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1

Effect of nitridation on the aqueous dissolution of Na2O-K2O-CaO-P2O5 metaphosphate glasses.  

PubMed

The use of oxynitride glasses is presented as an alternative for the preparation of bioresorbable phosphate glasses with a controlled dissolution rate. This work describes the design of oxynitride phosphate glasses within the systems of composition (50-x)Na(2)O·xCaO·50P(2)O(5) and (25-(x/2))Na(2)O·(25-(x/2))K(2)O·xCaO·50P(2)O(5) (x=5, 10, 15, 20 mol.%) throughout the processing parameters of the ammonolysis reaction and the glass composition. Mixed-alkali sodium-potassium phosphate glasses with low CaO contents present the best characteristics for nitridation. The dissolution rate has been determined by immersion of glass samples in water, at constant temperature of 37 °C, and has been discussed as a function of both modifiers composition and nitrogen content incorporated in the glasses through ammonolysis. All oxynitride glass compositions dissolve congruently and their dissolution rate decreases by more than three orders of magnitude for the highest nitrogen contents. However, it has been demonstrated that nitrogen contents as low as 2-3 wt.% (i.e. a 0.2N/P ratio) are sufficient to decrease the dissolution rate by one order of magnitude with respect to the pure oxide glasses. Novel oxynitride phosphate glasses with a controlled and congruent dissolution are proposed for future applications in biodegradable composite materials, tissue engineering or host matrices for the controlled release of drugs. PMID:21440095

Riguidel, Quentin; Muñoz, Francisco

2011-04-02

2

Second harmonic generation and fabrication of transparent K2O-Na2O-Nb2O5-TeO2 glass-ceramics  

Microsoft Academic Search

To develop and utilize TeO2-based glasses as nonlinear optical materials or matrix glasses, xK(2)O-(14-x)Na2O-14Nb(2)O(5)-72TeO(2) (x=0 similar to 14 mol%) glasses were prepared using a conventional melt quenching method and then the nano-crystallization behavior and second harmonic generation (SHG) properties of these glasses were investigated. Although SHG was clearly observed in 10K(2)O-4Na(2)O-14Nb(2)O(5)-72TeO(2) glass-ceramics consisting of a nano-crystalline phase, the 14Na(2)O-14Nb(2)O(5)-72TeO(2) glass-ceramic

Euh Duck Jeong; Pramod H. Borse; Jae Sung Lee; Myoung Gyu Ha; Hyuk Kyu Pak; Takayuki Komatsu; Hyun Gyu Kim

2006-01-01

3

Mössbauer study of crystallization of glasses in the system K 2 O-Na 2 O-CaO-MgO-Al 2 O 3 SiO 2  

Microsoft Academic Search

Mössbauer spectroscopy has been used to study several glasses and glass ceramics based on the system K2O-Na2O-CaO-MgO-Al2O3-SiO2 with additions of Fe2O3, Fe3O4 and P2O5. The change of co-ordination and proportion of Fe2+ and Fe3+ occurring during the transformation from glass to glass ceramic was studied. By means of the nuclear magnetic hyperfine splitting effect Fe3O4 was found in glass ceramics

Yang Xiong Ying; M. Cable; Zhong Zu Ping; J. M. Williams

1992-01-01

4

Crystallization Behavior and Microstructure of Silica-Free 5K2O-45CaO-50P2O5 Bioglass  

NASA Astrophysics Data System (ADS)

The crystallization behavior and microstructure of silica-free 5K2O-45CaO-50P2O5 (KCP) bioglass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning election microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The activation energy for the KCP bioglass crystallization is found to be 337.4 kJ/mol using a nonisothermal method. The crystalline phases of the glass surface determined by XRD are KCa(PO3)3, 4CaO·3P2O5, and ?-Ca(PO3)2 when the KCP bioglass is crystallized at 903 K for 4 hours. The crystalline phase of the powder samples determined by XRD is ?-Ca(PO3)2 when silica-free KCP glasses crystallized at 873 to 1073 K for 8 hours. Crystallization starts at the surface of the KCP bioglass and then proceeds toward the interior of the glass matrix. The morphology of ?-Ca(PO3)2 is a fibrillar shape 20 to 180 nm in length and 17 to 20 nm in diameter, with an aspect ratio ranging from 1.0 to 10.6.

Wang, Moo-Chin; Lai, You-Cheng; Shih, Wei-Jen; Shih, Ping-Yu; Chen, Guo-Ju; Li, Wang-Long

2010-02-01

5

The effects of K2O on the compositions of near-solidus melts of garnet peridotite at 3 GPa and the origin of basalts from enriched mantle  

NASA Astrophysics Data System (ADS)

Enrichment in K2O in oceanic island basalts (OIB) is correlated with high SiO2, low CaO/Al2O3, and radiogenic isotopic signatures indicative of enriched mantle sources (EM1 and EM2). These are also chemical characteristics of the petit-spot lavas, which are highly enriched in K2O (3-4 wt%) compared to other primitive oceanic basalts. We present experimentally derived liquids with varying concentrations of K2O in equilibrium with a garnet lherzolite residue at 3 GPa to test the hypothesis that the major element characteristics of EM-type basalts are related to their enrichment in K2O. SiO2 is known to increase with K2O at pressures less than 3 GPa, but it was previously unknown if this effect was significant at the high pressures associated with partial melting at the base of the lithosphere. We find that at 3 GPa for each 1 wt% increase in the K2O content of a garnet lherzolite saturated melt, SiO2 increases by 0.5 wt% and CaO decreases by 0.5 wt%. MgO and KD^{{{{Fe}} - {{Mg}}}} each decrease slightly with K2O concentration, as do Na2O and Cr2O3. The effect of K2O alone is not strong enough to account for the SiO2 and CaO signatures associated with high-K2O OIB. The SiO2, CaO, and K2O concentrations of experimentally derived partial melts presented here resemble those of petit-spot lavas, but the Al2O3 concentrations from the experimental melts are greater. Partitioning of K2O between peridotite and melt suggests that petit spots, previously considered to sample ambient asthenosphere, require a source more enriched in K2O than the MORB source.

Davis, Fred A.; Hirschmann, Marc M.

2013-07-01

6

The effects of K2O on the compositions of near-solidus melts of garnet peridotite at 3 GPa and the origin of basalts from enriched mantle  

NASA Astrophysics Data System (ADS)

Enrichment in K2O in oceanic island basalts (OIB) is correlated with high SiO2, low CaO/Al2O3, and radiogenic isotopic signatures indicative of enriched mantle sources (EM1 and EM2). These are also chemical characteristics of the petit-spot lavas, which are highly enriched in K2O (3-4 wt%) compared to other primitive oceanic basalts. We present experimentally derived liquids with varying concentrations of K2O in equilibrium with a garnet lherzolite residue at 3 GPa to test the hypothesis that the major element characteristics of EM-type basalts are related to their enrichment in K2O. SiO2 is known to increase with K2O at pressures less than 3 GPa, but it was previously unknown if this effect was significant at the high pressures associated with partial melting at the base of the lithosphere. We find that at 3 GPa for each 1 wt% increase in the K2O content of a garnet lherzolite saturated melt, SiO2 increases by ~0.5 wt% and CaO decreases by ~0.5 wt%. MgO and each decrease slightly with K2O concentration, as do Na2O and Cr2O3. The effect of K2O alone is not strong enough to account for the SiO2 and CaO signatures associated with high-K2O OIB. The SiO2, CaO, and K2O concentrations of experimentally derived partial melts presented here resemble those of petit-spot lavas, but the Al2O3 concentrations from the experimental melts are greater. Partitioning of K2O between peridotite and melt suggests that petit spots, previously considered to sample ambient asthenosphere, require a source more enriched in K2O than the MORB source.

Davis, Fred A.; Hirschmann, Marc M.

2013-10-01

7

Highly bioactive P 2O 5–Na 2O–CaO–SiO 2 glass-ceramics  

Microsoft Academic Search

Glasses having a chemical composition between 1Na2O–2CaO–3SiO2 (1N2C3S) and 1.5Na2O–1.5CaO–3SiO2, containing 0, 2, 4 and 6 wt% P2O5, were crystallized to several volume percent through thermal treatments in the range 550–700 °C. These glasses and glass-ceramics were exposed to a simulated body fluid solution (SBF-K9 which is close to human plasma) for several time periods. Fourier transform infrared spectroscopy (FTIR)

Oscar Peitl; Edgar Dutra Zanotto; Larry L. Hench

2001-01-01

8

Structural characterization of Na 2O–CaO–SiO 2 glass ceramics reinforced with electric arc furnace dust  

Microsoft Academic Search

The microstructure of three different compositions of electric arc furnace dust (EAFD) from steel scrap recycling facilities mixed with cheap raw materials (SiO2, Na2O, CaO), treated under the same conditions were examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Wollastonite-type crystals were identified as the major crystalline phases. The initial composition of

I. Tsilika; Ph. Komninou

2007-01-01

9

Thomas Cao  

Center for Drug Evaluation (CDER)

Text Version... Food and Drug Administration Silver Spring, MD 20993 April 5, 2012 Thomas Cao, MD 1435 North Randall Road, Suite #402 Elgin, IL 60123 ... More results from www.fda.gov/downloads/drugs/drugsafety

10

Effects of added oxide and thermal history on Young's modulus of added oxide(s)–Na 2O–SiO 2 glass  

Microsoft Academic Search

Three-point bending method was used to determine the Young's modulus of glasses based on Na2O–SiO2 and containing the following oxides: Al2O3, CaO, TiO2, or ZnO. The determination was carried out both on as-drawn and annealed rods. The experimental results for the elastic modulus show that the Al2O3 glass has the lowest value while the CaO glass has the highest value

Gheorghe Gavriliu

2001-01-01

11

Effects of Na2O on the Thermal Shock Resistance of Aluminosilicate Refractory Ceramics  

Microsoft Academic Search

This report presents the results of an experimental study of the effects of Na2O on the thermal shock resistance (number of cold shock cycles to failure) of aluminosilicate refractory ceramics. The addition of 4–6% mole is shown to improve the thermal shock resistance, which is characterized by the number of shock cycles to failure. The Na2O changes the viscosity-temperature characteristics,

W. O. Soboyejo; E. T. Akpan; I. B. Bashir; J. Zimba; N. Hosannah; S. Allameh

2007-01-01

12

Glass transition and fragility of Na 2O–TeO 2 glasses  

Microsoft Academic Search

The heat capacity (Cp) change in the glass transition region for the xNa2O·(100?x)TeO2, mol%, glass forming melts with x=7.5, 11.1, 15.0, 20.0 and 25.0 was measured as a function of heating rate (2, 4, 6, 10 and 15 °C\\/min) using differential scanning calorimetry. The glass transition properties that have been measured and reported in this paper include the glass transition

Dongmei Zhu; Chandra S. Ray; Wancheng Zhou; Delbert E. Day

2003-01-01

13

The antibacterial effect of silver-carrying B 2 O 3 ?SiO 2 ?Na 2 O glass material  

Microsoft Academic Search

The antibacterial effect of carrying silver B2O3?SiO2?Na2O glass material was studied by means of antibacterial ring, nephelometery, MIC value, thin film attachment and microcalorimetry,\\u000a respectively. The experimental results of five kinds of antibacterial test methods are almost identical and can verify that\\u000a carrying silver B2O3?SiO2?Na2O glass material exerts an excellent antibacterial performance. Antibacterial ring and nephelometery are simple, quick, but

Xu Ying; Cheng Jinshu; Li Xi; Gao Deqiang; Liu Xiaoming

2005-01-01

14

The nitrogen reaction between carbon saturated Iron and Na2O-SiO2 Slag: Part 1. Thermodynamics  

NASA Astrophysics Data System (ADS)

The nitrogen partition ratio between Na2O-SiO2 slags and carbon saturated iron was measured for slags containing from 0.4 to 0.55 mole fraction of Na2O and the temperature range 1200° to 1350 °C. The nitrogen is dissolved in the slag as the cyanide ion (CN-) and the partition ratio is proportional to the oxygen pressure to the -1/4 power as predicted for CN- dissolution. The oxygen pressure for carbon saturated iron silicon alloys is controlled by the Si (metal)-SiO2 (slag) equilibrium. The nitrogen partition ratio and the cyanide capacity increase with Na2O content and temperature. Calculations indicate that Na2O-SiO2 slags will absorb three times more nitrogen than CaO-Al2O3 slags at the same basicity and temperature. Based on thermodynamic calculations it is estimated that for a typical Na2CO3 hot metal treatment, half of the nitrogen in the metal could possibly be removed.

Tsukihashi, F.; Fruehan, R. J.

1986-09-01

15

Phase Equilibria in The System La2O3–K2O–P2O5  

Microsoft Academic Search

The ternary system La2O3–K2O–P2O5 has been examined by thermal, X-ray, IR and microscopic methods. The existence of three double potassium-lanthanum phosphates,\\u000a K3La(PO4)2, KLa(PO3)4 and K2La(PO3)5 has been confirmed, and the phase diagram of the ternary system La2O3–K2O–P2O5 over the composition range LaPO4–K3PO4–P2O5 has been determined.

W. Jungowska

2000-01-01

16

Compressibility of hydrated and anhydrous Na2O-2SiO2 liquid and also glass to 8 GPa using Brillouin scattering  

Microsoft Academic Search

Brillouin scattering measurements have been carried out on an aqueous solution of Na2O-2SiO2 and anhydrous Na2O-2SiO2 glass and liquid under in situ pressures to 8 GPa in the temperature range from 300 to 850 K. This temperature range spans through the glass transition of both the hydrous and anhydrous forms of Na2O-2SiO2. The ``modified'' platelet scattering geometry has allowed us

Sergey N. Tkachev; Murli H. Manghnani; Quentin Williams; Li Chung Ming

2005-01-01

17

Compressibility of hydrated and anhydrous Na2O-2SiO2 liquid and also glass to 8 GPa using Brillouin scattering  

Microsoft Academic Search

Brillouin scattering measurements have been carried out on an aqueous solution of Na2O-2SiO2 and anhydrous Na2O-2SiO2 glass and liquid under in situ pressures to 8 GPa in the temperature range from 300 to 850 K. This temperature range spans through the glass transition of both the hydrous and anhydrous forms of Na2O-2SiO2. The “modified” platelet scattering geometry has allowed us

Sergey N. Tkachev; Murli H. Manghnani; Quentin Williams; Li Chung Ming

2005-01-01

18

Synthesis and thermochemical characteristics of Na2O · Al2O3 · 2.5H2O  

NASA Astrophysics Data System (ADS)

A pure phase of monosodium aluminate hydrate Na2O · Al2O3 · 2.5H2O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of -100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated.

Grishchenko, R. O.; Emelina, A. L.

2013-01-01

19

Non-Potassic Melts In CMAS-CO2-H2O-K2O Model Peridotite  

NASA Astrophysics Data System (ADS)

Volatile mediated model systems have been fundamental in shaping our knowledge about the way we view melting phase relations of peridotite at various depths in the Earth. Volatiles not only affect the melting temperatures, but the resulting liquids are, in some case, dramatically different than those witnessed in melting of dry peridotite. For example, the influence of CO2 and H2O on the melting phase relations of model peridotite shows a remarkable decrease in the solidus temperatures when compared to the dry peridotite (Gudfinnsson and Presnall, 2005). These model systems illustrate a gradational change above the solidus from carbonatites to kimberlites over several hundreds of degrees. Group-II kimberlites are ultrapotassic rocks with high water content where the mineral phlogopite is abundant. To get a better understanding of the melting phase relations related to carbonatitic and kimberlitic magmas, K2O was added to the system CMAS-CO2-H2O. In these systems, fluid and melt can co-exist in P-T space. However, from past studies, it is also known that in hydrous systems, both the fluid and melt will become indistinguishable from one another creating a singularity (second critical endpoint). Starting from the solidus located in six components (Keshav and Gudfinnsson, AGU abstract, 2009), with seven phases, melting phase relations in CMAS-CO2-H2O-K2O involving, fo-opx-cpx-garnet-carbonate-melt-fluid, are divariant. Fluid was recognized with the observation of large cavities seen in exposed capsules. Moreover, the presence of bright, needle-like grains found in large cavities in backscattered images implies the presence of solute in the fluid phase. Significantly, liquids on this divariant region have about 1000 ppm K2O, and so is the case with accompanying cpx. Hence, with this non-interesting amount of K2O in the mentioned phases, fluid must have all the potassium. At 30 kbar/1100C, with fo-opx-cpx-garnet-carbonate-phlogopite-melt-fluid, the melting phase relations become isobarically invariant. In contrast, the solidus in CMAS-CO2-H2O at 30 kbar is at 1000C. Above 1100C, phlogopite is no longer in equilibrium with the phase assemblage. In all the experimental charges, capsules were pierced, and a hydrous solution was seen escaping. When tested with litmus paper, in all cases at 25-50 kbar, this solution was determined to be highly basic (pH>10). Upon evaporation of the hydrous solution, a white precipitate was left behind around the piercing on the capsule wall. In CMAS-CO2-H2O, the fluid was found to be almost neutral (pH 7-8). The melt present in our experiments is carbonatitic in nature and does not contain any significant amounts of K2O. This contradicts a recent study on K2O in a natural composition (Foley et al, 2009) where carbonatitic melt had up to 13 wt% of K2O. Significantly, since K2O is perhaps all in the fluid, source regions for potassic magmas in the Earth’s mantle could not be created by metasomatism of alkali-rich, carbonatitic melts.

Buisman, I.; Walter, M. J.; Keshav, S.

2009-12-01

20

Thermal Conductivity of Molten Silicate of Al2O3-CaO-Na2O-SiO2 Measured by Means of a Front Heating-Front Detection Laser Flash Method  

NASA Astrophysics Data System (ADS)

Thermal conductivity values have been systematically obtained for molten silicates containing Al2O3, CaO, Na2O, and SiO2 by means of a front heating-front detection laser flash method. The measurements were made for 13 samples in the temperature range between 1073 K and 1823 K (800 °C and 1550 °C), depending on the composition. Thermal conductivities of the silicate melts are found to be relatively insensitive to the variation of temperature, but they depend on the composition ratio, particularly the ratio of Non-Bridging Oxygen ions per Tetrahedrally coordinated cation—NBO/T. The thermal conductivity values decrease from 2.8 W/mK to 1.5 W/mK with the NBO/T value until it reaches about 1. Thermal conductivity values become constant for silicate melts with a higher value of NBO/T. It is known that the length of the silicate chain decreases with disconnection by the addition of alkaline earth cation or alkaline cation. The strong correlation between thermal conductivity and NBO/T is quite likely to suggest that silicate chain is a preferential path for heat transport in silicate melts.

Hasegawa, Hiroki; Kowatari, Takaya; Shiroki, Yasuhiro; Shibata, Hiroyuki; Ohta, Hiromichi; Waseda, Yoshio

2012-12-01

21

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O-Al2O3-SiO2 and Na2O-Fe2O3-Al2O3-SiO2 melts  

NASA Astrophysics Data System (ADS)

The configurational heat capacity, shear modulus and shear viscosity of a series of Na2O-Fe2O3-Al2O3-SiO2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na2O/(Na2O + Al2O3) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz-1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si-O bonds and Na-O bonds in the melt. The lifetime of the Al-O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al-O bonds in these melts is similar to that of Si-O bonds with the Al-O relaxation peak being subsumed by the Si-O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si-O bonds in the Al-poor peralkaline melts, and by the lifetime of Al-O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.

Falenty, Katarzyna; Webb, Sharon L.

2010-10-01

22

Metamorphic evolution of eclogites at Qinglongshan: modeling in system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3  

NASA Astrophysics Data System (ADS)

Eclogite at Qinglongshan in NE Jiangsu province is one of the research objects which are investigated frequently and products are remarkable in ultra-high pressure (UHP) metamorphic petrology and geochemistry nearly twenty years. Though scholars in China and abroad have made abundant petrological work, there are opposite perspectives to some important petrological questions such as peak assemblage, crystalization time and condition of epidote porphyroblasts which contain coesite, peak assemblage contains talc or not, lawsonite has occurred in the rock or not. This paper choose eclogites in Qinglongshan. Besides traditional petrological work, we applied phase diagram modeling to mineral assemblage and chemical composition, quantitatively investigating the change with temperature and pressure. With the help of petrographic observation the petrological questiones can be solved. Eclogites in Qinglongshan can be divided into three categories: porphyroblastic foliated eclogites, granular massive eclogites and banded eclogites. The peak assemblage in three kinds of eclogites is garnet + omphacite + phengite + kyanite +rutile + coesite. The minerals in the peak assemblage show shape preferred orientation defining the rock foliation in porphyroblastic eclogites. The peak assemblage defined by garnet compositional isopleths in the calculated phase diagram is garnet +omphacite + phengite + kyanite + rutile + coesite + lawsonite + talc in porphyroblastic eclogites, and is garnet + omphacite + phengite + kyanite + rutile +coesite + lawsonite in banded eclogites, both inconsistent with the petrographic observation. This discrepancy probably resulted from the assumption of pure water as the ultrahigh-pressure (UHP) fluid phase. Three stages of metamorphism are established for Qinglongshan eclogites. Prograde inclusions such as amphibole, epidote, plagioclase, chlorite, muscovite, paragonite and albite coexist in the area of < 0.8GPa and < 575. It can infer from mineral assemblage that peak temperature and pressure are higher than 710 and 2.9GPa in porphyroblastic eclogites and >620 and 2.9GPa in banded eclogites. Both petrography and phase diagram modelling demonstrate a crystallization sequence of kyanite-epidote-talc, with the first two having begun to crystallize at UHP condition and hence including coesite. The mode of epidote increases dramatically at < 2 GPa resulting in the formation of large porphyroblasts. The randomly oriented porphyroblasts overprint the rock foliation, implying that they crystallized later than the peak assemblage under a weak shear stress field. Kyanite begun to crystallize at early retrogression in banded eclogites. Epidote begun to develop at low pressure, so there is no coesite in banded eclogites. Symplectite is the product of late retrograde metamorphism. The P-T paths of porphyroblastic eclogites and banded eclogites defined by the mineral assemblages are both typically the hair-pin type. The amounts of hydrous minerals increased during retrogression, implying continuous ingress of fluids into the rock.

Yan, R.; Yang, J.; Zhang, Z.

2011-12-01

23

Does six-coordinate germanium exist in Na 2O–GeO 2 glasses? Oxygen17 nuclear magnetic resonance measurements  

Microsoft Academic Search

Sodium germanate glasses of compositions Na2O·9GeO2 and 2Na2O·9GeO2 have been studied using solid-state 17O nuclear magnetic resonance (NMR). Quartz-type and rutile-type GeO2 were used as examples of oxygen connected to 4-fold and 6-fold coordinated germanium. The 17O spectra yielded nuclear quadrupole coupling constants, (e2qQ\\/h), asymmetry parameters, (?), and isotropic chemical shifts, (?i), from line shape simulations. The chemical shifts of

R. Hussin; D Holland; R Dupree

1998-01-01

24

The effect of oxidation state on the viscosity of melts in the system Na2O-FeO-Fe2O3SiO2  

Microsoft Academic Search

The viscosities of two melts in the system Na2o-Feo_Fe203s~ have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with CO\\/COr gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts. \\

DONALD B. DINGWELL; D VIRGO

1987-01-01

25

Phosphate capacity of CaO-AI2O3 slags containing CaF2, BaO, Li2O, or Na2O  

NASA Astrophysics Data System (ADS)

Phosphorus partition ratios between CaO-Al2O3 and CaO-Al2O3-CaF2 fluxes and Fe-Csat-P alloys have been measured as a function of slag composition at 1500 °C. The effects of additions of BaO, Li2O, and Na2O to the CaO-Al2O3-CaF2 system on the phosphorus partition ratios at 1400 °C and 1300 °C have been measured. From the partition ratio, and assuming that the oxygen potential is controlled by C-CO equilibrium, the phosphate capacities of the fluxes were calculated. Also, the activities of Li2O and Na2O were measured as a function of slag composition at 1300 °C by equilibrating the flux and the metal with Pb-Li or Pb-Na alloy and CO in a graphite crucible. The results indicate that phosphorus partition ratios with carbon-saturated iron and the phosphate capacities for additions of more basic oxides decrease in the following order: Na2O?;Li2O?;BaO. The activities of Li2O and Na2O in calcium aluminate fluxes have large negative deviations from ideal behavior; the activity coefficients at infinite dilution are on the order of 0.05 and 10-5, respectively.

Nassaralla, C.; Fruehan, R. J.

1992-03-01

26

Optical investigation in UV region for undoped and Ni doped (80-x)Sb2O3-20K2O-xMoO3 gla  

NASA Astrophysics Data System (ADS)

We have analyzed the Ni influence on the absorption spectra of new ternary systems Sb2O3-K2O-MoO3 in the Urbach's rule region at room temperature. Glasses have been synthesized by using classical routes (melting-casting) in the glass composition (80-x)Sb2O3-20K2O-xMoO3 (x=30, 40 mol%) doped with 0.1 mol% NiO. The parameters of electron-phonon interaction and Urbach's energy are investigated. The constants of Urbach's rule and the dynamic disorder in the glasses are calculated following the experimental data. Their values are compared also.

Petkova, P.; Houhou, S.; Soltani, M. T.

2012-09-01

27

Crystallization and microstructure of glasses in the system Na 2O\\/MnO\\/SiO 2\\/Fe 2O 3  

Microsoft Academic Search

Glasses with the compositions (100?x)(0.16Na2O\\/0.10MnO\\/0.74SiO2)\\/xFe2O3, (x=5–30) and 16Na2O\\/10MnO\\/(74?y)SiO2\\/yFe2O3 (y=5–30) were studied using X-ray diffraction and scanning electron microscopy. The effect of the chemical composition and the thermal history on the phase formation and the resulting microstructure was investigated. During cooling, the precipitation of ferrimagnetic solid solutions Fe3O4\\/Mn3O4 was observed. These crystals show dendritic or platelet shape, whereby the platelets are

Ruzha Harizanova; Günter Völksch; Christian Rüssel

28

Glass forming region and physical properties in the system P 2O 5Na 2O–Fe 2O 3  

Microsoft Academic Search

The glass forming region of the system P2O5–Na2O–Fe2O3 was determined, using phosphate salts as precursor materials. The glasses were produced in non-wetting gold\\/platinum crucibles in order to avoid contamination. Glass formation was confirmed using XRD and the final composition determined using EDX. The glass forming region was found to be relatively short at 50% P2O5 content in comparison to both

A. J. Parsons; C. D. Rudd

2008-01-01

29

The effect of oxidation state on the viscosity of melts in the system Na 2 O-FeO-Fe 2 O 3 SiO 2  

Microsoft Academic Search

The viscosities of two melts in the system Na 2 O-FeO-Fe 2 O 3 -SiO 2 have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with CO \\/ CO 2 gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts.

Donald B. Dingwell; David Virgo

1987-01-01

30

Effect of Na2O and B2O3 on the Crystallization Behavior of Low Fluorine Mold Fluxes for Casting Medium Carbon Steels  

NASA Astrophysics Data System (ADS)

An investigation has been conducted to study the effect of Na2O and B2O3 on the crystallization behavior of low fluorine (F) mold powders for casting medium carbon (MC) steels in this article. The results of this study indicated that B2O3 tends to lower the crystallization temperature and increase crystallization incubation time of the low F powders; however, Na2O plays an opposite role compared with that of B2O3. The crystalline phase of Ca11Si4B2O22 was formed in Sample D2 [F = 3 pct, Na2O = 10 pct, B2O3 = 8 pct (in wt pct)], which exhibited the most similar crystallization behavior to that of cuspidine, such that Sample D2 showed closest crystallization kinetics to that of a conventional high-F mold slag for casting MC steels. The precipitated crystalline phases for all the samples have been analyzed and discussed in the article.

Wei, Juan; Wang, Wanlin; Zhou, Lejun; Huang, Daoyuan; Zhao, Huan; Ma, Fanjun

2013-10-01

31

Optical properties of transparent glass-ceramics in K 2O?Nb 2O 5?TeO 2 glasses  

Microsoft Academic Search

Transparent glass-ceramics consisting of a cubic crystalline phase with crystallites having diameters between 20 and 40 nm in the composition of 15K2O?15Nb2O5?70TeO2 (mol%) have been fabricated. A phase with cubic structure is formed by post-heat-treatment at around 390°C for 1 h and transforms into a stable phase at temperatures above 450°C. The glass-ceramics consisting of a stable crystalline phase are

Kazuhide Shioya; Takayuki Komatsu; Hyun Gyu Kim; Ryuji Sato; Kazumasa Matusita

1995-01-01

32

Organic reagents for removing heavy metals from a 10-34-0 (NP 2 O 5 -K 2 O) grade fertilizer solution and wet-process phosphoric acid  

Microsoft Academic Search

Fertilizer solutions and wet-process phosphoric acid (WPA) contain heavy metal impurities such as cadmium, zinc, lead, copper, manganese, and chromium. Trisodium trithiocyanuric acid (TMT-15), sodium trithiocarbonate (5% Na2CS3), and sodium polythiocarbonate (Thio-Red II) were evaluated as precipitating agents for heavy metals in a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and WPA. A water-insoluble starch xanthate was also evaluated as an adsorbent

V. M. Norwood; J. J. Kohler

1990-01-01

33

CAOS: Code for Adaptive Optics Systems  

NASA Astrophysics Data System (ADS)

The CAOS "system" (where CAOS stands for Code for Adaptive Optics Systems) is properly said a Problem Solving Environment (PSE). It is essentially composed of a graphical programming interface (the CAOS Application Builder) which can load different packages (set of modules). Current publicly distributed packages are the Software Package CAOS (the original adaptive optics package), the Software Package AIRY (an image-reconstruction-oriented package - AIRY stands for Astronomical Image Restoration with interferometrY), the Software Package PAOLAC (a simple CAOS interface for the analytic IDL code PAOLA developed by Laurent Jolissaint - PAOLAC stands for PAOLA within Caos), and a couple of private packages (not publicly distributed but restricted to the corresponding consortia): SPHERE (especially developed for the VLT planet finder SPHERE), and AIRY-LN (a specialized version of AIRY for the LBT instrument LINC-NIRVANA). Another package is also being developed: MAOS (that stands for Multiconjugate Adaptive Optics Simulations), developed for multi-reference multiconjugate AO studies purpose but still in a beta-version form.

Carbillet, M.; Verinaud, C.; Femenia, B.; Riccardi, A.; Fini, L.

2011-06-01

34

Na 2 O-SiO 2 wood-inorganic composites prepared by the sol-gel process and their fire-resistant properties  

Microsoft Academic Search

For enhancing fire-resistant properties, a binary system to prepare wood-inorganic composites was studied by adding sodium\\u000a methoxide (SM) or sodium acetate (SA) to a reaction system for SiO2 composites. Compared with the SiO2 composites, both the Na2O-SiO2 composites prepared could be greatly improved up to 600°C-700°C (glowing). From scanning electron microscopic observations,\\u000a this enhanced fire resistance was assumed to be

Hisashi Miyafuji; Shiro Saka

2001-01-01

35

Partitioning of Na between olivine and melt: An experimental study with application to the formation of meteoritic Na 2O-rich chondrule glass and refractory forsterite grains  

Microsoft Academic Search

We report experimentally determined 1atm olivine\\/melt DNa partitioning data for low fO2, a variety of melt compositions and a temperature range of 1325–1522°C. We demonstrated that high-current electron microprobe analyses (EPMA, I=500nA, 600s on the peak) allow quantitative determination of Na2O in olivine down to ?10?g\\/g. The mean olivine\\/melt DNa from 12 experimental runs is 0.0031±0.0007 (1?). This is the

Alexander Borisov; Andreas Pack; Andreas Kropf; Herbert Palme

2008-01-01

36

FER zeolite crystallized in THF–Na 2O–SiO 2–Al 2O 3–H 2O reactant system containing catalytic amount of organic additives  

Microsoft Academic Search

Pure-phase FER zeolite was hydrothermally synthesized in the reactant system of Na2O–SiO2–Al2O3–H2O with tetrahydrofuran (THF) as the template in the presence of catalytic amount of glycerol [CH2(OH)CH(OH)CH2(OH), GC] or OP emulsion agent [C8H17–C6H5–O–(CH2CH2O)10OH, OP] in the temperature range of 413–473K. Powder X-ray diffraction (XRD) was used to observe the crystallization products, and scanning electron microscope (SEM), 13C cross polarization (CP)

Xiao-wei Cheng; Jing Wang; Juan Guo; He-yong He; Ying-cai Long

2009-01-01

37

Physical, optical and structural properties of xNa2O-(50-x)Bi2O3-10ZnO-40B2O3 glasses  

NASA Astrophysics Data System (ADS)

Glasses with composition xNa2O-(50-x)Bi2O3-10ZnO-40B2O3 with 0 <= x<= 20 have been synthesized by conventional melt quench method. Density and molar volume decreases with increase in Na2O content. The optical absorption studies revealed that the cutoff wavelength decreases and optical band gap (Eopt) increases with increase in Na2O content and the present glass system shows indirect allowed transitions. The IR studies indicate that these glasses are made up of [BiO3] [BiO6], [BO3] and [BO4] basic structural units. Na2O acts a network modifier and modify the glass structure.

Dahiya, Sajjan; Maan, A. S.; Punia, R.; Kundu, R. S.; Murugavel, S.

2013-02-01

38

Influence of the composition of a molten salt on the field-assisted diffusion of potassium ions in the 20Na 2 O · 80SiO 2 glass  

Microsoft Academic Search

The kinetics of interaction between the sodium silicate glass 20Na2O · 80SiO2 and molten salts in a dc electric field is investigated using the electron-probe X-ray microanalysis and radioactive-tracer\\u000a technique. The influence of the electric field strength, the temperature, the interaction time, and the composition of a molten\\u000a salt on the concentration distribution of alkali cations in the 20Na2O ·

S. I. Sviridov

2007-01-01

39

FTIR structural investigation of gamma irradiated BaO–Na2O–B2O3–SiO2 glasses  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FT-IR) spectra of xBaO–15Na2O–(70?x)B2O3–15SiO2 glass system with x=0, 5, 10, 15 and 20 (mol%) has been measured in the spectral range 400–4000 cm?1 at room temperature in order to understand the characteristic frequencies of the chemical bonds and bonding mechanisms, which are susceptible to the structural and spectral changes. The effect of gamma irradiation in the dose range 0.1 kGy–60 kGy on the infrared absorption spectra of these glasses is also reported. The change in the glass structure due to the effect of composition is also discussed. It has been observed that irradiation of the glasses with the gamma rays increases the BO3 groups and the non bridging oxygens which make the network loose.

Kaur, Ravneet; Singh, Surinder; Pandey, Om Prakash

2012-12-01

40

Properties and Structure of RO-R2O-Na2O-Al2O3-P2O5 Glasses  

SciTech Connect

The properties and structural features of RO-R2O-Na 2O-Al2O3-P2O5 (R= Mg, Ca, Ba and RO= Li) glasses in the system have been investigated. The properties of those glasses seem to depend on the field strength of the alkali or alkali-earth ions in glasses as in silicate glasses. Infrared (IR) spectroscopy indicates that the glass network is dominated by bridging P-tetrahedral present in glasses with O/P {approx_equal} 3.0. The variation in physical properties of the glasses seem to be closely related to the variation in structure of the glasses and could be explained by simple mechanism such as field strength and differences in mass.

Agus Setyo Budi; Ahmad, Asmala [Jabatan Sains and Math, Pusat Perkhidmatan Akademik, Kolej Universiti Teknikal Kebangsaan Malaysia, 75450 Ayerkeroh, Melaka (Malaysia); Safarudin Gazali Herawan [Faculty of Mechanical Engineering, Kolej Universiti Teknikal Kebangsaan Malaysia, 75450 Ayerkeroh, Melaka (Malaysia); Sunaryo [Physics Dept.-Faculty of Science, State University of Jakarta, Jakarta 13320 (Indonesia)

2007-05-09

41

Accurate Procedure for Calibrating the CAO Optical Hygrometer.  

National Technical Information Service (NTIS)

Two hygrometers of the Central Aerological Observatory (CAO) (Russia) were calibrated with respect to the partial pressure of water vapor. Optical hygrometers from the CAO are designed for measuring water vapor at heights above 10 km. They use the fluores...

J. Gumbel U. Waelchli M. Kretova

1992-01-01

42

Phosphate glasses for tissue engineering: Part 1. Processing and characterisation of a ternary-based P 2O 5–CaO–Na 2O glass system  

Microsoft Academic Search

This paper presents the results of a study of the thermal properties, X-ray powder diffraction (XRPD), NMR and solubility of a range of phosphate-based glasses. Ion release and pH measurements were also obtained. The compositions were limited by fixing the P2O5 mol% content at 45, 50 and 55mol%, and varying the CaO mol% at 30, 35 and 40mol%. Initial data

I. Ahmed; M. Lewis; I. Olsen; J. C. Knowles

2004-01-01

43

Role of B2O3 on the Viscosity and Structure in the CaO-Al2O3-Na2O-Based System  

NASA Astrophysics Data System (ADS)

The effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied. An increase in the B2O3 content at fixed CaO/Al2O3 ratio lowered the viscosity. Higher CaO/Al2O3 ratio at fixed B2O3 content also decreased the viscosity. The alumino-borate structures were confirmed through Fourier transformed infrared (FTIR) and Raman spectroscopy and consisted of [AlO4]-tetrahedral structural units, [BO3]-triangular structural units, and [BO4]-tetrahedral structural units, which could be correlated to the viscosity. At fixed CaO/Al2O3 ratio, B2O3 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-D network structures such as pentaborate and tetraborate into 2-D network structures of boroxol and boroxyl rings by breaking the bridged oxygen atoms (O0) to produce non-bridged oxygen atoms (O-) leading to a decrease in the molten flux viscosity. At fixed B2O3 contents and higher CaO/Al2O3 ratio, 3-D complex network structures become 3-D simple and 2-D isolated network structures, resulting in lower viscosities. The apparent activation energy for viscous flow varied from 132 to 249 kJ/mol according to the composition of B2O3 and CaO/Al2O3 ratio.

Kim, Gi Hyun; Sohn, Il

2013-10-01

44

The effect of oxidation state on the viscosity of melts in the system Na 2O-FeO-Fe 2O 3-SiO 2  

NASA Astrophysics Data System (ADS)

The viscosities of two melts in the system Na 2O-FeO-Fe 2O 3-SiO 2 have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with CO/CO 2 gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts. 57Fe Mössbauer spectra were obtained on quenched melt samples recovered during the viscometry experiments. In addition, a series of loop fusion experiments were performed at calibrated ƒO 2 values in order to relate viscosity determinations directly to ƒO 2. The viscosities of acmite and NS4F40 (Na-rich and Si-poor relative to acmite) melts decrease with reduction of Fe in the melts, as nonlinear functions of Fe 3+/?Fe, yielding a region of viscosity invariance at moderate to low values of Fe 3+/?Fe (<0.4). The 57Fe Mössbauer spectra of quenched melts as a function of Fe 3+/?Fe indicate the presence of one (network-modifying) ferrous species and two ferric species with ferric iron acting dominantly as a network-former in oxidized melts and dominantly as a network-modifier in reduced melts. The presence of two ferric iron species produces a minimum in the degree of polymerization of the melt at intermediate values of Fe 3+/?Fe: the region of viscosity invariance corresponds to this minimum. If viscosity is positively correlated with polymerization for all values of Fe 3+/?Fe then the viscosity of very reduced melts will increase with reduction, as the melt polymerizes. The effect of oxidation state on viscosity is large and illustrates that ferric iron should be considered as a separate component in calculation schemes for estimating the viscosity of natural magmas.

Dingwell, Donald B.; Virgo, David

1987-02-01

45

The Effect of Chlorine on the Rheology of Na2O-Fe2O3-Al2O3-SiO2 Melts  

NASA Astrophysics Data System (ADS)

Because of the high fluid mobility of chlorine, the mantle wedge in subduction zone settings may be enriched in chlorine by the fluids released by the subducted altered oceanic crust plus sediments. The presence of chlorine (and other halogens) will affect the solidus temperature and the rheology of melts, thus influencing the magma evolution, eruption and degassing. Very little is known about the solubility mechanism and diffusivity of Cl in silicate melts and even less is known about the effect of Cl on viscosity. The present study addresses the effect of the halogen chlorine on the viscosity of silicate melts. The shear viscosities of Cl-bearing melts in the system Na2O-Fe2O3-Al2O3-SiO2 were determined over the temperature range 550-950C at room pressure in air. Viscosities were determined using the micropenetration technique in the range of 108.5 to 1012.0 Pa s. The compositions are based on addition of Fe2O3 or FeCl3 to aluminosilicate glasses with a fixed amount of SiO2 (67 mol %). Although there was loss of Cl- during the glass syntheses, no loss occurred during the viscometry experiments. It is to be expected that Cl- takes the structural position of an oxygen, and thus reduces the polymerization of the melt structure, and therefore the viscosity of the melt; as F- does. Our measurements show that, depending upon the melt composition, the addition of Cl- will either increase or decrease the viscosity of the melt. In the present melts at least 20% of the iron exists as network modifying, viscosity reducing Fe2+; while the rest exists as network forming Fe3+. It is proposed here that the different effects of chlorine on viscosity are due to the preferred Cl--Fe2+NBO bonding together with the different structure of peralkaline and peraluminous melts. In peralkaline aluminosilicate melts, the addition of Cl2O-1 will destroy 2 NBOs and create one BO if Cl- bonds primarily to the Fe2+ creating non-bridging oxygens. This would result in an increase in viscosity. In peraluminous melts, the addition of Cl2O-1 may result in Cl- bonds to the charge-balancing Fe2+, creating 2 new tri-clusters (assuming (Al3+, Fe3+)Si2O5 tri-clusters exist). The viscosity should then decrease due to the weaker bonds of the charge balancing Fe2+-Cl- units. The preference of Cl- to form bonds to the NBO-forming Fe2+ is indicated by the small amount of Cl- soluble in the peraluminous melt structure in comparison to that soluble in the peralkaline structure.

Zimova, M.; Webb, S.

2004-12-01

46

Antimicrobial activity of caO nanoparticles.  

PubMed

The high degree of microbial diseases and their multidrug resistant properties make the researchers to develop new class of antimicrobial agents. A modern and innovative approach of drug development is the use of metallic nanoparticles as new formulations of antimicrobial agents. In this study, microwave irradiated CaO nanoparticles (CaO-NPs) were used to determine their antimicrobial efficacy against gram negative and gram positive bacteria, as well as pathogenic yeast. The physiochemical properties of CaO-NPs were characterized by means of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The nanoparticles consist of well dispersed agglomerates of grains with a narrow size distribution of 14-24 nm. The prepared CaO-NPs showed much higher antimicrobial activity against Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus epidermidis (MTCC 435) in comparision to Candida tropicalis (NCIM 3110). The minimum inhibitory concentration (MIC) value of CaO-NPs was found within the range of 2-8 mM for all the above tested strains. This bioactive nanoparticle also inhibits the biofilm formation and may have future applications cheap and non toxic as antimicrobial drug for skin care product development. PMID:23980504

Roy, Arup; Gauri, Samiran S; Bhattacharya, Madhusmita; Bhattacharya, Jayanta

2013-09-01

47

Production and properties of high purity TeO 2–ZnO–Na 2O–Bi 2O 3 and TeO 2–WO 3–La 2O 3–MoO 3 glasses  

Microsoft Academic Search

High-purity TeO2–ZnO–Na2O–Bi2O3 and TeO2–WO3–La2O3–MoO3 glasses were produced by melting the high-purity oxides mixtures in platinum or gold crucible at 800°C in hermetic chamber in the purified oxygen atmosphere. The content of limiting impurities in the produced initial oxides and glasses, the optical properties as well as the stability to crystallization were investigated. The optical fibers were produced from high-purity tellurite

A. N. Moiseev; V. V. Dorofeev; A. V. Chilyasov; I. A. Kraev; M. F. Churbanov; T. V. Kotereva; V. G. Pimenov; G. E. Snopatin; A. A. Pushkin; V. V. Gerasimenko; A. F. Kosolapov; V. G. Plotnichenko; E. M. Dianov

2011-01-01

48

Correlation between etch pits formed by molten KOH+Na2O2 etching and dislocation types in heavily doped n+-4H-SiC studied by X-ray topography  

NASA Astrophysics Data System (ADS)

X-ray topography (XRT) has been carried out to examine the accuracy of KOH+Na2O2 etching (KN etching) technique which was recently developed for identifying dislocation types in n+-4H-SiC (n>1019 cm-3). Precise one-to-one correlation have been found between the position of etch pits and dislocations revealed by XRT. More importantly, XRT observation has also confirmed the validity of using the pit sizes formed by KN etching to distinguish threading screw dislocations from threading edge dislocations.

Yao, Yongzhao; Ishikawa, Yukari; Sugawara, Yoshihiro; Sato, Koji; Danno, Katsunori; Suzuki, Hiroshi; Bessho, Takeshi; Yamaguchi, Satoshi; Nishikawa, Koichi

2013-02-01

49

Effect of Fe 2O 3 concentration on the structure of the SiO 2–Na 2O–Al 2O 3–B 2O 3 glass system  

Microsoft Academic Search

The structural properties of the glass matrix 40SiO2·30Na2O·1Al2O3·(29?x)B2O3·xFe2O3 (mol%), 0.0?x?29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe3O4 crystal formation for Fe2O3 concentrations of 29.0mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe2O3 concentration and that these alterations were related to structural change

Noelio O. Dantas; Walter E. F. Ayta; Anielle C. A. Silva; Nilo F. Cano; Sebastião W. Silva; Paulo C. Morais

2011-01-01

50

The CAOS problem-solving environment: recent developments  

NASA Astrophysics Data System (ADS)

We present recent developments of the CAOS problem-solving environment (PSE), an IDL-based software tool whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system -from the atmospheric propagation of light, to the sensing of the wave-front aberrations and the correction through a deformable mirror- but which results in a widely more general tool now. In fact, the different developments made through the last years result in a very versatile numerical tool complete of a global graphical interface (the CAOS Application Builder), a general utilities library (the CAOS Library), and different packages dedicated to a wide range of astronomical-optics-related scientific topics: the original package designed for end-to-end AO system simulations (the Software Package CAOS), an image simulation/ reconstruction package with interferometric capabilities (the Software Package AIRY), an extension of the latter specialized for the LBT instrument LINC-NIRVANA (the Software Package AIRY-LN), an ad hoc package dedicated to the VLT instrument SPHERE (the Software Package SPHERE), and an embedment of the analytical AO simulation code PAOLA (the Software Package PAOLAC).We present the status of the whole CAOS PSE, together with the most recent developments, and plans for the future of the overall tool.

Carbillet, Marcel; Desiderà, Gabriele; Augier, Evelyne; La Camera, Andrea; Riccardi, Armando; Boccaletti, Anthony; Jolissaint, Laurent; Ab Kabir, Diyana

2010-07-01

51

Structural and optical properties of 60B2O3-(20-x)Na2O-10PbO-10Al2O3:xTiO2:yNd2O3 glasses  

NASA Astrophysics Data System (ADS)

In this work we investigate the effect of replacing Na2O by TiO2 on the structural and spectroscopic characteristics of the Nd2O3-doped 60B2O3-(20-x)Na2O-10PbO-10Al2O3:xTiO2:yNd2O3 borate glass matrix. Measurements of X-ray patterns, glass temperatures (Tg), vibrational (Raman and infrared (IR)) and optical (absorption and emission) spectra were carried out. The trend of Tg, the Judd-Ofelt parameters and Nephelauxetic ratio as the TiO2 and Nd2O3 concentration increases was interpreted quantitatively and qualitatively in terms of the network bonds and coordination numbers. Measurements of Tg across the Nd-doped glass series for different levels of Ti suggests changes in the rigidity of the matrix due to change of coordination of boron oxide resulting from the BO4-BO3 back conversion effect. The changes observed in the Raman and IR spectra are related to the BO3 ? BO4 conversion effect. The variation of the Judd-Ofelt parameters ? and ? indicates that the average rare earth-ligand radius decreases establishing an electronic density distribution when Nd3+ concentration increases. This effect is interpreted in terms of Judd-Ofelt parameters and by the bonding parameter b due to Nephelauxetic effect.

de Souza, N. C. A.; Santos, C. C.; Guedes, I.; Dantas, N. O.; Vermelho, M. V. D.

2013-10-01

52

Synthesis and properties of glasses in the K 2 O–SiO 2 –Bi 2 O 3 –TiO 2 system and bismuth titanate (Bi 4 Ti 3 O 12 ) nano glass–ceramics thereof  

Microsoft Academic Search

Glasses were prepared by the melt-quench technique in the K2O–SiO2–Bi2O3–TiO2 (KSBT) system and crystallized bismuth titanate, BiT (Bi4Ti3O12) phase in it by controlled heat-treatment at various temperature and duration. Different physical, thermal, optical, and\\u000a third-order susceptibility (?3) of the glasses were evaluated and correlated with their composition. Systematic increase in refractive index (n) and ?3 with increase in BiT content

Atiar Rahaman Molla; Anal Tarafder; Basudeb Karmakar

2011-01-01

53

Effects of Sm3+\\/Yb3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO2 GeO2 K2O Sm2O3\\/Yb2O3] glasses  

Microsoft Academic Search

Effects of Sm3+\\/Yb3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 °C and the structure of two glass systems of the composition (80TeO2 10GeO2 8K2O 2Sm2O3\\/Yb2O3) is discussed. It was found that the addition of Yb3+ to the glass very strongly enhances the intensities of the antistokes' Raman bands at 155, 375, 557

I. Shaltout; Y. Badr

2006-01-01

54

Geochemistry of shales from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: Implications for provenance and source-area weathering  

Microsoft Academic Search

Phyllites from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe, were deposited on a stable cratonic platform. Analyses of the phyllites generally define a single geochemical group based on major-and trace-element abundances. The phyllites are strongly depleted in CaO, Na2O, and Sr with respect to average Archean upper crust. By contrast, K2O, Ba, and Rb are enriched several times relative

Christopher M. Fedo; Kenneth A. Eriksson; Eirik J. Krogstad

1996-01-01

55

Alteration of basaltic glass: Mechanisms and significance for the oceanic crust-seawater budget  

Microsoft Academic Search

Alteration of basaltic glass to palagonite is characterized by a nearly isomolar exchange of SiO 2 , Al 2 O 3 , MnO, MgO, CaO, Na 2 O, P 2 O 5 , Zn, Cu, Ni, Cr, Hf, Sc, Co and REE for H 2 O and K 2 O, whilst TiO 2 and FeO are passively accumulated during removal

Hubert Staudigel; Stanley R. Hart

1983-01-01

56

A-type granites: geochemical characteristics, discrimination and petrogenesis  

Microsoft Academic Search

New analyses of 131 samples of A-type (alkaline or anorogenic) granites substantiate previously recognized chemical features, namely high SiO2, Na2O+K2O, Fe\\/Mg, Ga\\/Al, Zr, Nb, Ga, Y and Ce, and low CaO and Sr. Good discrimination can be obtained between A-type granites and most orogenic granites (M-, I and S-types) on plots employing Ga\\/Al, various major element ratios and Y, Ce,

Joseph B. Whalen; Kenneth L. Currie; Bruce W. Chappell

1987-01-01

57

Fluid compositions in equilibrium with silica-undersaturated magmas in the system Na2O-Al2O3-SiO2-H2O: clues to the composition of fenitizing fluids  

NASA Astrophysics Data System (ADS)

Fenites result from alkali metasomatism of granitoid rocks associated with the intrusion of silica-undersaturated alkaline magmas, and are characterized by addition of alkalis, iron and magnesium, albitization, nephelinization, removal of silica and the formation of alkali pyroxenes and amphiboles. In an attempt to constrain the fluid compositions involved in this process, we have investigated the compositions of the fluids in equilibrium with a range silica-undersaturated alkaline magmas, in the model system Al2O3-Na2O-SiO2-H2O at 850 °C and 1 kbar. The starting compositions straddle the nepheline-albite join, and include both peralkaline and alkali-granitoid compositions. The quenched run products all contained a glass, representing the melt, as well as an aqueous fluid and a radial crystalline phase interpreted to be a fluid quench phase. Several of the glasses also contained albite, nepheline or quartz crystals. Fluid compositions in crystal-free experiments were calculated using a mass-balance approach that incorporated the composition of the glass, composition of starting materials and carefully determined masses of the different run product fractions, as well as that of the starting materials. Compositions plotting to the peralkaline side of the nepheline-albite join produced fluids that were highly enriched in dissolved solids (SiO2 + Al2O3 + Na2O, in the range 40-50 wt%). This substantial fractionation of the solid starting materials, between melt and fluid phase, results in reasonable resolution of the fluid compositions produced, despite significant uncertainties in the measured Na2O and H2O concentrations in the glasses. Model calculations indicate that the fluid compositions in equilibrium with the more SiO2 undersaturated melt compositions in this study are capable of converting a typical granodiorite to a nepheline syenite composition at fluid/rock ratios lower than 1:1. Albitization and the removal of quartz (in the form of soluble sodium metasilicate), formation of sodic pyroxenes (acmite) and ultimately nepheline are characteristic of the process modeled here. These are largely analogous to the general features observed in some natural fenites.

Preston, Robin; Stevens, Gary; McCarthy, Terence

2002-11-01

58

Un caos perfecto: El cine de Emir Kusturica  

Microsoft Academic Search

Desentrañar la vida de este cineasta, capaz de conv ertir el caos en perfección, es una tortura exquisita sólo para quien tenga en el c uerpo una sobredosis de él suficiente como para soportarla. Aunque su nombre ya está inserto en la historia del séptimo arte como el director que más premios ha ganado en el Festival de Cannes, el

Evelyn ERLIJ

59

XPS Study of CaO in Sodium Silicate Glass.  

National Technical Information Service (NTIS)

This paper shows that CaO added to silicate glasses behaves much like Na sub 2 O in converting bridging oxygen sites to nonbridging sites. Good correspondence with model predictions was obtained but deviations were still sufficiently large to warrant atte...

B. W. Veal D. J. Lam A. P. Paulikas W. Y. Ching

1981-01-01

60

INVESTIGATION OF PRODUCT-LAYER DIFFUSIVITY FOR CAO SULFATION  

EPA Science Inventory

The paper gives results of comparisons of the sulfation rates of CaO prepared from Ca(OH)2 and CaCO3, using six types of each precursor derived from the same natural limestones. The particles were small enough to eliminate all transport resistances except diffusion through the Ca...

61

Synthesis, bioactivity and preliminary biocompatibility studies of glasses in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2.  

PubMed

New compositions of bioactive glasses are proposed in the CaO-MgO-SiO(2)-Na(2)O-P(2)O(5)-CaF(2) system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO(4)) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts' cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C). PMID:21188484

Tulyaganov, D U; Agathopoulos, S; Valerio, P; Balamurugan, A; Saranti, A; Karakassides, M A; Ferreira, J M F

2010-12-29

62

Subsolidus phase relations in Na2O CuO Sb2On system and crystal structure of new sodium copper antimonate Na3Cu2SbO6  

Microsoft Academic Search

Subsolidus phase relation studies in the NaSb3O7 Na3SbO4 CuO CuSb2O6 quadrangle of Na2O CuO Sb2On system at 1123 1173 K revealed the formation of one new compound Na3Cu2SbO6. It is a superstructure derived from alpha-NaFeO2 type, space group C2\\/m, lattice constants: a=5.6759(1) Å, b=8.8659(1) Å, c=5.8379(1) Å, beta=113.289(1)°. All ions are in octahedral environment, but CuO6 polyhedron exhibits strong elongation

O. A. Smirnova; V. B. Nalbandyan; A. A. Petrenko; M. Avdeev

2005-01-01

63

Subsolidus phase relations in Na2O CuO Sb2On system and crystal structure of new sodium copper antimonate Na3Cu2SbO6  

NASA Astrophysics Data System (ADS)

Subsolidus phase relation studies in the NaSb3O7 Na3SbO4 CuO CuSb2O6 quadrangle of Na2O CuO Sb2On system at 1123 1173 K revealed the formation of one new compound Na3Cu2SbO6. It is a superstructure derived from ?-NaFeO2 type, space group C2/m, lattice constants: a=5.6759(1) Å, b=8.8659(1) Å, c=5.8379(1) Å, ?=113.289(1)°. All ions are in octahedral environment, but CuO6 polyhedron exhibits strong elongation due to Jahn Teller effect (Cu O: 2.000(2) Å×2, 2.021(2) Å×2, 2.494(3) Å×2), whereas SbO6 octahedron is almost regular. The relationship to other similar superlattices is discussed.

Smirnova, O. A.; Nalbandyan, V. B.; Petrenko, A. A.; Avdeev, M.

2005-04-01

64

Subsolidus phase relations in Na 2O–CuO–Sb 2O n system and crystal structure of new sodium copper antimonate Na 3Cu 2SbO 6  

Microsoft Academic Search

Subsolidus phase relation studies in the NaSb3O7–Na3SbO4–CuO–CuSb2O6 quadrangle of Na2O–CuO–Sb2On system at 1123–1173K revealed the formation of one new compound Na3Cu2SbO6. It is a superstructure derived from ?-NaFeO2 type, space group C2\\/m, lattice constants: a=5.6759(1)Å, b=8.8659(1)Å, c=5.8379(1)Å, ?=113.289(1)°. All ions are in octahedral environment, but CuO6 polyhedron exhibits strong elongation due to Jahn–Teller effect (Cu–O: 2.000(2)Å×2, 2.021(2)Å×2, 2.494(3)Å×2), whereas SbO6

O. A. Smirnova; V. B. Nalbandyan; A. A. Petrenko; M. Avdeev

2005-01-01

65

Mixed alkali effect and optical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 glasses.  

PubMed

Optical and physical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5?x?25) glasses are carried out at room temperature. Powder XRD pattern of all the glass samples confirms the amorphous nature. Several physical parameters are evaluated for all the glasses with respect to the composition. The optical absorption spectra confirm the site symmetry of the Ni2+ doped glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. It is interesting to observe that the optical band gap and Urbach energies exhibit the mixed alkali effect. The FT-IR spectral investigations of Ni2+ doped glasses exhibit characteristic vibrations of BO3 and BO4 units. PMID:21652259

Rao, T Raghavendra; Krishna, Ch Rama; Reddy, Ch Venkata; Thampy, U S Udayachandran; Reddy, Y P; Rao, P S; Ravikumar, R V S S N

2011-05-11

66

The Investigation on the Carbonation of CaO in FBC  

Microsoft Academic Search

Limestone is usually be used as a sorbent for capture of sulphur dioxide, but, almost half of CaO will not reacted with SO2 in FBC. So, when the fly ash that contains CaO cools to bellow the calcination temperature, carbonation of CaO in fly ash that deposited on cool surfaces may occur. In this study, CaO was carbonated in a

Chunbo Wang; Guang Lu; Chunchang Song

2010-01-01

67

First-principle investigations of CaO (1 0 0) surface and adsorption of H 2O on CaO (1 0 0)  

Microsoft Academic Search

The results of first-principles calculations about (100) surface of CaO and adsorption of water molecules on the CaO (100) have been presented. Both surface parameters (atomic structures and electronic configurations) and adsorption parameters (bond, charge and energy) of H2O on CaO (100) surface are obtained using density functional theory calculations with the generalized gradient approximation (DFT–GGA). It is found that

Wei Dai; Zhong-He Shui; Kai Li

2011-01-01

68

Production and properties of high purity TeO2-ZnO-Na2O-Bi2O3 and TeO2-WO3-La2O3-MoO3 glasses  

NASA Astrophysics Data System (ADS)

High-purity TeO2-ZnO-Na2O-Bi2O3 and TeO2-WO3-La2O3-MoO3 glasses were produced by melting the high-purity oxides mixtures in platinum or gold crucible at 800 °C in hermetic chamber in the purified oxygen atmosphere. The content of limiting impurities in the produced initial oxides and glasses, the optical properties as well as the stability to crystallization were investigated. The optical fibers were produced from high-purity tellurite glasses with losses at the level of several hundreds of dB/km.The total content of 3d-transition metals in the glasses was not more than 1 ppm wt and content of hydroxyl groups corresponded to the absorption level of 0.001-0.002 cm-1 at ˜3 ?m. The absorption band, monotonically increasing with the increase in MoO3 content, was observed in dry TeO2-WO3-La2O3-MoO3 glasses with the maximum at about 3.7 ?m.

Moiseev, A. N.; Dorofeev, V. V.; Chilyasov, A. V.; Kraev, I. A.; Churbanov, M. F.; Kotereva, T. V.; Pimenov, V. G.; Snopatin, G. E.; Pushkin, A. A.; Gerasimenko, V. V.; Kosolapov, A. F.; Plotnichenko, V. G.; Dianov, E. M.

2011-10-01

69

The Oxygenase CAO-1 of Neurospora crassa Is a Resveratrol Cleavage Enzyme.  

PubMed

The genome of the ascomycete Neurospora crassa encodes CAO-1 and CAO-2, two members of the carotenoid cleavage oxygenase family that target double bonds in different substrates. Previous studies demonstrated the role of CAO-2 in cleaving the C40 carotene torulene, a key step in the synthesis of the C35 apocarotenoid pigment neurosporaxanthin. In this work, we investigated the activity of CAO-1, assuming that it may provide retinal, the chromophore of the NOP-1 rhodopsin, by cleaving ?-carotene. For this purpose, we tested CAO-1 activity with carotenoid substrates that were, however, not converted. In contrast and consistent with its sequence similarity to family members that act on stilbenes, CAO-1 cleaved the interphenyl C?-C? double bond of resveratrol and its derivative piceatannol. CAO-1 did not convert five other similar stilbenes, indicating a requirement for a minimal number of unmodified hydroxyl groups in the stilbene background. Confirming its biological function in converting stilbenes, adding resveratrol led to a pronounced increase in cao-1 mRNA levels, while light, a key regulator of carotenoid metabolism, did not alter them. Targeted ?cao-1 mutants were not impaired by the presence of resveratrol, a phytoalexin active against different fungi, which did not significantly affect the growth and development of wild-type Neurospora. However, under partial sorbose toxicity, the ?cao-1 colonies exhibited faster radial growth than control strains in the presence of resveratrol, suggesting a moderate toxic effect of resveratrol cleavage products. PMID:23893079

Díaz-Sánchez, Violeta; F Estrada, Alejandro; Limón, M Carmen; Al-Babili, Salim; Avalos, Javier

2013-07-26

70

Mixed alkali effect in Mn2+ doped 20ZnO+xLi2O+(30-x)K2O+50B2O3(5?x?25) glasses.  

PubMed

Divalent Mn2+ ions containing 20ZnO+xLi2O+(30-x)K2O+50B2O3(5?x?25) mol% glasses are prepared by using melt quench technique and are characterized by several spectroscopic techniques. Various physical parameters are evaluated from the measured values of density and refractive index for the observation of mixed alkali effect. Structural changes of Mn2+ doped ZLKB glasses are investigated by Powder XRD, UV-VIS absorption, Electron Paramagnetic Resonance and FT-IR spectroscopic studies. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of all glasses revealed that the network structure of glass system are mainly based on BO3 and BO4 units placed in different structural groups in which the BO3 units being dominant. The EPR spectra of Mn2+ ions doped glasses exhibited a characteristic hyperfine sextet around g=2.0. The spectroscopic analyses of the obtained results confirmed near octahedral site symmetry for the Mn2+ impurity ions. Crystal field and Racah parameters are evaluated from optical absorption spectra. The optical band gap and Urbach energies are determined which exhibited the mixed alkali effect. PMID:23099172

Kumari, G Krishna; Krishna, Ch Rama; Begum, Sk Muntaz; Manjari, V Pushpa; Murthy, P N; Ravikumar, R V S S N

2012-10-02

71

Optical characterization of Mn2+: Li2O-K2O-CdO-B2O3 glass system: Absorption edge, optical band gap, optical polarizability and optical basicity  

NASA Astrophysics Data System (ADS)

Mixed alkali borate glasses (30-x)Li2O-xK2O-10CdO-59B2O3 (0 <= × <= 30) implanted with 1mol% manganese ions (LKCBM) were prepared from the melts. These glasses were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density measurements. Optical absorption studies were carried out as a function of alkali content to look for `Mixed Alkali Effect' (MAE) on the spectral properties of these glasses. The optical absorption spectra of LKCBM exhibit a broad band around 21000 cm-1 which has been assigned to the transition 6A1g(S) ? 4T1g(G). From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion (?o2-), Optical basicity (wedge) and Yamasita-Kurosawas's interaction parameter (A) were also evaluated for all the glasses. In the present investigation many of the physical parameters like glass transition temperature, density, optical band gap and optical basicity vary non-linearly with alkali concentration (x) indicating MAE.

Padmaja, G.; Kistaiah, P.

2009-07-01

72

Studies on some ternary oxyborates of the Na2O Me2O3 B2O3 (Me=rare earth or aluminum) systems: Synthesis, structure and crystal growth  

NASA Astrophysics Data System (ADS)

Sodium rare-earth oxyborates Na2RE2O(BO3)2 (RE=Y, Nd, Er) were prepared for the first time in the present study. They were found to be isostructural with phases of the same composition containing Sm, Eu or Gd and reported by Corbel et al. [J. Solid State Chem.144 (1999) 35 44]. It was shown that the yttrium and erbium compounds could be synthesized at 900 1000 °C by a solid-state reaction between oxides in an equimolecular ratio. With both oxyborates melting led to decomposition into a mixture of Y(Er)BO3, Y2(Er2)O3 and Na2B4O7. Just the opposite was observed during thermal treatment of the oxide mixture containing Nd2O3, from which a practically pure phase of Na2Nd2O(BO3)2 was only obtained after melting. The attempts to synthesize the oxyborate Na2La2O(BO3)2 showed it to be unstable, this leading to the formation of a mixture containing, in addition to Na2La2O(BO3)2, also other already known stable phases of the system Na2O La2O3 B2O3 along with an unknown ternary oxide phase. This phase was found to represent a new oxyborate of sodium and lanthanum with the formula Na3La9O3(BO3)8, whose single crystals were obtained by flux growth. It was established that synthesis of a polycrystalline material with the same composition was also possible using solid-state interaction between Na2CO3, La2O3 and H3BO3 at 1000 1100 °C. X-ray diffraction experiments on single crystals were used to solve the structure of Na3La9O3(BO3)8. The unit cell was found to be hexagonal, space group P62m (No. 189) with Z=1. The compound can be regarded as the forefather of a second group of oxyborates representing a new family of isostructural compounds, Na3RE9O3(BO3)8. Such phases were obtained with RE=Nd, Sm and Eu whereas with RE=Y and Gd, the synthesis experiments failed. The concentration and temperature regions of crystallization of the double-oxyborate Na2Al2O(BO3)2 in the ternary system Na2O Al2O3 B2O3 were determined. This compound was shown to melt incongruently at 970±3 °C, which made high-temperature solution growth most appropriate for obtaining its single crystals with NaBO2 as the best solvent. On the basis of the data obtained, a composition of the initial solution was proposed, the validity of the choice being demonstrated by the growth of Na2Al2O(BO3)2 single crystals on a seed using the top-seeded solution growth (TSSG) technique and slow cooling of the solution.

Peshev, P.; Pechev, S.; Nikolov, V.; Gravereau, P.; Chaminade, J.-P.; Binev, D.; Ivanova, D.

2006-09-01

73

Effect of Bi2O3 addition on electron paramagnetic resonance, optical absorption, and conductivity in vanadyl-doped Li2O-K2O-Bi2O3-B2O3 glasses.  

PubMed

Glasses with composition 15Li(2)O-15K(2)O-xBi(2)O(3)-(65 - x)-B(2)O(3)/5V(2)O(5) (3 ? x ? 15) have been prepared by the conventional melt quench technique. The electron paramagnetic resonance spectra of VO(2+) in these glasses have been recorded in the X-band frequency (?9.3 GHz) at room temperature. The spin Hamiltonian parameters and covalency rates were evaluated. It was found that the V(4+) ions exist as vanadyl (VO(2+)) ions and are in an octahedral coordination with a tetragonal compression. The covalency rates (1 - ?(2)) and (1 - ?(2)) indicate moderate covalency for the ?- and ?-bonds. It was observed that the spin-Hamiltonian parameters depend slightly on the relative concentration of Bi(2)O(3). The optical properties of this glass system are studied from the optical absorption spectra recorded in the wavelength range 200-800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap for indirect allowed transitions have been determined using available theories. The direct current electrical conductivity, ?, has been measured in the temperature range 373-573 K. The conductivity decreases with the increase in Bi(2)O(3) concentration. This has been discussed in terms of the decrease in the number of mobile ions and their mobility. An attempt is made to correlate the EPR, optical, and electrical results and to find the effect of Bi(2)O(3) content on these parameters. PMID:21247083

Subhadra, M; Kistaiah, P

2011-01-19

74

In vitro cellular adhesion and antimicrobial property of SiO2-MgO-Al2O3-K2O-B2O3-F glass ceramic.  

PubMed

The aim of the present study was to examine the cellular functionality and antimicrobial properties of SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics (GC) containing fluorophlogopite as major crystalline phase. The cellular morphology and cell adhesion study using human osteoblast-like Saos-2 cells and mouse fibroblast L929 cells reveals good in vitro cytocompatibility of GC. The potential use of the GC for biomedical application was also assessed by in vitro synthesis of the alkaline phosphatase (ALP) activity of Saos-2 cells. It is proposed that B(2)O(3) actively enhances the cell adhesion and supports osteoconduction process, whereas, fluorine component significantly influences cell viability. The Saos-2 and L929 cells on GC shows extensive multidirectional network of actin cytoskeleton. The in vitro results of this study illustrate how small variation in fluorine and boron in base glass composition influences significantly the biocompatibility and antimicrobial bactericidal property, as evaluated using a range of biochemical assays. Importantly, it shows that the cell viability and osteoconduction can be promoted in glass ceramics with lower fluorine content. The underlying reasons for difference in biological properties are analyzed and reported. It is suggested that oriented crystalline morphology in the lowest fluorine containing glass ceramic enhanced cellular spreading. Overall, the in vitro cell adhesion, cell flattening, cytocompatibility and antimicrobial study of the three different compositions of glass ceramic clearly reveals that microstructure and base glass composition play an important role in enhancing the cellular functionality and antimicrobial property. PMID:19936888

Kalmodia, Sushma; Molla, Atiar Rahaman; Basu, Bikramjit

2009-11-20

75

COMPARATIVE SO2 REACTIVITY OF CAO DERIVED FROM CACO3 AND CA(OH)2  

EPA Science Inventory

Experimental data on sulfation rates of CaO particles derived from CaCO3 are compared to those derived from Ca(OH)2 using a product layer diffusion control model differing only in the shape of the CaO grain. Both the model and the experimental data indicate slightly higher reacti...

76

COMPARATIVE SO2 REATIVITY OF CAO DERIVED FROM CACO3 AND CA(OH)2  

EPA Science Inventory

The paper gives results of a Comparison of experimental data on sulfation rates of CaO particles derived from CaC03 with those derived from Ca(OH)2 using a product layer diffusion control model differing only in the shape of the Cao grain. Both the model and the experimental data...

77

Interdiffusion in NiO, CaO, AND MgO Single Crystals.  

National Technical Information Service (NTIS)

Citation interdiffusion was investigated in single crystals of NiO, CaO, and MgO in the temperature range 1300C-1700C. The excess cation vacancies present in NiO in air cause diffusion to proceed more rapidly in NiO than in either CaO or MgO. This in turn...

M. Appel

1968-01-01

78

Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses  

NASA Astrophysics Data System (ADS)

Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0?x?7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (×10-20 cm2: ?2=4.49±0.84, ?4=5.03±0.61, ?6=4.31±0.73), the radiative transition probabilities (AT), radiative lifetimes (?R), fluorescence branching ratios (?) and emission cross-sections (?em) were calculated for the 4F3/2?4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The ?R value of the 4F3/2 level amount to 164 ?s and is slightly higher than the measured decay time of 162 ?s. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 ?s. The estimated quantum efficiency amount to 100%, based on a comparison of ?R and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2?4I9/2 and 4F5/2?4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2?4I9/2 and 4G5/2?4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm laser host as well as an optical sensor for temperature measurements.

Sobczyk, Marcin

2013-04-01

79

Effects of Sm3+/Yb3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO2 GeO2 K2O Sm2O3/Yb2O3] glasses  

NASA Astrophysics Data System (ADS)

Effects of Sm3+/Yb3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 °C and the structure of two glass systems of the composition (80TeO2 10GeO2 8K2O 2Sm2O3/Yb2O3) is discussed. It was found that the addition of Yb3+ to the glass very strongly enhances the intensities of the antistokes’ Raman bands at 155, 375, 557 and 828 cm-1 and quenches both the intensities of the stokes’ vibration modes of the TeO4 units in the range of 120 770 cm-1 and the intensities of the OH- stretching vibration modes in the range of 2600 3300 cm-1. Sm2O3/Yb2O3 rare earth co-doping has a great influence on removing and/or changing the nature of the OH- groups. The appearance and splitting of the stretching vibration modes of the OH- groups at lower frequencies (2770, 2970 cm-1) for the Sm+3 singly doped glass sample, compared to the band at ˜3200 cm-1 for the Sm3+/Yb3+ co-doped glass sample, suggested that the OH- groups are more strongly bonded and incorporated with the glass matrix for the singly doped glass. Heating the sample up continuously weakens the hydrogen bonding of the OH- groups to the glass matrix leading to creation of NBO and breakdown of the connectivity of the OH- groups to the TeO4, TeO3+1 and TeO3 structural units. Raman bands at 286, 477, 666 and 769 cm-1 were assigned to its respective vibrations of Te2O7, TeO4-4 species, the (Te O Te)bending vibrations of the TeO4 triagonal bipyramids (tbps), the axial symmetric stretching vibration modes (Teax O)s with bridging oxygen BO atoms and to the (Te O)nbo non-bridging stretching vibration modes of the TeO3+1 and/or TeO3 pyramids.

Shaltout, I.; Badr, Y.

2006-05-01

80

Theoretical Study of the Rovibronic States of CaO  

NASA Astrophysics Data System (ADS)

The spin-rovibronic energy levels of CaO, which result from the couplings of X1?+, a3?, A?1?, b3?+, and A1?+ low-lying electronic states, are determined from wave packet time propagations and Prony analysis. The electronic potentials were taken from our previous study [Chem. Phys., 386, 50 (2011)]. The spin-orbit and L^ coupling functions were determined by CASSCF and MRCI calculations. The effects of spin-orbit coupling on vibrational levels were analyzed in the ? = 0+, 0-, 1 coupling schemes. All spin-vibronic energy levels associated with the a3?, A?1?, b3?+, and A1?+ states were determined up to 16 000 cm-1 above the electronic ground-state minimum. The results obtained from the spin-orbit coupling functions are in remarkable agreement with the experimental data extracted using a deperturbation procedure. The final energies calculated for J = 2 and J = 25 are used to compare the experimental observations concerning the X1?+-A1?+ transition.

Khalil, H.; Le Quéré, F.; Brites, V.; Léonard, C.

2012-01-01

81

THE INFLUENCE OF CaO REACIVITY ON FORMATION OF LOW-BASE CALCIUM SILICATE HYDRATES  

Microsoft Academic Search

The influence of CaO reactivity on the calcium sili cate hydrates formation in the CaO - SiO 2?nH 2O - H 2O system when molar CaO\\/SiO 2 ratio equal to 0.83 and 1.0 was determined. It was identified that in pure CaO - SiO 2?nH 2O - H 2O system with CaO\\/SiO 2 = 0.83, C-S-H(I) is rather stable and

K. Baltakys; E. PRICHOCKIENE

2010-01-01

82

CaO interaction in the staged combustion of coal  

SciTech Connect

The LIMB (limestone injection multi-stage burner) process offers special potential for reducing NO/sub x/ and SO/sub x/ by at least 50 percent in coal combustion. This is to be accomplished by adding limestone with fuel and/or air in a low NO/sub x/ burner. This program has been directed to defining the chemistry and kinetics necessary to optimize sulfur capture in LIMB combustion. More specifically, this program has attempted to clarify the role of calcium sulfide in LIMB chemistry. When limestone is added in a staged burner, there is a strong possibility that under certain circumstances CaS is produced in the reducing (fuel-rich) zone of the burner. Since CaS is more stable than CaSO/sub 4/, this affords the opportunity to (1) operate the burner at a higher temperature, 2200 to 2500 F, (2) pass the CaS rapidly through the high temperature zone (before dissociation), and (3) complete the combustion in a lean (air-rich) region where the sulfur is finally retained in CaSO/sub 4/. For these reasons this program has concentrated on the high temperature chemistry and kinetics of CaS. To achieve the program objective, the program was divided into three tasks. These involved (1) a study of CaS formation, (2) a brief examination of CaS oxidation, and (3) a laboratory examination of the combustion of coal in the presence of CaO under first stage, fuel-rich conditions. In the most general sense, the study has shown that the formation of CaS in the reducing zones of the burner may be restricted by competing kinetics and thermodynamics. The addition of lime in LIMB will require special care to optimize the ability to capture sulfur. 36 references, 44 figures, 10 tables.

Levy, A.; Merryman, E.L.; Rising, B.W.

1983-12-19

83

Variations in Compressive Strength of Geopolymer due to the CaO Added Fly Ash  

NASA Astrophysics Data System (ADS)

Recently, geopolymer has been a noteworthy material which can be used as a replacement for portland cement. The mechanical characteristics and consistency of the geopolymer are strongly affected by its chemical components of fly ash. The variations in compressive strength of geopolymer due to the CaO added fly ash were investigated in this paper. The compressive strengths of geopolymer were increased with an increase in the curing period, and the characteristics changed from the one of plastic soil material to brittle material such as concrete, regardless of CaO content. Also, the results of compressive strength and modulus of deformation showed their maximum value in the case of 8-10% CaO content. From this result, the maximum characteristics of the strengths were assumed to be exerted in case which the water draining process of geopolymer was balanced with the water absorbing process of additional CaO.

Zhao, Yuqing; Koumoto, Tatsuya; Kondo, Fumiyoshi

84

Measurement of secondary ionization coefficient of CaO film electrode  

NASA Astrophysics Data System (ADS)

The secondary ionization coefficient ? of a CaO film electrode is investigated taking into account the difference in breakdown voltage obtained by repeated voltage applications. Such measurement is performed under a sinusoidal voltage of 0.5 Hz. If the CaO film electrode acts as the cathode, breakdown voltage gradually decreases and converges to an almost constant value after several breakdowns. From the obtained results, the ? of the CaO film electrode is determined for each breakdown using Townsend's criterion. The ? in the first breakdown is lower than those in subsequent breakdowns, particularly in the steady state. The difference in ? is considered to originate from accumulated charges on the CaO film electrode. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Suzuki, Susumu; Kashiwagi, Yasuhide; Itoh, Haruo

2013-02-01

85

Assessment of CAOS as a training model in spinal surgery: a randomised study  

Microsoft Academic Search

The objectives of this study were (1) to quantify the benefit of computer assisted orthopaedic surgery (CAOS) pedicle screw\\u000a insertion in a porcine cadaver model evaluated by dissection and computed tomography (CT); (2) to compare the effect on performance\\u000a of four surgeons with no experience of CAOS, and varying experience of pedicle screw insertion; (3) to see if CT with

P. J. Richards; I. C. Kurta; V. Jasani; C. H. Wynn Jones; A. Rahmatalla; G. MacKenzie; J. Dove

2007-01-01

86

Removal of Fluoride from Aqueous Solution by CaO Nanoparticles  

Microsoft Academic Search

Colloidal particles of CaO were synthesized by the sol-gel method. The particle morphology was characterized by FT-IR, TGA, DTA, and TEM analysis. The ability of the CaO nanoparticles for removal of fluoride from aqueous solution through adsorption has been investigated. All the experiments were carried out by batch mode. The effect of various parameters viz. contact time, pH effect (pH

Gaurang Patel; Usha Pal; Shobhana Menon

2009-01-01

87

Influence of CaO on damping capacity and mechanical properties of Mg alloy  

Microsoft Academic Search

For developing cost effective damping Mg alloys with high damping capacity and better mechanical properties, the microstructures, the mechanical properties at room temperature and the damping capacity of Mg alloy adding CaO were investigated and compared with those of K1A alloy. CaO adding into pure Mg maintains the damping capacity and increases the ultimate tensile strength compared with those of

Dong-In JANG; Jin-Kyu LEE; Dae-Up KIM; Shae-K KIM

2009-01-01

88

Catalytic reduction of nitric oxide by methane over CaO catalyst  

Microsoft Academic Search

The selective catalytic reduction of nitric oxide by methane was studied over CaO catalyst in a bubbling fluidized bed in\\u000a the temperature range of 800–900 °C, in which NO cannot be reduced by CH4 without CaO catalyst. The nitric oxide conversion was found to depend on oxygen and CH4 feed concentration, and also on temperature. In addition, the presence of

Wei Xu; Huiling Tong; Changhe Chen; Xuchang Xu

2008-01-01

89

Bactericidal effects of CaO (scallop-shell powder) on foodborne pathogenic bacteria.  

PubMed

This study was investigated the bactericidal effects of calcium oxide (CaO) on three common foodborne pathogenic bacteria: Escherichia coli, Listeria monocytogenes, and Salmonella typhimurium. Each bacteria level was determined in a CaO solution (0.01, 0.03, 0.05, 0.10, 0.15, and 0.20% [w/v]) exposed for either 15 sec, 30 sec, 1 min, 2 min, 3 min, 5 min, 10 min, or 30 min. All three bacteria were not greatly affected by CaO solutions at concentrations of 0.01 and 0.03%, however, the decline of E. coli (99%; 2.78 log10 CFU/mL), L. monocytogens (45%; 1.44 log10 CFU/mL), and S. typhimurium (70%; 2.08 log10 CFU/mL) was greatest when they were exposed to 0.05% CaO solution for 10 min. Moreover, the bactericidal action of CaO was maintained for at least 24 h of storage. The results of this study provide evidence that CaO, as a substitute for synthetic chemical substances has potential for use in the disinfection and sanitization of foods and food processing equipment. PMID:16681035

Bae, Dong-Ho; Yeon, Ji-Hye; Park, Shin-Young; Lee, Dong-Ha; Ha, Sang-Do

2006-04-01

90

Thermal analysis of binary mixtures of CaO, CaO 2 , Ca(OH) 2 , and Mg(OH) 2 with sodium and potassium perchlorates  

Microsoft Academic Search

The catalytic activity of magnesium oxide, calcium oxide, and calcium peroxide in reactions of dioxygen evolution from sodium and potassium perchlorates has been studied. Additives of CaO facilitate the complete decomposition of perchlorates within the same temperature range as that found for additives of Mn, Co, Ni, and Cu oxides. Tile data oil the low catalytic activity of calcium oxide

V. V. Klyucharev; M. Sinel'nikov; A. P. Razumova; V. D. Sasnovskaya

1996-01-01

91

Phosphate base laser glasses  

SciTech Connect

A phosphate base laser glass comprising 55-70% P2O5, 1-15% Al2O3, 0-25% Li2O, 0-25% Na2O, 0-8% K2O, the total proportion of Li2O, Na2O, and K2O being 10-25%, 0-15% BaO, 0-15% ZnO, 0-15% CaO , 0-15%, sro, 0-15% MgO, the total proportion of BaO, ZnO, CaO, SrO, and MgO being 5-15%, 0-5% Y2O3, 0-5% La2O3, 0-5% GeO2, 0-5% CeO2, 0-3% Nb2O5, 0-3% MnO2, 0-2% Ta2O5, 0-1% Sb2O3, and 0.01-5% Nd2O3, all % being mole %. The phosphate base laser glass of this invention has a high induced emission cross section, a low non-linear refractive index coefficient, and excellent acid resistance and divitrification resistance. By replacing partially or wholely one or more of LiO2, Na2O, K2O, BaO, ZnO, CaO, SrO, MgO or Al2O3 by LiF, NaF, KF , BaF2ZnF2, CaF2, SrF2, MgF2 or AlF3, respectively, the above properties of the laser glass are further improved.

Izumitani, T.; Tsuru, M.

1980-12-16

92

Influence of alkali and alkali-earth metal oxide substitutions on the properties of lithium–iron–phosphate glasses  

Microsoft Academic Search

The influences of different alkali and alkali-earth oxide substitutions on the properties of lithium–iron–phosphate (LIP) glasses have been studied. Na2O, K2O, MgO, CaO and BaO were used to substitute Li2O to prepare LIP glasses with molar compositions of (20?x)Li2O?xR2O(RO)?30Fe2O3?50P2O5 (x=2.4, 4, 5.6 and 7.2). The glass transition temperature (Tg) was determined by the differential thermal analysis technique. The density and

Ruijuan Yang; Yinghui Wang; Xiaopeng Hao; Jie Zhan; Shiquan Liu

2011-01-01

93

Komposisi Unsur-Unsur Utama dan Logam Berat dalam Tanih di Sekitar Bukit Batu Kapur di Perlis (Major Elements and Heavy Metal Composition of Soils Surrounding Limestone Hills in Perlis)  

Microsoft Academic Search

ABSTRAK Sebanyak 16 sampel tanih atas dari Bukit Jernih, Gua Kelam dan Bukit Merah telah dianalisis bagi menentukan komposisi unsur utama dan logam berat serta beberapa sifat fiziko-kimianya. Unsur-unsur utama yang ditentukan adalah SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5, manakala logam berat ialah As, Co, Cu, Cr, Ni, Pb dan Zn. Sifat fiziko-kimia yang ditentukan adalah

MUHD BARZANI GASIM; WAN MOHD RAZI IDRIS; MOHAMAD M. D. TAN

94

Rapid simultaneous multi-element determination of soils and environmental samples with polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry using pressed powder pellets  

Microsoft Academic Search

A rapid simultaneous multi-element analysis method for soils and environmental samples has been established using polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry. The pressed powder pellet technique was adopted because it is simple and requires no specialized skills for sample preparation. The analytes examined were: Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3, V, Cr, Co, Ni, Cu,

Hisaya Matsunami; Kenji Matsuda; Shin-ichi Yamasaki; Kazuhiko Kimura; Yasumasa Ogawa; Yoshinori Miura; Isao Yamaji; Noriyoshi Tsuchiya

2010-01-01

95

Kiglapait Geochemistry IV: The Major Elements  

Microsoft Academic Search

The summed bulk composition of the Kiglapait intrusion is SiO 2 47.46 (31). TiO 2 0.81 (20), Al 2 O 3 19.46 (48), Fe 2 O 3 1.91 (46), FeO 9.36 (36), MnO 0.15 (01). MgO 8.04 (21), CaO 9.27 (46). Na 2 O 3.13 (05), K 2 O 0.22 (01), P 2 O 5 , 0.09 (01), and BaO

S. A. Morse

1981-01-01

96

Development of glass-ceramics by sintering and crystallization of fine powders of calcium-magnesium-aluminosilicate glass  

Microsoft Academic Search

Natural raw materials normally used in the ceramic and glass industry were studied for the production of calcium–magnesium–aluminosilicate glass or glass-ceramic materials. Sintering and crystallization processes of fine powders of parent glass with chemical composition (wt.%) 46.00 SiO2, 15.90 Al2O3, 1.20 Fe2O3, 0.42 TiO2, 23.50 CaO, 9.37 MgO, 0.04 Na2O, 0.98 K2O, 1.95 P2O5 and 0.35 CaF2 were studied. Crystallization

D. U. Tulyaganov; M. J. Ribeiro; J. A. Labrincha

2002-01-01

97

[Textual research on the editions of Ben cao fa ming (Invention of Materia Medica)].  

PubMed

The edition of Ben cao fa ming (Invention of Materia Medica) included in Zhong guo ben cao quan shu (The Complete Collection of Traditional Texts on Chinese Materia Medica) is photoprinted from the Ming-dynasty block-printed edition persevered in the Library of China Academy of Chinese Medical Sciences (CACMS), an incomplete one with some parts missing. In addition, there are the Ming-dynasty block-printed edition preserved in the Shanghai Library and Japanese hand-copied edition, both complete ones with full texts. In fact, the Shanghai edition and CACMS edition are the same one, only the text of "the differential classification of ben cao of the Ming Dynasty" are located in different position between them. The Japanese one is hand-copied from the Ming-dynasty block-printed edition. PMID:24135479

Li, Yu-Qing

2013-03-01

98

Dissolution process for ZrO.sub.2 -UO.sub.2 -CaO fuels  

DOEpatents

The present invention provides an improved dissolution process for ZrO.sub.2 -UO.sub.2 -CaO-type pressurized water reactor fuels. The zirconium cladding is dissolved with hydrofluoric acid, immersing the ZrO.sub.2 -UO.sub.2 -CaO fuel wafers in the resulting zirconium-dissolver-product in the dissolver vessel, and nitric acid is added to the dissolver vessel to facilitate dissolution of the uranium from the ZrO.sub.2 -UO.sub.2 -CaO fuel wafers.

Paige, Bernice E. (Idaho Falls, ID)

1976-06-22

99

Correlation effects in MgO and CaO: Cohesive energies and lattice constants  

SciTech Connect

A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using {ital ab} {ital initio} quantum-chemical methods for evaluating individual increments, we obtain {approximately}80{percent} of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1{percent} from experimental values, in the case of MgO and CaO. {copyright} {ital 1996 The American Physical Society.}

Doll, K.; Dolg, M. [Max-Planck-Institut fuer Physik Komplexer Systeme, D-01187 Dresden (Germany); Stoll, H. [Institut fuer Theoretische Chemie, Universitaet Stuttgart, D-70550 Stuttgart (Germany)

1996-11-01

100

Bactericidal effects of CaO (scallop-shell powder) on foodborne pathogenic bacteria  

Microsoft Academic Search

This study was investigated the bactericidal effects of calcium oxide (CaO) on three common foodborne pathogenic bacteria:Escherichia coli, Listeria monocytogenes, andSalmonella typhimurium. Each bacteria level was determined in a CaO solution (0.01, 0.03, 0.05, 0.10, 0.15, and 0.20% [w\\/v]) exposed for either\\u000a 15 sec, 30 sec, 1 min, 2 min, 3 min, 5 min, 10 min, or 30 min. All

Dong-Ho Bae; Ji-Hye Yeon; Shin-Young Park; Dong-Ha Lee; Sang-Do Ha

2006-01-01

101

METHOD FOR VARIATION OF GRAIN SIZE IN STUDIES OF GAS-SOLID REACTIONS INVOLVING CAO  

EPA Science Inventory

The paper describes a method for varying grain size in studies of gas-solid reactions involving CaO. (Note: Introducing grain size as an independent experimental variable should contribute to improved understanding of reactions in porous solids.) Calcining 1 micrometer CaCO3 part...

102

Performance of the first-light adaptive optics system of LBT by means of CAOS simulations  

Microsoft Academic Search

This presentation reports the numerical simulations we have done in order to evaluate the performance of the first-light AO system of LBT. The simulation tool used for this purpose is the Software Package CAOS, applicable for a wide range of AO systems and for which a brief recall of the main features is made. The whole process of atmospheric propagation

Marcel Carbillet; Christophe Vérinaud; Simone Esposito; Armando Riccardi; Alfio Puglisi; Bruno Femenía; Luca Fini

2003-01-01

103

Effect of specific surface area on the reactivity of CaO with SOâ  

Microsoft Academic Search

The rate of reaction of calcined limestone with SOâ and Oâ was measured at conditions that eliminate all resistances not associated with the CaO grain surface. Reactivity increased with the square of the BET surface area when grain size was varied as an experimental parameter. The observed effects of surface area and temperature account for the SOâ capture reported for

R. H. Borgwardt; K. R. Bruce

1986-01-01

104

Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity.  

PubMed

Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol. PMID:22905508

Raja, Pradeep Kumar; Chokkalingam, Anand; Priya, Subramaniam V; Balasubramanian, Veerappan V; Benziger, Mercy R; Aldeyab, Salem S; Jayavell, Ramasamy; Ariga, Katsukiho; Vinu, Ajayan

2012-06-01

105

Investigation of Product-Layer Diffusivity for CaO Sulfation.  

National Technical Information Service (NTIS)

The paper gives results of comparisons of the sulfation rates of CaO prepared from Ca(OH)2 and CaCO3, using six types of each precursor derived from the same natural limestones. The particles were small enough to eliminate all transport resistances except...

R. H. Borgwardt K. R. Bruce J. Blake

1987-01-01

106

Effect of Specific Surface Area on the Reactivity of CaO with SO2.  

National Technical Information Service (NTIS)

The paper discusses results of measuring the rate of reaction of calcined limestone (CaCO3) with sulfur dioxide (SO2) and oxygen (O2) at conditions that eliminate all resistances not associated with the lime (CaO) grain surface. Reactivity increased with ...

R. H. Borgwardt K. R. Bruce

1986-01-01

107

Critical Notice: Tian Yu Cao's “The Conceptual Development of 20th Century Field Theories”  

Microsoft Academic Search

Tian Yu Cao has written a serious and scholarly book covering a great deal of physics. He ranges from classical relativity theory, both special and general, to relativistic quantum …eld theory, including non-Abelian gauge theory, renor- malization theory, and symmetry-breaking, presenting a detailed and very rich picture of the mainstream developments in quantum physics; a remarkable feat. It has, moreover,

Simon Saunders

2003-01-01

108

Postcombustion Capture of CO2 with CaO in a Circulating Fluidized Bed Carbonator  

NASA Astrophysics Data System (ADS)

There is an emerging postcombustion capture technology that uses CaO to capture CO2 from combustion flue gases in a circulating fluidized bed reactor. This paper summarizes recent work conducted at CSIC to understand and develop this technology. The paper includes experimental results at conditions close to those expected in the real system, carried out in continuous mode in a 30kW test facility made up of two interconnected circulating fluidized bed reactors. In one of the reactors, CO2 is captured from the gas phase by the CaO continuously circulating from a calciner. In the second reactor, the CaCO3 formed in the carbonator is regenerated to CaO and CO2 by calcination. Modeling of the system at process level, at reactor level (in particular the CFB carbonator), and at particle level (decay in capture capability of CaO) is also outlined. The work carried out so far confirms that the carbonator reactors can be designed to attain capture efficiencies between 70-90%, operating at fluid dynamic conditions close to those present in circulating fluidized bed combustors.

Alonso, M.; Rodriguez, N.; González, B.; Grasa, G.; Murillo, R.; Abanades, J. C.

109

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice)  

Microsoft Academic Search

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its

Qingying Zhang; Min Ye

2009-01-01

110

EFFECT OF SPECIFIC SURFACE AREA ON THE REACTIVITY OF CAO WITH SO2  

EPA Science Inventory

The paper discusses results of measuring the rate of reaction of calcined limestone (CaCO3) with sulfur dioxide (SO2) and oxygen (O2) at conditions that eliminate all resistances not associated with the lime (CaO) grain surface. Reactivity increased with the square of the Brunaue...

111

Materials compatibility during the chlorination of molten CaCl/sub 2/. CaO salts. [CaCl/sub 2/. CaO salt  

SciTech Connect

As part of our effort to develop a semicontinuous PuO/sub 2/ reduction process, we are investigating promising materials for containing a 900/sup 0/C molten CaCl/sub 2/ . CaO chlorination reaction. We want the material to contain this reaction and to be reusable. We tested candidate materials in a simulated salt (no plutonium) using anhydrous HCl as the chlorinating agent. Data are presented on the performance of 36 metals and alloys, 9 ceramics, and 3 coatings.

Rense, C.E.C.; Fife, K.W.; Bowersox, D.F.; Ferran, M.D.

1987-01-01

112

Use of low CaO unprocessed steel slag in concrete as fine aggregate  

Microsoft Academic Search

Steel slag, which is produced locally in great amounts, has a negative impact on the environment when disposed. Local steel slag has a low CaO content and has no pozzolanic activity.In this research, local unprocessed steel slag is introduced in concrete mixes. Various mixes with compressive strength ranging from 25 to 45MPa are studied. The slag is used as fine

Hisham Qasrawi; Faisal Shalabi; Ibrahim Asi

2009-01-01

113

Development of new CaO based sorbent materials for CO 2 removal at high temperature  

Microsoft Academic Search

This study focuses on developing a CO2 sorbent with high sorption capacity (higher than 6mol\\/kg of sorbent) and long life-time. The target value of the sorption capacity was attained by screening and testing two different microporous CaO precursors, Ca(OH)2 and Ca(CH3COO)2. Between them, calcined calcium acetate showed the highest CO2 uptake ability, 50% increase of the weight of the sorbent

Christina S. Martavaltzi; Angeliki A. Lemonidou

2008-01-01

114

Sintering of calcium oxide (CaO) during CO2 chemisorption: a reactive molecular dynamics study.  

PubMed

Reactive dynamics simulations with the reactive force field (ReaxFF) were performed in NVE ensembles to study the sintering of two solid calcium oxide (CaO) particles with and without CO(2) chemisorption. The simulated sintering conditions included starting adsorption temperatures at 1000 K and 1500 K and particle separation distances of 0.3 and 0.5 nm. The results revealed that the expansion of sorbent particles during CO(2) chemisorption was attributed to the sintering of two CaO-CaO particles. Increasing the adsorption temperature resulted in more particle expansion and sintering. The shorter the distance between two particles, the faster the rate of sintering during CO(2) adsorption. A detailed analysis on atom spatial variations revealed that the sorbent particles with a larger separation distance had a larger CO(2) uptake because of less sintering incurred. The chemisorptions of CO(2) on CaO particles sintered at high adsorption temperatures were also simulated to mimic the process of sorbent regeneration. It was found that regeneration would be more difficult for sintered particles than for fresh particles. In addition, a possible sintering barrier, magnesium oxide (MgO), was introduced to prevent CaO particles from sintering during CO(2) chemisorption. It was found that the MgO particles could reduce the sintering of CaO particles during CO(2) chemisorption. Simulation results from this study provided some guidelines on synthesizing or selecting sorbents with less sintering effect for multiple CO(2) adsorption-regeneration cycles. PMID:22990764

Zhang, Luzheng; Lu, Yongqi; Rostam-Abadi, Massoud

2012-09-18

115

Amorphous CaO · Al 2O 3 fibers by melt extraction  

Microsoft Academic Search

A novel melt extraction technique has been used to produce fine calcium aluminate (CaO · Al2O3) fibers with wheel velocities of 1.5–65 m s?1. The geometry of the fibers depends on the wheel velocity; at speeds < 3 m s?1 uniform diameter fibers were obtained, whereas at higher velocities Rayleigh waves formed on the fibers owing to instability and the

M. Allahverdi; R. A. L. Drew; P. Rudkowska; G. Rudkowski; J. O. Strom-Olsen

1996-01-01

116

Corundum, Rutile, Periclase, and CaO in Ca, Al-Rich Inclusion from Carbonaceous Chondrites  

Microsoft Academic Search

Four calcium, aluminum-rich inclusions from four carbonaceous chondrites-Allende, Acfer 082, Acfer 086, and Acfer 094-were studied by transmission electron microscopy. All inclusions contained at least two of the oxides periclase (MgO), rutile (TiO_2), calcium oxide (CaO), and corundum (Al_2O_3). The oxides (50 to 200 nanometers in size) were found inside and at grain boundaries of the constituent minerals of the

A. Greshake; A. Bischoff; A. Putnis; H. Palme

1996-01-01

117

Full potential photoemission theory: application to MgO and CaO  

Microsoft Academic Search

The full potential photoemission theory is applied for the first time to the alkaline-earth oxides MgO and CaO. This theory is a straightforward generalization of the one-step model of photoemission for the case of anisotropic, space-filling potentials and several atoms per unit cell. It allows the calculation of angle-resolved ultraviolet photoemission (ARUPS) and bremsstrahlung isochromat spectra (ARBIS) from compounds. The

M. Grass; J. Braun; G. Borstel

1995-01-01

118

Production of hydrogen from bio-oil using CaO as a CO 2 sorbent  

Microsoft Academic Search

Steam reforming of bio-oil into transportation-fuel-grade hydrogen using CaO as a CO2 sorbent is modelled using the ASPEN PLUS process simulator. The simulations predict that (1) operating the absorbing (reforming) reactor at 600–850°C and the desorbing (regeneration) reactor at ?800°C and near ambient pressure is optimal; (2) the gas exiting the absorbing reactor contains >95%H2 (dry gas, molar basis) versus

C. M. Kinoshita; S. Q. Turn

2003-01-01

119

Porous carbon material containing CaO for acidic gas capture: Preparation and properties.  

PubMed

A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials. PMID:23743266

Przepiórski, Jacek; Czy?ewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W

2013-04-30

120

Geology, petrology, and geochemistry of a younger granite pluton, central Eastern Desert of Egypt; importance of mixing  

NASA Astrophysics Data System (ADS)

The Younger Granite pluton that is the main subject of study of this work, is a small epizonal pluton in the central part of the Eastern Desert (C.E.D.) of Egypt. This pluton is a representative example of widespread and abundant shallow intrusions emplaced in northern and northeastern Africa in late Precambrian time. The Younger Granite pluton occupies a central position in the Maetiq Dome, a metamorphic core complex. It was emplaced along foliation planes of the country rocks, mainly gneisses and mylonites. This together with other observations indicate that it is a sill. Samples from the Younger Granite pluton are silica rich (77.2-75.3 wt% SiO2), metaluminous to peraluminous rocks (molar Al2O3/(Na2O + K2O + CaO) = 0.98 - 1.09). Whole rock major element abundances of 21 samples show only small variation in SiO2, Al2O3, Na2O and K2O compared to larger variation for the less abundant major elements such as FeO, TiO2, CaO, MnO and MgO and the trace elements Sc, Cr, Co, Rb, Sr, Zr, La, Ce, Nd, Sm, Tb, Yb, Lu, Ta, Th and U.

Sultan, M. I.

121

Micro-narratives in Contemporary Chinese Art: A Case Study of Cao Fei's Pearl River Delta Anti-heroes  

Microsoft Academic Search

This paper investigates the representation of micro-narratives in contemporary Chinese art by examining the multi-layered narratives in Cao Fei's Pearl River Delta Anti-heroes performed at the opening of the 2 Guangzhou Triennial in 2005. I consider Cao's work as a hyper-realistic portrayal of the micro-narratives of the Pearl River Delta region in a mediated form highly influenced by the media,

Silvia Fok

2011-01-01

122

The effect of investment material and ceramming regime on the surface roughness of two castable glass–ceramic materials  

Microsoft Academic Search

Objective: To assess the surface roughness (Ra) of two castable glass–ceramic materials, cast using four different investment materials and employing different ceramming regimes.Methods: Forty discs, each 12mm diameter and 2mm thick were produced from two castable glass–ceramic materials, one a glass ionomer derivative based on 1.5SiO2–1Al2O3–0.53P2O5–1CaO–0.67CaF2 (LG112), the other a fluorcanasite material based on 0.60SiO2–0.05K2O–0.10Na2O–0.15CaO–0.10CaF2 (SG3). The discs were made

A Johnson; R van Noort; P. V Hatton; J. M Walsh

2003-01-01

123

Evolutionary changes in chlorophyllide a oxygenase (CAO) structure contribute to the acquisition of a new light-harvesting complex in micromonas.  

PubMed

Chlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences of CAO among photosynthetic organisms elucidated changes in the domain structures of CAO during evolution. However, the evolutionary relationship between the light-harvesting system and the domain structure of CAO remains unclear. To elucidate this relationship, we investigated the CAO structure and the pigment composition of chlorophyll-protein complexes in the prasinophyte Micromonas. The Micromonas CAO is composed of two genes, MpCAO1 and MpCAO2, that possess Rieske and mononuclear iron-binding motifs, respectively. Only when both genes were introduced into the chlorophyll b-less Arabidopsis mutant (ch1-1) was chlorophyll b accumulated, indicating that cooperation between the two subunits is required to synthesize chlorophyll b. Although Micromonas has a characteristic light-harvesting system in which chlorophyll b is incorporated into the core antennas of reaction centers, chlorophyll b was also incorporated into the core antennas of reaction centers of the Arabidopsis transformants that contained the two Micromonas CAO proteins. Based on these results, we discuss the evolutionary relationship between the structures of CAO and light-harvesting systems. PMID:23677999

Kunugi, Motoshi; Takabayashi, Atsushi; Tanaka, Ayumi

2013-05-15

124

Structure refinement of CaO.6Al2O3  

Microsoft Academic Search

The crystal structure of CaO.6Al2O3 at 294 K was investigated by X-ray diffraction and refined to an R value of 0.025 for 2735 reflections (1492 independent reflections). It belongs to the space group P63\\/mmc with a = 5.5587(1), c = 21.8929(3) Å, V = 585.83(1)Å3, and Z = 2, Dx = 3.79 g\\/cm3, and mu(MoKalpha) = 15.86 cm-1. Three different

A. Utsunomiya; K. Tanaka; H. Morikawa; F. Marumo; H. Kojima

1988-01-01

125

Pressure-induced amorphization in mayenite (12CaO.7Al2O3)  

NASA Astrophysics Data System (ADS)

We report a joint experimental and theoretical study on high pressure structures of nanoporous mayenite (12CaO.7Al2O3). A pressure-induced amorphization was identified at ~13 GPa by in situ high pressure x-ray experiments. The amorphous product can be decompressed to ambient conditions. Ab initio calculations reveal that the anisotropic deformations of empty cages break the crystallographic long-range orders, leading to the formation of high-pressure amorphous state. Furthermore, the deformation routes of empty cages are found fully dependent on their individual locally structural geometry relevant to the distribution of extra-framework oxygen ions.

Zhang, Xinxin; Wang, Yanchao; Wang, Hui; Cui, Qiliang; Wang, Chengxin; Ma, Yanming; Zou, Guangtian

2011-09-01

126

Effect of Bi2O3 content on physical and optical properties of 15Li2O-15K2O-xBi2O3-(65-x) B2O3: 5V2O5 glass system  

NASA Astrophysics Data System (ADS)

Multi-component bismuth borate glasses doped with vanadium ions 15Li2O-15K2O-xBi2O3-(65-x) B2O3: 5V2O5, (x=3, 5, 7, 10, 12 and 15) have been prepared using conventional melt quench technique. Characterization of the prepared glasses has been done using X-ray diffraction, differential scanning calorimetry and density measurements. The effect of Bi2O3 content on the optical properties of the present glass system is studied from the optical absorption spectra recorded in the wavelength range 200-800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap for indirect allowed transitions have been determined using available theories. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions. The density and molar volume studies indicate that Bi2O3 in these glasses is acting partly as network modifier and partly as network former. The variations in the optical band gap energies, density and molar volume with Bi2O3 content have been discussed in terms of changes in the glass structure. Values of the theoretical optical basicity, average crosslink density and the average electronic polarizability are also reported.

Subhadra, M.; Kistaiah, P.

2011-04-01

127

Exciton-driven highly hyperthermal O-atom desorption from nanostructured CaO  

SciTech Connect

We report qualitatively new highly-hyperthermal (HHT) oxygen atom emission from nanostructured CaO excited by 6.4 eV nanosecond laser pulses. The kinetic energy distribution of emitted O-atoms peaks at 0.7 eV, which is over four times greater than previously observed. Excitation of MgO and CaO nanostructures with UV laser pulses is known to result in thermal and hyperthermal emission of oxygen atoms when photons with energies below and above the band gap, respectively, are used. The highly energetic atomic desorption we observe, following bulk excitation, challenges the conventional view that bulk excitation can only induce thermal desorption. Using density functional theory and an embedded cluster method, we propose a mechanism for this HHT feature based on the interaction of surface holes with bulk excitons. These experimental and theoretical results suggest that specific atomic desorption mechanisms in wide-bandgap materials can be controlled by selective electronic excitation of not only the surface but also the bulk of these materials

Sushko, Petr V.; Shluger, Alexander L.; Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.

2011-01-27

128

Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium  

SciTech Connect

In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360{degrees}C.

Park, J.H.; Kassner, T.F.

1994-11-01

129

Nature of the solid solutions in the system ZrO/sub 2/-CaO  

SciTech Connect

The results of x-ray spectral microanalysis and x-ray diffraction analysis indicate that the solid solutions in the system ZrO/sub 2/-CaO must be interpreted as solutions of ZrO/sub 2/ in CaZr/sub 4/O/sub 9/. As regards the structure of the solid solutions in this system, they evidently must be described from the standpoint of the model of coordination defects by analogy with the system HfO-CaO, where the phases enriched with hafnium dioxide (from CaHf/sub 4/O/sub 9/ to CaHf/sub 6/O/sub 13/) were studied based on the defective structure of fluorite. In addition, the samples with intermediate compositions can be represented by a set of coherently related, ordered, interpenetrating structures.

Kostikov, Yu.P.; Leonov, A.I.

1986-12-01

130

Performance of the first-light adaptive optics system of LBT by means of CAOS simulations  

NASA Astrophysics Data System (ADS)

This presentation reports the numerical simulations we have done in order to evaluate the performance of the first-light AO system of LBT. The simulation tool used for this purpose is the Software Package CAOS, applicable for a wide range of AO systems and for which a brief recall of the main features is made. The whole process of atmospheric propagation of light, wavefront sensing (using a complete model of the pyramid wavefront sensor), wavefront reconstruction using the LBT672 adaptive secondary mirror modes), and closing of the loop, is simulated. The results are given in terms of obtained Strehl ratios in J-, H-, and K-band. Estimation of the resulting sky-coverage in K-band for different regions of the sky are also expressed. A comparison with the performance that would be obtained by using a Shack-Hartmann sensor is presented, confirming the gain achievable with the pyramid sensor.

Carbillet, Marcel; Vérinaud, Christophe; Esposito, Simone; Riccardi, Armando; Puglisi, Alfio; Femenía, Bruno; Fini, Luca

2003-02-01

131

Microstructure-property relationship for porous CaO stabilized ZrO2 support tubes  

SciTech Connect

The active elements of the Westinghouse solid oxide electrolyte fuel cell are supported on porous CaO stabilized ZrO2 tubes. These support tubes must possess adequate mechanical strength to survive both fabrication activities as well as long term cell operation. At the same time, gas diffusion rates through the porous structure must be high enough so as not to limit cell fabrication and cell operation processes that are dependent upon gas transport. Both mechanical properties and gas diffusion rates are strongly related to tube microstructure. These property-microstructure relationships are described. Using this understanding, porous support tubes with improved properties can be realized through compositional developments and/or processing innovations.

Rossing, B.R.

1983-10-01

132

Fluidized bed combustion systems integrating CO2 capture with CaO.  

PubMed

Capturing CO2 from large-scale power generation combustion systems such as fluidized bed combustors (FBCs) may become important in a CO2-constrained world. Using previous experience in capturing pollutants such as SO2 in these systems, we discuss a range of options that incorporate capture of CO2 with CaO in FBC systems. Natural limestones emerge from this study as suitable high-temperature sorbents for these systems because of their low price and availability. This is despite their limited performance as regenerable sorbents. We have found a range of process options that allow the sorbent utilization to maintain a given level of CO2 separation efficiency, appropriate operating conditions, and sufficiently high power generation efficiencies. A set of reference case examples has been chosen to discuss the critical scientific and technical issues of sorbent performance and reactor design for these novel CO2 capture concepts. PMID:15884387

Abanades, J Carlos; Anthony, Edward J; Wang, Jinsheng; Oakey, John E

2005-04-15

133

Large magnetoresistive effect in bulk Bi2212 with small additions of USr2CaO6  

NASA Astrophysics Data System (ADS)

A large magnetoresistive (MR) effect was observed in Bi2212 in which USr2CaO6 was added in a proportion of 6 wt%. The resistivity of melt-textured (MT) Bi2212 + 6 wt% USr2CaO6 possess a high sensitivity to applied dc fields, as compared to pure Bi2212, in particular at low fields, below 3 T, and in a temperature range between 45 and 85 K. In this temperature range, the MR effects of MT Bi2212 + 6 wt% USr2CaO6 display a maximum that may be tuned to a particular temperature within the above range, by changing the amount of added non-superconducting compound. X-ray results show that during the melt-texturing process of this mixture, the USr2CaO6 phase is stable and the reaction with Bi2212 matrix is minimal, in spite of a small decrease in the superconducting transition temperature. A cryogenic sensor was build and tested at 77 K in low fields. It shows high sensitivity and no hysteresis of resistivity when the applied field was cycled between 0 and 1 T.

Ionescu, M.; Winton, B.; Silver, T.; Dou, S. X.; Ramer, R.

2004-07-01

134

Synthesis of tourmaline solid solutions in the system Na2O-MgO-Al2O3-SiO2-B2O3-H2O-HCl and the distribution of Na between tourmaline and fluid at 300 to 700 °C and 200 MPa  

NASA Astrophysics Data System (ADS)

Tourmaline has been synthesized hydrothermally at 200 MPa between 300 and 700 °C from oxide mixtures with Mg-Al ratios for the end members dravite NaMg3Al6(Si6O18)(BO3)3(OH)3(OH) and Mg-foitite ?(Mg2Al)Al6 (Si6O18)(BO3)3(OH)3(OH). Six different Na concentrations were investigated to determine the distribution of Na between tourmaline and fluid in the SiO2-saturated system Na2O-MgO-Al2O3-SiO2-B2O3-H2O-HCl. Synthetic tourmaline ranges from X-site vacant (?) tourmaline (Mg-foitite) to nearly ideal dravite with Na=0.95 apfu. There are small, but significant, amounts of proton deficiency and negligible tetrahedral Al. Chemical variation is primarily caused by the substitutions Al?Mg-1Na-1 and minor AlMg-1H-1. Varying amounts of Na and ? determine the Mg/Al ratios. Besides tourmaline and quartz, additional Mg-Al phases are chlorite and, at 700 °C, cordierite. Albite is also present at high Na concentrations in the bulk composition. The c dimension of the tourmaline crystals increases with Na in tourmaline. The amount of Na in the X-site depends strongly on the bulk concentration of Na in the system as well as on the temperature. These factors in turn control the phase assemblage and the composition of the fluid phase. For the assemblage tourmaline + quartz + chlorite/cordierite + fluid, a linear relationship exists between Na concentration in the fluid (quenched after the run) and tourmaline with temperature: T °C [±25 °C]=(Nafluid/Natur)×558.878-14.692 (r2=0.96). For the assemblage tourmaline + albite + quartz + fluid, it is: T °C [±15 °C]=(Nafluid/Natur)×845.813-6.231 (r2=0.95), where Nafluid is the concentration of Na+ in the final fluid (mol/l) and Natur is the number of Na cations in the X-site of tourmaline. The equations are valid in the temperature range of 500-715 °C. Our experiments demonstrate that the occupancy of the X-site in combination with the changing concentrations of Al and Mg can be used to monitor changes in the fluid composition in equilibrium with a growing tourmaline crystal. Currently, this relation can be applied qualitatively to natural tourmaline to explain zoning in Na- and Al/(Al+Mg).

v. Goerne, G.; Franz, G.; Heinrich, W.

2001-05-01

135

Effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen  

SciTech Connect

The effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen was investigated to evaluate the potential of simultaneous SO{sub 2} and NO removal at the temperature range of 700-850{sup o}C. The physical and chemical properties of the CaO sulfation products were analyzed to investigate the NO reduction mechanism. Experimental results showed that sulfated CaO had a catalytic effect on NO reduction by NH{sub 3} in the presence of excess O{sub 2} after the sulfation reaction entered the transition control stage. With the increase of CaO sulfation extent in this stage, the activity for NO reduction first increased and then decreased, and the selectivity of NH{sub 3} for NO reduction to N{sub 2} increased. The byproduct (NO{sub 2} and N{sub 2}O) formation during NO reduction experiments was negligible. X-ray photoelectron spectroscopy (XPS) analysis showed that neither CaSO{sub 3} nor CaS was detected, indicating that the catalytic activity of NO reduction by NH{sub 3} in the presence of excess O{sub 2} over sulfated CaO was originated from the CaSO{sub 4} product. These results revealed that simultaneous SO{sub 2} and NOx control by injecting NH{sub 3} into the dry flue gas desulfurization process for NO reduction might be achieved. 38 refs., 6 figs., 1 tab.

Tianjin Li; Yuqun Zhuo; Yufeng Zhao; Changhe Chen; Xuchang Xu [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of Ministry of Education

2009-04-15

136

Intermitência alfvênica gerada por caos na atmosfera solar e no vento solar  

NASA Astrophysics Data System (ADS)

Dados medidos no vento solar rápido proveniente dos buracos coronais revelam que os plasmas no meio interplanetário são dominados por flutuações Alfvênicas, caracterizadas por uma alta correlação entre as variações do campo magnético e da velocidade do plasma. As flutuações exibem muitas características esperadas em turbulência magneto-hidrodinâmica totalmente desenvolvida, tais como intermitência e espectros contínuos. Contudo, os mecanismos responsáveis pela evolução de turbulência Alfvênica intermitente não são completamente compreendidos. Neste trabalho a teoria de caos é usada para explicar como sistemas Alfvênicos, modelados pela equação Schrödinger não-linear derivativa e pela equação Kuramoto-Sivashinsky, podem se tornar fortemente caóticos à medida em que parâmetros do plasma são variados. Pequenas perturbações no parâmetro de dissipação podem fazer com que o sistema mude bruscamente de um regime periódico, ou fracamente caótico, para um regime fortemente caótico. As séries temporais das flutuações do campo magnético nos regimes fortemente caóticos exibem comportamento intermitente, em que fases laminares ou fracamente caóticas são interrompidas por fortes estouros caóticos. É mostrado que o regime fortemente caótico é atingido quando as soluções periódicas ou fracamente caóticas globalmente estáveis interagem com soluções do sistema que são fortemente caóticas, mas globalmente instáveis. Estas soluções globalmente instáveis são conjuntos caóticos não-atrativos conhecidos como selas caóticas, e são responsáveis pelos fortes estouros nos regimes intermitentes. Selas caóticas têm sido detectadas experimentalmente em uma grande variedade de sistemas, sendo provável que elas desempenhem um papel importante na turbulência intermitente observada em plasmas espaciais.

Rempel, E. L.; Chian, A. C.-L.; Macau, E. E. N.; Rosa, R. R.

2003-08-01

137

The kinetic rate of SO/sub 2/ sorption by CaO  

SciTech Connect

The intrinsic rate constant for the rate of reaction of SO/sub 2/ with porous CaO in an excess of O/sub 2/ to form CaSO/sub 4/ has been determined from SO/sub 2/ sorption data on a wide range of particle diameters (1..mu..m-1mm), SO/sub 2/ partial pressures (60 Pa to 5 kPa), and temperatures (973-1,478K). An intrinsic SO/sub 2/ reaction order of unity has been validated through current fixed-bed experiments in the 60 to 300 Pa SO/sub 2/ partial pressure range, while fluidized-bed data were used to validate the reaction order from 500 Pa to 5 kPa SO/sub 2/ partial pressure. The absolute value of the rate constant and the activation energy was derived from data on small (1 ..mu..m) particles, which approach the limit of kinetic control. While analysis of this data base dose minimize the role of intraparticle diffusion through the porous sorbent particle, the filling of the small pores by the product deposits and the associated loss of internal surface area is critical to the data reduction. It is believed that the intrinsic rate constant is known to the accuracy to which the reactivity and the BET surface area may be measured.

Simons, G.A.; Garman, A.R.; Boni, A.A.

1987-02-01

138

Zircon saturation in felsic liquids: Experimental results and applications to trace element geochemistry  

Microsoft Academic Search

Hydrothermal experiments were carried out at 2 kbar water pressure, 700 °–800 ° C, with the objective of determining the level of dissolved Zr required for precipitation of zircon from melts in the system SiO2-Al2O3-Na2O-K2O. The saturation level depends strongly upon molar (Na2O + K2O)\\/Al2O3 of the melts, with remarkably little sensitivity to temperature, SiO2 concentration, or melt Na2O\\/ K2O.

E. Bruce Watson

1979-01-01

139

Geochemistry and Rb–Sr geochronology of the alkaline?peralkaline Narraburra Complex, central southern New South Wales; tectonic significance of Late Devonian granitic magmatism in the Lachlan Fold Belt  

Microsoft Academic Search

Three suites of alkaline granite can be recognised in the Narraburra Complex at the triple junction of the Tumut, Giralambone?Goonumbla and Wagga Zones, central southern New South Wales. On the basis of K2O\\/Na2O ratios, biotite and hornblende?biotite potassic I?type granites have been assigned to the Gilmore Hill (K2O\\/Na2O 1.00) and Barmedman Suites (K2O\\/Na2O > 1.2). These are metaluminous to weakly

R. J. Wormald; R. C. Price; A. I. S. Kemp

2004-01-01

140

The utilization of galvanic cells using Ca??Alumina solid electrolytes in a thermodynamic investigation of the CaO AI 2 O 3 system  

Microsoft Academic Search

Ca??-alumina solid electrolytes have been used in calcium concentration electrochemical cells to determine the standard free\\u000a energies of formation of the calcium aluminates, from their constituent oxides, in the temperature ranges specified: (1) CaO(s)\\u000a + 6Al2O3(s) ? CaO6Al203(s) ?G =-4270.9 - 9.4r(K)(200)cal = -17869.4 - 39.3T (840)J; 1100 to 1500 K. (2) CaO(s) + 2Al2O3(s) ? CaO.2Al2O3(s) ?G = -3087.1

R. V. Kumar; D. A. R. Kay

1985-01-01

141

Phase selection in the containerless solidification of undercooled CaO · 6Al 2O 3 melts  

Microsoft Academic Search

The CaO·6Al2O3 melts were solidified on an aero-acoustic levitator under a containerless processing condition at various undercoolings. A high-speed video was operated to monitor the recalescence behavior, from which the growth velocity as a function of melt undercooling was determined. The microstructures were observed and the crystalline phases were identified using the X-ray diffraction technique, indicting that the Al2O3 was

Mingjun Li; Kazuhiko Kuribayashi

2004-01-01

142

Opposite rumpling of the MgO and CaO (100) surfaces: A density-functional theory study  

Microsoft Academic Search

Density-functional theory calculations using the periodic slab approach are carried out to investigate the relaxed structures of the regular MgO and CaO(100) surfaces. Both local density and gradient corrected approximations to the exchange-correlation energy are employed and slab orbitals are expanded in Gaussian atom-centered orbitals as well as in plane waves. For MgO, the cations are displaced downwards towards the

Dominic R. Alfonso; James A. Snyder; John E. Jaffe; Anthony C. Hess; Maciej Gutowski

2000-01-01

143

Theory of F centers in the alkaline-earth oxides MgO and CaO  

Microsoft Academic Search

We present results of a theoretical study of the electronic structure of isolated anion vacancies (F-center-like defects) in the alkaline-earth oxides MgO and CaO using the multiple-scattering-theory-based muffin-tin Green's-function method. These ab initio calculations are valence-charge self-consistent for the vacancy and first shell of cation neighbors but, at present, do not include effects due to atomic relaxation around the vacancy

Barry M. Klein; Warren E. Pickett; Larry L. Boyer; R. Zeller

1987-01-01

144

Cryogenic magnetic field sensor based on the magnetoresistive effect in bulk Bi2212+USr2CaO6  

NASA Astrophysics Data System (ADS)

A large magnetoresistive (MR) effect was observed in melt-textured (MT) Bi2212 in which USr2CaO6 was added in a proportion of 6 wt %. The resistivity measurements of MT Bi2212+6 wt % USr2CaO6 show high sensitivity to applied dc fields, as compared to pure Bi2212, in particular at low fields, below 3 T, and in a temperature range between 45 K and 85 K. In this temperature range, the MR effect of MT Bi2212+6 wt % USr2CaO6 is two orders of magnitude larger than the MR effect in pure Bi2212, and display a maximum that may be tuned to a particular temperature within the above range, by changing the amount of added nonsuperconducting compound. A cryogenic sensor was built and tested at 77 K in low fields. It shows a good sensitivity and small (~1%) hysteresis of resistivity when the applied field was cycled between 0 T and 1 T.

Ionescu, M.; Winton, B.; Silver, T.; Dou, S. X.; Ramer, R.

2004-06-01

145

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium  

SciTech Connect

Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5--85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400--420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance. which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes(e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {ge}360{degrees}C.

Park, J.H.; Kassner, T.F.

1996-02-01

146

Effect of matrix liquid phase on interphase formation in SiC fibre-reinforced Si2N2OAl2O3CaO composites  

Microsoft Academic Search

Matrix compositions based on Si2N2O, with Al2O3 and CaO additions, were used to hot press Nicalon SiC fibre-reinforced composites at 1600 °C. With both CaO and Al2O3 additions, eutectic melting formed an appreciable volume of liquid phase during hot pressing, which remained as a stable glassy phase in the cooled composites. This liquid phase fostered formation of ~240 nm thick

Hyun-Ho Shin; Y. Berta; R. F. Speyer

1995-01-01

147

A density functional theory study of the adsorption of Hg and HgCl 2 on a CaO(001) surface  

Microsoft Academic Search

The adsorption of mercury and mercury chloride on a CaO(001) surface was investigated by the density functional theory (DFT)\\u000a by using Ca9O9 cluster embedded in an electrostatic field represented by 178 point charges at the crystal CaO lattice positions. For the\\u000a mercury molecular axis normal to the surface, the mercury can only coordinate to the O2? anion and has a

Xin Guo; Chuguang Zheng; Nanxia Lu

2007-01-01

148

Antibacterial glass-composite coatings for protection of special purpose steel panels  

NASA Astrophysics Data System (ADS)

It has been established that the most informative and universal method for determination of biocide properties of vitreous coatings is qualitative method that takes into account the growth level of biotest microorganisms inoculated into liquid nutrient media. It is shown, that biocidity of glass-composite coatings on the basis of glasses of Na2O - K2O - CaO - ZrO2 - TiO2 - Al2O3 - P2O5 - B2O3 - SiO2 system is determined by the presence of calcium phosphates in them and depends on the type of bactericide filler. The most effective ones by the action on Pseudomonas aeruginosa bacterium and Aspergillus niger and Candida albicans fungi are zinc titanate and Ag+, to Escherichia coli- only zinc phosphate.

Savvova, O.; Bragina, L.; Babich, E.

2011-12-01

149

[Determination of 12 elements in coal ash by x-ray fluorescence spectrometry].  

PubMed

A method for the determination of SiO2, Al2O3, Fe2O3, CaO, SO3, TiO2, K2O, Na2O, P2O5, MgO, MnO and BaO in coal ash by X-ray fluorescence spectrometry with melt sample preparation was developed. This method solved the problems of determination accuracy of S by using the 12:22 mix flux and oxide to lower the melt temperature. Using the soil standard sample and mixing the soil standard sample and coal ash standard sample solved the problem that there are not enough standard samples for coal ash analysis by XRF. The accuracy and precision of this method are acceptable, and the results are comparable to the those obtained by wet chemical method. PMID:18800742

Song, Yi; Guo, Fen; Gu, Song-hai

2008-06-01

150

Fluid interaction and element mobility in the development of ultramylonites  

NASA Astrophysics Data System (ADS)

Shear zones are often characterized by the presence of mylonitic fabrics. The textural development of such fabrics is enhanced by the presence of a fluid phase. In a single specimen of rock from the Brevard fault zone in North Carolina, we can demonstrate the development of ultramylonite domain by focused fluid flow. The ultramylonite interface retains a sharp textural and chemical discontinuity; this suggests that solute transport was dominantly parallel to the tectonic layering. Major chemical changes between the ultramylonite zone and the protolith include losses of SiO2, Na2O, and K2O and gain of CaO, FeO, and H2O in the high-strain domain.

Krishna Sinha, A.; Hewitt, David A.; Rimstidt, J. Donald

1986-10-01

151

Improved Retrieval of Chlorophyll and Carotenoids Contents at the Canopy Scale Using Hyperspectral CAO Data and PROSAIL Model  

NASA Astrophysics Data System (ADS)

The sustainability of biodiversity requires frequent and spatially detailed assessment of species number and distribution, among other information. Remote sensing is one of the most promising way to achieve this environmental management due to reasonable cost and accuracy. However, the use of airborne and spaceborne data remains challenging: sensors must combine the appropriate spatial and spectral resolutions to retrieve pertinent environmental parameters that will permit identification of specific properties of organisms present in an ecosystem. Leaf area index (LAI), canopy structure and pigment composition of vegetation are valuable information to study ecosystem dynamics and distinguish between many species. Chlorophyll and carotenoid pigments are of particular interest because they are involved in photosynthesis, but until now, remote sensing was unable to assess these pigments separately and accurately. Some advances have been made recently with the separation of these pigments in PROSPECT-5, a radiative transfer model that simulates leaf spectral reflectance and transmittance at 1 nm resolution. PROSAIL, the joint vegetation canopy reflectance model associating PROSPECT-5 with 4SAIL, the latest version of the SAIL model, was first run in direct mode to design vegetation indices sensitive to leaf pigments. Subsequently, we retrieved chlorophyll and carotenoid contents using PROSAIL with CAO (Carnegie Airborne Observatory) data acquired in Hawaii. The CAO, an imaging spectrometer coupled with a 3-D laser scanner, has already demonstrated its ability to manage biodiversity in various ecosystems like tropical rainforests or savannah. Its performance make it particularly adapted to assess vegetation structure, biochemistry, and then fluxes. The first results obtained when processing CAO images with PROSAIL are promising in terms of chlorophyll and carotenoid retrieval at the canopy scale. They show that our approach can provide original information on vegetation and hopefully new indicators to help manage and conserve biodiversity. They open new fields of investigation in the domain of mapping and monitoring Earth ecosystems from present operational (Aviris, Hyperion) or future (EnMap, HyspIRI) airborne and spaceborne sensors offering high spectral resolution data.

Feret, J.; Asner, G. P.; Jacquemoud, S.; François, C.

2008-12-01

152

Behavioral responses of Cao Vit gibbon (Nomascus nasutus) to variations in food abundance and temperature in Bangliang, Jingxi, China.  

PubMed

The Cao Vit gibbon is a critically endangered species with only about 110 individuals remaining in a degraded karst forest along the China-Vietnam border. Behavioral data from this site are particularly useful in understanding gibbon behavioral adaptations to different sets of ecological conditions and will contribute to the conservation of the species. We studied seasonal variation in the time budget and diet of the Cao Vit gibbon in response to variation in food availability and ambient temperature by observing two groups for 1,379 hr between January and December 2009. We used 5-min scan samples to record the activity of gibbons. Both ambient temperature and food availability varied from month to month. Gibbon groups increased resting time and huddled together in sleeping places in cold months. Gibbons spent more time feeding on fruit when fruit was more abundant suggesting that fruit was their preferred food. Alternatively, leaf eating was negatively correlated with leaf availability which suggested that leaves may be used as a fallback food. Gibbons increased their diet diversity when they ate more leaves. This might be a strategy to cope with toxins or digestion inhibitor accumulation associated with feeding from a limited number of leaf species. Individuals consumed more buds when Broussonetia papyrifera produced buds in March and April. During this period, they decreased traveling time and engaged in less frequent social interactions. Gibbons spent more time searching for and feeding on invertebrates during June and October. However, we did not collect data on invertebrate abundance and therefore cannot determine the relationship between invertebrate feeding and availability. We conclude that flexibility in consuming diverse food types and food species, and in responding to the availability of preferred foods, has enabled the Cao Vit gibbon to survive in a degraded karst forest habitat. PMID:22553151

Fan, Peng-Fei; Fei, Han-Lan; Ma, Chang-Yong

2012-05-02

153

Comparison between the in vitro surface transformations of AP40 and RKKP bioactive glasses.  

PubMed

Two bioactive silica-phosphate glasses, AP40 and RKKP, were compared in their behaviour in simulated biological environment. Their chemical composition is practically identical, except that RKKP contains small amounts of amphoteric network-former oxides Ta2O5 and La2O3 (composition in wt% for AP40: beta-Ca3(PO4)2 24.50, SiO2 44.30, CaO 18.60, Na2O 4.60, K2O 0.19, MgO 2.82, CaF2 4.99; RKKP: beta-Ca3(PO4)2 24.23, SiO2 43.82, CaO 18.40, Na2O 4.55, K2O 0.19, MgO 2.79, CaF2 4.94, Ta2O5 0.99, La2O3 0.09). Previous investigations showed a better performance in osteopenic bone for RKKP. To gain more insight into these differences in biological behaviour, the in vitro bioactivity of the glasses was studied by treatment with a continuously replenished Hanks' Balanced Salt Solution (HBSS). The glasses were examined before and after HBSS treatment for 20 and 40 days by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Energy Dispersion (EDX), Raman and IR vibrational spectroscopies. Some slight but notable differences between the two glasses were observed after HBSS treatment. IR and EDX analyses showed that deposits formed on both glasses were composed of a calcium deficient carbonate-apatite; however, the layer formed on RKKP glass was found to be slightly more calcium deficient and thinner. EDX analysis evidenced the presence of a small percentage of F- ions only in the layers formed on the RKKP samples. The differences disclosed, although slight, can contribute to the understanding of the different biological behaviour previously observed. PMID:15744599

Krajewski, A; Ravaglioli, A; Tinti, A; Taddei, P; Mazzocchi, M; Martinetti, R; Fagnano, C; Fini, M

2005-02-01

154

Making sense out of CAOS: Preliminary results on the Paleozoic-Mesozoic deformation of the Central Asian Orogenic System  

NASA Astrophysics Data System (ADS)

There are two contrasting models for the tectonic evolution of accretionary orogens, both based on the Paleozoic geology of the Central Asian Orogenic System (CAOS), which is located between the Siberian, European, and Chinese cratons. One model requires that syn-subduction strike-slip faults with more than 1000 km of displacement control the construction of accretionary orogens, whereas a second model suggests that thrust faults are responsible for shortening during and after arc magmatism. Specifically for the CAOS, previous studies show that igneous activity occurred in two episodes at 408-377 Ma and 344-290 Ma. The early phase is marked by calc-alkaline magmatism and occurred in an island-arc setting while the second phase exhibits geochemical characteristics of post-collisional magmatism. In the context of the existing pluton geochronology and geochemical interpretations, the first tectonic model requires CAOS strike-slip faulting to be Devonian in age, whereas the second requires that thrust faulting is as young as Permian. We completed field mapping, U-Th-Pb geochronology, thermobarometry, and 40Ar/39Ar thermochronology to determine the nature of tectonic contacts, timing and extent of metamorphism and deformation, and low temperature exhumation history of the southern Altai Mountains in NW China. Our results show that at least three northeast-dipping thrust faults were responsible for crustal shortening of at least 50%. The Ertix fault (also known as the Irtysh fault) juxtaposes high-grade metamorphic rocks from > 20 km depth against a Devonian-Carboniferous arc sequence. Thermochronologic data suggest that rocks were exhumed during motion on the Ertix fault between 280 Ma and 260 Ma. The Kuerti thrust, a range-bounding thrust fault, was exhuming rocks in its hanging-wall between 270 and 200 Ma. The Barils thrust was responsible for exhumation and cooling of lower amphibolite-grade hanging-wall rocks between 230 and 150 Ma. Minor orogen-parallel sinistral shear occurred after 261 Ma, based on zircon ages from a deformed granitoid. Our data suggest that major deformation, primarily accomplished by thrusting, occurred after the termination of arc magmatism in the CAOS, and does not support tectonic models requiring major syn-subduction strike-slip faulting during accretionary orogen development.

Briggs, S. M.; Yin, A.; Manning, C. E.

2005-12-01

155

Giant dielectric constant response of the composites in ternary system CuO-TiO{sub 2}-CaO  

SciTech Connect

The subsolidus phase relations of the ternary system CuO-TiO{sub 2}-CaO sintered at 950 deg. C in air have been determined by powder X-ray diffraction method. Only one ternary compound CaCu{sub 3}Ti{sub 4}O{sub 12} was found in this system. From room-temperature dielectric property mapping at 10 kHz, a giant dielectric constant (epsilon{sub r}>10{sup 4}) was observed for most of the ceramic composites in the CuO-rich region and in the region along the CaO-CuO binary line. The composites in the CaCu{sub 3}Ti{sub 4}O{sub 12}-rich region were found to give a comparable giant dielectric constant when sintered at 1050 deg. C. The particular microstructure of larger grains with predominant phase surrounded by smaller grains with the secondary phases was found in such composites with a high dielectric constant. The relations between structures and dielectric properties were investigated. An internal barrier layer capacitance effect is the most probable mechanism to explain this particular dielectric behavior. - Graphical Abstract: In the ternary system, CuO-TiO{sub 2}-CaO, a giant dielectric constant (epsilon{sub r}) above 10{sup 4} (red color) was observed in most of the composites sintered at only 950 deg. C in the CuO-rich region. Dashed lines show the phase boundaries.

Veith, Michael, E-mail: Michael.Veith@inm-gmbh.d [INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbruecken (Germany); Ren Shuhua; Wittmar, Matthias; Bolz, Henning [INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbruecken (Germany)

2009-10-15

156

Generation of hydrogen from polyvinyl chloride by milling and heating with CaO and Ni(OH)2.  

PubMed

This work discusses an alternative process option for the treatment of polyvinyl chloride (PVC) by producing hydrogen (H(2)) gas, at the same time fixing chlorine for proper environmental control. In the first-stage, a milling operation is performed in a planetary ball mill to obtain a mixture of PVC sample with CaO and Ni(OH)(2) to be used as feed in the second-step, involving heating of the milled product. Analyses by thermogravimetry-mass spectroscopy (TG-MS) and gas chromatography (GC) showed H(2), CH(4), CO and CO(2) as main constituents. The results clearly show that addition of Ni(OH)(2) to provide nickel as catalyst and CaO as adsorbent to fix CO(2) and HCl gases generated during heating, assisted in clean H(2) generation with concentration near 90% at temperatures between 450 and 550 degrees C. Analyses of solids after heating by X-ray diffraction and TG-DTA techniques showed both CaOHCl and CaCO(3) as main phases in the product. This process could be developed to treat PVC wastes together with other polymers and/or plastic wastes for production of H(2) gas. PMID:19231073

Tongamp, William; Zhang, Qiwu; Shoko, Miyagi; Saito, Fumio

2009-01-30

157

Charge competition with oxygen molecules determines the growth of gold particles on doped CaO films.  

PubMed

The influence of gas-phase oxygen on the growth of Au nanoparticles on Mo-doped CaO films has been investigated by means of low temperature scanning tunnelling microscopy and X-ray photoelectron spectroscopy. Whereas at ideal vacuum conditions, only 2D Au islands develop on the oxide surface, the fraction of 3D deposits increases with increasing O2 pressure until they become the dominant species in 106 mbar oxygen. The morphology crossover arises from changes in the interfacial electron flow between Mo donors in the CaO lattice and different ad-species on the oxide surface. In the absence of 02 molecules, the donor electrons are predominately transferred to the Au ad-atoms, which consequently experience enhanced binding to the oxide surface and agglomerate into 2D islands. In an oxygen atmosphere, on the other hand, a substantial fraction of the excess electrons is trapped by adsorbed O2 molecules, while the Au atoms remain neutral and assemble into tall 3D particles that are typical for non-doped oxides. Our experiments demonstrate how the competition for charge between different adsorbates governs the physical and chemical properties of doped oxides, so widely used in heterogeneous catalysis. PMID:24015581

Cui, Yi; Huang, Kai; Nilius, Niklas; Freund, Hans-Joachim

2013-01-01

158

Geochemical Distribution in the Surficial Sediments of Periyar River and Cochin Estuary on the South West Coast of India  

NASA Astrophysics Data System (ADS)

Geochemical study of bed sediments of Periyar river and Cochin estuary was carried out to understand the distribution, sources and possible factors responsible for the enrichment and depletion of various major and trace elements in the sediments. The river sediments are coarse to medium sand and estuarine sediments are sandy to clayey silt. The spatial distribution pattern of elements indicate that the sediment grain size is the major controlling factor in this estuarine-river system. The fine-grained sediments of the estuary are rich in MgO, CaO, Al2O3, TiO2, Fe2O3, Na2O, P2O5, MnO, Li, Sc, V, Cr, Co, Ni, Cu, Zn, As, Rb, Ta, Zr, Nb, Cd, Pb, LOI and poor in SiO2 and Ba. The organic rich sediments exhibit a similar distribution of Fe2O3, Al2O3, MgO and P2O5, Cu, Ni, Co, Cr and V. Factor analysis of the geochemical data gave four important factors which control the sediment chemistry. The first prominent factor (ca. 58 percent of variance) is characterised by high statistical loadings on most of the elements analysed except TiO2, CaO, K2O, Mo, Ag, Hf, Bi and Th. It is interpreted as a combined fine-grained alumino-silicate and organic matter factor. The second factor (13 percent of total variance) shows high loadings on the technogenic elements like Pb, Zn, Cd, Bi and also on Th. This is identified as an anthropogenic and industrial pollution factor. Factor 3, (11 percent variance) is characterised by high loadings on CaO, Sr and Ba and also on Na2O and K2O and can be interpreted as a biological contribution factor. The higher loadings on TiO2, MnO, Zr, Hf and Th in factor 4 (4 percent of variance) clearly represent the heavy minerals present in the study area. The factor scores point out that the fine-grained estuarine sediments mainly contribute towards the first factor whereas both estuarine and river sediments contribute to all other factors. The higher concentration of Fe2O3, K2O, MgO, P2O5, Zn, Ba, Pb, Cd, Bi, As, Cr, Ni and Sr in comparison with other Indian rivers suggest that the Periyar river and Cochin estuary is showing heavy anthropogenic contamination. Key words: Bottom sediments; Sediment chemistry; Factor analysis; Cochin estuary; Periyar river.

Paul, S. K.; Watanabe, Y.

2001-05-01

159

(CaO · Al2O3 · SiO2): Eu phosphors for violet/ultraviolet-to-white radiation conversion  

NASA Astrophysics Data System (ADS)

(2CaO · 0.5Al2O3 · 5SiO2): Eu and (CaO · 0.2Al2O3 · SiO2): Eu phosphors doped with B2O3 in an amount of 3 wt % are obtained by direct solid-phase synthesis at 1350°C. When excited by LED radiation with a maximum at 380 nm, these phosphors emit white light with color coordinates, which are close to those in the EBU and NTSC TV standards and fall into the field of white light corresponding to light warning systems according to the International Commission on Illumination (CIE).

Gurin, N. T.; Paksyutov, K. V.; Terent'ev, M. A.; Shirokov, A. V.

2012-02-01

160

Glass integrated optical wavelength division multiplexing (WDM) devices: a comparison between experimental results and modeling by CAOS software  

NASA Astrophysics Data System (ADS)

A systematic study on integrated wavelength multi/demultiplexers is presented, in which the experimental features of the devices, the theoretical predictions of a simple model, and the results of extensive modelling by a BPM analysis are compared. The components are based on the two-mode interference principle, and are fabricated on soda-lime glass by Ag-Na ion exchange. The modelling is performed by CAOS, a user-friendly general purpose simulator, based on a FD scheme with transparent boundary conditions. The agreement between experimental and simulated spectral characteristics is very good; moreover the proposed analysis procedure allows the determination of the maximum index variation (Delta) n and the diffusion depth D which describe the optical and geometrical characteristics of the waveguides.

Perrone, Guido; Gulisano, A.; Petazzi, Diego; Macchia, L.; Montrosset, Ivo; Morasca, Salvatore; Pozzi, Fabio; de Bernardi, Carlo S.; Zaffiro, G.

1994-08-01

161

Magnetism without Magnetic Ions: Percolation, Exchange, and Formation Energies of Magnetism-Promoting Intrinsic Defects in CaO  

NASA Astrophysics Data System (ADS)

We investigate theoretically the prospects of ferromagnetism being induced by cation vacancies in nonmagnetic oxides. A single Ca vacancy VCa0 has a magnetic moment due to its open-shell structure but the ferromagnetic interaction between two vacancies extends only to four neighbors or less. To achieve magnetic percolation on a fcc lattice with such an interaction range one needs a minimum of 4.9% vacancies, or a concentration 1.8×1021cm-3. Total-energy calculations for CaO show, however, that due to the high vacancy formation energy even under the most favorable growth conditions one can not obtain more than 0.003% or 1018cm-3 vacancies at equilibrium, showing that a nonequilibrium vacancy-enhancement factor of 103 is needed to achieve magnetism in such systems.

Osorio-Guillén, J.; Lany, S.; Barabash, S. V.; Zunger, A.

2006-03-01

162

Dry mechanochemical synthesis of hydroxyapatites from DCPD and CaO: influence of instrumental parameters on the reaction kinetics.  

PubMed

Mechanochemistry is a possible route to synthesize calcium deficient hydroxyapatite (CDHA) with an expected molar calcium-to-phosphate (Ca/P) ratio +/-0.01. To optimize the experimental conditions of CDHA preparation from dicalcium phosphate dihydrate (DCPD) and calcium oxide by dry mechanosynthesis reaction, we performed the kinetic study varying some experimental parameters. This kinetic study was carried out with two different planetary ball mills (Retsch or Fritsch Instuments). Results obtained with the two mills led to the same conclusions although the values of the rate constants of DCPD disappearance and times for complete reaction were very different. Certainly, the origin of these differences was from the mills used, thus we investigated the influence of instrumental parameters such as the mass and the surface area of the balls or the rotation velocity on the mechanochemical reaction kinetics of DCPD with CaO. Results show that the DCPD reaction rate constant and the inverse of the time for complete disappearance of CaO both vary linearly with (i) the square of the rotation velocity, (ii) the square of eccentricity of the vial on the rotating disc and (iii) the product of the mass by the surface area of the balls. These observations comply with theoretical models developed for mechanical alloying. The consideration of these four parameters allows the transposition of experimental conditions from one mill to another or the comparison between results obtained with different planetary ball mills. These instrumental parameters have to be well described in papers concerning mechanochemistry or when grinding is an important stage in a process. PMID:14643588

Mochales, Carolina; El Briak-BenAbdeslam, Hassane; Ginebra, Maria Pau; Terol, Alain; Planell, Josep A; Boudeville, Philippe

163

Use of solid-electrolyte galvanic cells to determine the activity of CaO in the CaO-ZrO{sub 2} system and the standard Gibbs free energies of formation of CaZrO{sub 3} from CaO and ZrO{sub 2}  

SciTech Connect

Ultraclean steel is deoxidized by the addition of aluminum, followed by desulfurizing and deoxidizing by the addition of calcium and zirconium. As a result of the deoxidation and desulfurization of molten steel, considerable oxide and sulfide inclusions are produced. The activity of CaO in the CaO-ZrO{sub 2} system has been measured at 1,572 to 1,877 K with a galvanic cell composed of 4CaO {center_dot} P{sub 2}O{sub 5} as the solid electrolyte. The activity ZrO{sub 2} was calculated from the activity of CaO by integrating the Gibbs-Duhem relation. From the activities of CaO and ZrO{sub 2}, the standard Gibbs free energy of formation of CaO {center_dot} ZrO{sub 2} was determined as follows: {Delta}G{sub f}{sup 0} = {minus}25,200 ({+-}150) {minus} 17.58 ({+-}0.085) T (1,633 to 1,873 K) J/mol.

Tanabe, Jun [Nippon Inst. of Tech., Saitama (Japan). Dept. of Mechanical Engineering; Nagata, Kazuhiro [Tokyo Inst. of Tech. (Japan). Dept. of Metallurgical Engineering

1996-08-01

164

Selective catalytic reduction of nitric oxide by methane in the presence of oxygen over CaO catalyst  

SciTech Connect

The selective catalytic reduction of nitric oxide by methane in the presence of oxygen was studied over CaO catalyst in the temperature range 550--850 C. The nitric oxide conversion-versus-temperature profile was found to depend on oxygen feed concentration, while the selectivity to N{sub 2} formation was found to be 100% and independent of oxygen feed concentration in the range 1--10 mol%. The kinetic study has shown that the reaction order with respect to NO and CH{sub 4} is 1.0 and 0.5, respectively. On the other hand, the reaction order with respect to O{sub 2} was found to be slightly positive for O{sub 2} feed concentrations up to 1 mol% and slightly negative at higher concentrations. The apparent activation energy of the reaction in the presence of oxygen was found to be 14.6 kcal/mol. The addition of 2.5 mol% CO{sub 2} and 5 mol% H{sub 2}O in the feed stream had a considerable inhibiting effect on NO conversion in the range 550--650 C, while a small inhibiting effect of CO{sub 2} and a positive effect of H{sub 2}O were observed in the range 700--850 C. Temperature-programmed desorption (TPD) of NO revealed the presence of two well-resolved NO peaks in the temperature range 250--650 C, a behavior also observed during a temperature-programmed oxidation experiment under O{sub 2}/He flow. However, during temperature-programmed surface reaction under CH{sub 4}/He flow the NO desorption spectrum showed a significant shift of the stronger adsorbed NO species toward lower temperatures. Preadsorbed CO{sub 2} on the CaO surface was found to largely affect the chemisorption of NO and its desorption kinetics during TPD. The amount of deposited carbon-containing species on the catalyst surface during reaction was determined with transient titration experiments and it was found to be small.

Fliatoura, K.D.; Verykios, X.E. [Univ. of Patras (Greece). Dept. of Chemical Engineering; Costa, C.N.; Efstathiou, A.M. [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Natural Sciences

1999-04-25

165

Magmatic differentiation in the calc-alkaline Khalkhab-Neshveh pluton, Central Iran  

NASA Astrophysics Data System (ADS)

Geochemical and isotopic data (Sr, Nd) are presented for the Khalkhab-Neshveh pluton, an E-W elongated body of quartz monzogabbro, quartz monzodiorite, granodiorite and granite in the Urumieh-Dokhtar magmatic arc of Central Iran. The plutonic rocks are medium- to high-K, metaluminous, and I-type, with 52-71 wt.% SiO2. The geochemistry shows smooth differentiation trends in which most major elements (except Al2O3, K2O and Na2O) are negatively correlated with SiO2; K2O, Ba, Rb, Ce, Nb, and Zr are positively correlated. Na2O, Sr, Eu and Y follow curves that are not considered to represent simple mixing between mafic and felsic magmas, but reflect crystal fractionation of clinopyroxene, plagioclase and hornblende. Initial 87Sr/86Sr ratios (˜0.7047) and &z.epsiv;Ndt values (˜+3.0) are essentially constant, and the large volume of quartz monzogabbros compared to granites, as well as the lack of mafic enclaves in more evolved rocks, are also indicative of crystal fractionation rather than mixing of magmas from different sources. Clinopyroxene fractionation was the main control in the evolution of the magmas up to 55% SiO2; hornblende took over from 55 wt.%, resulting in decreasing Dy/Yb with increasing silica content in the most siliceous rocks. Sr concentration increases up to 55% SiO2, and then decreases together with CaO, Al2O3, Na2O. Fractionation of opaque minerals and apatite throughout the sequence, and the continuous increase in K2O and Ba vs. SiO2 reflect the absence of significant fractionation of biotite and K-feldspar. Based on geochemical and isotope data, geophysics information and field studies, it seems that suturing of the Arabia and Iran plates caused the Khalkhab and Koush nousrat faults with left-lateral strike-slip in the Urumieh-Dokhtar region, and generated a purely tensional T space at 32° to the faults which was exploited by the emplacement of Khalkhab-Neshveh pluton.

Rezaei-Kahkhaei, Mehdi; Galindo, Carmen; Pankhurst, Robert J.; Esmaeily, Dariush

2011-08-01

166

Petrogenesis and metallogenic setting of the Habo porphyry Cu-(Mo-Au) deposit, Yunnan, China  

NASA Astrophysics Data System (ADS)

Although most porphyry-type deposits are associated with subduction-related magmas within magmatic arc settings, recent research has identified a number of porphyry-type deposits that formed in post-subduction tectonic settings. The newly discovered Habo porphyry Cu-(Mo-Au) deposit in Yunnan, China, formed in a post-subduction tectonic setting and is located in the southwest of the Cenozoic Ailao Shan-Red River continental collision zone. The deposit is associated with the Habo South granite pluton, which consists of three mineralization-related quartz monzonite porphyries and a post-mineralization diorite porphyry. Zircons from the Habo South granite and quartz monzonite porphyries were analyzed by in situ U-Pb LA-ICP-MS, yielding a similiar age of 36 Ma, with molybdenite Re-Os isotope dating indicating that the Habo porphyry deposit formed at 35.5 Ma. Both magmatism and the associated mineralization at Habo are coeval with porphyry copper deposits in the Yulong metallogenic belt of Eastern Tibet. The Habo South granite and porphyries have SiO2 concentrations of 67.28-73.44 wt.%, MgO concentrations of <1.5 wt.%, Al2O3 concentrations around 15 wt.%, Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios of >1.1, K2O + Na2O concentrations generally between 7 and 9 wt.%, and K2O/Na2O ratios of >1.4, showing indicative of high-K magmas. The Habo South granite and quartz monzonite porphyries are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE), with high Sr and low Y concentrations. They have initial 87Sr/86Sr values of 0.7071-0.7083, with &z.epsiv;Nd(t) values from -5.3 to -3.7. These features are indicative of lower-crust derived adakitic magmas, and are similar to those of mineralized porphyries in the Yulong copper belt in Eastern Tibet. This mineralogical, geochemical, and isotope evidence strongly suggests that the magmas that formed both porphyries and the Habo South granite were derived by partial melting of a region of thickened lower crust, with assimilation of components generated from a region of phlogopite-bearing lithospheric mantle involved during intrusion. The Habo porphyry deposit represents an extension of the Yulong metallogenic belt and formed in response to regional tectonic activity in Eastern Tibet.

Zhu, Xiangping; Mo, Xuanxue; White, Noel C.; Zhang, Bo; Sun, Mingxiang; Wang, Shuxian; Zhao, Sili; Yang, Yong

2013-04-01

167

Chemical and morphological consequences of acidification of pure, phosphated, and phosphonated CaO: influence of CO2 adsorption.  

PubMed

In situ Fourier transform infrared (FTIR) spectroscopy was employed to characterize the adsorption behavior (as a function of pressure or time) and surface species of CO2 molecules on pure, phosphated, and phosphonated CaO. Carbonate and bicarbonate species were found to form on the pure oxide, whereas on the phosphated and phosphonated oxide samples the carbonate species were found to substitute favorably some of the OH(-) and PO4(3-) groups thereon exposed, respectively. Before and after carbonation, the test samples were further examined by in situ FTIR spectroscopy of adsorbed pyridine species, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Then they were in situ acidified by exposure to a wet atmosphere of HCl vapor at 673 K for 10 min and re-examined similarly to reveal the influence of CO2 adsorption on the chemical and morphological consequences of acidification. The results obtained show the carbonate substitution of PO4(3-) groups to enhance agglomeration of the otherwise fine, longitudinal material particles into much bulkier ones and to render the otherwise more stable phosphonate groups less stable to acid treatment than the phosphate groups. Moreover, the bulky particle agglomerates of the carbonated test samples were detectably eroded following the acid treatment. PMID:18512873

Zaki, Mohamed I; Knözinger, Helmut; Tesche, Bernd; Mekhemer, Gamal A H; Bongard, Hans-Josef

2008-05-30

168

Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO·7Al2O3  

NASA Astrophysics Data System (ADS)

Natural 12CaO·7Al2O3 (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. These measurements suggest the existence of a narrow conduction band between the main conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, J. A.; Buling, A.; Kurmaev, E. Z.; Sushko, P. V.; Neumann, M.; Finkelstein, L. D.; Kim, S.-W.; Hosono, H.; Moewes, A.

2012-01-01

169

Strong enhancement of superconductivity in inorganic electride 12CaO·7Al2O3:e- under high pressure  

NASA Astrophysics Data System (ADS)

We present the results of the pressure dependence of the superconductivity of the inorganic electride 12CaO·7Al2O3:e- (C12A7:e-) single crystal through the ac-susceptibility measurement under high pressure. C12A7:e- has the cage structure and the density of states derived from the cages may play an important role in the superconductivity. The superconducting transition temperature ( T c) is ˜ 0.2 K at ambient pressure and monotonically increases up to 1.79 K at 4.7 GPa. The upper critical field H c2 and - dH c2/ dT at T c, in proportion to the density of states (DOS) at Fermi energy becomes larger under high pressure. The superconductivity in C12A7:e- is mediated by the electron-phonon interaction, and the increase of Tc with pressure may arise from a peak structure of the DOS of cage conduction band.

Tanaka, Shigeki; Kato, Tomoki; Miyake, Atsushi; Kagayama, Tomoko; Shimizu, Katsuya; Kim, Sung Wng; Matsuishi, Satoru; Hosono, Hideo

2013-08-01

170

Spectroscopic Characterization of a Multiband Complex Oxide: Insulating and Conducting Cement 12CaO·7Al?O?  

SciTech Connect

Natural 12CaO·7Al?O? (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a “cage conduction band” inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. Thesemeasurements suggest the existence of a narrow conduction band between themain conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

McLeod, John A.; Buling, A.; Kurmaev, Ernst Z.; Sushko, Petr V.; Neumann, N.; Finkelstein, L. D.; Kim, S. W.; Hosono, H.; Moewes, Alexander

2012-01-13

171

Calciothermic reduction of TiO2 and in situ electrolysis of CaO in the molten CaCl2  

NASA Astrophysics Data System (ADS)

A new cell concept for calciothermic reduction is presented where TiO2 is used as the raw material for reduction. The reduction system consists of a single cell, where both the reduction reaction and the electrolytic reaction for recovery of reducing agent coexist in the same molten CaCl2 bath. TiO2 powder reacts with a few mol%Ca dissolved in the melt. Sufficiently deoxidized titanium metal was obtained at the bottom of the cell. Because the molten CaCl2 has a large solubility for CaO, both mechanisms of the halide flux deoxidation and the electrochemical deoxidation work efficiently once the metallic Ti was precipitated. The reducing agent is in situ recovered by electrolysis of CaO as, Attheanode:C+2O=CO+4e Atthecathode:Ca+2e=Ca. Some experimental results are presented for confirmation of this proposal and mechanism.

Suzuki, Ryosuke O.

2005-02-01

172

Comparison of phosgene, chlorine, and hydrogen chloride as reagents for converting molten CaO. CaCl/sub 2/ to CaCl/sub 2/  

SciTech Connect

One method used at Los Alamos for preparing impure plutonium metal from the impure oxide is batch reduction with calcium metal at 850/sup 0/C in a CaCl/sub 2/ solvent. The solvent salt from this reduction is currently discarded as low-level radioactive waste only because it is saturated with the CaO by-product. We have demonstrated a pyrochemical technique for converting the CaO to CaCl/sub 2/, thereby incorporating solvent recycle into the batch reduction process. We discuss the effectiveness of HCl, Cl/sub 2/, and COCl/sub 2/ as chlorinating agents and present initial data on regenerating and recycling actual, spent-solvent salts. 6 refs., 8 figs., 1 tab.

Fife, K.W.; Bowersox, D.F.; McCormick, E.D.

1985-09-01

173

Comparison of phosgene, chlorine, and hydrogen chloride as reagents for converting molten CaO. CaCl/sub 2/ to CaCl/sub 2/  

SciTech Connect

One method at Los Alamos for preparing impure plutonium metal from the impure oxide is by batch reduction with calcium metal at 850/sup 0/C in a CaCl/sub 2/ solvent. The solvent salt from this reduction is currently discarded as low-level radioactivity waste only because it is saturated with the CaO byproduct. We have demonstrated a pyrochemical technique for converting the CaO to CaCl/sub 2/ thereby incorporating solvent recycling into the batch reduction process. We will discuss the effectiveness of HCl, Cl/sub 2/, and COCl/sub 2/ as chlorinating agents and recycling actual spent process solvent salts. 6 refs., 8 figs.

Fife, K.W.

1985-01-01

174

Role of Y{sub 2}O{sub 3}, CaO, MgO additives on structural and microstructural behavior of zirconia/mullite aggregates  

SciTech Connect

Zirconia mullite (MUZ), Y{sub 2}O{sub 3}-MUZ, CaO-MUZ and MgO-MUZ composites, synthesized through plasma fusion technique, are becoming important due to their commercial scale of production within five minutes of plasma treatment from sillimanite, zircon and alumina mixture. The X-ray diffraction studies reveal the monoclinic zirconia phase in MUZ composite whereas mixed monoclinic, tetragonal and cubic phases of zirconia have been observed in Y{sub 2}O{sub 3}, CaO, MgO added MUZ composites. The Y{sub 2}O{sub 3}, CaO and MgO additives act as sintering aids to favour the transformation and stabilisation of tetragonal and cubic zirconia phases at room temperature. These additives also play a key role in the development of various forms of microstructure to achieve dense MUZ composites.

Mishra, D. K.; Prusty, Sasmita; Mohapatra, B. K.; Singh, S. K.; Behera, S. N. [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); Geological Survey of India, Alandi Road, Pune 411 006, Maharashtra (India); Mineralogy Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); National Institute of Science and Technology (NIST), Berhampur 761 008, Odisha (India)

2012-07-23

175

Spin-Lattice Coefficients for Gd3+ and Eu2+ in CaF2 and for Gd3+ in CaO  

Microsoft Academic Search

We have measured the spin-lattice coefficients of Eu2+ and Gd3+ in CaF2 and Gd3+ in CaO by studying the effect of uniaxial stress on the EPR spectra of these ions. The experimental data show that fourth-order terms in the spin-lattice Hamiltonian give significant contributions. The values of the second-order spin-lattice coefficients are given, and the fourth-order contribution is tentatively identified

R. Calvo; R. A. Isaacson; Z. Sroubek

1969-01-01

176

Quantitative evaluation of antibacterial activities of metallic oxide powders (ZnO, MgO and CaO) by conductimetric assay  

Microsoft Academic Search

Antibacterial activities of metallic oxide (ZnO, MgO and CaO) powders against Staphylococcus aureus and Escherichia coli were quantitatively evaluated by measuring the change in electrical conductivity of the growth medium caused by bacterial metabolism (conductimetric assay). The obtained conductivity curves were analyzed using the growth inhibition kinetic model proposed by Takahashi for calorimetric evaluation, and the metallic oxides were determined

J. Sawai

2003-01-01

177

Thermal expansion of CaAl 4O 7-based refractory compositions containing MgO and CaO additions  

Microsoft Academic Search

Various compositions of recently developed CaAl4O7-based ceramics are mentioned with special reference to those called “nonexpansive refractories” (=NER). The observed effect of deep depression of their thermal expansion is mainly ascribed to the creation of a specific microstructure resulting from high temperature reactions of CaAl4O7 with MgO or CaO additives yielding a CaAl2O4-based liquid. Some details characterizing the phase composition

S. Jonas; F. Nadachowski; D. Szwagierczak; G. Wójcik

2006-01-01

178

Heat requirements in a calciner of CaCO 3 integrated in a CO 2 capture system using CaO  

Microsoft Academic Search

Several systems for CO2 capture using CaO as regenerable sorbent are under development. In addition to a carbonation step, they all need a regeneration step (calcination of CaCO3) to produce a concentrated stream of CO2. Different options for calcination may be possible, but they all share common operating windows that appear when the mass and heat balances in the system

N. Rodriguez; M. Alonso; G. Grasa; J. Carlos Abanades

2008-01-01

179

Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics  

NASA Astrophysics Data System (ADS)

T he oxidation behaviors of composites SiAlON/MgAlON phases (?-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 °C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

2013-02-01

180

CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system  

SciTech Connect

Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.

Park, J.H.; Kassner, T.F.

1995-09-01

181

Effects of poly(lactic-co-glycolic acid) (PLGA) degradability on the apatite-forming capacity of electrospun PLGA/SiO(2)-CaO nonwoven composite fabrics.  

PubMed

We investigated the effects of poly(lactic-co-glycolic acid) (PLGA) degradability on the apatite-forming ability of electrospun PLGA/SiO(2)-CaO gel composite fabric. Two PLGA copolymer compositions with low and high degradability were used in experiments. A nonwoven polymer/ceramic composite fabric composed of randomly mixed microsized biodegradable PLGA fibers and nanosized bioactive SiO(2)-CaO gel fibers was prepared using a simultaneous electrospinning method. A 17 wt.% PLGA solution was prepared using 1,1,3,3-hexafluoro-2-propanol as a solvent, while the SiO(2)-CaO gel solution was prepared via a condensation reaction following hydrolysis of tetraethyl orthosilicate under acidic conditions. PLGA and SiO(2)-CaO gel solutions were spun simultaneously with two separate nozzles under electric fields of 1 and 2 kV/cm using two syringe pumps with flow rates of 7.5 and 5 mL/h, respectively. As controls, low and high degradable PLGA and SiO(2)-CaO gel nonwoven fabrics were also made by the same methods. The five nonwoven fabrics that were produced were exposed to simulated body fluid (SBF) for 1 week. SBF exposure resulted in the deposition of a layer of apatite crystals on the surfaces of both the SiO(2)-CaO gel and the low degradable PLGA/SiO(2)-CaO gel composite fabrics, but not on the low and high degradable PLGA or the high degradable PLGA/SiO(2)-CaO gel composite fabrics. The results are explained in terms of the acidity of the PLGA degradation products, which could have a direct influence on apatite dissolution. PMID:20091921

Kim, In Ae; Rhee, Sang-Hoon

2010-04-01

182

A comparison of the chemical composition and bioactive ingredients of the Chinese medicinal mushroom DongChongXiaCao, its counterfeit and mimic, and fermented mycelium of Cordyceps sinensis  

Microsoft Academic Search

The Chinese herbal drug DongChongXiaCao, a medicinal and edible mushroom originating from the fungus Cordyceps sp., has been developed into health foods. Counterfeit and mimic types are frequently found in markets. Mycelial preparations of Cordyceps sinensis, via submerged fermentation, have been commercialized and also named DongChongXiaCao. This investigation endeavours to characterize the proximate composition, amino acid profiles, and contents of

Tai-Hao Hsu; Li-Hua Shiao; Chienyan Hsieh; Der-Ming Chang

2002-01-01

183

Caos en Dinámica Estelar  

NASA Astrophysics Data System (ADS)

We describe some recent advances in the application of chaos theory to stellar dynamics, particularly those related to triaxial galaxies with central singularities. We also list current research on chaos in stellar dynamics conducted by La Plata astronomers and physicists.

Muzzio, J. C.

184

Heavy doping of H{sup -} ion in 12CaO.7Al{sub 2}O{sub 3}  

SciTech Connect

12CaO.7Al{sub 2}O{sub 3} (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H{sup -}), oxide (O{sup 2-}), hydroxide (OH{sup -}) ions, and electrons, has been doped with H{sup -} ions to investigate its effects as dominant extraframework species. Chemical doping with CaH{sub 2} enables the concentration of H{sup -} ions to reach almost the theoretical maximum. The concentration of H{sup -} ions is characterized by optical absorption intensity ascribed to photoionization of H{sup -} ions, and {sup 1}H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F{sup +} absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H{sup -} ion doping increases until it reaches half the theoretical maximum and then decreases as the H{sup -} ion concentration increases further. This dependence indicates that both H{sup -} and O{sup 2-} ions are necessary for the generation of persistent electrons. - Graphical abstract: CaH{sub 2} reduction markedly enhances H{sup -} ion doping in 12CaO.7Al{sub 2}O{sub 3}. The H{sup -} ion incorporation is evaluated using optical absorption and {sup 1}H-MAS-NMR spectra. Both H{sup -} and O{sup 2-} ions are responsible for photogeneration of electrons. Highlights: > CaH{sub 2} reduction markedly enhances H{sup -} ion doping in 12CaO.7Al{sub 2}O{sub 3}. {yields}The H{sup -} ion incorporation is evaluated using optical absorption and {sup 1}H-MAS-NMR spectra. > Both H{sup -} and O{sup 2-} ions are responsible for photogeneration of electrons.

Hayashi, Katsuro, E-mail: k-hayashi@lucid.msl.titech.ac.jp [Center for Secure Materials, Materials and Structures Laboratory, Tokyo Institute of Technology, R3-34, 4295 Nagatsuta, Yokohama 226-8503 (Japan)

2011-06-15

185

EPR spectra of Cr3+ ions in LiNbO3:ZnO and LiNbO3: CaO  

NASA Astrophysics Data System (ADS)

The electron paramagnetic resonance spectra of Cr3+ in LiNbO3 co-doped with ZnO or CaO (? 6%) have been studied. Both impurities give rise to the same effect as that observed in MgO-doped samples: a strong diminution of the anisotropic (axial) spectrum reported for LiNbO3:Cr and the appearance of an intense and isotropic line. The origin of this line in the co-doped samples is discussed.

Bravo, D.; Martín, A.; Voda, M.; López, F. J.

1995-12-01

186

Phase selection in the containerless solidification of undercooled CaO {center_dot} 6Al{sub 2}O{sub 3} melts  

SciTech Connect

The CaO {center_dot} 6Al{sub 2}O{sub 3} melts were solidified on an aero-acoustic levitator under a containerless processing condition at various undercoolings. A high-speed video was operated to monitor the recalescence behavior, from which the growth velocity as a function of melt undercooling was determined. The microstructures were observed and the crystalline phases were identified using the X-ray diffraction technique, indicting that the Al{sub 2}O{sub 3} was solidified when the melt temperature was higher than the peritectic temperature, T{sub p}. When the melt was undercooled below T{sub p}, the CaO {center_dot} 6Al{sub 2}O{sub 3} (CA{sub 6}) peritectic phase was crystallized directly from the undercooled melts. With respect to the direct formation of the peritectic phase, further analysis from the viewpoints of competitive nucleation indicated that the minimum free energy principle may be applied to elucidate the nucleation of CA{sub 6} phase. In terms of the competitive growth behavior, the interface attachment kinetics for Al{sub 2}O{sub 3} and CA{sub 6} phases are calculated by using the classical BCT model indicating that although the Al{sub 2}O{sub 3} phase doped by CaO has about four times larger interface kinetic coefficient than that of the CA{sub 6} peritectic phase, the growth kinetics of Al{sub 2}O{sub 3} in the melt with the CaO {center_dot} 6Al{sub 2}O{sub 3} chemical composition is not sufficiently high to replace the CA{sub 6} phase as the primary phase. Therefore, once CA{sub 6} is nucleated, it can develop into a macro crystal as the primary phase. The competitive nucleation and growth behavior in the CA{sub 6} system is different from those in other well-studied peritectic alloys and the present investigation on the phase formation will be an essential supplement to the phase selection theory.

Li Mingjun; Kuribayashi, Kazuhiko

2004-07-12

187

Structure and properties of the slags of continuous converting of copper nickel-containing mattes and concentrates: II. Effect of the SiO2/CaO ratio on the structure and liquidus temperature of the slags  

NASA Astrophysics Data System (ADS)

The structure and liquidus temperature of the SiO2-CaO-Al2O3-FeO x -Cu2O-NiO slags that form during continuous converting of copper mattes and concentrates into blister copper are analyzed. The slag melt compositions are varied over a wide SiO2/CaO range. The slags are studied by X-ray diffraction, scanning electron microscopy, and electron-probe microanalysis. The liquidus temperature of the slags is determined by differential thermal analysis. It is found that, depending on the SiO2/CaO ratio, the structure and liquidus temperature of the slags change and the forms of copper in a slag also change. The SiO2/CaO range in a slag is recommended for the process of continuous converting of a copper nickel-containing sulfide raw materials.

Pigarev, S. P.; Tsymbulov, L. B.; Selivanov, E. N.; Chumarev, V. M.

2012-03-01

188

Effects of CaO, Al 2 O 3 , and MgO additions on the copper solubility, ferric\\/ferrous ratio, and minor-element behavior of iron-silicate slags  

Microsoft Academic Search

The effects of CaO, Al2O3, and MgO additions, singly or in combination, on the copper solubility, the Fe3+\\/Fe2+ ratio in slag, and on the minor-element behavior of silica-saturated iron silicate slags were examined at 1250 °C and a p\\u000a O2 of 10?12 to 10?6 atm. The results indicated that copper solubility in slag was lowered with the addition of CaO,

Hang Goo Kim; H. Y. Sohn

1998-01-01

189

Performance of CaO and MgO for the hot gas clean up in gasification of a chlorine-containing (RDF) feedstock.  

PubMed

Calcined limestone (CaO) and calcined dolomite (CaO.MgO) were tested at bench scale to study their usefulness in cleaning hot raw gas from a fluidized bed gasifier of a synthetic or simulated refuse-derived fuel (RDF) with a high (3 wt%) content in chlorine. In the gas cleaning reactor two main reactions occurred simultaneously: the elimination of HCl and the elimination of tar by steam reforming. The elimination of HCl formed CaCl2 and MgCl2 with melting points below the high (above 800 degrees C) temperatures required for the simultaneous tar elimination reaction. So, the CaO-based particles progressively melted and the catalytic gas cleaning reactor became a compact, agglomerated or glued, cake. Therefore, the life and usefulness of the CaO-based solids used was very low. Nevertheless, and to further avoid these problems, some positive guidelines for future research are proposed here. PMID:18372172

Corella, José; Toledo, José M; Molina, Gregorio

2008-03-26

190

Factors Related to Adoption and Non-Adoption of Technical and Organizational Recommendations by Farmers Involved with Societe de Developpement du Cacao (SO.DE.CAO) in Cameroon. A Research Summary.  

ERIC Educational Resources Information Center

|In order to promote cocoa production and assist cocoa farmers in overcoming diseases in this crop, the government of Cameroon created an experimental corporation called Societe de Developpement du Cacao (SO.DE.CAO) in 1974. This organization functioned much like an extension service to provide information about crop production and disease…

Kamga, Andre; Cheek, Jimmy G.

191

Thermal stabilities, physical and optical properties of (KO)-O-2-(NaO)-O-2-(NbO5)-O-2-TeO2 glasses  

Microsoft Academic Search

The thermal stabilities, physical and optical properties of xK(2)O-(14-x)Na2O-14Nb(2)O(5)-72TeO(2) (x = 0 similar to 12 mol%) glasses have been studied. The glasses consisting of ca. 10 mol% K2O show high thermal stabilities with values of Delta T = Tx - Tg = ca. 105 degrees C against crystallization, where Tg and Tx are the glass transition and crystallization onset temperatures,

Euh Duck Jeong; Myoung Gyu Ha; Hyuk Kyu Pak; Bong Ki Ryu; Pramod H. Borse; Jae Sung Lee; Takayuki Komatsu; Hae Jin Kim; Hyun Gyu Kim

2006-01-01

192

CO2 and potassium in the mantle: carbonaceous pelite melts from the trailing edge of a detached slab hybridizing in the mantle to ultrapotassic kamafugite  

Microsoft Academic Search

The ultrapotassic magmas from the Intra-Apennine and Roman provinces constitute worldwide endmembers in terms of K2O\\/Na2O, K2O content and CO2 degassing, and are associated with carbonatites. Group II kimberlites, which are geochemically similar but less extreme, occur on cratons stable since several 100 Ma. This geotectonic situation appears in strong contrast to the subduction setting of central Italy, where plate

M. W. Schmidt

2007-01-01

193

Petrological and experimental phase equilibria constraints on magma storage conditions beneath Cerro Uturuncu, Bolivia  

NASA Astrophysics Data System (ADS)

Volcanic unrest manifest as surface deformation detected with InSAR recently drew attention to Cerro Uturuncu, a dormant dacitic stratovolcano in the Bolivian altiplano that last erupted 271 ka. Magma intrusion in the mid to upper crust is thought to be responsible for the deformation calculated as 1-2 cm/yr central uplift rate between 1992 and 2006. Using petrological and experimental phase equilibrium experiments designed to replicate natural mineral assemblages, phase proportions and phase compositions, we aim to constrain the pre-eruptive pressure, temperature, fO2 and fH2O storage conditions of Uturuncu magmas. Plagioclase, orthopyroxene, biotite, titaniferous magnetite, ilmenite, apatite and a rhyolitic glassy matrix are ubiquitous in all 50 thin sections of Uturuncu lava samples studied. All of the lavas are porphyritic with examples of normal and reverse zoning in plagioclase and orthopyroxene phenocrysts. Biotite commonly has dehydration reaction rims. Magmatic temperatures of ~870°C and fO2s around NNO+1.3 have been estimated from coexisting Fe-Ti oxides. A water content of 3.6 wt%, similar to those calculated in melt inclusions using the by-difference method, was estimated using plagioclase-melt equilibria and, assuming the magma was water saturated, VolatileCalc indicates a magma storage pressure of at least 91 MPa. Several previous studies have experimentally investigated phase equilibria of silicic magmatic systems including Volcan San Pedro (Chile), Mount Unzen (Japan), and Fish Canyon and Mount St. Helens (USA). Compared to these systems, Uturuncu lavas have higher SiO2 by 1.0-4.2 wt%; higher K2O by 0.5-3.3 wt%; and Na2O lower by 1.9-2.8 wt%, and are unique in crystallising biotite in the absence of hornblende. Crystallisation experiments are being performed in cold-seal hydrothermal pressure apparatuses with two synthetic starting materials that replicate the bulk dacite and rhyolite glass chemistry of a glassy lava sample with a relatively low microlite content and a total crystallinity of 36 vol%. The dacite composition is SiO2 67.0 wt%, Al2O3 15.9 wt%, K2O 4.5 wt%, FeO 4.0 wt%, CaO 3.6 wt%, Na2O 2.1 wt%, MgO 1.5 wt%; the rhyolitic composition is SiO2 75.1 wt%, Al2O3 13.4 wt%, K2O 6.7 wt%, FeO 1.1 wt%, CaO 0.8 wt%, Na2O 2.2 wt%, MgO 0.2 wt%. Experiments are being conducted at temperatures between 800-900°C and pressures between 50-300 MPa at water saturated conditions. The results will be compared to natural samples to assess storage conditions of the 890-271 ka eruptions at Uturuncu, and the storage depths inferred today from geophysical data.

Muir, D. D.; Blundy, J. D.; Rust, A.; Brooker, R.

2011-12-01

194

Effect of Slag Composition on the Distribution Behavior of Pb between FetO-SiO2 (-CaO, Al2O3) Slag and Molten Copper  

NASA Astrophysics Data System (ADS)

The distribution behavior of Pb between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K (1200 °C) and p_{{{{O}}2 }} = 10^{ - 10} {{atm}} in view of the reaction mechanism of Pb dissolution into the slag. Furthermore, the lead capacity of the slag was estimated from the experimental results. The distribution ratio of Pb ( L Pb) decreases with increasing CaO content ( 6 mass pct) irrespective of Fe/SiO2 ratio (1.4 to 1.7). However, the addition of alumina into a slag with Fe/SiO2 = 1.5 linearly decreases the L Pb, whereas a minimum value is observed at about 4 mass pct Al2O3 at Fe/SiO2 = 1.3. The log L Pb continuously decreases with increasing Fe/SiO2 ratio, and the addition of Al2O3 (5 to 15 mass pct) into the silica-saturated iron silicate slag (Fe/SiO2 < 1.0) yields the highest Pb distribution ratio. This is mainly due to a decrease in the FeO activity even at silica saturation. The log L Pb linearly decreases by increasing the log (Fe3+/Fe2+) value. The Pb distribution ratio increases and the excess free energy of PbO decreases with increasing Cu2O content in the slag. However, from the viewpoint of copper loss into the slag, the silica-saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in the slag phase at a low Cu2O content. The lead capacity was defined in the current study and shows a linear correlation with the activity of FeO in a logarithmic scale, indicating that the concept of lead capacity is a good measure of absorption ability of Pb in iron silicate slags, and the activity of FeO can be a good basicity index in iron silicate slag.

Heo, Jung Ho; Park, Soo-Sang; Park, Joo Hyun

2012-10-01

195

Geochemical characteristics of the Miocene eolian deposits in China: Their provenance and climate implications  

NASA Astrophysics Data System (ADS)

In the Loess Plateau in northern China, the Quaternary loess-soil sequences, the Hipparion Red Earth of eolian origin (Red Clay), and the Miocene loess-soil sequences constitute a near-continuous terrestrial record of paleoclimates for the past 22 Ma. In this study, Miocene loess and paleosol samples from Qinan (QA-I) were analyzed for their major, trace, and rare earth element chemistry and compared with the Plio-Pleistocene samples from Xifeng with emphasis on their provenance and paleoclimatic implications. The results show similar geochemical signatures for the eolian deposits of different ages, and they are also comparable to the average composition of the upper continental crust. These suggest that the dust materials were all derived from well-mixed sedimentary protoliths which had undergone numerous upper crustal recycling processes. They also support the notion of broadly similar source areas and dust-transporting trajectories for different periods since the early Neogene. The slightly higher K2O, Fe2O3, and MgO concentrations and loss on ignition values and the lower Na2O content in the Miocene loess samples compared to their Quaternary counterparts are attributable to the finer grain size of the Miocene loess associated with weaker dust-carrying winds. In comparison with some loess in Europe and America with less extensive sources, eolian deposits from northern China show higher Cs and lower Zr and Hf content. This is attributable to the sorting processes from remoter sources during transportation and could be regarded as an indication of the desert origin of the loess deposits. Miocene paleosol samples show higher chemical index of alteration values and lower CaO, MgO, and Na2O concentrations than does the intervening loess, indicating stronger weathering of the paleosols. However, the moderate chemical weathering of the paleosol samples indicates a constant semiarid and subhumid climatic range in northern China since the early Miocene.

Liang, Meiyan; Guo, Zhengtang; Kahmann, A. Julia; Oldfield, Frank

2009-04-01

196

Papuan Ultramafic Belt (PUB) Ophiolite: Field Mapping, Petrology, Mineral chemistry, Geochemistry, Geochronology, And Experimental Studies Of The Metamorphic Sole  

NASA Astrophysics Data System (ADS)

The Papuan Ultramafic Belt (PUB) ophiolite in Papua New Guinea (PNG) is a large and well known section of former oceanic crust and upper mantle exposed in the western Pacific region. The PUB ophiolite was emplaced onto the southeast PNG continental crust possibly in the early Cenozoic . Detailed west-east transects during field mapping in the Musa-Kumusi divide area has shown that the Emo Metamorphics grade into amphibolites which grade up into the granulites which grade up into or are in contact with the ultramafic base of the PUB ophiolite. The ultramafics at the base of the PUB consist of harzburgites, and banded peridotites consisting of lherzolite, pyronenite and harzburgite layers. The harzburgites in the ultramafics have Fo92 olivine but there are small and correlated differences in Cr/Al ratio of both spinel and orthopyroxene and in CaO content. The pyroxenes in the lherzolite are very Ca-rich diopside and co-existing orthopyroxene with low CaO content, but higher than that of orthopyroxene in harzburgite. Temperature of equilibration by two pyroxene thermometry is 814-865oC, at 3 kbar. Hornblende is the dominant mineral phase in the granulites and amphibolites coexisting with olivine, orthopyroxene, clinopyroxene, plagioclase, ilmenite, magnetite. Lower SiO2, CaO, Al2O3 and higher MgO, TiO2, (Na2O+K2O), P2O5 contents of the granulites and the high MgO content and normative olivine (10% ) suggest that the sole granulites are essentially picritic in composition and are similar or transitional to the basic rocks of the Emo Metamorphics, and differ from the gabbroic rocks of the PUB ophiolite in lower TiO2, lower Na2O, higher Al2O3, lower FeO and lower P2O5 of the PUB, at similar MgO contents. A conventional A K-Ar, 40Ar-39Ar total fusion and incremental step-heating 40Ar-39Ar geochronological study on the metamorphic sole using amphiboles from emplacement-related granulites and amphibolites have been concluded. Sandwich melting experiments have been conducted to understand the mechanism for generation of boninite melts within the mantle wedge above subduction zone. Eruption of the Cape Vogel boninites and the emplacement of the PUB ophiolite and the formation of the metamorphic sole occurred in the Paleocene between 60 Ma to 58 Ma.

Lus, W. Y.; Green, D.; McDougall, I.; Eggins, S.; Davies, H.

2001-12-01

197

Variation of chemical composition in Australasian tektites from different localities in Vietnam  

NASA Astrophysics Data System (ADS)

One hundred and thirteen Australasian tektites from Vietnam (Hanoi, Vinh, Dalat, and Saigon areas) were analyzed for their major and trace element contents. The tektites are either of splash form or Muong Nong-type. The splash-form tektites have SiO2 contents ranging from 69.7 to 76.8 wt%, whereas Muong Nong-type tektites, which are considerably larger than splash-form tektites and have a blocky and chunky appearance, have slightly higher silica contents in the range of 74-81 wt%. Major-element relationships, such as FeO versus major oxides, Na2O versus K2O, and oxide ratio plots, were used to distinguish the different groups of the tektites. In addition, correlation coefficients have been calculated for each tektite group of this study. Many chemical similarities are noted between Hanoi and Vinh tektites from the north of Vietnam, except that the Hanoi tektites contain higher contents of CaO than Vinh; the higher content of CaO might be due to some carbonate parent material. Both Dalat and Saigon tektites have nearly similar composition, whereas the bulk chemistries of the tektites from Hanoi and Vinh appear different from those of Saigon and Dalat. There are differences, especially in the lower CaO and Na2O and higher MgO, FeO, for the tektites of Dalat and Saigon in comparison to that of Hanoi tektites. Furthermore, the Dalat and Saigon tektites show enrichments by factors of 3 and 2 for the Ni and Cr contents, respectively, compared to those of Hanoi and Vinh. The difference in chemistry between the North Vietnam tektites (Hanoi, Vinh) to that of South Vietnam tektites (Saigon, Dalat) of this study indicate that the parent material was heterogeneous and possibly mixing between different source rocks took place. Muong Nong-type tektites are enriched in the volatile elements such as Br, Zn, As, and Sb compared to the average splash-form tektites of this study. The chemical compositions of the average splash-form and Muong Nong-type tektites of this study closely resemble published data for average splash-form and Muong Nong-type indochinites, indicating that they have the same source. The trace element ratios Ba/Rb (2.7), Th/U (5.2), Th/Sc (1.3), Th/Sm (2.2), and the rare earth element (REE) abundances of this study show close similarities to those of average upper continental crust.

Amare, Kassa; Koeberl, Christian

2006-01-01

198

Comparison of CaO's effect on the fate of heavy metals during thermal treatment of two typical types of MSWI fly ashes in China.  

PubMed

Both grate and fluidized bed incinerators are widely used for MSW incineration in China. CaO addition for removing hazardous emissions from MSWI flue gas changes the characteristics of fly ash and affects the thermal behavior of heavy metals when the ash is reheated. In the present work, two types of MSWI fly ashes, sampled from both grate and fluidized bed incinerators respectively, were thermal treated at 1023-1323K and the fate of heavy metals was observed. The results show that both of the fly ashes were rich in Ca and Ca-compounds were the main alkaline matter which strongly affected the leaching behavior of heavy metals. Ca was mostly in the forms of Ca(OH)2 and CaCO3 in the fly ash from grate incinerator in which nascent fly ash particles were covered by Ca-compounds. In contrast, the content of Ca was lower in the fly ash from fluidized bed incinerator and Ca was mostly in the form of CaSO4. Chemical reactions among Ca-compounds caused particle agglomeration in thermal treated fly ash from grate incinerator, restraining the heavy metals volatilization. In thermal treated fly ash from fluidized bed incinerator, Ca was converted into aluminosilicates especially at 1323K which enhanced heavy metals immobilization, decreasing their volatile fractions as well as leaching concentrations. Particle agglomeration hardly affected the leaching behavior of heavy metals. However, it suppressed the leachable-CaCrO4 formation and lowered Cr leaching concentration. PMID:23800595

Hu, Hong-Yun; Liu, Huan; Shen, Wen-Qing; Luo, Guang-Qian; Li, Ai-Jun; Lu, Zhao-Ling; Yao, Hong

2013-06-22

199

Preparation, structure and bioactivity of xAu2O3·(100 - x)[P2O5·CaO] glass system  

NASA Astrophysics Data System (ADS)

Gold doped calcium phosphate glasses were prepared by the melting method. The structure of Au2O3-P2O5-CaO glasses is investigated using X-ray diffraction, infrared absorption and Raman scattering. The depth characterization of their structures is essential for the understanding of the properties of biocompatible materials. Thermal analysis DTA and TGA were also made to study behavior under different temperature regions and to see chemical changes versus time and temperature of these glasses. Bioactivity of the glasses was investigated in vitro by examining apatite formation on the surface of glasses treated in acellular simulated body fluid (SBF) with ion concentrations nearly equal to those in human blood plasma. Formation of bioactive apatite layer on the samples treated in SBF for 28 days at 37 °C was confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The effect of SBF soaking induces structural changes on the surface, reflected by the appearance of nano-crystalline particles agglomerated into micro-aggregates.

Regos, Adriana N.; Ardelean, I.

2011-12-01

200

NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on ?-Al2O3  

SciTech Connect

NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on ?-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the ?-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/?-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

2008-07-15

201

Identifying Source Heterogeneity of Italian K-rich Volcanism With Melt Inclusions: Roccamonfina Revisited  

NASA Astrophysics Data System (ADS)

Volcanism along the Tyrrhenian border of peninsular Italy is characterized by a wide compositional variety of potassic and ultrapotassic rocks, inferred to be related to metasomatic enrichment of mantle sources. Assessing the diversity of their source components and processes from erupted products remains challenging, since the bulk lavas rarely represent primary melts. Roccamonfina stratovolcano has erupted lavas and pyroclastics (e.g., Luhr and Giannetti, 1987; Giannetti and Luhr, 1983, 1990) that have traditionally been distinguished into a qtz- normative K-series (KS), and a Si-undersaturated high-K series (HKS). We have studied olivine-hosted (Fo=93- 87) melt inclusions of five representative mafic lavas (46-52 wt.% SiO2, 5-8 wt.% MgO, 1.4-6.3 wt.% K2O) from both series, aiming to assess the compositional diversity of primary melts. Relatively high CaO contents of HKS olivines (0.4-0.6 wt.%) are clearly distinct from those of KS olivines (0.03- 0.35 wt.%), irrespective of Fo contents, and appear to correlate with the degree of alkali enrichment. Heating- stage-homogenized MI (n=150) show strong compositional variations in each series. No systematic variations exist between the CaO contents of MI and host olivine, but highest K2O, P2O5, F concentrations were found in MI of HKS, and highest CaO (up to 19 wt.%), CaO/Al2O3, (up to 1.5), S and Cl in those of KS. Nevertheless, potassium contents of the primitive melts (MgO>7 wt.%) show a strong diversity in samples from both series (0.5-5 wt.% K2O in KS; 0.5-9 wt.% in HKS). Collectively, the MI data show that most of the bulk lava compositions reported so far do not represent primary melts, tending to overestimate SiO2, K2O, Na2O, and Al2O3, and underestimate MgO, CaO and TiO2. Importantly, bulk samples appear to be composed of multiple melts, suggesting contributions from heterogeneous mantle domains. MI in HKS olivines have the highest incompatible trace element contents. Both series show subduction-type LILE/HFSE ratios, but there is considerable variation in the degree of overall enrichment, particularly in the KS, which includes some anomalous depleted melts. Pb isotopic signatures obtained on MI show an extreme diversity (e.g., 207Pb/206Pb=0.8-0.86, 206Pb/204Pb=18.0-19.6) encompassing much of the range seen in the entire spectrum of Italian magmas. Despite some scatter, KS and HKS melts trend towards isotopically different crustal/sedimentary source components. Our findings are consistent with the hypothesis that distinct mantle domains below Roccamonfina were metasomatized by multiple agents with different properties. Similarities with signatures of the Roman Province suggests that the source of the HKS melts was affected by input from the Adria slab, whereas that of the KS melts was modified by the Ionian subduction in view of a greater affinity with Campanian magmas. We speculate that virtually simultaneous melting of a heterogeneous mantle column below Roccamonfina was promoted by upwelling hot asthenosphere in response to slab detachment, inferred from seismic tomography. References Luhr and Giannetti, 1987, CMP 95, 420-436; Giannetti and Luhr, 1983, CMP 84, 235-252; Giannetti and Luhr 1990, EPSL 101, 404-424.

van Bergen, M. J.; Nikogosian, I. K.

2007-12-01

202

[Study on carving workers of Chong xiu zheng he jing shi zheng lei bei yong ben cao (Revised Prepared Materia Medica Classified under Syndromes in Zhenghe Period) published by Huiming Xuan (Huiming Sanctum)].  

PubMed

The ancient carving workers have made a great contribution to the xylographic printing art in ancient China, so the studies on them are significant for a survey of ancient Chinese printing history, and for the identification of ancient Chinese books edition. Zheng lei ben cao published by Huiming Xuan (Huiming Sanctum) in the Jin and Yuan dynasties, which is the earliest extant edition of Zhenghe version system of Zheng lei ben cao and has important literature value. Thirty carving workers were involved in its printing process. On the whole, these workers had a relatively high technique and completed a remarkably fine work. In addition to lettering, 28 persons of them also made a total of 536 pages with 900 exquisite engraving illustrations on Chinese materia medica included in this book. Because of the high levels on carving, this precious book has been the representative of Pingshui edition, which has a great reputation but has very few works now. PMID:23363847

Liang, Fei; Li, Jian; Zhang, Wei; Zhang, Rui-Xian

2012-11-01

203

A study of natural and experimental metasomatic assemblages in an ultramafic-quartzofeldspathic metasomatic system from the haast schist, South Island, New Zealand  

NASA Astrophysics Data System (ADS)

The mineralogy of a metasomatic sequence formed between ultramafic and quartzofeldspathic protoliths from the Southern Alps of New Zealand consists of a forsterite-antigorite core surrounded concentrically by zones of antigorite-magnesite, magnesite-talc, talc, tremolite, chlorite and muscovite with discontinuous pods of albite associated with the muscovite zone. On the basis of trace element data the original ultramafite-schist contact is positioned between the present tremolite and chlorite zones. An experimental study of a metasomatic system was undertaken in an attempt to clarify diffusion relationships during the metasomatic event. To simulate the natural event, ultramafic and quartzofeldspathic natural starting materials were tightly packed in a gold tube with a graphite layer between to allow later identification of the original lithological interface. Run conditions were 450° C at 2 kb for 40 days. Phase dissolution and formation were analysed petrographically and component migration was examined with the electron-microprobe. The following hierarchical scheme of component migration, phase dissolution and phase formation is delineated: CO2 migrates from the schist into the ultramafite forming first the antigorite-magnesite zone and then the magnesite-talc zone at higher values of ?CO2. These zones are then partially overprinted by the formation of talc due to SiO2 metasomatism. The SiO2 is supplied from the schist by the dissolution of quartz and albite in the region adjacent to the ultramafite. The tremolite zone forms at the expense of the metasomatic talc zone upon the introduction of CaO from the schist into the ultramafite. Concurrent with tremolite formation, MgO migrates from the ultramafite into the schist to form the chlorite metasomatic zone. The growth of the chlorite zone causes dissolution of the pre-metasomatic micas and displaces K2O from the chlorite zone further into the schist. Displaced K2O and Na2O are responsible for the formation of the muscovite zone and the albitite pods.

Koons, Peter O.

1981-11-01

204

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation  

NASA Astrophysics Data System (ADS)

Epidote-bearing porphyritic dikes (whole rock analysis: SiO2 = 55-65 wt. %, MgO <2.1 wt. %, K2O <2.5 wt. %, Al2O3 >17 wt. %, Na2O + K2O = 5.7-9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388 ± 2 Ma and 389 ± 6 Ma. The porphyries contain phenocrysts of magmatic epidote ( Ps = 17-25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al2O3 = 12-16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than log fo2 = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK = 0.7-1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of 86Sr/87Sri = 0.709-0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.

Pribavkin, Sergey V.; Avdonina, Irina S.; Zamyatin, Dmitry A.

2013-02-01

205

[Determination of major elements in soil from cancer village by X-ray fluorescence spectrometry].  

PubMed

Many social problems arise from environmental pollution, cancer village is one of the many important problems caused by pollution. The authors selected a typical cancer village where 80-100 people died of cancer in the last five years, but there are only a total of 1 200 people in this village. The authors sampled soils from crops-planted areas and detected the major elements by X-ray fluorescence spectrometry. The results showed that the contents of SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 in soil of this village were 66.05%, 0.66%, 11.37%, 3.93%, 0.075%, 1.97%, 5.47%, 1.90%, 2.11% and 0.20% respectively; with the precision being +/- 0.20%, +/- 0.005%, +/- 0.10%, +/- 0.10%, +/- 0.005%, +/- 0.05%, +/- 0.04%, +/- 0.08%, +/- 0.02% and +/- 0.005% respectively, which showed that X-ray fluorescence spectrometry is a good method. PMID:19271523

Wei, Zhen-Lin; Li, He; Rui, Yu-Kui

2008-11-01

206

Straczekite, a new calcium barium potassium vanadate mineral from Wilson Springs, Arkansas.  

USGS Publications Warehouse

Straczekite occurs as a rare secondary mineral in fibrous seams, along with other V minerals (A.M. 64-713), in ore from the vanadium mine in Wilson Springs (formerly Potash Sulfur Springs), Garland County, Arkansas. It forms soft, thin laths of dark greenish black crystals up to 0.5 mm in length. Indexed XRD data are tabulated; strongest lines 3.486(100), 10.449(50), 1.8306(50), 1.9437(15) A; a 11.679, b 3.6608, c 10.636 A, beta 100.53o; space group C2/m, C2 or Cm. Chemical analysis gave V2O5 66.4, V2O4 15.3, Fe2O3 0.9, Na2O 0.4, K2O 1.8, CaO 2.5, BaO 5.5, H2O 7.2, = 100.0, leading to the formula (Ca0.39Ba0.31K0.33Na0.11)- 196(V4+1.59V5+6.31Fe3+0.10)O20.02(H2O)2.9; Dcalc. 3.21 g/cm3. A possible layer structure is discussed. The name is for J. A. Straczek, Chief Geologist at Union Carbide Corp.-R.A.H.

Evans, Jr, H. T.; Nord, G.; Marinenko, J.; Milton, C.

1984-01-01

207

Conversion of borate-based glass scaffold to hydroxyapatite in a dilute phosphate solution.  

PubMed

Porous scaffolds of a borate-based glass (composition in mol%: 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5), with interconnected porosity of approximately 70% and pores of size 200-500 microm, were prepared by a polymer foam replication technique. The degradation of the scaffolds and conversion to a hydroxyapatite-type material in a 0.02 M K2HPO4 solution (starting pH = 7.0) at 37 degrees C were studied by measuring the weight loss of the scaffolds, as well as the pH and the boron concentration of the solution. X-ray diffraction, scanning electronic microscopy and energy dispersive x-ray analysis showed that a hydroxyapatite-type material was formed on the glass surface within 7 days of immersion in the phosphate solution. Cellular response to the scaffolds was assessed using murine MLO-A5 cells, an osteogenic cell line. Scanning electron microscopy showed that the scaffolds supported cell attachment and proliferation during the 6 day incubation. The results indicate that this borate-based glass could provide a promising degradable scaffold material for bone tissue engineering applications. PMID:20057014

Liu, Xin; Pan, Haobo; Fu, Hailuo; Fu, Qiang; Rahaman, Mohamed N; Huang, Wenhai

2010-01-07

208

Phosphate glass fibres and their role in neuronal polarization and axonal growth direction.  

PubMed

Phosphate glass fibres with composition 50P(2)O(5)-30CaO-9Na(2)O-3SiO(2)-3MgO-(5-x)K(2)O-xTiO(2)mol.% (x=0, 2.5, 5, respectively coded as TiPS(0), TiPS(2.5) and TiPS(5)) were drawn following the preform drawing approach. A 20-day solubility test in bi-distilled water was carried out on glass fibres with different compositions and diameters ranging between 25 and 82 ?m. The results show that the glass composition, the initial fibre diameter and the thermal treatment are the main factors influencing the dissolution kinetics and that the fibres maintain their structural integrity and composition during dissolution. Biological tests were carried out on aligned TiPS(2.5) glass fibres using Neonatal Olfactory Bulb Ensheathing Cell Line (NOBEC) and Dorsal Root Ganglia (DRG) neurons. The fibres showed to be permissive substrates for cell adhesion and proliferation. The aligned configuration of the fibres seemed to provide a directional cue for growing axons of DRG neurons, which showed to sprout and grow long neurites along the fibre axis direction. These promising findings encourages further studies to evaluate the potential use of resorbable glass fibres (e.g.in combination with a nerve guidance tube) for the enhancement of the peripheral nerve healing with the role of supporting and guiding the cells involved in the nerve regeneration. PMID:22134161

Vitale-Brovarone, C; Novajra, G; Lousteau, J; Milanese, D; Raimondo, S; Fornaro, M

2011-11-20

209

Sodic granitoids and felsic gneisses associated with uranium-thorium mineralisation, Crockers Well, South Australia  

NASA Astrophysics Data System (ADS)

Thorian brannerite mineralisation at the Crockers Well prospect occurs in sodic granitic rocks and associated sodic felsic gneisses. Field, mineralogical and chemical data support the derivation of the granitic rocks from the gneisses by anatexis during high grade metamorphism. The sodic granitic rocks are largely peraluminous, contain high Na2O, low K2O, CaO, Rb, Ba, Sr and ferromagnesian elements, and variable but commonly high U, Th, Nb, Ce, Y and F values. Many geochemical parameters are inherited from the compositionally similar sodic felsic gneisses, which are interpreted to be metamorphosed analcime-rich volcano-sedimentary rocks of original intermediate-felsic (alkaline) affinites. Significant U-Th mineralisation is restricted to fractures and local breccia bodies which contain a mineral assemblage rich in quartz, F-bearing phlogopite and minor fluorapatite, sodic plagioclase, niobian rutile, thorian brannerite, monazite, muscovite, chlorite, tourmaline and fluorite. Certain genetic analogies are proposed with porphyry Cu and stockwork Mo deposits, with mineral deposition having occurred in mechanically-induced fractures and breccia bodies developed during sub-solidus cooling of the sodic granitoids.

Ashley, Paul M.

1984-01-01

210

Geochemical constraints on the petrogenesis of the Paleozoic granitoids of the Sierra de San Luis, Sierras Pampeanas, Argentina  

NASA Astrophysics Data System (ADS)

The Paleozoic granitoids of the Sierra de San Luis comprise the Ordovician tonalite suite (OTS; metaluminous to mildly peraluminous calcic tonalite granodiorites) and granodiorite granite suite (OGGS; peraluminous calcic to calc-alkaline granodiorite monzogranites), as well as the Devonian granite suite (DGS; peraluminous alkali-calcic monzogranites) and monzonite granite suite (DMGS; metaluminous alkali-calcic quartz monzonite monzogranite ± granodiorite, mildly peraluminous alkalicalcic monzogranites). The OTS has relatively high K2O, CaO, and YbN and low Cr, Ni, Ba, Sr, Rb/Sr, Sr/Y, and (La/Yb)N, as well as negative Eu/Eu?, high 87Sr/86Sr (0.70850 0.71114), and unradiogenic ?Nd(470Ma) (-5.3 to -6.0), which preclude an origin of variably fractionated mantle melts and favour a mafic lower crustal source. The OGGS consists of two granitoids: (1) high-temperature characterized by low Al2O3/TiO2, Rb/Sr, and (La/Yb)N, a smooth negative Eu/Eu?, and relatively high CaO and (2) low-temperature with high Al2O3/TiO2 and Rb/Sr, low CaO, (La/Yb)N, and Sr/Y, and negative Eu/Eu?. Melting of metagreywackes at pressures below 10 kbar with a variable supply of water could account for the chemistry of the high-T OGGS, whereas dehydration melting of biotite-bearing metasedimentary sources at low pressures is proposed for the low temperature OGGS. Melting of crustal sources relates to a contemporaneous mafic magmatism. Devonian magmatism is characterized by high Ba, Sr, K2O, Na2O, Sr/Y, and (La/Yb)N. Sources for the DGS include metasedimentary or metatonalitic protoliths. Biotite dehydration melting triggered by the addition of heat, supplied by mantle-derived magmas, is proposed. High Ba, Sr, LREE, MgO, Cr, Ni, Zr, and V of the monzonites suggest an enriched lithospheric mantle source. Low Yb and Y and high Sr and (La/Yb)N indicate a garnet-rich residual assemblage (P ? 10 kbar). Melts for the peraluminous rocks may have derived from a metasedimentary or metaigneous source at lower pressures in a process dominated by biotite consumption and plagioclase in the residue. The Ordovician granitoids are synkinematic with compressive deformation related to the early stages of Famatinian convergence. The Devonian magmatism is synkinematic with a system of shear zones that were active during the Achalian cycle.

de Luchi, M. G. López; Siegesmund, Siegfried; Wemmer, Klaus; Steenken, Andre; Naumann, Rudolf

2007-09-01

211

Röntgenographische Untersuchungen in den Systemen GeO 2 -{K 2 O,Rb 2 O,Cs 2 O}  

Microsoft Academic Search

Folgende GeO2-reiche Alkaligermanate wurden aufgefunden und röntgenographisch hinsichtlich der Gitterparameter charakterisiert: K2Ge8O17 und Rb2Ge8O17 (isotyp), Rb2Ge7O15 und Cs2Ge5O11. Die Existenz der seinerzeit als Pentagermanate beschriebenen isotypen Verbindungen von K, Rb, Cs und Tl sowie deren Gitterparameter werden bestätigt, doch ergab eine ausführliche Prüfung an gut kristallisierten Produkten zusammen mit den genau bestimmten Dichtewerten eine geringfügige Verschiebung im Verhältnis Me2O\\/GeO2, entsprechend

Elisabeth Modern; A. Wittmann

1966-01-01

212

Conductivity thresholds and glass structure in (K2O)x(GeO2)1-x glasses  

NASA Astrophysics Data System (ADS)

There are reports of conductivity thresholds with glass composition in solid electrolyte glasses. In the titled glass system, a seven order of magnitude increase in conductivity occurs at x > 0.10. The origin of the observation remains an open question. In titled glasses, we show that glass structure probed by the elastic behavior of its backbone shows two thresholds, a stress transition near x = 0.04 and a rigidity transition near x = 0.09. These elastic thresholds emerge from the reversibility window observed in calorimetric measurements, and in Raman scattering experiments that show scattering strength of the 520 cm-1 mode of 3-member rings to show a global maximum in the reversibility window. The pronounced increase of conductivity apparently occurs when backbones become flexible at x > 0.09, permitting K^+ ions to freely diffuse. The correlation between the electrical, thermal and optical properties of the present solid electrolyte glasses may well be a generic feature of these materials. Jain et al JNCS 222, 361 (1997). S. Chakravarty et al. J.C.M.P 17,L1-7 (2005).

Wang, Ninghua; Novita, Deassy; Boolchand, Punit

2007-03-01

213

Top-Seeded Flux Growth of Tetragonal GeO2.  

National Technical Information Service (NTIS)

Tetragonal single crystals of germanium dioxide have been grown using lithium oxide (Li2O), sodium oxide (Na2O), and potassium oxide (K2O) as solvents. Top-seeding methods yielded crystals superior to those GeO2 single crystals grown by the conventional f...

J. W. Goodrum

1970-01-01

214

Synthetic model of the asymmetric [Mn3CaO4] cubane core of the oxygen-evolving complex of photosystem II  

PubMed Central

The laboratory synthesis of the oxygen-evolving complex (OEC) of photosystem II has been the objective of synthetic chemists since the early 1970s. However, the absence of structural information on the OEC has hampered these efforts. Crystallographic reports on photosystem II that have been appearing at ever-improving resolution over the past ten years have finally provided invaluable structural information on the OEC and show that it comprises a [Mn3CaO4] distorted cubane, to which is attached a fourth, external Mn atom, and the whole unit attached to polypeptides primarily by aspartate and glutamate carboxylate groups. Such a heterometallic Mn/Ca cubane with an additional metal attached to it has been unknown in the literature. This paper reports the laboratory synthesis of such an asymmetric cubane-containing compound with a bound external metal atom, [(1)] . All peripheral ligands are carboxylate or carboxylic acid groups. Variable-temperature magnetic susceptibility data have established 1 to possess an S = 9/2 ground state. EPR spectroscopy confirms this, and the Davies electron nuclear double resonance data reveal similar hyperfine couplings to those of other MnIV species, including the OEC S2 state. Comparison of the X-ray absorption data with those for the OEC reveal 1 to possess structural parameters that make it a close structural model of the asymmetric-cubane OEC unit. This geometric and electronic structural correspondence opens up a new front in the multidisciplinary study of the properties and function of this important biological unit.

Mukherjee, Shreya; Stull, Jamie A.; Yano, Junko; Stamatatos, Theocharis C.; Pringouri, Konstantina; Stich, Troy A.; Abboud, Khalil A.; Britt, R. David; Yachandra, Vittal K.; Christou, George

2012-01-01

215

Modulated misfit structure of the thermoelectric [Bi0.84CaO2]2[CoO2]1.69 cobalt oxide.  

PubMed

The structure of the thermoelectric lamellar misfit cobalt oxide [Bi0.84CaO2]2[CoO2]1.69 has been refined using single crystal X-ray diffraction data. Using the four dimensional superspace formalism for aperiodic structures, the superspace group is confirmed P2/m(0delta1/2) (a1 = 4.9069(4), b1 = 4.7135(7), b2 = 2.8256(4), c1 = 14.668(5) A, beta1 = 93.32(1) degrees). The modulated displacements and site occupancies have been refined and are both compatible with the misfit character of the structure, and with a longitudinal modulation of the Bi-O layers of the structure. This modulation is similar to the corresponding one in the related Sr phase [Bi0.87SrO2]2[CoO2]1.82, but now oriented in the orthogonal direction. Because its incommensurate wavelength is locked with the aperiodicity of the misfit structure, it is possible to distinguish between the modulation parameters induced by the accommodation of both subsystems and those related to the longitudinal modulation of the Bi-O layers. In this original structure, two independent aperiodic phenomena coexist in an single crystallographic direction. A particular attention has been paid to the structural configuration of the CoO2 layer, in relation with other similar phases. The thermoelectric properties are probably directly related to the specific distortion of the compressed layer, but the different measured values for the Seebeck coefficient cannot be related to a significant modification of the CoO6 octahedra. PMID:18314946

Muguerra, Hervé; Grebille, Dominique; Guilmeau, Emmanuel; Cloots, Rudi

2008-03-04

216

Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution  

NASA Astrophysics Data System (ADS)

The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 °C to 1500 °C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.

Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

2013-02-01

217

Surface and chemical study of SiO{sub 2} {center_dot} P{sub 2}O{sub 5} {center_dot} CaO {center_dot} (MgO) bioactive glasses  

SciTech Connect

Glasses in SiO{sub 2} {center_dot} CaO {center_dot} P{sub 2}O{sub 5} and SiO{sub 2} {center_dot} CaO {center_dot} P{sub 2}O{sub 5} {center_dot} MgO systems have been prepared by a sol-gel synthesis procedure. The calcined glasses have been characterized by XRD, N{sub 2} adsorption, Hg porosimetry, XPS and TEM have been also subjected to in vitro tests (immersion in a simulated body fluid) to evaluate their bioactivity. The presence of magnesium in the glasses increases the surface area and porosity, but is retards the formation of an apatite layer on the surface of glasses in the in vitro test. The XPS reveals that the surfaces of the glasses are richer in phosphorus and poorer in calcium than the bulk, whereas the magnesium, if present, associates preferentially to phosphorus at the glass surface. The TEM shows the presence of apatite-like calcium phosphate domains in the magnesium -free glasses, which are barely detected in the glasses, which contain this element. These apatitic domains are proposed to be the nucleation centers for the crystallization of apatite in the in vitro tests.

Perez-Pariente, J.; Balas, F.; Vallet-Regi, M.

2000-03-01

218

End-member fluids for diamond formation and their possible sources  

NASA Astrophysics Data System (ADS)

Microinclusions in fibrous diamonds carry high density fluids (HDF) with compositions that vary between silicic, carbonatitic and saline end-members. Combining EPMA and FTIR data we can estimate the composition of each end-member. The silicic end-member composition (Udachnaya) comprises ~90 wt% silicates, 4% carbonate, 4% water and minor apatite. The saline end-member (Diavik, Canada) carries 51 wt% alkali halides, 12% carbonates and 37% water. Klein-BenDavid et al. (in review) defined two carbonatitic end-members. The low-Mg one carries ~75 wt% carbonates, 11% silicates, 5% halides, 2% apatite and 7% water; the high-Mg end-member carries similar proportions, except for the higher apatite: 78% carbonates, 9% silicates, 5% apatite, 2% halides and 6% water, but with much higher Mg/(Mg+Fe+Ca) ratio. The volatile-free oxides proportions of the most silicic microinclusions in an Udachnaya diamond are: 69 wt% SiO2; 14% Al2O3; 10% K2O, 2% Na2O, 1% CaO and P2O5 and minor FeO, TiO2, MgO, and Cl. The saline HDF carries 73 wt% KCl, 12% NaCl, 7% CaO, 2.5% MgO, 2.5% BaO, 1.5% FeO and 1.5% SiO2. In the low-Mg carbonatitic HDF calcium exceeds magnesium: ~21 wt% CaO, 18% FeO, 12% MgO, 22% K2O; 10% SiO2, 8% Na2O and minor TiO2, Al2O3, P2O5 and Cl, while in the high-Mg end-member MgO is the main oxide: ~29% MgO, 23% CaO, 7% FeO, 17% K2O, 8% SiO2, 9% Na2O, 2% P2O5 and Cl and minor BaO, TiO2, Cr2O3 and Al2O3 ( all values were calculated on volatile-free basis). Weiss et al., in a companion abstract, suggest that the four end-members form two arrays; one between the saline and the high-Mg carbonatitic compositions and the second between the silicic and the low-Mg carbonatitic ones. They further suggest that the first array represents a process that takes place in a peridotitic environment and the other in an eclogitic one. For example, the arrays may be formed by interaction of hydrous or saline fluids with carbonate-eclogite or with carbonate-peridotite. Safonov et al. (2007) suggested that a saline melt can interact with silicate minerals to form immiscible silicic melt that may later evolve into a carbonatitic HDF. In an ultramafic environment a saline melt may evolve along the array to high-Mg carbonatites without forming an immiscible silicate melt (Safonov, 2008). The source of the saline fluid is not clear. It may be present as discrete halides or as a grain-boundary phase in the carbonate-bearing rock, or it may form deeper in the mantle and migrate upwards either as a saline melt, or as a hydrous fluid that is concentrated enough to preclude interaction with the mantle rocks it traverses. A second alternative is to introduce the carbonate as the penetrating fluid in the form of carbonatitic melt. A third alternative involves the upward migration of CH4 and heavier hydrocarbons. Such a fluid should be stable in eclogitic or peridotitic environments, as long as the oxygen fugacity is low enough. During ascent, such fluids migrate to more oxidized regions and eventually will react with the mantle rocks to form C+H2O (Luth, 1993; Malkovets et al. 2007) and later CO2. In eclogitic rocks, the water will react to form a silicic HDF and the C may precipitate as diamond. In a peridotitic environment, at temperatures below the carbonate solidus, such water may leach and dissolve K and Cl from the rock and evolve into a saline HDF. Temperature increase or further diamond oxidation may initiate the formation of carbonatitic HDF's.

Navon, O.; Weiss, Y.; Klein-Bendavid, O.; Bell, D. R.

2009-04-01

219

A metallogenic survey of alkalic rocks of Mt. Somma-Vesuvius volcano  

Microsoft Academic Search

Summary   Somma-Vesuvius is an alkaline volcano whose products (pumice, scoria and lava) have alkaline (Na2O?+?K2O) contents between 6 and 16?wt%, Mg number 2 59–47?wt% and MgO 0–7.8?wt% (more than 50% of the samples have a content <2?wt%). Immobile-element ratios (Th\\/Yb, Ta\\/Yb,\\u000a Ce\\/Yb) indicate a shoshonitic character, while the K2O content (4–10?wt%) is characteristic of ultrapotassic rocks. The behavior of selected

A. Paone; R. A. Ayuso; B. De Vivo

2001-01-01

220

Oxidized, magnetite-series, rapakivi-type granites of Carajás, Brazil: Implications for classification and petrogenesis of A-type granites  

NASA Astrophysics Data System (ADS)

The varying geochemical and petrogenetic nature of A-type granites is a controversial issue. The oxidized, magnetite-series A-type granites, defined by Anderson and Bender [Anderson, J.L., Bender, E.E., 1989. Nature and origin of Proterozoic A-type granitic magmatism in the southwestern United States of America. Lithos 23, 19 52.], are the most problematic as they do not strictly follow the original definition of A-type granites, and approach calc-alkaline and I-type granites in some aspects. The oxidized Jamon suite A-type granites of the Carajás province of the Amazonian craton are compared with the magnetite-series granites of Laurentia, and other representative A-type granites, including Finnish rapakivi and Lachlan Fold Belt A-type granites, as well as with calc-alkaline, I-type orogenic granites. The geochemistry and petrogenesis of different groups of A-types granites are discussed with an emphasis on oxidized A-type granites in order to define their geochemical signatures and to clarify the processes involved in their petrogenesis. Oxidized A-type granites are clearly distinguished from calc-alkaline Cordilleran granites not only regarding trace element composition, as previously demonstrated, but also in their major element geochemistry. Oxidized A-type granites have high whole-rock FeOt/(FeOt + MgO), TiO2/MgO, and K2O/Na2O and low Al2O3 and CaO compared to calc-alkaline granites. The contrast of Al2O3 contents in these two granite groups is remarkable. The CaO/(FeOt + MgO + TiO2) vs. CaO + Al2O3 and CaO/(FeOt + MgO + TiO2) vs. Al2O3 diagrams are proposed to distinguish A-type and calc-alkaline granites. Whole-rock FeOt/(FeOt + MgO) and the FeOt/(FeOt + MgO) vs. Al2O3 and FeOt/(FeOt + MgO) vs. Al2O3/(K2O/Na2O) diagrams are suggested for discrimination of oxidized and reduced A-type granites. Experimental data indicate that, besides pressure, the nature of A-type granites is dependent of ƒO2 conditions and the water content of magma sources. Oxidized A-type magmas are considered to be derived from melts with appreciable water contents (? 4 wt.%), originating from lower crustal quartz-feldspathic igneous sources under oxidizing conditions, and which had clinopyroxene as an important residual phase. Reduced A-type granites may be derived from quartz-feldspathic igneous sources with a metasedimentary component or, alternatively, from differentiated tholeiitic sources. The imprint of the different magma sources is largely responsible for the geochemical and petrological contrasts between distinct A-type granite groups. Assuming conditions near the NNO buffer as a minimum for oxidized granites, magnetite-bearing granites formed near FMQ buffer conditions are not stricto sensu oxidized granites and a correspondence between oxidized and reduced A-type granites and, respectively, magnetite-series and ilmenite-series granites is not always observed.

Dall'Agnol, Roberto; de Oliveira, Davis Carvalho

2007-02-01

221

Major Element Geochemistry of Biofilms in a Silica-Precipitating Hot Spring  

NASA Astrophysics Data System (ADS)

Hydrothermal biofilm communities represent one of the best present-day representations of early microbial communities, dating back to 2.5 Ga, and possibly 3.8 Ga in the geologic record. Silica-precipitating hydrothermal springs have been thought to have great potential for biosignature preservation. The interactions of hydrothermal water, biofilms, and precipitated siliceous sinter, however, remain poorly constrained. To this end, we collected water and biofilm, as well as contextual sinter and rock samples from various hot springs in Yellowstone National Park. Here we focus on one hot spring in Sentinel Meadow (Lower Geyser Basin), with temperature and pH that vary from the source (93 C, pH 7.4) to the farthest of five collection points down channel (56 C, pH 8.2). Elemental analysis reveals that the biofilms are made up of from <1 to ~11 % dry wt. carbon and ~0.1 to 1% dry wt. nitrogen. Major element analysis via electron microprobe and complimentary x-ray fluorescence show that (excluding C and N from the total) SiO2 constitutes 86 to 94 % dry weight mass, with the rest made up of Al2O3 (3 to 8%), Na2O (1.7 to 3.7%), K2O (0.6 to 1.5%), and minor amounts of FeO, CaO, MgO, and TiO2 (<1%). Local sinter is SiO2 (97.5% dry wt.), Na2O (1.5%), and <1% Al2O3, FeO, K2O, CaO, MgO, and TiO2. In addition, sinter contains measurable amounts of carbon (1.4%) and nitrogen (0.2%). Discrepancies between the biofilm and sinter values show that the geochemical compositions of biofilms are not captured by the precipitating silica. If biofilms accumulated elements strictly from the water, then it would take as much as 440 L of water to supply 1 gram (dry wt) of biofilm with the elements contained therein, assuming complete uptake. This seems especially unlikely in the case of Al, which is quite dilute (~500 ppb), poses very little benefit nutritionally, and increases in concentration down channel. Other major element components also exhibit at least one, if not all, of these traits. A potential source of the elements found in biofilms is aeolian-deposited dust. Area country rock is dominated by siliceous volcanism, represented locally by rhyolite samples collected from Sentinel Meadow. With an average value of ~10 wt % Al2O3 for the surrounding country rock, it would take approximately 0.6 grams of the ground up rock as dust to account for the Al found in one gram of biofilm. The low Al2O3 content of the sinter indicates that the Al is not entombed from the biofilms. A hypothesis for the above discrepancies in Al (as well as other elements) is that dust deposited in the water is captured on the biofilm surfaces, and the biofilm community then breaks down the dust, utilizing any nutritionally or metabolically important elements, and either precipitating (for Si) or releasing (for Al) unnecessary elements.

Havig, J. R.; Shock, E. L.; Moore, G.

2007-12-01

222

Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran  

NASA Astrophysics Data System (ADS)

Mashhad granitoids in northeast Iran are part of the so-called Silk Road arc that extended for 8300 km along the entire southern margin of Eurasia from North China to Europe and formed as the result of a north-dipping subduction of the Paleo-Tethys. The exact timing of the final coalescence of the Iran and Turan plates in the Silk Road arc is poorly constrained and thus the study of the Mashhad granitoids provides valuable information on the geodynamic history of the Paleo-Tethys. Three distinct granitoid suites are developed in space and time (ca. 217-200 Ma) during evolution of the Paleo-Tethys in the Mashhad area. They are: 1) the quartz diorite-tonalite-granodiorite, 2) the granodiorite, and 3) the monzogranite. Quartz diorite-tonalite-granodiorite stock from Dehnow-Vakilabad (217 ± 4-215 ± 4 Ma) intruded the pre-Late Triassic metamorphosed rocks. Large granodiorite and monzogranite intrusions, comprising the Mashhad batholith, were emplaced at 212 ± 5.2 Ma and 199.8 ± 3.7 Ma, respectively. The high initial 87Sr/86Sr ratios (0.708042-0.708368), low initial 143Nd/144Nd ratios (0.512044-0.51078) and low ?Nd(t) values (- 5.5 to - 6.1) of quartz diorite-tonalite-granodiorite stock along with its metaluminous to mildly peraluminous character (Al2O3/(CaO + Na2O + K2O) Mol. = 0.94-1.15) is consistent with geochemical features of I-type granitoid magma. This magma was derived from a mafic mantle source that was enriched by subducted slab materials. The granodiorite suite has low contents of Y (? 18 ppm) and heavy REE (HREE) (Yb < 1.53 ppm) and high contents of Sr (> 594 ppm) and high ratio of Sr/Y (> 35) that resemble geochemical characteristics of adakite intrusions. The metaluminous to mildly peraluminous nature of granodiorite from Mashhad batholiths as well as its initial 87Sr/86Sr ratios (0.705469-0.706356), initial 143Nd/144Nd ratios (0.512204-0.512225) and ?Nd(t) values (- 2.7 to - 3.2) are typical of adakitic magmas generated by partial melting of a subducted slab. These magmas were then hybridized in the mantle wedge with peridotite melt. The quartz diorite-tonalite-granodiorite stock and granodiorite batholith could be considered as arc-related granitoid intrusions, which were emplaced during the northward subduction of Paleo-Tethys Ocean crust beneath the Turan micro-continent. The monzogranite is strongly peraluminous (Al2O3/(CaO + Na2O + K2O) Mol. = 1.07-1.17), alkali-rich with normative corundum ranging between 1.19% and 2.37%, has high initial 87Sr/86Sr ratios (0.707457-0.709710) and low initial 143Nd/144Nd ratios (0.512042-0.512111) and ?Nd(t) values (- 5.3 to - 6.6) that substantiate with geochemical attributes of S-type granites formed by dehydration-melting of heterogeneous metasedimentary assemblages in thickened lower continental crust. The monzogranite was emplaced as a consequence of high-temperature metamorphism during the final integration of Turan and Iran plates. The ages found in the Mashhad granites show that the subduction of Paleo-Tethys under the Turan plate that led to the generation of arc-related Mashhad granites in late-Triassic, finally ceased due to the collision of Iran and Turan micro-plates in early Jurassic.

Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

2013-06-01

223

Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho  

SciTech Connect

Geologic mapping in the Selway-Bitterroot Wilderness identified approximately 731 kmS of epizonal plutonic granitic rocks within the Bitterroot lobe of the Idaho batholith. From north to south, the intrusions are the Rock Lake Creek stock and the Whistling Pig, Running Creek, Bad Luck and Painted Rocks plutons. The stock and plutons consist of medium- to coarse-grained biotite and hornblende-biotite syenorgranite to monzogranite and quartz syenite capped by fine-grained biotite leucogranite. These rocks are intruded by late-synplutonic leucogranite dikes and post plutonic porphyritic rhyolite to rhyodacite and basalt dikes. The medium-grained granitic rocks are high in SiO2, K2O, Na2O, Ga, Th, U, W and Zr, but low in Al7O3, CaO, MgO, Cr, Ni, Co and V. Most of the granites are peraluminous. Rare-earth element (REE) plots (rock sample/chondrite) show enrichment in light REE over heavy REE with strong EU depletions. K-Ar biotite radiometric age determinations for medium-grained granites in all of the plutons range from approximately 51 Ma (Whistling Pig pluton) to 43.7 Ma (Painted Rocks pluton). Petrogenetic studies suggest that the plutons were rapidly emplaced to within 3.0 km of the paleosurface. The types, textures and color of the rocks result from devolatilization of the crystallizing melt and very low-grade hydrothermal alteration. The fluorine-rich melts are the fractionated with accumulate residue; they are considered to be anorogenic (A-type) granites intruded into the center of a metamorphic core complex.

Motzer, W.E.

1996-01-01

224

(210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil.  

PubMed

Activity profiles of excess (210)Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na(2)O, K(2)O, CaO, MgO, Al(2)O(3), P(2)O(5), Fe(2)O(3) and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm(-2)yr(-1) were obtained, and are compatible with the results of others studies. The (210)Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. PMID:21353731

Nery, José Reinaldo Cardoso; Bonotto, Daniel Marcos

2011-02-25

225

Classification and statistical analysis of mine spoils chemical composition from Oliete basin (Teruel, NE Spain)  

NASA Astrophysics Data System (ADS)

The Oliete basin (Early Cretaceous, NE Teruel, Spain) is one of the most important areas for the supply of mine spoils used as ball clays for the production of white and red stoneware in the Spanish ceramic industry of wall and floor tiles. This study corresponds to the second part of the paper published recently by Meseguer et al. (Environ Geol 2008) about the use of mine spoils from Teruel coal mining district. The present study shows a statistical data analysis from chemical data (major, minor and trace elements). The performed statistical analysis of chemical data included descriptive statistics and cluster analysis (with ANOVA and Scheffé methods). The cluster analysis of chemical data provided three main groups: C3 with the highest mean SiO2 content (66%) and lowest mean Al2O3 content (20%); C2 with lower SiO2 content (48%) and higher mean Al2O3 content (28%); and C1 with medium values for the SiO2 and Al2O3 mean content. The main applications of these materials are refractory, white and red ceramics, stoneware, heavy ceramics (including red earthenware, bricks and roof tiles), and components of white Portland cement and aluminous cement. Clays from group 2 are used in refractories (with higher kaolinite content, and constrictions to CaO + MgO and K2O + Na2O contents). All materials can be used in fine ceramics (white or red, according to the Fe2O3 + TiO2 content).

Meseguer, S.; Sanfeliu, T.; Jordán, M. M.

2009-02-01

226

Mineralogical, geochemical and radiological characterisation of Selmo Formation in Batman area, Turkey.  

PubMed

This work deals with the mineralogical, geochemical and radiological characterisations of Selmo Formation in Batman neighbourhood. The upper Miocene-Pliocene Selmo Formation is common in the centre of Batman and composed of carbonated sandy claystones and silty-sandy stone lenses. The common whole minerals of the samples are quartz, feldspars, calcite and dolomite. The clay minerals are smectite, illite, chlorite and mixed-layer clay (chlorite-smectite). The geochemical mean values of the samples are 51.7% SiO(2); 12.6% Al(2)O(3); 6.2% Fe(2)O(3); 3.6% MgO; 6.3% CaO; 1.1% Na(2)O; 1.7% K(2)O; 0.8% TiO(2); 0.2% P(2)O(5); 0.1% MnO; and 0.03% Cr(2)O(3). In addition, baseline maps for the concentrations of each radionuclide, the radium equivalent activity and the outdoor gamma dose rate distributions have been plotted for the study area. The mean activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs were determined to be 32, 24, 210 and 9 Bq kg(-1), respectively. The assessments of the radiological hazard indices, such as radium equivalent activity, absorbed dose rate in air, annual effective dose equivalent, excess lifetime cancer risk, external hazard index and internal hazard index, were calculated and compared with the internationally accepted reference values. This study shows that the concentrations of radioactivities in the measured samples were within the recommended safety limits and did not pose to be any significant source of radiation hazard. PMID:22316137

Isik, Umit; Damla, Nevzat; Akkoca, Dicle Bal; Cevik, U?ur

2012-02-09

227

Experiments on liquid immiscibility along tholeiitic liquid lines of descent  

NASA Astrophysics Data System (ADS)

Crystallization experiments have been conducted on compositions along tholeiitic liquid lines of descent to define the compositional space for the development of silicate liquid immiscibility. Starting materials have 46-56 wt% SiO2, 11.7-17.7 wt% FeOtot, and Mg-number between 0.29 and 0.36. These melts fall on the basaltic trends relevant for Mull, Iceland, Snake River Plain lavas and for the Sept Iles layered intrusion, where large-scale liquid immiscibility has been recognized. At one atmosphere under anhydrous conditions, immiscibility develops below 1,000-1,020°C in all of these compositionally diverse lavas. Extreme iron enrichment is not necessary; immiscibility also develops during iron depletion and silica enrichment. Variations in melt composition control the development of silicate liquid immiscibility along the tholeiitic trend. Elevation of Na2O + K2O + P2O5 + TiO2 promotes the development of two immiscible liquids. Increasing melt CaO and Al2O3 stabilizes a single-liquid field. New data and published phase equilibria show that anhydrous, low-pressure fractional crystallization is the most favorable condition for unmixing during differentiation. Pressure inhibits immiscibility because it expands the stability field of high-Ca clinopyroxene, which reduces the proportion of plagioclase in the crystallizing assemblage, thus enhancing early iron depletion. Magma mixing between primitive basalt and Fe-Ti-P-rich ferrobasalts can serve to elevate phosphorous and alkali contents and thereby promote unmixing. Water might decrease the temperature and size of the two-liquid field, potentially shifting the binodal (solvus) below the liquidus, leading the system to evolve as a single-melt phase.

Charlier, Bernard; Grove, Timothy L.

2012-07-01

228

Geochemistry of rock units at the potential repository level, Yucca Mountain, Nevada  

USGS Publications Warehouse

The compositional variability of the phenocryst-poor member of the 12.8 Ma Topopah Spring Tuff at the potential repository level was assessed by duplicate analysis of 20 core samples from the cross drift at Yucca Mountain, Nevada. Previous analyses of outcrop and core samples of the Topopah Spring Tuff showed that the phenocryst-poor rhyolite, which includes both lithophysal and nonlithophysal zones, is relatively uniform in composition. Analyses of rock samples from the cross drift, the first from the actual potential repository block, also indicate the chemical homogeneity of this unit excluding localized deposits of vapor-phase minerals and low-temperature calcite and opal in fractures, cavities, and faults. The possible influence of vapor-phase minerals and calcite and opal coatings on rock composition at a scale sufficiently large to incorporate these heterogeneously distributed deposits was evaluated and is considered to be relatively minor. Therefore, the composition of the phenocryst-poor member of the Topopah Spring Tuff is considered to be adequately represented by the analyses of samples from the cross drift. The mean composition as represented by the 10 most abundant oxides in wt. % or g/100 g is: SiO2, 76.29; Al2O3, 12.55; FeO, 0.14; Fe2O3, 0.97; MgO, 0.13; CaO, 0.50; Na2O, 3.52; K2O, 4.83; TiO2, 0.11; and MnO, 0.07. ?? 2002 Published by Elsevier Science Ltd.

Peterman, Z. E.; Cloke, P. L.

2002-01-01

229

Thermal Expansion Calculation of Silicate Glasses at 210°C, Based on the Systematic Analysis of Global Databases  

SciTech Connect

Thermal expansion data for more than 5500 compositions of silicate glasses were analyzed statistically. These data were gathered from the scientific literature, summarized in SciGlass© 6.5, a new version of the well known glass property database and information system. The analysis resulted in a data reduction from 5500 glasses to a core of 900, where the majority of the published values is located within commercial glass composition ranges and obtained over the temperature range 20 to 500°C. A multiple regression model for the linear thermal expansivity at 210°C, including error formula and detailed application limits, was developed based on those 900 core data from over 100 publications. The accuracy of the model predictions is improved about twice compared to previous work because systematic errors from certain laboratories were investigated and corrected. The standard model error (precision) was 0.37 ppm/K, with R² = 0.985. The 95% confidence interval for individual predictions largely depends on the glass composition of interest and the composition uncertainty. The model is valid for commercial silicate glasses containing Na2O, CaO, Al2O3, K2O, MgO, B2O3, Li2O, BaO, ZrO2, TiO2, ZnO, PbO, SrO, Fe2O3, CeO2, fining agents, and coloring and de-coloring components. In addition, a special model for ultra-low expansion glasses in the system SiO2-TiO2 is presented. The calculations allow optimizing the time-temperature cooling schedule of glassware, the development of glass sealing materials, and the design of specialty glass products that are exposed to varying temperatures.

Fluegel, Alex

2010-10-01

230

Geochemistry and evolution of the South Platte granite-pegmatite system, Jefferson County, Colorado  

NASA Astrophysics Data System (ADS)

The South Platte pegmatite district is well known for its significant enrichment in the rare earth elements (REE), Y, Nb, F, and for the exceptionally well-developed internal zonation of the complex pegmatites located within a reversely zoned portion of the Pikes Peak batholith. Chemical trends both within and between pegmatites define the behavior of major and trace elements and the role of F in the fractionation of the granitic magma and pegmatitic fluids, suggesting a new model for the evolution of the granite-pegmatite system. Whole-rock XRF and INAA analyses of the host Pikes Peak granite and quartz monzonite and pegmatite wall zones provide strong evidence that all three are related by differentiation. With increasing SiO 2, there is systematic enrichment in K 2O, Na 2O, and Rb, and depletion in CaO, MgO, FeO?, TiO 2, P 2O 5, Ba, Sr, and Sc. REE, Y, Zr, and Th were strongly partitioned out of the wall zone into the final residual fluids where they were concentrated up to an order of magnitude over levels in the granite. Within the district, there is also chemical zonation of F, Nb, Th, U, and REE between groups of pegmatites. Polyzonal quartz-core types typically contain more fluorite, samarskite, HREE-zircon, and yttrian-fluorite than their bizonal composite-core counterparts, which contain only sparse fluorite and allanite. The sequence of magmatic evolution involved: (1) a process of diffusive differentiation and fractional crystallization which produced a chemically stratified magma chamber with a hotter more mafic quartz monzonitic base and a more felsic, granitic top enriched in H 2O, F, HREE, Nb, and Y; (2) resurgence of the more mafic lower level crystal mush in to the upper more felsic part of the pluton; and (3) separation of pegmatitic fluids from the juxtaposed magmas giving rise to two compositionally distinct groups of pegmatites.

Simmons, Wm. B.; Lee, Maxie T.; Brewster, Renee H.

1987-03-01

231

[Rapid determination of major and trace elements in the salt lake clay minerals by X-ray fluorescence spectrometry].  

PubMed

A rapid multi-element analysis method for clay mineral samples was described. This method utilized a polarized wave-length dispersive X-ray fluorescence spectrometer--Axios PW4400, which had a maximum tube power of 4 000 watts. The method was developed for the determination of As, Mn, Co, Cu, Cr, Dy, Ga, Mo, P, Pb, Rb, S, Sr, Ni, ,Cs, Ta, Th, Ti, U, V, Y, Zn, Zr, MgO, K2O, Na2O, CaO, Fe2O3, Al2O3, SiO2 and so on. Thirty elements in clay mineral species were measured by X-ray fluorescence spectrometry with pressed powder pellets. Spectral interferences, in particular the indirect interferences of each element, were studied. A method to distinguish the interference between each other periodic elements in element periodic table was put forward. The measuring conditions and existence were mainly investigated, and the selected background position as well as corrected spectral overlap for the trace elements were also discussed. It was found that the indirect spectral overlap line was the same important as direct spectral overlap line. Due to inducing the effect of indirect spectral overlap, some elements jlike Bi, Sn, W which do not need analysis were also added to the elements channel. The relative standard deviation (RSD) was in the range of 0.01% to 5.45% except three elements Mo, Cs and Ta. The detection limits, precisions and accuracies for most elements using this method can meet the requirements of sample analysis in clay mineral species. PMID:20496720

Wang, Xiao-Huan; Meng, Qing-Fen; Dong, Ya-Ping; Chen, Mei-Da; Li, Wu

2010-03-01

232

Isotopic variation in the Tuolumne Intrusive Suite, central Sierra Nevada, California  

USGS Publications Warehouse

Granitoid rocks of the compositionally zoned Late Cretaceous Toulumne Intrusive Suite in the central Sierra Nevada, California, have initial87Sr/86Sr values (Sri) and143Nd/144Nd values (Ndi) that vary from 0.7057 to 0.7067 and from 0.51239 to 0.51211 respectively. The observed variation of both Sri and Ndi and of chemical composition in rocks of the suite cannot be due to crystal fractionation of magma solely under closed system conditons. The largest variation in chemistry, Ndi, and Sri is present in the outer-most equigranular units of the Tuolumne Intrusive Suite. Sri varies positively with SiO2, Na2O, K2O, and Rb concentrations, and negatively with Ndi, Al2O3, Fe2O3, MgO, FeO, CaO, MnO, P2O5, TiO2, and Sr concentrations. This covariation of Sri, Ndi and chemistry can be modeled by a process of simple mixing of basaltic and granitic magmas having weight percent SiO2 of 48.0 and 73.3 respectively. Isotopic characteristic of the mafic magma are Sri=0.7047, Ndi=0.51269 and ??18O=6.0, and of the felsic magma are Sri=0.7068, Ndi=0.51212 and ??18O=8.9. The rocks sampled contain from 50 to 80% of the felsic component. An aplite in the outer equigranular unit of the Tuolumne Intrusive Suite apparently was derived by fractional crystallization of plagioclase and hornblende from magma with granudiorite composition that was a product of mixing of the magmas described above. Siliceous magmas derived from the lower crust, having a maximum of 15 percent mantle-derived mafic component, are represented by the inner prophyritic units of the Tuolumne Intrusive Suite. ?? 1986 Springer-Verlag.

Kistler, R. W.; Chappell, B. W.; Peck, D. L.; Bateman, P. C.

1986-01-01

233

[Study on the determination of trace composition and impurity elements in kaolin with ICP-MS].  

PubMed

The direct determination method of trace composition, Fe2O3, TiO2, MnO, K2O, Na2O, CaO and MgO, and impurity elements, Pb, Cr, Cd, Cu and As, in kaolin was studied by using inductive coupled plasma mass spectrometry (ICP-MS). After the samples were dissolved completely in HF-HNO3 at low temperature, silicon was volatilized in the form of SiF4 and separated from the solution. Then the solution was continually evaporated to dry to get the solid substance which was dissolved by the nitric acid (1+3). The internal elements 45Sc, 115In and 205Tl were added on line and the effect of matrix, interface and fluctuation of instrument was overcome effectively by using internal standard calibration method. By choosing the optional operating parameters and appropriate isotopes of element to be detected, the influence of mass spectrometry interference was conquered effectively. The effect of temperature in samples preparation on the determination of arsenic was tested. The recovery for spiking sample is in the range from 95.0% to 101.0% and the relative standard deviation is in the range from 1.1% to 2.01%. In order to check the accuracy of the method, the kaolin standard reference material GBW03122 was also analyzed, and the analytical values conformed to standard values. This method has the characteristics of being simple, rapid and accurate, and can be used in the testing of trace composition and impurity elements in kaolin and ceramic product. PMID:19445238

Huang, Dong-Gen; Zhou, Wen-Bin; Liu, Lei; Quan, Shui-Qing; He, Zong-Jian; Wan, Jin-Bao

2009-02-01

234

Comparing results from two continental geochemical surveys to world soil composition and deriving Predicted Empirical Global Soil (PEGS2) reference values  

NASA Astrophysics Data System (ADS)

Analytical data for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from 3526 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper continental crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It can be demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more robust median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).

de Caritat, Patrice; Reimann, Clemens

2012-02-01

235

Major and trace element distributions in manganese nodules and micronodules as well as abyssal clay from the Clarion-Clipperton abyssal plain, Northeast Pacific  

NASA Astrophysics Data System (ADS)

The contents of seven major components (TiO2, Fe2O3, MgO, CaO, Na2O, K2O and P2O5) and 15 trace elements (Sc, V, Cr, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, Nd, Eu, Yb and Th) were determined by ICP-AE spectrometry in 27 samples of manganese nodules, micronodules as well as abyssal clay collected by dredging from an area of nearly 1,9802 nautical miles in the central Clarion-Clipperton abyssal plain at a depth of about 4,500 m. Statistical analyses were used to compare among individual as well as pooled datasets, in addition to different indicators such as La/Th, Ni/Cu and LREE/HREE ratios for the Clarion-Clipperton samples, as well as between these and corresponding values for the upper continental crust (UCC), North America Shale Composite (NASC), and igneous Indian and Pacific Mid-Ocean Ridge Basalts (MORBs). The results show significant correlations between major components in the Clarion-Clipperton samples and Pacific Ocean MORB, whereas trace elements (excepting Ni and Cu) correlate better with the UCC and NASC. There is also depletion in LREEs, together with a Ce negative anomaly for all Clarion-Clipperton samples. The nodule, micronodule and abyssal clay datasets each reveal typical clusters of components such as P2O5 and Y, La, Nd, Eu, Tb, or Ni and Cu. Compared to abyssal clay, the nodule as well as micronodules show significant enrichment in Ni and Cu; nevertheless, an essentially constant Ni/Cu ratio indicates that all samples come from the sediment surface. The distributions of major components as well as trace elements for the Clarion-Clipperton samples present, to different degrees, characteristics common to both the upper continental crust and Mid-Ocean Ridge Basalt, strongly implying a hydrothermal origin, most probably from East Pacific Rise material transported by the Pacific North Equatorial Current.

Duliu, O. G.; Alexe, V.; Moutte, J.; Szobotca, S. A.

2009-04-01

236

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

237

Porous and strong bioactive glass (13-93) scaffolds prepared by unidirectional freezing of camphene-based suspensions.  

PubMed

Scaffolds of 13-93 bioactive glass (6Na(2)O, 12K(2)O, 5MgO, 20CaO, 4P(2)O(5), 53SiO(2); wt.%) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700°C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1-7°C min(-1)) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3°C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7°C min(-1) (porosity=50±4%; average pore diameter=100 ?m), had a compressive strength of 47±5 MPa and an elastic modulus of 11±3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35±11 MPa and 8±3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones. PMID:21855661

Liu, Xin; Rahaman, Mohamed N; Fu, Qiang; Tomsia, Antoni P

2011-08-05

238

The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany  

NASA Astrophysics Data System (ADS)

The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al2O3, Na2O and Y contents and higher TiO2, CaO, K2O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ˜11 wt.% and LaN/YbN of 29 ± 2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher LaN/YbN of 42 ± 2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al2O3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

Shaw, Cliff S. J.; Woodland, Alan B.

2012-03-01

239

Alteration of plagioclase to nepheline in the Khariar alkaline complex, SE India: Constraints on metasomatic replacement reaction mechanisms  

NASA Astrophysics Data System (ADS)

At the Khariar alkaline complex in southeastern India, some tholeiitic amphibolites inter-layered with syenite and nepheline syenite show microtextural evidence of fenitization. Typical metasomatic textures include the replacement of plagioclase by vein nepheline and albitic-plagioclase or by symplectitic nepheline + albite + Na–Al-rich clinopyroxene. Whole rock mass balance calculations indicate that the fenitized variants gained alkalis (Na + K), some large ion lithophile elements (Sr, Rb and Ba) and high field strength elements like Zr and Hf during the metasomatic exchange. The plagioclase replacement textures can be explained by a fluid-mediated coupled dissolution–reprecipitation process whereby the infiltration of alkali-bearing fluid along grain boundaries and deformation-induced intragranular fractures led to the dissolution of the host plagioclase along an inward moving reaction interface. Na+ ions were introduced and Ca2 + ions removed by the fluid phase. The Al and Si released from the breakdown of the anorthite component of the plagioclase combined with Na+ from the fluid to precipitate nepheline + albitic-plagioclase or Na–Al-rich clinopyroxene. Reaction enhanced cracking during metasomatism due to local volume changes in the alteration zone produced a hierarchical system of fractures. Mass-balance calculations using the volume proportion of phases in the plagioclase replacement zones show that SiO2 and Al2O3 were broadly conserved during the replacement; there was significant loss of CaO (ca. 73%) and huge gains of Na2O and K2O. These results indicate that alkali and alkaline elements (Na, K and Ca) were exchanged freely between the fluid phase and the reaction zone whereas Si and Al released during plagioclase dissolution were consumed in the replacement zone itself to form nepheline and albite-rich plagioclase or Na–Al-rich clinopyroxene. The trace element and Sr–Nd isotope signature of the rocks indicate that the fenitizing fluids were derived from the nepheline syenites.

Upadhyay, Dewashish

2012-12-01

240

Natural radionuclide concentrations in granite rocks in Aswan and Central-Southern Eastern Desert, Egypt and their radiological implications.  

PubMed

Different types of granites, used extensively in local construction, were collected from five localities in Egypt, namely: Abu Ziran (Central Eastern Desert), Gabal El Maesala (Aswan) and three areas from Wadi Allaqi, (Gabal Abu Marw, Gabal Haumor and Gabal um Shalman), in the South Eastern Desert. Granite samples were studied radiologically, petrographically and geochemically. The contents of natural radionuclides ((226)Ra, (232)Th and (40)K) were measured in investigated samples by using gamma spectrometry [NaI (Tl) 3'×3']. The activity concentrations of (226)Ra, (232)Th and (40)K in the selected granite samples ranged from 9±0.5 to 111±7, 8±1 to 75±4 and 100±6 to 790±40 Bq kg(-1), respectively. The external hazard index (H(ex)), absorbed dose and annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The calculated radium equivalents were lower than the values recommended for construction materials (370 Bq kg(-1)). The excess lifetime cancer risks were also calculated. Petrographically, the granites studied are varied in the form of potash-feldspar, quartz, plagioclase, mica and hornblende. The accessory minerals are zircon, apatite and allanite. Geochemically, the chemical composition of the granite is studied especially for major oxides. They are characterized to have SiO(2), K(2)O, Na(2)O and Al(2)O(3) with depletion in CaO, MgO, TiO(2) and P(2)O(5). PMID:22147926

Issa, Shams A M; Uosif, M A M; Abd el-Salam, L M

2011-12-05

241

Late Ediacaran (605–580 Ma) post-collisional alkaline magmatism in the Arabian–Nubian Shield: A case study of Serbal ring-shaped intrusion, southern Sinai, Egypt  

NASA Astrophysics Data System (ADS)

The Serbal pluton is a late Neoproterozoic (605–580 Ma) post-collisional A-type granites in southern Sinai, Egypt (northernmost Arabian–Nubian Shield, ANS). It is characterized by discontinuous ring-shaped outcrops dislocated by later faulting. The pluton intrudes late Neoproterozoic metamorphic and high-K calc-alkaline rocks. The Serbal pluton mostly comprises an outer zone of alkali feldspar granite surrounding a core of peralkaline granite. Gradational and sharp contacts in the Serbal granites suggest that they were emplaced with a very short time interval, still before complete crystallization of the earlier batch. Serbal granites are highly evolved (75.98–78.52 wt.% SiO2) and display the typical geochemical characteristics of post-collisional A-type granites, namely high SiO2, Na2O + K2O, FeO*/MgO, Ga/Al, Zr, Nb, Ga and Y and low CaO, MgO, Ba, and Sr. They are rich in REE and have extreme Eu-negative anomalies (Eu/Eu* = 0.01–0.23). The chemical characteristics indicate that the peralkaline granite shares many features of granites with the tetrad REE effect. The Serbal pluton evolved through fractional crystallization of a parental magma derived through partial melting of a juvenile crustal protolith that had been extracted from a source having mantle geochemical and isotopic characteristics. The crystallization temperatures using Fe–Ti oxides of the Serbal granites point to their formation at high temperatures, up to 650–850 °C at a shallow depth of emplacement (<10 km).

Azer, Mokhles K.

2013-11-01

242

Silicate globules in kyanite from grospydites of the Zagadochnaya kimberlite pipe, Yakutia: The problem of the origin  

NASA Astrophysics Data System (ADS)

The results of complex study of silicate globules and ?-quartz paramorphs after coesite in kyanite from grospydites from the Zagadochnaya kimberlite pipe, Yakutia, using optical and scanning electron spectroscopy, electron and ion microprobes, LA ICP MS and Raman spectroscopy, are presented. The existence of radial fractures diverging from silicate globules into the matrix (kyanite) attests to the fact that the content of the globules is extremely condensed. A zonal structure is usually typical for globules: a coat and a core, which can be explicitly distinguished under the electron microscope, can be differentiated in them. Compositionally, the coat of the globule corresponds to potassium feldspar (wt %: 66.4 SiO2; 16.9 Al2O3; 0.4 FeO; 0.1 CaO; 0.2 Na2O; 14.7 K2O). The globules were also detected in which along with K, a high content of Na and Ca was also ascertained in the silicate coat. The globule coat is considerably enriched with Ba, La, Ce, Nb, and a number of other noncompatible elements as compared with xenolith minerals. The water content in globules is ˜0.6 wt %. As compared with the host mineral (kyanite), the core part of the globules is also enriched with Co, Ni, Zn, and Cu; their content in kyanite is negligibly low. The entire data collection attests to the fact that the formation of silicate globules could have been caused by interaction of the conservated fluid and/or water-silicate melt with the host mineral and crystalline inclusions of clinopyroxene and garnet with decreasing pressure during the transportation of grospydite xenoliths by the kimberlite melt to the Earth's surface.

Tomilenko, A. A.; Kovyazin, S. V.; Pokhilenko, L. N.; Sobolev, N. V.

2011-01-01

243

Origin of mafic enclaves and their feldspar phenocrysts in the El Capitan Granite, Yosemite National Park, California  

NASA Astrophysics Data System (ADS)

Mafic magmatic enclaves preserve evidence of interaction between mafic and felsic magmas in both volcanic and plutonic rocks, but the extent to which such interaction produces intermediate-composition rocks is in question. Magma mixing is viewed as one possible mechanism for their creation, yet contrasts in physical properties do not permit easy homogenization of mafic and felsic magmas. The El Capitan Granite of Yosemite Valley contains abundant mafic enclaves, enclave swarms, and schlieren, and is adjacent to a large, roughly coeval mafic complex known as the diorite of the Rockslides (DOTR) that has been suggested as an enclave source. Many of the mafic enclaves contain large (~ 0.5 to 1 cm) plagioclase phenocrysts similar in size to those in the host El Capitan Granite. We have performed geochemical and mineralogical analyses of the enclaves and host rocks in an effort to determine the source of the enclaves and whether the plagioclase phenocrysts could have been introduced into the enclaves by mixing from the host. Enclaves are broadly dioritic (55-65 wt% SiO2) and lie between the El Capitan Granite and the DOTR on most chemical plots. However, Na2O and MnO lie above, and CaO below, a simple mixing line between the two, precluding mixing as a complete explanation for their bulk compositions. The enclaves are distinctly more Na- and Mn-rich than the overall Sierran trend. Diffusion of elements is evident in chemical profiles taken perpendicular to the enclave/granite boundary. Na2O diffused out of the enclaves, so their overall enrichment in Na2O cannot be explained by addition from the host granite. The enclaves are typically enclosed by tonalitic haloes ~2 cm thick, perhaps owing to diffusion of K2O into the enclaves and diffusion of Na2O and SiO2 into the granite. Plagioclase phenocrysts within the mafic enclaves are similar in composition to those in the groundmass (An20-42) and are only slightly more calcic than plagioclase of the El Capitan Granite. Plagioclase crystals found in the DOTR have much higher anorthite contents (An74-90) than any found in the enclaves. The phenocrysts contain Mn-rich ilmenite inclusions that are not present in the El Capitan Granite or DOTR; these and other mineral inclusions match the compositions of the minerals composing the mafic enclaves. The sodic nature of the enclave phenocrysts and the lack of calcic cores similar in composition to DOTR feldspars further imply that the phenocrysts were not introduced from the host granite. These data indicate enclaves did not result from mixing of the El Capitan Granite and mafic rocks of the DOTR, but most likely arose from andesitic magmas that are not otherwise found in the Sierra Nevada batholith. Andesites with similar compositions are found at Cascade volcanoes.

Ireland, K. R.; Glazner, A. F.; Mills, R. D.

2011-12-01

244

The Behavior of Pyroxenes During Partial Melting of Pyroxenite and Lherzolite in the Mantle: An Experimental and Numerical Study  

NASA Astrophysics Data System (ADS)

Pyroxenes are the primary phases involved in partial melting of peridotite and pyroxenite lithologies in the upper mantle. In order to better understand the grain-scale processes of pyroxene melting and their effects on major and trace element distributions during magma generation, we carried out a series of kinetic melting experiments using reaction couple method. Partial melting experiments were conducted at 1340° C and 1.5 GPa for 72 hrs using reaction couples formed by juxtaposing pre-synthesized rods of orthopyroxenite (90% opx, 5% olivine, 5% melt) against clinopyroxenite (90% cpx + 10% melt). These laboratory experiments were supplemented by numerical simulations of partial melting in binary and ternary systems. Reaction between orthopyroxenite and clinopyroxenite at 1340° C and 1.5GPa results in a reactive boundary layer (RBL, 240 ? m after 72 hrs) that consists of euhedral olivine (35%), cpx (45%), and melt (20%). The RBL is located on the orthopyroxenite side of the original interface. The grain sizes of ol and cpx in the RBL are significantly larger than those in the orthopyroxenite and the clinopyroxenite. Clinopyroxene compositions vary systematically across the RBL, for example the Na2O and TiO2 content decrease from 1.05% and 0.35%, respectively, in the clinopyroxenite to 0.83% and 0.14% at the orthopyroxenite-RBL interface. The melt is concentrated in the RBL and appears to localize in those areas where olivine grains are more densely accumulated. The average melt in the RBL is a ne-normative alkali basalt (10.6% MgO, 49.2% SiO2, 4.7% Na2O, 0.28% K2O) and has relatively high Al2O3 (15.5%) and CaO (10.7%). The characteristics of increasing grain size and varying cpx and melt compositions in the RBL are very similar to those observed in our clinopyroxenite-harzburgite partial melting experiments [1], consistent with the grain-scale melting processes that involve dissolution of opx at the orthopyroxenite-RBL interface, precipitation of ol and new cpx within the RBL, and production of Na2O-Al2O3-SiO2-rich melts in that region. This dissolution and reprecipitation process, due to two very different time-scales of crystal-melt interaction in partially molten systems, is reproduced in our numerical simulations of partial melting of bio-mineralic rocks in binary and ternary systems, and is likely to occur during lherzolite and pyroxenite partial melting in the laboratory and nature. One of the important consequences of cpx reprecipitation during peridotite and pyroxenite partial melting is the significant reduction in diffusive reequilibration time between the cpx and the surrounding melt, since diffusion coefficients of trace elements such as REE, U, and Th in cpx are much smaller than those of major elements in cpx and melt. The rate of cpx reprecipitation is dominated by the rate of chemical diffusion of the major components in cpx. This dissolution and reprecipitation process may help to explain the apparent equilibrium melting trends observed in some slab derived magmas that were produced at relatively low temperatures. The mechanisms outlined above can also be used to better understand the melting process of lherzolite and pyroxene-rich lithologies in the upper mantle and could partially explain the petrogenesis of high Na2O-Al2O3-SiO2 magmas, without the involvement of an eclogite component in the source region. [1] Lo Cascio et al., GRL, 31, L16605, doi: 10.1029/2004GL020602

Lo Cascio, M.; Liang, Y.

2004-12-01

245

Identification of Oxidized Amino Acid Residues in the Vicinity of the Mn4CaO5 Cluster of Photosystem II: Implications for the Identification of Oxygen Channels within the Photosystem  

PubMed Central

As a light-driven water-plastoquinone oxidoreductase, Photosystem II produces molecular oxygen as an enzymatic product. Additionally, under a variety of stress conditions, reactive oxygen species are produced at or near the active site for oxygen evolution. In this study, Fourier-transform ion cyclotron resonance mass spectrometry was used to identify oxidized amino acid residues located in several core Photosystem II proteins (D1, D2, CP43 and CP47) isolated from spinach Photosystem II membranes. While the majority of these oxidized residues (81%) are located on the oxygenated solvent-exposed surface of the complex, several residues on the CP43 protein (354E, 355T, 356M and 357R) which are in close proximity (<15 Å) to the Mn4CaO5 active site are also modified. These residues appear to be associated with putative oxygen/reactive oxygen species exit channel(s) in the photosystem. These results are discussed within the context of a number of computational studies which have identified putative oxygen channels within the photosystem.

Frankel, Laurie K.; Sallans, Larry; Limbach, Patrick A.; Bricker, Terry M.

2012-01-01

246

Structural characterization of glass-ceramics made from fly ash containing SiO2-Al2O3-Fe2O3-CaO and analysis by FT-IR-XRD-SEM methods  

NASA Astrophysics Data System (ADS)

The glass-ceramics has been proposed as a useful recycling fly ash from thermal power plants. In this study, C type fly ash containing SiO2-Al2O3-Fe2O3-CaO has been sintered to form glass-ceramic materials at different temperatures between 850 °C and 1050 °C after using powder processing based on milling and powder compaction without inorganic additives. The effect of firing temperatures between 850 °C and 1050 °C on mineralogy and microstructure of sintered samples is reported. The Fourier Transform Infrared Spectra (FT-IR), Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were applied on the sintered powder form. From the XRD results, the amount of quartz decreases on sintering, when the sintering temperature increases. On the basis of SEM observations, new crystallites structure developed in the microstructures of the C type of fly ash samples and the glassy region decreased at the crystallization temperature.

Yilmaz, G.

2012-07-01

247

Immobilization of High-Level Wastes into Sintered Glass: 1. Hot Pressing Process.  

National Technical Information Service (NTIS)

In order to immobilize the high-level radioactive wastes from the reprocessing, fuel elements borosilicate glass was adopted. Sintering experiments are described with the variety VG 98/12 (SiO2, TiO2, Al2O3, B2O3, MgO, CaO and Na2O) (which does not presen...

D. O. Russo N. Messi de Bernasconi M. A. Audero

1987-01-01

248

Effect of surface morphology of macro-scale perlite particles on adsorption process of Malachite Green dye  

Microsoft Academic Search

Perlite is a mineral compound. It is a mixture of SiO2, Al2O3, Na2O, K2O, Fe2O3 and so on. Its high porosity and low density cause that it is being used as an adsorbent to remove organic and inorganic pollutants from wastewater in many researches. But its capacity depends on its structure as an adsorbent. In this research, the effect of

Khashayar Badii; Farrokh-Legha Amini; Soodeh-Sadat Rasoli Ahari

2011-01-01

249

Monzonitic plutons, California, and a model for generation of alkali-rich, near silica-saturated magmas  

Microsoft Academic Search

Petrochemical data suggest that early Mesozoic alkali-rich monzonite plutons in California were generated by partial melting of a garnet-bearing, virtually feldspar-free source which was rich (compared to abyssal basalt or sub-oceanic mantle peridotites) in LIL elements. These monzonites are characterized by high Na2O+K2O (near 10 wt% total) and Sr (1000 to 2000 ppm), moderate SiO2 (53 to 63 wt%), steep

Calvin F. Miller

1978-01-01

250

Belmore Volcanic Province, northeastern New South Wales, and some implications for plume variations along Cenozoic migratory trails  

Microsoft Academic Search

The little known Belmore Volcanic Province, near Baryugil, northeast New South Wales, is a half-eroded structure, 21 – 19.5 Ma in age. The remnants occupy 140 km and suggest an original volcanic field ?14 km in volume. The eruptive sequence, fed by dykes, plugs and compound centres ranges up to 350 m thick. Sodic, metaluminous trachytes predominate and include ne and qtz normative types, with Na2O\\/K2O

F. L. Sutherland; I. T. Graham; H. Zwingmann; R. E. Pogson; B. J. Barron

2005-01-01

251

Experimental study of partitioning of tantalum, niobium, manganese, and fluorine between aqueous fluoride fluid and granitic and alkaline melts  

Microsoft Academic Search

This study presents a new set of quantitative experimental data on the partitioning of Ta, Nb, Mn, and F between aqueous F-bearing fluid and water-saturated, Li- and F-rich haplogranite melts with varying alumina\\/alkali content at T = 650-850 °C and P = 100 MPa. The starting homogeneous glasses were preliminary obtained by melting of three gel mixtures of K2O-Na2O-Al2O3-SiO2 composition

G. P. Borodulin; V. Yu. Chevychelov; G. P. Zaraysky

2009-01-01

252

Phase Equilibrium Experiments at 0.5 GPa and 1100-1300 deg. C on a Basaltic Andesite From Arenal Volcano, Costa Rica  

Microsoft Academic Search

The on-going eruption of Arenal volcano has undergone complex changes in eruptive behavior. To investigate pre-eruptive crustal processes, we conducted phase equilibrium experiments on a basaltic andesite. The anhydrous synthetic starting mix has a Mg# of 52 and concentrations of SiO2, Na2O and K2O of 55, 3.0 and 0.6 wt.%, respectively. Al(OH)3 was used to obtain bulk water concentrations of

M. Pertermann; C. C. Lundstrom

2004-01-01

253

Relationships between Campi Flegrei and Mt. Somma volcanism: evidence from melt inclusions in clinopyroxene phenocrysts from volcanic breccia xenoliths  

Microsoft Academic Search

Summary   We present compositions of reheated melt inclusions in clinopyroxene phenocrysts from three mafic xenoliths in Breccia Museo,\\u000a Campi Flegrei, Italy. Melt inclusion compositions are remarkably different from the compositions of known contemporary Campi\\u000a Flegrei lavas, being significantly enriched in K2O and depleted in Na2O. Some differences are also evident in FeO* (total Fe as FeO) and TiO2 contents. The

L. V. Danyushevsky; A. Lima

2001-01-01

254

Multistage metasomatism of diamondiferous eclogite xenoliths from the Udachnaya kimberlite pipe, Yakutia, Siberia  

Microsoft Academic Search

The primary garnet (pyrope-almandine)-omphacite (Cpx 1, 6.5–7 wt% Na 2O)-sulfide (Fe-Ni-Co mss) assemblage of the two diamondiferous eclogite xenoliths studied (U33\\/1 and UX\\/1) experienced two mantle metasomatic events. The metasomatic event I is recorded by the formation of platy phlogopite (~ 10 wt% K 2O), prior to incorporation of the xenoliths in the kimberlite. The bulk of the metasomatic alteration, consisting of

Kula C. Misra; Mahesh Anand; Lawrence A. Taylor; Nikolai V. Sobolev

2004-01-01

255

Early Proterozoic crustal evolution: Geochemical and NdPb isotopic evidence from metasedimentary rocks, southwestern North America  

Microsoft Academic Search

Early Proterozoic (1.8-1.7 Ga) metasedimentary rocks in northern New Mexico and southern Colorado, USA, can be divided into turbidite successions (commonly volcanogenic) associated with mafic\\/felsic metavolcanic successions (e.g., Irving Fm.) and stable shelf quartzite-pelite successions of shallow marine origin (e.g., Hondo Gp.). Metapelites from the turbidite successions reported here have low K 2 O\\/Na 2 O, low Th\\/U (<3.0), low

S. M. McLennan; S. R. Hemming; S. R. Taylor; K. A. Eriksson

1995-01-01

256

Synthesis, Ion-exchange, Structural Characterization and Adsorption of K, Na-FER Type Zeolite  

Microsoft Academic Search

Synthesis of K, Na -FER type zeolite wasstudied in the reactant system ofK 2O-–Na 2O-–Al 2O 3-–SiO 2-–CO 3-–HCO 3-ndash;H 2O.Sodium silicate, silica sol andfumed silica were tested as the silica source, andsolid aluminum sulfate, aluminum hydroxide andmeta-kaolinite as the alumina source. The startingmaterials, the composition of the reactant, and thesynthesis temperature greatly influence the phasescrystallized. A pure phase of

Yingcai Long; Minghua Ma; Yaojun Sun; Huiwen Jiang

2000-01-01

257

Petrochemical variations among mildly peralkaline (comendite) obsidians from the oceans and continents  

Microsoft Academic Search

Eleven new analyses and modes of comendite obsidians are presented, and compared with all available data on similar rocks. Most specimens are aphyric or contain only sparse phenocrysts, most commonly alkali feldspar. The oxides SiO2, Al2O3, Na2O and K2O total over ninety percent by weight in all analyses. Iron, as FeO, is the only other constituent rising above one percent

D. K. Bailey; R. MacDonald

1970-01-01

258

Characterization and Origin of Aluminous A-type Granites from the Lachlan Fold Belt, Southeastern Australia  

Microsoft Academic Search

The term ‘A-type’ was proposed in an abstract by A-type granites, such as those of the Lachlan Fold Belt, should be Loiselle & Wones (1979) to distinguish ‘mildly alkaline’ defined as ‘aluminous A-type’ granites and should not be grouped rocks (high K2O + Na2O) from typical ‘calc-alkaline’ (I- with peralkaline granites. The Lachlan Fold Belt aluminous type) rocks. Other distinctive

P. L. KING; A. J. R. WHITE; B. W. CHAPPELL; C. M. ALLEN

1997-01-01

259

Evolution of the trachydacite and pantellerite magmas of the bimodal volcanic association of Dzarta-Khuduk (Central Mongolia): evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Using various methods of melt inclusion investigation, including electron and ion microprobe techniques, we estimated the composition, evolution, and formation conditions of melts producing the trachydacites and pantellerites of the Late Paleozoic bimodal volcanic association of Dzarta-Khuduk, CentralMongolia. Dzarta Huduk paleovolcano occupies an area of more than 120 square kilometers. A sequence of felsic agpaitic volcanics rests on subalkali basalts and consists of intercalating alkaline trachydacites, pantellerites, and comendites. Their mineralogical and chemicall characteristics correspond to silicic peralkaline rocks of the K-Na series with an agpaitic index of >1 and high contents of F, Zr, Li, Rb, and REE. Primary crystalline and melt inclusions were detected in anorthoclase from trachydacites and quartz from pantellerites and pantelleritic tuffs. Among the crystalline inclusions, we identified hedenbergite, fluorapatite, and pyrrhotite in the trachydacites and F-arfvedsonite, fluorite, ilmenite, and the rare REE diorthosilicate chevkinite in the pantellerites. Melt inclusions in anorthoclase from the trachydacites are composed of glass, a gas phase, and daughter minerals (F-arfvedsonite, fluorite, villiaumite, and anorthoclase rim on the inclusion wall). Melt inclusions in quartz from the pantellerites are composed of glass, a gas phase, and a fine-grained salt aggregate consisting of Li, Na, and Ca fluorides (griceite, villiaumite, and fluorite). Melt inclusions in quartz crystalloclasts from the pantelleritic tuffs are composed of homogeneous silicate glasses. The phenocrysts of the trachydacites and pantellerites crystallized at temperatures of 1060-1000°C. During thermometric experiments with quartz-hosted melt inclusions from the pantellerites, the formation of immiscible silicate and salt (fluoride) melts was observed at a temperature of 800°C. Homogeneous melt inclusions in anorthoclase from the trachydacites have both trachydacite and rhyolite compositions (wt %):68-70 SiO2, 12-13 Al2O3, 0.34-0.74 TiO2, 5-7 FeO, 0.4-0.9 CaO, and 9-12 Na2O + K2O. The agpaitic index ranges from 0.92 to 1.24. The glasses of homogenized melt inclusions in quartz from the pantellerites and pantelleritic tuffs have rhyolitic compositions. Compared with the homogeneous glasses trapped in anorthoclase of the trachydacites, quartz-hosted inclusions from the pantellerites show higher SiO2 (72-78 wt %) and lower Al2O3 contents (7.8-10.0 wt %). They also contain 0.14-0.26 wt % TiO2, 2.5-4.9 wt % FeO, 9 -11 wt % Na2O + K2O, and 0.9-0.15 wt % CaO and show an agpaitic index of 1.2-2.05. Homogeneous melt inclusions in quartz from the pantelleritic tuffs contain 69-72 wt % SiO2. The contents of other major components, including TiO2, Al2O3, FeO, and CaO, are close to those in the homogeneous glasses of quartz-hosted melt inclusions in the pantellerites. The contents of Na2O + K2O are 4-10 wt %, and the agpaitic index is 1.0-1.6. The glasses of melt inclusions from each rock group show distinctive volatile compositions. The H2O content is up to 0.08 wt % in anorthoclase of the trachydacites, 0.4-1.4 wt % in quartz of the pantellerites, and up to 5 wt % in quartz of the pantelleritic tuffs. The content of F in the glasses of melt inclusions in the phenocrysts of the trachydacites is no higher than 0.67 wt %, and up to 1.4-2.8 wt % in quartz from the pantellerites. The Cl content is up to 0.2 wt % in the glasses of melt inclusions in the minerals of the trachydacites and up to 0.5 wt % in the glasses of quartz-hosted melt inclusions from the pantellerites. The investigation of trace elements in the homogenized glasses of melt inclusions in minerals showed that the trachydacites and pantellerites were formed from strongly evolved rare-metal alkaline silicate melts with high contents of Li, Zr, Rb, Y, Hf, Th, U, and REE. The analysis of the composition of homogeneous melt inclusions in the minerals of the above rocks allowed us to distinguish magmatic processes resulting in the enrichment of these rocks in trace and rare earth element

Andreeva, I.

2012-04-01

260

K-rich glass-bearing wehrlite xenoliths from Yitong, Northeastern China: petrological and chemical evidence for mantle metasomatism  

NASA Astrophysics Data System (ADS)

Ultramafic xenoliths in Cenozoic alkali basalts from Yitong, northeast China comprise three types in terms of their modal mineralogy: lherzolite, pyroxenite and wehrlite. The wehrlite suite always contains interstitial pale/brown glass which occupies several per cent by volume of the whole rock. The texture of the wehrlites is porphyroclastic with some large strained grains of olivine (0.5 1 mm) scattered in a very fine grained matrix (0.1 mm), implying a metamorphic origin for the protolith rather than an igneous origin. The host minerals are compositionally zoned, showing evidence of reaction with a melt. Petrological evidence for resorption of spinel (lherzolite) and orthopyroxene (wehrlite) by infiltrating melt further supports the hypothesis that the wehrlites result from interaction between a partial melting residue and a melt, which preferentially replaced primary spinel, Cr-diopside and enstatite to produce secondary clinopyroxene (cpx) + olivine (ol) ± chromite ± feldspar (fd). The composition of the mineral phases supports this inference and, further indicates that, prior to melt impregnation, the protoliths of these wehrlites must have been subjected to at least one earlier Fe-enrichment event. This explanation is consistent with the restricted occurrence of glasses in the wehrlite suite. The glass is generally associated with fine-grained (0.1 mm) minerals (cpx+ol+chromite ±fd). Electron microprobe analyses of these glasses show them to have high SiO2 content (54 60 wt%), a high content of alkalis (Na2O, 5.6 8.0%; K2O, 6.3 9.0%), high Al2O3 (20 24%), and a depletion in CaO (0.13 2.83%), FeO (0.89 4.42%) and MgO (0.29 1.18%). Ion probe analyses reveal a light rare earth element-enrichment in these glasses with chondrite normalised (La)n = 268 480. The high K2O contents in these glasses and their mode of occurrence argue against an origin by in-situ melting of pre-existent phases. Petrographic characteristics and trace element data also exclude the possibility of percolation of host-basalt related melts for the origin of these glasses. Thus the glasses must have resulted from local penetration of mantle metasomatic melts which may have been produced by partial melting of peridotites with involvement of deep-seated fluids. Such melts may have been significantly modified by subsequent fractional crystallization of ol, cpx and sp, extensive reaction with the mantle conduit and the xenolith transport process.

Xu, Y.; Mercier, J.-C. C.; Lin, Chuanyong; Shi, Lanbin; Menzies, M. A.; Ross, J. V.; Harte, B.

1996-11-01

261

Alkalis partitioning between miscible liquids: Experimental investigation and implications for magmas mixing/contamination  

NASA Astrophysics Data System (ADS)

Natural magmatic melts show wide variations in silica and the effect of SiO2 on the chemical properties of silicate melts is therefore of special interest. Model silicate melts (Di-An eutectic modified with variable amounts of silica and Ca2Si3O8 modified with variable amounts of alumina) were experimentally saturated with Na, K and Rb at a total pressure of 1 atm and temperatures of 1300-1470° C [1, 2]. A crucible supported loop technique was applied [3]. Either binary Na2O-SiO2 and K2O-SiO2 or complex Na2O-K2O-SiO2 and Na2O-K2O-Rb2O-SiO2 melts were used as alkalis sources. It was shown that alumina content in many cases has little influence on the degree of silicate melt saturation with alkalis. In contrast, silica content strongly affects the solubility of alkalis in silicate melts. Model calculations showed that the perfectly mobile behavior of alkalis leads to a potassium specifics in basalts contaminated by crustal materials and, correspondingly, a sodic specifics in silicic melts from crustal xenoliths contaminated by the enclosing basaltic melt. [1] Borisov (2008) Petrology, 16, 552-564. [2] Borisov Petrology, submitted. [3] Borisov et al. (2006) American Mineralogist, 91, 762-771.

Borisov, A.

2009-04-01

262

Interfacial tension between immiscible melts in the system K2O - FeO - Fe2O3 - Al2O3 - SiO2  

Microsoft Academic Search

Interfacial tension is a very important parameter of the kinetics of phase nucleation, dissolution and growth. Excess surface energy contributes to the energy barrier for phase nucleation, and works as the main driving force for minimization of phase contact surfaces in heterogeneous systems. Immiscible silicate melts have been found to form in a broad range of basaltic, dacitic and rhyolitic

J. Kaehn; I. V. Veksler; G. Franz; D. B. Dingwell

2009-01-01

263

Electrical properties of K2O-doped Ba0.5Sr 0.5TiO3 ceramic humidity sensor  

Microsoft Academic Search

A ceramic humidity sensor using Ba0.5Sr0.5TiO3 doped with a few molar percent of potassium oxide was studied. It was characterized by long life, was reversible without repeated high-temperature thermal desorption processes, and conductance against relative humidity (RH) sensitivity, as high as four orders of magnitude, was found at low frequencies. This sensor showed a good exponential relationship between the conductance,

Yuan-Chang Yeh; T. Y. Tseng

1989-01-01

264

Rectal cancer delivery of radiotherapy in adequate time and with adequate dose is influenced by treatment center, treatment schedule, and gender and is prognostic parameter for local control: Results of study CAO/ARO/AIO-94  

SciTech Connect

Purpose: The impact of the delivery of radiotherapy (RT) on treatment results in rectal cancer patients is unknown. Methods and Materials: The data from 788 patients with rectal cancer treated within the German CAO/AIO/ARO-94 phase III trial were analyzed concerning the impact of the delivery of RT (adequate RT: minimal radiation RT dose delivered, 4300 cGy for neoadjuvant RT or 4700 cGy for adjuvant RT; completion of RT in <44 days for neoadjuvant RT or <49 days for adjuvant RT) in different centers on the locoregional recurrence rate (LRR) and disease-free survival (DFS) at 5 years. The LRR, DFS, and delivery of RT were analyzed as endpoints in multivariate analysis. Results: A significant difference was found between the centers and the delivery of RT. The overall delivery of RT was a prognostic factor for the LRR (no RT, 29.6% {+-} 7.8%; inadequate RT, 21.2% {+-} 5.6%; adequate RT, 6.8% {+-} 1.4%; p = 0.0001) and DFS (no RT, 55.1% {+-} 9.1%; inadequate RT, 57.4% {+-} 6.3%; adequate RT, 69.1% {+-} 2.3%; p = 0.02). Postoperatively, delivery of RT was a prognostic factor for LRR on multivariate analysis (together with pathologic stage) but not for DFS (independent parameters, pathologic stage and age). Preoperatively, on multivariate analysis, pathologic stage, but not delivery of RT, was an independent prognostic parameter for LRR and DFS (together with adequate chemotherapy). On multivariate analysis, the treatment center, treatment schedule (neoadjuvant vs. adjuvant RT), and gender were prognostic parameters for adequate RT. Conclusion: Delivery of RT should be regarded as a prognostic factor for LRR in rectal cancer and is influenced by the treatment center, treatment schedule, and patient gender.

Fietkau, Rainer [Department of Radiation Therapy, University of Rostock, Rostock (Germany)]. E-mail: rainer.fietkau@med.uni-rostock.de; Roedel, Claus [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany); Hohenberger, Werner [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany); Raab, Rudolf [Department of Surgery, Klinikum Oldenburg, Oldenburg (Germany); Hess, Clemens [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Liersch, Torsten [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Becker, Heinz [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Wittekind, Christian [Institute of Pathology, University of Leipzig, Leipzig (Germany); Hutter, Matthias [Department of Radiation Therapy, Krankenhaus Nordwest Frankfurt, Frankfurt (Germany); Hager, Eva [Department of Radiation Therapy, Krankenhaus Klagenfurt, Klagenfurt (Austria); Karstens, Johann [Department of Radiation Therapy, University of Hannover, Hannover (Germany); Ewald, Hermann [Department of Radiation Therapy, University of Schleswig-Holstein, Campus Kiel, Kiel (Germany); Christen, Norbert [Department of Radiation Therapy, Krankenhaus Dresden-Friedrichstadt, Dresden (Germany); Jagoditsch, Michael [Department of Surgery, Klinikum St. Veit, St. Veit (Austria); Martus, Peter [Institute of Biostatistics and Clinical Epidemiology, Charite Universitary Medicine Berlin, Berlin (Germany); Sauer, Rolf [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany)

2007-03-15

265

Simulations with CAO-3D model of photochemical response caused by precipitating electrons and solar protons at both polar regions during geomagnetic storms in October-November 2003 (preliminary comparison with MIPAS data)  

NASA Astrophysics Data System (ADS)

Relativistic electrons precipitating from radiation belts and solar protons can penetrate below 100 km into the polar atmosphere sometimes reaching the stratospheric levels wasting its energy and causing the ionization. It leads to additional production of NOx and HOx chemical com-pounds which destroy ozone in the chemical catalytic cycles. One of the strongest geomagnetic storms accompained by a strong Solar Proton Eevent (SPE) occured in October-November 2003. This period was covered also by observations with MIPAS instrument placed on board of ENVISAT satellite. The response of atmospheric chemical composition in both polar regions was studied with CAO-3D photochemical-transport model. In order to calculate ionization rates induced by precipitating electrons and solar protons during late October and November 2003, corresponding proton and electron fluxes in different energetic channels from GOES-10 and POES-15/16 have been used. The Atmospheric Ionization Module Osnabruck -AIMOS /Wissing and Kallenrode, 2009/ was used to calculate 3D fields of ionization rates separately by electrons and protons. Photochemical simulations showed that Northern and Southern po-lar regions had different photochemical response. Such difference mostly is the result of the two factors: polar cap expansion during the geomagnetic storm and the effect of horizontal transport. The calculated members of NOy, HOx, Cly families were preliminary compared with corresponding observed data measured by MIPAS and showed a general agreement. The sensitivity of calculated chemical response to the efficiencies of NOx and HOx production by en-ergetic particles have been studied also. This work was supported by Russian Science Foudation for Basic Research (grant 09-05-009949) and by contract 1-6-08 under Russian Sub-Program "Reseach and Investigation of Antarctica".

Krivolutsky, Alexei A.; Banin, Max; Maik Wissing, Jan; Vyushkova, Tatyana

266

An XRD study of the effect of the SiO 2\\/Na 2O ratio on the alkali activation of fly ash  

Microsoft Academic Search

Soluble silica has a very significant effect on the microstructural and mechanical development of the cementitious materials produced as a result of the alkali activation of fly ash. In this study, four different alkaline solutions with different soluble silica contents were used to activate fly ash. The primary reaction product was a sodium aluminosilicate gel, while different types of zeolites

M. Criado; A. Fernández-Jiménez; A. G. de la Torre; M. A. G. Aranda; A. Palomo

2007-01-01

267

Zircon solubility and zirconium complexation in H2O+Na2O+SiO2±Al2O3 fluids at high pressure and temperature  

NASA Astrophysics Data System (ADS)

Zircon is an important host mineral for many high-field strength elements (HFSE), particularly Zr and Hf. Thus, its solubility in geologic fluids at high pressure and temperature plays an important role in terrestrial cycling of these elements during processes in the Earth's crust and mantle. We performed in-situ high-pressure, high-temperature measurements of zircon solubility in H2O-Na2Si3O7, H2O-Na2Si3O7+Al2O3, H2O-Na2Si2O5, H2O-NaAlSi3O8 fluids, as well as of baddeleyite solubility in H2O-NaOH fluids, by in-situ synchrotron radiation X-ray fluorescence analysis using hydrothermal diamond-anvil cells. Zirconium complexation in fluids in equilibrium with zircon was constrained by in-situ X-ray absorption near-edge structure (XANES) spectroscopy. Zircon solubility is strongly enhanced by addition of Na2Si3O7 to H2O. The degree of enhancement increases with Na2Si3O7 concentration. The Zr content of fluids containing 10 wt% Na2Si3O7 reached up to 86±2 ppm Zr at 550 °C and 400 MPa. At 30 wt% Na2Si3O7, the maximum Zr concentration was 997±6 ppm at 600 °C and 440 MPa. Zircon solubility in these fluids decreases considerably with pressure and increases slightly with temperature. Addition of Al2O3 decreases the zircon solubility. In H2O-NaAlSi3O8 fluids, the Zr concentrations are in the sub-ppm to ppm range. Zr concentrations in NaOH solutions in equilibrium with baddeleyite reached up to 390±2 ppm at 600 °C and 930 MPa and increase with pressure and temperature. In-situ XANES spectra collected on Zr in H2O-Na2Si3O7, H2O-Na2Si3O7+Al2O3, H2O-NaOH, and H2O-HCl fluids in equilibrium with zircon provide evidence for strong differences in the Zr complexation between these fluids. Comparison of XANES spectra to those of model compounds and ab-initio simulation of XANES spectra revealed [8]Zr for the HCl solution, [7]Zr for the NaOH solution, and [6]Zr for the Na-Al-silicate-bearing solutions. For the latter solutions, formation of alkali zircono-silicate complexes is indicated by the strong dependence of zircon solubility on Na/Al and the similarity of the XANES spectra to spectra simulated based on the local structure around Zr in the alkali zircono-silicates vlasovite and catapleite. Alkali zircono-silicate complexes are responsible for the enhancement of Zr concentrations in Na-Al-silicate-bearing solutions and very likely play an important role for mobilization of HFSE during fluid-rock interaction. Because high alkali/Al can be expected in aqueous fluids at high pressure and temperature due to incongruent dissolution of feldspar and mica, the increase of zircon solubility along the NaAlSi3O8-Na2Si3O7 join points to potentially considerable Zr or HFSE transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.

Wilke, Max; Schmidt, Christian; Dubrail, Julien; Appel, Karen; Borchert, Manuela; Kvashnina, Kristina; Manning, Craig E.

2012-10-01

268

Molecular Dynamics Simulation of La2O3-Na2O-SiO2 Glasses. II. The Clustering of La3+ Cations  

SciTech Connect

Clustering of high-field strength rare-earth (RE) ions in silicate glasses is known to occur regardless of their concentration. This has also been recently observed by molecular dynamics computer simulations. Although there have been numerous experimental studies, atomic-level structural details of the mechanisms that lead to clustering remain unclear. In this work molecular dynamics computer simulations are used to verify that clustering is not an artifact of the simulation method and to provide clues as to the mechanism of atomic-level clustering.

Park, Byeongwon; Corrales, Louis R.

2002-11-05

269

Results of the Hawaii Scientific Drilling Project: Petrogenesis of Mauna Kea tholeiites  

NASA Astrophysics Data System (ADS)

The Hawaii Scientific Drilling (HSDP) project recovered ~3 km of fresh basaltic rocks by coring into the flank of the Mauna Kea volcano at Hilo. Rocks recovered from deeper than 1 km were all deposited below sea level (pillow lavas, hyaloclastites, and massive lava flows; there are also minor shallow intrusives emplaced roughly contemporaneously with the submarine units). Because of the submarine deposition, there is considerable fresh glass in the recovered samples, providing a high-resolution record of petrogenesis over a several hundred thousand year interval of shield building of a major Hawaiian volcano. In contrast to what is observed in subaerially exposed Hawaiian shields, the tholeiites from the HSDP core span a significant range (~48-52.5%) in SiO2 contents at 7-8% MgO. Moreover, the SiO2 contents are bimodally distributed, with modes at ~48.5-49 and 51-52%. Al2O3, FeO, Na2O, H2O, and TiO2 contents of the high-SiO2 group are lower than those of the low-SiO2 group, but K2O and CaO contents of the two groups are essentially identical. The two groups are for the most part also distinguishable isotopically and in terms of their trace element contents. In addition to these major compositional groups, there is a more subtle grouping of glasses at 49-50% SiO2 with slightly elevated CaO, Al2O3, and TiO2 contents, one isolated occurrence of low-SiO2 glasses with significantly elevated K2O and CaO contents, and one 50 m zone in which the low-SiO2 group trends toward transitional compositions and elevated incompatible element concentrations. We propose the following model for the generation of the two major tholeiitic magma types in the HSDP core: The low-SiO2 magmas are produced by melting of a dominantly lherzolitic source, with segregation of the liquid from the residue at ~30 kbar. The high-SiO2 magmas are produced by thermal and chemical interaction between the low-SiO2 magmas and lherzolite as the low-SiO2 magmas ascend through overlying peridotites (these peridotites are envisioned as not melting since they are moving roughly horizontally due to lithospheric drag on the plume). Using pMELTS to constrain the reaction coefficients that would apply during such coupled ascent/reaction, we are able to explain quantitatively the major and minor element compositions of the high-SiO2 magmas. The modeling predicts that olivine precipitates and orthopyroxene and clinopyroxene are resorbed during this reaction, and every 100 g of ascending melt must interact with ~35-55 g of peridotite. The bimodality of the observed magmas and the upper limit to the observed SiO2 contents are explained by the melt-peridotite reaction proceeding to similar extents repeatedly, controlled by the base of the lithosphere. Magmas with >50% SiO2 of the sort found in the HSDP core are typical of most Hawaiian shields, so if this hypothesis for the petrogenesis of high-SiO2 Hawaiian magmas from Mauna Kea is valid, such melt-peridotite interactions may be an important control on magma composition in Hawaiian magmatism and hot spot magmatism more generally.

Stolper, E.; Baker, M. B.

2003-04-01

270

Geochemistry and shock petrography of the Crow Creek Member, South Dakota, USA: Ejecta from the 74-Ma Manson impact structure  

USGS Publications Warehouse

The Crow Creek Member is one of several marl units recognized within the Upper Cretaceous Pierre Shale Formation of eastern South Dakota and northeastern Nebraska, but it is the only unit that contains shock-metamorphosed minerals. The shocked minerals represent impact ejecta from the 74-Ma Manson impact structure (MIS). This study was aimed at determining the bulk chemical compositions and analysis of planar deformation features (PDFs) of shocked quartz; for the basal and marly units of the Crow Creek Member. We studied samples from the Gregory 84-21 core, Iroquois core and Wakonda lime quarry. Contents of siderophile elements are generally high, but due to uncertainties in the determination of Ir and uncertainties in compositional sources for Cr, Co, and Ni, we could not confirm an extraterrestrial component in the Crow Creek Member. We recovered several shocked quartz grains from basal-unit samples, mainly from the Gregory 84-21 core, and results of PDF measurements indicate shock pressures of at least 15 GPa. All the samples are composed chiefly of SiO2, (29-58 wt%), Al2O3 (6-14 wt%), and CaO (7-30 wt%). When compared to the composition of North American Shale Composite, the samples are significantly enriched in CaO, P2O5, Mn, Sr, Y, U, Cr, and Ni. The contents of rare earth elements (REE), high field strength elements (HFSE), Cr, Co, Sc, and their ratios and chemical weathering trends, reflect both felsic and basic sources for the Crow Creek Member, an inference, which is consistent with the lithological compositions in the environs of the MIS. The high chemical indices of alteration and weathering (CIA' and CIW': 75-99), coupled with the Al2O3-(CaO*,+Na2O -K2O (A-CN'-K) ratios, indicate that the Crow Creek Member and source rocks had undergone high degrees of chemical weathering. The expected ejecta thicknesses at the sampled locations (409 to 219 km from Manson) were calculated to range from about 1.9 to 12.2 cm (for the present-day crater radius of Manson), or 0.4 to 2.4 cm (for the estimated transient cavity radius). The trend agrees with the observed thicknesses of the basal unit of the Crow Creek Member, but the actually observed thicknesses are larger than the calculated ones, indicating that not all of the basal unit comprises impact ejecta. ?? Meteoritical Society, 2004.

Katongo, C.; Koeberl, C.; Witzke, B. J.; Hammond, R. H.; Anderson, R. R.

2004-01-01

271

On ``Birthmarks'' in rare-metal granites of the Losevka pluton, northern Kazakhstan  

NASA Astrophysics Data System (ADS)

The Losevka pluton of rare-metal albite granite, which was explored as a possible source of columbite-zircon-malacon ore, is composed of quartz, sodic plagioclase, potassium feldspar, annite, protolithionite, lepidomelane, and Li-muscovite. The average chemical composition of this rock is as follows, wt %: 74.14 SiO2, 0.04 TiO2, 14.07 Al2O3, 1.05 Fe2O3, 0.78 FeO, 0.15 MnO, 0.09 MgO, 0.47 CaO, 4.65 Na2O, 4.11 K2O, and 0.03 P2O5. The accessory minerals are zircon, malacon, and cyrtolite (874 ppm); apatite (18 ppm); ilmenite (114 ppm); xenotime and monazite (119 ppm); and Nb-columbite (463 ppm). The black inclusions up to 15 cm in size, which are observed in this granite and called “birthmarks” by local geologists, consist of the same rock-forming minerals as the surrounding granite, but are enriched in MnO, MgO, CaO, TiO2, and F and depleted in SiO2 relative to the light granite. The black granite is also distinguished by much higher Sr and Ba contents and lower La, Rb, Y, Nb, REE, Cs, Ta, Th, and U contents. The black color is caused by enrichment in manganese oxides, manganoilmenite, and Mn-annite. All rock-forming minerals are pervaded by thin veinlets of Mn-oxides. In addition, bastnaesite, Y-and Th-fluorides, zircon, and malacon have been identified. Aggregates of black-colored minerals are not the products of the fractionation of the initial magma or immiscibility effects, because the structure of the albite-potassium feldspar-quartz-mica matrix is the same both in black and light granites. The percolation of a deep-sourced fluid enriched in Mn and F into a granitic melt might be a more probable origin.

Letnikov, F. A.; Levin, A. V.; Letnikova, A. F.

2007-12-01

272

Mid-Pleistocene lavas from the Seguam volcanic center, central Aleutian arc: closed-system fractional crystallization of a basalt to rhyodacite eruptive suite  

NASA Astrophysics Data System (ADS)

In contrast to adjacent volcanic centers of the modern central Aleutian arc, Seguam Island developed on strongly extended arc crust. K-Ar dates indicate that mid-Pleistocene, late-Pleistocene, and Holocene eruptive phases constitute Seguam. This study focuses on the petrology of the mid-Pleistocene, 1.07 07 Ma, Turf Point Formation (TPF) which is dominated by an unusual suite of porphyritic basalt and basaltic andesite lavas with subordinate phenocryst-poor andesite to rhyodacite lavas. Increasing whole-rock FeO*/MgO from basalt to dacite, the anhydrous Plag+Ol+Cpx±Opx±Mt phenocryst assemblage, groundmass pigeonite, and the reaction Ol+Liq=Opx preserved in the mafic lavas indicate a tholeiitic affinity. Thermometry and comparison to published phase equilibria suggests that most TPF basalts crystallized Plag+Ol+Cpx±Mt at ?1160°C between about 3 5 kb (±1 2% H2O), andesites crystallized Plag+Cpx+Opx±Mt at ?1000°C between 3 4 kb with 3 5% H2O, and dacites crystallized Plag +Cpx±Opx±Mt at 1000°C between 1 2 kb with 2 3% H2O. All lavas crystallized at f o 2 close to the NNO buffer. Mineral compositions and textures indicate equilibrium crystallization of the evolved lavas; petrographic evidence of open-system mixing or assimilation is rare. MgO, CaO, Al2O3, Cr, Ni, and Sr abundances decrease and K2O, Na2O, Rb, Ba, Zr, and Pb increase with increasing SiO2 (50 71%). LREE enrichment [(Ce/Yb)n=1.7±0.2] characterizes most TPF lavas; total REE contents increase and Eu anomalies become more negative with increasing SiO2. Relative to other Aleutian volcanic centers, TPF basalts and basaltic andesites have lower K2O, Na2O, TiO2, Rb, Ba, Sr, Zr, Y, and LREE abundances. 87Sr/86Sr ratios (0.70361 0.70375) and ratios of 206Pb/204Pb (18.88 18.97), 207Pb/204Pb (15.58 15.62), 208Pb/204Pb (38.46 38.55) are the highest measured for any suite of lavas in the oceanic portion of the Aleutian arc. Conversely, ?Nd values (+5.8 to+6.7) are among the lowest from the Aleutians. Sr, Nd, and Pb ratios are virtually constant from basalt through rhyodacite, whereas detectable isotopic heterogenity is observed at most other Aleutian volcanic centers. Major and trace element, REE, and Sr, Nd, and Pb isotopic compositions are consistent with the basaltic andesitic, andesitic, dacitic, and rhyodacitic liquids evolving from TPF basaltic magma via closed-system fractional crystallization alone. Fractionation models suggest that removal of ˜80 wt% cumulate (61% Plag, 17% Cpx, 12% Opx, 7% Ol, and 3% Mt) can produce 20 wt% rhyodacitic residual liquid per unit mass of parental basaltic liquid. Petrologic and physical constraints favor segregation of small batches of basalt from a larger mid-crustal reservoir trapped below a low-density upper crustal lid. In these small magma batches, the degree of cooling, crystallization, and fractionation are functions of the initial mass of basaltic magma segregated, the thermal state of the upper crust, and the magnitude of extension. Tholeiitic magmas erupted at Seguam evolved by substantially different mechanisms than did calc-alkaline lavas erupted at the adjacent volcanic centers of Kanaga and Adak on unextended arc crust. These variable differentiation mechanisms and liquid lines of descent reflect contrasting thermal and mechanical conditions imposed by the different tectonic environments in which these centers grew. At Seguam, intra-arc extension promoted eruption of voluminous basalt and its differentiates, unmodified by interaction with lower crustal or upper mantle wallrocks.

Singer, Bradley S.; Myers, James D.; Frost, Carol D.

1992-03-01

273

Carbonate-Silicate Association in the Kamafugite of the Toro-Ankole Province (East African Rift)  

NASA Astrophysics Data System (ADS)

Carbonatite melts play an important role in the magmatism of the East African Rift Zone. A tight spatial association of high-Mg ultrapotassic and carbonatite rocks in the Western branch of the East African Rift suggests the genetic relationship of their parental melts. New evidence of such connection of kamafugitic and carbonatite magmas were obtained during study of the volcanic rocks of kamafugitic affinity in Toro-Ankole province. Primary carbonates (calcite and dolomite) were found as inclusions in olivine from ugandite and mafurite of the Bunyaruguru volcanic field. In the ugandite carbonates contain in the crystallized melt inclusions in olivine phenocrysts consist also of kalsilite, clinopyroxene, mica, and titanomagnetite. Some inclusions reach up to 40x75µm, the host olivine is 150x300µm in size. In the mafurite carbonates form rare microlites, microphenocrysts, and lenses with cavities in central parts, and occur as inclusions in olivine phenocrysts and aggregates in the adjacent zones. These aggregates are multiphase and in mineral set resemble carbonatites: they contain kalsilite, clinopyroxene, magnetite, phillipsite, and mica. Also the two-phase carbonate-sulfate inclusions in olivine were found. The most part of carbonates in composition correspond to calcites with low magnesium, iron, sodium, strontium, and barium contents. The carbonates from two-phase inclusions in olivine from the mafurite are significantly higher magnesian, approaching pure dolomite. The different types of carbonate in mafurite vary in Sr, Ba, Na and K. The highest content of these elements is observed in groundmass carbonates, reaching 2.44 wt % SrO, 1.25% BaO, 0.64% Na2O, and 1.23% K2O. Such assemblage in kamafugites have not been described yet. Some olivines contain microinclusions of sulfate (barite), occurs as fine (10-20 µm) rounded inclusions. The presence of barite inclusions in the olivine of the studied mafurite indicates the high sulfur content in the primary melt. The temperature and oxygen fugacity for the studied rocks was estimated from olivine-spinel equilibrium. Obtained results indicate that crystallization of the mafurite occurred within a wide range of temperature (1230-750°C) and oxygen fugacity (1-3 log units above the QFM buffer). These data demonstrate that crystallization of Toro-Ankole kamafugites occurred in a relatively oxidized setting close to those of wehrlites and subduction-related island-arc oxidized magmas. An increase in oxygen chemical potential resulted from mantle metasomatism widely spread in this area of the East African Rift. To elucidate the origin of kamafugite carbonate inclusions the bulk composition of initial melt for two crystallized inclusions in the ugandite olivine was calculated from data on analyzed mineral compositions. Obtained melts appear to be carbonatite, close to the bomb of Katwe-Kikorongo and average composition of intrusive carbonatite. According to morphology, these are primary inclusions and obtained composition is close to the composition of melt trapped during olivine crystallization. The validity of results has been estimated using a multicomponent system (SiO2 + Al2O3 + TiO2) - CaO + MgO + FeO*)-(Na2O + K2O), which is most close to natural rocks. The compositions of the kamafugite rocks of the Toro-Ankole province were plotted on the diagram with calculated "carbonatite melts". Compositions of calculated melts from inclusions in olivine are plotted on the trend of progressive melting carbonatised lherzolite (or fractional crystallization of alkali basalts), which connects fields of primary carbonatite melts and alkali basalts with data points of high-Mg volcanics of Bunyaruguru. The presence of magmatic carbonates in the olivine from the mafurite and ugandite of the Bunyaruguru volcanic field, the western branch of the East African Rift, indicates that ultrapotassic magmas were in equilibrium with primary carbonatite melts at P-T conditions of their formation.

Muravyeva, Natalya; Senin, Valery

2010-05-01

274

Late Paleozoic to Early Mesozoic arc-related magmatism in southeastern Korea: SHRIMP zircon geochronology and geochemistry  

NASA Astrophysics Data System (ADS)

Phanerozoic granitoids are widespread in the Korean Peninsula and form a part of the East Asian Cordilleran-type granitoid belt extending from southeastern China to Far East Russia. Here we present SHRIMP zircon U-Pb ages and geochemical and Nd isotopic compositions of Late Paleozoic to Early Jurassic granitoid plutons in the northern Gyeongsang basin, southeastern Korea; namely the Jangsari, Yeongdeok, Yeonghae, and Satkatbong plutons. The granite and associated gabbroic rocks from the Jangsari pluton were coeval and respectively dated at 257.3 ± 2.0 Ma and 255.7 ± 1.4 Ma. This result represents the first finding of a Late Paleozoic pluton in South Korea. Three granite samples from the Yeongdeok pluton yielded a slightly younger age span ranging from 252.9 ± 2.5 Ma to 246.7 ± 2.1 Ma. Two diorite samples from the Yeonghae pluton gave much younger ages of 195.1 ± 1.9 Ma and 196.3 ± 1.6 Ma. An Early Jurassic age of 192.4 ± 1.6 Ma was also obtained from a diorite sample from the Satkatbong pluton. The mineral assemblage and Al2O3/(Na2O + K2O) versus Al2O3/(CaO + Na2O + K2O) relationship indicate that all the analyzed plutons are subduction zone granitoids. Enrichments in large-ion-lithophile-elements and depletions in high-field-strength-elements of these plutons are also concordant with geochemical characteristics typical for the subduction zone magma. The presence of Late Permian to Early Triassic arc system is in contrast with the conventional idea that the arc magmatism along the continental margin of the Korean Peninsula has commenced from Early Jurassic after the termination of Triassic collisional orogenesis. The ?Nd(t) values of the granitoid plutons are consistently positive (2.4-4.6), suggesting that crustal residence time of the basement beneath the Gyeongsang basin is relatively short. Moreover, the reevaluation of previously-published data reveals that geochemical compositions of the Yeongdeok pluton are compatible with those of high-silica adakites; La/Yb = 37.5-114.6, Sr/Y = 138.2-214.0, SiO2 = 62.9-72.0 wt.%, Al2O3 = 15.5-17.0 wt.%, Sr = 562-1173 ppm, MgO = 0.4-1.6 wt.%, Y = 3-6 ppm, Yb = 0.18-0.45 ppm, and Eu/Eu* = 0.92-1.31. The occurrence of adakites in southeastern Korea, and presumably in the Hida belt of central-western Japan, is indicative of a hot subduction regime developing at least partly along the East Asian continental margin during the Permian-Triassic transition period.

Yi, Keewook; Cheong, Chang-sik; Kim, Jeongmin; Kim, Namhoon; Jeong, Youn-Joong; Cho, Moonsup

2012-11-01

275

Crystallization of tholeiitic basalt in Alae Lava Lake, Hawaii  

USGS Publications Warehouse

The eruption of Kilauea Volcano August 21-23, 1963, left 600,000 cubic meters of basaltic lava in a lava lake as much as 15 meters deep in Alae pit crater. Field studies of the lake began August 27 and include repeated core drilling, measurements of temperature in the crust and melt, and precise level surveys of the lake surface. The last interstitial melt in the lake solidified late in September 1964; by mid August 1965 the maximum temperature was 690??C at a depth of 11.5 meters. Pumice air-quenched from about 1140??C contains only 5 percent crystals - clinopyroxene, cuhedral olivine (Fo 80), and a trace of plagioclase, (An 70). Drill cores taken from the zone of crystallization in the lake show that olivine continued crystallizing to about 1070??C; below that it reacts with the melt, becoming corroded and mantled by pyroxene and plagioclase. Below 1070??C, pyroxene and plagioclase crystallized at a constant ratio. Ilmenite first appeared at about 1070??C and was joined by magnetite at about 1050??C; both increased rapidly in abundance to 1000??C. Apatite first appeared as minute needles in interstitial glass at 1000??C. Both the abundance and index of refraction of glass quenched from melt decreased nearly linearly with falling temperature. At 1070??C the quenched lava contains about 65 percent dark-brown glass with an index of 1.61; at 980??C it contains about 8 percent colorless glass with an index of 1.49. Below 980??C, the percentage of glass remained constant. Progressive crystallization forced exsolution of gases from the melt fraction; these formed vesicles and angular pores, causing expansion of the crystallizing lava and lifting the surface of the central part of the lake an average of 19.5 cm. The solidified basalt underwent pneumatolitic alteration, including deposition of cristobalite at 800??C, reddish alteration of olivine at 700??C, tarnishing of ilmenite at 550??C, deposition of anhydrite at 250??C, and deposition of native sulfur at 100??C. Ferric-ferrous ratios suggest that oxidation with maximum intensity between 550??C and 610??C moved downward in the crust as it cooled; this was followed by reduction at a temperature of about 100??C. The crystallized basalt is a homogeneous fine-grained rock containing on the average 48.3 percent by volume intergranular pyroxene (augite > pigeonite), 34.2 percent plagioclase laths (An60 70), 7.9 percent interstitial glass, 6.9 percent opaques (ilmenite > magnetite), 2.7 percent olivine (Fo70 80), and a trace of apatite. Chemical analyses of 18 samples, ranging from initially quenched pumice to lava cored more than a year after the eruption from the center and from near the base of the lake, show little variation from silica-saturated tholeiitic basalt containing 50.4 percent SiO2, 2.4 percent Na2O, and 0.54 percent K2O. Apparently there was no significant crystal settling and no appreciable vapor-phase transport of these components during the year of crystallization. However, seven samples of interstitial liquid that had been filter-pressed into gash fractures and drill holes from partly crystalline mush near the base of the crust show large differences from the bulk composition of the solidified crust-lower MgO, CaO, and Al2O3; and higher total iron, TiO2, Na2O, K2O, P2O5, and F, and, in most samples, SiO2. The minor elements Ba, Ga, Li, Y, and Yb and possibly Cu tend to be enriched in the filter-pressed liquids, and Cr and possibly Ni tend to be depleted. ?? 1966 Stabilimento Tipografico Francesco Giannini & Figli.

Peck, D. L.; Wright, T. L.; Moore, J. G.

1966-01-01

276

Petrogenesis of syn-orogenic basement-derived granites (Central Damara Orogen, Namibia): insights from Nd, Sr and Pb isotopes  

NASA Astrophysics Data System (ADS)

The Pan-African Damara orogen (Namibia) represents a well-exposed and deeply eroded orogenic mobile belt consisting of the north-south extending Kaoko belt and the northeast-southwest trending intracontinental Damara belt. The latter has been subdivided into a Northern, a Central and a Southern Zone based on stratigraphy, metamorphic grade, structure and geochronology. In the central part Proterozoic basement gneisses are overlain by Neoproterozoic to Paleozoic metasedimentary sequences. The Kubas pluton in the Central Zone (ca. 25 km south of Usakos) consists of two different, non-genetic granite types, the grey Kubas granite and the red Kubas leucogranite. The weakly deformed grey Kubas granite consists of quartz, plagioclase, microcline/orthoclase and biotite. Major and trace element variations show weak negative correlations of TiO2, MgO, CaO, Na2O, Sr and Ba vs. SiO2 and weak positive correlations of K2O vs. SiO2. Rubidium, Sr and Ba covariations demonstrate that fractional crystallisation processes of mainly plagioclase and K-feldspar occurred (< 10% fractional crystallisation). This observation is supported by moderate negative Eu anomalies. The grey granites are isotopically evolved (initial ? Nd: ~ -16; initial 87Sr/86Sr > 0.719; calculated for an assumed age of 500 Ma) and were likely derived from sources with early Proterozoic crustal residence ages, as shown by depleted mantle Nd model ages between 2.1 and 2.6 Ga. Pb isotope data, obtained on acid leached feldspar, show significant variation of 207Pb/204Pb relative to 206Pb/204Pb and plot above the Stacey and Kramers reference curve. In 208Pb/204Pb vs. 206Pb/204Pb the samples also plot above the Pb reference curve with minor variations in 208Pb/204Pb. These features suggest that the source of the granites had a high U/Pb and Th/U ratio. These isotope characteristics support a model of an ancient source for the granite. Major element features (Na2O: 3.0-3.5 wt.%, K2O: 4.2-5.1 wt.%) and trace element characteristics (Rb: 230-280 ppm; Sr: 110-140 ppm; Ba: 520-630 ppm) of the granites are between those assumed to be characteristic for metasedimentary or meta-igneous sources. Since Proterozoic metasedimentary rocks are not known from the basement-dominated part of the Damara orogen, the likely source for the grey Kubas granites is meta-igneous pre-Damara basement located in the lower crust. The heating events that promoted melting of fertile deep crustal rocks might have been caused by the inferred high heat productivity of heat-producing radioactive elements (Th, U, K) together with crustal thickening during the main periods of the Damara orogeny. This view is supported by moderate high Th/U ratios of the granites (4-6) and moderate high heat production values of ca. 3-4 ?W/m3. In addition, delamination of mantle lithosphere during the final extensional stages of the Pan-African orogeny is a possibility.

Ostendorf, Jörg; Jung, Stefan

2010-05-01

277

Natural weathering in dry disposed ash dump: Insight from chemical, mineralogical and geochemical analysis of fresh and unsaturated drilled cores.  

PubMed

Some existing alternative applications of coal fly ash such as cement manufacturing; road construction; landfill; and concrete and waste stabilisation use fresh ash directly collected from coal-fired power generating stations. Thus, if the rate of usage continues, the demand for fresh ash for various applications will exceed supply and use of weathered dry disposed ash will become necessary alternative. As a result it's imperative to understand the chemistry and pH behaviour of some metals inherent in dry disposed fly ash. The bulk chemical composition as determined by XRF analysis showed that SiO2, Al2O3 and Fe2O3 were the major oxides in fresh ash and unsaturated weathered ashes. The unsaturated weathered ashes are relatively depleted in CaO, Fe2O3, TiO2, SiO2, Na2O and P2O5 due to dissolution and hydrolysis caused by chemical interaction with ingressing CO2 from the atmosphere and infiltrating rain water. Observed accumulations of Fe2O3, TiO2, CaO, K2O, Na2O and SO3 and Zn, Zr, Sr, Pb, Ni, Cr and Co in the lower layers indicate progressive downward movement through the ash dump though at a slow rate. The bulk mineralogy of unsaturated weathered dry disposed ash, as determined by XRD analysis, revealed quartz and mullite as the major crystalline phases; while anorthite, hematite, enstatite, lime, calcite, and mica were present as minor mineral phases. Pore water chemistry revealed a low concentration of readily soluble metals in unsaturated weathered ashes in comparison with fresh ash, which shows high leachability. This suggests that over time the precipitation of transient minor secondary mineral phases; such as calcite and mica might retard residual metal release from unsaturated weathered ash. Chloride and sulphate species of the water soluble extracts of weathered ash are at equilibrium with Na+ and K+; these demonstrate progressive leaching over time and become supersaturated at the base of unsaturated weathered ash. This suggests that the ash dump does not encapsulate the salt or act as a sustainable salt sink due to over time reduction in pore water pH. The leaching behaviours of Ca, Mg, Na+, K+, Se, Cr and Sr are controlled by the pH of the leachant in both fresh and unsaturated weathered ash. Other trace metals like As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. The precipitation of minor quantities of secondary mineral phases in the unsaturated weathered ash has significant effects on the acid susceptibility and leaching patterns of chemical species in comparison with fresh ash. The unsaturated weathered ash had lower buffering capacity at neutral pH (7.94-8.00) compared to fresh (unweathered) ash. This may be due to the initial high leaching/flushing of soluble basic buffering constituents from fly ash after disposal. The overall results of the acid susceptibility tests suggest that both fresh ash and unsaturated weathered ash would release a large percentage of their chemical species when in contact with slightly acidified rain. Proper management of ash dumps is therefore essential to safeguard the environmental risks of water percolation in different fly ashes behaviour. PMID:22446137

Akinyemi, S A; Akinlua, A; Gitari, W M; Khuse, N; Eze, P; Akinyeye, R O; Petrik, L F

2012-03-22

278

Effect of the Cl ? content on the formation and dissolution of precipitates in a soda–lime–silica glass  

Microsoft Academic Search

The glass with composition 13Na2O–11CaO–76SiO2 (mol%) undergoes subliquidus phase separation via a binodal mechanism. Below the binodal temperature, Tb, the glass separates into two amorphous phases, silica-enriched droplets and a silica-poor matrix. Small-angle X-ray scattering (SAXS) is used to study the formation process of the droplet phase at 600 °C, as well as, the inverse process where the precipitates dissolve

Rainer Kranold; Martin Kammel; Armin Hoell

2001-01-01

279

Synthesis of MgO–SiO 2 and CaO–SiO 2 amorphous powder by sol–gel process and ion exchange  

Microsoft Academic Search

The processing of binary or ternary metal–oxide spherical powders often provides ideal starting materials for the preparation of ceramics or glasses, and the use of these powders can lead to excellent properties. Amorphous spherical powders composed of SiO2 and MgO or CaO were synthesized by using Na2O–SiO2 spherical powder as a starting material and then conducting ion-exchange between the magnesium

Sei-ichi Suda; Toshiya Tashiro; Takao Umegaki

1999-01-01

280

Na depletion in modern adakites via melt \\/ rock reaction within the sub-arc mantle  

Microsoft Academic Search

Interaction between slab-derived melt and mantle peridotite and the role of slab melt as a metasomatizing agent in the sub-arc mantle is being increasingly recognized. Adakite, the slab melt erupted on the surface, usually exhibits anomalously high MgO, CaO, Cr and Ni contents that indicate interaction with mantle peridotitite. Here we note that Cenozoic adakites have Na2O contents below 5.8

X. L. Xiong; B. Xia; J. F. Xu; H. C. Niu; W. S. Xiao

2006-01-01

281

Effect of ternary phosphate-based glass compositions on osteoblast and osteoblast-like proliferation, differentiation and death in vitro  

Microsoft Academic Search

There is currently a need to expand the range of graft materials available to orthopaedic surgeons. This study investigated the effect of ternary phosphate-based glass (PBG) compositions on the behaviour of osteoblast and osteoblast-like cells. PBGs of the formula (in mol.%) P2O5(50)–CaO(50?X)–Na2O(X), where X is either 2, 4, 6, 8 or 10, were produced and their influence on the proliferation,

K. L. Skelton; J. V. Glenn; S. A. Clarke; G. Georgiou; S. P. Valappil; J. C. Knowles; S. N. Nazhat; G. R. Jordan

2007-01-01

282

Effect of surface composition of yttrium-stabilized zirconia on partial oxidation of methane to synthesis gas  

Microsoft Academic Search

Catalytic partial oxidation of methane to synthesis gas (CPOM) over yttrium-stabilized zirconia (YSZ) was studied within a wide temperature window (500–1100?°C). The catalysts were characterized by X-ray fluorescence (XRF) and low-energy ion scattering (LEIS). The influence of calcination temperature, Y2O3 content, and especially impurities such as CaO, TiO2, and Na2O on catalytic performance were investigated. Creation of active sites by

Jianjun Zhu; Jan G. van Ommen; Arie Knoester; Leon Lefferts

2005-01-01

283

Geochemistry of silicic magmas in the Macolod Corridor, SW Luzon, Philippines: evidence of distinct, mantle-derived, crustal sources for silicic magmas  

NASA Astrophysics Data System (ADS)

Silicic volcanic deposits (>65 wt% SiO2), which occur as domes, lavas and pyroclastic deposits, are relatively abundant in the Macolod Corridor, SW Luzon, Philippines. At Makiling stratovolcano, silicic domes occur along the margins of the volcano and are chemically similar to the silicic lavas that comprise part of the volcano. Pyroclastic flows are associated with the Laguna de Bay Caldera and these are chemically distinct from the domes and lavas at Makiling stratovolcano. As a whole, samples from the Laguna de Bay Caldera contain lower concentrations of MgO and higher concentrations of Fe2O3(t) than the samples from domes and lavas. The Laguna de Bay samples are more enriched in incompatible trace elements. The silicic rocks from the domes, Makiling Volcano and Laguna de Bay Caldera all contain high alkalis and high K2O/Na2O ratios. Melting experiments of primitive basalts and andesites demonstrate that it is difficult to produce high K2O/Na2O silicic magmas by fractional crystallization or partial melting of a low K2O/Na2O source. However, recent melting experiments (Sisson et al., Contrib Mineral Petrol 148:635-661, 2005) demonstrate that extreme fractional crystallization or partial melting of K-rich basalts can produce these silicic magmas. Our model for the generation of the silicic magmas in the Macolod Corridor requires partial melting of mantle-derived, evolved, moderate to K-rich, crystallized calc-alkaline magmas that ponded and crystallized in the mid-crust. Major and trace element variations, along with oxygen isotopes and ages of the deposits, are consistent with this model.

Vogel, Thomas A.; Flood, Timothy P.; Patino, Lina C.; Wilmot, Melissa S.; Maximo, Raymond Patrick R.; Arpa, Carmencita B.; Arcilla, Carlo A.; Stimac, James A.

2006-03-01

284

Characterization of the lead smelter slag in Santo Amaro, Bahia, Brazil.  

PubMed

For 33 years, a primary lead smelter operated in Santo Amaro (Brazil). Since the 1970s, large amounts of Pb and Cd have been widely documented in the blood and hair of people living near the smelter. The plant closed down in 1993, and several years later, the Pb levels in the blood of children under 4 years of age living near the smelter were high, where the disposed lead slag was suspected to be the main source of this contamination. The objective of this study is to elucidate the source of the Pb contamination and any other potentially toxic contamination, focusing on the characterization of the slag. The samples used for this characterization study were taken from the slag heaps. The results of the chemical analysis showed that the major constituents of the slag, in decreasing order of wt%, were the following: Fe(2)O(3) (28.10), CaO (23.11), SiO(2) (21.39), ZnO (9.47), MgO (5.44), PbO (4.06), Al(2)O(3) (3.56), C (2.26), MnO (1.44), Na(2)O (0.27), S (0.37), K(2)O (0.26), and TiO(2) (0.25). The Cd content of the slag was 57.3mg/kg, which is relatively low. The X-ray diffraction and the electron probe microanalyzer X-ray mapping indicated that the major phases in the slag were wüstite, olivine, kirschsteinite, and franklinite. Only spheroidal metallic Pb was found in the slag. The leaching study showed that the slag was stable at a pH greater than 2.8, and only in an extremely acidic environment was the solubilization of the Pb enhanced significantly. The solubilization of Zn was very limited in the acidic and alkaline environments. These results can be explained by the limited leachability of the metallic Pb and Zn-bearing compounds. The leaching study used TCLP, SPLP, and SWEP and indicated that the lead slag was stable in weak acidic environments for short contact times. PMID:21440365

Lima, L R P de Andrade; Bernardez, L A

2011-03-06

285

New soil composition data for Europe and Australia: demonstrating comparability, identifying continental-scale processes and learning lessons for global geochemical mapping.  

PubMed

New geochemical data from two continental-scale soil surveys in Europe and Australia are compared. Internal project standards were exchanged to assess comparability of analytical results. The total concentration of 26 oxides/elements (Al2O3, As, Ba, CaO, Ce, Co, Cr, Fe2O3, Ga, K2O, MgO, MnO, Na2O, Nb, Ni, P2O5, Pb, Rb, SiO2, Sr, Th, TiO2, V, Y, Zn, and Zr), Loss On Ignition (LOI) and pH are demonstrated to be comparable. Additionally, directly comparable data for 14 elements in an aqua regia extraction (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo, and Pb) are provided for both continents. Median soil compositions are close, though generally Australian soils are depleted in all elements with the exception of SiO2 and Zr. This is interpreted to reflect the generally longer and, in places, more intense weathering in Australia. Calculation of the Chemical Index of Alteration (CIA) gives a median value of 72% for Australia compared to 60% for Europe. Element concentrations vary over 3 (and up to 5) orders of magnitude. Several elements (total As and Ni; aqua regia As, Co, Bi, Li, Pb) have a lower element concentration by a factor of 2-3 in the soils of northern Europe compared to southern Europe. The break in concentration coincides with the maximum extent of the last glaciation. The younger soils of northern Europe are more similar to the Australian soils than the older soils from southern Europe. In Australia, the central region with especially high SiO2 concentrations is commonly depleted in many elements. The new data define the natural background variation for two continents on both hemispheres based on real data. Judging from the experience of these two continental surveys, it can be concluded that analytical quality is the key requirement for the success of global geochemical mapping. PMID:22178529

Reimann, Clemens; de Caritat, Patrice

2011-12-16

286

Stratigraphy and Petrology of the Grande Soufriere Hills Volcano, Dominica, Lesser Antilles  

NASA Astrophysics Data System (ADS)

The Grande Soufriere Hills volcanic center is located on the south east coast of the island of Dominica in the Lesser Antilles. Although the volcano is deeply dissected, a distinct circular crater that opens to the east can be observed. Within the crater is a lava dome and unconsolidated pyroclastic deposits mantle the southeast flanks of the volcano. These pyroclastic deposits are almost entirely matrix-supported block and ash flows and surges suggesting that Pelean-style eruptions have dominated its most recent activity. Within this sequence is a relatively thin (30-50 cm) clast-supported deposit that has been interpreted as a possible blast deposit. Two age dates from these younger deposits suggest that much of this activity occurred between l0,000 and 12,000 years ago. On the southeastern coast at Pointe Mulâtre and extending approximately 4 km north and at a maximum 2 km west, is a megabreccia of large (up to 3 m) flow-banded andesite clasts set in a semi-lithified medium grained ash matrix. At Pointe Mulâtre this megabreccia is overlain by unconsolidated block and ash flow deposits. To the north of the megabreccia, exposures in the sea cliffs reveal a consolidated sequence of well-bedded alternating coarse and fine deposits suggesting deltaic foreset beds; which in turn appears to be overlain by a yellow- colored relatively coarse flow deposit with an irregular upper surface. The uppermost deposits in the sea cliffs are a sequence of unconsolidated block and ash flow deposits and interbedded fluviatile conglomerates equivalent to the younger flow deposits logged inland. Volcanic rocks from the Grande Soufriere Hills are all porphyritic andesites often containing hypabyssal inclusions. Dominant phenocrysts are plagioclase often with inclusion-rich cores and well developed zoning. Mafic phenocrysts include hornblende, augite and hypersthene. Geochemically these andesites range from 58- 63% SiO2 and show trends of decreasing values for Al2O3, FeO, MgO, CaO, TiO2, Sr, V, and Sc and increasing values for Na2O, K2O, Ba, Rb, and Zr with increasing silica. Samples from the megabreccia can be chemically distinguished from the younger rocks of this center. Petrologic models suggest that the younger rocks from the Grand Soufriere Hills can be produced by fractional crystallization of basaltic magma such as those erupted from other centers (such as Morne Anglais to the west). Minor variations within this suite of andesites can be related to upper crustal fractionation of phenocryst phases.

Daly, G.; Smith, A. L.; Garcia, R.; Killingsworth, N.

2007-12-01

287

Geochemistry and origin of Archaean quartz-cordierite gneisses from the Godthåbsfjord region, West Greenland  

NASA Astrophysics Data System (ADS)

We report new data on the major, minor and trace element compositions of metasedimentary quartzcordierite gneisses (QCG), an important member of the Archaean Malene supracrustal suite found throughout the Godthåbsfjord region of West Greenland. The analyzed QCG contain assemblages of quartz+cordierite+biotite±garnet±anthophyllite/gedrite±staurolite±sillimanite±plagioclase (with abundant accessory zircon, and minor rutile, monazite and allanite), and broadly resemble cordierite-orthoamphibole rocks found in a great number of other metamorphic terrains. Chemically, the QCG are characterized by: (1) high but variable SiO2 (59 87 wt%), relative enrichments in MgO, FeO, and Al2O3 (mg˜0.35 0.85), and depletions in Na2O, K2O and especially CaO; (2) low concentrations of Sc, Cr, Co, Ni, and Sr; (3) high concentrations of Y, Nb, Zr, Hf, Ta, Th, U, and REE (rare earth elements)-with prominent negative Eu-anomalies in each case; (5) high concentrations of Ga (18 55 ppm), with variable Ga/Al ratios that are significantly higher than average crustal material. Low Cr and Ni, together with enriched and fractionated REE (displaying negative Eu-anomalies), distinguish the Malene QCG from published accounts of most other Archaean sedimentary rocks. Furthermore, all of the above-mentioned trace element characteristics distinguish the QCG from “ordinary” Malene clastic metasediments (quartzites, psammites, and pelites), suggesting a separate origin for the QCG. These data point towards chemically evolved felsic igneous rocks being the source of the QCG. Consequently, we propose that the Malene QCG represent metamorphosed felsic volcaniclastic sediments that underwent hydrothermal alteration by heated seawater prior to metamorphism, which resulted in gain of Mg (and Fe?), loss of alkalis and lime, and possibly Eu and Sr. The overall trace-element characteristics of the QCG (elevated Ga, Zr, Nb, REE, etc.) are features shared by A-type granites and their volcanic equivalents. Such igneous rocks may represent the ultimate source material for the QCG protolith.

Dymek, Robert F.; Smith, Michael S.

1990-11-01

288

Geochemistry of K/T-boundary Chicxulub ejecta of NE-Mexico  

NASA Astrophysics Data System (ADS)

Many K/T sections all over the world contain impact spherules supposed related to the Chicxulub event. This study focus on ejecta layers in NE-Mexican profiles. We carried out systematic XRF and synchrotron radiation measurements on such spherules at the HASYLAB and ANKA facilities as well as microprobe analyses (CAMECA SX50). Area scans on tektite-like material of the Bochil section reveal a pronounced zonation in the inner part, dominated by Ba and Sr whereas secondary CaCO3 dominates in the altered margin. The composition of the spherules from the Mesa-Juan Perez section differ significantly from the Beloc (Haiti) and Bochil tektite glasses. At Mesa-Juan Perez, spherules are either extremely rich in Fe and Ca or consist of smectite, some of those carry carbonate inclusions. Yttrium, La and Ce are zoned within the smectite with concentrations below the detection limit and up to 20 æg/g The Ca-rich inclusions are enriched in Y (up to 35 æg/g) and La (18 æg/g) and, compared to the surrounding smectite, also in Ce (up to 34 æg/g). The Ce enrichment in spherules from the Mesa-Juan Perez section indicates impact-melted carbonates of the Yucatan carbonate platform as possible precursor rocks. Recent investigations focus on the chemistry of melt rock samples from the PEMEX wells Yucatan-6 and Chicxulub-1: Their average composition (mean of 250 data points in wt-percent ) is 61.6 for SiO2, 0.16 for TiO2, 18.07 for Al2O3, 0.01 for Cr2O3, 1.98 for Na2O, 1.5 for FeO, 0.05 for MnO, 0.01 for NiO, 0.31 for MgO, 9.14 for K2O, 3.44 for CaO, and 0.01 for SO2. These results are in some cases comparable to the geochemistry of ejecta glasses, e.g. from Beloc (Haiti).

Harting, M.; Deutsch, A.; Rickers, K.

2003-12-01

289

Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)  

NASA Astrophysics Data System (ADS)

The Phlegrean volcanic district (PVD) in southern Italy is one of the best known volcanic hazard areas in the world. More than 1.5 million people live in close proximity to the volcanic centers. The PVD comprises three volcanic fields: the Campi Flegrei caldera and the islands of Ischia and Procida. We studied volatiles plus major and trace elements in the magma associated with the Solchiaro eruption on the Island of Procida, Italy, to gain a better understanding of the relationship between pre-eruptive volatiles and magmatic evolution. The Solchiaro eruption is one of the more primitive products erupted in the PVD and provides information on the source of later more evolved magmas associated with this volcanic system. The composition of the magma before eruption was determined by analyzing 104 melt inclusions (MIs) in forsteritic olivine, glass embayment plus rim glasses, and high vesciculated glasses selected from 4 representative samples. The composition of MIs was recalculated and ranges from basaltic to trachy-basaltic. Among major elements potassium shows the highest variability, from 0.5 to 6 wt%. MI define a continuous trend based on major and minor element compositions. Embayments matrix glass and high vesciculated glasses define a field that suggests a discontinuous process. Compatible to incompatible trace element ratios in early melts are highly variable and represent the melt phase before or at the very beginning of assimilation-fractional crystallization (FCA) processes. Intermediate melt compositions reflect continuing FCA processes, late melt compositions suggest that the FCA process was aborted before eruption. Volatile contents of early melt are highly variable and reflect source heterogeneities, and the melts are interpreted to be undersaturated. Intermediate melts were volatile saturated and H2O-CO2 contents define a degassing path. Depths of trapping of MI range from 4.4 to 2.2 km, and are calculated based on Newman and Lowenstern (2002) and assuming a pressure gradient of 270 bar/Km. Pressures of crystallization of intermediate melts correlate with magma evolution associated with FCA processes. At the moment of the eruption, melt saturated in volatiles at 8 km continuously lost volatiles during its rapid ascent to the surface. Glass embayments and glass at the crystal/melt interface shows higher volatiles (especially CO2), compared to highly vesiculated matrix glass. Magma compositions relative to some MIs hosted in forsterite-rich olivine show extremely low contents of both K2O and Na2O and high CaO (0.5, 1.90 and 13.89 wt% respectively). Similar compositions have not been previously reported from the PVD but are characteristic of the Aeolian Arc.

Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Hunter, J.

2009-12-01

290

Geochronology, petrogenesis and tectonic significance of peraluminous granites from the Chinese Altai, NW China  

NASA Astrophysics Data System (ADS)

The Paleozoic granites in the Chinese Altai are important for the study of tectonic evolution and crustal growth in the Central Asian Orogenic Belt (CAOB). Four representative peraluminous granitic intrusions were selected for systematic studies of zircon U-Pb and Hf isotopic compositions and whole-rock geochemical and Nd-Sr isotopic analyses. These rocks have high ASI (Alumina Saturation Index, Al2O3/(CaO + Na2O + K2O) = 1.01-1.46 molecular ratios), with 0.6-5.6 wt.% of normative corundum, and are characterized by moderately negative Eu anomalies (Eu/Eu* = 0.38-0.98) and strong depletion in Ba, Nb and Sr elements. Our data suggest that these intrusions were emplaced from 419 to 393 Ma, consistent with a period of intensive magmatic activities and high temperature metamorphism in the Chinese Altai. While in situ zircon Hf isotopic analyses for these granites give predominantly positive ?Hf(t) values (+ 0.8 to + 12.8), a few inherited zircons yield negative ?Hf(t) values from - 12.5 to - 1.53. The U-Pb age and Hf isotopic data of these inherited zircons are similar to that of the widespread metasediments. In addition, the peraluminous granitic rocks have near-zero or negative ?Nd(t) values (- 3.3 to - 0.5) and relatively high initial 87Sr/86Sr ratios (0.7079-0.7266), distinct from those of the I-type granites in the study region, but similar to the Early Paleozoic Habahe sediments. These isotopic compositions suggest that the newly accreted metasediments of Habahe Group may be the major source rock of the peraluminous granites. The geochemical compositions indicate that their precursor magmas were derived from a relatively shallow crustal level (P ? 5 kbar) and zircon saturation temperatures suggest that these granitic intrusions were emplaced at 672-861 °C. The peraluminous granitic magmas were generated by dehydration melting of newly accreted materials, which were possibly brought to at least middle crustal depth by subduction-related processes in an active margin, and were subsequently molten by strikingly high ambient temperature probably caused by upwelling of the hot asthenosphere associated with ridge subduction in the Paleozoic.

Cai, Keda; Sun, Min; Yuan, Chao; Zhao, Guochun; Xiao, Wenjiao; Long, Xiaoping; Wu, Fuyuan

2011-11-01

291

Geochemistry of oceanic igneous rocks - Ridges, islands, and arcs - With emphasis on manganese, scandium, and vanadium  

USGS Publications Warehouse

A database on a number of elements in oceanic volcanic rocks is presented, including the principal major-element oxides - SiO2, TiO2, Al2O3, Fe2O3(T), MnO, MgO, CaO, Na2O, K2O, and P2O5 (where T refers to total iron) - and the trace elements - Ba, Ce, Cr, Cu, Ni, Sc, Sr, V, Pb (mainly by isotope dilution), Yb, Zn, and Zr. Interpretations are given for transition metals, with emphasis on Mn, Sc, and V, in order to determine the concentration of the elements in primitive melts and assess their trends in magmatic differentiation. Transition metals are not enriched in plagioclase, so all are incompatible with pure plagioclase removal - that is, they become enriched in the melt. Both Cr and Ni are known to be highly compatible with olivine separation - i.e., they are depleted in the melt early in differentiation. Also, Sc is compatible with clinopyroxene (Cpx) removal from the melt and is depleted by separation of Cpx. Copper does not fit well in any of the principal silicates, but Cu, like Ni, is greatly enriched in sulfides that may remain in the source or separate from the magma. Decreasing Ni abundances and increasing Cu contents during differentiation are a sign of olivine separation. In the analysis presented herein, V - in the absence of Cpx separation - is found to behave remarkably like the moderately incompatible element Zn, and these two elements add to the list of element pairs of similar incompatibility whose ratios are insensitive to differentiation and to submarine weathering as well. Both are enhanced in titanomagnetite, so both would he compatible during titanomagnetite separation. When Cpx separates, however, V becomes compatible like Sc, but Zn remains incompatible. Thus, decreasing V (and Sc) contents and increasing Zn contents during differentiation are a sign of Cpx separation. Manganese often behaves much like Zn and therefore is moderately incompatible, but Mn is less compatible than Zn and V in titanomagnetite. Thus, decreasing Zn and V with increasing Mn is an indication of titanomagnetite removal. Dual compatible and incompatible trends with differentiation are found chiefly for Cu, Sc, and Sr. Distinguishing mid-ocean ridge basalts (MORB), oceanic-island volcanic rocks (OIV), and island-arc volcanic rocks (IAV) may be accomplished by plots of Ce/Yb versus Ba/Ce, where OIV plot to higher values of Ce/Yb than do MORB, and IAV data plot to higher values of Ba/Ce than do those of MORB. These ratios do not seem to be significantly affected by submarine weathering.

Doe, B. R.

1997-01-01

292

Diffusion-Reaction Between Basaltic Andesite and Gabbro at 0.5 GPa: an Explanation for Anorthitic Plagioclase?  

NASA Astrophysics Data System (ADS)

Despite the remarkably smooth variation in bulk composition of erupted lavas at Arenal volcano (1968-2003), mineral compositions vary widely. Plagioclase ranges from An52 to An95 while Cr2O3 in CPX varies from 0.7 to 0.05 wt % (Streck et al., 2003). To address the question "how do bulk compositions remain near-steady-state while crystal compositions vary widely," we have performed 2 diffusion-reaction experiments in the piston cylinder at 0.5 GPa. These juxtaposed Arenal basaltic andesite AR-8 at 1200° C with a Stillwater Complex gabbro, lying in a thermal gradient toward the piston. In one experiment, we synthesized a glass-plagioclase (An67-75) aggregate of AR-8 in a graphite-Pt-Ti capsule at P-T, polished one end, dried tracer solutions of 45Ca, 6Li, 84Sr and 136Ba on its surface, and juxtaposed it with gabbro for 13 days. Profiles of bulk composition as a function of distance from the interface show that AR-8 gains Al2O3, MgO and CaO from the gabbro and loses Na2O, K2O, SiO2 and FeO to it. Notably, a plagioclase rich (65%) layer develops at the interface between the two materials as CPX disappears. This layer and the compositional profiles are reproduced by diffusion-reaction models using IRIDIUM (Boudreau, 2003). Plagioclase at the interface develops a texture of homogeneous anorthitic cores (An90) that abruptly shift to 10? m rims having compositions (An67) in Na-Ca exchange equilibrium with the co-existing melt. A beta track map shows that 45Ca is incorporated into the plagioclase cores while SIMS analyses indicate isotopic equilibration between core and melt. Thus, these anorthitic plagioclase result from diffusion-reaction with efficient chemical communication between the melt and the plagioclase core. Microchannels cutting through the rim, rather than solid-state diffusion, appear to control re-equilibration. Other observations from the experiment parallel Arenal lavas: Mg# variation in OPX is small in both experiments and lavas while profiles of Cr show that significant amounts of Cr move from gabbro to AR-8, possibly explaining Cr2O3 variations in Arenal CPX. The near-steady-state behavior at Arenal could reflect a flux balance between ascending magmas and melt from the surrounding crust reflecting diffusion-reaction.

Lundstrom, C. C.; Boudreau, A. E.; Pertermann, M.

2004-12-01

293

Constraining Major Element Fractionation in an Alkali Gabbroic Sill using Mass Balance Modelling.  

NASA Astrophysics Data System (ADS)

The Ringkallen hill gabbro (RHG) is an ~225m thick layered alkali gabbroic sill in central Sweden. It is a part of the much larger ~1.26 Ga Ulvö Gabbro complex, a series of 200-300m thick saucer-shaped alkali gabbroic intrusions with diameters of 30-80km. The anorthite (An.) content of plagioclase decrease gradually from ~70% at the margins to ~45% at the Sandwich Horizon, and the bulk composition of the RHG calculated from whole-rock analyses closely resembles the chilled margin composition, suggesting that the intrusion crystallised from a single pulse of magma in a closed system. Mass balance calculations were used to calculate the evolution of the supernatant liquid to the point where 90% of the intrusion had crystallised. The results show a successive decrease in the concentration of Al2O3 and MgO, an increase in MnO, TiO2, Na2O and K2O, while the concentrations of SiO2 and CaO remain stable. The major element variations of the calculated supernatant liquid were used to constrain the proportion between cumulus phases and crystallising liquid fraction (CLF). By iteratively changing the bulk partition coefficient by varying the proportion between the cumulus phases and the CLF for a given interval, the best estimate was found using root mean square method. The results indicate that the intrusion crystallised with a CLF of ~0.8 for the first 50% of crystallisation, and the next 30% had an estimated CLF of ~0.6 and the final 10% had ~0.8 CLF. At the point where 90% of the intrusion had crystallised, the stratigraphy contained only ~25% cumulus minerals. In strong contrast, simulation of the stratigraphic decrease in An. content of plagioclase by thermodynamic modelling suggests more than 70% fractional crystallisation. The strong stratigraphic decrease of plagioclase An. content is inconsistent with the modest change of the An. content of the calculated liquid. This suggests that the linear partitioning in the binary plagioclase system for these alkali gabbroic intrusions may be different from experimental results.

Ek, M.; Hogmalm, K. J.; Larson, S.-Å.

2012-04-01

294

The influence of multivariate analysis methods and target grain size on the accuracy of remote quantitative chemical analysis of rocks using laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) was used to quantitatively analyze 195 rock slab samples with known bulk chemical compositions, 90 pressed-powder samples derived from a subset of those rocks, and 31 pressed-powder geostandards under conditions that simulate the ChemCam instrument on the Mars Science Laboratory Rover (MSL), Curiosity. The low-volatile (<2 wt.%) silicate samples (90 rock slabs, corresponding powders, and 22 geostandards) were split into training, validation, and test sets. The LIBS spectra and chemical compositions of the training set were used with three multivariate methods to predict the chemical compositions of the test set. The methods were partial least squares (PLS), multilayer perceptron artificial neural networks (MLP ANNs) and cascade correlation (CC) ANNs. Both the full LIBS spectrum and the intensity at five pre-selected spectral channels per major element (feature selection) were used as input data for the multivariate calculations. The training spectra were supplied to the algorithms without averaging ( i.e. five spectra per target) and with averaging ( i.e. all spectra from the same target averaged and treated as one spectrum). In most cases neural networks did not perform better than PLS for our samples. PLS2 without spectral averaging outperformed all other procedures on the basis of lowest quadrature root mean squared error (RMSE) for both the full test set and the igneous rocks test set. The RMSE for PLS2 using the igneous rock slab test set is: 3.07 wt.% SiO 2, 0.87 wt.% TiO 2, 2.36 wt.% Al 2O 3, 2.20 wt.% Fe 2O 3, 0.08 wt.% MnO, 1.74 wt.% MgO, 1.14 wt.% CaO, 0.85 wt.% Na 2O, 0.81 wt.% K 2O. PLS1 with feature selection and averaging had a higher quadrature RMSE than PLS2, but merits further investigation as a method of reducing data volume and computation time and potentially improving prediction accuracy, particularly for samples that differ significantly from the training set. Precision and accuracy were influenced by the ratio of laser beam diameter (˜490 ?m) to grain size, with coarse-grained rocks often resulting in lower accuracy and precision than analyses of fine-grained rocks and powders. The number of analysis spots that were normally required to produce a chemical analysis within one standard deviation of the true bulk composition ranged from ˜10 for fine-grained rocks to >20 for some coarse-grained rocks.

Anderson, Ryan B.; Morris, Richard V.; Clegg, Samuel M.; Bell, James F.; Wiens, Roger C.; Humphries, Seth D.; Mertzman, Stanley A.; Graff, Trevor G.; McInroy, Rhonda

2011-10-01

295

Estimating mantle temperature from a global comparison of seismic models and the petrology of mid-ocean-ridge basalts  

NASA Astrophysics Data System (ADS)

Inferring mantle temperature and composition is one of the primary applications of seismic tomography. Mantle temperature and composition also strongly influence the petrology of mid-ocean-ridge basalts (MORBs) erupted on the seafloor. It is therefore reasonable to hypothesize that a relationship exists between seismological and petrological data. We have investigated whether such a relationship does exist using global seismic models and a new and expanded global compilation of MORB major-element chemistry. Using GeoMapApp and available bathymetry, we first divide the entire mid-ocean-ridge system into 771 individual ridge segments. Petrological data obtained from PetDB form the core of our geochemical database, which is augmented by unpublished analyses and Iceland samples from GEOROC. Each of the 14,493 basalt samples belongs to a particular ridge segment, and after applying fractionation corrections we have values of SiO2, Na2O, FeO, CaO, Al2O3, TiO2, K2O, and P2O5 corrected to 8% MgO for 218 ridge segments. We compare the petrological data (ridge depth, Na8, Fe8, etc.) with global mantle models of shear-wave speed (Kustowski et al., 2008; Panning et al., 2010) and attenuation (Dalton et al., 2008) and with global estimates of topography on the 410-km and 660-km discontinuities (Lawrence and Shearer, 2008). The coarse resolution of the seismic models necessitates spatial averaging of the ridge segments. Indeed, we observe a strong negative correlation between spreading rate and wave speed at 100-km depth that results from resolution limits of the seismic model. Ridge depth and wave speeds at 200-300 km depth are correlated, globally and especially for the Mid-Atlantic Ridge and Southeast Indian Ridge, suggesting that the same factors that control ridge depth and crustal thickness also influence seismic velocity. For several of the mid-ocean ridges, anti-correlation between ridge depth and depth to the 410-km discontinuity is seen, in particular the Southwest Indian Ridge and the Mid-Atlantic Ridge. Such a clear relationship is not found between topography on the 660 and ridge depth. The comparisons also reveal anti-correlation between Fe8 and shear-wave speed at 250-300 km for the Mid-Atlantic Ridge and ~400 km for the East Pacific Rise. Comparison of the petrological data and mantle seismic models provides an opportunity to understand the connection between temperature and composition at depth and processes occurring at the surface.

Dalton, C. A.; Gale, A.; Langmuir, C. H.

2010-12-01

296

Alteration of basaltic glass: Mechanisms and significance for the oceanic crust-seawater budget  

NASA Astrophysics Data System (ADS)

Alteration of basaltic glass to palagonite is characterized by a nearly isomolar exchange of SiO 2, Al 2O 3, MnO, MgO, CaO, Na 2O, P 2O 5, Zn, Cu, Ni, Cr, Hf, Sc, Co and REE for H 2O and K 2O, whilst TiO 2 and FeO are passively accumulated during removal of the remaining cations. The network forming cations Al and Si are removed from the glass in proportion to the gain in Ti and Fe, whilst the other cations do not show a significant relationship to the amount of Ti and Fe accumulation. Sr isotopic data show that during palagonite formation approximately 85% of the basaltic Sr is lost to the hydrous solutions and 40% of seawater Sr is added to the glass, yielding an average loss of the same order of magnitude as of the network forming cations. Losses and gains of oxides yield an average increase of +105% TiO 2. K, Rb, and Cs show high increases, but K/Rb and K/Cs ratios indicate two different alteration processes: (1) formation of palagonite involves a drastic decrease in these ratios, indicating structural similarities between palagonite and smectite; (2) surface alteration of glass is characterized by an increase in K/Rb and K/Cs ratios, probably best interpreted as sorption of alkalies in ratios approximating those of seawater. The total fluxes involved in alteration of glass in the upper portion of the oceanic crust are estimated from the modal abundance of palagonite in the oceanic crust and the abundance of the vein materials smectite and carbonate. Smectite and carbonates act as a sink for a significant portion of the elements liberated up during alteration of basaltic glass except for Na and Al, which are probably taken up by zeolites and/or albite, possibly hidden in the macroscopic estimate of carbonate. Formation of the observed quantity of secondary phases requires additional sources for Si, Fe. Ca and K. K is provided in excess from the inflowing seawater at reasonable water/rock ratios. The remaining excess Ca, Si and Fe required may be derived by alteration of interstitial glass and breakdown of anorthite rich plagioclase and titano-magnetite, and/or by supply of deeper seated metamorphic reactions.

Staudigel, Hubert; Hart, Stanley R.

1983-03-01

297

Geochemical Investigation of Saddlebag Lake Roof Pendant and Lee Vining Intrusive Suite Origins  

NASA Astrophysics Data System (ADS)

Our study is to determine to what extent volcanic rocks from the Saddlebag Lake Roof Pendant (SLRP) represent the erupted complement of the Sierra Nevada Batholith (SNB). SLRP formation is thought to be prior to or synchronous with Sierra Nevada orogeny. Age dates of the SLRP are similar to age dates from the Lee Vining Intrusive Suite (LVIS), so the LVIS may be the plutonic equivalent of the SLRP (Kistler and Fleck 1994). A hypothesized analog between SLRP-LVIS is the Wilson Ridge Pluton (WRP)-River Mountains (RM) complex in southern Nevada, which is a dismembered volcanic complex offset by normal faulting (Honn and Smith, 2008). WRP and RM trace element data from Honn and Smith plot very similar on a Hf-Th-Ta ternary diagram, and Sr and Nd isotope analyses also indicate that the Nevada rocks are co-magmatic. Our goal is to conduct geochemical tests to determine whether the SLRP and LVIS are co-genetic. Our preliminary data support the possibility that the SLRP may provide a window into the magmatic evolutionary processes that led to the development of the LVIS, and the SNB generally. Eighteen samples were collected from the SLRP; major element compositions of whole rocks yield similar weight percents of major oxides for some published data from the LVIS (Bateman et al. 1984). Our SLRP samples, though, trend to higher MgO, Fe2O3, Al2O3, and CaO, lower in SiO2 and Na2O+K2O. If the SLRP and LVIS are indeed related, the SLRP samples may represent some of the less-differentiated liquids from which the LVIS was derived. We were only able to find one basalt (51.2 wgt % SiO2), albeit with very low MgO (2.17 wt %), which may give clues as to the origin of the LVIS. If the mafic enclaves in the LVIS were once liquid, then the SLRP basalts should be comparable to mafic enclaves in composition. We are also analyzing mafic enclaves from the LVIS to explore whether these are liquid precursors to Sierra Nevada Batholith granites.

Wonderly, A.; Canchola, J.; Putirka, K. D.

2009-12-01

298

The Southeast Asian Tin Belt  

NASA Astrophysics Data System (ADS)

The Southeast Asian Tin Belt is a north-south elongate zone 2800 km long and 400 km wide, extending from Burma (Myanmar) and Thailand to Peninsular Malaysia and the Indonesian Tin Islands. Altogether 9.6 million tonnes of tin, equivalent to 54% of the world's tin production is derived from this region. Most of the granitoids in the region can be grouped geographically into elongate provinces or belts, based on petrographic and geochronological features. - The Main Range Granitoid Province in western Peninsular Malaysia, southern Peninsular Thailand and central Thailand is almost entirely made up of biotite granite (184-230 Ma). Tin deposits associated with these granites contributed 55% of the historic tin production of Southeast Asia. - The Northern Granitoid Province in northern Thailand (0.1% of tin production) also has dominant biotite granite (200-269 Ma) but it is distinguished by abundant post-intrusion deformation. - The Eastern Granitoid Province extends from eastern Peninsular Malaysia to eastern Thailand. The Malaysian part is subdivided into the East Coast Belt (220-263 Ma), Boundary Range Belt (197-257 Ma) and Central Belt (79-219 Ma). The granitoids cover a wide compositional range from biotite granite to hornblende-biotite granite/granodiorite and diorite-gabbro. Tin deposits are associated with biotite granite in the East Coast Belt (3% of tin production). The granitoids in the other areas of the Eastern Granitoid Province are barren. - The Western Granitoid Province (22-149 Ma) in northern Peninsular Thailand, western Thailand and Burma has biotite granite and hornblende-biotite granite/granodiorite. Tin deposits are associated with biotite granite, which probably is the dominant phase (14% of tin production). The granitoids of the Indonesian Tin Islands (193-251 Ma) do not permit grouping into geographically distinct units. Main Range-type and Eastern Province-type plutons occur next to each other. Most of the tin deposits are associated with Main Range-type plutons (28% of tin production). Tin-mineralized plutons are characterized by high concentrations of SiO 2, K 2O, Rb, Sn, Th and U, whereas the concentrations of Fe 2O 3, MgO, CaO, Na 2O, Ba and Sr as well as the Fe2O3/FeO ratios are low. Tin-mineralized plutons are also distinguished by high initial 87Sr/86Sr ratios low magnetic susceptibilities.

Schwartz, M. O.; Rajah, S. S.; Askury, A. K.; Putthapiban, P.; Djaswadi, S.

1995-07-01

299

Restite and the compositions of S-type granites  

NASA Astrophysics Data System (ADS)

S-type granites, particularly those emplaced in the upper crust, are generally considered to be the mobilized products of fluid-absent partial melting of metasediments. Entrainment of variable proportions of source material into the magmas has been proposed as one of the major mechanisms controlling geochemical variations in such rocks. We examined the major-element compositions of melts produced in 17 studies of fluid-absent partial melting of aluminous metasediments, at T = 750 1000 ºC and P = 0.3 1.0 GPa. Despite the differences in starting compositions and experimental conditions, the melt compositions are strikingly similar; all are peraluminous leucogranites. The melt compositions were compared with those of 769 Australian S-type granitic rocks, and 211 S-types from the Cape Granite Suite of South Africa, including both volcanic and plutonic rocks. In mol-proportion ternary projections from SiO2 and H2O, plots of A (Al2O3) vs FM (FeO + MgO) vs CNK (CaO + Na2O + K2O) reveal a poor correlation between the natural granite compositions and those of the experimental melts. Only about one third of granites plot within the field defined by the experimental melts. Also, about half the experimental melts plot in a field apparently occupied by no natural granitic rocks. Typically, experimental glasses (even those generated at temperatures of 950 to 1000 °C, and derived from natural, close-to-average metasedimentary compositions) are more leucocratic and aluminous than natural granites. These granite compositions can readily be modelled as mixtures of the experimental melt compositions plus orthopyroxene and garnet or cordierite. If the databases are not skewed towards cumulate compositions, these features suggest that many natural granitic rocks represent mixtures of melts and solid peritectic reaction products (restites). The scant evidence for restitic phases in the petrography of the rocks suggests that these phases dissolve during magma ascent, and react with the melt to form magmatic biotite. It appears that typical metasedimentary melts could resorb/react > 15wt% Grt + Opx before becoming essentially Kfs-free tonalites. Other possibilities are that many granitic rocks are indeed cumulates, or that the S-type melts were hybridized with more mafic magmas. These three possibilities are explored further in this presentation.

Stevens, G.; Clemens, J. D.

2003-04-01

300

Comparison of Results Analyzed by China and European Laboratories for the FOREGS Geochemical Baselines Mapping Samples  

NASA Astrophysics Data System (ADS)

The geochemical data obtained from China and European laboratories for the subsoil samples of FOREGS Geochemical Baselines Mapping Project were compared. 190 sub soil samples were composed from 787 samples remained after the analysis campaign of the FOREGS Project. In addition to the FOREGS elemental analysis package, Au, Pt, Pd, B, Ge, Br, Cl, Se, N, Li and F were also analyzed by using the IGGE 76 element analytical scheme. In this study, the geochemical data statistics, scatter plotting, and the geochemical map compilation techniques were employed to investigate the differences between the analysis results. The results of the two dataset agree extremely well for about 23 elements, viz: SiO2, Sr, Al2O3, Zr, Ba, Fe2O3, Ti, Rb, Mn, Gd, CaO, Ga, MgO, P, Pb, Na2O, Y, Th, As, U Sc, Cr, and Co. The slight proportional errors exist between the datasets for the elements of Ni, K2O, Tb, Tl, Cu, S, Sm, La, Ce, Pr, Nd, Eu, Ho, Er, Tm, Yb, Lu, Ta, Nb, Hf, Dy. For the elements of Cd, Cs, Be, Sb, In, Mo, I, Sn, and Te, their geochemical maps are normal similarity, but the obvious biases exist between the two dataset for the values near the detection limits. The sensitivities of FOREGS analytical methods for W, Bi, Sn, Te, Be, and I are insufficient to produce reportable values at least 80% of the samples. Although the detection limits of Ag for both method are all sufficient to give out enough reportable values, but the big bias were found between the two datasets. This study demonstrated that the comparable analytical data of the certain elements for the global geochemical mapping samples can be achieved by the different laboratories. But for other elements, such as Ag, the further research on the selection of the proper analytical methods and on the quality control methods should to be undertaken and the final recommendation should be commonly obeyed by all participates of the global geochemical mapping program.

Yao, W.; Wang, X.; Nie, L.

2010-12-01

301

Reprint of "Geochemistry and petrogenetic significance of natrocarbonatites at Oldoinyo Lengai, Tanzania: Composition of lavas from 1988 to 2007"  

NASA Astrophysics Data System (ADS)

The natrocarbonatites of Oldoinyo Lengai, Tanzania, are unique in magmatic petrology. The historical activity of Oldoinyo Lengai has seen changes from nephelinitic to natrocarbonatitic character of the emitted magmas. Since 1983 the activity was characterized by the effusion of fluid natrocarbonatite lava from which we have collected and analyzed fresh samples in the summit crater from 1988 to 2007. The available compositional data set forms the basis for presenting and discussing the typical composition and variation of natrocarbonatites and their relationship to the silicate magmas of Oldoinyo Lengai. The "type" natrocarbonatite major and trace element composition is derived for an average of 25 samples with low standard deviation. Oldoinyo Lengai carbonatites are unique in almost all aspects of their petrological and geochemical characteristics and are characterized as extremely alkali-rich, with Na2O + K2O generally about 40 wt.%, and with high CaO contents of 14-18 wt.%. This composition results from the presence of phenocrysts of nyerereite (Na,K)2Ca(CO3)2 and gregoryite (Na,K,Cax)2-x(CO3) dominating the highly porphyritic natrocarbonatite lavas, with sylvite and fluorite as main groundmass minerals. The significance of particular trace element concentrations and ratios of equally incompatible elements (REE, Ba, Sr, Th/U, Nb/Ta, Zr/Hf) is evaluated for models of liquid-liquid separation. In defining a "type" natrocarbonatite composition, we also distinguish special variations in chemical and/or mineralogical compositions as follows: (1) silicate-bearing natrocarbonatites, characterized by the occurrence of nephelinite spheroids, as in the 1993 and 2006 lavas; (2) residual melt compositions as described from the 1988 eruptive period as represented by the aphyric, filter-pressed interstitial melt of solidifying porphyritic lavas; (3) an interlude during 2000 when natrocarbonatites with sylvite and fluorite microcrysts were emitted. After 25 years of mostly mild activity characterized by effusion and spattering of fluid natrocarbonatite lava, the paroxysmal ash eruptions of September 4, 2007, changed dramatically the crater morphology, eruptive dynamics and magma composition of Oldoinyo Lengai. Fresh natrocarbonatites — if present at the bottom of the deep crater pit formed during the 2007-2008 explosive activity — will possibly remain inaccessible for decades.

Keller, J.; Zaitsev, A. N.

2012-11-01

302

Geochemistry and petrogenetic significance of natrocarbonatites at Oldoinyo Lengai, Tanzania: Composition of lavas from 1988 to 2007  

NASA Astrophysics Data System (ADS)

The natrocarbonatites of Oldoinyo Lengai, Tanzania, are unique in magmatic petrology. The historical activity of Oldoinyo Lengai has seen changes from nephelinitic to natrocarbonatitic character of the emitted magmas. Since 1983 the activity was characterized by the effusion of fluid natrocarbonatite lava from which we have collected and analyzed fresh samples in the summit crater from 1988 to 2007. The available compositional data set forms the basis for presenting and discussing the typical composition and variation of natrocarbonatites and their relationship to the silicate magmas of Oldoinyo Lengai. The "type" natrocarbonatite major and trace element composition is derived for an average of 25 samples with low standard deviation. Oldoinyo Lengai carbonatites are unique in almost all aspects of their petrological and geochemical characteristics and are characterized as extremely alkali-rich, with Na2O + K2O generally about 40 wt.%, and with high CaO contents of 14-18 wt.%. This composition results from the presence of phenocrysts of nyerereite (Na,K)2Ca(CO3)2 and gregoryite (Na,K,Cax)2-x(CO3) dominating the highly porphyritic natrocarbonatite lavas, with sylvite and fluorite as main groundmass minerals. The significance of particular trace element concentrations and ratios of equally incompatible elements (REE, Ba, Sr, Th/U, Nb/Ta, Zr/Hf) is evaluated for models of liquid-liquid separation. In defining a "type" natrocarbonatite composition, we also distinguish special variations in chemical and/or mineralogical compositions as follows: (1) silicate-bearing natrocarbonatites, characterized by the occurrence of nephelinite spheroids, as in the 1993 and 2006 lavas; (2) residual melt compositions as described from the 1988 eruptive period as represented by the aphyric, filter-pressed interstitial melt of solidifying porphyritic lavas; (3) an interlude during 2000 when natrocarbonatites with sylvite and fluorite microcrysts were emitted. After 25 years of mostly mild activity characterized by effusion and spattering of fluid natrocarbonatite lava, the paroxysmal ash eruptions of September 4, 2007, changed dramatically the crater morphology, eruptive dynamics and magma composition of Oldoinyo Lengai. Fresh natrocarbonatites — if present at the bottom of the deep crater pit formed during the 2007-2008 explosive activity — will possibly remain inaccessible for decades.

Keller, J.; Zaitsev, A. N.

2012-09-01

303

Geochemical investigation of a semi-continuous extrusive basaltic section from the Deccan Volcanic Province, India: implications for the mantle and magma chamber processes  

NASA Astrophysics Data System (ADS)

Spatial and temporal variations in the geochemistry of an extrusive basaltic section of Deccan traps record progressive changes in mantle melting and crustal filtration and are relevant to understand continental flood basalt (CFB) magmatism. In the present work we have carried out detailed field, petrographic, density and magnetic susceptibility, and geochemical investigations on a small, semi-continuous extrusive section in the eastern Deccan Volcanic Province (DVP) to understand the role of shallow magma chambers in CFB magmatism. Four formations, Ajanta, Chikhli, Buldhana and Karanja crop out in the Gangakhed-Ambajogai area with increasing elevation. Our studies indicate that: (1) the Karanja Formation represents a major magma addition, as indicated by abrupt change in texture, increases in MgO, CaO, Ni, Cr, and Sr, and drastic decreases in Al2O3, Na2O, K2O, Rb, Ba, REE, bulk-rock density and magnetic susceptibility; (2) assimilation fractional crystallization, crystal-laden magmas, and accessory cumulus phases influence the trace element chemistry of Deccan basalts; (3) the predicted cumulate sequence of olivine gabbro-leucogabbro-oxide-apatite gabbro is supported by the observed layered series in a shallow magma chamber within the DVP; (4) the initial magma was saturated with olivine, plagioclase, and augite, and final the pressure of equilibration for the Gangakhed-Ambajogai section basalts is ~2 kbar (~6 km depth); (5) petrophysical parameters act as proxies for magmatic processes; (6) a small layer of oxide-rich basalts may represent the latest erupted pulse in a given magmatic cycle in the DVP; (7) parental basalts to some of the red boles, considered as formation boundaries, might represent small degree partial melts of the mantle; (8) SW Deccan basaltic-types continue into the eastern DVP; and (9) in addition to the magma chamber processes, dynamic melting of the mantle may have controlled DVP geochemistry. The present study underscores the importance of mapping specific stratigraphic intervals in limited areas to understand mantle and magma chamber processes relevant to CFB magmatism.

Vijaya Kumar, Kopparapu; Chavan, Chakradhar; Sawant, Sariput; Naga Raju, K.; Kanakdande, Prachiti; Patode, Sangita; Deshpande, Krishna; Krishnamacharyulu, S. K. G.; Vaideswaran, T.; Balaram, V.

2010-06-01

304

Apatite and clinopyroxene as tracers for metasomatic processes in nepheline clinopyroxenites of Uralian-Alaskan-type complexes in the Ural Mountains, Russian Federation  

NASA Astrophysics Data System (ADS)

Clinopyroxene and apatite are found to trace metasomatic processes in nepheline-bearing clinopyroxenites (tilaites) from the igneous, mafic-ultramafic Uralian-Alaskan-type complexes of Kytlym and Nizhny Tagil, Ural Mountains, Russian Federation. The clinopyroxenites consist predominantly of coarse-grained, partially to totally altered clinopyroxene phenocrysts in a matrix of fine-grained olivine, clinopyroxene, plagioclase, K-feldspar, and nepheline. Apatite occurs as idiomorphic inclusions (<25 ?m) in the clinopyroxene and as xenomorphic grains in the matrix. In the matrix, plagioclase is partially to totally replaced by a fine-grained symplectitic intergrowth of K-feldspar and nepheline most likely due to the influx of an K2O-, Na2O-, and Al2O3-bearing fluid. During conversion of the plagioclase, CaO and SiO2 were partitioned into the fluid. Altered areas in the clinopyroxene phenocrysts are characterized by the redistribution of major and trace elements. This includes depletion in Mg, Rb, and Sr and enrichment in Al, Na, Ba, U, Th, REE except Eu, and HFSE compared to the original magmatic areas in the clinopyroxene. Apatite inclusions in the altered areas of the clinopyroxene and in the matrix are enriched in Cl relative to apatite inclusions in the unaltered areas of clinopyroxene. It is proposed that these rocks experienced a two-stage metasomatic process. Stage 1 was the partial to total alteration of plagioclase to K-feldspar and nepheline due to interaction with an infiltrating (K,Na)Cl-rich brine (most likely late magmatic) with an Al component, which enriched the fluid in CaCl2. Stage 2 consisted of the partial to total chemical alteration of the original magmatic clinopyroxene by this now CaCl2-enriched fluid through the mechanism of coupled dissolution-reprecipitation. This process also chemically altered the apatite inclusions from fluor-chlorapatite to chlor-fluorapatite and redistributed as well as partially removed the titanomagnetite inclusions in the altered areas. This is supported experimentally by the fact that alteration of fluorapatite to Cl-rich apatite can only take place in the presence of CaCl2-bearing fluids and by the fact that in general Fe and Ti, along with most metal cations, are relatively mobile in Cl-rich fluids. If this scenario is correct, the implications from this study are that inclusions of one mineral in a host mineral can be chemically overprinted during metasomatic alteration of the host mineral. While at the same time the original crystal shape and orientation of both the host phase as well as that of the inclusions are preserved.

Krause, Joachim; Harlov, Daniel E.; Pushkarev, Evgeny V.; Brügmann, Gerhard E.

2013-11-01

305

Mineralogic, Petrographic, Mechanical And Physical Properties Of Incesu Ignimbrite (Central Anatolia - Turkey) Used Building Stone In Historical Buildings  

NASA Astrophysics Data System (ADS)

The Central Anatolian Volcanic Province (CAVP) is located in the Central Turkey and one of the four major volcanic provinces in Turkey. It extends 300 km along a NE-SW direction, over a large area (32500 km2). The CAVP includes various volcanic, pyroclastic rocks, which are related to collision volcanism between the Arabian and Eurasian plates, occurred in Neogene, and Quaternary times There are numerous natural stone pits in the CAVP. They have been commonly used in historical building which had been built in the Anatolian Seljuk and Ottoman empires times. The subject of this study is to figure out petrographic, geochemical, some mechanical and physical properties which include Schmidt hardness, density, porosity, water absorption by weight, point load index and failure load.Incesu ignimbrite is subdivided into three levels as lower, middle and upper according to color, welding degree, crystal contents and lithic components. All of the natural stone pits is the upper part which is characterized by grey pinkish in color, poorly welded, high porosity ratios, high amount of lithic fragments and almost 2 m thickness. In terms of the mineralogical composition, it is composed of plagioclase (oligoclase, andesine) + pyroxene (augite, clinoenstatite) + opaque minerals and low amount of amphibole, biotite and quartz. Vitrofiric texture is dominant in upper level. Al2O3 content of the upper level from 12.75-13.96wt%, SiO2 66.70-68.10wt%, MgO 0.73-1.40wt%, Fe2O3 3.77-4.04wt%, TiO2 0.46-0.51wt%, CaO 1.97-2.91wt%, Na2O 3.41-4.29wt%, K2O 3.21-4.20wt%, P2O5 0.13-0.18wt% and LOI 3.65-4.52wt%. Geochemical analyze results reveal that Incesu ignimbrite has rhyolite, rhyodacite-dacite composition, medium to high-K calc-alkaline and peraluminous nature.Building stones can be classified according to their mineralogy, mechanical and physical properties and processing types. Mechanical and physical properties are more significant depending on the stones practice aim. The mean schmidt hardness value of the upper level of Incesu ignimbrite is 35, bulk density ranges between 2.42 - 2.66 g/cm3, mean water absorption by weight is 90%, mean point load strength is 38.2 MPa and failure load is 1890 kgf/cm based on the mechanical and physical test results.

Tasdelen, S.; Korolay, T.; Kadioglu, Y. K.; Kumral, M.

2009-05-01

306

Geochemical, Mineralogical, and Sedimentological Investigation of Phosphorite and its Clay-Rich Mine Tailings from a Phosphate Mine, Togo, West Africa  

NASA Astrophysics Data System (ADS)

Clay-rich mine tailings from phosphate mine operations in Togo West, Africa present major environmental and economic problems. Options for reclamation and restoration of the tailings are limited and are fundamentally restricted due to poorly executed waste management. The major control on the bulk physical properties of the tailings is the mineralogy of the materials. Clay samples from raw phosphate mined were obtained to investigate its sedimentological geochemical, and bulk properties Tailings were also analyzed for similar properties. The phosphatic deposits are Eocene in age, 1 to 10s of meters thick and consist mostly of moderately to poorly sorted phosphatized pellets, formanifera, and other bioclastic debris. Attapulgite occurs interstitially. Moisture contents of clays from the raw phosphate varies from 4.00 to 7.11 wt%. Francolite is the main mineral phase present in the samples analyzed. Geochemically, the rocks show significant enrichment in P2O5 and CaO. P2O5 concentrations vary from approximately 29 to 35.78 wt%. A strong correlation (r2 = 0.92) occurs between CaO and P2O5 abundances indicating that apatite is a major control on the phosphate. A number of heavy metal elements and trace elements occur. Cr, V, Ni, Cu, and Cd are interpreted to be in phosphate minerals, largely apatite. Mean oxide compositions (wt %) are 31.27% P2O5, 43.74% CaO, 9.50% SiO2, 4.30% Al2O3, 2.96% Fe2O3, 0.11 % K2O, 0.19% TiO2, 0.02% MnO, 0.02% MgO, 0.02 % Na2O, and 6.12 % LOI (loss of ignition). Our analysis shows that Cd, U, Th, and F are incorporated into the francolite. We conclude that the phosphorites in Togo formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of calcium fluroapatite during early digenesis at the sediment-water interface. Analysis of the mine tailings show that the purification process leads to the enrichment of certain metals (Cr, Cu, Ni, V, Zn, Ba, Sr, Fe, and Al) in the tailings due to their association with the clay minerals, whereas Cd, Th, and U are enriched in the purified apatite-rich product. Leaching tests show that the solubility of metals generally increases when salinity increases or when pH decreases. Thus, the processing of phosphorites with sea water and the dumping of phosphorite tailings into the sea represent a serious potential risk for the marine ecosystem and for human health through the food chain.

Rezaie Boroon, M.; Ramirez, P. C.; Gnandi, K.

2009-12-01

307

Glass–ceramic scaffolds containing silica mesophases for bone grafting and drug delivery  

Microsoft Academic Search

Glass–ceramic macroporous scaffolds were prepared using glass powders and polyethylene (PE) particles of two different sizes.\\u000a The starting glass, named as Fa-GC, belongs to the system SiO2–P2O5–CaO–MgO–Na2O–K2O–CaF2 and was synthesized by a traditional melting-quenching route. The glass was ground and sieved to obtain powders of specific\\u000a size which were mixed with PE particles and then uniaxially pressed in order to

Chiara Vitale-Brovarone; Francesco Baino; Marta Miola; Renato Mortera; Barbara Onida; Enrica Verné

2009-01-01

308

Late Cretaceous high?K volcanism in the eastern Pontide orogenic belt: implications for the geodynamic evolution of NE Turkey  

Microsoft Academic Search

High?K volcanics were produced in two different Late Cretaceous cycles during the infilling of back?arc basins of the eastern Pontides. The first cycle, represented by shoshonitic trachyandesites and associated pyroclastics, containing high K2O (2.74–4.81 wt?%) and Na2O (3.60–5.51 wt?%), overlies a mid?Cretaceous ophiolitic?olistostromal melange formed during the rifting stage of a back?arc basin (Neotethys). Ar\\/Ar dating of biotite from trachyandesite

Yener Eyübo?lu

2010-01-01

309

Plio–Pleistocene basalts from the Meseta del Lago Buenos Aires, Argentina: evidence for asthenosphere–lithosphere interactions during slab window magmatism  

Microsoft Academic Search

Plio–Pleistocene (3.4–0.125 Ma) post-plateau magmatism in the Meseta del Lago Buenos Aires (MLBA; 46.7°S) in southern Patagonia is linked with the formation of asthenospheric slab windows due to ridge collision along the Andean margin ?6 Ma ago. MLBA post-plateau lavas are highly alkaline (43–49% SiO2; 5–8% Na2O+K2O), relatively primitive (6–10% MgO) mafic volcanics that have strong OIB-like geochemical signatures. Their

Matthew Gorring; Brad Singer; Jason Gowers; Suzanne M. Kay

2003-01-01

310

Pseudo-One-Dimensional Periodic Domain Boundary Structures in Alkali Titanium Oxides  

Microsoft Academic Search

Potassium- and sodium-doped titanium (magnesium) oxides have been prepared from the starting powders of K2O–8TiO2–0.2MgO and a small amount of Na2O. An interesting crystal structure has been discovered, namely the pseudo-one-dimensional periodic domain boundary structure with the average periodic value of M=3.3. The domains show layered structures consisting of corrugated layers of Ti(Mg)O6 octahedra, which could be either Csx(Ti2?x\\/2Mgx\\/2)O4-type or

F. F. Xu; Y. Bando; K. Kurashima; H. Ogawa; K. Inada

2001-01-01

311

Magmatic source enrichment by slab-derived melts in a young post-collision setting, central Mindanao (Philippines)  

Microsoft Academic Search

Central Mindanao was the locus of a Pliocene (4–5Ma old) arc–arc collision event followed by basaltic to dacitic magmatism starting at 2.3Ma, representing the most voluminous volcanic field in the Philippines. Lava compositions range from calc-alkaline to shoshonitic. Adakites and Nb-enriched basalts are among the magmatic products. All the lavas are Na-rich (up to 4.88%), with Na2O\\/K2O ratios from 2.5

Fernando G. Sajona; René C. Maury; Manuel Pubellier; Jacques Leterrier; Hervé Bellon; Joseph Cotten

2000-01-01

312

Computer model for a multicomponent slag-forming mixture melt: Relation between its atomic structure and physicochemical properties  

NASA Astrophysics Data System (ADS)

Experimental data on the density are used to perform molecular dynamics simulation (for the first time) of the multicomponent melt of a commercial slag-forming SiO2-CaO-Al2O3-MgO-CaF2-Na2O-K2O-FeO mixture using an ionic bond model. The simulation results are discussed and compared to available experimental and calculated data. The developed model exhibits a weak temperature dependence of the melt structure. A high diffusion mobility of fluorine ions and alkali metal ions as compared to other elements is revealed.

Gel'Chinskii, B. R.; Belashchenko, D. K.; Dul'Dina, E. V.; Lozovskii, E. P.

2011-02-01

313

Experimental study of partitioning of tantalum, niobium, manganese, and fluorine between aqueous fluoride fluid and granitic and alkaline melts  

Microsoft Academic Search

This study presents a new set of quantitative experimental data on the partitioning of Ta, Nb, Mn, and F between aqueous F-bearing\\u000a fluid and water-saturated, Li- and F-rich haplogranite melts with varying alumina\\/alkali content at T = 650–850 °C and P = 100 MPa. The starting homogeneous glasses were preliminary obtained by melting of three gel mixtures of K2O-Na2O-Al2O3-SiO2 composition

G. P. Borodulin; V. Yu. Chevychelov; G. P. Zaraysky

2009-01-01

314

K, Rb and Sr abundances and Sr isotopic composition of the Tanzawa granitic and associated gabbroic rocks, Japan: low-potash island arc plutonic complex  

Microsoft Academic Search

The granitic and associated gabbroic rocks of the Tanzawa plutonic complex of Miocene age occurring in the northern part of the Izu-Bonin arc are characterized by low abundances of K (229-6790 ppm) and Rb (0.414-12.1 ppm), low K2O\\/Na2O ratios (0.037-0.21), moderately high K\\/Rb ratios (541-630), low Rb\\/Sr ratios (0.00137-0.0579) and low initial 87Sr\\/86Sr ratios (0.70332-0.70372). This indicates that acid to

Kyoichi Ishizaka; Takeru Yanagi

1977-01-01

315

SPECTRAL ANALYSIS OF ORIGINAL AND RESTAURATED ANCIENT PAPER FROM ROMANIAN GOSPEL  

Microsoft Academic Search

A complete characterization of Romanian Gospel from 1740, has been carried out including X-ray fluorescence (EDXRF), induced coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transformed infrared spectroscopy (FTIR) and thermal analysis (DTA-TGA-DSC). The analysis of the paper showed the presence of Fe2O3, CaCO3, ZnO, BaSO4, SrCrO4, K2O, Na2O, Al2O3, Ca3(PO4)3 and also some organic trace due to.

R. M. ION; M. L. ION; V. I. R. NICULESCU; I. DUMITRIU; R. C. FIERASCU; G. FLOREA; C. BERCU; S. SERBAN

316

Deciphering the source and contamination history of peraluminous magmas using ? 18 O of accessory minerals: examples from garnet-bearing plutons of the Sierra Nevada batholith  

Microsoft Academic Search

Peraluminous granitoids provide critical insight as to the amount and kinds of supracrustal material recycled in the central\\u000a Sierra Nevada batholith, California. Major element concentrations indicate Sierran peraluminous granitoids are high-SiO2 (68.9–76.9) and slightly peraluminous (average molar Al2O3\\/(CaO + Na2O + K2O)=1.06). Both major and trace element trends mimic those of other high-silica Sierran plutons. Garnet (Grt) in the peraluminous\\u000a plutons is almandine–spessartine-rich and

Jade Star Lackey; John W. Valley; Hans J. Hinke

2006-01-01

317

Optical studies in gamma-irradiated commercial soda–lime silicate glasses  

Microsoft Academic Search

Optical absorption measurements of gamma-irradiated (60Co) commercial soda–lime silicate (SLS) glasses were performed at room temperature (RT) to detect and characterize the induced radiation damage in these materials. Isothermal bleaching (RT–723K) of the radiation-induced defects, followed the irradiation of samples. In glasses containing different amount of the glass-network modifiers (Na2O,K2O) and some multivalent transition metal cations (Fe2+\\/Fe3+,Ni2+ and\\/or Mn2+) three

M. Suszynska; B. Macalik

2001-01-01

318

The physicochemical conditions of diamond formation in the mantle matter: experimental studies  

Microsoft Academic Search

Experimental studies of diamond formation in the alkaline silicate-carbon system Na2O–K2O–MgO–CaO–Al2O3–SiO2–C were carried out at 8.5 GPa. In accordance with the diamond nucleation criterion, a high diamond generation efficiency (spontaneous mass diamond crystallization) has been confirmed for the melts of the system Na2SiO3–carbon and has been first established for the melts of the systems CaSiO3–carbon and (NaAlSi3O8)80(Na2SiO3)20–carbon. It is shown

Yu. A. Litvin

2009-01-01

319

Early Proterozoic crustal evolution: Geochemical and Nd?Pb isotopic evidence from metasedimentary rocks, southwestern North America  

Microsoft Academic Search

Early Proterozoic (1.8-1.7 Ga) metasedimentary rocks in northern New Mexico and southern Colorado, USA, can be divided into turbidite successions (commonly volcanogenic) associated with mafic\\/felsic metavolcanic successions (e.g., Irving Fm.) and stable shelf quartzite-pelite successions of shallow marine origin (e.g., Hondo Gp.). Metapelites from the turbidite successions reported here have low K2O\\/Na2O, low Th\\/U (<3.0), low to moderate Th\\/Sc (0.1-0.6),

S. M. McLennan; S. R. Hemming; S. R. Taylor; K. A. Eriksson

1995-01-01

320

An enriched mantle source for potassic basanites: evidence from Karisimbi volcano, Virunga volcanic province, Rwanda  

Microsoft Academic Search

Lavas from Karisimbi, the largest volcano in the Virunga province in the Western Branch of the African rift on the Zaire-Rwandan border, constitute a suite of mafic potassic basanites and more evolved potassic derivatives. All of the lavas are potassic with K2O\\/Na2O=1, and enriched in incompatible elements, with chondrite normalised (La\\/Yb)n>18 and Nb\\/Zr>0.25. The 87Sr\\/86Sr and 143Nd\\/144Nd ratios reflect these

N. W. Rogers; M. Mulder; C. J. Hawkesworth

1992-01-01

321

An enriched mantle source for potassic basanites: evidence from Karisimbi volcano, Virunga volcanic province, Rwanda  

Microsoft Academic Search

Lavas from Karisimbi, the largest volcano in the Virunga province in the Western Branch of the African rift on the Zaire-Rwandan border, constitute a suite of mafic potassic basanites and more evolved potassic derivatives. All of the lavas are potassic with K2O\\/Na2O>=1, and enriched in incompatible elements, with chondrite normalised (La\\/Yb)n>18 and Nb\\/Zr>0.25. The 87Sr\\/86Sr and 143Nd\\/144Nd ratios reflect these

N. W. Rogers; M. de Mulder; C. J. Hawkesworth

1992-01-01

322

Geochemistry, petrogenesis and radioactivity of El Hudi I-type younger granites, South Eastern Desert, Egypt  

Microsoft Academic Search

The present study deals with geochemical characteristics and petrogenesis of three younger granite varieties (coarse-grained\\u000a biotite-muscovite granites (CBG), garnetiferous muscovite granites (GMG) and Abu Aggag biotite granites (AAG)) in El-Hudi\\u000a area, east of Aswan, southeastern desert of Egypt. Mineral chemistry and whole rock chemistry data revealed that all granites\\u000a have high SiO2 (70.8-74.7 wt.%), Al2O3 (12.8-14.3 wt.%), Na2O and K2O (>3.2 wt.%) contents

Ashraf Emam; Nasser M. Moghazy; Anas M. El-Sherif

2011-01-01

323

Geochemistry of black shales from the Lower Cretaceous Paja Formation, Eastern Cordillera, Colombia: Source weathering, provenance, and tectonic setting  

NASA Astrophysics Data System (ADS)

The major and trace element characteristics of black shales from the Lower Cretaceous Paja Formation of Colombia are broadly comparable with those of the average upper continental crust. Among the exceptions are marked enrichments in V, Cr, and Ni. These enrichments are associated with high organic carbon contents. CaO and Na2O are strongly depleted, leading to high values for both the Chemical Index of Alteration (77 96) and the Plagioclase Index of Alteration (86 99), which indicates derivation from a stable, intensely weathered felsic source terrane. The REE abundances and patterns vary considerably but can be divided into three main groups according to their characteristics and stratigraphic position. Four samples from the lower part of the Paja Formation (Group 1) are characterized by LREE-enriched chondrite-normalized patterns (average LaN/YbN = 8.41) and significant negative Eu anomalies (average Eu/Eu? = 0.63). A second group of five samples (Group 2), also from the lower part, have relatively flat REE patterns (average LaN/YbN = 1.84) and only slightly smaller Eu anomalies (average Eu/Eu? = 0.69). Six samples from the middle and upper parts (Group 3) have highly fractionated patterns (average LaN/YbN = 15.35), resembling those of Group 1, and an identical average Eu/Eu? of 0.63. The fractionated REE patterns and significant negative Eu anomalies in Groups 1 and 3 are consistent with derivation from an evolved felsic source. The flatter patterns of Group 2 shale and strongly concave MREE-depleted patterns in two additional shales likely were produced during diagenesis, rather than reflecting more mafic detrital inputs. An analysis of a single sandstone suggests diagenetic modification of the REE, because its REE pattern is identical to that of the upper continental crust except for the presence of a significant positive Eu anomaly (Eu/Eu? = 1.15). Felsic provenance for all samples is suggested by the clustering on the Th/Sc Zr/Sc and GdN/YbN Eu/Eu? diagrams. Averages of unmodified Groups 1 and 3 REE patterns compare well with cratonic sediments from the Roraima Formation in the Guyana Shield, suggesting derivation from a continental source of similar composition. In comparison with modern sediments, the geochemical parameters (K2O/Na2O, LaN/YbN, LaN/SmN, Eu/Eu?, La/Sc, La/Y, Ce/Sc) suggest the Paja Formation was deposited at a passive margin. The Paja shales thus represent highly mature sediments recycled from deeply weathered, older, sedimentary/metasedimentary rocks, possibly in the Guyana Shield, though Na-rich volcanic/granitic rocks may have contributed to some extent.

Campos Alvarez, N. O.; Roser, B. P.

2007-04-01

324

Geochemistry and degassing systematics of silicate magma at Ol Doinyo Lengai, Tanzania  

NASA Astrophysics Data System (ADS)

Ol Doinyo Lengai (OL) volcano is unique in that it produces natro-carbonatite lavas. However, every ~25 years the volcano explosively erupts nephelinitic ash. OL entered an explosive phase in September 2007, which lasted until November 2008, and carbonatite activity resumed early in 2009. This study assesses the composition of the 2007-2009 eruptive products and volatiles to characterize degassing and magmatic processes during the explosive eruption. Ash samples collected in 2008 and 2009 are extremely crystal-rich with scarce scoria. Bulk compositions show that the ash is dominated by alkali- and volatile-rich silicate ash with a secondary carbonatite component (SiO2 37.3%, CO3 4.3%, MgO 1.8%, CaO 15.4%, Na2O 11.2%, K2O 3.5%, S 0.14%, Cl 0.20%). Electron microprobe analyses of vesicular scoria show that the matrix glass (SiO2 41.0%, Na22 but enriched in incompatible elements compared to nepheline-hosted glass inclusions (SiO2 43.2%, Na2O 15.8%). S correlates positively with Cl and F in nepheline-hosted glass inclusions (S 0.2-0.4%, Cl 0.3-0.5%, F 0.3-0.8%) showing that these species behaved incompatibly and were not saturated in the parental melt. Matrix glass extends to higher S concentrations (up to 0.7%) at relatively constant Cl and F (Cl ~0.5%, F ~0.7%) resulting in increasing S/Cl and S/F in the residual melt. This is interpreted to reflect Cl and F saturation in the melt due to further crystallization and partitioning of these species into the gas phase while S was undersaturated. Reflectance FTIR shows that the matrix glass has no detectible H2O and ~3% CO2. Glass inclusions have <1.8% H2O based on a calibration for basaltic glasses [1] and up to 7.5% CO2. The OL magma was therefore initially H2O-poor and CO2-rich and degassed <1.8% H2O and <4.5% CO2 between glass inclusion entrapment and eruption. The average S isotope composition of juvenile rock products is -0.7‰ (vs. CDT), which is MORB-like [2]. The ratio of H2S/SO2 in fumarolic gases is ~26, with isotope compositions of H2S = +1.1‰ and SO2 = -0.2 to +1.1‰. At gas equilibrium temperatures of 500°C [3] SO2 should be enriched in 34S relative to H2S by ~6.5‰. The more depleted SO2 values can be explained by partial SO2 dissolution/precipitation in the shallow carbonatite reservoir as 34S enriched sulfate. A SO2 flux of 1.6-1.9 tons/day was measured in June 2009, during renewed effusive carbonatite activity. The CO2/SO2 ratio of ~700 measured in plume gas using an automated bubbler results in a CO2 flux of 766 to 909 tons/day. The very low SO2 fluxes observed at OL during the period 2005-2008 (<10 tons/day), and 2009 are attributed to 1) high S solubility in the silicate melt, and 2) to S dissolution in the shallow carbonatite reservoir. These results have important implications for monitoring, degassing, and volatile budgets for OL as well as other silica undersaturated magmas in the East African Rift. [1] King,P.L.et al. (2006).GAC-MAC mtg, 31: 77. [2] Sakai, H., et al (1984). Geochim. Cosmochim. Acta, 48: 2433-2441. [3] Fischer et al., AGU Fall 09 abstract.

de Moor, J.; Fischer, T. P.; King, P. L.; Hilton, D. R.; Sharp, Z. D.; Barry, P. H.; Ramirez, C.; Mangasini, F.

2009-12-01

325

The composition of Yakutian diamond-forming liquids  

NASA Astrophysics Data System (ADS)

Microinclusions in natural diamonds represent a bulk sample of fluids/melts from which they crystallized [e.g. Navon et al., 1988], and provide a unique opportunity to characterize diamond-forming liquids and to understand their origin and evolution within the mantle. Here we report the composition of microinclusions in Yakutian diamonds (fibrous, cloudy, coated). Diamonds were recovered from several major industrial kimberlite pipes (Udachnaya, Internatsionalnaya, Yubileinaya, Sytyksnskaya, Aikhal) and alluvial deposits (Ebelyakh area). The major-element compositions of the subsurface microinclusions have been determined using EDS. All analyses are normalized to 100% on a carbon free basis (with excess oxygen for chlorine). Major- and trace-element compositions of the bulk microinclusion populations have been quantitatively analyzed by LA-ICP-MS. The abundances of carbonates, water and silicates in the diamonds were determined by FTIR. The major-element composition of microinclusions in Yakutian diamonds shows wide variations. Some important inter-element correlations between silica and chlorine content and the water/carbonate ratio of microinclusions are observed. In comparison with the worldwide database, the fluids in most of the studied diamonds define a continuous range of carbonatitic to silicic compositions and only a few fall into the starting interval of the carbonatitic to saline range. The silicic microinclusions are rich in water, SiO2, Al2O3, K2O and P2O5. The silicic end-member, constrained from combined EDS and FTIR data, carries ~80 wt % silicates, 11 wt % water, 6 wt % carbonates and 3 wt % apatite. Carbonatitic microinclusions are rich in carbonate, CaO, MgO and FeO. The carbonatitic end-member comprises 82 wt% carbonates, 12 wt% silicates, 2 wt% water, 2 wt% apatite and 1 wt% halides. Samples with saline components are slightly enriched in water, K2O, Na2O and Cl. The most saline inclusions in Yakutian diamonds consist of 49 wt% carbonates, 25 wt% halides, 12 wt% silicates, 9 wt% water, 3 wt% sulfides and 2 wt% apatite. The trace-element compositions of the microinclusions are generally similar to those of kimberlites and carbonatites, but there are significant differences in major elements. The bulk analyses of the microinclusions in Yakutian diamonds have smooth PM-normalized patterns for the LILE. Some samples show enrichment in Cs. The relative abundance of K in the fluids is significantly higher than observed in the host kimberlite and carbonatites. The pattern of HFSE in the microinclusions shows some depletion in Ti, Zr and Hf relative to Ta, Nb and Mo. The REE pattern reveals low abundances of the heavy REE and high light REE concentrations. The La/Dy of the micro-inclusion populations varies widely, gradually decreasing from carbonatitic to silicic compositions. Many samples with carbonatitic composition have a negative anomaly in Y. Yakutian diamonds have low contents of transition metals and most of them are significantly depleted in Ni and Co. The observed geochemical features are consistent with a genetic link between the diamond-forming fluids and ephemeral carbonatitic liquids (fluids/melts) which sometimes may be precursors of the host kimberlite. These fluids/melts may originate either from the metasomatic influx of volatile agents and/or from partial melting of previously carbonated eclogites and peridotites. Some elemental variations may be explained by the fractional crystallization of such fluids/melts, or mixing between liquids with different compositions. These processes result in diamond formation and kimberlite generation.

Zedgenizov, D. A.; Shatsky, V. S.; Araujo, D.; Griffin, W. L.; Ragozin, A. L.

2009-04-01

326

Calcium-sodium antagonism on the frog's heart: a voltage-clamp study.  

PubMed Central

1. In double sucrose-gap voltage-clamped frog atrial fibres the influence of [Ca]o and [Na]o on membrane current and contraction was investigated. 2. The slow (secondary) inward current varied with [Ca]o but was almost insensitive to changes in [Na]o. In contrast, the phasic (transient) contraction initiated by the slow inward current was affected by both [Ca]o and [Na]o. 3. With moderate changes of [Ca]o and [Na]o from normal, the strength of phasic contraction at a given depolarization followed the [Ca]o/[Na]2o ratio approximately. This was best seen at membrane potentials near zero level. 4. Under the same conditions, tonic (sustained) contractions associated with prolonged depolarizations were strictly correlated to the [Ca]o/[Na]2o ratio at any potential. No interrelation between tonic tension and steady-state current was found. 5. With extensive changes in [Ca]o and [Na]o, the sensitivity of both phasic and tonic tension to the [Ca]o/[Na]2o ratio declined, the negative effect of [Na]o becoming smaller than was expected from this ratio. 6. In Na-free choline-Ringer, a strong contracture developed followed by a spontaneous relaxation. Starting from the relaxed state, application of depolarizing clamps gave rise to phasic contractions with a very slow relaxation while tonic contractions were apparently lacking. 7. The results are interpreted in terms of an energy-dependent carrier mechanism exchanging one Ca for two Na ions across the cell membrane. The model implies a strong asymmetry in the rate constants governing the chemical reactions on both sides of the membrane. The system is thought to operate close to equilibrium at any potential, thereby determining the steady level of myoplasmic Ca. The equilibrium itself is considered to shift upon depolarization. Assuming that [Na]i is constant, the steady level of [Ca]i is expected to be proportional to the [Ca]o/[Na]2o ratio, the scale factor being a function of membrane potential. 8. The carrier model suggests the occurrence of a depolarization-induced inward transfer of Ca which might be involved in the generation of tonic contractions. 9. The apparent lack of tonic contractions in the absence of external Na ions may be explained by a suppression of carrier-mediated Ca influx normally occurring upon depolarization. 10. The antagonistic effects of [Ca]o and [Na]o on phasic contraction are understood as being due to alterations of the Ca pumping system rather than changes in slow inward current.

Benninger, C; Einwachter, H M; Haas, H G; Kern, R

1976-01-01

327

The distribution of the valence electron density in predominantly ionic crystals with different Bravais sublattices  

Microsoft Academic Search

Based on the theory of the local-density functional, self-consistent valence electron densities are calculated for CaO with\\u000a a rock-salt lattice, CaF2 with a fluorite lattice, K2O with an antifluorite lattice, and for their constituent sublattices. It is shown that in the crystals with different Bravais\\u000a sublattices, the anionic sublattice is a framework with covalent bonds containing a metal sublattice inside

Yu. N. Zhuravlev; A. S. Poplavnoi

2003-01-01

328

Liming and Fertilization Effects on Triticale (XTriticosecale W.) Yield Between 1999 and 2006  

Microsoft Academic Search

Precipitation amount, distribution and nitrogen (N)-, phosphorus (P2O5)-, potassium (K2O)-, calcium (CaO)-, and magnesium (MgO) fertilization interaction effects were studied on a sandy acidic lessivated brown forest soil; WRB: Haplic Luvisol in the 44 year old Nyírlugos Field Trial (NYFT) in a Hungarian fragile agro-ecosystem in Nyírség region (N: 470 41' 60'' and E: 220 2' 80'') on triticale (X

2009-01-01

329

Geochemical constraints on the petrogenesis of the Paleozoic granitoids of the Sierra de San Luis, Sierras Pampeanas, Argentina  

Microsoft Academic Search

The Paleozoic granitoids of the Sierra de San Luis comprise the Ordovician tonalite suite (OTS; metaluminous to mildly peraluminous calcic tonalite–granodiorites) and granodiorite–granite suite (OGGS; peraluminous calcic to calc-alkaline granodiorite–monzogranites), as well as the Devonian granite suite (DGS; peraluminous alkali-calcic monzogranites) and monzonite–granite suite (DMGS; metaluminous alkali-calcic quartz monzonite–monzogranite±granodiorite, mildly peraluminous alkalicalcic monzogranites). The OTS has relatively high K2O, CaO,

M. G. López de Luchi; Siegfried Siegesmund; Klaus Wemmer; Andre Steenken; Rudolf Naumann

2007-01-01

330

Late Paleozoic granitoid magmatism in Chukotka and its relation to Ellesmerian orogeny in Arctic Alaska and Canada  

NASA Astrophysics Data System (ADS)

Chukotka fold area (Mesozoides) was formed as a result of collision between Chukotka - Arctic Alaska microplate and active margin of Siberian continent [1]. At present the majority of researches distinguish at least three stages of granitoid magmatism of Chukotka Mesozoides: 147-139, 127-100 and 82.4-78.8 Ma [2]. Granites of first two stages intrude metamorphic basement and Paleozoic-Mesozoic fold structures. Formation of Early Cretaceous granitoids are often considered in relation to granite-metamorphic core complexes evolution [3-5]. Intrusion of the third stage granitoid intrusions corresponds to Okhotsk-Chukotka volcanic belt activity. At the same time in several publications there is information of existence of more ancient Paleozoic granitoids. For orthogneisses of East Chukotka there are age estimations 380-320 Ma (U-Pb SHRIMP, [6]). V.V.Akinin [7] showed that protoliths of Velinkenay and Kuekvun plutons have Late Devonian (380-360 Ma) age. Granites of Kibera Peninsula were dated as 439±32 Ma [Rb-Sr method, 8]. Besides basal conglomerates of Carboniferous deposits contain granite pebbles. At the same time on the existing geological maps granites are indicated as Early Cretaceous ones [9]. Thus there are contradictions on the age estimations and scales of Paleozoic and Mesozoic granitoid magmatism manifestation within Chukotka Mesozoides. As a result of this interregional correlations, first of all correlation of Caledonian and Ellesmerian orogenies events in Arctic region, are complicated. So we carried out U-Pb geochronological studies of some reference granitoid plutons of Central Chukotka, located in the cores of antiform structures, composed of Paleozoic deposits, namely granodiorites of Kibera and quartz syenites of Kuekvyun plutons (Kuul and Kuekvyun rises respectively). Granitoids of Kibera pluton (coastal clippings of Kibera Peninsula, coast of East-Siberian Sea) intrude terrigenous Devonian deposits with carbonate units which are overlain with erosion by Permian-Triassic carbonate-terrigenous and sandy-argillaceous deposits. Kibera pluton is composed mainly of Amph-Bi granites and granite-porphyres. Endocontact zone is presented by foliated Bi granodiorites which were dated. Within Kuekvyun Rise [2] in the core of lineated antiform structure Devonian deposits, metamorphosed to amphibolite facies and deformed, are exposed. Earlier such structures were considered as horst-like saliences of Paleozoic cover and crystalline basement, now, as structures of granite-metamorphic core complexes [3-5]. In the central part of antiform there are micaceous and Gar-Bi schists, marbled limestones, Q-Fsp-Ep-Bi-Amph, Bi-Amph-Cpx schists, intruded by subconcordant bodies of Amph-Bi quartz syenites. At the peripheral parts of rise metamorphic complexes are discordantly overlain by terrigenous deposits of Permian(?)-Triassic age. Granodiorites of Kibera pluton (N 69°56' 50.5'', E172°40' 52,1''; SiO2=67.34%, TiO2=0.41%, Al2O3=14.72%, FeO=2.66%, Fe2O3=1.88%, MnO=0.074%, MgO=1.4%, CaO=2.48%, Na2O=3.71%, K2O=3.42%, P2O5=0.232%) have foliated texture, blastogranitic structure and are composed of quartz, plagioclase, potassic feldspar and biotite. Accessory minerals are sphene, allanite, apatite and zircon. Amph-Bi quartz syenites of Kuekvyun pluton (N 68°37'25.4'', E178°28'21,2'', SiO2=63.51%, TiO2=0.40%, Al2O3=16.57%, FeO=2.3%, Fe2O3=1.8%, MnO= 0.056%, MgO=0.99%, CaO=3.6%, Na2O=3.24%, K2O=5.83%, P2O5=0.245%) also have foliated texture, blastohypidiomorphic structure and are composed of plagioclase, potassic feldspar, amphibole, biotite and quartz. Sphene prevails within accessory minerals, allanite, apatite and zircon are also present. U-Pb geochronological studies for Kibera granodiorite are carried out for three microshots (10-15 grains) of most transparent zircon crystals, selected from 85-100 and 100-150 micron fractions. Points of isotope composition of studied microshots form Discordia, which lower intersection with Concordia correspond to age 353±5 Ma (upper intersection, 1183±660 Ma, ???=0.17). U-Pb geochronologica

Luchitskaya, Marina; Sokolov, Sergey; Kotov, Alexander; Katkov, Sergey; Sal'nikova, Elena; Yakovleva, Sonya

2013-04-01

331

Shlykovite KCa[Si4O9(OH)] · 3H2O and cryptophyllite K2Ca[Si4O10] · 5H2O, new mineral species from the Khibiny alkaline pluton, Kola Peninsula, Russia  

NASA Astrophysics Data System (ADS)

New minerals, shlykovite and cryptophyllite, hydrous Ca and K phyllosilicates, have been identified in hyperalkaline pegmatite at Mount Rasvumchorr, Khibiny alkaline pluton, Kola Peninsula, Russia. They are the products of low-temperature hydrothermal activity and are associated with aegirine, potassium feldspar, nepheline, lamprophyllite, eudialyte, lomonosovite, lovozerite, tisinalite, shcherbakovite, shafranovskite, ershovite, and megacyclite. Shlykovite occurs as lamellae up to 0.02 × 0.02 × 0.5 mm in size or fibers up to 0.5 mm in length usually combined in aggregates up to 3 mm in size, crusts, and parallel-columnar veinlets. Cryptophyllite occurs as lamellae up to 0.02 × 0.1 × 0.2 mm in size intergrown with shlykovite being oriented parallel to {001} or chaotically arranged. Separate crystals of the new minerals are transparent and colorless; the aggregates are beige, brownish, light cream, and pale yellowish-grayish. The cleavage is parallel to (001) perfect. The Mohs hardness of shlykovite is 2.5-3. The calculated densities of shlykovite and cryptophyllite are 2.444 and 2.185 g/cm3, respectively. Both minerals are biaxial; shlykovite: 2 V meas = -60(20)°; cryptophyllite: 2 V meas > 70°. The refractive indices are: shlykovite: ? = 1.500(3), ? = 1.509(2), ? = 1.515(2); cryptophyllite: ? = 1.520(2), ? = 1.523(2), ? = 1.527(2). The chemical composition of shlykovite determined by an electron microprobe (H2O determined from total deficiency) is as follows, wt %: 0.68 Na2O, 11.03 K2O, 13.70 CaO, 59.86 SiO2, 14.73 H2O; the total is 100.00. The empirical formula calculated on the basis of 13 O atoms (OH/H2O calculated from the charge balance) is (K0.96Na0.09)?1.05Ca1.00Si4.07O9.32(OH)0.68 · 3H2O. The idealized formula is KCa[Si4O9(OH)] · 3H2O. The chemical composition of cryptophyllite determined by an electron microprobe (H2O determined from the total deficiency) is as follows, wt %: 1.12 Na2O, 17.73 K2O, 11.59 CaO, 0.08 Al2O3, 50.24 SiO2, 19.24 H2O, the total is 100.00. The empirical formula calculated on the basis of (Si,Al)4(O,OH)10 (OH/H2O calculated from the charge balance) is (K1.80Na0.17)?1.97Ca0.99Al0.01Si3.99O9.94(OH)0.06 · 5.07H2O. The idealized formula is K2Ca[Si4O10] · 5H2O. The crystal structures of both minerals were solved on single crystals using synchrotron radiation. Shlykovite is monoclinic; the space group is P21/ n; a = 6.4897(4), b = 6.9969(5), c = 26.714(2)Å, ? = 94.597(8)°, V = 1209.12(15)Å3, Z = 4. Cryptophyllite is monoclinic; the space group is P21/ n; a = 6.4934(14), b = 6.9919(5), c = 32.087(3)Å, ? = 94.680(12)°, V= 1451.9(4)Å, Z = 4. The strongest lines of the X-ray powder patterns ( d, Å- I, [ hkl] are: shlykovite 13.33-100[002], 6.67-76[004], 6.47-55[100], 3.469-45[021], 3.068-57[ bar 1 21], 3.042-45[121], 2.945-62[ 23], 2.912-90[025, 12, 211]; cryptophyllite 16.01-100[002], 7.98-24[004], 6.24-48[101], 3.228-22[ bar 1 09], 3.197-27[0.0.10], 2.995-47[122], 2.903-84[123, 204, bar 1 24, 211], 2.623-20[028, 08, 126]. Shlykovite and cryptophyllite are members of new related structural types. Their structures are based on a two-layer packet consisting of tetrahedral Si layers linked with octahedral Ca chains. Mountainite, shlykovite and cryptophyllite could be combined into the mountainite structural family. Shlykovite is named in memory of Russian geologist V. G. Shlykov (1941-2007); the name cryptophyllite is from the Greek words meaning concealed and leaf that allude to its layered structure (phyllosilicate) in combination with a lamellar habit and intimate intergrowths with visually indistinguishable shlykovite. Type specimens of the minerals are deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.

Pekov, I. V.; Zubkova, N. V.; Filinchuk, Ya. E.; Chukanov, N. V.; Zadov, A. E.; Pushcharovsky, D. Yu.; Gobechiya, E. R.

2010-12-01

332

Geochemistry of the Yangla volcanic rocks and its relationship to Cu mineralization in the Yangla copper deposit, western Yunnan, China  

NASA Astrophysics Data System (ADS)

The Yangla copper deposit is a recently discovered, giant copper deposit with an estimated Cu reserve of about 1,200,000 tons. Development is now underway. Previous studies have reported that the Yangla copper deposit is a VMS-type deposit related to the Yangla volcanic rocks. Volcanic bulk-rock analyses shows high contents of Si (49.3%-58.7%), Na2O (Na2O = 3.3%-4.9%), MgO (MgO = 3.7%-8.6%), and CaO(CaO = 6.8%-9.0%), low TiO2 (TiO2 = 0.9%-2.1%) and K2O(K2O = 0.2%-1.4%) contents. The geochemistry of the volcanic represent forearc basalts. Four molybdenites samples from the ore bodies in the deposit yield Re-Os model ages ranging from 229.7 ± 3.3 Ma to 233 ± 3.4 Ma. The REE distribution patterns and the primitive-mantle-normalized trace element patterns of the volcanic rocks are similar to the ores, indicating the Yangla copper deposit are closely associated with the Yangla volcanic rocks. The results contribute to our understanding of the genesis of the Yangla copper deposit and will guide further exploration in the region.

Yang, Xian; Liu, Jiajun; Zhai, Degao; Han, Siyu; Wang, Huan; Yang, Longbo; Huo, Dongliang

2012-10-01

333

Effect of the Chemical Composition on The Pyroplastic Deformation of Sanitaryware Porcelain Body  

NASA Astrophysics Data System (ADS)

Pyroplastic deformation is the bending of a ceramic specimen caused by gravity during heat treatment. It can be defined as the loss of shape of product during its firing. Pyroplastic deformation is related to properties of liquid phases formed during firing. Therefore, the effect of the chemical composition on the pyroplastic deformation of sanitaryware porcelain was investigated in this study. Systematical compositional arrangements were made according to different combinations of (SiO2/Al2O3) and (Na2O/K2O) ratios by using Seger formula approach. Pyroplastic deformation behaviour of compositions within a controlled firing regime was investigated by using fleximeter. The bodies were also prepared in a special form by slip casting method at laboratory scale in order to determine the pyroplastic deformation of the samples. The experimental results showed that a definite combination at SiO2/Al2O3 ratio of 5 and Na2O/K2O ratio of 4 give the lowest pyroplastic deformation in the porcelain body formulations. The pyroplastic deformation value of this composition was determined as 25 mm which is 44% lower than that of the standard composition (45 mm).

Ye?im Tunçel, Derya; Kerim Kara, Mustafa; Özel, Emel

2011-10-01

334

EFFECTS OF LIME (CAO) ON THE ENDOTOXIN LEVELS OF BIOSOLIDS  

EPA Science Inventory

Lime addition is a common practice for treating biosolids in order to meet EPA 503 requirements for land application. Since this treatment kills the majority of microorganisms, will it increase the level of endotoxins present in biosolids? And, if endotoxin levels are increased, ...

335

?`Caos en la Resonancia 2:3 con Urano?  

NASA Astrophysics Data System (ADS)

The 2:3 resonace with Uranus and 3:2 with Neptune define limits in the semi -major axis interval, where some objects like 7066 Nessus (semi-major axis 24.456 au) has been observed. In this contribution, we describe the dynamics of a mass-less test particle near the critical value of the semi-major axis for each resonance. We analize the structure of the phase space in each case, using the restricted three-body planar approach, for different values of the Jacobi constant. Although this aproximation does not reflect the whole complexity of this region, it constitutes a good first solution, since there are not first or second order orbital resonances with the major planets. For the 2:3 resonance with Uranus, we find a smooth curve of quasi-periodical orbits surrounding the periodic orbit corresponding to the critical value of the semi-major axis. This region is also surrounded by chaotic orbits, probably due to the presence of other conmensurabilities of first or second order with Uranus. At the internal resonance 3:2 with Neptune, the structure of the section surfaces varies with the value of the C constant. In general, periodic orbits are found for the critical semi-major axis, but for other values of the Jacobi constant, which are obtained modifying the eccentricity of the particle orbit, the region is not closed anymore, so the test particle crosses the Neptune orbit, and escapes from this region.

Fernández, S.; Nicotra, M. A.

336

Research of Geochemical Associations of Nephelin Ores  

NASA Astrophysics Data System (ADS)

The instant paper concerns research of distribution petrogenic chemical members in urtit ore body of Kia-Shaltyrsk deposit. Rocks of the deposit are ore for producing alum earth. Actuality of the subject based on outlooks of detection noble metal ore-bearing (Au, Pt, Pd, Rh, Ru) in alkaline rocks of Siberia, including rocks of Kia-Shaltyrsk deposit (Kuznetsk Alatau). The main purpose of analysis of distribution of members is directed to detection of a non-uniformity of distribution of substance and segments enriched with alum earth and noble members. The basic solved problems are following: o Creation regression models of ore body; o Definition of cumulative distribution functions of members in a contour of ore body; o The analysis of the obtained outcomes in geologic terms. For construction regression models the full-scale data was used, which was presented by the results of the spectral and silicate analyses of gold and petrogenic members containing 130 assays arranged in ore body. A non-linear multiparameter model of the ore body based on components of nephelin ore using neural net approach was constructed. For each member the corresponding distribution function is produced. The model is constructed on the following members: Au, Al2O3, SiO2, Fe2O3, CaO, MgO, SO3, R2O ((Na2O+K2O) -1) and losses of burning. The error of model forecasting membersS concentrations was from 0.02 up to 20%. Large errors basically connected with assays located near contact of ore body and ad- jacent strata or with very high concentrations of members; also they can be connected with different genesis of rocks or superposition of other processes. The analysis of concentrations of members and normalised absolute errors of the fore- cast has shown, that all members can be sectioned into two groups: first: Al2O3, SiO2, R2O, Fe2O3 and second: Au, losses of burning, CaO, MgO, SO3. The distribution of 1 gold is tightly connected with calcium and losses of burning and spatially linked with zones of contact of ore body and adjacent wall rocks. Also it is possible to point, that the segments enriched with gold do not coincide with segments of high-alumna rocks but they are phase-opposite. High concentrations of alum earth, earth silicon, alkalis and low contents of ferric oxide, calcium and sulphur determine high-alumina rocks. Thus, one group of members determines high quality of nephelin ore, and the sec- ond U noble metal ore-bearing bound with members aggravating quality of nephelin ore. Therefore, it is possible to draw a conclusion, that the preliminary enrichment of nephelin ore with the help of flotation will allow to receive two kinds of high quality concentrate: aluminous and noblemetal. The research also allows developing ways of a practical solution of a problem of de- terioration quality of nephelin ore with increasing depth and, accordingly, increases its cost price. These problems apparently connected with economical planning of a production activity of the ore mine and the financial state of the alumnus plant. 2

Vulf, M.; Simonov, K.; Sazonov, A.

337

Nepheline Crystallization in Nuclear Waste Glasses: Progress toward acceptance of high-alumina formulations  

SciTech Connect

We have critically compiled and analyzed historical data for investigating the quantity of nepheline (NaAlSiO4) precipitation as a function of composition in simulated nuclear waste glasses. To understand composition we used two primary methods: 1) investigating the Al2O3-SiO2-Na2O ternary with filtering for different B2O3 levels and 2) creating a quadrant system consisting of compositions reduced to two metric numbers. These metrics are 1) the nepheline discriminator (ND) which depends only on the SiO2 content by weight normalized to the total weight of the Al2O3-SiO2-Na2O sub-mixture and 2) the optical basicity (OB) which contains contributions from all constituents in the glass. Nepheline precipitation is expected to be suppressed at high SiO2 levels (ND >0.62) or at low basicities (OB <0.55 to 0.57). Changes in sodium aluminosilicate glass OB due to additions of CaO and B2O3 correlate with observed effects on nepheline formation. We propose that additional composition space is available for formulating high-waste-loading, high-Al¬2O3 nuclear waste glasses when Na2O levels are less than ~0.125 (normalized by weight on the Al2O3-SiO2-Na2O sub-mixture). However, this compositional space is considerably extended to higher Na2O levels when adding >5 wt% B2O3. The OB concept can help further refine regions of nepheline-free glass formation.

McCloy, John S.; Schweiger, Michael J.; Rodriguez, Carmen P.; Vienna, John D.

2011-09-01

338

Tephra study in the Lake Biwa  

NASA Astrophysics Data System (ADS)

Lake Biwa is one of important reservoirs for the volcanic ash in Japan. During 1982-1983, the 1422 m core was drilled in southern basin of the lake (35øX13'06"N, 136øX00'49"E). The most upper part of core was a continuous 250 m thick lacustrine clay and dated as within 430 ka (Meyers et al.,1993; Takemura, 1990). Total of 18 tephra layers were distinguished from the upper 640 m of the core. However, the fore 14 tephra layers were from the most upper 250 m. Pure glass shards were handpicked out from each tephra layer under the microscope and analyzed by the electron microprobe in the IES for chemical compositions. The K2O vs. SiO2 plot of the glass shards was used to verify the source of each tephra layer. Tephra Layer-2 at depth 13.5m with lower SiO2 and higher K2O was supposed from Ulreung-Oki in southern Japan Sea. Furuta (1986) claimed that glass shards of the caldera eruptions in central Kyushu revealed the high alkali contents (K2O + Na2O = 8.8wt%). Therefore, the tephra Layer-4 (K2O =4.6wt%) at depth of 66.85 m can be corresponded to the Aso-4 eruption well, while the tephra Layer-10 (K2O =4.8wt%) and tephra Layer-11 (K2O =4.98wt%) at around 169.2-170.9 m depth can be identified as the product of the Aso-1 eruption. Comparison of chemical compositions of glass shards in tephra layers in Lake Biwa with those in marine cores around Japan (Machida, 1999), they clearly showed that tephra Layer-1 at depth of 12.9 m, tephra Layer-5 at depth of 74.5 m, and tephra Layer-9 at depth of 158.6 m can be correlated with the caldera eruptions of K-Ah, Ata and Ata-Th in southern Kyushu, respectively. However, some tephra layers with lower K2O content (<4 wt%) are hard to distinguish their sources. Advanced isotopic analyses are needed to distinguish their sources in the future.

Fang, K.; Chen, C.; Takemura, K.; Danhara, T.

2004-12-01

339

Reaction of sodium calcium borate glasses to form hydroxyapatite.  

PubMed

This study investigated the transformation of two sodium calcium borate glasses to hydroxyapatite (HA). The chemical reaction was between either 1CaO . 2Na(2)O . 6B(2)O(3) or 2CaO . 2Na(2)O . 6B(2)O(3) glass and a 0.25 M phosphate (K(2)HPO(4)) solution at 37, 75 and 200 degrees C. Glass samples in the form of irregular particles (125-180 microm) and microspheres (45-90 and 125-180 microm) were used in order to understand the reaction mechanism. The effect of glass composition (calcium content) on the weight loss rate and reaction temperature on crystal size, crystallinity and grain shape of the reaction products were studied. Carbonated HA was made by dissolving an appropriate amount of carbonate (K(2)CO(3)) in the 0.25 M phosphate solution. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the reaction products. The results show that sodium calcium borate glasses can be transformed to HA by reacting with a phosphate solution. It is essentially a process of dissolution of glass and precipitation of HA. The transformation begins from an amorphous state to calcium-deficient HA without changing the size and shape of the original glass sample. Glass with a lower calcium content (1CaO . 2Na(2)O . 6B(2)O(3)), or reacted at an elevated temperature (75 degrees C), has a higher reaction rate. The HA crystal size increases and grain shape changes from spheroidal to cylindrical as temperature increases from 37 to 200 degrees C. Increase in carbonate concentration can also decrease the crystal size and yield a more needle-like grain shape. PMID:17486301

Han, Xue; Day, Delbert E

2007-05-08

340

Induced optical absorption of silicate glasses due to gamma irradiation at high temperatures  

Microsoft Academic Search

Gamma radiation-induced optical absorption in 75SiO2–22Na2O–3CaO (wt.%) multi-component glass and in the same glass additionally doped with 0.05wt.% CeO2 has been studied, with irradiations performed at 70, 200, and 350°C, 25kGy\\/h up to a dose of 0.6MGy. For the undoped glass irradiation at 70°C produces strong optical absorption from 700nm down to the UV. Irradiation at 200°C gives a lower

A. Gusarov; S. Huysmans; F. Berghmans; L. Glebova; L. Glebov; E. R. Hodgson

2010-01-01

341

Fabrication and biological characteristics of ?-tricalcium phosphate porous ceramic scaffolds reinforced with calcium phosphate glass  

Microsoft Academic Search

The fabrication process, compressive strength and biocompatibility of porous ?-tricalcium phosphate (?-TCP) ceramic scaffolds\\u000a reinforced with 45P2O5–22CaO–25Na2O–8MgO bioglass (?-TCP\\/BG) were investigated for their suitability as bone engineering materials. Porous ?-TCP\\/BG scaffolds\\u000a with macropore sizes of 200–500 ?m were prepared by coating porous polyurethane template with ?-TCP\\/BG slurry. The ?-TCP\\/BG\\u000a scaffolds showed interconnected porous structures and exhibited enhanced mechanical properties to those

S. Cai; G. H. Xu; X. Z. Yu; W. J. Zhang; Z. Y. Xiao; K. D. Yao

2009-01-01

342

Ar ion damage on the surface of soda-lime-silica glass  

Microsoft Academic Search

Ar ion sputtering is one of the most accepted techniques for depth profiling in practical X-ray photoelectron spectroscopy (XPS) analysis, while this technique is known to be inadequate for quantitative analysis of glass including mobile ions such as soda-lime-silica glass. In this paper, the profile change in soda-lime-silica glass (70.4SiO2, 0.9Al2O3, 7.3MgO, 7.8CaO, 13.6Na2O in mol%) was investigated on the

Yuichi Yamamoto; Kiyoshi Yamamoto

2011-01-01

343

Calcium phosphate invert glass-ceramic coatings joined by self-development of compositionally gradient layers on a titanium alloy  

Microsoft Academic Search

A glass-ceramic layer containing ?-Ca3(PO4)2 crystals could be joined easily with a new type of titanium alloy (Ti–29Nb–13Ta–4.6Zr) consisting of a ?-titanium phase by heating the metal, on which glass powders with a composition of 60CaO·30P2O5·7Na2O·3TiO2 were placed, at 800°C in air. Measurement of tensile bonding strength revealed that the joining between the coating layer and the substrate is very

Toshihiro Kasuga; Takeshi Mizuno; Mikio Watanabe; Masayuki Nogami; Mitsuo Niinomi

2001-01-01

344

Structural characterization by x-ray methods of novel antimicrobial gallium-doped phosphate-based glasses  

NASA Astrophysics Data System (ADS)

Antimicrobial gallium-doped phosphate-based glasses of general composition (P2O5)0.45(CaO)0.16(Na2O)0.39-x(Ga2O3)x (where x=0, 0.01, 0.03, and 0.05) have been studied using the advanced synchrotron-based techniques of Ga K-edge x-ray absorption spectroscopy and high-energy x-ray diffraction to provide a structural insight into their unique properties. The results show that the Ga3+ ions are octahedrally coordinated. Furthermore, substitution of Na2O by Ga2O3 strengthens the phosphate network structure because the presence of GaO6 octahedra inhibits the migration of the remaining Na+ ions. The results are discussed in terms of the use of Na2O-CaO-P2O5 glasses as controlled-delivery devices for antimicrobial Ga3+ ions in biomedical applications. We are thereby able to relate the atomic-scale environment of the Ga3+ ions beneficially to the glass dissolution, and thus to their ability to disrupt bacterial cell activity by usurping the role of iron.

Pickup, D. M.; Moss, R. M.; Qiu, D.; Newport, R. J.; Valappil, S. P.; Knowles, J. C.; Smith, M. E.

2009-02-01

345

Kaersutite megacrysts in the Permian mafic dikes of the Panticosa pluton (Pyrenees, Spain)  

NASA Astrophysics Data System (ADS)

Several mafic dikes crosscut the Palaeozoic granitic pluton of Panticosa and its Devonian metasedimentary country rocks. The dikes arrange in two swarms: 1) a N-S oriented system with a calc-alkaline affinity and 2) an E-W oriented system with an alkaline affinity; the alkaline dikes sometimes cut the calc-alkaline ones. The alkaline dikes are classified as diabases and lamprophyres. They are mainly composed of micro- to phenocrysts of calcic plagioclase, Ti-rich clinopyroxene, olivine pseudomorphs and opaque minerals, defining doleritic to microporphyritic rock textures. Vesicles are common in these dikes, normally filled by chlorite (± calcite). Megacrysts of brown amphibole have been recognised in some of the alkaline dikes. They are Ti-rich calcic amphiboles classified as kaersutite (Krs). They are up to 8 cm in size (3-4 cm on average), so they are visible to the naked eye. In contrast, the rock groundmass is fine grained (300-400 ?m). This size difference between the megacrysts and the groundmass suggests that the former crystallised below the emplacement level. The Krs megacrysts present markedly anhedral habits, with ellipsoidal, reniform or amoeboid shapes. Their contacts with the groundmass are rounded and sharp and no overgrowth rims have been recognised. These contacts are slightly jagged and show accumulations of opaque minerals. These accumulation zones can reach 400 ?m in thickness, leaving an amphibole relict in the core area. Furthermore, some of the megacrysts are permeated by the rock groundmass. These textural aspects suggest a resorption of the megacrysts due to disequilibrium with the host magma. The composition of the Krs megacrysts has been determined by EMP (major elements) and LA-ICP-MS (trace elements). The megacrysts present very homogeneous compositions: TiO2 (7.5-5.2 wt. %), Al2O3 (13.6-11.8 wt. %), CaO (11.3-10.2 wt. %), Na2O (2.9-0.9 wt. %), K2O (1.3-1 wt. %) and mg# (Mg/(Mg+Fe2++Fe3++Mn) per formula unit, 0.78-0.67). The concentrations in Rare Earth Elements (REE) are considerably high (? REE = 642-938 ppm). They are 45 to 165 times enriched over the primitive mantle; this enrichment is greater for the LREE. Primitive mantle - normalised multielemental diagrams show clear positive anomalies in Nb-Ta and Ba, whilst the main negative anomalies correspond to Rb, Th, U and Pb. The liquid in equilibrium with the Krs megacrysts shows La/LuN values of 4.5-7.8 and a strong negative anomaly in Sr. Furthermore, the relatively high Nb-Ta contents and the low Rb concentration point to HIMU (or EM-1)-type magmas. This signature strongly contrasts, however, with the normalised patterns of the whole rock of the dikes. Thermobarometric calculations suggest a deep origin for the Krs megacrysts: 1105-1032 °C and more than 7 kbar, indicating that they crystallised at a depth of ca. 25 km. According to the petrographic and geochemical results, the Krs megacrysts are not cognate with their host groundmass and should be considered xenocrysts. They crystallised at deep levels and were afterwards incorporated into the ascending magma batch which carried them up to the emplacement level.

Tierz, P.; Lago, M.; Galé, C.; Ubide, T.; Arranz, E.; Larrea, P.; Sanz, T.

2012-04-01

346

Zircon U-Pb ages, Hf-O isotopes and whole-rock Sr-Nd-Pb isotopic geochemistry of granitoids in the Jinshajiang suture zone, SW China: Constraints on petrogenesis and tectonic evolution of the Paleo-Tethys Ocean  

NASA Astrophysics Data System (ADS)

The Jinshajiang suture zone, located in the eastern part of the Tethyan tectonic domain, is noticeable for a large-scale distribution of Late Jurassic to Triassic granitoids. These granitoids were genetically related to the evolution of the Paleo-Tethys Ocean. Beiwu, Linong and Lunong granitoids occur in the middle zone of the Jinshajiang Suture Zone, and possess similar geochemical features, indicating that they share a common magma source. SIMS zircon U-Pb dating reveals that the Beiwu, Linong and Lunong granitic intrusions were emplaced at 233.9 ± 1.4 Ma (2?), 233.1 ± 1.4 Ma (2?) and 231.0 ± 1.6 Ma (2?), respectively. All of these granitoids are enriched in abundances of Si (SiO2t = 65.2-73.5 wt.%), and large-ion lithophile elements (LILEs), but depleted in high field strength elements contents (HFSEs, e.g., Nb, Ta, and Ti). In addition, they have low P2O5 contents (0.06-0.11 wt.%), A/CNK values ([molecular Al2O3/(CaO + Na2O + K2O)], mostly < 1.1) and 10,000 Ga/Al ratios (1.7-2.2), consistent with the characteristics of I-type granites. In terms of isotopic compositions, these granitoids have high initial 87Sr/86Sr ratios (0.7078-0.7148), Pb isotopic compositions [(206Pb/204Pb)t = 18.213-18.598, (207Pb/204Pb)t = 15.637-15.730 and (208Pb/204Pb)t = 38.323-38.791], zircon ?18O values (7.3‰-9.3‰) and negative ?Nd(t) values (- 5.1 to - 6.7), suggesting they were predominantly derived from the continental crust. Their Nb/Ta ratios (average value = 8.6) are consistent with those of the lower continental crust (LCC). However, variable ?Hf(t) values (- 8.6 to + 2.8) and the occurrences of mafic microgranular enclaves (MMEs) suggest that mantle-derived melts and lower crustal magmas were involved in the generation of these granitoids. Moreover, the high Pb isotopic ratios and elevated zircon ?18O values of these rocks indicate a significant contribution of the upper crustal composition. We propose a model in which the Beiwu, Linong and Lunong granitoids were generated under a late collisional or post-collisional setting. It is possible that this collision was completed before Late Triassic. Decompression induced mantle-derived magmas to be underplated and provided the heat for the anatexis of the crust. Hybrid melts including mantle-derived and the lower crustal magmas were then generated. The hybrid melts thereafter ascended to a shallow depth and resulted in some degree of sedimentary rock assimilation. Such three-component mixing magma source and subsequent fractional crystallization could be responsible for the formation of the Beiwu, Linong and Lunong granitoids.

Zhu, Jing-Jing; Hu, Rui-Zhong; Bi, Xian-Wu; Zhong, Hong; Chen, Heng

2011-10-01

347

Behavior of rare earth elements in a paleoweathering profile on granodiorite in the Front Range, Colorado, USA  

NASA Astrophysics Data System (ADS)

A Paleoweathering profile on the Boulder granodiorite in northern Colorado provides an opportunity to trace the behavior of REEs from parent rock, through a weathering profile, into unconformably overlying Permian sediments. With progressive upward weathering of the granodiorite, Na 2 O, CaO, SiO 2 , Ta/Hf, Co/Th, Cr/Sc, Cr/Th, Zr/Hf, La/Sc, Zr/Y, and La/Th decrease; Al 2 O 3 and Fe 2 O 3 T increase; and TiO 2 , MgO, K 2 O, P 2 O 5 , Rb, Zr, Sc, Cr, Co Hf, Nb, Ta, Y, Th, U, REE, Ti/Nb, and Zr/Nb increase to maximum values and then either level off or decrease. LREE enrichment is less in the weathering profile than in the parent granodiorite and although the parent does not have an Eu anomaly (or only a slight positive anomaly), all samples from the weathering profile and overlying sediments have significant negative Eu anomalies. This observation is especially important in that it shows conclusively that a negative Eu anomaly can be produced during chemical weathering of granitoids. We suggest these Eu anomalies are due to relative enrichment of the other REEs and partial loss of Eu during the breakdown of plagioclase. The Boulder weathering profile also has a very minor negative Ce anomaly that is within error of a Ce anomaly in the parent. In the unweathered parent, >50% of the REE are contained in sphene, and in the case of La, also in allanite. From 10-20% of the REE are contained in apatite and biotite (± hornblende), and from 7-10% of the HREEs are in zircon. With exception of Eu, for which feldspars contribute about 8%, negligible amounts of REEs occur in the feldspars. In weathered samples, >75% of the REEs are contained in clay minerals. The crossover between sphene and clay control of REEs occurs over a distance of 1 m near the contact with fresh rock. Except for their small negative Eu anomalies, the clay minerals have REE patterns very similar to those of the parent rock. Isocon plots suggest apparent enrichments of many elements in the Boulder weathering profile result from losses of Na, Ca, and Si during plagioclase weathering. In addition, variable amounts of Sr, Eu, Ta, Nb, P, and Ba were lost during weathering. Although Th/U, Zr/Y, Th/Sc, Zr/Hf, Lu/Hf, and Ti/Zr may have been transferred relatively unchanged from granodiorite parent to the bulk weathering profile, most other element ratios and REE distributions were significantly changed during weathering. This observation implies that caution needs to be exercised when using REE patterns and element ratios to trace sediment provenance. The fact that most element ratios and REE distributions also differ between Fountain sediments and the bulk weathering profile may be related to one or a combination of four factors, listed in order of probable decreasing importance: contribution of other sources to the Fountain sediments, sorting of minerals during sediment deposition, remobilization of elements during diagenesis, and leaching of elements by water flow through the upper meter of the weathering profile.

Condie, Kent C.; Dengate, Jessie; Cullers, Robert L.

1995-01-01

348

Trace element mobilisation in garnet-phengite HP veins along a metabasite-micaschist contact: an example from the Ile de Groix, France  

NASA Astrophysics Data System (ADS)

Whole rock trace element and isotopic compositions of different HP-LT metamorphic rocks of the Ile de Groix, a late Palaeozoic HP terrane, characterize the geochemical processes during subduction and exhumation. Open system fluid-rock interactions during the early stages of subduction (hydrothermal alteration, metasomatism related to sediment-derived fluids) resulted in an increase of ?18O values, as well as K2O, Na2O, MgO, and large ion lithophile element (LILE) content, and a decrease of CaO content of metabasites. During the HP-LT event, fluid-rock interactions were of a closed system nature and most metabasites retained their early-subduction trace element and isotopic compositionsup to lower eclogite-facies P-T conditions. However, rare eclogitic veins are multi-stage veins with a cumulate fluid flow at HP conditions (El Korh et al., 2011). They are phe-grt-ep-rt-ilm-qtz-ab-pg-ap bearing, dominated by garnet and phengite and are hosted in metasomatised eclogite facies metabasites with a grt-agr/jd-barr-gln-rt-ep-qtz-ab-chl-ilm-mt assemblage (peak conditions: ~ 2.0 GPa; 450-550°C) in contact with metapelites. The HREE and HFSE enrichments in garnet and rutile, as well as the LREE enrichment in epidote of the veins, result from a mass transfer from the host metabasite involving an internally-derived fluid during the first stage of vein formation. The fluid was able to mobilise the REE and HFSE on a small scale, but precipitation thereof within the vein minerals. During the second stage of vein formation, the fluid responsible for the formation of phengite, chloritoid, ilmenite and garnet rims contained LILE and REE. Addition of an external fluid is necessary to explain the LILE enrichment. The phengite content in the vein (20-25%) is too high to originate from the host metabasites (only 3-5% phengite), suggesting an input of a pelite-derived fluid from the neighbouring micaschists in addition to the metabasite-derived fluid. The fluid ?18O values of 10.8-12.1‰ (relative to VSMOW) calculated in equilibrium with garnet and phengite from the vein suggest a mix between two sources, but does not allow the internal and external fluid inputs to be quantified as the two sources (host metabasites: 8.9-9.6‰, and near-by metapelites: 11.3-12.1‰) have isotopic values that are close (± 3‰). Eclogitic garnet-phengite veins along metabasite-metapelite contacts support local fluid migration and mass transfer from surrounding source rocks to veins. The vein provides evidence of a small-scale transport of LILE, HREE and HFSE. HREE and HFSE mobility requires intense fluid-rock interaction, and necessitates destabilisation of the prograde HFSE- and HREE-rich minerals (e.g. titanite, garnet) of the vein-hosting rocks.

El Korh, A.; Schmidt, S. Th.; Vennemann, T.; Ulianov, A.

2012-04-01

349

Geochronological and geochemical constraints on the petrogenesis of Middle Paleozoic (Kwangsian) massive granites in the eastern South China Block  

NASA Astrophysics Data System (ADS)

To achieve a better understanding of the Kwangsian orogenic event of the eastern South China Block, this paper documents a set of new zircon U-Pb geochronological and Hf isotopic data and whole-rock elemental and Sr-Nd isotopic analytical results for the representative massive granite intrusions across the Jiangshan-Shaoxing fault. The studied samples are classified into two groups, representing the rocks from the Cathaysia Block to the east of the Jiangshan-Shaoxing Fault (Group 1) and those from the eastern Yangtze Block between the Anhua-Luocheng and Jiangshan-Shaoxing faults (Group 2). The Group 1 samples gave the zircon U-Pb ages of 405-454 Ma and ?Hf(t) values of - 3.6 to - 15.2 with Hf model ages of 1.6-2.4 Ga. Group 2 yielded the zircon U-Pb ages of 400-432 Ma and ?Hf(t) values of - 0.2 to - 12.7 with Hf model ages of 1.3-2.2 Ga. Geochemically, the Group 1 samples (A/CNK = 1.02-1.43) have relatively lower Al2O3, MgO, CaO, P2O5 and ?Nd(t) but higher K2O + Na2O than those of Group 2 (A/CNK = 0.93-1.44). Both groups show similar chondrite-normalized patterns of rare-earth elements with Eu/Eu* values of 0.15-0.92 and strongly negative Ba, Sr, Nb, P and Ti anomalies in primitive mantle-normalized spider diagrams. Their ?Nd(t) values range from - 11.1 to - 8.0 for Group 1, and - 8.9 to - 5.0 for Group 2, generally similar to those of Precambrian paragneiss and contemporaneous gneissoid granites in the eastern South China Block. Our geochronological results indicate that the Kwangsian massive granites in the eastern South China Block were crystallized between 400 Ma and 454 Ma, synchronous to the Kwangsian gneissoid granites along the Wugong and Wuyi-Baiyun-Yunkai domains in the eastern South China Block. The synthesis of these whole-rock geochemical and in-situ zircon Hf isotopic data suggests that both the Group 1 and 2 granites across the Jiangshan-Shaoxing Fault were predominantly derived from a crustal source with some proportional metapelitic and metaigneous components from the Precambrian basement. The input of juvenile mantle-derived magma is insignificant. Taking into account other available evidences, it is proposed that the Jiangshan-Shaoxing Fault might be a pre-existing boundary between the Yangtze and Cathaysia Blocks, which was reactivated during the middle Paleozoic (Kwangsian) orogenic event. The massive granitic magmatism was probably resulted from the doubly crustal thickening and subsequent isostatic readjustment in an intracontinental tectonic regime.

Zhang, Feifei; Wang, Yuejun; Zhang, Aimei; Fan, Weiming; Zhang, Yuzhi; Zi, Jianwei

2012-10-01

350

Stability of basalt+anhydrite+calcite at HP-HT: implications for Venus, the Earth and Mars  

NASA Astrophysics Data System (ADS)

“Canali” observed at Venus’ surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding Venus’ surface temperature. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 - which are alteration products of basalts - melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials may release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earth’s magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by the subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle). Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston-cylinder experiments at 1 GPa between 950 and 1700°C using a mixture of 70wt% tholeiitic basalt + 15wt% anhydrite + 15wt% calcite. Up to ~1440°C, an ultracalcic (CaO>13.5 wt%; CaO/Al2O3>1 wt%) picrobasaltic (SiO2~40-45 wt%; Na2O+K2O<2 wt%) melt containing up to 5 wt% SO3 and up to 5.3 wt% CO2+H2O (calculated by difference) is present in equilibrium with clinopyroxene, anhydrite, spinel-chromite, a CAS-phase and a gas composed mainly of CO and an aliphatic thiol (CH2)4SH. Hydrogen was incorporated either by contact between the starting material and air or by diffusion through the capsule during the experiments. The S content in the gas increases with temperature and run duration, implying that gases with various C/S ratios might be released during an impact or at subduction zones, depending on the P-T-t path and on the H content. Above ~1440°C, a Ca-rich carbonate-sulfate melt forms (in equilibrium with the picrobasaltic melt) which contains a few percents of Na and K. Such melt is not expected to form at Earth’s subduction temperatures. If it forms by meteorite impact, it might crystallize too fast to explain long flows like Venus’ canali. A different basalt/anhydrite/calcite ratio might, however, decrease its formation temperature.

Martin, A. M.; Righter, K.; Treiman, A. H.

2010-12-01

351

Oxygen isotopic and geochemical evidence for a short-lived, high-temperature hydrothermal event in the Chegem caldera, Caucasus Mountains, Russia  

USGS Publications Warehouse

Within the 2.8 Ma Chegem ash-flow caldera (11 ?? 15 km), a single cooling unit of rhyolitic to dacitic welded tuff more than 2 km thick is exposed in deep valleys incised during recent rapid uplift of the Caucasus Mountains. The intracaldera tuff is mineralogically fresh and unaltered, and is overlain by andesite lavas and cut by a resurgent granodiorite intrusion. Major- and trace-element compositions for a 1405-m stratigraphic section of intracaldera tuff display trends of upwardly increasing Na2O, CaO, Al2O3, total Fe, MgO, TiO2, Sr and Zr and decreasing SiO2, K2O and Rb. This mafic-upward zoning (from 76.1 to 69.9% SiO2) reflects an inverted view of the upper part of the source magma chamber. Oxygen isotope studies of 35 samples from this 1405-m section define a striking profile with "normal" igneous ??18O values (+7.0 to +8.5) in the lower 600 m of tuff, much lower ??18O values (-4.0 to +4.3) in a 700-m zone above that and a shift to high ??18O values (+4.4 to -10.9) in the upper 100 m of caldera-fill exposure. Data from two other partial stratigraphic sections indicate that these oxygen isotope systematics are probably a caldera-wide phenomenon. Quartz and feldspar phenocrysts everywhere have "normal" igneous ??18O values of about +8.5 and +7.5, respectively, whereas groundmass and glass ??18O values range from -7.7 to +12.3. Consequently, the ??18O values of coexisting feldspar, groundmass and glass form a steep array in a plot of ??feldspar vs. ??groundmass/glass. Such pronounced disequilibrium between coexisting feldspar and groundmass or glass has never before been observed on this scale. It requires a hydrothermal event involving large amounts of low-18O H2O at sufficiently high temperatures and short enough time (tens of years or less) that glass exchanges thoroughly but feldspar does not. The most likely process responsible for the O depletions at Chegem is a very high temperature (500-600??C), short-lived, vigorous meteoric-hydrothermal event that was focused within the upper 750 m of intracaldera tuff. Mass balance calculations indicate fluid fluxes of = 6 ?? 10-6 mol cm-2 s-1. We believe that the closest historical analogue to this Chegem hydrothermal event is the situation observed in the Valley of Ten Thousand Smokes (Alaska, USA), where hundreds of steam fumaroles with measured temperatures as high as 645??C persisted for 10 to 15 years in the much smaller welded ash-flow tuff sheet (??? 200 m thick) produced by the 1912 Katmai eruption.

Gazis, C.; Taylor, Jr. , H. P.; Hon, K.; Tsvetkov, A.

1996-01-01

352

Alloriite, Na5K1.5Ca(Si6Al6O24)(SO4)(OH)0.5 · H2O, a new mineral species of the cancrinite group  

NASA Astrophysics Data System (ADS)

Alloriite, a new mineral species, has been found in volcanic ejecta at Mt. Cavalluccio (Campagnano municipality, Roma province, Latium region, Italy) together with sanidine, biotite, andradite, and apatite. The mineral is named in honor of Roberto Allori (b. 1933), an amateur mineralogist and prominent mineral collector who carried out extensive and detailed field mineralogical investigations of volcanoes in the Latium region. Alloriite occurs as short prismatic and tabular crystals up to 1.5 × 2 mm in size. The mineral is colorless, transparent, with a white streak and vitreous luster. Alloriite is not fluorescent and brittle; the Mohs’ hardness is 5. The cleavage is imperfect parallel to {10overline 1 0}. The density measured with equilibration in heavy liquids is 2.35g/cm3 and calculated density ( D calc) is 2.358 g/cm3 (on the basis of X-ray single-crystal data) and 2.333 g/cm3 (from X-ray powder data). Alloriite is optically uniaxial, positive, ? = 1.497(2), and ? = 1.499(2). The infrared spectrum is given. The chemical composition (electron microprobe, H2O determined using the Penfield method, CO2, with selective sorption, wt %) is: 13.55 Na2O, 6.67 K2O, 6.23 CaO, 26.45 Al2O3, 34.64 SiO2, 8.92 SO3, 0.37 Cl, 2.1 H2O, 0.7 CO2, 0.08-O = Cl2, where the total is 99.55. The empirical formula ( Z = 1) is Na19.16K6.21Ca4.87(Si25.26Al22.74O96)(SO4)4.88(CO3)0.70Cl0.46(OH)0.76 · 4.73H2O. The simplified formula (taking into account the structural data, Z = 4) is: [Na(H2O)][Na4K1.5(SO4)] · [Ca(OH,Cl)0.5](Si6Al6O24). The crystal structure has been studied ( R = 0.052). Alloriite is trigonal, the space group is P31 c; the unit-cell dimensions are a = 12.892(3), c = 21.340(5) Å, and V = 3071.6(15) Å3. The crystal structure of alloriite is based on the same tetrahedral framework as that of afghanite. In contrast to afghanite containing clusters [Ca-Cl]+ and chains ...Ca-Cl-Ca-Cl..., the new mineral contains clusters [Na-H2O]+ and chains ...Na-H2O-Na-H2O.... The strongest reflections in the X-ray powder diffraction pattern [ d, Å ( I, %)( hkl)] are: 11.3(70)(100), 4.85(90)(104), 3.76(80)(300), 3.68(70)(301), 3.33(100)(214), and 2.694(70)(314, 008). The type material of alloriite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow. The registration number is 3459/1.

Chukanov, N. V.; Rastsvetaeva, R. K.; Pekov, I. V.; Zadov, A. E.

2007-12-01

353

Phosphoinnelite, Ba4Na3Ti3Si4O14(PO4,SO4)2(O,F)3, a new mineral species from peralkaline pegmatite of the Kovdor pluton, Kola Peninsula  

NASA Astrophysics Data System (ADS)

Phosphoinnelite, an analogue of innelite with P > S, has been found in a peralkaline pegmatite vein crosscutting calcite carbonatite at the phlogopite deposit, Kovdor pluton, Kola Peninsula. Cancrinite (partly replaced with thomsonite-Ca), orthoclase, aegirine-augite, pectolite, magnesioarfvedsonite, golyshevite, and fluorapatite are associated minerals. Phosphoinnelite occurs as lath-shaped crystals up to 0.2 × 1 × 6 mm in size, which are combined typically in bunch-, sheaf-, and rosettelike segregations. The color is yellow-brown, with vitreous luster on crystal faces and greasy luster on broken surfaces. The mineral is transparent. The streak is pale yellowish. Phosphoinnelite is brittle, with perfect cleavage parallel to the {010} and good cleavage parallel to the {100}; the fracture is stepped. The Mohs hardness is 4.5 to 5. Density is 3.82 g/cm3 (meas.) and 3.92 g/cm3 (calc.). Phosphoinnelite is biaxial (+), ? = 1.730, ? = 1.745, and ? = 1.764, 2V (meas.) is close to 90°. Optical orientation is Z^c ˜ 5°. Chemical composition determined by electron microprobe is as follows (wt %): 6.06 Na2O, 0.04 K2O, 0.15 CaO, 0.99 SrO, 41.60 BaO, 0.64 MgO, 1.07 MnO, 1.55 Fe2O3, 0.27 Al2O3, 17.83 SiO2, 16.88 TiO2, 0.74 Nb2O5, 5.93 P2O5, 5.29 SO3, 0.14 F, -O=F2 = -0.06, total is 99.12. The empirical formula calculated on the basis of (Si,Al)4O14 is (Ba3.59Sr0.13K0.01)?3.73(Na2.59Mg0.21Ca0.04)?3.04(Ti2.80Fe{0.26/3+}Nb0.07)?3.13[(Si3.93Al0.07)?4O14(P1.11S0.87)?1.98O7.96](O2.975F0.10)?3.075. The simplified formula is Ba4Na3Ti3Si4O14(PO4,SO4)2(O,F)3. The mineral is triclinic, space group P overline 1 or P1. The unit cell dimensions are a = 5.38, b = 7.10, c = 14.76 Å; ? = 99.00°, ? = 94.94°, ? = 90.14°; and V = 555 Å3, Z = 1. The strongest lines of the X-ray powder pattern [ d, Å in ( I)( hkl)] are: 14.5(100)(001), 3.455(40)(103), 3.382(35)(0overline 2 2), 2.921(35)(005), 2.810(40)(1overline 1 4), 2.683(90)(200, overline 2 01), 2.133(80)(overline 2 overline 2 2), 2.059(40)(204, 1overline 3 3, 221), 1.772(30)(0overline 4 1, 1overline 2 7, 2overline 3 2, 2overline 3 3). The infrared spectrum is demonstrated. An admixture of P substituting S has been detected in the innelite samples from the Inagli pluton (South Yakutia, Russia). An innelite-phosphoinnelite series with a variable S/P ratio has been discovered. The type material of phosphoinnelite has been deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Pekov, I. V.; Chukanov, N. V.; Kulikova, I. M.; Belakovsky, D. I.

2007-12-01

354

Remote Raman - Laser Induced Breakdown Spectroscopy (LIBS) Geochemical Investigation under Venus Atmospheric Conditions  

NASA Astrophysics Data System (ADS)

The extreme Venus surface temperatures (~740 K) and atmospheric pressures (~93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. [1] and Sharma et al. [2] demonstrated that both analytical techniques can be integrated into a single instrument capable of planetary missions. The focus of this paper is to explore the capability to probe geologic samples with Raman - LIBS and demonstrate quantitative analysis under Venus surface conditions. Raman and LIBS are highly complementary analytical techniques capable of detecting both the mineralogical and geochemical composition of Venus surface materials. These techniques have the potential to profoundly increase our knowledge of the Venus surface composition, which is currently limited to geochemical data from Soviet Venera and VEGA landers that collectively suggest a surface composition that is primarily tholeiitic basaltic [3] with some potentially more evolved compositions and, in some locations, K-rich trachyandesite. These landers were not equipped to probe the surface mineralogy as can be accomplished with Raman spectroscopy. Based on the observed compositional differences and recognizing the imprecise nature of the existing data, 15 samples were chosen to constitute a Venus-analog suite for this study, including five basalts, two each of andesites, dacites, and sulfates, and single samples of a foidite, trachy-andesite, rhyolite, and basaltic trachyandesite under Venus conditions. LIBS data reduction involved generating a partial least squares (PLS) model with a subset of the rock powder standards to quantitatively determine the major elemental abundance of the remaining samples [4]. PLS analysis suggests that the major element compositions can be determined with root mean square errors ca. 5% (absolute) for SiO2, Al2O3, Fe2O3(total), MgO, and CaO, and ca. 2% or less for TiO2, Cr2O3, MnO, K2O, and Na2O. Finally, the Raman experiments have been conducted under supercritical CO2 involving single-mineral and mixed-mineral samples containing talc, olivine, pyroxenes, feldspars, anhydrite, barite, and siderite. The Raman data have shown that the individual minerals can easily be identified individually or in mixtures. [1] Wiens R.C., et al. (2005) Spect. Acta A 61, 2324; [2] Sharma, S. K. et al. (2007) Spect. Acta A, 68 , 1036 (2007); [3] Barsukov VL (1992) Venusian Igneous Rocks. In Venus Geology, Geochemistry, and Geophysics (eds. VL Barsukov et al.). Univ. Arizona Press, pp. 165-176. [4] Tucker, J.M. et al. (2010) Chem. Geol., in press.

Clegg, S. M.; Barefield, J. E.; Humphries, S.; Wiens, R. C.; Vaniman, D. T.; Sharma, S. K.; Misra, A. K.; Dyar, M. D.; Smrekar, S. E.

2010-12-01

355

Subduction Cycling of C-O-H Volatiles Constrained by Near-Solidus Phase Relations of Water-undersaturated, Carbonated Pelite at 3 GPa  

NASA Astrophysics Data System (ADS)

While the petrology of water release from subducting slab to magmatic arcs is reasonably well-understood, similar cycle of carbon is a poorly understood process. Subducting sediments globally contribute to the geochemical characteristics of arc magmas1, but sedimentary carbonates are predicted to survive shallow dehydration2. Previous experiments on Fe-calcareous clay of Lesser Antilles3 and dry, carbonated pelite composition relevant for Central American trench4 suggested that melting also may not be efficient in releasing CO2 to mantle wedge. To add to the discussion, here we present results from new high pressure experiments on water-undersaturated, CO2-saturated pelitic compositions. Piston cylinder experiments using Au capsules were carried out at 3.0 GPa and 800-1150 °C, using two starting compositions, both containing 5 wt.% CO2 and 1 wt.% H2O, The SiO2 contents of the two bulk compositions were varied (HPLC2: ~60 wt.% and HPLC3: ~51 wt.%) to capture variable loss of silica during shallow dehydration. The subsolidus phase assemblages for both the compositions are identical and at 800 °C comprise cpx + garnet + coesite + Fe-Mg-calcite + phengite + rutile. The solidi are located between 800 and 850 °C and phengite disappears and K-spar appears at 900 °C. Calcitic carbonate disappears at 950-1000 °C for both the compositions. Melts in all the experiments at ?900 °C are fluid-saturated and are rhyolitic in composition. Silicate melt compositions show a decrease in SiO2 and an increase of TiO2, FeO, and CaO with increasing temperature. Al2O3, MgO, Na2O, and K2O in the melt varied little with temperature. The temperatures of solidus, phengite-out, and carbonate breakdown are respectively ~50 °C, ~50 °C, and ~75 °C lower compared to those determined for a calcareous clay3 at similar pressures. Our study suggests that calcitic carbonate and phengite are likely cycled into the deep Earth via relatively cool subduction (<800 °C slab-surface temperature at 3 GPa), whereas dehydration melting of phengite might be encountered for warm subduction zones (800-950 °C at 3 GPa5). Melting of downgoing sediments in warm subduction zones, although is efficient in releasing water to mantle wedge, unlikely strips-off all the carbon as calcitic carbonate remains stable in the residue 100-200 °C above the solidus. Main pulse of slab-CO2 at sub-arc depths may come from sediment diapirs that, owing to lower densities with respect to peridotite, upwell and undergo super-adiabatic melting in the mantle wedge. 1Plank, T. and Langmuir, C. 1993, Nature 362, 739-743. 2Kerrick, D. M. and Connolly, J. A. D. 2001, Nature 411, 293-296. 3Thomsen, T.B. and Schmidt, M.W., EPSL 267, 17-31. 4Tsuno, K. and Dasgupta, D. 2010, Contrib Mineral Petrol doi: 10.1007/s00410-010-0560-9 5Syracuse, E. M., van Keken, P. E. and Abers, G. A. 2010, PEPI doi:10.1016/j.pepi.2010.02.004

Tsuno, K.; Dasgupta, R.

2010-12-01

356

Geochemistry and age of the Essimingor volcano, northern Tanzania (East Africa)  

NASA Astrophysics Data System (ADS)

Essimingor is the oldest of a line of north-south trending pre-rift volcanoes in northern Tanzania associated with the opening of the southern sector of the Gregory Rift, part of the East African Rift system (EAR). Essimingor is centrally located within the present day rift, on the East-West alignment between the large volcanoes of Kilimanjaro and Ngorongoro. Based on K-Ar data of Bagdasaryan et al. (1973), Essimingor is commonly reported to be about 8 Ma, although Evans et al. (1971) reports it to be between 5 to 3 Ma. Geochemically, Essimingor is characterized by alkaline magmatism and it is compositionally similar to adjacent albeit younger volcanoes (e.g. Burko, Tarosero and Monduli). Although the regional trend in magmatic evolution is from basalt to alkaline basalt, and then to more evolved rock types enriched in alkalis (Dawson, 2008), Essimingor appears to be an exception given its age. In fact, this volcano precedes or is, perhaps, contemporaneous with the dominantly basaltic regional magmatism. Essimingor’s age and geochemistry are crucial to providing the earliest record for the tectonomagmatic reconstruction of the EAR in northern Tanzania. To better characterize this pivotal pre-rift volcano we present new 40Ar/39Ar laser-incremental heating and geochemical analyses (major, minor and trace element compositions, and Sr-Nd-Pb isotope data) on twelve carefully chosen lava samples. Laser-incremental heating of whole rock matrix, bulk whole rock and nepheline, yield 40Ar/39Ar ages ranging from 5.81±0.01 Ma to 6.20±0.03 Ma. These ages restrict the duration of volcanism of Essimingor to approximately 370 kyr, and its maximum age to about 6.2 Ma, approximately 2 myr earlier than previously considered. Preliminary geochemical data suggest the presence of large variations in radiogenic isotopes: 87Sr/86Sr ranges from 0.7036 to 0.7056, 143Nd/144Nd from 0.5124 to 0.5126 and 206Pb/204Pb are about 20-21. The isotopic and incompatible trace element variations indicate open system processes and multiple sources, in which one end member is most probably HIMU. The Ce/Pb ratio can be used as a rough evaluation of the crust-magma mixing suggesting the presence of crustal contamination. This contamination is not attributed to simple wall rock assimilation around the magma chamber as there is no correlation between Sr isotopes and Sr concentration. In contrast, major elements are well-behaved with linear compositional variations that reveal magmatic evolution from picrite, to basanite, to nephelinite to tephri-phonolite. The MgO content decreases from 9.40 to 1.12 wt.%, CaO correlates positively with MgO while Al2O3, Na2O and K2O correlate negatively. At about 6 wt.% of MgO, P2O5 and TiO2 no longer behave as incompatible elements but behave as compatible elements. These geochemical trends can be modeled by crystal fractionation during the process of magma evolution in a sub-volcanic chamber. Initially, olivine and pyroxene crystallization drive magmatic evolution, but at MgO values close to 6-5 wt.% a change in slope occurs in several oxide-oxide plots corresponding with the co-precipitation of several other mineral phases (e.g. apatite, Fe-Ti oxides, nepheline).

Mana, S.; Mollel, G. F.; Feigenson, M.; Carr, M. J.; Turrin, B. D.; Furman, T.; Swisher, C. C.

2009-12-01

357

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

358

Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA  

USGS Publications Warehouse

Albitite, locally aegirine- and riebeckite-bearing, formed as a result of sodium metasomatism of felsic dykes and argillites along the Melones Fault Zone near Jamestown, California. Pyrite, magnetite, hematite and titanite are common in small amounts in altered dykes. The dykes were originally plagioclase-hornblende porphyritic, and had major and trace element abundances typical of calc-alkaline rocks, whereas they now have Na2O contents as high as 11.40%. Mass balance calculations indicate that alteration involved addition of large amounts of sodium, and the removal of SiO2 and K2O. Textural preservation, combined with volume factors calculated from specific gravity and whole rock analytical data, indicate that Na-metasomatism was essentially isovolumetric. -from Author

Albino, G. V.

1995-01-01

359

Bioactive glass coatings for orthopedic metallic implants  

SciTech Connect

The objective of this work is to develop bioactive glass coatings for metallic orthopedic implants. A new family of glasses in the SiO2-Na2O-K2O-CaO-MgO-P2O5 system has been synthesized and characterized. The glass properties (thermal expansion, softening and transformation temperatures, density and hardness) are in line with the predictions of established empirical models. The optimized firing conditions to fabricate coatings on Ti-based and Co-Cr alloys have been determined and related to the glass properties and the interfacial reactions. Excellent adhesion to alloys has been achieved through the formation of 100-200 nm thick interfacial layers (Ti5Si3 on Ti-based alloys and CrOx on Co-Cr). Finally, glass coatings, approximately 100 mu m thick, have been fabricated onto commercial Ti alloy-based dental implants.

Lopez-Esteban, Sonia; Saiz, Eduardo; Fujino, Sigheru; Oku, Takeo; Suganuma, Katsuaki; Tomsia, Antoni P.

2003-06-30

360

Geochemical studies of granitic rocks of Kallur area, Manvi Taluk, Raichur district, Karnataka (India).  

PubMed

The geochemical data is much widely used in establishing the overall chemical relation existing between the different rock types with their parentage. A major impetus for this shift comes not only from the need to understand and quantify better the spatial and temporal evolution, with emphasis on the younger greenstone belts (Kallur copper formations), but also from the recognition that such knowledge could form the basis for the sustainable development of our natural resources. In addition, the recurrence of natural hazards has reinforced the need to learn more about the mechanics and to develop predictive modeling with advanced technical tools. This paper is emphasizing on Granodiorites of Kallur area of Manvi Taluk, Raichur District to substantiate the classical approaches of exploration and data gathering through quantitative methods of data processing and interpretation. The trilinear diagram indicates that the granites are rich in Potash and Soda. This clearly indicates that Granites are fairly rich in K2O than Na2O. PMID:22324155

Raghavendra, N R; Reddy, R Purushottam; Nijagunappa, R

2011-01-01

361

Geothermometry applications for the Bal?kesir thermal waters, Turkey  

NASA Astrophysics Data System (ADS)

In this study, reservoir temperatures of Bal?kesir geothermal waters in northwestern Turkey are estimated with various geochemical models. The geothermal fluids in the region are represented by Na-SO4, Na-HCO3 and Ca-HCO3 type waters with discharge temperatures up to 98°C. It was determined that the solubility of silica in most of the waters is controlled by the chalcedony phase. Equilibrium states of the Bal?kesir thermal waters studied by means of Na-K-Mg-Ca diagram, mineral saturation calculations and activity diagrams in the system composed of Na2O-CaO-K2O-Al2O3-SiO2-H2O phases approximate a reservoir temperature of about 120°C. Most of the waters are found to be equilibrated with calcite, chalcedony ± quartz and muscovite at predicted temperature ranges, similar to those calculated from the chemical geothermometers.

Mutlu, Halim; K?l?ç, Ahmet

2009-01-01

362

Bioactive porous scaffolds for tissue engineering applications: investigation on the degradation process by Raman spectroscopy and scanning electron microscopy.  

PubMed

Bioactive glasses in the Na2 O-K2 O-MgO-CaO-B2 O3 -P2 O5 -SiO2 system characterized by an unusually large working range were used for the production of fiber porous scaffolds. In vitro tests were carried out by immersing the scaffolds in simulated body fluid (SBF) solution; soaking time and glass composition effects on the degradation of the material are the principal subject of this investigation. Raman spectroscopy and scanning electron microscopy (SEM) were used as the main investigative methods. The study demonstrates the importance of the network modifiers and, in particular, of the amount of alkaline and al-kaline earths in the different stages of the material degradation and in the development of the hydroxyl-carbonate-apatite (HCA) layer. PMID:20799209

Moimas, L; De Rosa, G; Sergo, V; Schmid, C

363

Gallium-containing phosphosilicate glasses: functionalization and in-vitro bioactivity.  

PubMed

A gallium containing glass 45.7SiO2·24.1Na2O·26.6CaO·2.6P2O5·1.0Ga2O3 (referred to as "Ga1.0") and a parent Ga-free glass 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5 (hereinafter represented as "H"), corresponding to Bioglass® 45S5, were functionalized with Tetraethoxysilane (TEOS) and (3-Aminopropyl)triethoxysilane (APTS) in order to improve their ability to bond with biomolecules, such as drugs, proteins, and peptides. Functionalization with TEOS and APTS promoted the increment in OH groups and formation of NH2 groups on the glass surface, respectively. The presence of OH or NH2 groups was investigated by means of IR spectroscopy and elemental analysis. Moreover, in vitro study of these functionalized glasses was performed in simulated body fluid (SBF) so as to investigate the effect of functionalization on the bioactive behavior of H and Ga1.0. The results showed that the functionalization was obtained along with maintaining their bioactivity. The surfaces of both functionalized glasses were covered by a layer of apatite within 30 days of SBF immersion. In addition, CaCO3 was also identified on the surface of APTS functionalized glasses. However, no gallium release was detected during SBF soaking. PMID:23706200

Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Shruti, Shruti

2013-04-06

364

Geochemistry and petrogenesis of lamproites, late cretaceous age, Woodson County, Kansas, U.S.A.  

USGS Publications Warehouse

Lamproite sills and their associated sedimentary and contact metamorphic rocks from Woodson County, Kansas have been analyzed for major elements, selected trace elements, and strontium isotopic composition. These lamproites, like lamproites elsewhere, are alkalic (molecular K2O + Na2O Al2O3 = 1.6-2.6), are ultrapotassic ( K2O Na2O = 9.6-150), are enriched in incompatible elements (LREE or light rare-earth elements, Ba, Th, Hf, Ta, Sr, Rb), and have moderate to high initial strontium isotopic compositions (0.7042 and 0.7102). The silica-saturated magma (olivine-hypersthene normative) of the Silver City lamproite could have formed by about 2 percent melting of a phlogopite-garnet lherzolite under high H2O CO2 ratios in which the Iherzolite was enriched before melting in the incompatible elements by metasomatism. The Rose Dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain. Significant fractional crystallization of phases that occur as phenocrysts (diopside, olivine, K-richterite, and phlogopite) in the Silver City magma and that concentrate Co, Cr, and Sc are precluded as the magma moved from the source toward the surface due to the high abundances of Co, Cr, and Sc in the magma similar to that predicted by direct melting of the metasomatized Iherzolite. Ba and, to a lesser extent, K and Rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone. The Silver City lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected. ?? 1985.

Cullers, R. L.; Ramakrishnan, S.; Berendsen, P.; Griffin, T.

1985-01-01

365

Vapor pressure and vapor fractionation of silicate melts of tektite composition  

USGS Publications Warehouse

The total vapor pressure of Philippine tektite melts of approximately 70 per cent silica has been determined at temperatures ranging from 1500 to 2100??C. This pressure is 190 ?? 40 mm Hg at 1500??C, 450 ?? 50 mm at 1800??C and 850 ?? 70 mm at 2100?? C. Determinations were made by visually observing the temperature at which bubbles began to form at a constant low ambient pressure. By varying the ambient pressure, a boiling point curve was constructed. This curve differs from the equilibrium vapor pressure curve due to surface tension effects. This difference was evaluated by determining the equilibrium bubble size in the melt and calculating the pressure due to surface tension, assuming the latter to be 380 dyn/cm. The relative volatility from tektite melts of the oxides of Na, K, Fe, Al and Si has been determined as a function of temperature, total pressure arid roughly, of oxygen fugacity. The volatility of SiO2 is decreased and that of Na2O and K2O is increased in an oxygen-poor environment. Preliminary results indicate that volatilization at 2100??C under atmospheric pressure caused little or no change in the percentage Na2O and K2O. The ratio Fe3 Fe2 of the tektite is increased in ambient air at a pressure of 9 ?? 10-4 mm Hg (= 106.5 atm O2, partial pressure) at 2000??C. This suggests that tektites were formed either at lower oxygen pressures or that they are a product of incomplete oxidation of parent material with a still lower ferricferrous ratio. ?? 1964.

Walter, L. S.; Carron, M. K.

1964-01-01

366

Optical absorption and photoluminescence properties of Er3+ doped mixed alkali borate glasses.  

PubMed

An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er2O3 in mixed alkali borate glasses of the type 67.8B2O3 x xLi2O(32-x)Na2O, 67.8B2O3 x xLi2O(32-x)K2O and 67.8B2O3 x xNa2O(32-x)K2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H3BO3, Li2CO3, Na2CO3, K2CO3 and Er2O3 (950-1100 degrees C, 1.5-2 h) between two brass plates. Spectroscopic parameters like Racah (E1, E2 and E3), spin-orbit (xi(4f)) and configuration interaction (alpha) parameters are deduced as function of x. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (omega2, omega4 and omega6) are obtained. Radiative and non-radiative transition rates (A(T) and W(MPR)), radiative lifetimes (tauR), branching ratios (beta) and integrated absorption cross-sections (sigma) have been computed for certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses. PMID:15911407

Ratnakaram, Y C; Kumar, A Vijaya; Naidu, D Tirupathi; Rao, J L

2005-07-01

367

Jurassic-Cretaceous clastic sequences of Chukotka: sedimentation, structural style and geodynamic implications for Russian East Arctic shelf.  

NASA Astrophysics Data System (ADS)

Jurassic-Lower Cretaceous sedimentary sequence, exposed on the Chukotka continental margin is critical for understanding the timing, dynamics and sedimentary setting evolution of Chukotka-Eurasia collisional process (e.g., Sokolov et al., 2002) and so, represents one of the key regional stratigraphic units (Til'man,1973, Tibilov,1982; Miller et al., 2002, 2007). From the other hand, this research may shed the light on the widely discussing problem of the Canadian and Makarov basins opening (e.g., Miller, Verzhbitsky, in press). Jurassic-Lower Cretaceous sedimentary complexes of the Chukotka microcontinent are composed of terrigeneous deposites. Those sedimentary complexes are enriched by organic matter, and fresh clastic materials. Fragments of shales, sometimes laminated or cleaved are their indicator constituents. Sandstones are arkosic. The percentage of types of rocks fragments is different in Jurassic and Cretaceous deposits. Chemical composition of the Jurassic-Cretaceous rocks is not uniform too: Upper Jurassic sandstones form one group depleted in Na2O+K2O, Cretaceous sandstones, enriched in Na2O+K2O. Thus, our investigations indicate that Jurassic-Cretaceous sedimentary basins were related to different source provenance. We believe, that the stratigraphy and composition of Jurassic-Lower Cretaceous onshore sequences are crucial for prediction of the geological structure of East Siberian and Chukchi Sea shelf (1), understanding the evolution of Mesozoic sedimentary basins of East Arctic (2) and testifying the existing geodynamic models of Amerasian Basin opening (3). The work is supported by the Russian Foundation for Basic Research (grant 08-05-00547), program of ONZ RAS 14, and NSH-3172.2008.5.

Tuchkova, M. I.; Sokolov, S. D.; Verzhbitsky, V. E.

2009-04-01

368

Geodynamics of rapid voluminous felsic magmatism through time  

NASA Astrophysics Data System (ADS)

Two end member geodynamic settings produce the observed examples of rapid voluminous felsic (rhyolitic) magmatism through time. The first is driven by mantle plume head arrival underneath a continent and has operated in an identifiable and regular manner since at least 2.45 Ga. This style produces high temperature (? 1100 °C), low aspect ratio rheoignimbrites and lavas that exhibit high SiO2/Al2O3 ratios, high K2O/Na2O ratios, and where available data exists, high Ga/Al2O3 ratios (> 1.5) with high F (in thousands of parts per million) and low water content. F concentration is significant as it depolymerizes the silicate melt, influencing the magmas' physical behavior during development and emplacement. These rhyolites are erupted as part of rapidly emplaced (10-15 Myr) mafic LIPs and are formed primarily by efficient assimilation-fractional crystallization processes from a mafic mantle parent. The second is driven by lithospheric extension during continental rifting or back arc evolution and is exclusive to the Phanerozoic. SLIPs (silicic large igneous provinces) develop over periods < 40 Myr and manifest in elongate zones of magmatism that extend up to 2500 km, contrasting with the mafic LIP style. Some of the voluminous felsic magmas within SLIPs appear to have a very similar geochemistry and petrogenesis to that of the rhyolites within mafic LIPs. Other voluminous felsic magmas within SLIPs are sourced from hydrous lower crust, and contrast with those sourced from the mantle. They exhibit lower temperatures (< 900 °C), explosive ignimbrites with lower SiO2/Al2O3 ratios, and lower K2O/Na2O ratios. Rapid voluminous felsic magmatism represents both extreme examples of continental growth since the Archean, and also dramatic periods of crustal recycling and maturation during the Phanerozoic.

Pankhurst, M. J.; Schaefer, B. F.; Betts, P. G.

2011-04-01

369

Experimental study of partitioning of tantalum, niobium, manganese, and fluorine between aqueous fluoride fluid and granitic and alkaline melts  

NASA Astrophysics Data System (ADS)

This study presents a new set of quantitative experimental data on the partitioning of Ta, Nb, Mn, and F between aqueous F-bearing fluid and water-saturated, Li- and F-rich haplogranite melts with varying alumina/alkali content at T = 650-850 °C and P = 100 MPa. The starting homogeneous glasses were preliminary obtained by melting of three gel mixtures of K2O-Na2O-Al2O3-SiO2 composition with a variable Al2O3/(Na2O+K2O) ratio, ranging from 0.64 (alkaline) and 1.1 (near-normal) to 1.7 (alumina-rich). Ta, Nb, and Mn were originally present in glass only, whereas F was load in both the glass and the solution. The solutionto-glass weight ratio was 1.5-3.0. The compositions of quenched glass were measured by an electronic microprobe, and those of the aqueous solution, with the ICP-MS and ICP-AES methods. The F concentration in the quenched solution was calculated from the mass balance. Under experimental conditions the partition coefficients of Ta, Nb, and Mn between the fluid and the granitic melt (weight ratio fluid C Ta/melt C Ta = fluid/melt D Ta) are shown to be extremely low (0.001-0.008 for Ta, 0.001-0.022 for Nb, and 0.002-0.010 for Mn); thus, these metals partition preferentially into the melt. The coefficients fluid/melt D Ta and fluid/melt D Nb generally increase either with increasing alumina ratio A/NKM in the glass composition, or with rising temperature. The experiments also demonstrated that F preferentially concentrates in the melt; and the partition coefficients of F are below 1, being within the range of 0.1-0.7.

Borodulin, G. P.; Chevychelov, V. Yu.; Zaraysky, G. P.

2009-07-01

370

The distribution and variation of elements in sediments off the Huanghe (Yellow) River mouth  

NASA Astrophysics Data System (ADS)

Surface sediment samples collected off the Huanghe (Yellow) River mouth during the period 2007-2009 were analyzed for major and trace element concentrations. Concentrations of 16 elements were measured using X-ray fluorescence spectrometry. Results demonstrate that sediment grain size is the dominant factor controlling the spatial variations of elemental concentrations. Correlation and cluster analyses allowed classification of the study area into four geochemical regions: Regions I and III are characterized by high concentrations of Al2O3, Fe2O3, MgO, Na2O, K2O, Cr, Cu, Mn, Ni, Pb, V, and Zn, and contain fine-grained sediments with mean grain size ( M z)<22 ?m; and; Regions II and IV contain mostly coarse-grained sediments, and are characterized by high concentrations of SiO2, Na2O, and Zr. The sediment entering the sea from the Huanghe River and its tributaries is enriched in Ca. Thus, the Ca/Al ratio was used as an indicator of the proportion of sediments in the study area that originated from the Huanghe River. Ca/Al ratios decrease from Regions I and II (located in the nearshore zone of the Huanghe River delta) to Regions III and IV (distributed in the offshore zone of the northern Huanghe River delta, southern and southeastern Laizhou Bay area).

Qiao, Shuqing; Shi, Xuefa; Gao, Jingjing; Liu, Yanguang; Yang, Gang; Zhu, Aimei; Wang, Kunshan

2013-07-01

371

29Si NMR study of structural ordering in aluminosilicate geopolymer gels.  

PubMed

A systematic series of aluminosilicate geopolymer gels was synthesized and then analyzed using 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) in combination with Gaussian peak deconvolution to characterize the short-range ordering in terms of T-O-T bonds (where T is Al or Si). The effect of nominal Na2O/(Na2O + K2O) and Si/Al ratios on short-range network ordering was quantified by deconvolution of the 29Si MAS NMR spectra into individual Gaussian peaks representing different Q4(mAl) silicon centers. The deconvolution procedure developed in this work is applicable to other aluminosilicate gel systems. The short-range ordering observed here indicates that Loewenstein's Rule of perfect aluminum avoidance may not apply strictly to geopolymeric gels, although further analyses are required to quantify the degree of aluminum avoidance. Potassium geopolymers appeared to exhibit a more random Si/Al distribution compared to that of mixed-alkali and sodium systems. This work provides a quantitative account of the silicon and aluminum ordering in geopolymers, which is essential for extending our understanding of the mechanical strength, chemical and thermal stability, and fundamental structure of these systems. PMID:15779981

Duxson, Peter; Provis, John L; Lukey, Grant C; Separovic, Frances; van Deventer, Jannie S J

2005-03-29

372

Triassic shoshonites from the dolomites, northern Italy: Alkaline arc rocks in a strike-slip setting  

NASA Astrophysics Data System (ADS)

Triassic igneous rocks of the Dolomites are typical shoshonites, with high K2O/SiO2 and K2O/Na2O ratios, and low Fe contents. They have mid-ocean ridge basalt-like abundances of high field strength elements but are highly enriched in large ion lithophile (LIL) elements (Rb, Sr, Ba, K). The effects of crustal contamination and fractional crystallization have been superimposed on initial LIL element enrichment. Lavas of similar composition occur in Papua New Guinea, Fiji, the Absaroka Mountains, and the Eolian Islands. These suites are all associated with destructive plate margins but were not erupted until after subduction had ceased. Examination of Mediterranean paleogeography indicates that no subduction event which could have given rise to the shoshonites of the Dolomites occurred during the Triassic. In fact, the tectonic setting at the time of eruption of the lavas was probably one of strike-slip faulting. The suite may have inherited its "arc signature" from Permo-Carboniferous subduction of the ocean between Laurasia and Gondawanaland prior to the Hercynian orogeny.

Sloman, L. E.

1989-04-01

373

Influence of oxygen fugacity on the solubility of nitrogen, carbon, and hydrogen in FeO-Na 2 O-SiO 2 Al 2 O 3 melts in equilibrium with metallic iron at 1.5 GPa and 1400°C  

Microsoft Academic Search

It is assumed in the theories of Earth formation that the composition of gases extracted by primary planetary magmas is formed\\u000a by the large-scale melting of the early mantle, which occurred in the presence of a metallic Fe phase. The molten Fe metal\\u000a and silicate materials underwent gravitational migration, which affected the fractionation of siderophile elements. Volatile\\u000a compounds had to

A. A. Kadik; N. A. Kurovskaya; Yu. A. Ignat’ev; N. N. Kononkova; V. V. Koltashev; V. G. Plotnichenko

2011-01-01

374

Geochemical criteria for distinguishing magmatic and metasomatic albite-enrichment in granitoids — examples from the Ta-Li granite Yichun (China) and the Sn-W deposit Tikus (Indonesia)  

NASA Astrophysics Data System (ADS)

Two examples of albite-rich granitoids of different genesis are discussed: the Ta-Li granite at Yichun (China) exhibits dominantly igneous textures, and the sodium-enrichment zone in biotite granite of the Sn-W deposit at Tikus is characterized by metasomatic textures. The Yichun stock shows a magmatic evolution from biotite-muscovite granite to lepidolite granite with an increase of Na2O and F concentrations and a decrease of CaO and Sr concentrations. The composition of the different granite phases is close to pseudoternary minima in the haplogranite-H2O(-Li-F) system. The composition of the F-rich albitization zone at Tikus deviates strongly from the pseudoternary minima and shows a tendency to become monomineralic (nearly pure albitite). CaO and Sr concentrations are increased or remain unchanged with respect to the unaltered biotite granite at Tikus. Albitization produced by fluid-rock interaction in F-rich systems is characterized by that CaO or Sr released by the breakdown of plagioclase in the granite protolith, are fixed in newly formed fluorite or albite, respectively.

Schwartz, M. O.

1992-03-01

375

High-alumina materials of the Al 2 O 3 CaO system  

Microsoft Academic Search

The microstructure of the materials was studied on a MBI-6 microscope, using polished sections, thin sections, and immersion specimens. Specimens prepared from various parts of castings were used to study materials with an inhomogeneous structure. The microanalysis was carried out on polished sections on an MAR-6 microscope at an accelerating voltage of 25 kV and a probe current of 80

V. K. Pavlovskii; E. K. Romanova; A. D. Semenov

1994-01-01

376

Using CaO and MgO-rich industrial waste streams for carbon sequestration  

Microsoft Academic Search

To prevent rapid climate change, it will be necessary to reduce net anthropogenic CO2 emissions drastically. This likely will require imposition of a tax or tradable permit scheme that creates a subsidy for negative emissions. Here, we examine possible niche markets in the cement and steel industries where it is possible to generate a limited supply of negative emissions (carbon

Joshuah K. Stolaroff; Gregory V. Lowry; David W. Keith

2005-01-01

377

STEP cement: Solar Thermal Electrochemical Production of CaO without CO(2) emission.  

PubMed

New molten salt chemistry allows solar thermal energy to drive calcium oxide production without any carbon dioxide emission. This is accomplished in a one pot synthesis, and at lower projected cost than the existing cement industry process, which after power production, is the largest contributor to anthropogenic greenhouse gas emissions. PMID:22540130

Licht, Stuart; Wu, Hongjun; Hettige, Chaminda; Wang, Baohui; Asercion, Joseph; Lau, Jason; Stuart, Jessica

2012-04-26

378

Physical Properties of Calcium Phosphates Glasses with Various Cao\\/P2O5 Mole Ratios  

Microsoft Academic Search

The physical properties of calcium phosphate glasses with various CaO\\/P2O5 mole ratios, Vicker's surface hardness, weight loss percentage after dipping Ringer's solution were investigated in this study. The best surface hardness of crystallized glass has an average hardness of 670Kg\\/mm and the minmum weight loss percentage of crystallized glass were lower than 1%. The major crystalline phase that developed after

Chung-King Hsu; Jinn-Shing Lee; Jie-Ming Sheu; Chin-Wang Huang

1996-01-01

379

Electrical Conductivity of Solid Oxides. Xi. La2O3-CaO System.  

National Technical Information Service (NTIS)

In view of the previously investigated electrical conductivity of a solid solution with the fluorite-type lattice, the subject of this study was to determine the effect of the change of the crystal structure of the electrolyte on electrical conductivity. ...

S. F. Palguev Z. S. Volchenkova

1968-01-01

380

Putting "Organizations" into an Organization Theory Course: A Hybrid CAO Model for Teaching Organization Theory  

ERIC Educational Resources Information Center

|In this article, the authors present a retrospective analysis of an instructor's multiyear redesign of a course on organization theory into what is called a hybrid Classroom-as-Organization model. It is suggested that this new course design served to apprentice students to function in quasi-real organizational structures. The authors further…

Hannah, David R.; Venkatachary, Ranga

2010-01-01