of the seismogenic zone.

Guo, J.; Underwood, M.; Hillix, D.; Wu, H.; Banno, H.; Shriniwar, U.

2009-12-01

167

Mercury: Determining Minerals And Their Abundances With Mid-IR Spectral Deconvolution III  

NASA Astrophysics Data System (ADS)

We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W longitude from five slit observations at regions in north-mid and north latitudes. The subtending slit sectors have central coordinates as follows: (1) 11 April 2006#89; 203°W, 13°N 205°W, 47°N (2) 7 April 2006#77; 210°W, 8°N 230°W, 25°N (3) 11 April 2006#96; 212°W, 15°N 219°W, 45°N (4) 11 April 2006#93; 225°W, 13°N 237°W, 45°N (5) 11 April 2006#109; 262°W, 8°N, 267°W, 25°N. Our results are obtained by modeling spectra obtained with the Mid-Infrared Spectrometer and Imager (MIRSI) at the Infrared Telescope Facility (IRTF) using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR). We have assembled several mineral libraries (JHU, Salisbury et al. 1991; JPL, http://speclib.jpl.nasa.gov; RELAB, http://www.planetary brown.edu/relab; ASU, http://speclib.asu.edu; BED, Maturilli et al. 2007, LPSC XXXVIII Abs.) consisting of a wide range of known mineral compositions with grain sizes ranging from the finest separates, 0 - 45 µm, incrementally increasing to 250 - 400 µm. Surface mineral deconvolutions are suggestive of albite, enstatite, clinopyroxene, labradorite, and sodalite, mineral phases that have been previously observed in the mid-infrared at Mercury (Sprague et al. 1994, 1998, Icarus). The deconvolution also identified pigeonite at more than one location. The same techniques and computer program have correctly fit the known compositions of the HED samples, and given a plausible fit to spectra from the Moon (both also presented at this meeting). This work was funded by NSF AST0406796.

Sprague, Ann L.; Donaldson Hanna, K.; Kozlowski, R. W.; Helbert, J.; Maturilli, A.; Grosse, F. A.; Boop, T. S.; Boccafola, K.

2007-10-01

168

Adsorption of coliphages T1 and T7 to clay minerals.  

PubMed Central

Coliphages T1 and T7 of Escherichia coli were absorbed by kaolinite (K) and montmorillonite (M). Maximum adsorption of T7 (96%) to M was greater than that of T1 (84%), but the adsorption of both coliphages to K was the same (99%). Positively charged sites (i.e., anion exchange sites) on the clays appeared to be primarily responsible for the adsorption of T1 to K but only partially responsible for the adsorption of T1 to M; equilibrium adsorption isotherms of T1 to K and M did not show a correlation between adsorption and the cation exchange capacity of the clays, and the reduction in adsorption caused by sodium metaphosphate (a polyanion that interacts with positively charged sites on clay) was more pronounced with K than with M. The equilibrium adsorption isotherms of T7 to K and M suggested a correlation between adsorption and the cation exchange capacity of the clays. However, studies with sodium metaphosphate indicated that T7 also adsorbed to positively charged sites on the clays, especially on K. Adsorption of the coliphages to positively charged sites was greater with K than with M, probably because the ratio of positively charged sites to negatively charged sites was greater on K than on M.

Schiffenbauer, M; Stotzky, G

1982-01-01

169

New aluminium-rich alkali slag matrix with clay minerals for immobilizing simulated radioactive Sr and Cs waste  

NASA Astrophysics Data System (ADS)

A new aluminium-rich alkali-activated slag matrix (M-AAS) with clay absorbents has been developed for immobilization of simulated radioactive Sr or Cs waste by introducing metakaolin, natural zeolite and NaOH-treated attapulgite clay minerals into alkali-activated slag matrix (AAS). The results revealed that the additions of metakaolin and clay absorbents into the cementitious matrixes would greatly enhance the distribution ratio, Rd, of selective adsorption whether the matrix was OPC matrix or AAS matrix. The new immobilizing matrix M-AAS not only exhibited the strongest selective adsorption for both Sr and Cs ions, but also was characterized by lower porosity and small pore diameter so that it exhibited the lowest leaching rate. Hydration product analyses also demonstrated that (Na+Al)-substituted C-S-H(I) and self-generated zeolite were major hydration products in the M-AAS matrix, which provided this new immobilizing matrix with better selective adsorption on Sr and Cs and lower leaching rate.

Qian, Guangren; Sun, Darren Delai; Tay, Joo Hwa

2001-12-01

170

Anomalous small angle x-ray scattering studies of heavy metal ion solvation behavior in clay minerals  

SciTech Connect

The authors have exploited anomalous small angle x-ray scattering (ASAXS) to monitor the solvation behavior of Cu(II), Er(III) and Yb(III) ions within the interlayers of the natural aluminosilicate clay mineral montmorillonite. The ASAXS technique can reveal the distribution of specific metallic species within a heterogeneous and disordered matrix. The variations of signal intensity as a function of absorption energy were monitored for all of the metal-clays as a function of hydration. Two different hydration levels were probed: as prepared at ambient conditions, or so-called {open_quotes}dry{close_quotes} powders, and {open_quotes}wet{close_quotes} pastes. ASAXS intensities should increase with absorption energy if the metal ion is associated with the interlayer solvent (water in this case), and decrease if the metal ion is associated with the solid matrix. The results show that: (1) Cu(II) is solvated within the interlayers of the wet sample, as expected, and (2) Er(III) and Yb(III) decrease in ASAXS intensity with increased hydration. This latter result was not expected and there is speculation that these ions have associated as hydrolyzed products with the clay surface. The basic principles underlying SAXS and ASAXS will also be presented in this paper.

Carrado, K.A.; Thiyagarajan, P.; Winans, R.E.; Song, Kang [Argonne National Lab., IL (United States)

1997-09-01

171

Clay mineral distribution in surface sediments of the South China Sea and its significance for in sediment sources and transport  

NASA Astrophysics Data System (ADS)

Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials, and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining surface sediment sources and their transport routes will not only improve understanding of modern transportation and depositional processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS.

Liu, Jianguo; Chen, Muhong; Chen, Zhong; Yan, Wen

2010-03-01

172

Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon.  

PubMed

Column sorption experiments were conducted at 330°C and 250°C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330°C (r(2)>0.87), while the sorption isotherm of HCB vapor on AC at 330°C was in the shape of Brunauer type-II adsorption. Catalytic dechlorination of HCB was found to occur on the surface of fly ashes, and pentachlorobenzene was the only dechlorination product detected in the effluent gas. Increasing temperature decreased the sorption of HCB vapor on fly ashes, and promoted the catalytic dechlorination of HCB. On the assumption that the organic carbon and clay minerals in fly ash were derived from AC, kaolinite and montmorillonite, the relative contributions of these components to the apparent sorption capacity of fly ashes at 330°C were estimated. It was found that very small percentage of AC contributed the most to the apparent sorption of HCB vapor on fly ash. The sorption coefficient of HCB on montmorillonite at 250°C was 37 times higher than that at 330°C, suggesting montmorillonite could be a kind of low-cost sorbent to effectively reduce the emission of vapor-phase organochlorine compounds from MSW incinerators. PMID:20875668

Gao, Yuan; Zhang, Haijun; Chen, Jiping

2010-11-01

173

Clay-mineral and grain-size distributions in surface sediments of the White Sea (Arctic Ocean): indicators of sediment sources and transport processes  

Microsoft Academic Search

In this study, the grain-size and clay-mineral compositions of 73 surface sediment samples collected in a variety of environmental\\u000a settings in the White Sea are presented to characterize recent sedimentation processes, reconstruct transport pathways, and\\u000a identify potential source areas of the terrigenous components. Areas >100 m deep are invariably characterized by silty clay,\\u000a whereas areas <100 m deep exhibit more heterogeneous grain-size

Cornelia Saukel; Rüdiger Stein; Christoph Vogt; Vladimir P. Shevchenko

2010-01-01

174

The Moon: Determining Minerals and their Abundances with Mid-IR Spectral Deconvolution II  

NASA Astrophysics Data System (ADS)

We determine the mineral compositions and abundances at three locations on the lunar surface using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR 103, 577-596) for mid-infrared spectral libraries of mineral separates of varying grain sizes. Spectral measurements of the lunar surface were obtained at the Infrared Telescope Facility (IRTF) on Mauna Kea, HI with Boston University's Mid-Infrared Spectrometer and Imager (MIRSI). Our chosen locations, Aristarchus, Grimaldi and Mersenius C, have been previously observed in the VIS near-IR from ground-based telescopes and spacecraft (Zisk et al. 1977, The Moon 17, 59-99; Hawke et al. 1993, GRL 20, 419-422; McEwen et al. 1994, Science 266, 1858-1862; Peterson et al. 1995, 22, 3055-3058; Warell et al. 2006, Icarus 180, 281-291), however there are no sample returns for analysis. Surface mineral deconvolutions of the Grimaldi Basin infill are suggestive of anorthosite, labradorite, orthopyroxene, olivine, garnet and phosphate. Peterson et al. (1995) indicated the infill of Grimaldi Basin has a noritic anorthosite or anorthositic norite composition. Our spectral deconvolution supports these results. Modeling of other lunar locations is underway. We have also successfully modeled laboratory spectra of HED meteorites, Vesta, and Mercury (see meteorites and mercurian abstracts this meeting). These results demonstrate the spectral deconvolution method to be robust for making mineral identifications on remotely observed objects, in particular main-belt asteroids, the Moon, and Mercury. This work was funded by NSF AST406796.

Kozlowski, Richard W.; Donaldson Hanna, K.; Sprague, A. L.; Grosse, F. A.; Boop, T. S.; Warell, J.; Boccafola, K.

2007-10-01

175

Characterization of oil sands mineral components and clay-organic complexes  

SciTech Connect

Differences in oil sands processibility and extraction yields can be dependent upon many factors including the composition of the mineral components and the organic complexes that are associated with certain minerals. These mineral-organic associations help provide the bridge which leads to carry over of bitumen with the tailings as well as carry over of water and mineral matter with product. The nature of these complexes has been studied with nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) as well as other techniques such as thermogravimetric analysis. The relationship of these measurements to processibility and the relevance of conventional oil sands structural modes are discussed.

Axelson, D.E.; Mikula, R.J.

1988-06-01

176

Pathways of clay mineral transport in the coastal zone of the Brazilian continental shelf from Ceará to the mouth of the Amazon River  

NASA Astrophysics Data System (ADS)

The transport pathways of fine sediments (fraction <2 ?m) along the Brazilian continental shelf from Ceará to the Amazon River mouth were studied by means of clay mineral analyses. On the continental shelf southeast of the Amazon mouth, fluctuations in clay mineral compositions reflect simple mixing between the suspended load of the North Brazil Current and sediment from several smaller rivers. Previously, clay mineral variations west of the Amazon mouth have been explained by variable settling velocities of different grain-size classes within the <2 ?m fraction or by selective coagulation of individual clay mineral groups. By contrast, our experiments with river bank samples show that selective coagulation does not occur in Amazon River sediments. A more appropriate explanation for observed variations in clay mineral composition off the Amazon mouth seems to be, similarly to that for the shelf between Ceará and the Amazon mouth, a mixing of Amazon sediments with suspended material of the North Brazil Current. This interpretation is supported by data on clay mineral composition east and south of the Amazon mouth, showing more affinity to sediments of the North Brazil Current than to the suspended load of the Amazon River. Additionally, relatively low sedimentation rates and low concentrations of fine-grained sediments on the shelf suggest that high riverine input by the Amazon River does not overprint the sediments of the North Brazil Current in this region. The strong North Brazil Current shunts the Amazon suspended load in a north-westerly direction along the north-eastern coast of South America. Hence, stronger sedimentation of Amazon sediments would occur only west of the river mouth.

de Morais, J. O.; Tintelnot, M.; Irion, G.; Souza Pinheiro, L.

2006-03-01

177

Clay-mineral and grain-size distributions in surface sediments of the White Sea (Arctic Ocean): indicators of sediment sources and transport processes  

NASA Astrophysics Data System (ADS)

In this study, the grain-size and clay-mineral compositions of 73 surface sediment samples collected in a variety of environmental settings in the White Sea are presented to characterize recent sedimentation processes, reconstruct transport pathways, and identify potential source areas of the terrigenous components. Areas >100 m deep are invariably characterized by silty clay, whereas areas <100 m deep exhibit more heterogeneous grain-size compositions plausibly explained by coastal erosion and (re-)distribution mechanisms, particularly tidal currents. The dominance of sand in the estuarine areas of the Onega and Dvina rivers as well as toward the Gorlo Strait connecting the White Sea with the Barents Sea is attributed to increased current speeds. Illite and smectite are the dominant clay minerals in recent sediments of the southwestern and eastern White Sea sectors, respectively. Their distribution patterns largely depend on the geology of the source areas, and mirror surface circulation patterns, especially in Dvina Bay. Smectite is a key clay mineral in White Sea surface sediments, as it reveals the dominating influence of the Northern Dvina's runoff on sedimentation and water circulation throughout the basin. In comparison to other Eurasian shelf seas, the White Sea is characterized by a greater diversity of clay-mineral assemblages, which range from illite- to smectite-dominated sectors containing variable amounts of chlorite and kaolinite.

Saukel, Cornelia; Stein, Rüdiger; Vogt, Christoph; Shevchenko, Vladimir P.

2010-12-01

178

Effect of chlorine in clay-mineral specimens prepared on silver metal-membrane mounts for X-ray powder diffraction analysis  

USGS Publications Warehouse

Silver metal-membrane filters are commonly used as substrates in the preparation of oriented clay-mineral specimens for X-ray powder diffraction (XRD). The silver metal-membrane filters, however, present some problems after heat treatment if either the filters or the samples contain significant amounts of chlorine. At elevated temperature, the chloride ions react with the silver substrate to form crystalline compounds. These compounds change the mass-absorption coefficient of the sample, reducing peak intensities and areas and, therefore, complicating the semiquantitative estimation of clay minerals. A simple procedure that eliminates most of the chloride from a sample and the silver metal-membrane substrate is presented here.

Poppe, L. J.; Commeau, J. A.; Pense, G. M.

1989-01-01

179

Origin and diagenesis of clay minerals in relation to sandstone paragenesis: An example in eolian dune reservoirs and associated rocks, Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming  

Microsoft Academic Search

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in

R. M. Pollastro; C. J. Schenk

1991-01-01

180

NovaSil clay does not affect the concentrations of vitamins A and E and nutrient minerals in serum samples from Ghanaians at high risk for aflatoxicosis  

Microsoft Academic Search

To assess the potential interference of NovaSil (NS) clay with micronutrients in humans, vitamins A and E and minerals (15 nutrient and 15 non-nutrient minerals) were measured in serum samples from a 3-month intervention trial with NS. Participants (n?=?177) were randomly divided into three groups that received 3.0 g NS day (high dose, HD), 1.5 g NS day (low dose,

E. Afriyie-Gyawu; Z. Wang; N.-A. Ankrah; L. Xu; N. M. Johnson; L. Tang; H. Guan; H. J. Huebner; P. E. Jolly; W. O. Ellis; R. Taylor; B. Brattin; D. Ofori-Adjei; J. H. Williams; J.-S. Wang; T. D. Phillips

2008-01-01

181

Polyphase metamorphism in the eastern Carnic Alps (N Italy-S Austria): clay minerals and conodont Colour Alteration Index evidence  

NASA Astrophysics Data System (ADS)

Thermal evolution of the Palaeozoic-Triassic sequences of the Carnic Alps has been characterized by b cell dimension and Kübler Index (illite “crystallinity”) of K-white micas (KI), Árkai Index (AI) of chlorites, clay mineral assemblages and conodont Colour Alteration Index (CAI). Data indicate at least two metamorphic events, Variscan and Alpine. In the older event high anchizonal conditions predominated although epizonal conditions were reached over wide areas. It was characterized by low-intermediate pressure facies. The thermal peak was mainly due to an extensional regime during the Bashkirian. A younger thermal overprint generated by Alpine orogeny was of lower grade, reaching high diagenetic-anchizonal conditions characterized by high-pressure facies. Inverted metamorphic patterns are associated with middle to late Miocene thrusting. Hydrothermal alteration in the northern part of the region can be linked with emplacement of Oligocene plutons and high heat flow along the Periadratic lineament.

Brime, Covadonga; Perri, Maria Cristina; Pondrelli, Monica; Spalletta, Claudia; Venturini, Corrado

2008-11-01

182

Contribution of the Study of Clay Minerals in Soils from Loesses (Przyczynek Do Poznania Mineralow Ilastych W Glebach Wytworzonych Z Lessow).  

National Technical Information Service (NTIS)

Clay minerals may be treated as indexes of soil fertility determining the size of the sorption complex and also indexes of the stage of weathering and the course and subsequence of soil-forming processes, since the geological and soil processes lead - wit...

K. Konecka-Betley

1970-01-01

183

Weathering and clay mineral formation in two Holocene soils and in buried paleosols in Tadjikistan: towards a Quaternary paleoclimatic record in Central Asia  

Microsoft Academic Search

The upper part of the Karamaydan section, Tadjikistan, shows the most detailed loess–paleosol sequence yet known for the Brunhes chron, and the central and lower parts of the Chashmanigar section provide similar detail for most of the Matuyama chron. To enable paleoclimates to be deduced, the primary and secondary minerals in the silt and clay fractions must be determined separately

A. Bronger; R. Winter; S. Sedov

1998-01-01

184

Cesium and Strontium Uptake to Clay Minerals and Their Weathering Products in a Caustic Waste  

SciTech Connect

Weathering behavior and contaminant (Sr and Cs) uptake by specimen clays (illite, vermiculite, montmorillonite and kaolinite) and their secondary solid phase products were studied in batch systems under geochemical conditions characteristic of leaking tank waste at the Hanford Site in WA (0.05 M AlT, 2 M Na+, 1 M NO3 -, pH {approx}14, Cs+ and Sr2+ present as co-contaminants). Time series experiments were conducted from 0 to 369 days, with initial Cs+ and Sr2+ concentrations ranging from 10-5 to 10-3 M. Cesium sorption after 369 d reaction was the greatest in the order of vermiculite, illite, montmorillonite and kaolinite at 10-3 M Cs/Sr. In the case of Sr, vermiculite showed highest Sr sorption and was followed by kaolinite, montmorillonite and illite at highest loading Cs/Sr after 369 d. Secondary phase products were feldspathoid sodium aluminum nitrate silicate, sodium aluminum nitrate silicate hydrate, Na-Al chabazite and zeolite X in weathered clays. Discrete Sr single phases were found in kaolinite and illite systems after 369 d at 10-3 M Cs/Sr.

Choi, Sunkyung; Amistadi, Mary Kay; Seraphin, Supapan; Chorover, Jon

2004-03-28

185

Stratigraphic and climatic implications of clay mineral changes around the Paleocene/Eocene boundary of the northeastern US margin  

USGS Publications Warehouse

Kaolinite usually is present in relatively small amounts in most upper Paleocene and lower Eocene neritic deposits of the northern US Atlantic Coastal Plain. However, there is a short period (less than 200,000 k.y.) in the latest Paleocene (upper part of calcareous nannoplankton Zone NP 9) when kaolinite-dominated clay mineral suites replaced the usual illite/smectite-dominated suites. During this time of global biotic and lithologic changes, kaolinite increased from less than 5% of the clay mineral suite to peak proportions of 50-60% of the suite and then returned to less than 5% in uppermost Paleocene/lowermost Eocene strata. This kaolinite pulse is present at numerous localities from southern Virginia to New Jersey. These sites represent both inner and middle neritic depositional environments and reflect input from several river drainage systems. Thus, it is inferred that kaolinite-rich source areas were widespread in the northeastern US during the latest Paleocene. Erosion of these source areas contributed the kaolinite that was transported and widely dispersed into shelf environments of the Salisbury embayment. The kaolinite increase, which occurred during a time of relatively high sea level, probably is the result of intensified weathering due to increased temperature and precipitation. The southern extent of the kaolinite pulse is uncertain in that uppermost Paleocene beds have not been identified in the southern Atlantic Coastal Plain. The late Paleocene kaolinite pulse that consists of an increase to peak kaolinite levels followed by a decrease can be used for detailed correlation between more upbasin and more downbasin sections in the Salisbury embayment. Correlations show that more upbasin Paleocene/Eocene boundary sections are erosionally truncated. They have varying portions of the kaolinite increase and, if present at all, discontinuous portions of the subsequent kaolinite decrease. As these truncated sections are disconformably overlain by lower Eocene strata, rapid erosional removal of large parts of the most kaolinite-rich P/E boundary clay deposits occurred by early Eocene time. Erosion of the kaolinite-rich P/E boundary beds was enhanced during times of sea-level fall when kaolinite-rich sediments were redeposited to produce kaolinite spikes in basal beds of lower and middle Eocene sequences that have little or no kaolinite elsewhere in the sequence. In contrast, more downbasin sites document only the upper, decreasing part of the kaolinite pulse. The absence of strata documenting the earlier kaolinite increase is attributed to slow sedimentation (condensed interval) as a result of a significant sea level rise that ponded most sediments in shallower waters, combined with the probable subsequent erosional removal of these thin downbasin deposits by oceanic currents.

Gibson, T. G.; Bybell, L. M.; Mason, D. B.

2000-01-01

186

Nature of the changes in clay minerals of the high temperature drilling fluids  

SciTech Connect

The mineral reactions in the sepiolite and palygorskite-based drilling fluids were systematically examined with X-ray diffraction and analytical electron microscopy before and after hydrothermal treatments. Both sepiolite and palygorskite were converted into smectites and other mineral phases in fluids containing either chlorides or hydroxides. The conversion rate usually increased with increasing temperature. Below 600/sup 0/F, the smectite occurred as thin films with irregular outlines with a high layer charge, whereas discs or platelets with hexagonal outlines were formed above 600/sup 0/F. The conversion of sepiolite (or palygorskite) to smectite at low temperatures (< 600/sup 0/F) was accomplished through epitaxial growth of smectite films around sepiolite (or palygorskite) fibers. At higher temperatures (> 600/sup 0/F), smectites and other new mineral phases were formed through a dissolution-precipitation mechanism. Smectite formed from sepiolite was chemically and structurally a trioctahedral variety; however, smectite formed in the palygorskite fluids consisted of trioctahedral and di-trioctahedral phases. The ditrioctahedral phase with approximately equal amounts of Al and Mg in the octahedral sheets was an unusual reaction product. The rheological properties of the fluids such as viscosity and fluid loss, were related to the mineralogical changes at elevated temperatures. The formation of smectite platelets, discs, and other new mineral phases obviously exerted a detrimental effect on the rheology of the fluids.

Lee, L.J.

1984-01-01

187

Clay mineral contribution from various provenances in the northern South China Sea over the past 400 kyr: implications for the East Asian monsoon evolution  

NASA Astrophysics Data System (ADS)

Clay mineralogy of Core MD12-3432 taken at 2125 m water depth (CIRCEA cruise on board the R.V. Marion Dufresne, IPEV) in the northern South China Sea was investigated in order to understand the time series contribution of terrigenous sediments from various provenances. With calibration of a low-resolution analysis on carbonate concentration and major elements, we converted the XRF core scanned calcium data into a high-resolution carbonate content records. Through referring to the well-dated carbonate record of nearby Core MD05-2904, we established a reliable age model, indicating about 400 kyr ago at the bottom of Core MD12-3432. The clay mineral assemblage is dominated by smectite (23-59%) and illite (22-43%), with minor chlorite (13-27%) and kaolinite (4-13%). The time series variation of clay mineral assemblages indicates strong glacial-interglacial cyclicity. In general, the variation in smectite content is similar to that of carbonate concentration, with higher values during interglacials than during glacials, while illite and chlorite contents showing opposite patterns. The change in kaolinite content shows an independent pattern with high values during glacials, corresponding well with the illite crystallinity variation. The provenance analysis of these clay minerals suggests three end-member sources: all smectites derive from Luzon, all kaolinites originate from the Pearl River, and illite and chlorite are coming from both the Pearl River and Taiwan. Using the linear separation method of illite crystallinity, a time series of the clay mineral contribution from the three major provenances to the northern South China Sea was reconstructed. Combined with spectral analyses, we suggest the clay mineral contribution from Pearl River was mainly influenced by sea level change, while the East Asian summer monsoon controlled the contribution from Luzon. The strong precipitation rate related to intensive East Asian summer monsoon would have enhanced the denudation and intensified the delivery of terrigenous materials from Luzon to the South China Sea. Though Taiwan is also suffering from the monsoon rainfall, the major sediment discharge is caused by strong activities like typhoon rather than average precipitation. Thus, the glacial-interglacial variation in the clay mineral contribution from Luzon indicates the East Asian monsoon evolution. This work is presently conducted in the framework of the Franco-Chinese LIA-MONOCL.

Chen, Quan; Liu, Zhifei; Xie, Xin; Kissel, Catherine

2014-05-01

188

Clay mineral and zeolite diagenesis in the Toa Baja Well, Puerto Rico  

NASA Astrophysics Data System (ADS)

Several diagenetic reactions typical of volcaniclastic sediments have been identified in the Toa Baja well. The zeolites heulandite and (less commonly) analcite, present in the upper half of the drilled section, give way to laumontite at depth. A decrease with depth in the expandability of mixed layer chlorite/smectite was observed. Corrensite was detected over the depth range 1676-2286 m. Temperatures implied by the depth ranges of diagenetic and indicator minerals are consistent with a paleothermal gradient of about 30-50°C/km, assuming little or no erosion of section.

Tribble, Jane S.

189

Reduction and long-term immobilization of technetium by Fe(II) associated with clay mineral nontronite  

SciTech Connect

99Tc is formed mostly during nuclear reactions and is released into the environment during weapons testing and inadvertent waste disposal. The long half-life, high environmental mobility (as Tc(VII)O4-) and its possible uptake into the food chain cause 99Tc to be a significant environmental contaminant. In this study, we evaluated the role of Fe(II) in biologically reduced clay mineral, nontronite (NAu-2), in reducing Tc(VII)O4- to poorly soluble Tc(IV) species as a function of pH and Fe(II) concentration. The rate of Tc(VII) reduction by Fe(II) in NAu-2 was higher at neutral pH (pH 7.0) than at acidic and basic pHs when Fe(II) concentration was low (< 1 mmol/g). The effect of pH, however, was insignificant at higher Fe(II) concentrations. The reduction of Tc(VII) by Fe(II) associated with NAu-2 was also studied in the presence of common subsurface oxidants including iron and manganese oxides, nitrate, and oxygen, to evaluate the effect of the oxidants on the enhancement and inhibition of Tc(VII) reduction, and reoxidation of Tc(IV). Addition of iron oxides (goethite and hematite) to the Tc(VII)-NAu-2 system, where Tc(VII) reduction was ongoing, enhanced reduction of Tc(VII), apparently as a result of re-distribution of reactive Fe(II) from NAu-2 to more reactive goethite/hematite surfaces. Addition of manganese oxides stopped further Tc(VII) reduction, and in case of K+-birnessite, it reoxidized previously reduced Tc(IV). Nitrate neither enhanced reduction of Tc(VII) nor promoted reoxidation of Tc(IV). Approximately 11% of Tc(IV) was oxidized by oxygen. The rate and extent of Tc(IV) reoxidation was found to strongly depend on the nature of the oxidants and concentration of Fe(II). When the same oxidants were added to aged Tc reduction products (mainly NAu-2 and TcO2•nH2O), the extent of Tc(IV) reoxidation decreased significantly relative to fresh Tc(IV) products. Increasing NAu-2 concentration also resulted in the decreased extent of Tc(IV) reoxidation. The results were attributed to the effect of NAu-2 aggregation that effectively retained Tc(IV) in the solid and decreased its vulnerability to reoxidation. Overall, our results implied that bioreduced clay minerals could play an important role in reducing Tc(VII) and in maintaining the long-term stability of reduced Tc(IV).

Jaisi, Deb P.; Dong, Hailiang; Plymale, Andrew E.; Fredrickson, Jim K.; Zachara, John M.; Heald, S.; Liu, Chongxuan

2009-06-20

190

Distribution of clay minerals on the Alaskan margin near Barrow Canyon revealed by Diffuse Spectral Reflectance measurements  

NASA Astrophysics Data System (ADS)

Sediment clay mineral assemblages provide an excellent means of assessing the provenance of Arctic sediment due to the variety of sediment transport mechanisms at work and the existence of distinct weathering sources from differing bedrock geology. During HOTRAX Leg 1 aboard the USCG Ice breaker Healy (cruise HLY0501), we collected jumbo piston cores on the Alaskan margin near Barrow Canyon which provide detailed Holocene sedimentary records. Measurements of Diffuse Spectral Reflectance (DSR) were collected at 1cm resolution from the split surface of the cores using a Minolta CM-2600d UV/VIS spectrophotometer (400-700nm wavelength range; 10nm resolution; 3mm spot size). To interpret the resulting downcore records, we present a preliminary study using 28 coretop sediment samples collected by the Shelf-Basin Interaction program in 2004 arrayed in four transects across the shelf near Barrow Canyon. The samples were analyzed using an ASD Labspec Pro FR UV/VIS/NIR spectrometer (250-2500nm wavelength range, 2-10nm resolution; 20mm spot size). Our results indicate that the measurements from the two instruments are offset by constant factors, but can be easily compared. To estimate the clay mineralogy of the cores, we decomposed the matrix of DSR measurements from the coretop and downcore samples using principle component analysis and compared the resulting factor score patterns with mineral diffuse spectral reflectance signatures from known samples measured in our lab or available from version 5 of the USGS Digital Spectral Library. The three leading modes extracted by principle component analysis of the downcore samples are applicable to the coretops. We infer that the first principle component mode relates to smectite, the second to chlorite, and the third to a mixture of illite and goethite (herein referred to as illite - goethite). The geographic and bathymetric trends in the coretop data indicate that (1) the smectite and illite - goethite components both increase with depth and reach greater values in the two western transects than in the two eastern transects closest to the coast and Barrow Canyon, (2) the smectite and illite- goethite components are anticorrelated in the two western transects, but not in the two eastern transects, (3) chlorite decreases with depth and is highest in the two transects closest to Barrow Canyon. These results suggest that the chlorite on the Alaskan margin is transported by nearshore currents from the Bering Straight and then by bottom currents flowing through the Barrow Canyon. Accordingly, we interpret downcore chlorite peaks inferred from DSR measurements in our sediment cores as evidence of times of enhanced input of Pacific water to the Alaskan Margin.

Orsburn, C.; Ortiz, J. D.; Polyak, L.; Grebmeier, J. M.; Darby, D.

2007-12-01

191

Intercalation of a surfactant with a long polyfluoroalkyl chain into a clay mineral: unique orientation of polyfluoroalkyl groups in clay layers.  

PubMed

Eight novel polyfluorinated surfactants (C(n)F(2n+1)CONH(CH2)2 N(+)(CH3)2C16H33 Br(-); abbreviated as CnF-S, where n = 1, 2, 3, 4, 5, 6, 8, 10) were synthesized and their intercalation into cation-exchangeable clay was investigated. All of the polyfluorinated surfactants intercalated in amounts exceeding the cation exchange capacity (CEC) of the clay. The C4F-S and C5F-S surfactants exhibited intercalation up to 480% of the CEC as a saturated adsorption limit. On the basis of X-ray analysis, CnF-S surfactants intercalated between clay nanosheets to form a bilayer structure in which the surfactant molecules tilt at an angle of ?60° with respect to the clay surface. The saturated adsorption limits and layer distances differed between surfactants with short (n = 1, 2) and long (n = 3-10) perfluoroalkyl chains. For long-chain surfactants, their saturated adsorption limits were independent of the perfluoroalkyl chain length and the layer distances systematically increased with increasing perfluoroalkyl chain length. These results suggest that the microscopic orientation differed between the short and long chains. X-ray analysis showed that the long-chain surfactants orient the perfluoroalkyl chains at a tilt of 41 ± 5° with respect to the clay layer. This value was in good agreement with polarized IR measurements of 42 ± 2° for this angle. PMID:23909606

Yui, Tatsuto; Fujii, Shunsuke; Matsubara, Kazuki; Sasai, Ryo; Tachibana, Hiroshi; Yoshida, Hirohisa; Takagi, Katsuhiko; Inoue, Haruo

2013-08-27

192

Thermal Stability of SO2- and NO2 Adsorbed on the Surface of Sepiolite, a Porous Clay Mineral  

NASA Astrophysics Data System (ADS)

Nitrogen dioxide (NO2) and sulfur dioxide (SO2) adsorbed on the surface (sub-basket) of a porous clay mineral of sepiolite (Mg4Si6O15(OH)2\\cdot 6H2O) at room temperature were studied in terms of ESR signals after ?-ray irradiation at 77 K. Molecular radical species were observed with the anisotropic g-factors of gx=2.0055, gy=1.9921 and gz=2.0020 and hyperfine splitting constants of Ax=5.25 mT, Ay=4.90 mT and Az=6.49 mT for NO2, and g\\|=2.0093 and g\\bot=2.0024 for SO2-. The activation energies and frequency factors for thermal annealing of NO2 adsorbed on as-received sepiolite and HCl-treated sepiolite are 0.23 eV, 2.2× 104 s-1 and 0.25 eV, 4.7× 104 s-1, respectively. The NO2 signal was thermally annealed at temperatures up to 200 K. A different property of NO2 signal as that in solid NO2 was observed in a more concentrated NO2 gas adsorbed on sepiolite. A paramagnetic SO2- signal was observed during the annealing experiment at 260 K.

Matsuda, Tokiyoshi; Ikeya, Motoji

2002-05-01

193

Transformation of the soil clays under the anthropogenic salinization  

NASA Astrophysics Data System (ADS)

The objects of our investigation are the podzolic soils from the Seriogovo salt plug territory (Russian platform) where salt mineral waters deposites are situated. Samples were obtained from 7 soil uncontaminated (background) and saline cross sections near the Seryogovo salt deposite at the depth 0-103 cm. X-ray analysis indicates that almost all clay samples of background sections contain smectite, illite, chlorite, kaolinite with dominated smectite. In clay samples of saline soils chlorite, vermiculite, interstratified chlorite/vermiculite, kaolinite, illite and galite are contained. Chlorite became the predominant 1.4-nm-mineral. Smectite is the most abundant mineral in the clay fraction of uncontaminated soils. The smectite is not well ordered, evident by incomplete collapse to 1.0 nm when heated to 550oC. Small amount of disordered chlorite contains in this samples. In the lower parts of saline cross sections smectite is almost disappeared, the most abundant minerals are pedogenic dioctahedral chlorite and interstratified minerals. The comparison of the "d(060)" value of XRD patterns display that uncontaminated and contaminated samples has both trioctahedral and dioctahedral minerals but the intensity of the 060 peak for the dioctahedral mineral of saline soils, however, is proportionally larger than in the uncontaminated clay. The investigations display the difference between the clay minerals of saline and background soil samples of Seriogovo deposits because of their transformation under the environmental changes. The expandable layer silicates typical for the soils transformed to the unexpandable dioctahedral soil chlorite. Transformation reactions involves the introduction of non-exchangable hydroxyl-Al polymers into the interlamellar space of pre-existing smectite or vermiculite. We can propose that interlayer octahedral layers are more stable than exchangeable cations of clay minerals' crystal structure in the saline environment. The results presented suggest that chlorite was formed diagenetically by prolonged periodic percolation of salt brines through previous layer silicates.

Simakova, Y.

2009-04-01

194

Adsorption of dissolved aluminum on sapphire-c and kaolinite: implications for points of zero charge of clay minerals  

PubMed Central

We have studied the impact of dissolved aluminum on interfacial properties of two aluminum bearing minerals, corundum and kaolinite. The effect of intentionally adding dissolved aluminum on electrokinetic potential of basal plane surfaces of sapphire was studied by streaming potential measurements as a function of pH and was complemented by a second harmonic generation (SHG) study at pH 6. The electrokinetic data show a similar trend as the SHG data, suggesting that the SHG electric field correlates to zeta-potential. A comparable study was carried out on kaolinite particles. In this case electrophoretic mobility was measured as a function of pH. In both systems the addition of dissolved aluminum caused significant changes in the charging behavior. The isoelectric point consistently shifted to higher pH values, the extent of the shift depending on the amount of aluminum present or added. The experimental results imply that published isoelectric points of clay minerals may have been affected by this phenomenon. The presence of dissolved aluminum in experimental studies may be caused by particular pre-treatment methods (such as washing in acids and subsequent adsorption of dissolved aluminum) or even simply by starting a series of measurements from extreme pH (causing dissolution), and subsequently varying the pH in the very same batch. This results in interactions of dissolved aluminum with the target surface. A possible interpretation of the experimental results could be that at low aluminum concentrations adatoms of aluminum (we will refer to adsorbed mineral constituents as adatoms) can form at the sapphire basal plane, which can be rather easily removed. Simultaneously, once the surface has been exposed to sufficiently high aluminum concentration, a visible change of the surface is seen by AFM which is attributed to a surface precipitate that cannot be removed under the conditions employed in the current study. In conclusion, whenever pre-treatment or the starting point of an experiment favor the dissolution of aluminum, dissolved Al may remain in the experimental system and interact with the target surfaces. The systems are then no longer pristine and points of zero charge or sorption data are those of aluminum-bearing systems.

2014-01-01

195

On the origin of mixed-layered clay minerals from the San Andreas Fault at 2.5–3 km vertical depth (SAFOD drillhole at Parkfield, California)  

Microsoft Academic Search

A detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along\\u000a the San Andreas Fault Observatory at depth (SAFOD) drill hole. The characteristics of authigenic illite–smectite (I–S) and\\u000a chlorite–smectite (C–S) mixed-layer mineral clays indicate a deep diagenetic origin. A randomly ordered I–S mineral with ca.\\u000a 20–25% smectite layers is one of

A. M. Schleicher; L. N. Warr; B. A. van der Pluijm

2009-01-01

196

Provenance and depositional environments of the late Neogene Red Clay deposits in Northern China based on detrital zircon and heavy mineral analysis  

NASA Astrophysics Data System (ADS)

The late Miocene - Pliocene (about 11-2.5 Ma) time is the latest period of undisturbed global warmth before the onset of glacial times. Pliocene climate state is proposed as almost an analogue for future global climate by the end of 21st century and has been focus of much research. The Neogene red earth underlying the Pleistocene loess - paleosol deposits in northern China, has been demonstrated to have a relatively continuous depositional character at least over the past ~7-8 to ~2.6Ma. These Red Clay deposits are not only important continental archives of late Miocene-Pliocene environmental and climatic changes, but also preserve significant information on past atmospheric circulation patterns. Multiple competing hypotheses have been proposed for the provenance of Red Clay deposits of the Chinese Loess Plateau (CLP), yet none has been confirmed. Whether it is sediments derived from single or multiple source areas still remains ambiguous. U-Pb age dating of detrital zircons from clastic sediments has proved to be powerful tool to trace sediment sources. However, this method is seldom applied in constraining the provenance of Red Clay deposits. In this study, we selected three typical Red Clay sections across the northern China. They are Dongwan in the western part, Lantian in the southern part and Baode in the northeastern part of the CLP. Based on the systematic field geologic survey, stratigraphic investigation and magnetostratigraphy, 15 samples in different stratigraphic levels were chosen. By applying the zircon U-Pb dating and single grain zircon morphology, combined with heavy mineral analysis of the Red Clay samples, the research aims to investigate the source and spatio-temporal evolution of Neogene Red Clay deposits of northern China. This study has significant implications for understanding the Red Clay depositional environments and will give insight into the past wind systems responsible for transporting dust onto the Chinese Loess Plateau.

Shang, Yuan; Kaakinen, Anu; Beets, Christiaan J.; Prins, Maarten A.

2014-05-01

197

{sup 133}Cs NMR and XPS investigation of cesium adsorbed on clay minerals and related phases  

SciTech Connect

{sup 133}Cs MAS NMR and Cs XPS were used to study the adsorption of Cs on kaolinite, montmorillonite, corundum, and gibbsite from 0.1 N and 0.01 N CsCl solutions. XPS spectra for all samples except gibbiste contain strong signals associated with Cs 3d{sub 3/2} and 3d{sub 5/2} photopeaks. This result indicates that minerals without exchangeable cation sites have a tendency to sorb Cs on surfaces and along grain boundaries, although less than 1 mol% Cs is observed on these surfaces. Multiple surface or interlayer sites for Cs cannot be resolved from the individual Cs XPS peaks. The {sup 133}Cs NMR data, combined with TEM/XRD data for kaolinite show the following: (1) For montmorillonite, most of the Cs is adsorbed in the interlayers and at room humidity is motionally averaged among two or more sites at room temperature. (2) The spectra for kaolinite are similar to those of montomorillonite, and the tightly bonded Cs in our sample appears to be in expandable interlayers which exits as mixed layers with kaolinite and not as discrete smectite. (3) The Cs environments in both montmorillonite and kaolinite are sensitive to humidity. (4) For kaolinite the {sup 133}Cs chemical shift changes at low temperature and 100% humidity, indicating that the interlayer charge of its expandable layers is very small. (5) No {sup 133}Cs NMR signal could be detected for gibbsite or corundum. {sup 133}Cs NMR may be a useful probe of the presence and characteristics of expandable layers in kaolinite. 62 refs., 14 figs.

Kim, Yeongkyoo; Kirkpatrick, R.J. [Univ. of Illinois, Urbana, IL (United States); Cygan, R.T. [Sandia National Laboratories, Albuquerque, NM (United States)

1996-03-01

198

Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China  

Microsoft Academic Search

The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite

Shifeng Dai; Lei Zhao; Suping Peng; Chen-Lin Chou; Xibo Wang; Yong Zhang; Dan Li; Yingying Sun

2010-01-01

199

Insights into the Mechanism of Fe(II) Adsorption and Oxidation at Fe-Clay Mineral Surfaces from First-Principles Calculations  

SciTech Connect

Interfacial reactivity of redox-active iron-bearing mineral surfaces plays a crucial role in many environmental processes including biogeochemical cycling of various elements and contaminants. Herein, we apply density-functional-theory (DFT) calculations to provide atomistic insights into the heterogeneous reaction between aqueous Fe(II) and the Fe-bearing clay mineral nontronite Fe2Si4O10(OH)2 by studying its adsorption mechanism and interfacial Fe(II)-Fe(III) electron transfer (ET) at edge and basal surfaces. We find that edge-bound Fe(II) adsorption complexes at different surface sites (ferrinol, silanol and mixed) may coexist on both (010) and (110) edge facets, with complexes at ferrinol FeO(H) sites being the most energetically favorable and coupled to proton transfer. Calculation of the ET activation energy suggests that interfacial ET into dioctahedral Fe(III) sheets is probable at the clay edges and occurs predominantly but not exclusively through the complexes adsorbed at ferrinol sites and might also involve mixed sites. No clear evidence is found for complexes on basal surface that are compatible with ET through the basal sheet despite this experimentally hypothesized ET interface. This study suggests a strong pH-dependence of Fe(II) surface complexation at basal versus edge facets and highlights the importance of the protonation state of bridging ligands and proton coupled electron transfer to facilitate ET into Fe-rich clay minerals.

Alexandrov, Vitali Y.; Rosso, Kevin M.

2013-10-02

200

Origin and diagenesis of clay minerals in relation to sandstone paragenesis: An example in eolian dune reservoirs and associated rocks, Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming  

SciTech Connect

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in the diagenetic evolution of these sandstones. Allogenic clay minerals are present in shaly rock fragments and laminae. Early infiltration of clays into porous sabkha sands commonly form characteristic menisei or bridges between framework grains or, when more extensive, form coatings or rims on grain surfaces. Authigenic clays include nearly pure smectite, mixed-layer illite/smectite (I/S), and late diagenetic illite and corrensite; these clay minerals are present as pore-lining cements. In addition to the deposition and neoformation of clay minerals throughout sandstone paragenesis, the conversion of smectite to illite occurred as temperatures increased with progressive burial. A temperature of 103C is calculated at a present depth of 3,200 m using a geothermal gradient of 30C/km and a mean annual surface temperature of 7C. After correction for uplift and erosion (250 m), the maximum calculated temperature for the conversion of all random I/S to ordered I/S is 100C. This calculated temperature is in excellent agreement with temperatures of 100-110C implied from I/S geothermometry.

Pollastro, R.M.; Schenk, C.J. (Geological Survey, Denver, CO (United States))

1991-06-01

201

Evaluation of the endotoxin binding efficiency of clay minerals using the Limulus Amebocyte lysate test: an in vitro study  

PubMed Central

Endotoxins are part of the cell wall of Gram-negative bacteria. They are potent immune stimulators and can lead to death if present in high concentrations. Feed additives, which bind endotoxins in the gastrointestinal tract of animals, could help to prevent their negative impact. The objective of our study was to determine the potential of a bentonite (Bentonite 1), a sodium bentonite (Bentonite 2), a chemically treated smectite (Organoclay 1) and a modified attapulgite (Organoclay 2) to bind endotoxins in vitro. Polymyxin B served as positive control. The kinetic chromogenic Limulus Amebocyte lysate test was adapted to measure endotoxin activity. Firstly, a single sorption experiment (10 endotoxin units/mL (EU/mL)) was performed. Polymyxin B and organoclays showed 100% binding efficiency. Secondly, the adsorption efficiency of sorbents in aqueous solution with increasing endotoxin concentrations (2,450 – 51,700 EU/mL) was investigated. Organoclay 1 (0.1%) showed a good binding efficiency in aqueous solution (average 81%), whereas Bentonite 1 (0.1%) obtained a lower binding efficiency (21-54%). The following absorbent capacities were calculated in highest endotoxin concentration: 5.59 mg/g (Organoclay 1)?>?3.97 mg/g (Polymyxin B)?>?2.58mg/g (Organoclay 2)?>?1.55 mg/g (Bentonite 1)?>?1.23 mg/g (Bentonite 2). Thirdly, a sorption experiment in artificial intestinal fluid was conducted. Especially for organoclays, which are known to be unspecific adsorbents, the endotoxin binding capacity was significantly reduced. In contrast, Bentonite 1 showed comparable results in artificial intestinal fluid and aqueous solution. Based on the results of this in vitro study, the effect of promising clay minerals will be investigated in in vivo trials.

2014-01-01

202

Geotechnical evaluation of Turkish clay deposits: a case study in Northern Turkey  

NASA Astrophysics Data System (ADS)

Clay deposits in Oltu-Narman basins (Erzurum, northern Turkey) have been studied to determine their engineering properties and to evaluate their uses for geotechnical applications. These deposits are concentrated in two different stratigraphic horizons namely the Late Oligocene and the Early Miocene sequences. Clay-rich fine-grained sedimentary units are deposited in shallow marine and lagoonar mixed environments. Their clay minerals originated by the alteration of Eocene calc-alkaline island-arc volcanics, preferably from pyroclastics (trachite and andesite flow), which form the basement for the Oltu depression. Smectite group clay minerals are found abundant in clay deposits. The experimental results show that the clay soils have high plasticity behaviors and low hydraulic conductivity properties. The optimum water content, the free swell, and the swelling pressure of clay samples decreased and the maximum dry unit weight of clay samples increased under high temperature. Consequently, it is concluded that the expanding of clay soils is an important soil problem that cannot be avoided in the significant parts of Oltu city and its villages. However, the soils of clay-rich layers in the outcrops-section of clay deposits can be successfully used to build compacted clay liners for landfill systems and to construct vertical and horizontal barriers for protection of ground water and for preventing soil pollution in geotechnical applications.

Kalkan, Ekrem; Bayraktutan, M. Salih

2008-09-01

203

Distribution of clay minerals in surface sediments from the eastern Barents and south-western Kara seas  

Microsoft Academic Search

Surface samples from the eastern Barents and south-western Kara seas have been analysed for clay mineralogy. Transport paths, the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central Arctic Ocean deep sea and sea ice sediments. Franz Josef Land and Novaya

D. Nürnberg; M. A. Levitan; J. A. Pavlidis; E. S. Shelekhova

1995-01-01

204

Fluid-rock interaction controlling clay-mineral crystallization in quartz-rich rocks and its influence on the seismicity of the Carboneras fault area (SE Spain)  

NASA Astrophysics Data System (ADS)

The Carboneras Fault zone is one of the longest fault in the Betic Cordillera (SE Spain) and it would be a good candidate to generate large magnitude earthquakes (Gracia et al., 2006). Seismicity in the region is characterised by low to moderate magnitude events, although large destructive earthquakes have occurred, which reveals significant earthquake and tsunami hazards (Masana et al., 2004). Due to the internal architecture of the fault zone, shear lenses of post-orogenic sediments of Miocene and Pliocene age including marls and sandstones sequences are juxtaposed to the predominant slaty gouges of the Alpine basement. Microcataclasites and gouges of the quartz-rich post-orogenic sediments are also developed as cm- to m-scale bands, allowing the comparison between the deformed materials and their protoliths. Red, yellow and white sandstones and their respective cataclasites can be identified. This communication is concerned with the clay mineral crystallization events in these materials and its possible influence on the seismicity model of the region. The presence of phyllosilicates in fault zones as either neoformed or inherited clays is commonly related with fluid circulation and a mechanically weak fault behaviour (e.g., Wang, 1984). A critical factor for the understanding of the mechanical role of clays in fault rocks is to determine the timing of formation of mineral assemblages and microstructure of fault rocks and protolith. The effects of post-faulting alteration limit inferences about fault behaviour that can be made from exhumed rocks. The Carboneras fault zone provides good opportunities to study mineral processes enhanced by deformation, given that it is located in a region of arid climate and shows outcroppings of quartzitic rocks included in slaty rocks. Combined XRD, optical microscopy and SEM analyses reveal that deformed quartzitic rocks are enriched in phyllosilicates, increasing especially the amount of chlorite. The samples strongly damaged are characterised also by the presence of dolomite and gypsum. The deformation is highly localized, developing phyllosilicate-rich bands highly foliated due to the presence of fine-sized aligned clays (chlorite and mica). In some undeformed lenses of the cataclastic rocks, variable-sized patches of phyllosilicates containing random oriented stacks of chlorite and mica are developed. BSE images reveal that the stacks are made of two intergrown compositional types of chlorite. These results lead to conclude that limited clay growth during faulting occurred. The absence of significant compositional differences between undeformed and deformed phyllosilicates suggests that whereas fluids were present during strike-slip faulting, fluids were not preferentially focused along the quartz-rich rocks of the fault zone by phyllosilicates avoiding the development of the synkinematic clay alteration process. However, clays played an important role for the mechanical behaviour of the quartzitic rocks in the fault zone. Deformation is highly localized in chlorite-rich sandstones. These sandstones show substantial clay crystallization which texture can be related with a hydrothermal origin before strike-slip faulting, likely associated with the volcanic activity of the area leading to form of chlorite/mica patches. These data indicate that, although elevated fluid pressure confined by clay fabric cannot be appealed for the mechanical behaviour of the sandstones of the Carboneras fault, clay fabrics developed during deformation dominated the fault-weakening mechanism. We consider that lubricating properties of phyllosilicates in the quartzitic rocks were an important factor controlling movement mechanisms promoting the predominance of creep as regards seismic stick-slip (Bedrosian et al., 2004) reducing the possibility of larger seismogenic events that nucleate on localized fault planes developed within quartzitic rocks contained within the fault zone. Finally the crystallization of dolomite and gypsum in the highly damaged areas of the microcataclasites could be related with rec

Jimenez-Espinosa, R.; Abad, I.; Jimenez-Millan, J.; Lorite-Herrera, M.

2009-04-01

205

Clay mineral assemblages of terrestrial records (Xining Basin, China) during the Eocene-Oligocene climate Transition (EOT) and its environmental implications  

NASA Astrophysics Data System (ADS)

The Eocene-Oligocene Transition (EOT) between ~34.0 and 33.5 million years ago, where global climate cooled from 'greenhouse' to 'icehouse' at ~33.5 Ma ago, is one of the great events during Cenozoic climate deterioration. In contrast to the marine records of the EOT, significantly less research has focused on the continental climate change during this time, particularly in inner Asia. We present a comprehensive study of the upper Eocene to lower Oligocene succession with regular alternations of laterally continuous gypsum/gypsiferous layers and red mudstone beds in Tashan section of Xining Basin, which is located at the northeastern margin of the Tibetan Plateau. Clay minerals, which were extracted from this succession, were analyzed qualitatively and semi-quantitatively by using X-ray differaction (XRD). Base on detailed magnetostratigraphic time control, clay mineral compositions of this succession (33.1-35.5 Ma) are compared with open ocean marine records and Northern Hemisphere continental records to understand the process and characteristics of Asian climate change before, during and after EOT. Our results indicate that illite is the dominant clay mineral with less chlorite and variable smectite. Multi-parameter evidence suggests that the source areas of detrital inputs in Tashan have not changed and climate is the main control for the composition of the clay fraction. The characteristics of clay mineral concentrations suggest warm and humid fluctuations with cold and dry conditions and intense of seasonality during ~35.5-34.0 Ma in inner Asian. This changed to cold and dry condition at ~34 Ma and remained so from ~34-33.1 Ma. The comparisons between continental and marine records indicate that the climate changes experienced in the Xining basin region are more consistent with Northern Hemisphere rather than open oceans records. This indicates that paleoclimate changes for inner Asian before, during and after EOT was not controlled by Antarctic ice growth, but may be due to atmospheric cooling linked to the existence and expansion of Northern Hemisphere glaciation.

Zhang, C.; Guo, Z.

2013-12-01

206

An EXAFS study on the effects of natural organic matter and the expandability of clay minerals on cesium adsorption and mobility  

NASA Astrophysics Data System (ADS)

The relationship between cesium (Cs) adsorption on clay minerals with various expandabilities and Cs mobility in environment was investigated using sequential extraction, batch adsorption, X-ray diffraction (XRD), generalized adsorption model (GAM), and Cs LIII-edge extended X-ray absorption fine structure (EXAFS) analyses with molecular simulations using the density functional theory (DFT). In particular, the difference between the affinities of illite (non-expansion) and vermiculite (intermediate expansion) for Cs and the effect of humic acid (HA) addition on the Cs/clay mineral system were highlighted in this study. These two factors affect Cs mobility and bioavailability in surface soil and sediments. The batch adsorption results showed that Cs adsorption was inhibited to some extent in the ternary clay + HA + Cs system because of (i) the blocked access of Cs to the frayed edge site (FES) and type II site [inner-sphere (IS) complex in GAM] by HA, and (ii) the reduced availability of the interlayer site in vermiculite. EXAFS analysis further confirmed that the adsorbed Cs in clay minerals was drastically changed by the sequential addition of HA. In addition, the dominant IS complex in the illite + Cs and illite + Cs + HA systems (in which HA was added after Cs adsorption on illite) can be converted to the outer-sphere (OS) complex largely in the illite + HA + Cs system (in which HA was added prior to Cs adsorption). These results are consistent with the sequential extraction and GAM results. The IS complex of dehydrated Cs+ mainly formed at the FES and interlayer site on illite (non-expansion) without resulting in any illite structural changes. However, on vermiculite (intermediate expansion), the dehydrated Cs+ can be adsorbed as an IS complex associated with the siloxane group of the di-trigonal cavity in the tetrahedral SiO4 sheet. This adsorption is accompanied by collapse of the layer, which can be easily coated by HA molecules to prevent Cs fixation. However, a nearly complete OS complex was observed at the planar site of montmorillonite (large expansion). These processes were confirmed by sequential extraction, batch adsorption, XRD, and EXAFS, which clearly showed that Cs mobility in soil highly depends on clay mineral expandability, natural organic matter (NOM), and the coupling of both effects. The atomic-scale information given by EXAFS is consistent with the distribution data from adsorption experiments, GAM, sequential extraction, and DFT. These results can be used as a basis for a clearer understanding of Cs behavior in natural systems.

Fan, Q. H.; Tanaka, M.; Tanaka, K.; Sakaguchi, A.; Takahashi, Y.

2014-06-01

207

Biodegradation and adsorption of C1- and C2-phenanthrenes and C1- and C2-dibenzothiophenes in the presence of clay minerals: effect on forensic diagnostic ratios.  

PubMed

The impact of modified montmorillonites on adsorption and biodegradation of crude oil C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. Consequently, the effect on C1-dibenzothiophenes/C1-phenanthrenes, C2-dibenzothiophenes/C2-phenanthrenes, 2+3-methyldibenzothiophene/4-methyldibenzothiophene and 1-methyldibenzothiophene/4-methyldibenzothiophene ratios commonly used as diagnostic ratios for oil forensic studies was evaluated. The clay mineral samples were treated to produce acid activated montmorillonite, organomontmorillonite and homoionic montmorillonite which were used in this study. The different clay minerals (modified and unmodified) showed varied degrees of biodegradation and adsorption of the C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes. The study indicated that as opposed to biodegradation, adsorption has no effect on the diagnostic ratios. Among the diagnostic ratios reviewed, only C2-dibenzothiophenes/C2-phenanthrenes ratio was neither affected by adsorption nor biodegradation making this ratio very useful in forensic studies of oil spills and oil-oil correlation. PMID:24275986

Ugochukwu, Uzochukwu C; Head, Ian M; Manning, David A C

2014-07-01

208

The role of clay minerals and fulvic acid to the complexation of Na, Mg, and Ca in stream flows from adjacent forested head watersheds composed of different vegetation  

NASA Astrophysics Data System (ADS)

In order to understand the complexation and flow process in metal elements under a fresh water environment, discharges of Na, Mg, and Ca were measured in streams of adjacent forested head watersheds composed of coniferous evergreen- and deciduous broad leaf- trees. Total elements (T-Na, T-Mg, and T-Ca) and ions (Na+, Mg2+, and Ca2+) in stream flows which passed through 0.45 ?m filters were measured with an ICP and Ion-chromatograph. The remainders of total elements and ions were equated with complex compounds. Then the discharges of Si and fulvic acid, which respectively are the representatives of ligands by clay minerals and humic substances, provided the relationship between the compound discharges and the complexation process of the above metal elements. Even if Na, Mg, and Ca are believed to be mostly free ions in fresh water environments, the rates of the compounds to the total elements ranged 10 to 40 % in the coniferous watershed and 20 to 60 % in the deciduous watersheds. The compounds sometimes occupied more than half of the total elements; this was predominant in the deciduous watershed. These mean that the discharge of compounds is not negligible in watershed hydrology. Possible complexation processes in metal elements are #1) Hydration, #2) Adsorption or substitution with clay minerals, #3) Mineral complex, #4) Adsorption with humic substances as represented by fulvic acid, and #5) Chelate with organic acids as oxalate, formic acid, and pyrrole. Under fresh water environments, #2 and #4 must be the most potential processes of the complexation in metal elements. The relationship between the compounds, Si, and fulvic acid, therefore, supplies useful information to presume the status of the compounds. The compounds-Si relations in both watersheds showed linear correlations (r=0.79 to 0.99) for a stream base flow and stream flow in a small rainstorm. The linear correlations, however, occurred only for the stream flow in the compounds-Si relations at a big rain storm in the deciduous watershed (r=0.89 to 1.00) and also for the storm flow in the compound-fulvic acid relations (r=0.95 to 0.99). These things mean that the metal elements possibly flowed out as organic and/or inorganic complexes and the complexation could have been promoted in the deciduous watershed during rain storms. Thick organic soil, broadly distributing in the deciduous watershed, seems to be reasonable for promoting such complexation due to subsurface water movement in the soil through the contact of the metal elements with clay minerals and fulvic acid. In contrast, the much rainwater flows down below the surface within the loose litter and root-permeated zone developing predominantly in the coniferous watershed, where small clay minerals and humic substances occurs; which represents the rare contact of the metal elements with the clay minerals and fulvic acid in such flow paths. This would be the reason for the small and restrained complexation in the coniferous watershed at the big rain storm. The hydrochemical process in slope-stream systems can be controlled by the complexation affected by both the flow path of rainwater and the distribution of clay minerals and humic substances in soils.

Terajima, Tomomi; Moriizumi, Mihoko; Nakamura, Tomohiro

2010-05-01

209

Green Clay Minerals  

Microsoft Academic Search

Color is a problem for scientific study. One aspect is the vocabulary one used to describe color. Mint green, bottle green, and Kelly green are nice names but not of great utility in that people's physical perception of color is not always the same. In some industries, such as colored fabric manufacture, current use is to send a set of

B. Velde

2003-01-01

210

Laboratory study on heterogeneous degradation of methyl chloroform (CH3CCl3) on aluminosilica clay minerals as its potential tropospheric sink  

NASA Astrophysics Data System (ADS)

Heterogeneous reactions of methyl chloroform (1,1,1-trichloroethane, CH3CCl3) with alminosilica clay particles were examined between 288 and 313 K as a potential sink. Allophane and halloysite particles exhibited the activity to transform CH3CCl3 to 1,1-dichloroethene (CH2 = CCl2). The dependence of the reaction rate on the pretreatment, temperature, and relative humidity suggested that the reaction could proceed under environmental conditions. Illumination of light with wavelength longer than 300 nm did not affect CH3CCl3 decay but caused heterogeneous degradation of CH2 = CCl2 on clay particles. The lower limit of overall sticking coefficient for fresh allophane and halloysite particles was estimated to be 6×10-9 and 1.1×10-8, respectively. Heterogeneous degradation of CH3CCl3 on mineral aerosols and/or soils is worth taking into consideration in deriving tropospheric OH concentrations from global budget concentrations of CH3CCl3.

Kutsuna, Shuzo; Takeuchi, Koji; Ibusuki, Takashi

2000-03-01

211

Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains  

Microsoft Academic Search

Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis

G. J. Flynn; S. R. Sutton

1989-01-01

212

Occurrence, abundance and origin of minerals in coals and coal ashes  

Microsoft Academic Search

The mineralogy of coal and coal ash samples from a wide variety of deposits worldwide has been studied by X-ray diffractometry, light microscopy, SEM, TEM, and DTA-TGA methods. The common major minerals identified in the crystalline matter of coals are quartz, kaolinite, illite, calcite, pyrite, plagioclase, K-feldspar and gypsum, and occasionally dolomite, ankerite, siderite, Fe oxyhydroxides and sulphates. A number

Stanislav V. Vassilev; Christina G. Vassileva

1996-01-01

213

Abundance and diversity of total and nitrifying prokaryotes as influenced by biochemical quality of organic inputs combined with mineral nitrogen  

NASA Astrophysics Data System (ADS)

Ammonia-oxidizing bacteria and archaea (AOB, AOA) co-exist in soil, but they respond differently to distinct fertilization strategies in agricultural soils. Accordingly, effects of organic inputs and combination with mineral nitrogen (N) on AOB and AOA remain poorly understood. The aim of this study was to compare soil amendment with contrasting quality of organic inputs (i.e., high quality Tithonia diversifolia (TD; C/N ratio: 13, Lignin: 8.9 %; Polyphenols: 1.7 %), intermediate quality Calliandra calothyrsus (CC; 13; 13; 9.4) and low quality Zea mays (ZM; 59; 5.4; 1.2)), and combination with mineral N on the abundance (i.e., DNA-based gene quantification) and community structure (i.e., T-RFLP analysis) of total bacterial and archaea (16S rRNA gene), as well as AOB and AOA (targeting the amoA gene) communities in a Humic Nitisol. Soils (0-15 cm depth) were sampled prior to the onset of the rainy season in March 2012 in a 10 years old field experiment established in the central highlands of Kenya in 2002. Since the start of the experiment, organic inputs were applied annually at a rate of 4 Mg C ha-1 and mineral N twice a year as calcium ammonium nitrate (5Ca(NO3)2NH4NO3) at a rate of 120 kg N ha-1 growing season-1. Quality of organic inputs posed only a significant effect on the AOB community structure between TD versus ZM and CC versus ZM. Moreover, TD significantly increased the size of AOB over ZM input, while higher abundances for total bacteria, total archaea and AOA were measured in ZM and TD over CC. This was explained by high and available N in TD, but low lignin and polyphenol contents in TD and ZM as opposed to CC. AOB responded sensitively (i.e., complete community structure separation) to mineral N, specifically when combined with low quality ZM. Hence, AOB community was specifically responsive to quality of organic inputs and combination of low organic input with mineral N over AOA and total prokaryotic communities in the studied soil. The results presented were however, generated on one occasion soil sampling representing the effect of continuous organic and inorganic fertilizer application for ten years. We therefore recommend for prospective research, further investigations to rule out the temporal (short-term) variations of microbial decomposer dynamics at different crops growth stages during a cropping season as well as comparing different soil types.

Muema, Esther; Vanlauwe, Bernard; Röhl, Carolin; Cadisch, Georg; Rasche, Frank

2014-05-01

214

Clay mineralogy and cation exchange capacity of Brazilian soils from water contents determined by thermal analysis  

Microsoft Academic Search

The clay size fraction of subtropical soils is dominated by kaolinite, gibbsite, iron oxides, and small amounts of 2:1 clay minerals. Among these minerals, it is more difficult to quantify the presence of the 2:1 clay minerals where kaolinite is the dominant clay mineral present. Thermal analyses of 56 size clay size fractions, free of iron oxides, developed on magmatic

Antonio Carlos S Costa; Jerry M Bigham; Cássio A Tormena; José Carlos Pintro

2004-01-01

215

Comment on "Evaluation of X-ray diffraction methods for determining the crystal growth mechanisms of clay minerals in mudstones, shales and slates," by L. N. Warr and D. R. Peacor  

USGS Publications Warehouse

A recent paper by Warr and Peacor (2002) suggested that our use of the Bertaut-Warren-Averbach technique (MudMaster computer program) for studying changes in crystallite thickness distributions (CTDs) of clay minerals during diagenesis and very low-grade metamorphism is not reliable because it is dependent on many variables which can not be fully controlled. Furthermore, the authors implied that the measured shapes of CTDs cannot be used with confidence to deduce crystal growth mechanisms and histories for clays, based on our CTD simulation approach (using the Galoper computer program). We disagree with both points, and show that the techniques are powerful, reliable and useful for studying clay mineral alteration in rocks. ?? 2003 Schweiz. Mineral. Petrogr. Ges.

Eberl, D. D.; Srodon, J.; Drits, V. A.

2003-01-01

216

Evaluation of first-row transition metal oxides supported on clay minerals for catalytic growth of carbon nanostructures  

Microsoft Academic Search

In the present work we employed various transition metals (Cr, Mn, Fe, Co, Ni, Cu and Zn) loaded on different smectite clays (laponite and montmorillonite) as catalysts in synthesis of carbon nanostructures (mainly nanotubes) and we report the effect of the nature of the catalytic centers and type of aluminosilicate layers in the morphology, quality and structure on the final

Theodoros Tsoufis; Lubos Jankovic; Dimitrios Gournis; Pantelis N. Trikalitis; Thomas Bakas

2008-01-01

217

The temperature dependence of hydrogen isotope fractionation between clay minerals and water: Evidence from a geopressured system  

Microsoft Academic Search

δD values of water samples from two Gulf Coast geopressured oil fields vary linearly with temperature, while the δD values from the coexisting clays remain constant and are independent of temperature. Fluid flow rates on the order of millimeters per year, characteristic of Gulf Coast geopressured systems, provide adequate residence time for hydrogen isotope equilibrium to be achieved between the

R CAPUANO

1992-01-01

218

The temperature dependence of hydrogen isotope fractionation between clay minerals and water: Evidence from a geopressured system  

Microsoft Academic Search

D values of water samples from two Gulf Coast geopressured fields vary linearly with temperature, while the D values from the coexisting clays remain constant and are independent of temperature. Fluid How rates on the order of millimeters per year, characteristic of Gulf Coast geopressured systems, provide adequate residence time for hydrogen isotope equilibrium to be achieved between the extant

R. M. Capuano

1992-01-01

219

Decreased leaf-miner abundance in elevated CO2: reduced leaf quality and increased parasitoid attack.  

PubMed

Most studies on the effects of elevated CO2 have focused on the effects on plant growth and ecosystem processes. Fewer studies have examined the effects of elevated CO2 on herbivory, and of these, most have examined feeding rates in laboratory conditions. Our study takes advantage of an open-top CO2 fertilization study in a Florida scrub-oak community to examine the effects of elevated CO2 on herbivore densities, herbivore feeding rates, and levels of attack of herbivores by natural enemies. Higher atmospheric CO2 concentration reduced plant foliar nitrogen concentrations, decreased abundance of leaf-mining insect herbivores, increased per capita leaf consumption by leafminers, and increased leafminer mortality. As suggested by other authors, reduced foliar quality contributed to the increase in herbivore mortality, but only partly. The major factor increasing mortality was higher attack rate by parasitoids. Thus increasing CO2 concentrations may reduce the survivorship of insect herbivores directly, by reducing plant quality, but also indirectly, by changing herbivore feeding and eliciting greater top-down pressure from natural enemies. PMID:11543430

Stiling, P; Rossi, A M; Hungate, B; Dijkstra, P; Hinkle, C R; Knott WM 3rd; Drake, B

1999-02-01

220

Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains  

NASA Technical Reports Server (NTRS)

Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis facility at the National Synchrotron Light Source presently underway should increase the range of detectable elements and permit the analysis of smaller samples. In addition the Advanced Photon Source will be commissioned at Argonne National Laboratory in 1995. This 7 to 8 GeV positron storage ring, specifically designed for high-energy undulator and wiggler insertion devices, will be an ideal source for an x ray microprobe with one micron spatial resolution and better than 100 ppb elemental sensitivity for most elements. Thus trace element analysis of individual micron-sized grains should be possible by the time of the comet nucleus sample return mission.

Flynn, G. J.; Sutton, S. R.

1989-01-01

221

Mineral resource of the month: gypsum  

USGS Publications Warehouse

You may not realize it, but the walls of your office are probably made from a mineral: gypsum. Gypsum is an abundant, evaporite-derived sedimentary mineral with deposits located throughout the world. It is often associated with paleoenvironmental lake and marine environments. In its pure form, gypsum consists of calcium sulfate dihydrate, although most crude gypsum naturally occurs in combination with anhydrite, clay, dolomite and/or limestone.

Crangle, Robert D.

2011-01-01

222

Dioxin congener patterns in commercial catfish from the United States and the indication of mineral clays as the potential source.  

PubMed

Since 1991 the US Department of Agriculture (USDA) has conducted annual surveys of pesticide residues in foods under the Agricultural Marketing Service's Pesticide Data Program (PDP). To assess chemical residues in domestically marketed catfish products, 1479 catfish samples were collected during the 2008-2010 PDPs. A subset of 202 samples was analysed for 17 toxic polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). The average pattern of the individual PCDD/F congener concentrations in the catfish was rather unique in that it had almost no measurable amounts of polychlorinated dibenzofurans (PCDFs), but all PCDDs were present. This pattern was more dominant in the domestically produced catfish products than in the imported products (China/Taiwan). Comparison of the pattern to known sources of PCDD/Fs showed strong similarities to the pattern of PCDD/Fs found in kaolin clays which have often been used as anti-caking agents in animal feeds. To investigate whether catfish feeds may be the source of the PCDD/Fs found in the catfish, archived catfish feed data from a US Food and Drug Administration (USFDA) database were examined. In 61 out of 112 feed samples, the PCDD concentrations were 50 times higher than the PCDF concentrations and resembled the pattern found in the catfish products and in clays mined in the south-eastern United States. Although the source of PCDD/Fs in domestically marketed catfish products cannot be definitively established, mined clay products used in feeds should be considered a likely source and, given the wide concentration range of PCDD/Fs that has been found in clays, a critical control point for PCDD/Fs entrance to the food supply. PMID:23234292

Huwe, J K; Archer, J C

2013-01-01

223

Rare earth element and clay minerals of paddy soils from the central region of the Mekong River, Laos  

Microsoft Academic Search

The rare earth elements (REE) content, particle-size distribution, and clay mineralogical composition were analyzed for the paddy soils collected from the central region of the Mekong River, Laos, to study the origin and inherent potentiality of soils. REE as the chondrite-normalized curve of the plot of Ce\\/Eu against Eu\\/Sm were found to be useful for grouping soils according to their

K. Egashira; K. Fujii; S. Yamasaki; P. Virakornphanich

1997-01-01

224

Minerals  

NSDL National Science Digital Library

This slide show provides students with basic information on mineralogy. It explains how the term "mineral" is defined, the properties that are used to identify minerals, their importance in daily life, and some general facts. For each identifying property, an example mineral and photograph are provided. Addresses to websites with additional information are also included.

Passow, Michael

225

Variability of fluvial sediment supply to the Laptev Sea continental margin during Late Weichselian to Holocene times: implications from clay-mineral records  

NASA Astrophysics Data System (ADS)

Three sediment cores from the Laptev Sea continental margin were investigated for their clay mineralogy by X-ray diffraction to study the fluvial sediment supply since the late Weichselian. In the study area, the clay-mineral composition of surface sediments is characterized by distinct regional variations. The source area for smectite in the eastern Eurasian Basin is the Putoran Plateau drained by the Khatanga and Yenisei rivers. Currents caused by river discharge and the inflow of Atlantic water masses along the Eurasian continental margin are responsible for sediment distribution. In the sediment cores, smectite and illite contents show an opposite trend which mainly results from variable smectite supply. During MIS 2 the amount of smectite on the Laptev Sea continental margin never exceeds 10 rel.%. Probably, reduced river discharge and the lowered sea level during MIS 2 caused a decreased sediment supply to the Laptev Sea. Additionally, the Putoran Plateau was covered by an ice sheet during the Late Weichselian preventing the erosion of smectite-rich soils. In contrast, maximum smectite contents (up to 30 rel.%) in Holocene sediments result from increased sediment input by the Khatanga River and from the Kara Sea through the Vilkitsky Strait and via St. Anna Trough into the western Laptev Sea.

Müller, Claudia; Stein, Ruediger

2000-08-01

226

Linking dynamics of soil microbial phospholipid fatty acids to carbon mineralization in a 13C natural abundance experiment: Impact of heavy metals and acid rain  

Microsoft Academic Search

A 13C natural abundance experiment including GC-c-IRMS analysis of phospholipid fatty acids (PLFAs) was conducted to assess the temporal dynamics of the soil microbial community and carbon incorporation during the mineralization of plant residues under the impact of heavy metals and acid rain. Maize straw was incorporated into (i) control soil, (ii) soil irrigated with acid rain, (iii) soil amended

Michael Stemmer; Andrea Watzinger; Karl Blochberger; Georg Haberhauer; Martin H. Gerzabek

2007-01-01

227

Clay-based Nanocomposites Possibilities and Limitations  

NASA Astrophysics Data System (ADS)

In the last decades, clay mineral based nanocomposites and polymer-clay nanocomposites (PCNC) have been proposed as very useful materials for many uses including photocatalysis, medicinal uses as tissue engineering or modified drug delivery systems. Clay minerals and especially montmorillonite, kaolinite, halloysite palygorskite and sepiolite are the most used clay minerals because of their high surface areas, colloidal dimensions of their particles and other properties. This lecture aims at reporting on very recent developments in the use of clay minerals and PCNC as materials with photocatalytic and medical interest.

Papoulis, Dimitris

2011-09-01

228

Clay mineral analysis of the Hirabayashi NIED drill core on the Nojima fault that ruptured in the 1995 Kobe Earthquake, southwest Japan  

NASA Astrophysics Data System (ADS)

A 1800-m-deep borehole was drilled at Nojima Hirabayashi and penetrated the Nojima fault that was activated at the time of the 1995 Hyogo-ken Nanbu Earthquake (Kobe Earthquake) in Japan. Three possible fracture zones were detected at depths of about 1140 m, 1300 m, and 1800 m. At first, we analyzed the mode of distribution of rocks, minerals and chemical elements in them. There is a foliated blue-gray gouge at a depth of 1140 m. So we infer that this is the central fault plane, and began our fracture zone analysis there, as follows. The degree of fracturing is evidently greater in the hanging wall than in the footwall. We estimated the relative amounts of minerals qualitatively, and we detected not only quartz, orthoclase, plagioclase, biotite and hornblende in the parent rock (granodiorite), but also kaolinite, smectite, laumontite, stilbite, calcite, ankerite and siderite, which are related to hydrothermal alteration. Biotite notably disappears in both the hanging wall and footwall across the central fault plane, although it disappears over a significantly greater distance in the hanging wall than in the footwall. Equally, we estimated the amounts of major chemical elements quantitatively. Al2O3, Fe2O3, MnO, TiO2, and P2O5 all decrease throughout this interval, except at a few points. H2O_{ and CO2 increase throughout the interval. Na2O increases in the region adjacent to the central fault plane, while MgO and CaO increase in the hanging wall and decrease in the footwall. SiO2 and K2O decrease in the hanging wall and increase in the footwall. Next, we particularly investigated about the clay minerals such as smectite. From the drill core, we separated the clay-size fraction and analyzed it by X-Ray Diffractometer (XRD). Incidentally, particle-size separations are based on Stokes_fs law. We prepared oriented samples for XRD and to make it, we used the glass slide method. We measured it both in the air-dried and ethylene glycol-solvated conditions. We analyzed the other fracture zones along this fault in the same way. As a result, about the mode of distribution of rocks minerals and chemical elements, the fracture zone at 1140 m depth is very similar to the fracture zone at 1800 m depth and differs significantly from the fracture zone at 1300 m depth. But, the results of the clay minerals are different among each fracture zone. In air-dried condition, d (001) of smectite are 15 angstrom (at 1140 m depth), 14 angstrom (at 1300 m depth), 14~12 angstrom (at 1800 m depth), respectively (In ethylene glycol-solvated conditions, they are all 17 angstrom). It may suggest the existence of different fluid circulation between shallower and deeper fracture zones.

Matsuda, T.; Omura, K.; Ikeda, R.; Awaji, D.

2002-12-01

229

U, Th, Pb and REE abundances and Pb 207/Pb 206 ages of individual minerals in returned lunar material by ion microprobe mass analysis.  

NASA Technical Reports Server (NTRS)

Results of ion microprobe analyses of Apollo 11, 12 and 14 material, showing that U, Th, Pb and REE are concentrated in accessory minerals such as apatite, whitlockite, zircon, baddeleyite, zirkelite, and tranquillityite. Th/U ratios are found to vary by over a factor of 40 in these minerals. K, Ba, Rb and Sr have been localized in a K rich, U and Th poor glass phase that is commonly associated with the U and Th bearing accessory minerals. Li is observed to be fairly evenly distributed between the various accessory phases. The phosphates have been found to have REE abundance patterns (normalized to the chondrite abundances) that are fairly flat, while the Zr bearing minerals have patterns that rise steeply, by factors of ten or more, from La to Gd. All the accessory minerals have large negative Eu anomalies. Radiometric age dates (Pb 207/Pb 206) of the individual U and Th bearing minerals compare favorably with the Pb 207/Pb 206 age of the bulk rocks.

Andersen, C. A.; Hinthorne, J. R.

1972-01-01

230

Interaction of biological molecules with clay minerals: a combined spectroscopic and sorption study of lysozyme on saponite.  

PubMed

The interaction of hen egg white lysozyme (HEWL) with Na- and Cs-exchanged saponite was investigated using sorption, structural, and spectroscopic methods as a model system to study clay-protein interactions. HEWL sorption to Na- and Cs-saponite was determined using the bicinchoninic acid (BCA) assay, thermogravimetric analysis, and C and N analysis. For Na-saponite, the TGA and elemental analysis-derived sorption maximum was 600 mg/g corresponding to a surface coverage of 0.85 ng/mm(2) with HEWL occupying 526 m(2)/g based on a cross-sectional area of 13.5 nm(2)/molecule. HEWL sorption on Na-saponite was accompanied by the release of 9.5 Na(+) ions for every molecule of HEWL sorbed consistent with an ion exchange mechanism between the positively charged HEWL (IEP 11) and the negatively charged saponite surface. The d-spacing of the HEWL-Na-saponite complex increased to a value of 4.4 nm consistent with the crystallographic dimensions of HEWL of 3 × 3 × 4.5 nm. In the case of Cs-saponite, there was no evidence of interlayer sorption; however, sorption of HEWL to the "external" surface of Cs-saponite showed a high affinity isotherm. FTIR and Raman analysis of the amide I region of the HEWL-saponite films prepared from water and D(2)O showed little perturbation to the secondary structure of the protein. The overall hydrophilic nature of the HEWL-Na-saponite complex was determined by water vapor sorption measurements. The clay retained its hydrophilic character with a water content of 18% at high humidity corresponding to 240 H(2)O molecules per molecule of HEWL. PMID:22047516

Johnston, Cliff T; Premachandra, Gnanasiri S; Szabo, Tamas; Lok, Joyce; Schoonheydt, Robert A

2012-01-10

231

The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum oxide minerals: a time-resolved XAFS study  

NASA Astrophysics Data System (ADS)

In this study kinetic investigations were combined with X-ray Absorption Fine Structure (XAFS) measurements to determine Ni sorption processes on pyrophyllite, gibbsite, and montmorillonite over extended time periods (min-months). The kinetic investigations revealed that Ni sorption reactions (pH = 7.5, [Ni] initial = 3 mM, I = 0.1 M (NaNO 3)) were initially fast (8-35% of the initial Ni was removed within the first 40 min). Thereafter, the rate of sorption decreased significantly and depended on the type of mineral surface. For the Ni/pyrophyllite system Ni removal was almost complete after a reaction time of 24h while for the Ni/gibbsite and Ni/montmorillonite systems metal sorption continued up to ?2 months. XAFS data revealed the presence of a mixed Ni/Al phase in the Ni/pyrophyllite and Ni/gibbsite systems after a reaction time of minutes. These results suggest that adsorption and nucleation processes (mixed Ni/Al phase formation) can occur simultaneously over time scales of only minutes. However, our finding of a fast growing mixed Ni/Al phase cannot be extrapolated to other sorption systems. A reaction time of 48 h was required for the presence of a mixed Ni/Al phase in the Ni/mormorillonite system. As reaction time progressed, the number of second neighbor Ni atoms (N Ni-Ni) at a distance of ?3.05 Å increased in all sorption systems, suggesting further growth of a mixed Ni/Al phase with increasing reaction time. Our study suggests that three phenomena occur at the mineral/liquid interface: (1) nonspecific (i.e, outer- sphere complexation) and/or specific adsorption (i.e., inner-sphere complexation), (2) dissolution of Al, and (3) nucleation of a mixed Ni/Al phase. The rate-limiting step is the dissolution of Al from the surface, which depends on the mineral substrate. Using the Ni linear sorption rates observed in the Ni/gibbsite and Ni/montmorillonite systems and assuming the Ni/Al ratios in our sorption samples are within the range of Ni/Al ratios provided in the literature (1.3-5.6), one can estimate an average Al dissolution rate which seems to be enhanced compared to the Al dissolution rates of the minerals alone. This finding indicates that the dissolution of clay and aluminum oxide minerals can be promoted by metal ions such as Ni(II) through the formation of a mixed Ni/Al phase.

Scheidegger, André M.; Strawn, Daniel G.; Lamble, Geraldine M.; Sparks, Donald L.

1998-07-01

232

Spectral variability of plagioclase-mafic mixtures (1): Effects of chemistry and modal abundance in reflectance spectra of rocks and mineral mixtures  

NASA Astrophysics Data System (ADS)

Remote sensing from lunar highland and from Hermean surface showed reflectance spectra with no detectable absorption bands in the visible and near infrared, and recently M3 data from the lunar surface (e.g., Orientale Basin) have shown spectra with a weak absorption band centered at 1250 nm. Those terrains were generally interpreted as plagioclase rich regions. Plagioclase, however, has often been considered a spectrally transparent and almost featureless mineral. So it is difficult to recognize its presence and to quantify the abundance of this mineral even if it is one of the most important mineralogical component of the planetary surfaces.

Serventi, Giovanna; Carli, Cristian; Sgavetti, Maria; Ciarniello, Mauro; Capaccioni, Fabrizio; Pedrazzi, Giuseppe

2013-09-01

233

Phase transitions and chain dynamics of surfactants intercalated into the galleries of naturally occurring clay mineral magadiite.  

PubMed

We investigate conformational dynamics and phase transitions of surfactant molecules confined in the layered galleries of the organo-modified, natural polysilicate clay, magadiite. We have shown that our approach to studying this class of materials is capable of delivering detailed information on the molecular mobility of the confined molecules. From the analysis of the measured heteronuclear dipolar couplings, the orientational order parameters of the C-H bonds along the hydrocarbon chain have been determined. Three phases have been observed in the nanocomposite, characterized by distinct dynamical states of the surfactant. At room temperature, restricted mobility of the molecules led to the adoption of an essentially all-trans conformation by the chains. This behavior can be described by a model incorporating small-angle wobbling around the long molecular axes of the chains. Upon heating, dynamic transformation takes place, resulting in a rotator type solid phase where molecules in extended all-trans conformations undergo fast and unrestricted rotation about their respective symmetry axes. The second phase transition is associated with chain melting and the onset of translational dynamics and results in an essentially liquid-crystalline-like state of the organic component. The mobility of the surfactant is one of the key factors facilitating the efficient penetration of macromolecules in the process of preparing of polymer/organoclay nanocomposites. The exploration of dynamic properties of the functionalizing organic layer should provide important input into the improved design of new organic-inorganic hybrid materials. PMID:24921951

Kharkov, Boris B; Corkery, Robert W; Dvinskikh, Sergey V

2014-07-01

234

Clay Exploration  

NSDL National Science Digital Library

In this activity, learners explore the possibilities of clay as a natural material. At three stations, learners create sculptures, use natural items such as small pebbles, twigs, and pinecones to embellish clay structures, and paint with clay. These activities help learners discover the sensory qualities of clay as a medium.

Museum, Chicago C.

2008-01-01

235

Sorption of N2 and EGME vapors on some soils, clays, and mineral oxides and determination of sample surface areas by use of sorption data  

USGS Publications Warehouse

Vapor sorption isotherms of ethylene glycol monoethyl ether (EGME) at room temperature and isotherms of N2 gas at liquid nitrogen temperature were determined for various soils and minerals. The N2 monolayer capacities [Qm (N2)] were calculated from the BET equation and used to determine the surface areas. To examine whether EGME is an appropriate adsorbate for determination of surface areas, the apparent EGME monolayer capacities [Qm (EGME)ap] were also obtained by use of the BET equation. For sand, aluminum oxide, kaolinite, hematite, and synthetic hydrous iron oxide, which are relatively free of organic impurity and expanding/solvating minerals, the Qm (EGME)ap values are in good conformity with the corresponding Qm (N2) values and would give surface areas consistent with BET (N2) values. For other samples (Woodburn soil, a natural hydrous iron oxide, illite, and montmorillonite), the Qm (EGME)ap values overestimate the Qm (N2) values from a moderate to a large extent, depending on the sample. A high-organic-content peat shows a very small BET (N2) surface area; the EGME/ peat isotherm is linear and does not yield a calculation of the surface area. Large discrepancies between results of the two methods for some samples are attributed to the high solubility of polar EGME in soil organic matter and/ or to the cation solvation of EGME with solvating clays. The agreement for other samples is illustrative of the consistency of the BET method when different adsorbates are used, so long as they do not exhibit bulk penetration and/or cation solvation. ?? 1993 American Chemical Society.

Chiou, C. T.; Rutherford, D. W.; Manes, M.

1993-01-01

236

Rare-earth mobility across an interface and also beyond between selected soil clay mineral particles and roots of a selected plant interface: A view based on an experimental study.  

NASA Astrophysics Data System (ADS)

Some recent suggestions of the essentiality of rare-earth elements (REE) for plants have generated much interest in gathering information about processes of mineral weathering in root environments and acquisition of REE by plants from such environments. An additional recent interest on plant acquisition of metals is gaining ground in finding out the measures of plant contribution of various metals present in river water at a regional or global scale. To monitor the path of transfer of REE from a clay mineral rich soil medium to roots of a plant, a species of poplar plant (Populus eugenei) was grown, using small cuttings of stems from a previous poplar plant, in a Ca-smectite clay as a soil medium under a laboratory condition. The <2-micrometer fraction of the clay prior to the planting of the poplar had a total REE concentration of 275 ppm . In contrast , the root attached >2-micron fraction clay had a concentration of 203 ppm. The relatively low concentration for the root clay was accompanied by a slight enrichment in LREE (light rare-earth element) with a small Ce negative anomaly as compared to the equivalent fine clay fraction having no influence of the plant. The translocation of the clay REE from the apparently rhizosphere environment to the roots was, as expected in conformity with the REE fractionation that was observed in the root clays, marked by an enrichment in HREE (heavy rare-earth element), but with some positive Ce, Eu, and Gd anomalies, for the plant roots relative to the clays attached to the roots. The total REE concentration of the plant roots was nearly 39 ppm per gram of dry material. New stems grown from earlier (older) stems had REE concentrations of about 0.19 ppm per gram of dry material, whereas old stems from which new shoots grew (making up the new stems) had concentrations of about 0.22 ppm per gram of dry material. The new stems were found to be only slightly enriched in LREE but with a positive Eu anomaly relative to the older stems from which the new stems grew. The leaves that grew from new stems had a REE concentration of nearly 14 ppm per gram of dry material. The new leaves, however, were HREE enriched with negative anomalies of Sm, Eu, and Gd relative to the new stems from which the leaves grew. The REE patterns in plant organs are reflective of intercellular processes of enzyme influence coupled with reductive adsorptive mechanisms. If river waters could be found with an HREE trend for the dissolved REE, plant organs releasing such REE following decomposition could be a contributing factor to this trend in river waters.

Weber, R.; Schneider, J.; Chaudhuri, S.

2009-04-01

237

Selected Great Basin Playa Clays.  

National Technical Information Service (NTIS)

Mineralogical studies of samples from Deep Springs Playa, Calif., Mud Lake and Humboldt Playa, Nevada, Sevier Playa, Utah and the Animas Playa, New Mex., indicate that the mica-type clay minerals illite, vermiculite, and montmorillonite are prominent in t...

N. Guven P. F. Kerr

1965-01-01

238

21 CFR 186.1256 - Clay (kaolin).  

Code of Federal Regulations, 2013 CFR

...powder. There are at least three different minerals, kaolinite, dickite, and nacrite, classified as kaolin. Kaolinite or china clay is whiter, less contaminated with extraneous minerals, and less plastic in water. (b) In accordance...

2013-04-01

239

21 CFR 186.1256 - Clay (kaolin).  

Code of Federal Regulations, 2010 CFR

...white to yellowish or grayish fine powder. There are at least three different minerals, kaolinite, dickite, and nacrite, classified as kaolin. Kaolinite or china clay is whiter, less contaminated with extraneous minerals, and less...

2010-01-01

240

21 CFR 186.1256 - Clay (kaolin).  

Code of Federal Regulations, 2010 CFR

...white to yellowish or grayish fine powder. There are at least three different minerals, kaolinite, dickite, and nacrite, classified as kaolin. Kaolinite or china clay is whiter, less contaminated with extraneous minerals, and less...

2009-04-01

241

Enzyme-clay interactions and their impact on transformations of natural and anthropogenic organic compounds in soil  

SciTech Connect

Soil is a living system in which enzymes are present either free in solution or bound to clay and clay-humus complexes. Enzyme-clay interactions play a key role in transforming organic compounds in soil environments where the decomposition and synthetic processes are largely catalyzed by enzymes. Scientific evidence indicates that mineral colloids take part in the catalysis of degradative and synthetic reactions of organic compounds. Such information is essential to understanding the role of mineral colloids, the hidden half of the enzyme-mineral colloid complexes, in catalytic reactions. Despite the abundant literature on the enzyme interactions with pure crystalline aluminosilicates, the nature of enzyme association with soil constituents, including both clean and coated clay minerals and other mineral colloids, and the effect on soil processes still remain unclear. This study integrates the existing information, including recent findings on enzyme-mineral colloid interactions and their effect on natural and anthropogenic organic compound transformation in soil. Further, the study focuses on the catalytic role of enzyme-clay complex surfaces in toxic industrial and agricultural compound bioremediation in soil and water environments.

Naidja, A.; Huang, P.M.; Bollag, J.M.

2000-06-01

242

Mineral nanoparticles in dispersed soils  

Microsoft Academic Search

The chemical-mineral composition and morphological features of mineral nanoparticles of clay soils have been studied. In the\\u000a clay soils of the Moscow moraine, nanoparticles are found to be localized in the surface microcavities of sand and silt grains\\u000a covered with clay films. They have predominantly anisometric configurations and comprise mainly mixed-layered clay minerals\\u000a and ferric oxides. The distinctive features of

V. N. Sokolov; M. S. Chernov; V. G. Shlykov; O. V. Razgulina; D. I. Yurkovets; V. V. Krupskaya

2008-01-01

243

Clay Houses  

ERIC Educational Resources Information Center

In this article, the author describes a project designed for fourth-graders that involves making clay relief sculptures of houses. Knowing the clay houses will become a family heirloom makes this lesson even more worth the time. It takes three classes to plan and form the clay, and another two to underglaze and glaze the final products.

Pedro, Cathy

2011-01-01

244

The clay mineralogy of sediments related to the marine Mjølnir impact crater  

NASA Astrophysics Data System (ADS)

The 40 km diameter Mjølnir Crater is located on the central Barents Sea shelf, north of Norway. It was formed about 142 ± 2.6 Myr ago by the impact of a 1­2 km asteroid into the shallow shelf clays of the Hekkingen Formation and the underlying Triassic to Jurassic sedimentary strata. A core recovered from the central high within the crater contains slump and avalanche deposits from the collapse of the transient crater and central high. These beds are overlain by gravity flow conglomerates, with laminated shales and marls on top. Here, impact and post-impact deposits in this core are studied with focus on clay mineralogy obtained from XRD decomposition and simulation analysis methods. The clay-sized fractions are dominated by kaolinite, illite, mixed-layered clay minerals and quartz. Detailed analyses showed rather similar composition throughout the core, but some noticeable differences were detected, including varying crystal size of kaolinite and different types of illites and illite/smectite. These minerals may have been formed by diagenetic changes in the more porous/fractured beds in the crater compared to time-equivalent beds outside the crater rim. Long-term post-impact changes in clay mineralogy are assumed to have been minor, due to the shallow burial depth and minor thermal influence from impact-heated target rocks. Instead, the clay mineral assemblages, especially the abundance of chlorite, reflect the impact and post-impact reworking of older material. Previously, an ejecta layer (the Sindre Bed) was recognized in a nearby well outside the crater, represented by an increase in smectite-rich clay minerals, genetically equivalent to the smectite occurring in proximal ejecta deposits of the Chicxulub crater. Such alteration products from impact glasses were not detected in this study, indicating that little, if any, impact glass was deposited within the upper part of the crater fill. Crater-fill deposits inherited their mineral composition from Triassic and Jurassic sediments underlying the impact site.

Dypvik, H.; Ferrell, R. E., Jr.; Sandbakken, P. T.

2003-10-01

245

Mineralogy and instrumental neutron activation analysis of seven National Bureau of Standards and three Instituto de Pesquisas Tecnologicas clay reference samples  

USGS Publications Warehouse

The concentrations of 3 oxides and 29 elements in 7 National Bureau of Standards (NBS) and 3 Instituto de Pesquisas Techno16gicas (IPT) reference clay samples were etermined by instrumental neutron activation analysis. The analytical work was designed to test the homogeneity of constituents in three new NBS reference clays, NBS-97b, NBS-98b, and NBS-679. The analyses of variance of 276 sets of data for these three standards show that the constituents are distributed homogeneously among bottles of samples for 94 percent of the sets of data. Three of the reference samples (NBS-97, NBS-97a, and NBS-97b) are flint clays; four of the samples (NBS-98, NBS-98a, NBS-98b, and IPT-32) are plastic clays, and three of the samples (NBS-679, IPT-28, and IPT-42) are miscellaneous clays (both sedimentary and residual). Seven clays are predominantly kaolinite; the other three clays contain illite and kaolinite in the approximate ratio 3:2. Seven clays contain quartz as the major nonclay mineral. The mineralogy of the flint and plastic clays from Missouri (NBS-97a and NBS-98a) differs markedly from that of the flint and plastic clays from Pennsylvania (NBS-97, NBS-97b, NBS-98, and NBS-98b). The flint clay NBS-97 has higher average chromium, hafnium, lithium, and zirconium contents than its replacement, reference sample NBS-97b. The differences between the plastic clay NBS-98 and its replacement, NBS-98b, are not as pronounced. The trace element contents of the flint and plastic clays from Missouri, NBS-97a and NBS-98a, differ significantly from those of the clays from Pennsylvania, especially the average rare earth element (REE) contents. The trace element contents of clay sample IPT-32 differ from those of the other plastic clays. IPT-28 and IPT-42 have some average trace element contents that differ not only between these two samples but also from all the other clays. IPT-28 has the highest summation of the average REE contents of the 10 samples. The uranium content of NBS-98a, 46 parts per million, is very much higher than that of the other clays. Plots of average REE contents of the flint and plastic clays, normalized to chondritic abundances, show that the clays from Missouri differ from the same types of clay from Pennsylvania. The plot of REE contents for the miscellaneous clays shows that the normalized means for the elements lanthanum through samarium for IPT-28 are much greater than those for the other miscellaneous clays. The means for the elements europium through lutetium are similar for all three miscellaneous clays.

Hosterman, John W.; Flanagan, F. J.; Bragg, Anne; Doughten, M. W.; Filby, R. H.; Grimm, Catherine; Mee, J. S.; Potts, P. J.; Rogers, N. W.

1987-01-01

246

Minerals Yearbook: Cuba, 2006.  

National Technical Information Service (NTIS)

Nickel was the most important mineral commodity to the Cuban economy followed by cobalt, which was produced as a byproduct of nickel mining. Other minerals produced in the country included cement, clays, crushed stone, feldspar, salt, and silica sand. Cub...

O. Bermudez-Lugo

2008-01-01

247

Light-stable-isotope studies of spring and thermal waters from the Roosevelt Hot Springs and Cove Fort/Sulphurdale Thermal areas and of clay minerals from the Roosevelt Hot Springs thermal area  

SciTech Connect

The isotopic compositions of hydrogen and oxygen have been determined for spring waters and thermal fluids from the Roosevelt Hot Springs and Cove Fort-Sulphurdale thermal areas, for clay mineral separates from shallow alteration of the acid-sulfate type in the Roosevelt Hot Springs area, and for spring and well waters from the Goshen Valley area of central Utah. The water analyses in the Roosevelt Hot Springs thermal area confirm the origin of the thermal fluids from meteoric water in the Mineral Range. The water analyses in the Cove Fort-Sulphurdale thermal area restrict recharge areas for this system to the upper elevations of the Pavant and/or Tushar Ranges. The low /sup 18/O shift observed in these thermal fluids (+0.7 permil) implies either high water/rock ratios or incomplete isotope exchange or both, and further suggests minimal interaction between the thermal fluid and marble country rock in the system. Hydrogen and oxygen-isotope data for clay mineral separates from shallow alteration zones in the Roosevelt Hot Springs thermal system suggest that the fluids responsible for the shallow acid-sulfate alteration were in part derived from condensed steam produced by boiling of the deep reservoir fluid. The isotope evidence supports the chemical model proposed by Parry et al. (1980) for origin of the acid-sulfate alteration at Roosevelt Hot Springs. The isotope analyses of spring and well waters from the Goshen Valley area indicate only a general correlation of isotope composition, salinity and chemical temperatures.

Bowman, J.R.; Rohrs, D.T.

1981-10-01

248

Chemical and Clay Mineral Properties of a Highly Weathered Soil from the Colombian Llanos Orientales. R(CO-631-42-W363).  

National Technical Information Service (NTIS)

The author presents the results of quantitative clay mineralogical investigations on a soil from the Llanos Orientales (Eastern Savannas) region of Columbia, South America and discusses some possible agronomic effects of Al-chlorite presence in highly wea...

R. M. Weaver

1972-01-01

249

The ProteoMiner in the proteomic arena: a non-depleting tool for discovering low-abundance species.  

PubMed

Combinatorial ligand libraries, composed by millions of hexapeptides, are here reviewed in terms of their ability of capturing the low-abundance proteome. First, the physico-chemical properties of such libraries are dealt with, especially in regard to the proper length of the bait. The capturing ability of single amino acids has been assessed demonstrating that there exist a protein adsorption capability dichotomy, by which 8 amino acids (Arg, Lys, His, Phe, Tyr, Trp, Val and Leu) are classified as interacting with a large number of proteins with all the remaining amino acids with limited capturing capabilities. The highest performance in capturing the largest possible population of proteins is offered by the three hydrophobic, aromatic amino acids, i.e. Phe, Tyr and Trp, suggesting that hydrophobic motifs are those responsible for the strongest, and most frequently occurring, interactions. By exploring baits ranging from single, individual amino acids, to di-, tri-, tetra- penta- and hexapeptides, it was demonstrated that the 6-mer baits are the ones with the most promising length for capturing the largest possible population of proteins and that probably longer lengths would hardly be needed. Some examples are given on the ability to explore the low-abundance proteome in two systems, notably chicken egg white and yolk. In both cases, by using the peptide library methodology, it is possible to detect at least twice as many protein species as compared to the best results obtained so far with the most advanced proteomics studies using highly sophisticated mass spectrometry tools. PMID:18603494

Boschetti, Egisto; Righetti, Pier Giorgio

2008-08-21

250

Smart Clays: SAFOD Samples Confirm the Key Role of Newly-formed Clays in Shallow Fault Zones  

NASA Astrophysics Data System (ADS)

Analysis of fault rocks from drill-cores of the San Andreas Fault Observatory at Depth (SAFOD) project in Parkfield (CA) confirm our original hypothesis that active clay growth can occur locally at shallow conditions and that such clay localization affect fault mechanics and fault creep in particular. SAFOD fault rocks contain a variety of newly formed clay minerals including smectite, illite-smectite and chlorite-smectite, as well as illite and chlorite. Brecciated host rock fragments are abundantly coated by polished and/or striated thin-films of hydrated clay minerals, creating an interconnected and pervasive network of displacement surfaces. Ar encapsulation dating of mixed-layer nanocoatings demonstrates recent crystallization and reveal an 'older' fault strand (~8 Ma) at 3066 m measured depth and a 'younger' fault strand (~4 Ma) at 3296 m measured depth. Today, the younger strand is the site of active creep behavior, demonstrating continued (re)activation of clay-weakened zones. Recent experimental work on aseismically creeping segments of SAFOD samples showed frictional strengths that are significantly weaker than neighboring wall rocks, offering independent validation of our model. Using a range of analytical methods that include X-ray diffraction, X-ray goniometry, elemental analysis and electron microscopy, we determined the location and nature of smectitic clay minerals in borehole samples, to assess the extent of smectitic phases in space and depth, any fault zone fabric development, and the swelling behavior of smectitic phases within the fault zone. Beyond the occurrence of illite-smectite in these relatively shallow fault rocks, the localized concentration of chlorite-smectite can extend the role of smectitic clays to depths down to ~10 km. We conclude that ultrathin hydrous clay films, or nanocoatings, on displacement surfaces play a key role in influencing weak fault and creep behavior along the San Andreas Fault at Parkfield, and likely in shallow faults systems elsewhere. These results indicate that scenarios involving talc/serpentine phases or locally enhanced fluid pressure as explanations for mechanically weak crustal faults are not required.

Schleicher, A.; van der Pluijm, B.; Warr, L. N.

2013-12-01

251

Chemical disaggregation of kaolinitic claystones (tonsteins and flint clays)  

USGS Publications Warehouse

The coarse, non-clay fraction of many flint-like kaolinitic claystones often contains mineral grains diagnostic of the claystone's origin and, in the case of tonsteins (altered volcanic ashes), may also provide minerals suitable for radiometric dating. Separation of the non-clay mineral fraction is often difficult because flint clays and flint-like clays resist slaking in water and thus are difficult to disaggregate. Chemical disaggregation of resistant kaolinitic claystones may be achieved by immersion in either hydrazine monohydrate or DMSO for periods ranging from one day to several weeks. Generally, hydrazine monohydrate works more quickly and efficiently than DMSO to disaggregate most kaolinitic claystones and flint clays.

Triplehorn, D. M.; Bohor, B. F.; Betterton, W. J.

2002-01-01

252

Clay composition and swelling potential estimation of soils using depth of absorption bands in the SWIR (1100-2500 nm) spectral domain  

NASA Astrophysics Data System (ADS)

Swelling soils contain clay minerals that change volume with water content and cause extensive and expensive damage on infrastructures. Presence of clay minerals is traditionally a good estimator of soils swelling and shrinking behavior. Montmorillonite (i.e. smectite group), illite, kaolinite are the most common minerals in soils and are usually associated to high, moderate, and low swelling potential when they are present in significant amount. Characterization of swelling potential and identification of clay minerals of soils using conventional analysis are slow, expensive, and does not permit integrated measurements. SWIR (1100-2500 nm) spectral domain are characterized by significant spectral absorption bands related to clay content that can be used to recognize main clay minerals. Hyperspectral laboratory using an ASD Fieldspec Pro spectrometer provides thus a rapid and less expensive field surface sensing that permits to measure soil spectral properties. This study presents a new laboratory reflectance spectroscopy method that used depth of clay diagnostic absorption bands (1400 nm, 1900 nm, and 2200 nm) to compare natural soils to synthetic montmorillonite-illite-kaolinite mixtures. We observe in mixtures that illite, montmorillonite, and kaolinite content respectively strongly influence the depth of absorption bands at 1400 nm (D1400), 1900 nm (D1900), and 2200 nm (D2200). To attenuate or removed effects of abundance and grain size, depth of absorption bands ratios were thus used to performed (i) 3D (using D1900/D2200, D1400/D1900, and D2200/D1400 as axis), and (ii) 2D (using D1400/D1900 and D1900/D2200 as axis) diagrams of synthetic mixtures. In this case we supposed that the overall reduction or growth of depth absorption bands should be similarly affected by the abundance and grain size of materials in soil. In 3D and 2D diagrams, the mixtures define a triangular shape formed by two clay minerals as external envelop and the three clay minerals mixtures are located inside of the triangular shape. Clay composition of natural soils were estimated using 3D and 2D diagrams used as standard template from: (i) the average clay composition of the three closer mixtures when soil samples were plotted inside the triangular distribution of mixtures; and (ii) the closer mixture when the soil sample were plotted outside of the triangular distribution of mixtures. Comparison with X-ray diffraction analysis show reliable prediction of montmorillonite content that were used to estimate the swelling potential of soils. This method allows a simple, fast, and low cost method that classes soils into four swelling classes based on comparison with Methylene Blue test, and could be used as complementary or alternative method to traditional geotechnical analysis.

Dufréchou, Grégory; Granjean, Gilles; Bourguignon, Anne

2014-05-01

253

Surface Modification of Clays and Related Materials  

Microsoft Academic Search

This review analyzes various ways by which the surfaces of clay particles and related minerals can be non?covalently modified, as well as some of the analytical approaches with which these surface modifications can be measured and quantified. Among the principal methods of modification of the surface properties of clays and other metal oxide surfaces is treatment with cationic surfactants comprising

C. J. van Oss; R. F. Giese

2003-01-01

254

A possible energetic role of mineral surfaces in chemical evolution.  

PubMed

The postulated roles of clays and other minerals in chemical evolution and the origin of life are reconsidered in terms of the interaction of these minerals with penetrating sources of energy such as ionizing radiation and mechanical stress. This interaction, including such facets as excitation, degradation, storage, and transfer, is considered here with regard to its profound potential for altering the capabilities of minerals to serve both as substrates for prebiological chemistry and as inorganic prototypic life forms. The interaction of minerals and energy in relationship to surface chemistry is discussed in terms of the spectroscopic properties of minerals, the interaction of energy with condensed phases, some commonly accepted concepts of heterogeneous catalysis in the absence of electronic energy inputs, and some commonly accepted and novel means by which surface activity might be enhanced in the presence of energy inputs. An estimation is made of the potential contribution of two poorly characterized prebiotic energy sources, natural radioactive decay and triboelectric energy. These estimates place a conservative lower limit on their prebiotic abundance. Also some special properties of these energy sources, relative to solar energy, are pointed out which might give them particular suitability for driving reactions occurring under geological conditions. Skeletal support for this broadly defined framework of demonstrated and potential relationships between minerals, electronic excitation, and surface reactivity, as applied to chemical evolution, is provided from the results of our studies on 1/1 clays. We have discovered and partially characterized a number of novel luminescent properties of these clays, that indicate energy storage and transfer processes in clays. These luminescent properties are interpreted in relationship to the electron spin resonance phenomena, to provide a basis for estimating the potential significance of energy storage and transduction in monitoring or driving clay surface chemistry. Consideration of the electronic structure of abundant minerals in terms of band theory and localized defect centers provides a predictive theoretical framework from which to rationalize the capacity of these materials to store and transduce energy. The bulk crystal is seen as a collecting antenna for electronic energy, with the defect centers serving as storage sites. The clay properties produced by isomorphic substitution appear to be intimately associated with all of the life-mimetic chemical processes that have been attributed to clays.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3903606

Coyne, L M

1985-01-01

255

Probability of adsorption of peptide (CR3-1, S2) chains on clay minerals by coarse-grained Monte Carlo simulation  

NASA Astrophysics Data System (ADS)

A coarse-grained description is used to study the structure and dynamics of peptide chains (CR3-1, S2) in presence of a clay surface on a cubic lattice. A peptide chain is represented by the specific sequence of amino acids. Specificity of residues is captured via an interaction matrix based on the insight gained from the atomistic simulation, i.e., each residue interacts with surrounding residues, solvent, and the clay surface with a unique interaction potential. We use a standard LJ potential with its coefficient controlled by the interaction matrix. Simulations are performed with a number of peptide chains. Along with the global energy and dynamics of peptides, we keep track of mobility, energy (total and adsorption), and correlation with the local structure from the density profiles of each residue. Based on the analysis of local and global quantities, we are able to assess the probability of adsorption of peptides to clay surface in agreement with experiment. The probability of adsorption of S2 is found to be much higher than that of CR3-1 in which S2 is anchored by Lysine. The procedure is complementary to biopanning experiments since it allows screening a large number of peptides (more than 10E+5) on the surface to estimate their binding potential.

Pandey, Ras B.; Heinz, Hendrik; Farmer, Barry L.; Jones, Sharon; Drummy, Lawrence F.; Naik, Rajesh R.

2009-03-01

256

Fine-grained clay fraction (,0.2 {mu}m): An interesting tool to approach the present thermal and permeability state in active geothermal systems  

SciTech Connect

We have investigated by X-ray diffraction the very fine grained secondary minerals (< 0.2 {micro}m) developed in geothermal systems, in relation with their present thermal and permeability state. Because the smallest particles are the most reactive part of a rock, they are the youngest mineral phases of the geothermal fields. This study has been performed on two active geothermal fields: Milos field, Greece (130 < T < 320 C) and Chipilapa field, Salvador (90 < T < 215 C). In the Milos field, the mineralogical composition of the < 0.2 {micro}m clay fraction observed in the reservoir strongly differs from the overlying altered metamorphic schists in the presence of abundant quantities of saponite and talc/saponite interstratified minerals at unusually high temperature. These phases are considered to be kinetically control-led ''metastable'' minerals which rapidly evolve towards actinolite and talc for present temperatures higher than 300 C. Their occurrence is a good indicator of discharge in highly permeable zones. In the geothermal field of Chipilapa, the mineralogical composition of the < 0.2 {micro}m clay fractions fairly agrees with the temperatures presently measured in the wells, whereas several discrepancies may be pointed out from the compositions of coarser clay fractions (< 5 {micro}m) which contain minerals inherited from higher temperature stages. Permeable zones may be evidenced from an increase of expandable components in the interstratified minerals and a decrease of the coherent domain of the unexpandable clay particles (chlorite).

Patrier, P.; Papapanagiotou, P.; Beaufort, D.; Traineau, H.; Bril, H.

1992-01-01

257

Clay sized fraction and powdered whole-rock X-ray analyses from alluvial basin deposits in central and southern New Mexico  

USGS Publications Warehouse

As part of the study of the water quality and geochemistry of Southwest Alluvial Basins (SWAB) in parts of Colorado, New Mexico, and Texas, which is a Regional Aquifer-System Analysis (RASA) program, whole rock x-ray analysis and clay-size fraction mineralogy (x-ray) analysis of selected samples from alluvial basin deposits were done to investigate the types of minerals and clay types present in the aquifers. This was done to determine the plausible minerals and clay types in the aquifers that may be reacting with groundwater and affecting the water quality. The purpose of this report is only to present the whole rock x-ray and clay-fraction mineralogy data. Nineteen surface samples or samples from outcrop of Tertiary and Quaternary alluvial basin deposits in the central and southern Rio Grande rift were collected and analyzed. The analysis of the samples consisted of grain size analysis, and clay-size fraction mineralogy and semiquantitative analysis of the relative abundance of different clay mineral groups present. (USGS)

Anderholm, S. K.

1985-01-01

258

Clay energetics in chemical evolution  

NASA Technical Reports Server (NTRS)

Clays have been implicated in the origin of terrestrial life since the 1950's. Originally they were considered agents which aid in selecting, concentrating and promoting oligomerization of the organic monomeric substituents of cellular life forms. However, more recently, it has been suggested that minerals, with particular emphasis on clays, may have played a yet more fundamental role. It has been suggested that clays are prototypic life forms in themselves and that they served as a template which directed the self-assembly of cellular life. If the clay-life theory is to have other than conceptual credibility, clays must be shown by experiment to execute the operations of cellular life, not only individually, but also in a sufficiently concerted manner as to produce some semblance of the functional attributes of living cells. Current studies are focussed on the ability of clays to absorb, store and transfer energy under plausible prebiotic conditions and to use this energy to drive chemistry of prebiotic relevance. Conclusions of the work are applicable to the role of clays either as substrates for organic chemistry, or in fueling their own life-mimetic processes.

Coyne, L. M.

1986-01-01

259

Relationships between clay mineralogy, hydrothermal metamorphism, and topography in a Western Cascades watershed, Oregon, USA  

NASA Astrophysics Data System (ADS)

This study investigates variation in clay mineralogy and its relation to hydrothermal metamorphism, hillslope processes, and topography in the western Cascade Mountains. The study area is the drainage basin of Dorena Lake, a medium-sized (686 km 2) watershed located near Cottage Grove, OR. The Bohemia Mining District is on the southeastern rim of the watershed in a hydrothermally metamorphosed region associated with a set of granodiorite plutons. To characterize large-scale patterns of clay mineral distribution within the watershed, suspended sediments were collected from 43 stream locations. Samples of several metamorphosed and unaffected volcanic and volcaniclastic rocks were collected to help clarify metamorphic reaction processes. One active earthflow was also sampled. X-ray diffraction methods were used to determine the mineralogy of the clay-sized (<2 ?m) fraction of the samples. Clay mineralogy varies systematically across the watershed, and the three major stream tributaries carry sediment with distinct mineralogical signatures. Discrete minerals include kaolinite, smectite, chlorite, and illite. Interstratified kaolinite-smectite and chlorite-vermiculite (CV) are also present. The active earthflow and unmetamorphosed rock samples primarily contain smectite. In contrast, metamorphosed rock samples are composed of some combination of illite, interstratified illite-smectite, CV, and chlorite. Examination of clay mineral distribution reveals the effects of hydrothermal metamorphism in the mining district on clay mineralogy, hillslope processes, and landscape development. Compared with most of the watershed, the mining district has steeper slopes and higher elevations and lacks smectite almost entirely. Analyses of metamorphosed bedrock units indicate that smectite originally present in the rocks was converted to nonexpandable clay minerals during metamorphism. Induration of bedrock and loss of expandable clays resulted in thin soils and steep topography. Debris slides and flows are the dominant mass movement processes in this area; earthflows are noticeably absent, probably because thick, smectitic soils are lacking. Elsewhere in the watershed where smectite is abundant, slopes are more gentle; and both shallow and deep-seated mass movements are common. The clay mineralogy of bedrock and soils is thus integrally tied to the hillslope processes operating within the watershed and therefore affects the geomorphology of the landscape. High-relief, hydrothermally metamorphosed volcanic centers surrounded by weaker rocks in adjacent lowlands are common features in the western Cascade Mountains. These massifs were likely formed by differential erosion processes similar to those operating in the Dorena Lake watershed.

Ambers, Rebecca K. R.

2001-05-01

260

Constraints on Mineral-Phase Abundances and Compositions in the Low-Albedo Northern Plains of Mars using MGS-TES, OMEGA, and Laboratory Spectral Data.  

NASA Astrophysics Data System (ADS)

The abundances and compositions of mineral-phases in the low-albedo northern plains of Mars have been a focus of considerable study and debate in recent years. Large expanses of Acidalia Planitia surface materials are characterized by the MGS-TES Surface Type 2 (ST2) spectral endmember [1]. The ST2 spectrum is distinguished by a rounded, slightly V-shaped 800 to 1200 wavenumber region of absorption and uniform absorption at low wavenumbers. The same areas are also characterized by an OMEGA spectral signature that is relatively featureless, but with a strong blue slope (decreasing reflectance as a function of wavelength) from 0.9 to 2.6 microns [2]. A central question with both observations is whether they represent the spectral signature of a high-silica primary volcanic lithology (andesite) or the effects of chemical alteration on basaltic surface materials. Ambiguity in classifying the ST2 lithology arises because a spectral component of this unit (20-30 vol %) can be interpreted as volcanic siliceous glass [1, 3] (an abundant phase in andesite) or a combination of secondary phases found in altered basalt (amorphous silica-rich coatings, palagonite, smectite, and zeolite) [4-8]. Similarly, the OMEGA spectrum lacks evidence of distinct mafic mineral bands (found in andesite) as well as molecular vibration absorptions due to H2O and/or OH-, which might indicate the presence of well- crystalline alteration products and phyllosilicates [2]. Constraining these compositions is significant for understanding the petrogenesis of the Martian crust and its subsequent alteration. Identification of widespread andesite may imply an early episode of plate tectonics on Mars while altered basalt would indicate extensive surface-volatile interactions. The objective of this study is to combine TES and OMEGA observations of the low-albedo northern plains for comparison to laboratory thermal infrared and visible/near-infrared measurements of primary volcanic lithologies (basalt to dacite) and chemically weathered basalts from different terrestrial environments. Thermal infrared emission and visible/near-infrared reflectance measurements will be performed on rock chips, sorted particle sizes, and soil samples. Emission spectra have been acquired at Arizona State University using a Nicolet Nexus 670 FTIR spectrometer that has been modified to measure emitted energy over the range of 5 to 50 microns at 2 wavenumber spectral sampling. Bidirectional reflectance measurements from 0.32 to 2.55 microns at 0.05 micron sampling will be collected at the Brown University RELAB facility. Work by [5] on palagonitic alteration rinds developed on basaltic rocks demonstrates the effectiveness of combining wavelength regions in laboratory studies and applying results to orbital observations. In our study, we further this type of work by examining both unaltered volcanics and chemically altered basalts in an effort to constrain interpretations of the igneous lithology and the degree of secondary mineral-phase production in Acidalia Planitia. [1] Bandfield et al. (2000) Science, 287, 1626 1630. [2] Mustard et al. (2005) Science, 1594-1597. [3] Hamilton et al. (2001) JGR, 106, 14,733-14,746. [4] Wyatt and McSween (2002) Nature, 417, 263-266. [5] Morris et al. (2003) 6 Int. Mars. Conf, Abstract 3111. [6] Kraft et al. (2003) GRL, 30, 24, 2288, doi 10.1029.2003GL018848. [7] Ruff (2004) Icarus, 108, 131-143. [8] Michalski et al. (2005) Icarus, 174, 161-177.

Wyatt, M. B.; Mustard, J. F.

2006-12-01

261

Mineral mapping of tropical soils in land degradation areas through ASTER thermal infrared data  

NASA Astrophysics Data System (ADS)

The increasing loss of harvest areas in tropical humid and sub-humid regions is a comprehensive problem, but still underestimated. The main land degradation processes in these regions is related to erosion of arenitic rocks and formation of structured sandy soils, locally called in Brazil as “arenization”, but also generically called desertification. Such processes introduce several environmental damages such as increased erosion, reduction in soil fertility and decline of agricultural land use. The present work uses ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) Thermal Infrared data (TIR - 10 to 14 bands - 8.125-10.95 µm) to map quartz and clay minerals in areas of land degradation in the southern portion of Rio Grande do Sul State, Brazil. Using ASTER/TIR data it was possible to replicate important spectral diagnostic features related to the SiO reststrahlen band from clay minerals and quartz. The mapping of mineral abundance was produced using spectral index and band ratio methods. The results show that ASTER/TIR data were able to map these minerals in the tropical soil and to reveal the degree of mixtures among quartz, clay minerals and other land cover features. Areas simultaneously mapped as quartz-rich and with lower proportion of clay minerals indicate a wealth of sandy soils, scarce cover vegetation and excessive drainage, that leads to large nutrient losses. This approach allows a more precise and quantitative mapping of land degradation characteristics with important implications to the study of its dynamics in tropical environments.

Vicente, L. E.; Souza Filho, C. R.

2009-12-01

262

Fluid focusing and back-reactions in the uplifted shoulder of the Rhine rift system: a clay mineral study along the Schauenburg Fault zone (Heidelberg, Germany)  

Microsoft Academic Search

A retrograde sequence of fluid-controlled, low-temperature mineral reactions has been preserved along an east-west striking,\\u000a dextral-oblique-slip fault in the uplifted Rhine Graben shoulder. This fault (the Schauenburg Fault, near Heidelberg), juxtaposes\\u000a Permian rhyolite against Carboniferous (Variscan) granite and shows syn- or post-rift displacement of the north–south trending,\\u000a eastern boundary fault of the rift basin. Both mineral texture and rock fabric

A. M. Schleicher; L. N. Warr; B. A. van der Pluijm

2006-01-01

263

Searching for reciclability of modified clays for an environmental application  

NASA Astrophysics Data System (ADS)

Thanks to the development of the science and the technology of the nourishment in the last 50 years, there have revealed itself several new substances that can fulfill beneficial functions in the food, and these substances, named food additives, are today within reach of all. The food additives recover a very important role in the complex nourishing supply. The additives fulfill several useful functions in the food, which often we give for sat. Nevertheless the widespread use of food additives in the food production also influences the public health. The food industries, which are very important for the economy, spill residues proved from its activity that they have to be controlled to evaluate the environmental impact and to offer the necessary information about the quantitative evaluation of the chemical risk of the use of food additives for the public health. The clay materials have led to numerous applications in the field of public health (del Hoyo, 2007; Volzone, 2007) having been demonstrated its effectiveness as adsorbents of all contaminants. Some biodegradable materials are used for for adsorption of chemical contaminants: lignins (Valderrabano et al., 2008) and also clays and clay minerals, whose colloidal properties, ease of generating structural changes, abundance in nature, and low cost make them very suitable for this kind of applications. Among the strategies used at present to preserve the quality of the water and this way to diminish the environmental risk that supposes the chemical pollution, stands out the use of adsorbents of under cost, already they are natural or modified, to immobilize these compounds and to avoid the pollution of the water with the consequent reduction of environmental and economic costs. We have studied the adsorption of several contaminants related to the food industry by natural or modified clays, searching their interaction mechanisms and the possible recycling of these materials for environmental purposes and prevention of the health. We have used the FT-IR spectroscopy and DTA/TG studies to confirm the reciclability of these materials and the possible application in the industry to prevent the contamination. References -del Hoyo, C. (2007). Applied Clay Science. 36, 103-121.Layered Double Hydroxides and human health: An overview. -Valderrábano, M., Rodríguez-Cruz, S., del Hoyo, C., Sánchez-Martín, M.J. (2006). 4th International Workshop "Bioavalailability of pollutants and soil remediation". 1, 5-6. Physicochemical study of the adsorption of pesticides by lignins. -Volzone, C. (2007). Applied Clay Science. 36, 191-196. Retention of pollutant gases: Comparison between clay minerals and their modified products.

Del Hoyo Martínez, Carmen; Solange Lozano García, Marina; Sánchez Escribano, Vicente; Antequera, Jorge

2014-05-01

264

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS 13C NMR spectroscopy and low field T 1 NMR relaxometry  

Microsoft Academic Search

Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical–chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban

Pellegrino Conte; Cristina Abbate; Andrea Baglieri; Michéle Nègre; Claudio De Pasquale; Giuseppe Alonzo; Mara Gennari

2011-01-01

265

Characterizing regional soil mineral composition using spectroscopyand geostatistics  

USGS Publications Warehouse

This work aims at improving the mapping of major mineral variability at regional scale using scale-dependent spatial variability observed in remote sensing data. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and statistical methods were combined with laboratory-based mineral characterization of field samples to create maps of the distributions of clay, mica and carbonate minerals and their abundances. The Material Identification and Characterization Algorithm (MICA) was used to identify the spectrally-dominant minerals in field samples; these results were combined with ASTER data using multinomial logistic regression to map mineral distributions. X-ray diffraction (XRD)was used to quantify mineral composition in field samples. XRD results were combined with ASTER data using multiple linear regression to map mineral abundances. We testedwhether smoothing of the ASTER data to match the scale of variability of the target sample would improve model correlations. Smoothing was donewith Fixed Rank Kriging (FRK) to represent the mediumand long-range spatial variability in the ASTER data. Stronger correlations resulted using the smoothed data compared to results obtained with the original data. Highest model accuracies came from using both medium and long-range scaled ASTER data as input to the statistical models. High correlation coefficients were obtained for the abundances of calcite and mica (R2 = 0.71 and 0.70, respectively). Moderately-high correlation coefficients were found for smectite and kaolinite (R2 = 0.57 and 0.45, respectively). Maps of mineral distributions, obtained by relating ASTER data to MICA analysis of field samples, were found to characterize major soil mineral variability (overall accuracies for mica, smectite and kaolinite were 76%, 89% and 86% respectively). The results of this study suggest that the distributions of minerals and their abundances derived using FRK-smoothed ASTER data more closely match the spatial variability of soil and environmental properties at regional scale.

Mulder, V.L.; de Bruin, S.; Weyermann, J.; Kokaly, Raymond F.; Schaepman, M.E.

2013-01-01

266

Evaluation of Phosphatic Clay Disposal and Reclamation Methods. Volume 2. Mineralogy of Phosphatic Clays.  

National Technical Information Service (NTIS)

Twelve phosphatic clays and three sand tailings from Florida phosphate mining areas were examined by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and chemical analysis. Quantitative estimates of mineral species were made using sample XRD da...

A. E. Z. Wissa N. F. Fuleihan T. S. Ingra

1982-01-01

267

Behavior of halloysite clay under formamide treatment  

Microsoft Academic Search

Halloysite clay minerals are ubiquitous in soils and weathered rocks where they occur in a variety of particle shapes and hydration states. When both halloysite and kaolinite are present in a given sample, differentiation between the two minerals is problematic particularly when the halloysite constituent is dehydrated. Formamide intercalation test is widely used to differentiate halloysite-(7 Å) from kaolinite. The soil

Emmanuel Joussein; Sabine Petit; Bruno Delvaux

2007-01-01

268

Removal of chromium, nickel and cadmium from clays by in?situ electrokinetic remediation  

Microsoft Academic Search

This article presents the results of a research study that investigated the use of the in situ electrokinetic process for removing chromium, nickel, and cadmium from contaminated clays. For this study, electrokinetic experiments were conducted on two types of clays: kaolin, a commercial?grade soil consisting mainly of kaolinite clay mineral, and glacial till, a fíeld derived clay that possesses a

Krishna R. Reddy; Usha S. Parupudi

1997-01-01

269

Desorption of arsenic from clay and humic acid-coated clay by dissolved phosphate and silicate  

NASA Astrophysics Data System (ADS)

Arsenic (As) contaminated aquifers contain iron minerals and clays that strongly bind As at their surfaces. It was suggested that As mobilization is driven by natural organic matter (including fulvic acids (FA) and humic acids (HA)) present in the aquifers either via providing reducing equivalents for reductive dissolution of Fe(III) (hydr)oxides or via competitive desorption of As from the mineral surfaces. In the present study we quantified sorption of As(III) and As(V) to Ca 2+-homoionized illite (IL) and to kaolinite (Kao) as well as to HA-coated clays, i.e., illite-HA (IL-HA) and kaolinite-HA (Kao-HA) at neutral pH. Clay-HA complexes sorbed 28-50% more As than clay-only systems upon addition of 100 ?M As(III)/As(V) to 0.5 g of clay or HA-clay with Ca 2+ probably playing an important role for HA binding to the clay surface and As binding to the HA. When comparing sorption of As(V) and As(III) to clay and HA-clay complexes, As(V) sorption was generally higher by 15-32% than sorption of As(III) to the same complexes. IL and IL-HA sorbed 11-28% and 6-11% more As compared to Kao and Kao-HA, respectively. In a second step, we then followed desorption of As from Kao, Kao-HA, IL and IL-HA by 100 and 500 ?M phosphate or silicate both at high (0.41-0.77 ?mol As/g clay), and low (0.04 to 0.05 ?mol As/g clay) As loadings. Phosphate desorbed As to a larger extent than silicate regardless of the amount of As loaded to clay minerals, both in the presence and absence of HA, and both for illite and kaolinite. At high loadings of As, the desorption of both redox species of As from clay-HA complexes by phosphate/silicate ranged from 32 to 72% compared to 2-54% in clay only systems meaning that As was desorbed to a larger extent from HA-coated clays compared to clay only systems. When comparing As(III) desorption by phosphate/silicate to As(V) desorption in high As-loading systems, there was no clear trend for which As species is desorbed to a higher extent in the four clay systems meaning that both As species behave similarly regarding desorption from clay surfaces by phosphate/silicate. Similarly, no significant differences were found in high As-loading systems in the amount of As desorbed by phosphate/silicate when comparing Kao vs. IL and Kao-HA vs IL-HA systems meaning that both clay types behave similarly regarding desorption of As by phosphate/silicate. At low As loadings, up to 80% of As was desorbed by phosphate and silicate with no noticeable differences being observed between different As species, different types of clay, clay vs clay-HA or the type of desorbant (phosphate and silicate). The results of this study showed that HA sorption to Ca 2+-homoionized clay minerals can increase As binding to the clay although the As sorbed to the clay-HA is also released to a greater extent by competing ions such as phosphate and silicate. Desorption of As depended on the initial loadings of As onto the clay/clay-HA. Based on our results, the effect of humic substances on sorption of As and on desorption of As by phosphate and silicate has to be considered in order to fully understand and evaluate the environmental behavior of As in natural environments.

Sharma, Prasesh; Kappler, Andreas

2011-11-01

270

Effects of low-molecular-weight organic ligands and phosphate on adsorption of Pseudomonas putida by clay minerals and iron oxide.  

PubMed

Adsorption of Pseudomonas putida on kaolinite, montmorillonite and goethite was studied in the presence of organic ligands and phosphate. Citrate, tartrate, oxalate and phosphate showed inhibitive effect on P. putida adsorption by three minerals in a broad range of anion concentrations. The highest efficiencies of the four ligands in blocking the adsorption of P. putida on goethite, kaolinite and montmorillonite were 58-90%, 35-76% and 20-48%, respectively. The ability of organic ligands in prohibiting the binding of P. putida cells to the minerals followed the sequence of citrate>tartrate>oxalate>acetate. The significant suppressive effects on P. putida adsorption were ascribed to the increased negative charges by adsorbed ligands and the competition of ligands with bacterial surface groups for binding sites. The inhibitive effects on P. putida adsorption by organic ligands were also dependent on the steric hindrance of the molecules. Acetate presented promotive effect on P. putida adsorption by kaolinite and goethite at low anion concentrations. The results obtained in this study suggested that the adsorption of bacteria in soils especially in the rhizosphere can significantly be impacted by various organic and inorganic anions. PMID:20843669

Wu, Huayong; Jiang, Daihua; Cai, Peng; Rong, Xingmin; Huang, Qiaoyun

2011-01-01

271

Mineral Composition and Abundance of the Rocks and Soils at Gusev and Meridiani from the Mars Exploration Rover Mini-TES Instruments  

NASA Astrophysics Data System (ADS)

The miniature Thermal Emission Spectrometer (Mini-TES) has provided remote measurements of the mineralogy and thermophysical properties of outcrops, rocks, spherules, and soils surrounding the Spirit and Opportunity Rovers [1, 2]. The composition of surface materials provides insight into the origin and evolution of the martian crust and the nature of igneous and sedimentary processes. At Gusev, undisturbed soil spectra closely match MGS TES bright-regions dust spectra, with features interpreted to be due to minor carbonates and bound water. Dark-toned soils observed on rover-disturbed surfaces are likely derived from rocks and have a derived mineralogy, with uncertainties of 5-10 vol.%, of 45% pyroxene (20% high-Ca pyroxene, 25% pigeonite), 40% sodic/intermediate plagioclase, and 15% olivine (Fo35-Fo55). Aeolian drift material has a unique spectral character with higher oxide abundances than disturbed soil. Along the rover's traverse from the lander into the Columbia Hills, at least three distinct rock types have been recognized: olivine rich basalt, a volcaniclastic rock dominated by an amorphous component (possibly basaltic glass and/or shocked plagioclase), and a second volcaniclastic rock dominated by plagioclase of intermediate composition with lesser pyroxene and olivine components. One (or possibly two) spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. At Meridiani, the Mini-TES has identified coarse crystalline hematite and olivine basaltic sands as predicted from orbital TES spectroscopy [3, 4]. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped by TES from orbit. Light-toned outcrops of aqueous origin exposed in crater walls are composed of 20 to 40% Mg and Ca sulfates, a high-silica component that is modeled as glass/feldspar/sheet silicates (~20-30%), and hematite. The Fe-bearing sulfate, jarosite, that was identified by the Mossbauer spectrometer [5], is detected in deconvolutions of several Mini-TES outcrop spectra, but never in concentrations >5%. The dominance of Mg and Ca sulfates in Mini-TES spectra is consistent with the Alpha Particle X-ray Spectrometer (APXS) results, which show that Mg and Ca are present, and that there is significantly more S and too little Fe for the sulfates to be jarosite alone [6]. Two unique surface rocks have been identified during the rover's traverse. Bounce Rock is dominated by clinopyroxene relative to basaltic sands and is closer in inferred mineral composition to the basaltic SNC meteorites. Heat-Shield Rock has a Mini-TES spectral signature that closely resembles a typical spectrum of the sky. The initial Mini-TES interpretation that Heat-Shield Rock was a metallic object with a near reflective surface, and possibly an iron bearing meteorite, was confirmed by APXS and MB observations. The occurrence of waterlain rocks covered by olivine, pyroxene, and feldspar in basaltic sands suggests a significant change from an aqueous environment at the time the rocks were deposited to one dominated by physical weathering. 1)Christensen, P.R., et al., Science, 2004. 305: p. 837-842. 2)Christensen, P.R., et al., Science, 2004. 306: p. 1733-1739. 3)Christensen, P.R., et al., J. Geophys. Res., 2000. 105: p. 9623-9642. 4)Christensen, P.R., et al., J. Geophys. Res., 2001. 106: p. 23873-23885. 5)Klingelhofer, G., et al., Science, 2004. 306: p. 1740-1745. 6)Rieder, R., et al., Science, 2004. 306: p. 1746-1749.

Christensen, P. R.

2005-05-01

272

Thermo Gravimetric and Differential Thermal Analysis of Clay of Western Rajasthan (india)  

NASA Astrophysics Data System (ADS)

The paper presents the study of thermo gravimetric and differential thermal analysis of blended clay. Western part of Rajasthan (India) is rich resource of Ball clays and it is mainly used by porcelain, sanitary ware, and tile industry. The quality and grade of clay available in the region vary from one deposit to other. To upgrade the fired colour and strength properties, different variety of clays may be blended together. The paper compares the results of thermal analysis one of blended clay B2 with reference clay of Ukraine which is imported by industries owners. The result revealed that the blended clay is having mineral kaolinite while the Ukrainian clay is Halloysite.

Shekhawat, M. S.

273

Detailed mineral and chemical relations in two uranium-vanadium ores  

USGS Publications Warehouse

Channel samples from two mines on the Colorado Plateau have been studied in detail both mineralogically and chemically. A channel sample from the Mineral Joe No. 1 mine, Montrose County, Colo., extends from unmineralized rock on one side, through a zone of variable mineralization, into only weakly mineralized rock. The unmineralized rock is a fairly clean quartz sand cemented with gypsum and contains only minor amounts of clay minerals. One boundary between unmineralized and mineralized rock is quite sharo and is nearly at right angles to the bedding. Vanadium clay minerals, chiefly mixed layered mica-montmorillonite and chlorite-monmorillonite, are abundant throughout the mineralized zone. Except in the dark "eye" of the channel sample, the vanadium clay minerals are accompanied by hewettite, carnotite, tyuyamunite, and probably unidentified vanadates. In the dark "eye," paramontroseite, pyrite, and marcasite are abundant, and bordered on each side by a zone containing abundant corvusite. No recognizable uranium minerals were seen in the paramontroseite zone although uranium is abundant there. Coaly material is recognizable throughout all of the channel but is most abundant in and near the dark "eye." Detailed chemical studies show a general increase in Fe, Al, U, and V, and a decrease in SO4 toward the "eye" of the channel. Reducing capacity studies indicate that V(IV) and Fe(II) are present in the clay mineral throughout the channel, but only in and near the "eye" are other V(IV) minerals present (paramontroseite and corvusite). The uranium is sexivalent, although its state of combination is conjectural where it is associated with paramontroseite. Where the ore boundary is sharp, the boundary of introduced trace elements is equally sharp. Textural and chemical relations leave no doubt that the "eye: is a partially oxidized remnant of a former lower-valence ore, and the remainder of the channel is a much more fully oxidized remnant. A channel sample from the Virgin No. 3 mine, Montrose County, Colo., extends from weakly mineralized sandstone on both sides through a strongly mineralized central zone. The weakly mineralized zone is a poorly sorted sandstone with common detrital clay partings; chlorite and mixed layer mica-montmorrillonite are abundant interstitial to the quartz grains. No distinct vanadium or uranium minerals are recognizable, although the clay minerals are vanadium bearing. Euherdral pyrite grains and selenian galena are present but rare. The strongly mineralized rock is separated from the weakly mineralized rock by a narrow transition zone which only apporiximates the bedding planes. It contains abundant vanadium-bearing clay minerals (predominantly chlorite) interstitial to the quartz grains, and apparently replacing them. Paramontroseite is common and is intergrown with the clay minerals. Pyrite and marcasite are present, chiefly in or near the abundant blebs and fragments of carbonaceous material. Selenian galena is rarely present, and generally in or near carbonaceous material. Coffinite is the only uranium mineral idenitified; it is extremely fine grained and was identified only in X-ray diffraction patterns of heavy separates. Distribution of trace elements is not clear; some are consistently high in the strongly mineralized rocks, and some are consistently low. The trace element composition of the unmineralized rock is not known. Chemical studies show a very abrupt rise in the total U, V, and Fe from the weakly mineralized to strongly mineralized rock. Reducing-capacity studies indicate that most of the vanadium is present as V(IV), but some is present as V(V); that iron is present as both Fe(II) and Fe(III), the latter believed to have been present in the primary clays of the unmineralized rock; and that come of the uranium is present as U(VI) in addition to the U(IV) in the coffinite. All evidence points to weak oxidation of an ore once having a somewhat lower valence state. The channel samples from both the Mineral Joe No. 1 mine and the Virgin No. 3 mine are believe to have been essentially

Garrels, Robert M.; Larsen, E. S., III; Pommer, A. M.; Coleman, R. G.

1956-01-01

274

Formation of hydrocarbons from acid-Clay suspensions by gamma irradiation  

SciTech Connect

The adsorption of certain organic compounds by clays gives rise to the transformation of the adsorbate through the action of the clays. This phenomenon can be enhanced using ionizing radiation. In this context, these kinds of reactions play an important role in many natural and industrial processes. For example, in oil and gas exploration, the source and trap of petroleum hydrocarbons is frequently clay-rich rocks. Clay-water-based muds are also seen as environmentally friendly alternatives to toxic oil-based fluids. The principal processes that occur in sediments are usually held to be of bacterial action and thermal transformation, which may include thermally induced catalytic alteration of the organic debris. On the other hand, radioactive materials are widely distributed throughout Earth. They were more abundant in the past, but are present in petroleum reservoirs. Their presence induced radioactive bombardment, which may have altered these sediments. This important subject has not been extensively studied. The aim of this work is to study the behavior of fatty acids-like behenic acid-and dicarboxylic acids-like fumaric acid-as model compounds, which are adsorbed in a clay mineral (Na-montmorillonite) and exposed to gamma radiation. The results show that the radiation-induced decomposition of the clay-acid system goes along a definitive path (oxidation), rather than following several modes of simultaneous decomposition, as happens in radiolysis without clay or by heating the system. The main radiolytic products for fatty acids are their corresponding hydrocarbons, with one C-atom less than the original acid.

Cruz-Castaneda, J.; Negron-Mendoza, A.; Ramos-Bernal, S. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, UNAM. Cd. Universitaria, A. P. 70-543, 04510 Mexico (Mexico)

2013-07-03

275

A granulometry and secondary mineral fingerprint of chemical weathering in periglacial landscapes and its application to blockfield origins  

NASA Astrophysics Data System (ADS)

A review of published literature was undertaken to determine if there was a fingerprint of chemical weathering in regoliths subjected to periglacial conditions during their formation. If present, this fingerprint would be applied to the question of when blockfields in periglacial landscapes were initiated. These blocky diamicts are usually considered to represent remnants of regoliths that were chemically weathered under a warm, Neogene climate and therefore indicate surfaces that have undergone only a few metres to a few 10s of metres of erosion during the Quaternary. Based on a comparison of clay and silt abundances and secondary mineral assemblages from blockfields, other regoliths in periglacial settings, and regoliths from non-periglacial settings, a fingerprint of chemical weathering in periglacial landscapes was identified. A mobile regolith origin under, at least seasonal, periglacial conditions is indicated where clay(%) ? 0.5*silt(%) + 8 across a sample batch. This contrasts with a mobile regolith origin under non-periglacial conditions, which is indicated where clay(%) ? 0.5*silt(%) - 6 across a sample batch with clay(%) ? 0.5*silt(%) + 8 in at least one sample. A range of secondary minerals, which frequently includes interstratified minerals and indicates high local variability in leaching conditions, is also commonly present in regoliths exposed to periglacial conditions during their formation. Clay/silt ratios display a threshold response to temperature, related to the freezing point of water, but there is little response to precipitation or regolith residence time. Lithology controls clay and silt abundances, which increase from felsic, through intermediate, to mafic compositions, but does not control clay/silt ratios. Use of a sedigraph or Coulter Counter to determine regolith granulometry systematically indicates lower clay abundances and intra-site variability than use of a pipette or hydrometer. In contrast to clay/silt ratios, secondary mineral assemblages vary according to regolith residence time, temperature, and/or precipitation. A microsystems model is invoked as a conceptual framework in which to interpret the concurrent formation of the observed secondary mineral ranges. According to the fingerprint of chemical weathering in periglacial landscapes, there is generally no evidence of blockfield origins under warm Neogene climates. Nearly all blockfields appear to be a product of Quaternary physical and chemical weathering. A more dominant role for periglacial processes in further bevelling elevated, low relief, non-glacial surface remnants in otherwise glacially eroded landscapes is therefore indicated.

Goodfellow, Bradley W.

2012-12-01

276

Technical classification of the clay mineralogical composition of paddy soils using multivariate analysis in reference to rice production  

Microsoft Academic Search

Clay mineralogical analysis of paddy soils in Nagasaki Prefecture indicated the presence of smectite, vermiculite, clay mica, chlorite, 2:1 mineral-chlorite intergrade, and kaolin mineral. The application of Q-mode factor analysis to the paddy soils using the contents of 6 minerals in the clay fraction and the clay content of the soil as variables enabled to classify 71 paddy soils into

Kazuhiko Egashira; Koji Osaka; Seishiro Nakashima

1992-01-01

277

Burnt clay magnetic properties and palaeointensity determination  

NASA Astrophysics Data System (ADS)

Burnt clay structures found in situ are the most valuable materials for archaeomagnetic studies. From these materials the full geomagnetic field vector described by inclination, declination and intensity can be retrieved. The reliability of the obtained directional results is related to the precision of samples orientation and the accuracy of characteristic remanence determination. Palaeointensity evaluations depend on much more complex factors - stability of carried remanent magnetization, grain-size distribution of magnetic particles and mineralogical transformations during heating. In the last decades many efforts have been made to shed light over the reasons for the bad success rate of palaeointensity experiments. Nevertheless, sometimes the explanation of the bad archaeointensity results with the magnetic properties of the studied materials is quite unsatisfactory. In order to show how difficult is to apply a priory strict criteria for the suitability of a given collection of archaeomagnetic materials, artificial samples formed from four different baked clays are examined. Two of the examined clay types were taken from clay deposits from different parts of Bulgaria and two clays were taken from ancient archaeological baked clay structures from the Central part of Bulgaria and the Black sea coast, respectively. The samples formed from these clays were repeatedly heated in known magnetic field to 700oC. Different analyses were performed to obtain information about the mineralogical content and magnetic properties of the samples. The obtained results point that all clays reached stable magnetic mineralogy after the repeated heating to 700oC, the main magnetic mineral is of titano/magnetite type and the magnetic particles are predominantly with pseudo single domain grain sizes. In spite that, the magnetic properies of the studied clays seem to be very similar, reliable palaeointensity results were obtained only from the clays coming from clay deposits. The palaeointensity experiments for the samples formed from the ancient baked clays completely failed to give relibable results.

Avramova, Mariya; Lesigyarski, Deyan

2014-05-01

278

Reaction of Sodium Hydroxide with Silicate Minerals.  

National Technical Information Service (NTIS)

The reactions of individual silicate minerals with caustic solution were measured over a 1-week period. These silicate minerals included: two feldspars (microcline and albite), two micas (biotite and muscovite), and three clays (chlorite, Kaolinite and mo...

S. D. Thornton

1986-01-01

279

Alterations in the non-clay-mineral fraction of pelitic rocks the diagenetic to low-grade metamorphic transition, Ouachita Mountains, Oklahoma and Arkansas  

SciTech Connect

The transformation of smectite to illite has been cited by many authors as a source of silica during diagenesis of mudrocks. Illites themselves, however, undergo chemical changes as they recrystallize into micas during high-grade diagenesis/low-grade metamorphism. Average compositions of phyllosilicates from the literature suggest that an equivalent amount of silica is available from transformation of illite to muscovite as from illitization of smectites. The fate of silica released by this process has not been reported, but could be a major contributor to the silt-size quartz population. The quartz and feldspar fraction of pelites from the Stanley Shale (Mississippian) in the Ouachita Mountains of Oklahoma and Arkansas was separated using sodium bisulfate fusions. The mineralogy and the grain-size distribution of this fraction were determined using standard petro-graphic and X-ray diffraction (XRD) techniques. Bulk rock samples were analyzed using X-ray fluorescence (XRF) and instrumental neutron activation analysis (INAA) methods. The data obtained were related to illite crystallinity and vitrinite reflectance as reported by Guthrie el al. (1986) and Houseknecht and Matthews (1985). The authors results are consistent with reported differences between quartz in schists and their shale precursors, and suggest that release of silica during diagenesis of phyllosilicates continues after the smectite-illite transformation. This silica precipitates as quartz within the pelite, consistent with the suggestion by Blatt (1987) that metapelites are the source of abundant silt-size quartz. The lack of whole-rock chemical variation with thermal maturity implies closed-system behavior across much of the pelite-to-metapelite transition.

Totten, M.W.; Blatt, H. (Univ. of Oklahoma, Norman, OK (United States). School of Geology and Geophysics)

1993-09-01

280

Griffith Saponite as an Analog for Clay Minerals at Yellowknife Bay in Gale Crater, Mars: A Marker for Low-temperature Hydrothermal Processes  

NASA Technical Reports Server (NTRS)

The CheMin X-ray diffraction (XRD) instrument onboard the Mars Science Laboratory rover Curiosity in Gale Crater, Mars, discovered smectite in drill fines of the Sheepbed mudstone at Yellowknife Bay (YNB). The mudstone has a basaltic composition, and the XRD powder diffraction pattern shows smectite 02l diffraction bands peaking at 4.59 A for targets John Klein and Cumberland, consistent with tri-octahedral smectites (saponite). From thermal analysis, the saponite abundance is 20 wt. %. Among terrestrial analogues we have studied, ferrian saponite from Griffith Park (Los Angeles, CA) gives the best match to the position of the 02l diffraction band of YNB saponites. Here we describe iron-rich saponites from a terrestrial perspective, with a focus on Griffith saponite, and discuss their implications for the mineralogy of Sheepbed saponite and its formation pathways. Iron-rich saponite: Iron-rich saponite on the Earth is recognized as a low-temperature (<100 C), authigenic alteration product of basalt [e.g., 4-16]. In the discussion that follows, we reference the position of the 02l band because it is a measure of the unit cell 'b' dimension of the octahedral layer and thus the cations (including Fe redox state) in the octahedral layer. Ordinarily, the 06l band near 1.5 A is used to determine the 'b' dimension of smectite, but this band is not accessible with MSL CheMin instrument. For reference, a ferrosaponite (i.e., Fe2+ saponite) studied by [15] has a 02l spacing of 4.72 A and Fe3+/?Fe = 0.27 [15]. Samples of terrestrial ferrosaponite, however, are reported to oxidize on the timescale of days when removed from their natural environment and not protected from oxidation. The Griffith saponite is Mg-rich ferrian saponite, and sample AMNH 89172 has an 02l spacing of 4.59 A (same as the Sheepbed saponites) and Fe3+/?Fe = 0.64 [3]. This similarity suggests that Sheepbed saponites are ferrian (incompletely oxidized ferrosaponite). More oxidized Griffith saponites (Fe3+/?Fe > 0.90) have somewhat smaller 02l d-spacings and also show Mossbauer evidence for an XRD amorphous Fe-bearing phase (e.g., ferrihydrite, hisingerite, superparamagnetic ferric oxides, etc.). The Griffith saponite occurs as vesicle fills, as replacements of olivine, and as replacements of mesostasis (basaltic glass). Similar occurrence modes are reported elsewhere. Hisingerite has been proposed by [13] as the alteration product of ferrian saponite whose precursor by oxidation was ferrosaponite.

Morris, R.V.; Treiman, A. H.; Agresti, D. G.; Graff, T. G.; Achilles, C. N.; Rampe, E. B.; Bristow, T. F.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Bish, D. L.; Chipera, S. J.; Morrison, S. M.; Downs, R. T.

2014-01-01

281

Imprinted Clay Coil Vessels  

ERIC Educational Resources Information Center

The author teaches clay vessel construction in the fifth grade, and it is amazing what can be accomplished in one forty-five minute period when the expectations are clarified in the initial lesson. The author introduces clay coil vessels with a discussion of the sources of clay and how clay relates to fifth-grade science curriculum concepts such…

Lohr, Tresa Rae

2006-01-01

282

An ultrasonic method for isolating nonclay components from clay-rich material  

NASA Astrophysics Data System (ADS)

We present an efficient method for high-volume heavy mineral separation from clay-rich rocks using an ultrasonic probe. The ultrasonic clay separator (UCS) is an easily constructed device that allows for the recovery of high-density minerals, as small as 10 µm, with a minimum of sample preparation. Heavy mineral recovery from clay-rich material with the UCS yields a greater number of small (<100 µm) grains and approximately double the amount of material from that of gravity settling and decanting. Despite development with heavy mineral recovery in mind, the UCS should suitable for recovering small grain size geologic materials from flocculating clay-rich material.

Hoke, Gregory D.; Schmitz, Mark D.; Bowring, Samuel A.

2014-02-01

283

Experimental determination of scattering matrices of randomly oriented fly ash and clay particles at 442 and 633 nm  

Microsoft Academic Search

We present measurements of the scattering angle distribution of the whole scattering matrix for randomly oriented particles of three mineral samples: fly ash, green clay, and red clay at 442 and 633 nm. Fly ash consists of aggregates of nearly spherical particles while green clay and red clay particles represent irregular compact particles. We compare the measured results for fly

O. Muñoz; H. Volten; J. F. de Haan; W. Vassen; J. W. Hovenier

2001-01-01

284

Water Remediation by Adsorption of Phenol onto Hydrophobic Modified Clay  

Microsoft Academic Search

In this work we studied the phenol sorption from contaminated water onto modified clay mineral vermiculite and bentonite by\\u000a insertion of hexadecyltrimethylammonium in the interlayer of clays. The non modified clays showed negligible interaction with\\u000a phenol. The experimental data were treated using the Freunlich equation which had a good fit. The removal percentages were\\u000a higher than 35% for modified vermiculite

Sandro Froehner; Raquel Fernandes Martins; Willian Furukawa; Marcelo Risso Errera

2009-01-01

285

Modelling iron–clay interactions in deep geological disposal conditions  

Microsoft Academic Search

In the context of deep geological disposal of high level radioactive wastes, the interactions between iron and clay-rich materials may lead to adverse transformations of clay minerals with a potential loss of confining properties such as swelling and capacity to exchange cations. Such transformations have been experimentally observed at temperatures starting at ca. 80°C, where smectites contained in a mixture

O. Bildstein; L. Trotignon; M. Perronnet; M. Jullien

2006-01-01

286

Rheology of aging aqueous muscovite clay dispersions  

Microsoft Academic Search

In hydrometallurgical mineral processing, time and pH dependent rheology of dispersions comprising reactive particles can exert a striking influence on material processability and handleability. Rheological studies of 0.32 solid volume fraction (57wt% solid) aqueous dispersions of muscovite clay mineral aging at pH 7 and 1 for 4h were undertaken to investigate the temporal, pulp chemistry-mediated particle interactions. In particular, the

Ataollah Nosrati; Jonas Addai-Mensah; William Skinner

2011-01-01

287

Production Of Liquid Alum Coagulant From Local Saudi Clays  

Microsoft Academic Search

This study was carried out to investigate the use of local clays extremely abundant in the Kingdom for production of liquid alum. Local kaolinitic clay containing 29.4% Al2O3 was ground, activated by calcination and treated with sulfuric acid solution to extract alumina. In the activation step, the effects of grain size of clay, temperature and period of calcination on the

A. AL-ZAHRANI; M. H. ABDEL-MAJID

288

Spectral variability of plagioclase-mafic mixtures (2): Investigation of the optical constant and retrieved mineral abundance dependence on particle size distribution  

NASA Astrophysics Data System (ADS)

Remote sensing data reveal the presence of several igneous-rock forming silicates on the surfaces of various Solar System bodies. Mafic (Mg-Fe silicates) materials were clearly recognized in the past on Mars, Moon, Vesta, and recently the weak absorption of plagioclase has been detected on the lunar highland. The advance in the detection of these important mineral phases encourages the improvement in our capability to quantify the contribution of single end-members in mixed materials.

Carli, C.; Ciarniello, M.; Capaccioni, F.; Serventi, G.; Sgavetti, M.

2014-06-01

289

Three-dimensional complex resistivity analysis for clay characterization in hydrogeologic study  

Microsoft Academic Search

Mapping the distribution, fractional amount and type of clay is important in understanding groundwater flow and contaminant transport. Clay minerals have distinctive surface electrical properties and large surface areas that lead to decreased electrical resistivity in soils containing them and to a distinctive frequency dependent complex resistivity known as induced polarization (IP). IP depends on the clay type, concentration, cation

Jeong-Seok Yang

2002-01-01

290

Chemistry and microstructures of clay particles in smectite-rich shelf sediments, South Shetland Islands, Antarctica  

Microsoft Academic Search

The clay mineralogy of a Holocene sediment core from the shelf of Livingston Island, South Shetland Islands, Antarctica has been investigated by X-ray diffraction (XRD), lattice imaging, bulk chemical analysis of fine clay fractions and analytical transmission electron microscopy (ATEM). The clay minerals identified by XRD of

Gi Young Jeong; Ho Il Yoon; Seung Yeop Lee

2004-01-01

291

Sulphate attack and ettringite formation in the lime and cement stabilized marine clays  

Microsoft Academic Search

Swelling and shrinkage behaviour of marine clays impose foundation problems that may sometimes results in excessive settlements. Improving the behaviour of soft clays using lime or cement is not new. Recent studies reported the occurrence of high swelling and pavement failures in lime and cement stabilized clays containing sulphates. The above phenomena resulted in the formation of swelling minerals such

G. Rajasekaran

2005-01-01

292

Evidence for Smectite Clays from MSL SAM Analyses of Mudstone at Yellowknife Bay, Gale Crater, Mars  

NASA Technical Reports Server (NTRS)

Drilled samples of mudstone from the Sheepbed unit at Yellowknife Bay were analyzed by MSL instruments including the Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments in MSL's Analytical Laboratory. CheMin analyses revealed the first in situ X-ray diffraction based evidence of clay minerals on Mars, which are likely trioctahedral smectites (e.g., saponite) and comprise approx 20% of the mudstone sample (e.g., Bristow et al., this meeting). SAM analyses, which heated the mudstone samples to 1000 C and monitored volatiles evolved to perform in situ evolved gas analysis mass spectrometry (EGA-MS), resulted in a H2O trace exhibiting a wide evolution at temperatures < 500 C, and an evolution peak at higher temperatures near approx 750 C. The low temperature H2O evolution has many potential contributors, including adsorbed H2O, smectite interlayer H2O, and structural H2O/OH from bassanite and akaganeite (identified by CheMin) and H2O/OH from amorphous phases in the sample. The high temperature H2O is consistent with the evolution of H2O from the dehydroxylation of the smectite clay mineral. Comparison to EGA-MS data collected under SAM-like conditions on a variety of clay mineral reference materials indicate that a trioctahedral smectite, such as saponite, is most consistent with the high temperature H2O evolution observed. There may also be SAM EGA-MS evidence for a small high temperature H2O evolution from scoop samples from the Yellowknife Bay Rocknest sand shadow bedform. As in the mudstone samples, this evolution may indicate the detection of smectite clays, and the idea that minor clays may be present in Rocknest materials that could be expected to be at least partially derived from local sources is reasonable. But, because smectite clays were not definitively observed in CheMin analyses of Rocknest materials, they must be present at much lower abundances than the approx 20% observed in the mudstone samples. This potential detection underscores the complementary nature of the MSL CheMin and SAM instruments for investigations of martian sample mineralogy. Information on the nature of Yellowknife Bay clay minerals may also be available from the detection of H2 evolved during SAM EGA-MS at high temperature. A likely source of at least some of this H2 is H2O evolved from the smectite clays at high temperature, and it is possible these evolutions can be used in a similar fashion to high temperature H2O releases to provide constraints on the clay minerals in a sample. In addition, the D/H of this high temperature H2, as well as the H2O, can be derived from SAM MS and Tunable Laser Spectrometer (TLS) data, respectively. These D/H values may help to inform the provenance of high and low temperature water evolved from martian samples

McAdam, Amy; Franz, Heather; Mahaffy, Paul R.; Eigenbrode, Jennifer L.; Stern, Jennifer C.; Brunner, Anna; Archer, Paul Douglas; Ming, Douglas W.; Morris, Richard V.; Atreya, Sushil K.

2013-01-01

293

Evidence for Smectite Clays from MSL SAM Analyses of Mudstone at Yellowknife Bay, Gale Crater, Mars  

NASA Astrophysics Data System (ADS)

Drilled samples of mudstone from the Sheepbed unit at Yellowknife Bay were analyzed by MSL instruments including the Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments in MSL's Analytical Laboratory. CheMin analyses revealed the first in situ X-ray diffraction based evidence of clay minerals on Mars, which are likely trioctahedral smectites (e.g., saponite) and comprise ~20% of the mudstone sample (e.g., Bristow et al., this meeting). SAM analyses, which heated the mudstone samples to 1000oC and monitored volatiles evolved to perform in situ evolved gas analysis mass spectrometry (EGA-MS), resulted in a H2O trace exhibiting a wide evolution at temperatures <500oC, and an evolution peak at higher temperatures near ~750oC. The low temperature H2O evolution has many potential contributors, including adsorbed H2O, smectite interlayer H2O, and structural H2O/OH from bassanite and akaganeite (identified by CheMin) and H2O/OH from amorphous phases in the sample. The high temperature H2O is consistent with the evolution of H2O from the dehydroxylation of the smectite clay mineral. Comparison to EGA-MS data collected under SAM-like conditions on a variety of clay mineral reference materials indicate that a trioctahedral smectite, such as saponite, is most consistent with the high temperature H2O evolution observed. There may also be SAM EGA-MS evidence for a small high temperature H2O evolution from scoop samples from the Yellowknife Bay Rocknest sand shadow bedform. As in the mudstone samples, this evolution may indicate the detection of smectite clays, and the idea that minor clays may be present in Rocknest materials that could be expected to be at least partially derived from local sources is reasonable. But, because smectite clays were not definitively observed in CheMin analyses of Rocknest materials, they must be present at much lower abundances than the ~20% observed in the mudstone samples. This potential detection underscores the complementary nature of the MSL CheMin and SAM instruments for investigations of martian sample mineralogy. Information on the nature of Yellowknife Bay clay minerals may also be available from the detection of H2 evolved during SAM EGA-MS at high temperature. A likely source of at least some of this H2 is H2O evolved from the smectite clays at high temperature, and it is possible these evolutions can be used in a similar fashion to high temperature H2O releases to provide constraints on the clay minerals in a sample. In addition, the D/H of this high temperature H2, as well as the H2O, can be derived from SAM MS and Tunable Laser Spectrometer (TLS) data, respectively. These D/H values may help to inform the provenance of high and low temperature water evolved from martian samples (Mahaffy et al., this meeting).

McAdam, A.; Franz, H.; Mahaffy, P. R.; Eigenbrode, J. L.; Stern, J. C.; Brunner, A.; Sutter, B.; Archer, P. D.; Ming, D. W.; Morris, R. V.; Atreya, S. K.; Team, M.

2013-12-01

294

TNT adsoprtion on clay minerals by HPLC  

Microsoft Academic Search

Several military bases and monitions facilities throughout the world are contaminated with toxic explosives like 2,4,6-trinitrotoluene (TNT). This is an energetic compound and the least mobile of the military explosives. For this reason TNT gives one of the largest soil contamination problems. To understand the adsorption mechanism between TNT explosive and soil environments, the mechanical method analysis is used in

Rosángela Rivera; Liliana F. Alzate; Miguel A. Muñoz; Nairmen Mina

2006-01-01

295

Prolonged triboluminescence in clays and other minerals  

NASA Technical Reports Server (NTRS)

The decay curves of various triboluminescent-excited materials were obtained, including well-crystallized and poorly crystallized kaolin, bentonite, quartz, sodium chloride, and chalk calcite. A qualitative increase in triboluminescence was observed for kaolin dipped in water or tryptophan solution compared to dry kaolin, and for frozen kaolin and montmorillonite pastes. Theoretical explanations for the tryptophan effect are discussed.

Lahav, N.; Coyne, L. M.; Lawless, J. G.

1982-01-01

296

Mass removal and clay mineral dehydration/rehydration in carbonate-rich surface exposures of the 2008 Wenchuan Earthquake fault: Geochemical evidence and implications for fault zone evolution and coseismic slip  

NASA Astrophysics Data System (ADS)

We report variations in the mineralogical, geochemical, and isotopic (?13C, ?18O) composition of fault rocks sampled in transects across the Zhaojiagou and Pingxi exposures of the Wenchuan Earthquake or Longmenshan Fault Zone, where the gouge-rich fault core and principal slip surface cuts through carbonate-rich strata. Pervasive fluid infiltration was found to modify the mineralogical and geochemical architecture of the fault zones studied. Enrichment/depletion patterns, element partitioning, and a very large implied volume loss are quite different from those characterizing faults in granites and clastic sedimentary rocks and can be explained by a mass removal model involving dissolution and advective transport enhanced by pressure solution. An increasing enrichment in smectite observed toward the principal slip surface, a high abundance of elements such as Ba, Mg, and F, the deposition of minerals such as barite and fluorapatite, as well as the distinct depletion in 13C in vein material consistently suggest reactions involving a hydrothermal fluid originating at depth. Illitization of black gouges, caused by coseismic frictional heating, was found to be widespread. We propose that coseismic frictional heating along with the action of postseismic hydrothermal fluids controlled the transformation and distribution of smectite and illite within the fault core of the Longmenshan Fault Zone. The coseismic dewatering reactions are expected to have been more extensive at depth, possibly helping generate excess pore pressure assisting dynamic slip weakening during the Wenchuan Earthquake.

Chen, Jianye; Yang, Xiaosong; Ma, Shengli; Spiers, Christopher J.

2013-02-01

297

Remediation of contaminated soils and water with organic chemicals by means of natural, anionic and organic clays  

Microsoft Academic Search

Clays and “anionic clays” are layered natural and synthetic compounds, respectively, with very special surface properties.\\u000a Clay minerals are composed of negatively charged aluminosilicate layers whose surface charge is balance by hydrated inorganic\\u000a cations located in the interlayer space. Smectites are a clay mineral group having swelling or expandable structure which\\u000a makes the interlamellar space accessible for cationic or polar

Juan Cornejo; Rafael Celis

298

Herbivore trampling as an alternative pathway for explaining differences in nitrogen mineralization in moist grasslands.  

PubMed

Studies addressing the role of large herbivores on nitrogen cycling in grasslands have suggested that the direction of effects depends on soil fertility. Via selection for high quality plant species and input of dung and urine, large herbivores have been shown to speed up nitrogen cycling in fertile grassland soils while slowing down nitrogen cycling in unfertile soils. However, recent studies show that large herbivores can reduce nitrogen mineralization in some temperate fertile soils, but not in others. To explain this, we hypothesize that large herbivores can reduce nitrogen mineralization in loamy or clay soils through soil compaction, but not in sandy soils. Especially under wet conditions, strong compaction in clay soils can lead to periods of soil anoxia, which reduces decomposition of soil organic matter and, hence, N mineralization. In this study, we use a long-term (37-year) field experiment on a salt marsh to investigate the hypothesis that the effect of large herbivores on nitrogen mineralization depends on soil texture. Our results confirm that the presence of large herbivores decreased nitrogen mineralization rate in a clay soil, but not in a sandy soil. By comparing a hand-mown treatment with a herbivore-grazed treatment, we show that these differences can be attributed to herbivore-induced changes in soil physical properties rather than to above-ground biomass removal. On clay soil, we find that large herbivores increase the soil water-filled porosity, induce more negative soil redox potentials, reduce soil macrofauna abundance, and reduce decomposition activity. On sandy soil, we observe no changes in these variables in response to grazing. We conclude that effects of large herbivores on nitrogen mineralization cannot be understood without taking soil texture, soil moisture, and feedbacks through soil macrofauna into account. PMID:23271034

Schrama, Maarten; Heijning, Pieter; Bakker, Jan P; van Wijnen, Harm J; Berg, Matty P; Olff, Han

2013-05-01

299

Nanoporous polymer--clay hybrid membranes for gas separation.  

PubMed

Nanohybrid organo-inorgano clay mineral-polydimethylsiloxane (PDMS) membranes were prepared by the reaction of pure and/or modified natural clay minerals (Sepiolite and montmorillonite) with PDMS in hexane, followed by evaporation of the solvent at 70 degrees C. The membranes were characterized by means of XRD, SEM, ATD-TG and solid state (29)Si magic angle spinning (MAS) and cross-polarization (CP) CP/MAS NMR. The morphology of the membranes depends on the content loading of clay mineral. For low content, the membrane composition is homogeneous, with well dispersed nanoparticles of clay into the polymer matrix, whereas for higher clay content, the membranes are constituted also of a mixture of well dispersed nanoparticles into the polymer, but in the presence of agglomerations of small clay particles. Quantitative (29)Si MAS NMR demonstrated a strong correlation between the clay content of the membrane and the average length of the PDMS chain, indicating that the nanohybrid material is made of clay particles covalently linked to the PDMS structure. This is particularly the case for Sepiolite with has a high density of Q(2) silanol sites. The separation performances of the prepared membranes were tested for CO(2)/CH(4) and O(2)/N(2) mixtures. The observed separation factors showed an increase of the selectivity in the case of CO(2)/CH(4) in comparison with membranes made from PDMS alone under the same conditions. PMID:20060540

Defontaine, Guillaume; Barichard, Anne; Letaief, Sadok; Feng, Chaoyang; Matsuura, Takeshi; Detellier, Christian

2010-03-15

300

The distribution of secondary mineral phases along an eroding hillslope and its effect on carbon stabilization mechanisms and the fate of soil carbon fractions  

NASA Astrophysics Data System (ADS)

Soil redistribution processes can change soil carbon (C) dynamics drastically by moving carbon from high decomposition and re-sequestration environments at the eroding hillslope to low decomposition and burial at the depositional footslope and valley basin. This leads to not only spatially diverse soil carbon storage throughout the landscape, but also to qualitative changes of the transported carbon and the mineral phase. The interaction between those parameters and the effect on stabilization mechanisms for soil C are still a matter of debate. Here, we present an analysis that aims to clarify the bio/geo-chemical and mineralogical components involved in stabilizing C at various depths along an eroding cropped slope and how this affects the abundance of microbial derived carbon. We use the results of an incubation experiment combined with the abundance of amino sugars in different isolated soil C fractions as a tracer for the stability of the respective fraction. We applied further (i) a sequential extraction of the reactive soil phase using pyrophosphate, oxalate and dithionite-citrate-bicarbonate, and (ii) a qualitative analysis of the clay mineralogy, to analyze the changes in the mineral phase for the different isolated fractions along the slope transect. Our results emphasize the importance of physical protection within microaggregates to stabilize buried, chemically labile C. Our data further indicates that the stability of these aggregates is related to the presence of organo-mineral associations and poorly crystalline minerals. However, decreasing contents of these minerals with depth indicate a temporal limitation of this stabilization mechanism. Non-expandable clay minerals experience a relative enrichment at the depositional site while expandable clay minerals experience the same at the eroding site. These changes in clay mineralogy along the slope are partly responsible for the abundance of silt and clay associated C and the effectiveness of the clay fractions to stabilize C. In summary, our data clearly show that a variety of stabilization mechanisms together with changes in the organic and the mineral phase of soils need to be considered to understand this highly dynamic environment.

Doetterl, Sebastian; Cornelis, Jean-Thomas; Opfergelt, Sophie; Boeckx, Pascal; Bodé, Samuel; Six, Johan; Van Oost, Kristof

2014-05-01

301

Mineral Commodities  

NSDL National Science Digital Library

This exercise introduces mineral commodities (elements). Students consider the elements aluminum, iron, copper, nickel, zinc, uranium, lead, gold, mercury and tin and match them with their definintions in a table. Then they use minable grade (minable weight percent) and normal crustal abundance (crustal weight percent) to calculate the concentration factor for several commodities to determine their economic minability. Students then graph their calculations and explain their trend.

Perkins, Dexter

302

Influence of Potential Determining Ions on the Microstructural Performance and Contaminant Adsorption of a Homoionic Illitic Clay  

Microsoft Academic Search

Contaminant adsorption properties of clays are markedly influenced by the type of clay minerals, the nature of the exchangeable\\u000a ions, and the type of clay microstructure present. Clay soils, due to their high buffering capacity and low permeability,\\u000a are very helpful materials as barriers in waste disposal projects. On the other hand, the different microstructures of clay\\u000a soils, due to

V. R. Ouhadi; R. N. Yong; H. Bayesteh; A. R. Goodarzi

2007-01-01

303

Comparison of abundances of chemical elements in mineralized and unmineralized sandstone of the Brushy Basin Member of the Morrison Formation, Smith Lake District, Grants uranium region, New Mexico  

USGS Publications Warehouse

Statistical treatment of analytical data from the Mariano Lake and Ruby uranium deposits in the Smith Lake district, New Mexico, indicates that organic carbon, arsenic, barium, calcium, cobalt, copper, gallium, iron, lead, manganese, molybdenum, nickel, selenium, strontium, sulfur, vanadium, yttrium, and zirconium are concentrated along with uranium in primary ore. Comparison of the Smith Lake data with information from other primary deposits in the Grants uranium region and elsewhere in the Morrison Formation of the Colorado Plateau suggests that these elements, with the possible exceptions of zirconium and gallium and with the probable addition of aluminum and magnesium, are typically associated with primary, tabular uranium deposits. Chemical differences between the Ruby and Mariano Lake deposits are consistent with the interpretation that the Ruby deposit has been more affected by post-mineralization oxidizing solutions than has the Mariano Lake deposit.

Pierson, C. T.; Spirakis, C. S.; Robertson, J. F.

1983-01-01

304

Minerals Yearbook 1990: Montana.  

National Technical Information Service (NTIS)

Montana's 1990 nonfuel mineral production value was $567.7 million, relatively unchanged from that of 1989. Gains in the production value of portland cement, clays, gold, crushed stone, talc, and zinc offset the decline in values of copper, molybdenum, ph...

R. J. Minarik R. B. McCulloch

1992-01-01

305

Soil clay content underlies prion infection odds  

USGS Publications Warehouse

Environmental factors-especially soil properties-have been suggested as potentially important in the transmission of infectious prion diseases. Because binding to montmorillonite (an aluminosilicate clay mineral) or clay-enriched soils had been shown to enhance experimental prion transmissibility, we hypothesized that prion transmission among mule deer might also be enhanced in ranges with relatively high soil clay content. In this study, we report apparent influences of soil clay content on the odds of prion infection in free-ranging deer. Analysis of data from prion-infected deer herds in northern Colorado, USA, revealed that a 1% increase in the clay-sized particle content in soils within the approximate home range of an individual deer increased its odds of infection by up to 8.9%. Our findings suggest that soil clay content and related environmental properties deserve greater attention in assessing risks of prion disease outbreaks and prospects for their control in both natural and production settings. ?? 2011 Macmillan Publishers Limited. All rights reserved.

David, Walter, W.; Walsh, D. P.; Farnsworth, M. L.; Winkelman, D. L.; Miller, M. W.

2011-01-01

306

What makes a natural clay antibacterial?  

PubMed

Natural clays have been used in ancient and modern medicine, but the mechanism(s) that make certain clays lethal against bacterial pathogens has not been identified. We have compared the depositional environments, mineralogies, and chemistries of clays that exhibit antibacterial effects on a broad spectrum of human pathogens including antibiotic resistant strains. Natural antibacterial clays contain nanoscale (<200 nm), illite-smectite and reduced iron phases. The role of clay minerals in the bactericidal process is to buffer the aqueous pH and oxidation state to conditions that promote Fe(2+) solubility. Chemical analyses of E. coli killed by aqueous leachates of an antibacterial clay show that intracellular concentrations of Fe and P are elevated relative to controls. Phosphorus uptake by the cells supports a regulatory role of polyphosphate or phospholipids in controlling Fe(2+). Fenton reaction products can degrade critical cell components, but we deduce that extracellular processes do not cause cell death. Rather, Fe(2+) overwhelms outer membrane regulatory proteins and is oxidized when it enters the cell, precipitating Fe(3+) and producing lethal hydroxyl radicals. PMID:21413758

Williams, Lynda B; Metge, David W; Eberl, Dennis D; Harvey, Ronald W; Turner, Amanda G; Prapaipong, Panjai; Poret-Peterson, Amisha T

2011-04-15

307

What Makes a Natural Clay Antibacterial?  

PubMed Central

Natural clays have been used in ancient and modern medicine, but the mechanism(s) that make certain clays lethal against bacterial pathogens has not been identified. We have compared the depositional environments, mineralogies, and chemistries of clays that exhibit antibacterial effects on a broad spectrum of human pathogens including antibiotic resistant strains. Natural antibacterial clays contain nanoscale (<200 nm), illite-smectite and reduced iron phases. The role of clay minerals in the bactericidal process is to buffer the aqueous pH and oxidation state to conditions that promote Fe2+ solubility. Chemical analyses of E. coli killed by aqueous leachates of an antibacterial clay show that intracellular concentrations of Fe and P are elevated relative to controls. Phosphorus uptake by the cells supports a regulatory role of polyphosphate or phospholipids in controlling Fe2+. Fenton reaction products can degrade critical cell components, but we deduce that extracellular processes do not cause cell death. Rather, Fe2+ overwhelms outer membrane regulatory proteins and is oxidized when it enters the cell, precipitating Fe3+ and producing lethal hydroxyl radicals.

Williams, Lynda B.; Metge, David W.; Eberl, Dennis D.; Harvey, Ronald W.; Turner, Amanda G.; Prapaipong, Panjai; Poret-Peterson, Amisha T.

2011-01-01

308

Soil clay content underlies prion infection odds.  

PubMed

Environmental factors-especially soil properties-have been suggested as potentially important in the transmission of infectious prion diseases. Because binding to montmorillonite (an aluminosilicate clay mineral) or clay-enriched soils had been shown to enhance experimental prion transmissibility, we hypothesized that prion transmission among mule deer might also be enhanced in ranges with relatively high soil clay content. In this study, we report apparent influences of soil clay content on the odds of prion infection in free-ranging deer. Analysis of data from prion-infected deer herds in northern Colorado, USA, revealed that a 1% increase in the clay-sized particle content in soils within the approximate home range of an individual deer increased its odds of infection by up to 8.9%. Our findings suggest that soil clay content and related environmental properties deserve greater attention in assessing risks of prion disease outbreaks and prospects for their control in both natural and production settings. PMID:21326232

David Walter, W; Walsh, Daniel P; Farnsworth, Matthew L; Winkelman, Dana L; Miller, Michael W

2011-01-01

309

Deuterium abundances  

NASA Astrophysics Data System (ADS)

We discuss the measurements of deuterium abundances in high redshift quasar absorbers, in the solar system and in the interstellar medium. We present new results that indicate spatial variations of the deuterium abundance in the interstellar medium at the level of ˜50% over scales possibly as small as ˜10 pc, and discuss plausible causes for the origin of these variations.

Lemoine, Martin; Audouze, Jean; Ben Jaffel, Lotfi; Feldman, Paul; Ferlet, Roger; Hébrard, Guillaume; Jenkins, Edward B.; Mallouris, Christoforos; Moos, Warren; Sembach, Kenneth; Sonneborn, George; Vidal-Madjar, Alfred; York, Donald G.

1999-07-01

310

Yangtze River sediments from source to sink traced with clay mineralogy  

NASA Astrophysics Data System (ADS)

River bed sediments were collected from the main stream and major tributaries of the Yangtze River for clay mineralogy study. Surface sediments from the Yarlung Zangbo River on the Tibetan Plateau were also examined for comparison. The results show that the clay mineral compositions of the Yangtze River display a similar pattern through the whole truck stream, with illite being dominant, kaolinite and chlorite being lesser abundant, and smectite being minor component. Clay mineralogy shows distinct differences in the tributaries, which correspond to the heterogeneous source rocks and weathering intensity of the drainage. The illite crystallity and the illite chemical weathering index (5 Å/10 Å peak ratio) both increase downstream, indicating a increasing trend of hydrolysis along the river. It also indicates that the upperstream of the drainage is characterized with physical weathering while the middle- and lower reaches are controlled by chemical weathering process. In accordance with the result derived by the illite indexes, sediment input from upperstream including Yalong Jiang, Dadu He, Min Jiang and Jialing Jiang accounts for the major sediment load, whereas Wu Jiang, Xiang Jiang, Gan Jiang and Dongting Lake provide relatively less sediments.

He, Mengying; Zheng, Hongbo; Huang, Xiangtong; Jia, Juntao; Li, Ling

2013-06-01

311

Rocks and Minerals  

NSDL National Science Digital Library

This unit provides younger students with an introduction to rocks and minerals. Topics include the definition of a mineral, the physical properties of minerals and how they are measured, and a discussion of quartz, the most basic silicate mineral and one of the most abundant minerals in the Earth's crust. The discussion on rocks includes the rock cycle, the three rock types (igneous, sedimentary, metamorphic), and how they are formed. There is also a vocabulary list and downloadable, printable worksheets for each major topic.

Medina, Philip

2010-09-08

312

Flow of clays  

NASA Astrophysics Data System (ADS)

Recent experimental and theoretical research into physical phenomena in clays is reviewed. Clays' present place in the context of modern materials science is briefly discussed, and illustrated through the rich behavior recently displayed in this physical model system. We will show that in order to understand macroscopic flow behaviors in these systems, it is crucial to know the underlying nanostructures in detail. With the clay nanostructural basis at hand, we will review recent advances in clay systems from the geological example of quick clay flows and avalanches, to materials science and the stability, strength and flow of smart electrorheological clay structures. In the case of natural quick clay, there is now hope of establishing a protocol for avalanche preditction based on rheological sample data. In materials science, the use of electric fields together with flow in order to improve the processing of clay composite materials may open new unexplored avenues. We will finally discuss that due to the interplay of van der Waals and electrostatic forces screened by ions at the nanoscale, clays may either form a glass, or a gel and thus give fundamental insights into the elusive questions related to materials universal aging flow dynamics.

Fossum, J. O.

2012-04-01

313

The influence of authigenic clay formation on the mineralogy and stable isotopic record of lacustrine carbonates  

NASA Astrophysics Data System (ADS)

The mineralogical, compositional and stable isotopic variability of lacustrine carbonates are frequently used as proxies for ancient paleoenvironmental change in continental settings, under the assumption that precipitated carbonates reflect conditions and chemistry of ancient lake waters. In some saline and alkaline lake systems, however, authigenic clay minerals, forming at or near the sediment water interface, are a major sedimentary component. Often these clays are rich in Mg, influencing the geochemical budget of lake waters, and are therefore expected to influence the properties of contemporaneous authigenic carbonate precipitates (which may also contain Mg). This paper documents evidence for a systematic feedback between clay mineral and carbonate authigenesis through multiple precessionally driven, m-scale sedimentary cycles in lacustrine oil-shale deposits of the Eocene Green River Formation from the Uinta Basin (NE Utah). In the studied section, authigenic, Mg-rich, trioctahedral smectite content varies cyclically between 9 and 39 wt.%. The highest concentrations occur in oil-shales and calcareous mudstones deposited during high lake level intervals that favored sedimentary condensation, lengthening the time available for clay diagenesis and reducing dilution by other siliciclastic phases. An inverse relation between dolomite percentage of carbonate and trioctahedral smectite abundance suggests the Mg uptake during clay authigenesis provides a first order control on carbonate mineralogy that better explains carbonate mineralogical trends than the possible alternative controls of (1) variable Mg/Ca ratios in lake water and (2) degree of microbial activity in sediments. We also observe that cyclical change in carbonate mineralogy, believed to be induced by clay authigenesis, also causes isotopic covariation between ?13CPDB and ?18OPDB of bulk sediments because of differences in the equilibrium fractionation factors of dolomite and calcite (˜2‰ and ˜2.6%, respectively). This provides an alternative mechanism for the common pattern of isotopic covariation, which is typically attributed to the effect of simultaneous changes in water balance and biological activity on the carbon and oxygen isotopic composition of lake waters. These findings may help improve paleoenvironmental reconstructions based on lacustrine carbonate records by adding to the factors known to influence the mineralogical, compositional and stable isotopic signals recorded by lacustrine carbonates.

Bristow, Thomas F.; Kennedy, Martin J.; Morrison, Keith D.; Mrofka, David D.

2012-08-01

314

Application of Hyperspectral Methods in Hydrothermal Mineral System Studies  

NASA Astrophysics Data System (ADS)

Hyperspectral infrared reflectance spectra are used to identify abundances and compositional differences of mineral groups and single mineral phases. 3D mineral maps are derived from surface (airborne and satellite sensed) and sub-surface (drill core) mineralogical data and integrated with geological, geochemical and geophysical datasets, enabling a quantitative mineral systems analysis. The Western Australian Centre of Excellence for 3D Mineral Mapping is working on a variety of mineral deposits to showcase the emerging applications of hyperspectral techniques in mineral system studies. Applied remote sensing technologies comprise hyperspectral airborne surveys (HyMap) covering 126 bands in the visible and shortwave infrared, as well as satellite-based multispectral surveys (ASTER) featuring 14 bands from the visible to thermal infrared. Drill cores were scanned with CSIRO's HyLoggingTM systems, which allow a fast acquisition of mineralogical data in cm-spacing and thereby providing statistically significant datasets. Building on procedures developed for public Australian geosurvey data releases for north Queensland, Broken Hill and Kalgoorlie (http://c3dmm.csiro.au), the ultimate goal is to develop sensor-independent scalars based on the position, depth and shape of selected absorption features in the visible-near (VNIR), shortwave (SWIR) and thermal infrared (TIR), which can be applied to a wide range of mineral deposit types. In the Rocklea Dome Channel Iron Ore deposits of the Pilbara (Western Australia) for example, hyperspectral drill core data were processed into 3D mineral maps to delineate major ore zones by identifying various ore types and possible contaminants. Vitreous (silica-rich) iron ore was successfully separated from ochreous goethitic ore, with both of them requiring different metallurgical processing. The silicified vitreous iron ore as well as outlined carbonate-rich zones are presumably related to overprinting groundwater effects. The hyperspectral mineral mapping of contaminating, carbonate- or clay-rich zones helped to better constrain the ore zones and the genesis of the mineral system. Airborne hyperspectral data covering about 2500 km2 were obtained from the Eastern Goldfields Superterrane (Yilgarn Craton, Western Australia), which is highly prospective for Archean Au as well as komatiite associated Fe-Ni sulphide mineralisation. In this project hyperspectral airborne data allowed not only the remote mapping of mafic and ultramafic rocks, which are among the main host rocks for Archean Au deposits in the study area, but also the remote mapping of hydrothermal alteration patterns and various geochemical signatures related to the structurally controlled Au mineralisation down to a 4.5 m pixel size. We can reconstruct fluid pathways and their intersections with steep physicochemical gradients, where Au deposition presumably took place, by combining hyperspectral remote sensing with hyperspectral drill core data in 3D mineral maps. White mica mineral maps as well as mineral maps based on the abundance and composition of MgOH and FeOH bearing silicates are the main products for a semi-quantitative assessment of the key alteration minerals in this project. In the southern Selwyn Range, Mount Isa Inlier, Queensland, hyperspectral mineral maps, such as "ferric oxide abundance", "white mica abundance" and "white mica composition", were integrated with geophysical datasets (total magnetic intensity, ternary radiometric imagery). The integration of the datasets enabled us to construct a comprehensive fluid flow model contributing to our understanding of iron-oxide Cu-Au deposits in this region, identifying the source, pathway and depositional sites, which are in good accordance with known deposits. 3D mineral maps derived from hyperspectral methods can distinctly improve our understanding of mineral systems. The advantages of hyperspectral techniques over conventional exploration methods include: (1) the fast and cost efficient acquisition of both surface and sub-surface mi

Laukamp, Carsten; Cudahy, Thomas; Gessner, Klaus; Haest, Maarten; Cacetta, Mike; Rodger, Andrew; Jones, Mal; Thomas, Matilda

2010-05-01

315

Finicky clay divers  

Microsoft Academic Search

Clay spheres dropped into a dilute vinegar\\/baking-soda solution accumulate CO2 bubbles on their surfaces. Spheres below a certain size will then float, otherwise they remain sunken. Students must determine the maximum size that will float by considering the net density of the clay\\/bubble system.

Sean M. Cordry

1998-01-01

316

Finicky clay divers  

NASA Astrophysics Data System (ADS)

Clay spheres dropped into a dilute vinegar/baking-soda solution accumulate CO2 bubbles on their surfaces. Spheres below a certain size will then float, otherwise they remain sunken. Students must determine the maximum size that will float by considering the net density of the clay/bubble system.

Cordry, Sean M.

1998-02-01

317

The rheology of clay  

Microsoft Academic Search

The rheology of clay-water mixtures, both liquid and solid, is critically reviewed. Certain discrepancies between different experimental and mathematical treatments of the liquid suspensions are pointed out. The probable structure of the solid mixtures and their exceptional properties are discussed and it is shown how these properties may be explained by the supposition that the surfaces of the clay particles

H. H. Macey

1941-01-01

318

External Resource: Clay Planets  

NSDL National Science Digital Library

In this activity, learners/students use given amounts of clay to create models of the solar system. Learners/students use clay to represent different planets and other objects in the solar system (asteroids, moons, etc.). The learners/students can use as

1900-01-01

319

Columns in Clay  

ERIC Educational Resources Information Center

This article describes a clay project for students studying Greece and Rome. It provides a wonderful way to learn slab construction techniques by making small clay column capitols. With this lesson, students learn architectural vocabulary and history, understand the importance of classical architectural forms and their influence on today's…

Leenhouts, Robin

2010-01-01

320

The Swelling of Clay  

ERIC Educational Resources Information Center

Describes the macroscopic process of the swelling of clay by adding water, and the corresponding microscopic process of water molecules entering the spacings between clay crystals. Discusses how the Bragg equation can be used together with other physical data to calculate these spacings. (MLH)

Adams, J. M.

1975-01-01

321

The role of reaction affinity and secondary minerals in regulating chemical weathering rates at the Santa Cruz Soil Chronosequence, California  

NASA Astrophysics Data System (ADS)

In order to explore the reasons for the apparent discrepancy between laboratory and field weathering rates and to determine the extent to which weathering rates are controlled by the approach to thermodynamic equilibrium, secondary mineral precipitation, and flow rates, a multicomponent reactive transport model (CrunchFlow) was used to interpret soil profile development and mineral precipitation and dissolution rates at the 226 ka Marine Terrace Chronosequence near Santa Cruz, CA. Aqueous compositions, fluid chemistry, transport, and mineral abundances are well characterized [White A. F., Schulz M. S., Vivit D. V., Blum A., Stonestrom D. A. and Anderson S. P. (2008) Chemical weathering of a Marine Terrace Chronosequence, Santa Cruz, California. I: interpreting the long-term controls on chemical weathering based on spatial and temporal element and mineral distributions. Geochim. Cosmochim. Acta72 (1), 36-68] and were used to constrain the reaction rates for the weathering and precipitating minerals in the reactive transport modeling. When primary mineral weathering rates are calculated with either of two experimentally determined rate constants, the nonlinear, parallel rate law formulation of Hellmann and Tisserand [Hellmann R. and Tisserand D. (2006) Dissolution kinetics as a function of the Gibbs free energy of reaction: An experimental study based on albite feldspar. Geochim. Cosmochim. Acta70 (2), 364-383] or the aluminum inhibition model proposed by Oelkers et al. [Oelkers E. H., Schott J. and Devidal J. L. (1994) The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions. Geochim. Cosmochim. Acta58 (9), 2011-2024], modeling results are consistent with field-scale observations when independently constrained clay precipitation rates are accounted for. Experimental and field rates, therefore, can be reconciled at the Santa Cruz site. Additionally, observed maximum clay abundances in the argillic horizons occur at the depth and time where the reaction fronts of the primary minerals overlap. The modeling indicates that the argillic horizon at Santa Cruz can be explained almost entirely by weathering of primary minerals and in situ clay precipitation accompanied by undersaturation of kaolinite at the top of the profile. The rate constant for kaolinite precipitation was also determined based on model simulations of mineral abundances and dissolved Al, SiO 2(aq) and pH in pore waters. Changes in the rate of kaolinite precipitation or the flow rate do not affect the gradient of the primary mineral weathering profiles, but instead control the rate of propagation of the primary mineral weathering fronts and thus total mass removed from the weathering profile. Our analysis suggests that secondary clay precipitation is as important as aqueous transport in governing the amount of dissolution that occurs within a profile because clay minerals exert a strong control over the reaction affinity of the dissolving primary minerals. The modeling also indicates that the weathering advance rate and the total mass of mineral dissolved is controlled by the thermodynamic saturation of the primary dissolving phases plagioclase and K-feldspar, as is evident from the difference in propagation rates of the reaction fronts for the two minerals despite their very similar kinetic rate laws.

Maher, Kate; Steefel, Carl I.; White, Art F.; Stonestrom, Dave A.

2009-05-01

322

The role of reaction affinity and secondary minerals in regulating chemical weathering rates at the Santa Cruz Soil Chronosequence, California  

USGS Publications Warehouse

In order to explore the reasons for the apparent discrepancy between laboratory and field weathering rates and to determine the extent to which weathering rates are controlled by the approach to thermodynamic equilibrium, secondary mineral precipitation, and flow rates, a multicomponent reactive transport model (CrunchFlow) was used to interpret soil profile development and mineral precipitation and dissolution rates at the 226 ka Marine Terrace Chronosequence near Santa Cruz, CA. Aqueous compositions, fluid chemistry, transport, and mineral abundances are well characterized [White A. F., Schulz M. S., Vivit D. V., Blum A., Stonestrom D. A. and Anderson S. P. (2008) Chemical weathering of a Marine Terrace Chronosequence, Santa Cruz, California. I: interpreting the long-term controls on chemical weathering based on spatial and temporal element and mineral distributions. Geochim. Cosmochim. Acta 72 (1), 36-68] and were used to constrain the reaction rates for the weathering and precipitating minerals in the reactive transport modeling. When primary mineral weathering rates are calculated with either of two experimentally determined rate constants, the nonlinear, parallel rate law formulation of Hellmann and Tisserand [Hellmann R. and Tisserand D. (2006) Dissolution kinetics as a function of the Gibbs free energy of reaction: An experimental study based on albite feldspar. Geochim. Cosmochim. Acta 70 (2), 364-383] or the aluminum inhibition model proposed by Oelkers et al. [Oelkers E. H., Schott J. and Devidal J. L. (1994) The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions. Geochim. Cosmochim. Acta 58 (9), 2011-2024], modeling results are consistent with field-scale observations when independently constrained clay precipitation rates are accounted for. Experimental and field rates, therefore, can be reconciled at the Santa Cruz site. Additionally, observed maximum clay abundances in the argillic horizons occur at the depth and time where the reaction fronts of the primary minerals overlap. The modeling indicates that the argillic horizon at Santa Cruz can be explained almost entirely by weathering of primary minerals and in situ clay precipitation accompanied by undersaturation of kaolinite at the top of the profile. The rate constant for kaolinite precipitation was also determined based on model simulations of mineral abundances and dissolved Al, SiO2(aq) and pH in pore waters. Changes in the rate of kaolinite precipitation or the flow rate do not affect the gradient of the primary mineral weathering profiles, but instead control the rate of propagation of the primary mineral weathering fronts and thus total mass removed from the weathering profile. Our analysis suggests that secondary clay precipitation is as important as aqueous transport in governing the amount of dissolution that occurs within a profile because clay minerals exert a strong control over the reaction affinity of the dissolving primary minerals. The modeling also indicates that the weathering advance rate and the total mass of mineral dissolved is controlled by the thermodynamic saturation of the primary dissolving phases plagioclase and K-feldspar, as is evident from the difference in propagation rates of the reaction fronts for the two minerals despite their very similar kinetic rate laws. ?? 2009 Elsevier Ltd.

Maher, K.; Steefel, C. I.; White, A. F.; Stonestrom, D. A.

2009-01-01

323

CHEMICAL AND MINERALOGICAL CHARACTERISTICS OF FRENCH GREEN CLAYS USED FOR HEALING  

PubMed Central

The worldwide emergence of infectious diseases, together with the increasing incidence of antibiotic-resistant bacteria, elevate the need to properly detect, prevent, and effectively treat these infections. The overuse and misuse of common antibiotics in recent decades stimulates the need to identify new inhibitory agents. Therefore, natural products like clays, that display antibacterial properties, are of particular interest. The absorptive properties of clay minerals are well documented for healing skin and gastrointestinal ailments. However, the antibacterial properties of clays have received less scientific attention. French green clays have recently been shown to heal Buruli ulcer, a necrotic or ‘flesh-eating’ infection caused by Mycobacterium ulcerans. Assessing the antibacterial properties of these clays could provide an inexpensive treatment for Buruli ulcer and other skin infections. Antimicrobial testing of the two clays on a broad-spectrum of bacterial pathogens showed that one clay promotes bacterial growth (possibly provoking a response from the natural immune system), while another kills bacteria or significantly inhibits bacterial growth. This paper compares the mineralogy and chemical composition of the two French green clays used in the treatment of Buruli ulcer. Mineralogically, the two clays are dominated by 1Md illite and Fe-smectite. Comparing the chemistry of the clay minerals and exchangeable ions, we conclude that the chemistry of the clay, and the surface properties that affect pH and oxidation state, control the chemistry of the water used to moisten the clay poultices and contribute the critical antibacterial agent(s) that ultimately debilitate the bacteria.

Williams, Lynda B.; Haydel, Shelley E.; Giese, Rossman F.; Eberl, Dennis D.

2008-01-01

324

The Use of Clays as Sorbents and Catalysts  

Microsoft Academic Search

\\u000a This paper attempts to show how the structural, physical and chemical properties of clay minerals relate to their laboratory,\\u000a industrial and environmental uses as sorbents and catalysts. A brief review of the formulae, structures of clays and their\\u000a relationship to their chemical and physical properties is given. Isomorphous substitution of layer cations generates layer\\u000a charges, which are neutralised by the

M. Caine; G. Dyer; J. V. Holder; B. N. Osborne; W. A. Matear; R. W. McCabe; D. Mobbs; S. Richardson; L. Wang

325

Association of trace elements with mineral species in the New Albany oil shale  

SciTech Connect

X-Ray diffraction (XRD), electron microprobe (EMP), scanning electron microscopy (SEM) and neutron activation analysis (NAA) were used to identify mineral species in the New Albany shale and kerogen isolates. Elemental abundances were determined by NAA and distributions of Ni, V, As, and other elements with-in mineral grains were determined by EMP-XRF. Vanadium in the New Albany shale was found to be associated primarily with clay minerals (illite, montmorrillonite). In the New Albany kerogen, Ni and V were shown to be predominantly associated with the organic matrix. Pyrite (and/or marcasite) was shown to occur in two forms, a euhedral variety and as framboidal clusters. The Ni content of the framboidal variety was found to be higher than that of the euhedral pyrite.

Fitzgerald, S.L.; Day, J.W.; Mercer, G.E.; Filby, R.H. (Washington State Univ., Pullman (USA))

1989-03-01

326

Clay Mineralogy of Shallow Core Sediments of Lake Acigöl, Denizli, Turkey  

NASA Astrophysics Data System (ADS)

Lake Ac?göl is a hypersaline and active industrial salt production lake located in Denizli, Turkey. Lake Ac?göl has been investigated to elucidate the distribution clay minerals under the saline conditions of the lake and carbonate and ophiolitic rocks controlled lake basin. The lake is very shallow and generally characterized by an un-stratified and whole oxygenated water table. Determination clay minerals in the bulk samples via XRD method was not possible due to the their small amount. Therefore, the sequential clay enrichment procedure applied to the bulk samples such as sample dispersion, removal of soluble salts and ions, and particle-size fractionation. The XRD analyses of normal, glycolated and heat-treated shallow core samples show that the dominant clay minerals in the samples to be illite, including the swelling montmorillonite and kaolinite minerals are encountered less frequently. Glauberite, Blodite, Dansite and Nickelblodite have been also identified as soda minerals by XRD studies.

Budakoglu, Murat; Karaman, Muhittin; Geredeli, Serpil; Unal, Hatice; Abdelnasser, Amr; Kiran Yildirim, Demet

2014-05-01

327

Field trip guidebook on environmental impact of clays along the upper Texas coast  

NASA Technical Reports Server (NTRS)

The field trip was prepared to provide an opportunity to see first hand some the environmental hazards associated with clays in the Houston, Texas area. Because of the very high clay content in area soils and underlying Beaumont Formation clay, Houston is a fitting location to host the Clay Mineral Society. Examinations were made of (1) expansive soils, (2) subsidence and surface faulting, and (3) a landfill located southeast of Houston at the Gulf Coast Waste Disposal Authority where clay is part of the liner material.

Garcia, Theron D.; Ming, Douglas W.; Tuck, Lisa Kay

1991-01-01

328

Firing behaviour of the lower cretaceous clays of Tunisia  

NASA Astrophysics Data System (ADS)

The Valangenian-Hauterivian clays of Tunisia located at Djebel Oust were characterised by chemical analysis, X-ray diffraction and scanning electron microscopy in order to determine if these clays are appropriate for the manufacturing of ceramic products for construction. The mineralogical study shows that these clays are mainly of illitic type. However, other clay minerals, such as kaolinite, I/Sm mixed-layer, and chlorite, are also present. The chemical analysis indicates that the clays are notably siliceous, carbonated and aluminous. The content of iron is variable. Under firing tests on clay raw material until 1200 °C, quartz, cristobalite, hematite, mullite and sillimanite minerals were also identified. The amount of interstratified I/Sm and chlorite is higher in the samples located at the west zone of Djebel Oust than those located at the east. However, under firing behaviour of both types of raw samples seems to be similar. As conclusion of this study, these clays meet the firing specifications required for the manufacturing of ceramic products for construction.

Mahmoudi, Salah; Srasra, Ezzeddine; Zargouni, Fouad

2010-09-01

329

Functionalized synthetic clays designed for polymer-clay nanocomposites  

Microsoft Academic Search

Polymer-clay nanocomposites have many advantageous properties such as their light weight, transparency, flame retardency, barrier properties, and low cost. Exfoliation of natural clays into commercially important non-polar polymers such as polystyrene (PS) and polypropylene (PP) melts has been limited due to the immiscibility of these polymers with highly polar clays. Current means of addressing this problem, such as treating clays

Thuy Truong Chastek

2005-01-01

330

Zeta potential measurements on three clays from Turkey and effects of clays on coal flotation  

SciTech Connect

There is a growing trend of characterizing coal and coal wastes in order to study the effect of clays present in them during coal washing. Coarse wastes from the Zonguldak Coal Washery, Turkey, were characterized and found to contain kaolinite, illite, and chlorite. These three clays, obtained in almost pure form from various locations in Turkey, have been subjected to X-ray diffraction (XRD) analysis to assess their purity and zeta potential measurements in order to evaluate their properties in terms of their surface charge and point of zero charge (pzc) values. It was found from XRD data that these clays were almost pure and their electrokinetic potential should therefore be representative of their colloidal behavior. All three clay minerals were negatively charged over the range from pH 2.5 to 11. Chlorite and illite have pzc at pH 3 and pH 2.5, respectively, whereas kaolinite has no pzc. The effect of these clays in Zonguldak coal, wastes, and black waters on coal flotation was studied by floating artificial mixtures of Zonguldak clean coal (4.5% ash) and individual clay. The flotation tests on coal/individual clay revealed that each clay influences coal flotation differently according to its type and amount. Illite had the worst effect on coal floated, followed by chlorite and kaolinite. The loss of yield in coal was found to be 18% for kaolinite, 20% for chlorite, and 28% for illite, indicating the worst effect of illite and least for kaolinite during coal flotation.

Hussain, S.A. [Univ. of Engineering and Technology, Lahore (Pakistan). Mining Engineering Dept.] [Univ. of Engineering and Technology, Lahore (Pakistan). Mining Engineering Dept.; Demirici, S.; Oezbayoglu, G. [Middle East Technical Univ., Ankara (Turkey)] [Middle East Technical Univ., Ankara (Turkey)

1996-12-25

331

Using THEMIS to resolve the discrepancy between modeled phyllosilicate abundances and to assess the origin of phyllosilicate-bearing materials in Mawrth Vallis  

NASA Astrophysics Data System (ADS)

We examine the proposed explanations for the discrepancy that exists between phyllosilicate detection in visible/near-infrared vs. thermal infrared datasets -i.e., the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) vs. the Thermal Emission Spectrometer (TES). We test the effects of surface temperature discrepancies, physical (intimate) mixing of clay and non-clay bearing materials, and sub-pixel (checkerboard) mixing of clay and non-clay bearing material, all as a function of spatial resolution. Results indicate that a spatial resolution of 100 m/pixel (the resolution of data from the Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument), significantly improves the likelihood of phyllosilicate detection for all of the tested effects, even with its limited spectral resolution. We use spectral unit mapping techniques and the THEMIS dataset to provide the first phyllosilicate abundance maps of the Mawrth Vallis phyllosilicate-bearing units. With the limited spectral resolution, successful unmixing with a few endmembers can be achieved by carefully selecting the appropriate mineral endmembers based on the endmembers identified by both OMEGA/CRISM and TES. Derived abundances are then converted to major element oxides by assuming a representative mineral formula for each endmember present. The molar proportions of these oxides are used to evaluate the proposed formation mechanisms for clay in Mawrth Vallis. Our results indicate that the mineralogy is consistent with a model that requires the chemical weathering and leaching of primary volcanic material. The molar data reveal a trend suggesting the loss of feldspar (CaO + Na2O + K2O) and accumulation of insoluble clays (Al2O3), similar to that of terrestrial weathering of basaltic materials. The further accumulation of clays and loss of ferromagnesian minerals (FeO* + MgO) is only observed in advanced terrestrial weathering, and is not consistent with the THEMIS derived mineral abundances (* indicates all iron is reported as FeO). Regardless of the formation mechanism of the units in Mawrth Vallis, THEMIS modeling indicates phyllosilicate abundances of >50% with heterogeneous spatial distributions, which likely accounts for the discrepancy in detection between datasets. Furthermore, the molar proportions of oxides determined from these abundances are consistent with intermediate alteration of mafic primary material on Mars. This may be indicative of chemical weathering under relatively "dry" conditions (as compared to terrestrial weathering), as erosion and removal of weathering products soon after they are produced does not allow for the development of advanced weathering of those secondary products. With higher resolution mineral abundance modeling, those areas that preserve accumulation of phases characteristic of extreme weathering (e.g., oxides and hydroxides) zones may be revealed. Therefore, the current assessment of phyllosilicate formation in Mawrth Vallis may be a lower limit of the degree of chemical weathering preserved.

Viviano, C. E.; Moersch, J. E.

2012-12-01

332

Influence of Water on the Retention of Organic Probes on Clays Studied by IGC  

Microsoft Academic Search

Oil recovery is strongly related to the wettability of reservoir rocks that are formed of quartz grains attached by mineral hydroxides and clay minerals. Illites and kaolinites are the most active due to their high specific surface areas and electrical charge densities. Therefore, these minerals' relative affinities for oil or water when in contact with a water-oil mix are of

Henri Balard; ALAIN SAADA; BERNARD SIFFERT

1997-01-01

333

Clay nanocomposites for use in Li batteries  

NASA Astrophysics Data System (ADS)

Nanocomposites, materials made of more than one component and combined in an ordered manner on the nanometer scale, were synthesized using clay mineral hosts with various types of guests. The guests include polymers such as polyethylene oxide (PEO) and polyaniline (PANI), large molecules such as ethylmethyl sulfone, tetramethylene sulfone, and various length alkylamines. Vanadyl groups (VO 2+) were also incorporated with the clays. The otherwise non-swellable mica clay, synthetic Na-fluorophlogopite, was expanded by intercalation of acidic ions such as Cu2+ and Fe3+. As aqueous solutions, these ions caused the stable fluoromica to go from its dehydrated interlayer spacing of 9.8 A to over 14 A. This clay became a host for many other reactions including swelling with alkylamines to over 25 A. However, despite hydrated Cu2+ ions swelling fluorophlogopite, polymeric species such as PEO or PANI could not be inserted. Another clay that was used for formation of nanocomposites came from a procedure for the synthesis of Li-taeniolite, Li(Mg2Li)Si 4O10F2. The clay was synthesized following a high temperature method that led to a non-reactive product. Instead, a novel precursor route was employed that gave a clay product with a single hydration layer. Various chemical analyses gave a formula of Li0.8(Mg 2.2Li0.8)Si4O10(F1.6O 0.4)·H2O. For the purpose of forming nanocomposite electrolytes, ethylmethyl sulfone was synthesized and incorporated into the clay. For comparison of different shaped sulfones, tetramethylene sulfone also was inserted into the layers for electrolytic studies. To make a polymer-clay electrolyte, polyethylene oxide was intercalated into the Li-taeniolite. All of these new electrolyte materials were characterized using impedance spectroscopy for measurement of their conductivity. Syntheses and analyses are thoroughly discussed for all of these materials. Special attention is placed on powder x-ray diffraction and thermogravimetric techniques to understand the phases that are formed. The synthetic Li-taeniolite is also analyzed using direct-current plasma atomic emission spectroscopy (DCP-AES).

Moore, Gregory John

1999-11-01

334

Organophilic clay suspension medium  

SciTech Connect

This patent describes an improved liquid suspension medium for particulate solids. The suspension medium having been formed by admixing an organophilic clay wherein the clay is selected from the group consisting of bentonite, attapulgite, sepiolite and hectorite and admixtures thereof present in the quantity of about 0.5-8 weight percent with a liquid hydrocarbon present in the quantity of about 99-70 weight percent and at least one activator selected from the group consisting of phenyl hydroxyalkyl ethers.

Dixon, G.G.; Parlman, R.M.; Stewart, W.

1989-10-24

335

Isotopic biogeochemistry of the Oxford Clay Formation  

SciTech Connect

To better understand processes controlling production and preservation of the thermally immature organic matter in the Oxford Clay Fm. (Jurassic, U.K.), the authors measured the hydrogen index (HI), oxygen index (OI), abundance and isotopic composition of total organic carbon (TOC) and determined isotopic compositions of individual hydrocarbons (n-alkanes, pristane, and phytane). Bulk geochemical and molecular parameters vary as a function of abundance of TOC, lithology and macrofaunal biofacies. Shales dominated by epifaunal bivalve assemblages contain high abundances of TOC, high HI, low OI and high proportions of phytoplanktonic and bacterial organic matter. Conversely, shell beds and calcareous and silty clay beds have lower abundances of TOC, lower HI, and greater, but still not dominant proportions of terrestrial organic matter. [delta][sub TOC] ranges from [minus]26.5 to [minus]23.2[per thousand] vs. PDB and varies as a function of HI. In shales, abundance of C-13 increase with HI and with concentrations of TOC. This variation might be attributed to drawdown of CO[sub 2] by producers. In shell beds and in calcareous and silty clay beds, decreases in TOC and HI are correlated with enrichment of C-13, a signal that might be attributed to greater heterotrophic reworking. Isotopic compositions of pristane and phytane in each unit are equal and likely indicate that the C-13 content of algal lipids. [delta] values of TOC are as much as 8[per thousand] higher than those of pristane and phytane, indicating that the bulk of the TOC probably derives from consumer organisms. The greatest enrichment of C-13 in TOC occurs in one horizon where paleontological evidence indicates [ge]7 trophic levels in the food chain. Consideration of the overall patterns of variations allows distinction between effects of CO[sub 2] drawdown and heterotrophic reworking.

Kenig, F.; Hayes, J.M. (Indiana Univ., Bloomington, IN (United States). Biogeochemical Labs.); Popp, B.N. (Univ. of Hawaii, Honolulu, HI (United States). Dept. of Geology and Geophysics); Summons, R. (Bureau of Mineral Resources, Canberra (Australia))

1992-01-01

336

Clay VLSI layout language  

SciTech Connect

Clay is a procedural language based on C for nMOS VLSI layout. The primitive objects in Clay are wires and symbols. Wires are line segments of a given mask layer. Symbols are small rigid pieces of a layout, such as contact cuts or transistors. Wires and symbols are created and placed in a layout using programming language constructs. Composite structures, such as routing networks, inverters, registers, and PLAs can be written as functions that call lower-level functions or place the necessary wires and symbols directly. The programming language nature of Clay make it convenient to parameterize local and global features of a design, such as the size of a certain pullup transistor or the number of registers in an array. A key property of Clay layouts is that they are flexible. A section of a layout may be stretched as necessary to satisfy constraints on interface wires (those that have connections outside the cell's boundary.) This simplifies cell assembly by eliminating the need for exact pitch matching. All layout in Clay takes place within ordered contexts. Objects placed inside ordered contexts are separated horizontally or vertically, according to the sequential execution of program. There are two steps in the translation of a Clay program. The execution of the user's code wires a system of constraints as a side-effect. The layout constraint solver reads these constraints and outputs a rigid layout mask.

North, S.C.

1986-01-01

337

Chemistry, mineralogy and origin of the clay-hill nitrate deposits, Amargosa River valley, Death Valley region, California, U.S.A.  

USGS Publications Warehouse

The clay-hill nitrate deposits of the Amargosa River valley, California, are caliche-type accumulations of water-soluble saline minerals in clay-rich soils on saline lake beds of Miocene, Pliocene(?) and Pleistocene age. The soils have a maximum thickness of ??? 50 cm, and commonly consist of three layers: (1) an upper 5-10 cm of saline-free soil; (2) an underlying 15-20 cm of rubbly saline soil; and (3) a hard nitrate-rich caliche, 10-20 cm thick, at the bottom of the soil profile. The saline constituents, which make up as much as 50% of the caliche, are chiefly Cl-, NO-3, SO2-4 and Na+. In addition are minor amounts of K+, Mg2+ and Ca2+, varying, though generally minor, amounts of B2O3 and CO2-3, and trace amounts of I (probably as IO-3), NO-2, CrO2-4 and Mo (probably as MoO2-4). The water-soluble saline materials have an I/Br ratio of ??? 1, which is much higher than nearly all other saline depostis. The principal saline minerals of the caliche are halite (NaCl), nitratite (NaNO3), darapskite (Na3(SO4)(NO3)??H2O), glauberite (Na2Ca(SO4)2), gypsum (CaSO4??2H2O) and anhydrite (CaSO4). Borax (Na2B4O5(OH)4??8H2O), tincalconite (Na2B4O5(OH)4??3H2O) and trona (Na3(CO3)(HCO3)??2H2O) are abundant locally. The clay-hill nitrate deposits are analogous to the well-known Chilean nitrate deposits, and probably are of similar origin. Whereas the Chilean deposits are in permeable soils of the nearly rainless Atacama Desert, the clay-hill deposits are in relatively impervious clay-rich soils that inhibited leaching by rain water. The annual rainfall in the Death Valley region of ??? 5 cm is sufficient to leach water-soluble minerals from the more permeable soils. The clay-hill deposits contain saline materials from the lake beds beneath the nitrate deposits are well as wind-transported materials from nearby clay-hill soils, playas and salt marshes. The nitrate is probably of organic origin, consisting of atmospheric nitrogen fixed as protein by photoautotrophic blue-green algae, which are thought to form crusts on soils at the sites of the deposits when moistened by rainfall. The protein is subsequently transformed to nitrate by autotophic bacteria. ?? 1988.

Ericksen, G. E.; Hosterman, J. W.; St. , Amand, P.

1988-01-01

338

Synthesis of highly active and thermally stable nanostructured Pt/clay materials by clay-mediated in situ reduction.  

PubMed

Novel and intriguing one-pot in situ method for the preparation of nanostructured Pt-clay materials under simple conditions is reported. In this synthesis, an inorganic clay mineral such as synthetic hectorite ("Laponite XLG") or natural montmorillonite ("Kunipia F") serves as a mild and effective reducing agent for Pt ions, which is uncommon for such a clay system, and also acts as an outstanding stabilizer for the resulting Pt nanoparticles. In aqueous solution, exfoliated colloidal clay platelets forms complex with Pt ions in the initial stage of mixing. Devoid of any organic dispersants or external reducing agents, subsequently, the Pt nanoparticles (3-6 nm) generated by clay-assisted in situ reduction of Pt ions successfully anchored onto the clay nanoplatelets. The Pt-clay material features a very high surface area (312 m(2) g(-1)) and has excellent catalytic activity, as was kinetically evaluated via the reduction of 4-nitrophenol with NaBH(4). After drying, this remarkably stable nanocomposite is completely redispersible in water and displays extreme thermal stability (up to 500 °C). On the basis of these results, this synthetic strategy is anticipated to be a very simple, economical, and green approach for the synthesis of nanostructured Pt-clay materials. PMID:23343394

Varade, Dharmesh; Haraguchi, Kazutoshi

2013-02-12

339

Fe-Smectite-Glauconite Transition in Hydrothermal Green Clays from the Galapagos Spreading Center  

Microsoft Academic Search

X-ray powder diffraction (XRD) and energy-dispersive X-ray analyses (EDX) of individual clay particles from hydrothermal mounds in the Galapagos spreading center (GSC) (Deep Sea Drilling Project, hole 509B) and high-resolution transmission electron microscopy (HRTEM) of the <2-urn size fraction of these sediments were carried out to document the mineralogy, geochemistry, and evolution of their clay horizons. The hydrothermal clay minerals

Martine Buatier; JOSE HONNOREZ; GABRIELLE EHRET

1989-01-01

340

abundance: High Redshift Cluster Abundance  

NASA Astrophysics Data System (ADS)

abundance, written in Fortran, provides driver and fitting routines to compute the predicted number of clusters in a ?CDM cosmology that agrees with CMB, SN, BAO, and H0 measurements (up to 2010) at some specified parameter confidence and the mass that would rule out that cosmology at some specified sample confidence. It also computes the expected number of such clusters in the light cone and the Eddington bias factor that must be applied to observed masses.

Mortonson, Michael; Hu, Wayne; Huterer, Dragan

2014-01-01

341

Visible and Near Infrared Absorption Coefficients of Kaolinite and Related Clays.  

National Technical Information Service (NTIS)

Clay minerals, by their very nature, are always composed of aggregates of fine particles, a situation which makes conventional transmission spectroscopy and application of the Bouguer-Lambert law difficult, because of the intense scattering of light in th...

J. D. Lindberg M. S. Smith

1973-01-01

342

Effect of ten quaternary ammonium cations on tetrachloromethane sorption to clay from water  

Microsoft Academic Search

The mineral surface of Wyoming bentonite (clay) was modified by replacing inorganic ions by each of 10 quaternary ammonium compounds, and tetrachloromethane sorption to the modified sorbents from water was studied. Tetrachloromethane sorption from solution to clay modified with tetramethyl-, tetraethyl-, benzyltrimethyl-, or benzyltriethylammonium cations generally is characterized by relatively high solute uptake, isotherm nonlinearity, and competitive sorption (with trichloroethene

James A. Smith; Peter R. Jaffe; Cary T. Chiou

1990-01-01

343

Differences in the rheology and surface chemistry of kaolin clay slurries: The source of the variations  

Microsoft Academic Search

Kaolinite clays from two sources were found to display different rheological and electrokinetic behaviour despite having similar mineral composition. This difference is mainly due to the surface chemistry at the edges of the clay particles. Making the edge surface chemistry similar with an adsorbed small anionic additive such as citrate, produced a similar yield stress–pH behaviour for the different kaolin

E.-Jen Teh; Y. K. Leong; Y. Liu; A. B. Fourie; M. Fahey

2009-01-01

344

Temperature and pH controls over isotopic fractionation during adsorption of boron on marine clay  

Microsoft Academic Search

The variation of adsorption constants and isotope fractionation with pH and temperature during the adsorption of B from sea water onto marine clay have been examined. The controls over adsorption are similar to those exhibited by pure clay minerals. The isotope fractionations are the result of equilibrium processes, not kinetic effects. Variations in the measured fractionation factor with pH arise

M. R. Palmer; A. J. Spivack; J. M. Edmond

1987-01-01

345

Pharmaceutical applications of some spanish clays (sepiolite, palygorskite, bentonite): some preformulation studies  

Microsoft Academic Search

In this work, a pharmaceutical preformulation study of four Spanish clays (two sepiolites, one palygorskite and one bentonite) is presented, comparing the results obtained with those of three mineral products currently used in pharmaceutical technology. The results showed that the mineralogical and chemical purity of these clays is similar and even higher than that of the three commercial products. The

C Viseras; A Lopez-Galindo

1999-01-01

346

Iron oxyhydroxide nanostructured in montmorillonite clays: Preparation and characterization.  

PubMed

Akaganéite is a very rare iron oxyhydroxide in nature. It can be obtained by many synthetic routes, but thermohydrolysis is the most common method reported in the literature. In this work, akaganéite-like materials were prepared through the thermohydrolysis of FeCl(3).6H(2)O in water and suspensions containing clay minerals. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) data show that the clays determine the crystal phase and size of the iron oxyhydroxide crystals. According to XRD and FTIR data, beta-FeO(OH) (akaganéite) is the main metal oxyhydroxide phase. Considering the small basal spacing (d(001)) displacement observed when comparing the XRD patterns of pristine clays with the composites containing beta-FeO(OH), the iron oxyhydroxide should be mostly located on the basal and edge surfaces of the clay minerals. UV-Vis electronic absorption spectra indicate that the preferred phase of the iron oxyhydroxide is determined by the nature of the clay minerals. PMID:20609843

Villalba, Juan Carlo; Constantino, Vera R L; Anaissi, Fauze Jacó

2010-09-01

347

A Thick (>1500 m) Section of Clay-Bearing Clastic Rocks Near Mawrth Vallis: Evidence for Early Crustal Processing on Mars  

NASA Astrophysics Data System (ADS)

Aluminous and ferruginous clay minerals detected in the Mawrth Vallis area [Poulet et al., 2005] correspond to ancient, light-toned (TES albedo = ~0.22), layered bedrock. We conclude that the layered surface materials are indeed bedrock based on 1) their weathering style, they form scarps, steep cliffs, buttes, and mesas; and 2) their thermal inertia which, based on THEMIS data, is > 500 J K-1 m-2 s-1/2. Because the rocks are nearly flat-lying and morphologically unique, it is possible to make stratigraphic correlations throughout the Mawrth Vallis area. The clay mineral deposits all correspond to a complex section of rock present throughout an area similar in size to the Colorado Plateau. Through stratigraphic correlations and basic structural interpretations, we conclude that the layered clay mineral-bearing bedrock is >1500 m thick and contains 100s to 1000s of individual layers, indicating a dynamic environment during deposition. At least some of the light-toned layers are phyllosilicate-poor, making origin of the clay minerals by regional-scale, subsurface replacement an unlikely scenario. Geomorphic evidence shows that the light-toned rock unit was eroded and incised after lithification and it is disconformably overlain by a clay mineral-poor, dark-toned (TES albedo = ~0.12), layered sedimentary rock that occurs at all elevations throughout the area. This dark toned unit is interpreted as sedimentary rock because it contains abundant evidence for inverted topography in the form of meandering streams that may have fed Mawrth Vallis. The light-toned, clay mineral-bearing unit ends abruptly at the present day erosional remnant of the dichotomy boundary, though remnants of it are observed in buttes within the northern plains. Therefore, either the light-toned, clay mineral-bearing unit is older than the dichotomy (possibly > 4 Ga), or the basin in which these units were deposited was previously bounded to the north by a topographic barrier that no longer exists. It is unclear whether the upper, dark-toned units could also be older than the dichotomy. It is impossible to assign a unique interpretation to the light- toned clay-bearing rock unit, as it could ultimately be sedimentary rock or altered pyroclastic rock. However, its preservation implies the former existence of a depositional basin in this area. If the layered rocks are interpreted as volcanic and erosion erased the evidence of associated volcanic structures, then the erosion must have generated sediments that would have been deposited along with volcanic materials in the basin. Regardless of the interpretation of volcanoclastic + sedimentary versus purely sedimentary origins, these rock units are seemingly a window into early geologic processes in the Solar System, in a time period not observable on Earth. Indeed the evidence for ancient orogenic systems on Earth lies in ancient sedimentary sequences. This package of ancient clastic rocks may represent ancient fluvial, lacustrine, and/or marine deposits, and could have implications for early orogenic processes on Mars.

Michalski, J. R.; Noe, E.; Fergason, R.

2006-12-01

348

A mechanistic model for the spectral induced polarization of clay materials  

Microsoft Academic Search

Water-saturated clay-rich media exhibit low-frequency (1 Hz to 1 MHz) effective conductivity and effective permittivity dispersions that are the consequence of both the polarization of the mineral\\/water interface coating the surface of the grains and the Maxwell-Wagner polarization. These low-frequency properties are modeled by combining (1) a complexation model of the surface properties of clay minerals (kaolinite, illite, and smectite),

P. Leroy; A. Revil

2009-01-01

349

Clay-based geothermal drilling fluids  

SciTech Connect

The rheological properties of fluids based on fibrous clays such as sepiolite and attapulgite have been systematically examined under conditions similar to those of geothermal wells, i.e. at elevated temperatures and pressures in environments with concentrated brines. Attapulgite- and sepiolite-based fluids have been autoclaved at temperatures in the range from 70 to 800/sup 0/F with the addition of chlorides and hydroxides of Na, K, Ca, and Mg. The rheological properties (apparent and plastic viscosity, fluid loss, gel strength, yield point, and cake thickness) of the autoclaved fluids have been studied and correlated with the chemical and physical changes that occur in the clay minerals during the autoclaving process.

Guven, N.; Carney, L.L.; Lee, L.J.; Bernhard, R.P.

1982-11-01

350

Clay particles destabilize engineered nanoparticles in aqueous environments.  

PubMed

Given the ubiquity of natural clay minerals, the most likely interaction of nanoparticles released into an aquatic environment will be with suspended clay minerals. Thus, the transport of engineered nanoparticles in the subsurface and the water column will most likely be altered by their interaction with these minerals. We studied the interactions of two of the most produced nanoparticles, Ag and TiO(2), and montmorillonite to determine how heteroaggregation can alter the stability of nanoparticle/clay mineral mixtures. Since at low pH montmorillonite has a negatively charged basal plane and positively charged edges, its interaction with these nanoparticles at different pH lead to unusual behaviors. There are six different interactions for each clay-nanoparticle pair. At pH values below the IEP of montmorillonite edge site, montmorillonite reduced the stability of both negatively charged Ag and positively charged TiO(2) nanoparticles. Surprisingly this enhanced coagulation only occurs within an intermediate ionic strength range. The spillover of the montmorillonite basal plane electric double layer to the montmorillonite edge may screen the electrostatic attraction between Ag and the montmorillonite edge at low ionic strength, whereas a repulsion between TiO(2) and montmorillonite face sites may restabilize the mixture. PMID:22721423

Zhou, Dongxu; Abdel-Fattah, Amr I; Keller, Arturo A

2012-07-17

351

Regularities of tinting ceramics based on low-melting clays  

Microsoft Academic Search

The effect of the mineral composition of low-melting red-burning clay, the gaseous medium, and the type of raw materials on\\u000a the formation of light-colored (white) ceramics as a consequence of the crystallization of iron-bearing crystal phases is\\u000a established.

N. D. Yatsenko; V. P. Rat’kova

2006-01-01

352

Controlling Harmful Algal Blooms Through Clay Flocculation1  

Microsoft Academic Search

ABSTRACT. The potential use of clays to control harmful algal blooms (HABs) has been explored in East Asia, Australia, the United States, and Sweden. In Japan and South Korea, minerals such as montmorillonite, kaolinite, and yellow loess, have already been used in the field effectively, to protect fish mariculture fromCochlodiniumspp. and other blooms. Cell removal occurs through the flocculation of

MARIO R. SENGCO; DONALD M. ANDERSON

2004-01-01

353

Macroterme Geophagy and Pregnancy Clays in Southern Africa  

Microsoft Academic Search

Field observations in five countries of southern Africa reveal that geophagy among pregnant women is very widespread in rural areas and that a geophagy trade exists in urban markets. Giant mounds built by the termite genus macrotermes are a major source of pregnancy clay. In terms of supplying essential minerals and trace elements to the fetus, in needy circumstances, it

John M. Hunter

1993-01-01

354

Clay Mineralogy and Organic Carbon Burial in Proterozoic Basins  

NASA Astrophysics Data System (ADS)

Pedogenic, or soil-derived, clay minerals have long been implicated in the efficiency of organic matter (OM) burial and coincident accumulation of atmospheric oxygen. As diagenesis and metamorphism obscure pedogenic clays in many Precambrian rocks, clay mineralogy and its role in OM burial through much of geologic time remains incompletely understood. In this study we analyzed the mineralogy and total organic carbon (TOC) of a number of organic rich shales deposited in Late Archean to Early Cambrian sedimentary basins. Across all samples, diagenetic transformation of pre-existing smectite minerals has led to the predominance of glauconite and the diagenetic 1M and 1Md illite polytypes, which, collectively, can be thought of as "proto-smectite". The correlations between TOC and illite crystallinity suggest that OM burial and preservation in the Proterozoic proceeded by the physical aggregation of OM and pedogenic clays upon deposition. This association, in turn, led to the interference of OM with the illitization process, resulting in the ubiquitous relationship between high surface area (or, finely crystalline) material and high TOC. This interpretation is consistent with suggestions that the preservation of OM after burial proceeds by physical exclusion, with mineral surfaces effectively isolating OM from enzymatic breakdown. Together, it appears that the deposition of pedogenic clays has remained broadly constant over Proterozoic time and into the Early Cambrian, which is incompatible with the hypothesis that late Neoproterozoic oxygenation was influenced by increases in pedogenic clay production. As no clear temporal relationship exists between clays and OM, Precambrian oxygenation was likely controlled by other mechanisms.

Tosca, N. J.; Johnston, D. T.; Mushegian, A.; Rothman, D. H.; Knoll, A. H.

2008-12-01

355

Feldspar minerals as efficient deposition ice nuclei  

NASA Astrophysics Data System (ADS)

Mineral dusts are well known to be efficient ice nuclei, where the source of this efficiency has typically been attributed to the presence of clay minerals such as illite and kaolinite. However, the ice nucleating abilities of the more minor mineralogical components have not been as extensively examined. As a result, the deposition ice nucleation abilities of 24 atmospherically relevant mineral samples have been studied, using a continuous flow diffusion chamber at -40.0 ± 0.3 °C and particles size-selected at 200 nm. By focussing on using the same experimental procedure for all experiments, a relative ranking of the ice nucleating abilities of the samples was achieved. In addition, the ice nucleation behaviour of the pure minerals is compared to that of complex mixtures, such as Arizona Test Dust (ATD) and Mojave Desert Dust (MDD), and to lead iodide, which has been previously proposed for cloud seeding. Lead iodide was the most efficient ice nucleus (IN), requiring a critical relative humidity with respect to ice (RHi) of 122.0 ± 2.0% to activate 0.1% of the particles. MDD (RHi) 126.3 ± 3.4%) and ATD (RHi 129.5 ± 5.1%) have lower but comparable activity. From a set of clay minerals (kaolinite, illite, montmorillonite), non-clay minerals (e.g. hematite, magnetite, calcite, cerussite, quartz), and feldspar minerals (orthoclase, plagioclase) present in the atmospheric dusts, it was found that the feldspar minerals (particularly orthoclase) and some clays (particularly kaolinite) were the most efficient ice nuclei. Orthoclase and plagioclase were found to have critical RHi values of 127.1 ± 6.3% and 136.2 ± 1.3%, respectively. The presence of feldspars (specifically orthoclase) may play a significant role in the IN behaviour of mineral dusts despite their lower percentage in composition relative to clay minerals.

Yakobi-Hancock, J. D.; Ladino, L. A.; Abbatt, J. P. D.

2013-11-01

356

Feldspar minerals as efficient deposition ice nuclei  

NASA Astrophysics Data System (ADS)

Mineral dusts are well known to be efficient ice nuclei, where the source of this efficiency has typically been attributed to the presence of clay minerals such as illite and kaolinite. However, the ice nucleating abilities of the more minor mineralogical components have not been as extensively examined. As a result, the deposition ice nucleation abilities of 24 atmospherically-relevant mineral samples have been studied, using a continuous flow diffusion chamber at -40.0 ± 0.3 °C. The same particle size (200 nm) and particle preparation procedure were used throughout. The ice nucleation behaviour of the pure minerals is compared to that of complex mixtures, such as Arizona Test Dust (ATD) and Mojave Desert Dust (MDD), and to lead iodide, which has been previously proposed for cloud seeding. Lead iodide was the most efficient ice nucleus (IN), requiring a critical relative humidity with respect to ice (RHi) of 122.0 ± 2.0% to activate 0.1% of the particles. MDD (RHi 126.3 ± 3.4%) and ATD (RHi 129.5 ± 5.1%) have lower but comparable activity. From a set of clay minerals (kaolinite, illite, montmorillonite), non-clay minerals (e.g. hematite, magnetite, calcite, cerussite, quartz), and feldspar minerals (orthoclase, plagioclase) present in the atmospheric dusts it was found that the feldspar minerals (particularly orthoclase), and not the clays, were the most efficient ice nuclei. Orthoclase and plagioclase were found to have critical RHi values of 127.1 ± 6.3% and 136.2 ± 1.3%, respectively. The presence of feldspars (specifically orthoclase) may play a significant role in the IN behaviour of mineral dusts despite their lower percentage in composition relative to clay minerals.

Yakobi-Hancock, J. D.; Ladino, L. A.; Abbatt, J. P. D.

2013-06-01

357

Clay mineralogy of weathering profiles from the Carolina Piedmont.  

USGS Publications Warehouse

Saprolite profiles (12) that formed over various crystalline rocks from the Charlotte 1o X 2o quadrangle showed overall similarity in their clay mineralogy to depths of 6 to 45 m indicating control by weathering processes rather than by rock type. Most saprolite contained 10-25% clay, and ranged 3 to 70%. Kaolinite and halloysite composed = or >75% of the clay fraction of most samples. The ratio kaolinite:halloysite ranged widely, from 95% kaolinite to 90% halloysite, independent of depth. Clay-size mica was present in all profiles, and ranged 5-75% over a sericite schist. Mixed-layer mica-smectite and mica-vermiculite were subordinate; discrete smectite and vermiculite were rare. The abundance of halloysite indicates a continuously humid environment since the time of profile formation, because of the rapidity with which halloysite dehydrates irreversibly. -R.S.M.

Loferski, P. J.

1981-01-01

358

Rattles of Clay.  

ERIC Educational Resources Information Center

Using the rattles of Native American cultures as inspiration, students used pinching, coiling, and slab and molding techniques to form the bodies of rattles and clay pellets for sound. Surface decoration included glazed and unglazed areas as well as added handles, feathers, and leather. (IS)

Banning, Donna

1983-01-01

359

Moving Along: Sporting Clay.  

ERIC Educational Resources Information Center

Presents a junior high school student art project where three-dimensional art sculptures of surfing, snow boarding, or dirt biking were created. Discusses how the students created their three-dimensional works of art using a clay-slab technique. (CMK)

Hiller, Peter

2002-01-01

360

NITROGEN MINERALIZATION OF IMMATURE MUNICIPAL SOLID WASTE COMPOST  

Microsoft Academic Search

Nitrogen (N) mineralization of a municipal solid waste compost (MSWC) blended with two soils of different textures (clay and sandy) and the emergence of ryegrass plants treated with different N fertilizers were studied. Compost-soil samples showed initially a strong immobilization of the mineral N present in the blends. Only after 12 weeks of incubation, positive mineralization was observed in both

R. López; F. Cabrera; J. M. Murillo

2011-01-01

361

A structured Cam Clay model  

Microsoft Academic Search

A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Struc- tured Cam Clay model, is formulated by introducing the influence of soil structure into the Modified Cam Clay model. The proposed model is hierarchical, i.e., it is identical to the Modified Cam Clay soil model if a soil has no structure

M. D. Liu; J. P. Carter

2002-01-01

362

CLAYS AND CLAY INTERCALATION COMPOUNDS:Properties and Physical Phenomena  

NASA Astrophysics Data System (ADS)

The materials properties and physical phenomena exhibited by layered silicate clays and clay intercalation compounds, a subgroup of the general class of layered solids, are reviewed. The importance of layer rigidity is emphasized. Clays are compared and contrasted with the more familiar layered solids such as graphite and dichalcogenides. Some of the unusual structural features of clays including interstratification, swelling, and the lack of staging are discussed and explained qualitatively and quantitatively. Novel magnetic phenomena such as that associated with a disordered two-dimensional kagome antiferromagnet formed in synthetic clays and the effect of co-intercalated water on the crystal field-induced magnetic ordering in natural clays are described and analyzed. The vibrational excitations in clays are addressed in terms of lattice dynamical models for the phonon dispersion curves. The theoretical models are compared with experimental measurements including neutron scattering and Raman spectroscopy.

Solin, S. A.

1997-08-01

363

Evaporite mineral assemblages in the nakhlite (martian) meteorites  

NASA Astrophysics Data System (ADS)

A mineralogical study of the three nakhlite (martian) meteorites has revealed that they contain evaporite mineral assemblages. Lafayette has Ca-siderite and clay minerals (smectite/illite) along fractures within olivine; Governador Valadares contains clay mineral veins in olivine, with siderite, gypsum and anhydrite in interstitial areas; Nakhla has clay and gypsum veins in olivine, with Mg-, Mn-rich siderite, anhydrite and halite in interstitial sites. Minor goethite is also present in the three meteorites. Lafayette siderite has the range of compositions (mol%) CaCO 3 21.6-36.8, MnCO 3 4.2-35.3, MgCO 3 0.1-1.6, FeCO 3 27.4-67.0; Governador Valadares has CaCO 3 3.6-11.1, MnCO 3 1.1-2.1, MgCO 3 9.0-29.2, FeCO 3 64.3-77.8; Nakhla has CaCO 3 0.1-5.7, MnCO 3 1.0-39.9, MgCO 3 2.0-40.9, FeCO 3 23.2-87.0. Trace element abundances for clay, siderite and gypsum are all similar with LREE, Y>HREE, Zr, Nb and La 0.9-95×CI; Y 0.2-2.4×CI. This pattern of abundances reflects the trace element contents of the parent fluid, which in turn were derived through dissolution of LREE-enriched feldspathic mesostasis. The close similarities in silicate petrography and radiometric ages determined by other workers for these olivine clinopyroxenites suggests that the parent rocks were close to one another on Mars and therefore the same fluid may have been responsible for the precipitation of the evaporite mineral assemblages. Lafayette contains the mineral assemblage and siderite composition which are least soluble in water and Nakhla contains the most soluble minerals and carbonate composition. On the basis of our new data we consider a new model of progressive evaporation from a Na-Mg-Fe-Ca-SO 4-Cl-H 2O-HCO 3- acidic brine in an area of enclosed drainage (e.g. crater or low-lying flood plain) on Mars. Partial dissolution of near-surface rocks by the acidic brine released Fe, Mg and trace elements from mesostasis and olivine into the fluid. The Lafayette assemblage was formed where >25% volume of the water remained following evaporation, Governador Valadares 20% and Nakhla <10%. This model is consistent with martian ground temperatures at >0°C and a thicker atmosphere (pCO 2=30-100 mbar) at least over brief periods of time ?1.3 Ga.

Bridges, J. C.; Grady, M. M.

2000-03-01

364

Hydrothermal Alteration in the PACMANUS Hydrothermal Field: Implications From Secondary Mineral Assemblages and Mineral Chemistry, OPD Leg 193  

NASA Astrophysics Data System (ADS)

Leg 193 of the Ocean Drilling Program investigated the subsurface nature of the active PACMANUS hydrothermal field in the Manus backarc basin near Papua New Guinea. Drilling in different areas on the felsic neovolcanic Pual Ridge, including the high-temperature black smoker complex of Roman Ruins and the low-temperature Snowcap site with diffusive discharge yielded a complex alteration history with a regional primary alteration being overprinted by a secondary mineralogy. The intense hydrothermal alteration at both sites shows significant differences in the secondary mineralogy. At Roman Ruins, the upper 25 m of hydrothermally altered rocks are characterized by a rapid change from secondary cristobalite to quartz, implying a high temperature gradient. From 10 to 120 mbsf the clay mineralogy is dominated by illite and chlorite. The chlorite formation temperature calculated from oxygen isotope data lies at 250° C in 116 mbsf which is similar to the present fluid outflow temperatures of 240-250° C (Douville et al., 1999, Geochim. Cosmochim. Acta, 63, 627-643). Drilling in the Snowcap field recovered evidence for several stages of hydrothermal alteration. Between 50 and 150 mbsf, cristobalite and chlorite are the most abundant alteration minerals while hydrothermal pyrophyllite becomes abundant in some places At 67 mbsf, the isotopic composition of pyrophyllite gives a temperature for ist formation at 260° C whereas at 77 and 116 mbsf the pyrophyllite displays the highest temperatures of formation (>300° C). These temperatures are close to the maximum measured borehole temperatures of 313° C. The appearance of assemblages of chlorite, chlorite-vermiculite, chlorite-vermiculite-smectite and illite-smectite as well as the local development of corrensite below 150 mbsf suggests that the alteration at Snowcap may be more complex than that beneath Roman Ruins. Detailed geochemical studies of the authigenic clay mineral phases will provide further insights into the chemical changes due to hydrothermal alteration.

Lackschewitz, K. S.; Kummetz, M.; Kummetz, M.; Ackermand, D.; Botz, R.; Devey, C. W.; Singer, A.; Stoffers, P.

2001-12-01

365

Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide.  

PubMed

Supercritical carbon dioxide (scCO2) treatments of a montmorillonite (MMT) intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT) led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline ? form of syndiotactic polystyrene (s-PS), have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals. PMID:24790956

Longo, Simona; Mauro, Marco; Daniel, Christophe; Galimberti, Maurizio; Guerra, Gaetano

2013-01-01

366

Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide  

PubMed Central

Supercritical carbon dioxide (scCO2) treatments of a montmorillonite (MMT) intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT) led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline ? form of syndiotactic polystyrene (s-PS), have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersio