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1

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2O1^H2O  

E-print Network

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2OÃ?1^H2O to 100 MPa: II. Differentiation-component system Na2O^K2O^Al2O3^SiO2^F2OÃ?1^H2O at 100 MPa to character- ize differentiation paths of natural

Long, Bernard

2

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2O1^H2O  

E-print Network

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2O�1^H2O to 100 MPa: I. Silicate-component system Na2O^Al2O3^SiO2^F2O�1 were studied at 0Á1 and 100 MPa to define the location of fluoride and the haplogranite-cryolite binary at greater than 9608C and 0Á1^100 MPa.With increasing Al2O3 in the system

Long, Bernard

3

Effects of Substitution of K2O for Na2O on the Bioactivity of CaO-Na2O-SiO2-P2O5 glasses  

NASA Astrophysics Data System (ADS)

The compositional dependences of bioactivity, thermal properties, atomic structure, and surface morphology have been investigated in the CaO-Na2O-SiO2-P2O5 system; this system is known as a bioglass. 45S5 Bioglass® is known to be a general and highly bioactive material. However, the bioactivity of this glassy material is expected to be improved by modifying the alkali-metal composition. Thermal properties, density, and molar volume were measured to investigate the structural packing. FT-IR spectra and X-ray diffraction were used to confirm the structures of these glasses. The morphology was examined using field emission electron microscopy, and the formation of a Ca-P layer was studied using an energy-dispersive system. This study shows that the tendency to form a calcium phosphate layer is increased with the substitution of K2O for Na2O.

Kim, Taehee; Hwang, Chawon; Gwoo, Donggun; Park, Hoyyul; Ryu, Bong-Ki

2012-10-01

4

Sound Velocity Measurements on K2O-Na2O-Al2O3-SiO2 Liquids and the Compressibility of Crustal Melts  

NASA Astrophysics Data System (ADS)

Longitudinal acoustic velocities of eight liquids in the K2O-Na2O-Al2O3-SiO2 quaternary system have been measured at one bar between 1215 and 1620°C with an ultrasonic frequency-sweep interferometer at centered frequencies that range from 2.8 to 5.5 MHz. These include the first sound speed measurements on K2O- Al2O3-SiO2 liquids, which tend to be relatively viscous and have therefore been poorly represented in the sound speed data set for magmatic liquids. These new velocity measurements were combined with density data from the literature to calculate the adiabatic compressibility for each liquid. These results were converted to isothermal compressibility using available volume, thermal expansion, and heat capacity data in the literature. The final data set permits the compositional and temperature dependence of the liquid compressibility to be obtained through linear regression. The model equation used in the regression is as follows: ?T(liq)=SUM[(XiVi/V)[?i + d?i/dT(T-1673 K)

Liu, Q.; Ai, Y.; Lange, R.

2006-12-01

5

The effect of SiO2/Al2O3 ratio on the structure and microstructure of the glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system  

NASA Astrophysics Data System (ADS)

Ceramic glazes are commonly used to covering of the facing surface of ceramics ware. A well-chosen oxide composition and firing conditions of glazes causes significant improvement of technical parameters of ceramic products. Modern glazes are classified as glass-ceramic composites with different crystalline phases arising during firing. The presence of crystals in the glass matrix is influenced by many factors, especially by oxides molar composition. A crucial role is played by the molar ratio of SiO2/Al2O3. In this work the six composition of glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system were examined. The only variable is the ratio of the silicon oxideto alumina at a constant content of other components: MgO, CaO, K2O, Na2O, ZnO. In order to determine the real phase composition of the obtained glazes research on fluorescence spectrometer (XRF) were done. For structural studies X-ray diffraction (XRD) and spectroscopic in the middle infrared (MIR) were performed. In order to determine the state of the surface (microstructure) research on the scanning electron microscope (SEM) with EDX. The research allowed to determine the influence of SiO2/Al2O3 ratio on the structure and phase composition of glazes and the nature, and type of formed crystalline phases.

Partyka, Janusz; Sitarz, Maciej; Le?niak, Magdalena; Gasek, Katarzyna; Jele?, Piotr

2015-01-01

6

Influences of Al2O3/CaO and Na2O/CaO Ratios on Viscosities of CaO-Al2O3-SiO2-Na2O Melts  

NASA Astrophysics Data System (ADS)

The influences of Al2O3/CaO and Na2O/CaO ratios on viscosities of CaO-Al2O3-SiO2-Na2O melts are investigated by the rotating cylinder method in this study. It is indicated from the experimental results that viscosity first increases and then decreases as gradually increasing Na2O/CaO ratio. As increasing Na2O/CaO ratio while keeping the contents of Al2O3 and SiO2 constant, the transformation of bridging oxygen (from being bonded with Al3+ ion charge compensated by Ca2+ ion to that compensated by Na+ ion, for the higher priority of Na+ ion relative to Ca2+ ion) increases the viscosity, whereas the transformation of non-bridging oxygen decreases the viscosity. These two factors lead to the appearance of viscosity maximum. The viscosity model proposed in our previous papers could well describe the viscosity variation tendency.

Zhen, Yu-Lan; Zhang, Guo-Hua; Tang, Xu-Long; Chou, Kuo-Chih

2014-01-01

7

Enhanced osteocalcin expression by osteoblast-like cells (MC3T3-E1) exposed to bioactive coating glass (SiO 2–CaO–P 2O 5–MgO–K 2O–Na 2O system) ions  

Microsoft Academic Search

This study tested the hypothesis that bioactive coating glass (SiO2–CaO–P2O5–MgO–K2O–Na2O system), used for implant coatings, enhanced the induction of collagen type 1 synthesis and in turn enhanced the expression of downstream markers alkaline phosphatase, Runx2 and osteocalcin during osteoblast differentiation. The ions from experimental bioactive glass (6P53-b) and commercial BioglassTM (45S5) were added to osteoblast-like MC3T3-E1 subclone 4 cultures as

V. G. Varanasi; E. Saiz; P. M. Loomer; B. Ancheta; N. Uritani; S. P. Ho; A. P. Tomsia; S. J. Marshall; G. W. Marshall

2009-01-01

8

First Measurements of Time-Dependent Nucleation as a Function of Composition in Na2O.2CaO.3SiO2 Glasses  

NASA Technical Reports Server (NTRS)

The first measurements in any system of the composition dependence of the time-dependent nucleation rate are presented Nucleation rates of the stoichiometric crystalline phase, Na2O.2CaO.3SiO2, from quenched glasses made with different SiO2 concentrations were determined as a function of temperature and glass composition. A strong compositional dependence of the nucleation rates and a weak dependence for the induction times are observed. Using measured values of the liquidus temperatures and growth velocities as a function of glass composition, these data are shown to be consistent with predictions from the classical theory of nucleation, assuming a composition-dependent interfacial energy.

Kelton, K. F.; Narayan, K. Lakshmi

1996-01-01

9

Na 2O solubility in CaO-MgO-SiO 2 melts  

NASA Astrophysics Data System (ADS)

The sodium solubility in silicate melts in the CaO-MgO-SiO 2 (CMS) system at 1400 °C has been measured by using a closed thermochemical reactor designed to control alkali metal activity. In this reactor, Na (g) evaporation from a Na 2O- xSiO 2 melt imposes an alkali metal vapor pressure in equilibrium with the molten silicate samples. Because of equilibrium conditions in the reactor, the activity of sodium-metal oxide in the molten samples is the same as that of the source, i.e., aNa 2O (sample) = aNa 2O (source). This design also allows to determine the sodium oxide activity coefficient in the samples. Thirty-three different CMS compositions were studied. The results show that the amount of sodium entering from the gas phase (i.e., Na 2O solubility) is strongly sensitive to silica content of the melt and, to a lesser extent, the relative amounts of CaO and MgO. Despite the large range of tested melt compositions (0 < CaO and MgO < 40; 40 < SiO 2 < 100; in wt%), we found that Na 2O solubility is conveniently modeled as a linear function of the optical basicity ( ?) calculated on a Na-free basis melt composition. In our experiments, ?Na 2O (sample) ranges from 7 × 10 -7 to 5 × 10 -6, indicating a strongly non-ideal behavior of Na 2O solubility in the studied CMS melts (?Na 2O (sample) ? 1). In addition to showing the effect of sodium on phase relationships in the CMS system, this Na 2O solubility study brings valuable new constraints on how melt structure controls the solubility of Na in the CMS silicate melts. Our results suggest that Na 2O addition causes depolymerization of the melt by preferential breaking of Si-O-Si bonds of the most polymerized tetrahedral sites, mainly Q 4.

Mathieu, R.; Libourel, G.; Deloule, E.; Tissandier, L.; Rapin, C.; Podor, R.

2011-01-01

10

A new sol–gel process for producing Na 2O-containing bioactive glass ceramics  

Microsoft Academic Search

The sol–gel process of producing SiO2–CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na2O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However,

Qi-Zhi Chen; Yuan Li; Li-Yu Jin; Julian M. W. Quinn; Paul A. Komesaroff

2010-01-01

11

Effects of sodium and potassium ions on a novel SeO2-B2O3-SiO2-P2O5-CaO bioactive system  

NASA Astrophysics Data System (ADS)

The study is focused on Na2O and/or K2O influence on a new sol-gel derived SeO2-B2O3-SiO2-P2O5-CaO bioactive system. The structural changes induced by Na2O and/or K2O addition were correlated with the samples behavior in simulated biological media. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the structure and the type of the chemical bonds. The morphology of the samples was characterized through scanning electron microscopy (SEM). XRD results pointed out a prevalent vitreous structure with an incipient hydroxyapatite (HA) crystalline phase. FTIR results revealed a complex network consisting of silicate, phosphate and borate units, as well as the development of both A- and B-type of carbonate-substituted HA. The bioactivity of the samples was tested in vitro following the evolution of the apatite layers self-assembled on the samples surface in simulated body fluid. Their biocompatibility was investigated after samples surface functionalization with protein. The results indicate that sodium and potassium addition improves the biocompatibility by enhancement of protein adherence on samples surface and without to prevent the samples bioactivity.

Trandafir, D. L.; Ponta, O.; Ciceo-Lucacel, R.; Simon, V.

2015-01-01

12

Structure, dielectric and bioactivity of P2O5-CaO-Na2O-B2O3 bioactive glass  

NASA Astrophysics Data System (ADS)

Bioactive phosphate glasses have been widely investigated for bone repair. Phosphate glass system of 47P2O5-30.5CaO-(22.5-x)Na2O-xB2O3 has been prepared by melt quenching technique. From the Raman analysis, it is confirmed that phosphate network form metaphosphate structure. Bioactivity of the glass is studied by immersing the prepared glass in simulated body fluid (SBF). All the glasses exhibited bioactivity after soaking in SBF. Addition of B2O3 to the glass by replacing the Na2O produces considerable effect on the dielectric and bioactivity of the glass. Ion dynamics are also analyzed through imaginary modulus and imaginary dielectric permittivity.

Maheswaran, A.; Hirankumar, G.; Heller, Nithya; Karthickprabhu, S.; Kawamura, Junichi

2014-06-01

13

Nqrs Data for H4MoNa2O6 [MoNa2O4·2(H2O)] (Subst. No. 2281)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for H4MoNa2O6 [MoNa2O4·2(H2O)] (Subst. No. 2281)

Chihara, H.; Nakamura, N.

14

NQRS Data for MoNa2O4 (Subst. No. 2409)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for MoNa2O4 (Subst. No. 2409)

Chihara, H.; Nakamura, N.

15

Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass  

PubMed Central

The current state-of-the-art in nanotip synthesis relies on techniques that utilize elaborate precursor chemicals, catalysts, or vacuum conditions, and any combination thereof. To realize their ultimate potential, synthesized nanotips require simpler fabrication techniques that allow for control over their final nano-morphology. We present a unique, dry, catalyst-free, and ambient condition method for creating densely clustered, flower-like, sodium oxide (Na2O) nanotips with controllable tip widths. Femtosecond laser ablation of a soda-lime glass substrate at a megahertz repetition rate, with nitrogen flow, was employed to generate nanotips with base and head widths as small as 100 and 20?nm respectively, and lengths as long as 10??m. Control of the nanotip widths was demonstrated via laser dwell time with longer dwell times producing denser clusters of thinner nanotips. Energy dispersive X-ray analysis reveals that nanotip composition is Na2O. A new formation mechanism is proposed, involving an electrostatic effect between ionized nitrogen and polar Na2O. The synthesized nanotips may potentially be used in antibacterial and hydrogen storage applications. PMID:22809176

2012-01-01

16

Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass.  

PubMed

The current state-of-the-art in nanotip synthesis relies on techniques that utilize elaborate precursor chemicals, catalysts, or vacuum conditions, and any combination thereof. To realize their ultimate potential, synthesized nanotips require simpler fabrication techniques that allow for control over their final nano-morphology. We present a unique, dry, catalyst-free, and ambient condition method for creating densely clustered, flower-like, sodium oxide (Na2O) nanotips with controllable tip widths. Femtosecond laser ablation of a soda-lime glass substrate at a megahertz repetition rate, with nitrogen flow, was employed to generate nanotips with base and head widths as small as 100 and 20?nm respectively, and lengths as long as 10??m. Control of the nanotip widths was demonstrated via laser dwell time with longer dwell times producing denser clusters of thinner nanotips. Energy dispersive X-ray analysis reveals that nanotip composition is Na2O. A new formation mechanism is proposed, involving an electrostatic effect between ionized nitrogen and polar Na2O. The synthesized nanotips may potentially be used in antibacterial and hydrogen storage applications. PMID:22809176

Samarasekera, Champika; Tan, Bo; Venkatakrishnan, Krishnan

2012-01-01

17

? Cristobalite stabilization in (Na 2 O+Al 2 O 3 )-added silica  

Microsoft Academic Search

The metastable retention of ?-cristobalite in sintered colloidal gel-derived silica powder with (Na2O + Al2O3) addition has been confirmed by both X-ray diffractometry (XRD) and transmission electron microscopy (TEM). Selected-area\\u000a electron diffraction patterns (SADP) for the chemically stabilized ?-cristobalite revealed diffuse electron scattering intensities (DSIs) along ?111?\\u000a ?(-cristobalite), ?110?\\u000a ?\\u000a , and ?100?\\u000a ?\\u000a , respectively, representing a disordered structure

Chin-Hsiao Chao; Hong-Yang Lu

2002-01-01

18

Heat treatment of Na2O-CaO-P2O5-SiO2 bioactive glasses: densification processes and postsintering bioactivity.  

PubMed

Because of their excellent bioactivity, bioactive glasses are increasingly diffused to produce biomedical devices for bone prostheses, to face the dysfunctions that may be caused by traumatic events, diseases, or even natural aging. However, several processing routes, such as the production of scaffolds or the deposition of coatings, include a thermal treatment to apply or sinter the glass. The exposure to high temperature may induce a devetrification phenomenon, altering the properties and, in particular, the bioactivity of the glass. The present contribution offers an overview of the thermal behavior and properties of two glasses belonging to the Na2O-CaO-P2O5-SiO2 system, to be compared to the standard 45S5 Bioglass(®). The basic goal is to understand the effect of both the original composition and the thermal treatment on the performance of the sintered glasses. The new glasses, the one (BG_Na) with a high content of Na2O, the other (BG_Ca) with a high content of CaO, were fully characterized and sintering tests were performed to define the most interesting firing cycles. The sintered samples, treated at 880°C and 800°C respectively, were investigated from a microstructural point of view and their mechanical properties were compared to those of the bulk (not sintered) glass counterparts. The effect of sintering was especially striking on the BG_Ca material, whose Vickers hardness increased from 598.9 ± 46.7 HV to 1053.4 ± 35.0 HV. The in vitro tests confirmed the ability of the glasses, both in bulk and sintered form, of generating a hydroxyapatite surface layer when immersed in a simulated body fluid. More accurate biological tests performed on the sintered glasses proved the high bioactivity of the CaO-rich composition even after a heat treatment. PMID:22052581

Sola, A; Bellucci, D; Raucci, M G; Zeppetelli, S; Ambrosio, L; Cannillo, V

2012-02-01

19

Thermal and elastic characterization of Sb2O3-Na2O-ZnO glasses  

NASA Astrophysics Data System (ADS)

New glasses were investigated in the ternary system Sb2O3-Na2O-ZnO. The glass transition temperature, Tg, and the onset of the crystallization Tx range from 278 to 304 °C and from 370 to 450 °C, respectively. The thermal stability factor (Tx-Tg) lies between 109 and 155 °C. Ultrasonic velocities were measured by using the pulse echo method to determine the elastic parameters (E, G, K and L) and other related parameters (Poisson's ratio, acoustic impedance and Debye temperature). Other physical properties were also measured, such as density and microhardness. The different measured properties are analyzed in the light of the structural role of ZnO in these glasses.

Hamzaoui, M.; Azri, S.; Soltani, M. T.; Lebullenger, R.; Poulain, M.

2013-11-01

20

Measuring and Modeling Viscosity of CaO-Al2O3-SiO2(-K2O) Melt  

NASA Astrophysics Data System (ADS)

The effect of K2O on viscosity in CaO-SiO2-Al2O3 melt has been measured by a rotating spindle viscometer. It is indicated from the experimental results that viscosity first increases then decreases with the increasing content of K2O; the maximum viscosity occurs in the field of K2O/Al2O3 > 1. After gradually adding K2O, the transformation of bridging oxygen (from being bonded with Al3+ ion charge compensated by Ca2+ ion to that compensated by K+ ion, for the higher priority of K+ ion relative to Ca2+ ion) increases the viscosity, whereas the increase of content of nonbridging oxygen decreases viscosity. The two factors lead to the complicate variation behavior of viscosity. The viscosity model proposed in our previous papers describes this phenomenon well.

Zhang, Guo-Hua; Chou, Kuo-Chih

2012-08-01

21

Compressibility of Na2O-2SiO2 Liquid and Melt to 8 GPa Using Brillouin Scattering  

NASA Astrophysics Data System (ADS)

Brillouin scattering measurements have been carried out on Na2O-2SiO2 glass and liquid under in situ pressures to 8 GPa at temperatures from 300 K to 850 K. For the first time, the "modified" platelet scattering geometry has enabled us to determine VP independently from refractive index, and hence adiabatic compressibility and density of silicate melt as a function of pressure and temperature. In accordance with existing models for densification of silicate glasses and melts, the more compact arrangement of atoms has been assumed to account for the observed increase in density of the melt and glass phases formed at high P-T conditions. A marked change in pressure derivative of adiabatic bulk modulus (dK/dP=K') exists between the liquid (K'= 6.3) and glass (K'= 4.8) forms of Na2O-2SiO2: the notably higher K' of the liquid is consistent with the liquid being able to access a wider range of compressional mechanisms. The large K' of the liquid thus illustrates that the means of compaction of the liquid may differ substantially from that of the glass.

Tkachev, S. N.; Manghnani, M. H.; Williams, Q.; Ming, L.

2003-12-01

22

FT-IR and thermoluminescence investigation of P2O5-BaO-K2O glass system  

NASA Astrophysics Data System (ADS)

The 0.5P2O5?xBaO?(0.5-x)K2O glass system (0?x?0.5mol%) is investigated by FT-IR and thermoluminescence as a possible dosimetic material. FT-IR spectra show structural network modifications with the composition variations of the studied glasses. The predominant absorption bands are characterized by two broad peaks near 500 cm-1, two weak peaks around 740 cm-1 and three peaks in the 900-1270 cm-1 region. The shift in the position of the band assigned to asymmetric stretching of PO2- group, ?as(PO2-) modes from ˜1100 cm-1 to 1085 cm-1 and the decrease in its relative intensity with the increasing of K2O content shows a network modifier role of this oxide.. Luminescence investigations show that by adding modifier oxides in the phosphate glass a dose dependent TL signals result upon irradiation. Thus P2O5-BaO-K2O glass system is a possible candidate material for dosimetry in the dose 0 - 50 Gy range.

Ivascu, C.; Timar-Gabor, A.; Cozar, O.

2013-11-01

23

Kinetics of Na2O and B2O3 Loss From CaO-SiO2-Al2O3 Slags  

NASA Astrophysics Data System (ADS)

The present work was carried out to study the loss of Na2O and B2O3 from CaO-SiO2-Al2O3 slags containing high content of Al2O3 and Na2O in the temperature range of 1573 K to 1773 K (1300 °C to 1500 °C). The rate of loss was determined by monitoring the weight change of the slag melt by thermogravimetric analysis under isothermal conditions. As expected, the evaporation rate was found to increase with increasing the temperature. Higher basicity and larger B2O3 and Na2O concentrations were also found to increase the evaporation rate. The evaporation rate appears to be controlled by chemical reaction at the surface in the beginning, followed by a mixed reaction-mass transfer regime, and finally a liquid-phase mass transport step. The apparent activation energies for the evaporation reaction were calculated for different slag compositions.

Li, Mark; Utigard, Torstein; Barati, Mansoor

2014-08-01

24

Kinetics of Na2O and B2O3 Loss From CaO-SiO2-Al2O3 Slags  

NASA Astrophysics Data System (ADS)

The present work was carried out to study the loss of Na2O and B2O3 from CaO-SiO2-Al2O3 slags containing high content of Al2O3 and Na2O in the temperature range of 1573 K to 1773 K (1300 °C to 1500 °C). The rate of loss was determined by monitoring the weight change of the slag melt by thermogravimetric analysis under isothermal conditions. As expected, the evaporation rate was found to increase with increasing the temperature. Higher basicity and larger B2O3 and Na2O concentrations were also found to increase the evaporation rate. The evaporation rate appears to be controlled by chemical reaction at the surface in the beginning, followed by a mixed reaction-mass transfer regime, and finally a liquid-phase mass transport step. The apparent activation energies for the evaporation reaction were calculated for different slag compositions.

Li, Mark; Utigard, Torstein; Barati, Mansoor

2015-02-01

25

Experimental study of boron solubility and speciation in the Na 2O–B 2O 3–SiO 2–H 2O system  

Microsoft Academic Search

The Na2O–B2O3–SiO2–H2O system has been studied at 520 °C and 1.5 kbar in order to understand boron solubility and speciation under hydrothermal conditions at different sodium content. Within the studied compositional range (excess of SiO2; Na2O – 0–5.8 wt.%; B2O3 – 3.5–6.7 wt.%, and H2O – 50.5–68.2 wt.%) the system contains three phases: aqueous fluid, quartz and borosilicate liquid. At

Sergey Z. Smirnov; Victor G. Thomas; Sergey P. Demin; Valeri A. Drebushchak

2005-01-01

26

A semi-empirical thermodynamic formalism for high-pressure aqueous silicate solutions in the model system K2O-Na2O-CaO-MgO-Al2O3-SiO2-H2O-CO2, a first approach  

NASA Astrophysics Data System (ADS)

The results of experimental solubility determinations in aqueous solutions at high pressures up to 5 GPa are often difficult to gauge with respect to precision and accuracy, because of the potential uncertainties inherent in the available experimental approaches. Existing models of aqueous silicate solutions at low pressures are either unsuitable for extrapolation beyond 0.5 to 1.0 GPa or involve polynomial fits in which the fit parameters lack direct physical meaning. An approach described by Gerya et al. [1,2], based on statistical thermodynamics, allows aqueous silicate solutions to be described as mixtures of fictive oxide "components" together with water molecules in both clustered and "gas-like", i.e. unassociated, states. Burchard et al. [3] presented a first data set for fluids in the system CaO-SiO2-H2O, using the statistical thermodynamic formulation of Gerya et al [1,2] and extending it to include charged fluid species such as Ca2+, Ca(OH)+, Ca(OH)2, OH- and H+. We have now further developed the data set of Burchard et al. [3] by including carbonic fluid species and extending the model system to include MgO and Al2O3. In addition, initial progress has been made in including potassium and sodium model species. Solid phase data were obtained by mathematical conversion of existing thermodynamic mineral data into the semi-empirical form. With this semi-empirical data set calculations for simple, "wet" silicate rocks are now possible. We present applications to suites of jadeitites and jadeite-lawsonite-quartz rocks from the Rio San Juan serpentinite mélanges of the northern Dominican Republic. These rocks have crystallized from high-pressure aqueous fluids in a long-lived intra-oceanic subduction-zone environment at various times and at different P-T conditions (Schertl et al. [4]). The fluid-rock interactions leading to these spectacular rocks are still poorly understood. [1] Gerya et al. (2004) Phys. Chem. Minerals 31, 429-455; [2] Gerya et al. (2005) Eur. J. Mineral. 17, 269-283; [3] Burchard et al. (2011) Eur. J. Mineral. 23, 409-424; Schertl et al. (2012) Eur. J. Mineral. 24, 199-216.

Schertl, H.; Burchard, M.; Hertwig, A.; Maresch, W. V.

2012-12-01

27

Raman Spectroscopic Study of Nd-Doped 10Na(2)O-90TeO(2) Glasses  

SciTech Connect

Tellurite glass systems have important commercial applications in optical communication due to its high refractive index, good infrared transmittance, and high optical nonlinearity. Previously, we studied optical absorption. A local Nd-O structural transition, in the vicinity of 1 mol% Nd2O3, was found; the asymmetry of Nd-O ligand field was at maximum whereas, the degree of Nd-O bond covalency was in a minimum according to the Judd-Ofelt theory derived intensity parameters of the oscillator strength. In this study, we report our investigation on the structural change in the host matrix, 10Na2O-90TeO2, as a function of Nd2O3 concentration using Raman spectroscopy technique. Over the Nd2O3 concentration region from 0.5 to 2.5 mol%, our Raman spectroscopic study showed that the addition of Nd into tellurite glass converts TeO4 trigonal bipyramid (tbp) units to TeO3 trigonal pyramid (tp) units, and possibly some terminal TeO3+1 polyhedra. The Nd effect on the speciation of tellurite structural groups is similar to that of other metal cations of monovalent, divalent, and trivalent. The previously observed Nd-O local structural transition was also found in the current study. A transition, near 1 mol% Nd2O3, was observed in the correlations, both band position and intensity, between two Raman stretching vibration bands near 600 and 730 cm-1. The low frequency band represents the stretching vibration mode of TeO4 tbp units and the high frequency band represnts the stretching vibration mode of TeO3 trigonal pyramid (tp) units. Therefore, the observed transition may suggest the formation of TeO3+1 polyhedron units in the glasses with Nd2O3 concentration greater than 1 mol%. Near 465 cm-1, the bending vibration band for Te-O-Te linkages showed a significant decrease for the glass with 2.5 mol% Nd2O3, suggesting a considerable breakage of the tellurite network.

Li, Hong; Su, Yali; Sundaram, S. K.

2001-11-01

28

Preparation and characterization of sol–gel derived glasses in the ternary Na 2 O–Al 2 O 3 –P 2 O 5 system  

Microsoft Academic Search

A new sol–gel synthesis route to organic free Na2O–Al2O3–P2O5 xerogels was developed. These xerogels contain P2O5 up to 67.5 mole % and Al2O3 up to 20 mole % and could be melted to homogeneous glasses in air at significantly lower temperatures than those applied using the conventionally melting method. Aluminum isopropoxide dissolved in isopropanol, orthophosphoric acid dissolved in isopropanol and

Sherief M. Abo-Naf; N. A. Ghoneim; H. A. EI-Batal

2004-01-01

29

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

2014-04-01

30

Effect of SiO2/Na2O mole ratio on the properties of foam geopolymers fabricated from circulating fluidized bed fly ash  

NASA Astrophysics Data System (ADS)

Geopolymers are three-dimensional aluminosilicates formed in a short time at low temperature by geopolymerization. In this paper, alkali-activated foam geopolymers were fabricated from circulating fluidized bed fly ash (CFA), and the effect of SiO2/Na2O mole ratio (0.91-1.68) on their properties was studied. Geopolymerization products were characterized by mechanical testing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results show that SiO2/Na2O mole ratio plays an important role in the mechanical and morphological characteristics of geopolymers. Foam samples prepared in 28 d with a SiO2/Na2O mole ratio of 1.42 exhibit the greatest compressive strength of 2.52 MPa. Morphological analysis reveals that these foam geopolymers appear the relatively optimized pore structure and distribution, which are beneficial to the structure stability. Moreover, a combination of the Si/Al atomic ratio ranging between 1.47 and 1.94 with the Na/Al atomic ratio of about 1 produces the samples with high strength.

Liu, Ze; Shao, Ning-ning; Huang, Tian-yong; Qin, Jun-feng; Wang, Dong-min; Yang, Yu

2014-06-01

31

Optical properties and glass-forming region of the K2O-Sm2O3-TeO2 glass system  

NASA Astrophysics Data System (ADS)

The optical properties and the glass-forming region of the K2O-Sm2O3-TeO2 glass system are studied. In the K2O-Sm2O3-TeO2 system, only the 5K2O-5Sm2O3-90TeO2 composition gives a transparent glass. The refractive index, n, and the optical band-gap energy, E g , of the 5K2O-5Sm2O3-90TeO2 glass are n = 2.04 ± 0.003 and E g = 3.2 eV, respectively. A single Sm2Te6O15 phase is found to be formed by a two-step thermal treatment process at 370 °C for 5 h and 390 °C for 5 h. This is the first report on the crystallization and the preparation of the K2O-Sm2O3-TeO2 glass system.

Hong, K. S.; Cha, Y. J.; Ha, M. G.; Choi, S.; Kim, J. P.; Lee, B. S.; Jeong, E. D.; Kim, H. G.; Borse, P. H.

2014-11-01

32

NEAR-Solidus Phase Relationships in Metapelites to 1.0 GPa: Influence of K2O Content  

NASA Astrophysics Data System (ADS)

The transition from amphibolite to granulite facies conditions in metasediments at intermediate pressure is still poorly defined and contradictions persist in currently available petrogenetic grids. Phase relationships in metapelites are investigated on four synthetic compositions (M-P-H-L) in the model system K2O-CaO-FeO-MgO-Al2O3-SiO2-H2O. Experiments were carried out in a piston cylinder apparatus at pressures and temperatures up to 1.0 GPa and to 730^o, and in an internally heated pressure vessel at 0.8 GPa at temperatures up to 730^o. In order to monitor the effect of H2O saturation and fluid speciation, three different charges were loaded for each bulk composition, two at fluid saturated conditions and fO2 buffered by graphite, Ni-NiO and hematite-magnetite respectively. Experiments were characterized by XRD, BSE images and EMPA. All assemblages contain quartz and anorthite. Garnet + biotite ± staurolite + muscovite are stable in compositions M and P while orthoamphibole replaces muscovite in compositions H and L, where the K2O content is lower. Orthoamphibole is of gedrite type containing 2.0 a.p.f.u. (23 O) of Al at 650^o and 2.5 a.p.f.u. at 700^o . At 700^o and 1.0 GPa and 680^o and 0.8 GPa cordierite is also present in composition L. Garnet has grossular and pyrope fractions of 0.1 and 0.2 respectively all over the pressure-temperature range. In agreement with phase relations experimentally determined by Poli and Schmidt (2002), our results revealed that the stability field of staurolite + biotite and orthoamphibole + staurolite pairs extend to higher pressures and temperatures if compared with calculated equilibria in analogous systems (Worley and Powell, 1998; Gouwei et al., 1994). At near-solidus conditions a variety of hydrous phases may be directly involved in the production of melt through fluid present or fluid absent melting reactions. X. Gowei, T. M. Will and R. Powell, J. Metamorphic Geol., 12: 99-119, 1994 S. Poli &M. W. Schmidt, Annu. Rev. Earth Planet. Sci. 30:1-29, 2002 Worley &R. Powell, J. Metamorphic Geol., 16: 169-188, 1998

Ferri, F.

2003-04-01

33

Synthesis and optical characteristics of Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics  

NASA Astrophysics Data System (ADS)

We investigate the crystallinity and the optical properties of pure and Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment. We prepare pure and 1 mol% Sm3+-doped 15K2O-15Nb2O5-70TeO2 glasses by using the conventional melt-quenching method. After annealing at 390 °C and 410 °C, respectively, we characterize the crystallinity of the glasses. We examine the chemical bonding states of the ions and the optical properties by taking absorption, excitation, and emission spectra. We show that Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment are excellent red-orange-emitting phosphors under near UV excitation.

Hong, K. S.; Cha, Yu-Jung; Ha, Myoung Gyu; Jeong, Euh Duck; Bae, Jong Seong; Kim, Hyun Gyu; Yang, Ho-Soon

2014-06-01

34

Physical and optical properties of Dy3+: Li2O-K2O-B2O3 glasses  

NASA Astrophysics Data System (ADS)

The luminescence, lasing and sensing properties of rare earth (RE) ions have drawn much interest among researchers. We have focussed on the physical and optical properties of Li2O-K2O-B2O3 (LKB) with different concentrations of dysprosium (Dy3+) ions. The glass samples were prepared using melt quenching method. The physical parameters of the prepared glass were determined. Optical measurements such as XRD, FTIR, absorption and photoluminescence spectra have been carried out. Dy3+: LKB glass showed eight absorption bands with hypersensitive transition located at 1265 nm (6H15/2 ? 6F11/2-6H9/2). Finally, Dy3+: LKB glass exhibited two intense luminescence emission at 481 nm (4F9/2 ? 6H15/2; blue) and 573 nm (4F9/2 ? 6H13/2; yellow) and feeble band at 683 nm (4F9/2 ? 6H11/2; red) with excitation wavelength at 370 nm. The results obtained are prevalent with others studies and also point to its use in solid-state laser, optoelectronic devices and W-LEDs application.

Azizan, S. A.; Hashim, S.; Razak, N. A.; Mhareb, M. H. A.; Alajerami, Y. S. M.; Tamchek, N.

2014-11-01

35

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

NASA Astrophysics Data System (ADS)

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 for the first time to determine VP independently from refractive index and hence the adiabatic compressibility and density of liquids as a function of pressure and temperature. The observed increase in density of the melt and glass phases formed at high-pressure-temperature conditions is likely associated with structural effects. There is a marked change in pressure derivative of adiabatic bulk modulus (K'S = dKS/dP) between the two phases. The large values of K'S of the liquid phase illustrate that the means of compaction of the liquid differ substantially from those of the glass and that the liquid is able to access a wider range of compaction mechanisms. The measured bulk modulus of the aqueous sodium silicate solution is highly temperature-dependent but is much more similar to values of silicate melts than to that of end-member water, particularly at high pressures. Thus water-rich silica-bearing solutions present at depth are likely to be difficult to seismically distinguish from anhydrous silicate melts solely on the basis of their sound velocities. The data on water-bearing compounds allow the pressure dependence of the partial molar volume of water to be assessed to upper mantle depths. These results are in excellent agreement with prior determinations and illustrate the utility of Brillouin experiments coupled with the externally heated diamond anvil cell in determining partial molar properties of liquids at high pressures.

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

2005-07-01

36

A Phase Equilibrium Study of Tungsten-Bronze Type Solid Solution in BaO-SrO-Na2O-Nb2O5 System  

NASA Astrophysics Data System (ADS)

Phase equilibria in the quarternary BaO-SrO-Na2O-Nb2O5 system were investigated with particular interest in the tungsten-bronze type solid solution. Curie point and lattice constants of ceramic specimens depended considerably on the firing condition. Based on a careful examination of such effects, distribution maps were determined under a unified firing condition (1350°C, 10 h). Several crystals were pulled from the melts and their compositions were identified referring to these maps. The knowledge of tie-lines enables us to infer the behavior of liquidus and solidus surfaces for the solid solution and suggests the absence of a quaternary azeotropic point.

Mikami, Noboru; Ikeda, Takuro

1981-10-01

37

Optical and thermal properties of P 2O 5–Na 2O–CaO–Al 2O 3:CoO glasses doped with transition metals  

Microsoft Academic Search

The aim of this paper is to report the optical and thermal properties of V2O5 and CuO doped P2O5–Na2O–CaO–Al2O3:CoO glasses so as to investigate their possible use in solar collection applications. The optical absorption spectra of the glasses at room temperature were in the spectral range of 200–1100nm. The optical band gaps of the glass samples were determined for direct

S. Cetinkaya Colak; E. Aral

2011-01-01

38

High-pressure x-ray diffraction studies of the nanostructured transparent vitroceramic medium K2O-SiO2-Ga2O3  

E-print Network

High-pressure x-ray diffraction studies of the nanostructured transparent vitroceramic medium K2O embedded in an amorphous matrix, in the pressure range from ambient up to 15 GPa. The optically transparent in an amorphous medium. The pressure-driven evolution of x-ray-diffraction patterns indicated a progressive

Kruger, Michael - Department of Physics, University of Missouri

39

A re-assessment of phase equilibria involving two liquids in the system K2O-Al2O3-FeO-SiO2  

NASA Astrophysics Data System (ADS)

In previously published papers the presentation of experimental results involving two liquids has not adequately addressed the quaternary aspects of the phase equilibria. A theoretical examination of the types of quaternary and pseudo-ternary phase diagrams to be expected is prestend here. When applied to much of the previous data, such quaternary diagrams cope with the variation in the K2O?Al2O3 ratio of coexisting liquids, and all the previous data are shown to be in agreement with the existence of the assemblage tridymite-fayalite-two liquids for a limited temperature range along the field boundary between primary tridymite and primary fayalite. The absolute values of temperature in the different investigations are not easily reconciled without appealing to differences in experimental techniques, to differences in oxygen pressure, or to differences in K2O loss during the experiments, as possible explanations of temperature differences greater than reasonable interlaboratory variations.

Biggar, G. M.

1983-06-01

40

Upconversion and fluorescence spectral studies of Er3+/Yb3+-codoped Bi2Q3-GeO2-Ga2Q3-Na2O glasses.  

PubMed

The absorption spectra and upconversion fluorescence spectra of Er3+/Yb3+-codoped natrium-gallium-germanium-bismuth glasses are measured and investigated. The intense green (533 and 549 nm) and red (672 nm) emission bands were simultaneously observed at room temperature. The quadratic dependence of the green and red emission on excitation power indicates that the two-photon absorption processes occur. The influence of Ga2C3 on upconversion intensity is investigated. The intensity of green emissions increases slowly with increasing Ga2O3 content, while the intensity of red emission increases significantly. The possible upconversion mechanisms for these glasses have also been discussed. The maximum phonon energy of the glasses determined based on the infrared (IR) spectral analysis is as low as 740 cm-1. The studies indicate that Bi2O3-GeO2-Ga2O3-Na2O glasses may be potential materials for developing upconversion optical devices. PMID:16843049

Nie, Qiuhua; Jiang, Cheng; Wang, Xunsi; Xu, Tiefeng; Li, Haoquan

2007-02-01

41

Upconversion fluorescence spectroscopy of Er3+/Yb3+-doped heavy metal Bi2O3-Na2O-Nb2O5-GeO2 glass  

NASA Astrophysics Data System (ADS)

Upconversion fluorescence emission of Er3+/Yb3+-doped Bi2O3-Na2O-Nb2O5-GeO2 heavy metal glass samples excited at 1.06 ?m is experimentally investigated. The results reveal the existence of intense emission bands centered around 520, 545, and 655 nm. The germano-niobate based host glass presents high transparency in the region of 400-2700 nm, the capability of incorporating high dopant concentrations, high melting temperature, and large resistance to atmospheric moisture. The observed intensity of the green fluorescence emission, suggested that the niobium based host glass material plays an important role in the efficiency of the upconversion process. Emission lines centered at 425, 483, 503, 608, and 628 nm were also observed.

Oliveira, A. S.; de Araujo, M. T.; Gouveia-Neto, A. S.; Sombra, A. S. B.; Medeiros Neto, J. A.; Aranha, N.

1998-01-01

42

The biocompatibility of silver-containing Na2O.CaO.2SiO2 glass prepared by sol-gel method: in vitro studies.  

PubMed

This study was performed to determine the in vitro biocompatibility of a bioactive, antibacterial silver based gel. A human osteoblast-like cell line (HOS TE85) was used to test cytocompatibility in the presence of eluants and the biological response in direct contact with Na(2)O.CaO.2SiO(2) gel (containing 0.5050 wt % Ag(2)O prepared by a sol-gel process) sterilized by two different methods; autoclave and gamma-irradiation. MTT assay was used for the indirect evaluation of eluant toxicity and alamar Blue was performed to assess the biological response, which included cell viability and proliferation, and the results showed that these materials were cytocompatible. PMID:19802837

Raucci, Maria Grazia; Adesanya, Kehinde; Di Silvio, Lucy; Catauro, Michelina; Ambrosio, Luigi

2010-01-01

43

Photoluminescence characteristics and energy transfer between Bi3+ and Eu3+ in Na2O—CaO—GeO2—SiO2 glass  

NASA Astrophysics Data System (ADS)

We report the photoluminescence (PL) of Eu3+-doped glass with Bi3+ as a sensitizer. The specific glass system with the strong enhancement of the red emission of Eu3+ is obtained by adding a small number of Bi3+ ions instead of increasing the Eu3+ concentration. The emission band of Bi3+ overlaps with the excitation band of Eu3+ and the lifetime decay curves, resulting in a very efficient energy transfer from Bi3+ to Eu3+. The probability of energy transfer is strongly dependent on Bi3+ concentration. In addition, the intensity of 4f–4f transition is much stronger than that of a charge-transfer (CT) band in the excitation spectrum, which indicates that the Na2O—CaO—GeO2-SiO2 glass is a suitable red-emitting phosphor with high stability as a candidate for light-emitting diodes (LEDs).

Li, Qian-Yue; Xu, Xu-Hui; Zhang, Bu-Hao; Wu, Yu-Mei; Qiu, Jian-Bei; Yu, Xue

2014-12-01

44

DataRepository:Section1Samples,Locations,andTypesofAnalyses Sample#Mapunit,geographiclocalityandsequencenumberCoordinates40  

E-print Network

O, MnO, CaO, Na2O, K2O and P2O5) fused glass beads are prepared. Powders are calcined overnight at 1000 beads are prepared from calcined powders using a `pre-fused' flux from Claisse, with composition of 35

Busby, Cathy

45

E-mail addresses: chi@gps.caltech.edu, jgresh@udel.edu, grr@gps.caltech.edu, gulmer@astro.ocis.temple.edu, vicenzi@volcano.si.edu  

E-print Network

rainbow obsidian were studied. The first has layers of numerous trachytically oriented rods (0.2­2 by 10, 12.5 Al2O3, 1.7 FeOTOT, 0.01 MgO, 0.16 CaO, 4.4 Na2O and 4.6 K2O. The second type has trachytically

Ma, Chi

46

Comparative effects of thermal quenching and ballistic collisions in SiO2-B2O3-Na2O glass  

NASA Astrophysics Data System (ADS)

The differences between the effects of irradiation and thermal quenching were studied in SiO2-B2O3-Na2O glass by molecular dynamics. Classical molecular dynamics simulations reproduced quenching rates between 2 × 1012 K/s and instantaneous quenching. Each configuration was then subjected to a series of displacement cascades. An acceleration of the quenching rate and the accumulation of ballistic collisions result in qualitatively similar effects: swelling, increasing disorder, depolymerization of the glassy network, a decrease in the mean coordination number of B atoms. Nevertheless, ballistic processes induce specific effects that are not reproduced by accelerated quenching: an even larger degree of disorder, higher potential energy, greater depolymerization around B sites and different free volume distribution. The memory of the initial quenching rate is largely lost following an accumulation of displacement cascades, and the structure of the irradiated glasses adopts a final configuration weakly dependant on the initial state. This study shows that comparing the structure of the initial glass prepared at different quenching rates with the structure of irradiated glasses makes it possible to discriminate between thermal quenching and ballistic effects.

Delaye, J.-M.; Peuget, S.; Calas, G.; Galoisy, L.

2014-05-01

47

State-selective energy transfer from Er3+ to Eu3+ in Bi2O3-GeO2-Ga2O3-Na2O glasses.  

PubMed

The Eu(3+) ion was introduced into Er(3+) doped Bi(2)O(3)-GeO(2)-Ga(2)O(3)-Na(2)O (BGGN) glasses to improve the 1.5 microm band emission. As a function of Eu(2)O(3) doped content, we observed the increase in non-radiative decay rate of Er(3+) not only (4)I(11/2) energy level but also (4)I(13/2) energy level, while the lifetime of Er(3+):(4)I(11/2) and (4)I(13/2) levels were shortened from 607 to 241 micros and from 3.37 to 1.88 ms, respectively. Accordingly, the upconversion fluorescence (green and red) was quenched. The total quantum efficiency of the Er(3+):(4)I(13/2) increased with the Eu(2)O(3) content increasing up to 0.2 mol% due to the state-selective energy transfer from Er(3+) to Eu(3+). PMID:19010716

Wang, Jun; Zhou, Yaxun; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua

2009-02-01

48

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

49

Computer assisted orthopaedic surgery -- CAOS.  

PubMed

The use of computer navigation in orthopedic surgery allows for real time intraoperative feedback resulting in higher precision of bone cuts, better alignment of implants and extremities, easier fracture reductions, less radiation and better documentation than what is possible in classical orthopaedic procedures. There is no need for direct and repeated visualization of many anatomical landmarks (classical method) in order to have good intraoperative orientation. Navigation technology depicts anatomy and position of "smart tools" on the screen allowing for high surgical precision (smaller number of outliers from desired goal) and with less soft tissue dissection (minimally invasive surgery - MIS). As a result, there are more happy patients with less pain, faster recovery, better functional outcome and well positioned, long lasting implants. In general, navigation cases are longer on the average 10 to 20 minutes, special training is required and equipment is relatively expensive. CAOS applications in knee and hip joint replacement are discussed. PMID:16533171

Kanli?, Enes M; Delarosa, Fabian; Pirela-Cruz, Miguel

2006-02-01

50

Rheology and Structure of Chlorine, Fluorine and Water-Bearing Na2O-CaO-Al2O3-SiO2 Melts  

NASA Astrophysics Data System (ADS)

The effect of chlorine (Cl), fluorine (F) and water (H2O), alone and in combination, on the rheology and structure of synthetic peralkaline Na2O-CaO-Al2O3-SiO2 melts as an analog for highly evolved alkaline melts is investigated. We also investigated a peraluminous counterpart to study how the effect of Cl and F depends on the (Na+Ca)/Al ratio. The volatile-free melts were produced from oxide and carbonate powders at 1 atm and temperatures between 1200 and 1650 °C. Amounts of 0.5 to 1.3 mol% of Cl and 0.5 to 18 mol% F were added as NH4Cl, NH4F, NaCl, NaF, CaCl2 and CaF2. The composition of the samples was analysed by electron microprobe. The melts were hydrated with 0.5 to 4 wt% H2O. For the hydration of the peralkaline melts we used an internally heated pressure vessel at 1200 to 1250 °C and 1.5 to 3 kbar. Because of their high liquidus temperatures, the peraluminous melts were hydrated at 1600 to 1675°C and 5 kbar in a piston cylinder apparatus. Water contents were determined by Karl-Fischer-titration, thermogravimetry and IR-spectroscopy. The viscosities of the dry and hydrous peralkaline and peraluminous melts were measured with micropenetration and parallel plate techniques between 13 log10(Pa s) and 5.5 log10(Pa s). We found that the addition of 1.1 mol% Cl to peralkaline melts increased the viscosity by 0.8 log10(Pa s) while 1.9 mol% F decreased the viscosity by 1.2 log10(Pa s) relative to a viscosity of 12 log10(Pa s) of the halogen-free melt. In peralkaline melts containing equal amounts of both, Cl and F, the viscosity is 0.5 log10(Pa s) lower than the volatile-free melt, independent of the total amount of halogens. The effects of Cl and F seem to buffer each other. If there is twice as much F in the melt as Cl, the viscosity is reduced by 0.7 log10(Pa s). In peraluminous melts containing Cl and F the viscosity decreases with increasing volatile content independent of the ratio between the two volatiles. The addition of H2O decreases the viscosity of the peralkaline halogen-free melt by 3.4 log10(Pa s) at ~0.5 wt% H2O and 9.2 log10(Pa s) at ~4 wt% H2O. In both melts F and Cl seem to have no strong influence on the viscosity lowering effect of H2O. The local glass structure was investigated with 19F and 35Cl MAS NMR. Our data show that the F environment has at least 4 sites in the peralkaline melts, more than in the peraluminous melts, where there are 2 different sites. In the peralkaline melts there is a speciation change of F depending on the total amount of F. Cl is located in "salt-like" mixed Ca and Na environments in the peralkaline and peraluminous melts. As the Ca/(Na+Ca) ratio is ~0.16, Na is more prominent in the mixed sites. However, compared to the peralkaline melts Ca becomes slightly more important in the Cl-environment in the peraluminous melts.

Baasner, A.; Schmidt, B.; Webb, S. L.; Dupree, R.

2012-12-01

51

SiO2-CaO-K2O coatings on alumina and Ti6Al4V substrates for biomedical applications.  

PubMed

Alumina and Ti6Al4V alloys are widely used for orthopedics and dental applications due to their good mechanical properties and biocompatibility. Unfortunately they can not provide a satisfactory osteointegration when implanted. In fact, both alumina and Ti6Al4V are not bioactive and thus they can only guarantee a morphological fixation with the surrounding tissues without a suitable chemical anchorage. Aiming to impart bioactive properties to these materials a coating can be proposed. At this purpose, a bioactive glass belonging to the SiO2-CaO-K2O system was selected and prepared. This glass, named SCK, possess a thermal expansion coefficient matching with the alumina (8.5x 10(- 6)/ degrees C) and Ti6Al4V (9 x 10(- 6)/ degrees C) ones and thus is a good candidate to produce coatings on both of them. Simple and low-cost enameling and glazing techniques were used to realize the coatings. Structural, morphological and compositional characterizations of the coatings were carried out by means of X-ray diffraction, optical and scanning microscopy and compositional analyses. The in vitro properties of the coatings were investigated by soaking them in a simulated body fluid (SBF) in order to study the precipitation, on their surfaces, of a biologically active layer of hydroxylapatite (HAp). PMID:16167116

Vitale-Brovarone, C; Verné, E

2005-09-01

52

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O  

NASA Astrophysics Data System (ADS)

Beginning of melting and subsolidus relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been experimentally investigated at pressures up to 20 kbars. The equilibria discussed involve the phases anorthite, sanidine, zoisite, muscovite, quartz, kyanite, gas, and melt and two invariant points: Point [Ky] with the phases An, Or, Zo, Ms, Qz, Vapor, and Melt; point [Or] with An, Zo, Ms, Ky, Qz, Vapor, and Melt. The invariant point [Ky] at 675° C and 8.7 kbars marks the lowest solidus temperature of the system investigated. At pressures above this point the hydrated phases zoisite and muscovite are liquidus phases and the solidus temperatures increase with increasing pressure. At 20 kbars beginning of melting occurs at 740 °C. The solidus temperatures of the quinary system K2O-CaO-Al2O3-SiO2-H2O are almost 60° C (at 20 kbars) and 170° C (at 2kbars) below those of the limiting quaternary system CaO-Al2O3-SiO2-H2O. The maximum water pressure at which anorthite is stable is lowered from 14 to 8.7 kbars in the presence of sanidine. The stability limits of anorthite+ vapor and anorthite+sanidine+vapor at temperatures below 700° C are almost parallel and do not intersect. In the wide temperature — pressure range at pressures above the reaction An+Or+Vapor = Zo+Ms+Qz and temperatures below the melting curve of Zo+Ms+Ky+Qz+Vapor, the feldspar assemblage anorthite+sanidine is replaced by the hydrated phases zoisite and muscovite plus quartz. CaO-Al2O3-SiO2-H2O. Knowledge of the melting relationships involving the minerals zoisite and muscovite contributes to our understanding of the melting processes occuring in the deeper parts of the crust. Beginning of melting in granites and granodiorites depends on the composition of plagioclase. The solidus temperatures of all granites and granodiorites containing plagioclases of intermediate composition are higher than those of the Ca-free alkali feldspar granite system and below those of the Na-free system discussed in this paper. The investigated system also provides information about the width of the P-T field in which zoisite can be stable together with an Al2SiO5 polymorph plus quartz and in which zoisite plus muscovite and quartz can be formed at the expense of anorthite and potassium feldspar. Addition of sodium will shift the boundaries of these fields to higher pressures (at given temperatures), because the pressure stability of albite is almost 10kbars above that of anorthite. Assemblages with zoisite+muscovite or zoisite+kyanite are often considered to be products of secondary or retrograde reactions. The P-T range in which hydration of granitic compositions may occur in nature is of special interest. The present paper documents the highest temperatures at which this hydration can occur in the earth's crust.

Johannes, Wilhelm

1980-09-01

53

Thermogravimetric investigation of the chemical compatibility of graphite and metal oxides  

Microsoft Academic Search

Methods of thermodynamic analysis and gravimetric measurement are used to study graphite and its mixtures with metal oxides heated to 1000°C under nonisothermal conditions. The chemical compatibility of graphite with Al2O3, CaO, SiO2, MgO, Fe2O3, TiO2, Na2O, and K2O is investigated. It is shown experimentally that under the given conditions the loss of mass (m \\/m) in specimens with these

A. I. Snegirev; B. V. Slobodin

1996-01-01

54

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

55

Approche thermodynamique de la corrosion des refractaires aluminosiliceux par le bain cryolithique : modelisation thermodynamique du systeme quaternaire reciproque AlF3-NaF-SiF 4-Al2O3-Na2O-SiO2  

NASA Astrophysics Data System (ADS)

The main objective of this thesis is the thermodynamic modeling of liquid and solid solutions, the stoichiometric compounds and the gaseous phase of the chemical system which represent the species involved in the corrosion of the refractory lining of the electrolysis cell. This chemical system is the quaternary reciprocal system AlF3-NaF-SiF4-Al 2O3-Na2O-SiO2 with aluminum and carbon. The modeling of the entire reciprocal system has never been realized before and is very challenging due to the nature of the oxyfluoride solution. The thermodynamic modeling is based on Gibbs free energy functions coming from the theory of solutions. The central hypothesis of this project is that, if it is possible to reproduce the strong short-range ordering observed between the ions of the liquid solution, then reasonable results will be obtained for the phase equilibria involved in this chemical system. The thermodynamic model used in this thesis is the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA) which takes into account the short-range ordering between first- and also second-nearest-neighbors, and is the best suited to model the oxyfluoride liquid solution. First, the reciprocal system with the most negative Gibbs free energy change for the exchange reaction between the end-members, NaF-SiF4-Na 2O-SiO2, was modeled, allowing thus the validation of the recent modifications of the MQMQA aimed at improving the modeling of the thermodynamic properties of reciprocal solutions presenting a strong short-range order among first-nearest neighbors as well as second-nearest neighbors. In order to model this system, an estimate of the thermodynamic properties of the hypothetical SiF4 liquid was necessary. The experimental data in the binary systems NaF-SiF4 and Na2O-SiO2 are reproduced within the experimental error limits. In the reciprocal system, a group of data in conflict with all others could not be reproduced. The data considered reliable are well reproduced. A unique set of parameters was used to reproduce all the reciprocal sections and extrapolations outside these sections should be satisfactory. The ternary system Al2O3-Na2O-SiO 2 and the ternary reciprocal system AlF3-NaF-Al2O 3-Na2O have been treated jointly due to the fact that compromises were necessary for the optimization of the system common to the two systems, Al2O3-Na2O, in particular for the ?-alumina solid solution. The numerous experimental data relative to the thermodynamic properties of the stoichiometric or the solid solutions in the ternary system have been taken into account for the modeling of NaAlSiO4 and NaAlSi 3O8. Furthermore, the cation NaAl4+, used in the modeling to reproduce the charge compensation effect (substitution of Si4+ by Al3+ coupled to Na+ in the SiO2-rich region of the ternary oxide system), is present in both of these systems and the properties of the end-members related to it (NaAlF4 and NaAlO2) have been adjusted to reproduce the thermodynamic properties of the liquid phase. The absence or lack of experimental data in specific composition regions, in particular in the Na2O-rich region in the oxide system or in the oxide-rich region of the reciprocal system, makes the optimization of these two systems difficult. The modeling of the quaternary reciprocal system Al, Na, Si // F, O has been performed mainly by taking into account the experimental data available in the isoplethal sections NaF-NaAlSiO4, NaF-NaAlSi3O 8, Na3AlF6-NaAlSiO4 and Na3AlF 6-NaAlSi3O8 and by using the model parameters allowing the adjustment of the thermodynamic properties of the liquid solution in the composition region under consideration. The few available data and the conflict among them, undoubtedly related to the experimental difficulties, make the modeling of the quaternary reciprocal system complex. (Abstract shortened by UMI.).

Lambotte, Guillaume

56

Effect of Fe2O3 concentration on the structure of the SiO2-Na2O-Al2O3-B2O3 glass system.  

PubMed

The structural properties of the glass matrix 40SiO(2)·30Na(2)O·1Al(2)O(3)·(29-x)B(2)O(3)·xFe(2)O(3) (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 Fe(3)O(4) crystal formation for Fe(2)O(3) concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe(2)O(3) concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe(2)O(3) concentration. PMID:21763184

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

2011-10-15

57

Near infrared broadband emission from Bi5+-doped Al2O3-GeO2-X (X=Na2O,BaO,Y2O3) glasses  

NASA Astrophysics Data System (ADS)

The authors report on near infrared broadband emission with a wavelength ranging from O to S telecommunication bands in Bi5+-doped GeO2-Al2O3-Na2O, GeO2-Al2O3-BaO, and GeO2-Al2O3-Y2O3 glasses. The superbroadband character is ascribed to the emission of Bi5+ ions. The differences among the optical characters of the glasses are due to the Bi5+ affected by the introduction of yttrium and barium. As the integration of yttrium and barium into GeO2-Al2O3-Bi2O3 system would offer a preferable environment for the formation of Bi5+, the integration of yttrium and barium leads to the redshift of absorption edges as well as the accentuation of Bi5+ concentration.

Xia, Hai-Ping; Wang, Xue-Jun

2006-07-01

58

Investigating the influence of Na(+) and Sr (2+) on the structure and solubility of SiO 2-TiO 2-CaO-Na 2O/SrO bioactive glass.  

PubMed

This study was conducted to determine the influence that network modifiers, sodium (Na(+)) and strontium (Sr(2+)), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr(2+) containing glasses. Additionally the Sr(2+) (~250 mg/L) containing glasses displayed much lower ion release rates than the Na(+) (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface. PMID:25644099

Li, Y; Placek, L M; Coughlan, A; Laffir, F R; Pradhan, D; Mellott, N P; Wren, A W

2015-02-01

59

Investigating the surface reactivity of SiO2-TiO2-CaO-Na2O/SrO bioceramics as a function of structure and incubation time in simulated body fluid.  

PubMed

This study focuses on evaluating the biocompatibility of a SiO2-TiO2-CaO-Na2O/SrO glass and glass-ceramic series. Glass and ceramic samples were synthesized and characterized using X-ray diffraction. Each material was subject to maturation in simulated body fluid over 1, 7 and 30 days to describe any changes in surface morphology. Calcium phosphate (CaP) deposition was observed predominantly on the Na(+) containing amorphous and crystalline materials, with plate-like morphology. The precipitated surface layer was also observed to crystallize with respect to maturation, which was most evident in the amorphous Na(+) containing glasses, Ly-N and Ly-C. The addition of Sr(2+) greatly reduced the solubility of all samples, with limited CaP precipitation on the amorphous samples and no deposition on the crystalline materials. The morphology of the samples was also different, presenting irregular plate-like structures (Ly-N), needle-like deposits (Ly-C) and globular-like structures (Ly-S). Cell culture analysis presented a significant increase in cell viability with the Na(+) materials, 134%, while the Sr(2+) containing glasses, 60-80% and ceramics, 60-85% presented a general reduction in cell viability, however these reductions were not significant. PMID:24796627

Li, Y; Coughlan, A; Wren, Anthony W

2014-08-01

60

Intense 2.7 µm emission and structural origin in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass.  

PubMed

The 2.7 ?m emission properties in Er3+-doped bismuthate (Bi2O3-GeO2-Ga2O3-Na2O) glass were investigated in the present Letter. An intense 2.7 ?m emission in Er3+-doped bismuthate glass was observed. It is found that Er3+-doped bismuthate glass possesses high spontaneous transition probability A (65.26 s(-1)) and large 2.7 ?m emission cross section ?(em) (9.53×10(-21) cm2) corresponding to the stimulated emission of Er3+:4I11/2?4I13/2 transition. The emission characteristic and energy transfer process upon excitation of a conventional 980 nm laser diode in bismuthate glass were analyzed. Additionally, the structure of bismuthate glass was analyzed by the Raman spectrum. The advantageous spectroscopic characteristics of Er3+ single-doped bismuthate glass together with the prominent thermal property indicate that bismuthate glass might become an attractive host for developing solid-state lasers around 2.7 ?m. PMID:22854489

Guo, Yanyan; Li, Ming; Hu, Lili; Zhang, Junjie

2012-01-15

61

Enhanced 1.53-?m and lowered upconversion luminescence in Er3+-doped Ga2O3-GeO2-Bi2O3-Na2O glass by codoping rare earths  

NASA Astrophysics Data System (ADS)

Spectroscopic properties and energy transfer (ET) in Ga2O3-GeO2-Bi2O3-Na2O (GGBN, glass doped with Er3+ and rare earths (RE3+; RE3+=Ce3+, Tb3+) have been investigated. Intense 1.53-?m emission with the peak emission cross-section achieved to 7.58×10-21 cm2 from Er3+-doped GGBN glass has been obtained upon excitation at 980 nm. Effects of RE3+ (RE3+=Ce3+, Tb3+) codoping on the optical properties of Er3+-doped GGBN glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53 ?m emission intensity and decrease of upconversion (UC) fluorescence with increasing Ce3+ concentration have been observed. The incorporation of Tb3+ into Er3+-doped GGBN glass could significantly decrease the UC emission intensity, but meanwhile decrease the 1.53 ?m emission intensity due to the ET from Er3+:4I13/2 to Tb3+:7F2. The results indicate that the incorporation of Ce3+ into Er3+-doped GGBN glass can effectively improve 1.53-?m and lower UC luminescence, which makes GGBN glass more attractive for use in C-band optical fiber amplifiers.

Shi, D. M.; Zhao, Y. G.; Wang, X. F.

2011-07-01

62

Structural and magnetic properties of SiO2-CaO-Na2O-P2O5 containing BaO-Fe2O3 glass-ceramics  

NASA Astrophysics Data System (ADS)

The incorporation method was employed to produce bioactive glass-ceramics from the BaFe12O19-SiO2-CaO-Na2O-P2O5 glass system. The ferrimagnetic BaFe12O19 was first prepared using a simple mixed oxide method, where the oxide precursors of 45S5 bioglass were initially mixed and then melted to form glass. The devitrification of Na3Ca6(PO4)5 and Fe3O4 was observed in all of the quenched glass samples. The glass samples were then subjected to a heat treatment schedule for further crystallization. It was found that the small traces of BaFe12O19 phases started to crystallize in high BF content samples of 20 and 40 wt%. These samples also exhibited good magnetic properties comparable to that of other magnetic glass-ceramics. The bioactivity of the BF glass-ceramics improved with increasing BF content as was evident by the formation of bone-like apatite layers on the surface of all of the glass-ceramics after soaking in SBF for 14 days. The results support the use of these bioactive glass-ceramics for hyperthermia treatment within the human body.

Leenakul, W.; Kantha, P.; Pisitpipathsin, N.; Rujijanagul, G.; Eitssayeam, S.; Pengpat, K.

2013-01-01

63

Dirio de Notcias -Principal Apago informtico no metro lana caos  

E-print Network

Diário de Notícias - Principal Apagão informático no metro lança caos em Lisboa Autor: Luís Fontes parcial #12;Diário de Notícias - Principal Apagão informático no metro lança caos em Lisboa Autor: Luís reprodução, mesmo que parcial #12;Diário de Notícias - Principal Apagão informático no metro lança caos em

Instituto de Sistemas e Robotica

64

Fluorine speciation as a function of composition in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses: A multinuclear NMR study  

NASA Astrophysics Data System (ADS)

The incorporation mechanisms of fluorine (F) into peralkaline and peraluminous Na2O-CaO aluminosilicate glasses with ˜65 mol% SiO2 (model system for phonolites) were investigated by magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. In 19F MAS NMR spectra of the fluorine-bearing peralkaline glasses at least five F sites could be distinguished, while only three of these sites could be found in the corresponding peraluminous glasses, which shows that there are more F incorporation mechanisms in peralkaline than in peraluminous glasses. In the peralkaline glasses containing up to 6.2 mol% F the following F environments were identified: F-Ca(n) at ˜-113 ppm, Si-F-Na(n) or Al-F-Ca(n) at ˜-146 ppm, Al-F-Al at ˜-168 ppm, Al-F-Na(n) at ˜-188 ppm and F-Na(n) at ˜-225 ppm ("n" indicates that the number of atoms is variable or uncertain). F-Ca(n) is the most abundant site which is surprising as Ca is the least common cation in the glasses. The fraction of F-Ca(n) sites increases from 42% to 53% as the F content increases from 1.2 to 6.2 mol%. The addition of up to 16.5 mol% (5.3 wt%) water strongly affects F speciation in peralkaline glasses and results in a decrease in the fraction of F-Al sites compared to F-Ca(n) sites. It seems that hydroxyl groups (OH) and F occupy similar Al environments and that F cannot compete with OH.

Baasner, A.; Schmidt, B. C.; Dupree, R.; Webb, S. L.

2014-05-01

65

Antimicrobial Principles of Xian he cao (Agrimonia pilosa).  

PubMed

From the antimicrobially active extract of the Chinese crude drug, Xian he cao ( AGRIMONIA PILOSA Ledb.), four active compounds were isolated. They were all phloroglucinol derivatives and their structures were elucidated on the basis of spectroscopic data. PMID:17262333

Yamaki, M; Kashihara, M; Ishiguro, K; Takagi, S

1989-04-01

66

The 1.53 ?m spectroscopic properties and thermal stability in Er3+/Ce3+ codoped TeO2-WO3-Na2O-Nb2O5 glasses  

NASA Astrophysics Data System (ADS)

Er3+/Ce3+ codoped tellurite-based glasses with composition of TeO2-WO3-Na2O-Nb2O5 were prepared by high-temperature melt-quenching technique and a detailed study of the 1.53 ?m band spectroscopic properties and thermal stability was presented in this paper. The absorption spectra, visible upconversion spectra, 1.53 ?m band fluorescence spectra, fluorescence lifetimes, Raman spectra, differential scanning calorimeter (DSC) and X-ray diffraction (XRD) curves of glass samples were measured and investigated, together with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated emission and absorption cross-sections, amplification quality factors, energy transfer rates and quantum transition efficiencies. It was found that the prepared glass samples have good thermal stability (Tg>425 °C), large Judd-Ofelt intensity parameter (?6>0.80×10-20 cm2) and bandwidth quality factor (?ep×FWHM>360×10-21 cm2 nm) of Er3+. With the increasing of Ce3+ doped concentration, the visible upconversion emission decreased while the 1.53 ?m band fluorescence intensity improved significantly due to the enhanced energy transfer of Er3+:4I11/2+Ce3+:2F5/2?Er3+:4I13/2+Ce3+:2F7/2 owing to the moderate phonon energy (˜930 cm-1) of glass host, which was beneficial in compensating for the existing energy mismatch between the Er3+:4I11/2?4I13/2 emission and Ce3+:2F5/2?2F7/2 absorption transitions. Compared with the Er3+ single-doped case, the 1.53 ?m band fluorescence intensity in Er3+/Ce3+ codoped glass sample could increase by about 30%. The results indicate that the prepared tellurite-based glass with a suitable Er3+/Ce3+ codoping concentration is an excellent gain medium applied for broadband EDFA pumped with a 980 nm laser diode.

Zheng, Shichao; Zhou, Yaxun; Yin, Dandan; Xu, Xingchen; Qi, Yawei; Peng, Shengxi

2013-05-01

67

Solution behavior of reduced N-H-O volatiles in FeO-Na2O-SiO2-Al2O3 melt equilibrated with molten Fe alloy at high pressure and temperature  

NASA Astrophysics Data System (ADS)

Solubility and speciation of NOH volatiles in a model silicate melt (FeO-Na2O-Al2O3-SiO2) equilibrated with molten Fe alloy have been examined via nitrogen and hydrogen analyses and vibrational spectroscopy (Raman and FTIR). Experiments were performed in an anvil-with-hole apparatus conducted at 4 GPa, 1550 °C, and oxygen fugacity (fO2) from 2.1 to 3.3 log units below IW buffer. The technique of hydrogen fugacity (fH2) buffering via the dissociation of H2O employed here relies upon the diffusion of H2 through Pt to achieve equal chemical potentials of H2 in the Pt capsule and outer assemblage elements. The nitrogen source was Si3N4. The fO2 imposed on the charge was controlled by redox reactions between H2 buffered externally, Si3N4 and components of the Fe-bearing melt that was reduced with O2 liberation and metallic Fe formation. The initial Si3N4 was unstable under the experimental conditions and completely consumed according to the reaction of oxidation: Si3N4 (initial) + 3O2 ? 3SiO2 (melt) + 2N2 (melt) with a subsequent participation of nitrogen in the reactions with H2, the components of silicate and metallic melts. The nitrogen and hydrogen solubility, calculated as N and H, ranges from 0.4 to 1.9 wt.% and from 0.2 to 0.3 wt.%, accordingly. The nitrogen content in iron globules at ?log fO2(IW) = -3.3 was measured as 4.4 wt.%. Characterization by Raman and IR spectroscopy indicates that at fO2, where a metallic Fe phase is stable, the silicate melt would contain species with N-H bonds (NH3, NH4+, NH2-, NH2+) as well as N2, oxidized H species (OH- and H2O) and H2. Experimental studies have shown that the fO2 evolution during metal segregation would have strongly influenced the nature of nitrogen and hydrogen species in reduced magmas of the early Earth.

Kadik, Arnold A.; Litvin, Yuri A.; Koltashev, Vasily V.; Kryukova, Elena B.; Plotnichenko, Victor G.; Tsekhonya, Tatiana I.; Kononkova, Nataliya N.

2013-01-01

68

Hardness properties and microscopic investigation of crack- crystal interaction in SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramic system.  

PubMed

In view of the potential engineering applications requiring machinability and wear resistance, the present work focuses to evaluate hardness property and to understand the damage behavior of some selected glass-ceramics having different crystal morphologies with SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F composition, using static micro-indentation tests as well as dynamic scratch tests, respectively. Vickers hardness of up to 5.5 GPa has been measured in glass-ceramics containing plate like mica crystals. Scratch tests at a high load of 50 Nin artificial saliva were carried out in order to simulate the crack-microstructure interaction during real-time abrasion wear and machining operation. The experimental observations indicate that the novel "spherulitic-dendritic shaped "crystals, similar to the plate like crystals, have the potential to hinder the scratching induced crack propagation. In particular, such potential of the 'spherulitic-dendritic' crystals become more effective due to the larger interfacial area with the glass matrix as well as the dendritic structure of each mica plate, which helps in crack deflection and crack blunting, to a larger extent.While modest damage tolerant behavior is observed in case of 'spherulitic-dendritic' crystal containing material, severe brittle fracture of plate like crystals were noted, when both were scratched at 50 N load. PMID:19730992

Roy, Shibayan; Basu, Bikramjit

2010-01-01

69

On the development of two characteristically different crystal morphology in SiO(2)-MgO-Al (2)O (3)-K (2)O-B (2)O (3)-F glass-ceramic system.  

PubMed

The present work demonstrates how crystals with two different characteristic morphologies can be formed in SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass-ceramic system by adopting two sets of heat treatment experiments. In our study, single stage heat treatment experiments were performed at 1,000 degrees C for varying holding time of 8-24 h with 4 h time interval and as a function of temperature in the range of 1,000-1,120 degrees C with 40 degrees C temperature interval. The constant heating rate of 10 degrees C/min was employed for both sets of experiments. The microstructural changes were investigated using Fourier transformed infrared spectroscopy (FT-IR), SEM-EDS and XRD. For temperature variation batches, the microstructure is characterized by interlocked, randomly oriented mica plates ('house-of-cards' morphology). An important and new observation of complex crystal morphology is made in the samples heat treated at 1,000 degrees C for varying holding times. Such morphology appears to be the results of composite spherulitic-dendritic like growth of mica rods radiating from a central nucleus. The possible mechanism for such characteristic crystal growth morphology is discussed with reference to a nucleation-growth kinetics based model. The activation energy for crystal nucleation and Avrami index are computed to be 388 kJ/mol and 1.3 respectively, assuming Johnson-Mehl-Avrami model of crystallization. Another important result is that a maximum of around 70% of spherulitic-dendritic like crystal morphology can be obtained after heat treatment at 1,000 degrees C for 24 h, while a lower amount (approximately 58%) of interlocked plate like mica crystals is formed after heat treatment at 1,040 degrees C for 4 h. PMID:18704659

Roy, Shibayan; Basu, Bikramjit

2009-01-01

70

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...

71

Metrology from Vertical Objects Xiaochun Cao and Hassan Foroosh  

E-print Network

Metrology from Vertical Objects Xiaochun Cao and Hassan Foroosh School of Computer Science-parallel lines. 1 Introduction Metrology from uncalibrated images is becoming of increasing interest for many, Criminisi et al. [3] proposed an approach for single view metrology, and showed that affine scene structure

Foroosh, Hassan

72

Pool-Frenkel effect and high frequency dielectric constant determination of semiconducting P 2 O 5 Li 2 MoO 4 Li 2 O and P 2 O 5 Na 2 MoO 4 Na 2 O bulk glasses  

Microsoft Academic Search

The ternary 70P2O5-10Li2MoO4-20Li2O and 70P2O5-10Na2MoO4-20Na2O glasses, prepared by the press-melt quenching technique, were studied at temperatures between 298 and 418 K for their high\\u000a dc electric field properties. For the above purpose, the effect of a strong electric field on the dc conduction of these amorphous\\u000a bulk samples was investigated using the gap-type electrode configuration. At low electric fields, the

Dariush Souri; Mohammad Elahi; Mohammad S. Yazdanpanah

2008-01-01

73

Effect of Al 2 O 3 concentration on zirconolite (Ca(Zr,Hf)Ti 2 O 7 ) crystallization in (TiO 2 ,ZrO 2 ,HfO 2 )-rich SiO 2 –Al 2 O 3 –CaO–Na 2 O glasses  

Microsoft Academic Search

Glass-ceramic matrices containing zirconolite (nominally Ca(Zr,Hf)Ti2O7) crystals in their bulk that would incorporate high proportions of minor actinides (Np, Am, Cm) or plutonium could be envisaged\\u000a for their immobilization. Zirconolite-based glass-ceramics can be prepared by controlled crystallization of zirconolite in\\u000a glasses belonging to SiO2–Al2O3–CaO–Na2O–TiO2–ZrO2–HfO2 system. In this study, neodymium was used as trivalent actinides surrogate. Increasing Al2O3 concentration in glass

Daniel Caurant; Pascal Loiseau; Isabelle Bardez; Christel Gervais

2007-01-01

74

Behavior of rare earth elements in a paleoweathering profile on granodiorite in the Front Range, Colorado, USA  

Microsoft Academic Search

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, Na2O, CaO, SiO2, TaHf, CoTh, CrSc, CrTh, ZrHf, LaSc, ZrY, and LaTh decrease; Al2O3 and Fe2O3T increase; and TiO2, MgO, K2O, P2O5,

Kent C. Condie; Jessie Dengate; Robert L. Cullers

1995-01-01

75

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study  

Microsoft Academic Search

Contents of total and extractable heavy metals, carbonates, MnO and Fe2O3, organic matter, and matrix components such as SiO2, Al2O3, CaO, Na2O, MgO, TiO2, K2O and P2O5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were

A. V. Filgueiras; I. Lavilla; C. Bendicho

2004-01-01

76

Computer-Assisted Orthopedic Surgery (CAOS): Pros and Cons  

Microsoft Academic Search

\\u000a Computer-assisted orthopedic surgery (CAOS) has recently evolved as an important technical application that has offered substantial\\u000a improvements over conventional instrumented methods. The possibility of using computers in total joint replacement surgery\\u000a is not a recent discovery, as Bargar and Paul introduced the first successful robotic application for total hips in 1987.1 Their system was a development effort with IBM, which

James B. Stiehl

77

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...

78

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...

79

Kinetic Study on Desulfurization of Hot Metal Using CaO and CaC2  

NASA Astrophysics Data System (ADS)

The kinetics and reaction mechanisms of hot metal desulfurization using CaO and CaC2 were studied in a well-controlled atmosphere with a lab scale high temperature furnace. The growths of CaS around CaO and CaC2 were measured and compared at 1773 K (1500 °C). The parabolic rate constant was evaluated to be 5 × 10-7 (cm s-1) on CaO particles, and 2.4 × 10-7 (cm s-1) on CaC2. The bigger parabolic constant of CaO resulted in more efficient desulfurization. Agglomerates and big CaO particles led to 2CaO·SiO2 formation which hindered further utilization of CaO for desulfurization. The 2CaO·SiO2 formation was favoured by a high oxygen potential. Since the desulfurization reaction of CaO not only produced CaS but also oxygen, the local oxygen concentration around big CaO particles was higher than around small particles.

Lindström, David; Sichen, Du

2015-02-01

80

Vladykinite, Na3Sr4(Fe2+ )Si8O24: A new complex sheet silicate from peralkaline rocks of  

E-print Network

syenite in the north-central part of the Murun complex in eastern Siberia, Russia (Lat. 58° 22 48 N; LongRoduCtion Potassic peralkaline syenites [wt% K2O > wt% Na2O; mol% Na2O+K2O > mol% Al2O3] are an uncommon type

Chakhmouradian, Anton

81

Effect of H2O on the morphological changes of KNO3 formed on K2O/Al2O3 NOx storage materials: Fourier transform infra-red (FTIR) and time-resolved x-ray diffraction (TR-XRD) studies  

SciTech Connect

Based on combined FTIR and XRD studies, we report here that H2O induces a morphological change of KNO3 species formed on model K2O/Al2O3 NOx storage-reduction catalysts. Specifically as evidenced by FTIR, the contact of H2O with NO2 pre-adsorbed on K2O/Al2O3 promotes the transformation from bidentate (surface-like) KNO3 species to ionic (bulk-like) ones irrespective of K loadings. Once H2O is removed from the sample, a reversible transformation into bidentate KNO3 is observed, demonstrating a significant dependence of H2O on such morphological changes. TR-XRD results show the formation of two different types of bulk KNO3 phases (orthorhomobic and rhombohedral) in an as-impregnated sample. Once H2O begins to desorb above 400 K, the former is transformed into the latter, resulting in the existence of only the rhombohedral KNO3 phase. On the basis of consistent FTIR and TR-XRD results, we propose a model for the morphological changes of KNO3 species with respect to NO2 adsorption/desorption, H2O and/or heat treatments. Compared with the BaO/Al2O3 system, K2O/Al2O3 shows some similarities with respect to the formation of bulk nitrates upon H2O contact. However, there are significant differences that originate from the lower melting temperature of KNO3 relative to Ba(NO3)2.

Kim, Do Heui; Mudiyanselage, Kumudu K.; Szanyi, Janos; Hanson, Jonathan C.; Peden, Charles HF

2014-02-27

82

Electronic Energy Transfer on CaO Surfaces  

SciTech Connect

We excite low-coordinated surface sites of nanostructured CaO samples using tunable UV laser pulses and observe hyperthermal O-atom emission indicative of an electronic excited-state desorption mechanism. The O-atom yield increases dramatically with photon energy, between 3.75 and 5.4 eV, below the bulk absorption threshold. The peak of the kinetic energy distribution does not increase with photon energy in the range 3.9 to 5.15 eV. These results are analyzed in the context of a laser desorption model developed previously for nanostructured MgO samples. The data are consistent with desorption induced by exciton localization at corner-hole trapped surface sites following either direct corner excitation or diffusion and localization of excitons from higher coordinated surface sites.

Joly, Alan G.; Beck, Kenneth M.; Hess, Wayne P.

2008-09-28

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

Strain effects in low-dimensional transition metal oxides Jinbo Cao a,b,  

E-print Network

Strain effects in low-dimensional transition metal oxides Jinbo Cao a,b, *, Junqiao Wu a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 1.1. Spin­lattice­charge coupling in transition metal oxides

Wu, Junqiao

85

Nonisothermal Thermogravimetric Analysis of Thai Lignite with High CaO Content  

PubMed Central

Thermal behaviors and combustion kinetics of Thai lignite with different SO3-free CaO contents were investigated. Nonisothermal thermogravimetric method was carried out under oxygen environment at heating rates of 10, 30, and 50°C min?1 from ambient up to 1300°C. Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods were adopted to estimate the apparent activation energy (E) for the thermal decomposition of these coals. Different thermal degradation behaviors were observed in lignites with low (14%) and high (42%) CaO content. Activation energy of the lignite combustion was found to vary with the conversion fraction. In comparison with the KAS method, higher E values were obtained by the FWO method for all conversions considered. High CaO lignite was observed to have higher activation energy than the low CaO coal. PMID:24250259

Pintana, Pakamon

2013-01-01

86

Sensitivity Analysis of Discrete Stochastic Systems Rudiyanto Gunawan,* Yang Cao,y  

E-print Network

Sensitivity Analysis of Discrete Stochastic Systems Rudiyanto Gunawan,* Yang Cao,y Linda Petzold, University of California, Santa Barbara, California ABSTRACT Sensitivity analysis quantifies the dependence of system behavior on the parameters that affect the process dynamics. Classical sensitivity analysis

Cao, Yang

87

The mineralogy and geochemistry of quartz-tourmaline schlieren in the granites of the Primorsky Complex, Western Baikal Region  

NASA Astrophysics Data System (ADS)

Quartz-tourmaline schlieren have been found within rapakivi-like granites of the Early Proterozoic Primorsky Complex in the Western Baikal Region. These rocks are biotite leucogranites with normal alkalinity (A/CNK = 1.00-1.04); a high iron mole fraction (92-95%); a K2O/Na2O value of about 2.0; relatively high F, Li, Rb, Cs, Sn, Pb, Th, and U contents; and low Ba, Sr, Eu, Zn, Sc, and V contents. The schlieren composed of quartz and tourmaline with relics of feldspar also contain fluorite, rare muscovite, chlorite, and accessory rutile, ilmenite, zircon, monazite, xenotime, and bastnäsite. B2O3 and F contents in the schlieren are 2.29-2.63 and 0.30-0.47 wt %, respectively. Fe2O3 (4.8-5.4 wt %), F, and H2O contents are higher in these schlieren than in the host granite, while SiO2, CaO, Na2O, K2O, and P2O5 contents are lower than in host rocks. K2O/Na2O values decrease in the schlieren down to 0.4. Enrichment of the schlieren in Fe and other ore elements (Zn, Co, Cu, Sn, etc.), together with B, F, H2O, and Na, suggests that they crystallized from fluid-saturated melt segregated from aluminosilicate melt in the apical part of a shallow-seated intrusion. The formation of tourmaline may be related to the interaction of the fluid with feldspars in the crystallizing granites; it was accompanied by a separation of fluid F-CO2. Quartz precipitated at the next stage, due to the acidic character of the aqueous fluid. In general, the relationships of minerals in the schlieren indicate distinct fractionation of LREE, HREE, and Y in the fluid-saturated melt.

Savel'eva, V. B.; Bazarova, E. P.; Kanakin, S. V.

2014-12-01

88

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

89

Chemical durability and Structural approach of the glass series (40-y) Na2O-yFe2O3-5Al2O3-55P2O5-by IR, X-ray diffraction and Mössbauer Spectroscopy  

NASA Astrophysics Data System (ADS)

The relationship between the composition and structure for the glasses of general composition (40-y)Na2O-yFe2O3-5Al2O3-55P2O5 (5<=y<=20), has been studied. The chemical durability and density of these glasses increase with increasing Fe2O3 content. The dissolution rate (DR), calculated from the weight loss in distilled water at 90°C for up to 20 days was ? 3.10-9 g/cm2/mn which is 30 times lower than that of window glass. The structure and valence states of the iron ions in the glasses were investigated using, X-ray diffraction, 57Fe Mössbauer spectrometry, potentiometric analysis, and infrared spectroscopy. Both Mössbauer spectrometry and potentiometric analysis allow to estimate both Fe2+ and Fe3+ contents in all these glasses. X-ray diffraction indicates that the local structure of iron phosphate glasses is related to the short range structures of NaFeP2O7. Infrared spectra indicate the formation of P-O-Fe bonds in the pyrophosphate glasses that replace P-O-Na bonds. The presence of a small content of Al2O3 in the glass seems to play a role as a network modifier. The addition of Fe2O3 to Al2O3 in phosphate glasses favours the enhancement of the formation of pyrophosphate units because iron ions have stronger effect on the depolymerization of metaphosphate chains than the aluminium ions. Finally, the I.R spectra indicate that the presence of P-O-Fe bands of these glasses containing more than 15 mol%Fe2O3 is consistent with their good chemical durability.

Aqdim, S.; Sayouty, El H.; Elouad, B.; Greneche, J. M.

2012-02-01

90

[Quantitative estimation of CaO content in surface rocks using hyperspectral thermal infrared emissivity].  

PubMed

The objective of the present paper is to study the quantitative relationship between the CaO content and the thermal infrared emissivity spectra. The surface spectral emissivity of 23 solid rocks samples were measured in the field and the first derivative of the spectral emissivity was also calculated. Multiple linear regression (MLR), principal component analysis (PCR) and partial least squares regression (PLSR) were modeled and the regression results were compared. The results show that there is a good relationship between CaO content and thermal emissivity spectra features; emissivities become lower when CaO content increases in the 10.3-13 mm region; the first derivative spectra have a better predictive ability compared to the original emissivity spectra. PMID:22242490

Zhang, Li-Fu; Zhang, Xue-Wen; Huang, Zhao-Qiang; Yang, Hang; Zhang, Fei-Zhou

2011-11-01

91

Thermodynamics of strained vanadium dioxide single crystals Yijia Gu, Jinbo Cao, Junqiao Wu, and Long-Qing Chen  

E-print Network

Thermodynamics of strained vanadium dioxide single crystals Yijia Gu, Jinbo Cao, Junqiao Wu;Thermodynamics of strained vanadium dioxide single crystals Yijia Gu,1,a Jinbo Cao,2 Junqiao Wu,2 and Long Vanadium dioxide undergoes a metal­insulator transition, in which the strain condition plays an important

Chen, Long-Qing

92

Oxide nanowires for solar cell applications Qifeng Zhang, Supan Yodyingyong, Junting Xi, Daniel Myers and Guozhong Cao*  

E-print Network

to the electron collecting electrode. Such an enhancement effect could be further boosted while the nanowires were has published over 100 papers and book chapters. Guozhong Cao Guozhong Cao, PhD, is Boeing- Steiner at the University of Washington. He has published over 280 refereed papers and authored and edited 5 books including

Cao, Guozhong

93

Linear theory for optimal control of molecular wave packets Jianshu Cao and Kent R. Wilson  

E-print Network

Linear theory for optimal control of molecular wave packets Jianshu Cao and Kent R. Wilson proposals for the quantum control of matter have been suggested 1­7 , among which optimal control theory has-0339 Received 14 August 1996 A linear theory for optimizing optical fields to achieve a molecular configuration

Cao, Jianshu

94

Relating theories of actions and reactive control Chitta Baral and Tran Cao Son  

E-print Network

Relating theories of actions and reactive control Chitta Baral and Tran Cao Son Department In this paper 1 we give a formal characterization of reactive control using ac­ tion theories. In the process we provenly correct control modules. We then extend our approach to action theories and control modules

Baral, Chitta

95

The Cracking Experiment Research of Tar by CaO Catalyst  

NASA Astrophysics Data System (ADS)

The tar from rice husk gasification for power generation was taken as an example to be catalytically cracked by CaO catalyst. The experimental results showed the cracking efficiency of tar greatly increased from 28.66% by thermal cracking to 65.6% by catalytic cracking, the gas compositions from tar being cracked were H2, CO, CH4, and CO2, and the H2 was a majority of them. The DSC and XRT analysis revealed that the deposit carbon could be found after tar was catalytically cracked and the deposit carbon efficiency could reach 30.51%. The SEM photographs of CaO catalyst used as catalyst showed that the CaO catalyst was enwrapped by the deposit carbon and decreased its catalytic activity, at the same time, the pressure drop of gas passing through catalyst bed increased because of the deposit carbon, it was different for us to operate the cracking reactor of tar and CaO catalyst in the cracking reactor must be regenerated for its stable operation.

Lit, X. H.; Mi, T.; We, Z. S.; Chen, Y. F.; Wu, Q. X.

96

-closure, -closure and generalized closed sets J. Cao, M. Ganster, I. Reilly and M. Steiner  

E-print Network

-closure, -closure and generalized closed sets J. Cao, M. Ganster, I. Reilly and M. Steiner space via the associated -closure and -closure. The relationships among these new classes and existing and Preliminaries Let (X, ) be a topological space. Recall that a point x X is said to be in the -closure (resp

Ganster, Maximilian

97

Strong, Ductile Magnesium-Zinc Nanocomposites MICHAEL DE CICCO, HIROMI KONISHI, GUOPING CAO, HONG SEOK CHOI,  

E-print Network

of materials synthesis and processing. Most metal matrix nanocomposites (MMNCs) to date are made with expensiveStrong, Ductile Magnesium-Zinc Nanocomposites MICHAEL DE CICCO, HIROMI KONISHI, GUOPING CAO, HONG that the MgZn2 formation resulted in elimination of other intermetallics in the Mg-4Zn nanocomposite

Lakes, Roderic

98

Sensor Relocation in Mobile Sensor Networks Guiling Wang, Guohong Cao, Tom La Porta, and Wensheng Zhang  

E-print Network

Sensor Relocation in Mobile Sensor Networks Guiling Wang, Guohong Cao, Tom La Porta, and Wensheng of research on using mobility in sensor networks to assist in the initial deployment of nodes. Mobile sensors nodes such as small size and low cost, sensor networks [10], [13], [15], [17], [1] have become adopted

Zhang, Wensheng

99

Dynamics of condensation in totally asymmetric inclusion process Jiarui Cao, Paul Chleboun and Stefan Grosskinsky  

E-print Network

Dynamics of condensation in totally asymmetric inclusion process Jiarui Cao, Paul Chleboun inclusion process (TASIP) Dynamics of condensation Two condensates interaction Conclusion and further work Condensation phenomenon is said to occur when a finite fraction of the total quantity (particles, mass, wealth

Sengun, Mehmet Haluk

100

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

101

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...

102

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...

103

3D Fingerprint Phantoms Sunpreet S. Arora, Kai Cao and Anil K. Jain  

E-print Network

3D Fingerprint Phantoms Sunpreet S. Arora, Kai Cao and Anil K. Jain Department of Computer Science data. To overcome this limitation, use of a large number of 2D synthetic fingerprints for evaluating fingerprint systems had been proposed. However, the utility of 2D synthetic fingerprints is limited

104

METROLOGY IN UNCALIBRATED IMAGES GIVEN ONE VANISHING POINT Hassan Foroosh Xiaochun Cao Murat Balci  

E-print Network

METROLOGY IN UNCALIBRATED IMAGES GIVEN ONE VANISHING POINT Hassan Foroosh Xiaochun Cao Murat Balci in the perspective images. 1. INTRODUCTION Metrology from uncalibrated images is becoming of increas- ing interest al. [3] proposed an approach for single view metrology, and showed that affine scene structure can

Foroosh, Hassan

105

Can Facial Metrology Predict Gender? Deng Cao, Cunjian Chen, Marco Piccirilli,  

E-print Network

Can Facial Metrology Predict Gender? Deng Cao, Cunjian Chen, Marco Piccirilli, Donald Adjeroh the question of whether facial metrology can be exploited for reliable gender prediction. A new method based solely on metrological information from fa- cial landmarks is developed. Here, metrological features

Ross, Arun Abraham

106

La Zona Franca y su caos DesirDesir GmezGmez TorrentTorrent  

E-print Network

La Zona Franca y su caos DesiréDesiré GàmezGàmez TorrentTorrent #12;ESTRUCTURAESTRUCTURA 1. Conclusiones4. Conclusiones #12;¿Cual es el sustrato?¿Cual es el sustrato? Linea 9: Foneria de 48-51 m

Politècnica de Catalunya, Universitat

107

Stability Analysis of Three-Dimensional Colloidal Domains: Quadratic Fluctuations Jianlan Wu and Jianshu Cao*  

E-print Network

and Jianshu Cao* Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts-assemble in a charged colloidal suspension with competing short- range attraction and long-range Yukawa repulsion thermodynamic properties of domains in charged colloidal suspensions, analytical calculations are complicated

Cao, Jianshu

108

Effective pair potential for Ca-O bonds in CaGeO3 polymorphs  

NASA Astrophysics Data System (ADS)

The CaGeO3 perovskite and garnet were synthesized in a cubic anvil type apparatus under high pressure. The measurements of Ca and Ge K- edge XAFS spectra were carried out in the transmission mode at temperature up to 700 K. The effective pair potentials V(u)=?u2/2+?u3/3!, for Ca-O bond in various phases of CaGeO3 have been investigated by the temperature dependence of EXAFS Debye-Waller factors. The potential coefficient ? for the Ca-O bond in perovskite-type CaGeO3 is small, 4.4 eV/Å2 compared with those in garnet (6.0 eV/Å2) and wollastonite (6.4 eV/Å2). The potential for Ca-O bond in perovskite is broader than those in other CaGeO3 polymorphs, which is one reason for the Clausius-Clapeyron's curve for perovskite-garnet phase boundary having a negative slope. The potential coefficients for the Ca-O in perovskite are significantly smaller than those for the longer Ge-Ge distances as the framework vibration though the potential coefficient decreases usually as a result of the larger bond distance.

Koganemaru, A.; Yoshiasa, A.; Wang, L.; Nakatani, T.; Nakatsuka, A.; Okube, M.; Arima, H.; Sugiyama, K.

2013-04-01

109

Evaluation of biological cell properties using dynamic indentation measurement Guoxin Cao* and Namas Chandra  

E-print Network

Evaluation of biological cell properties using dynamic indentation measurement Guoxin Cao February 2010 Viscoelastic mechanical properties of biological cells are commonly measured using atomic on numerical simulation is built to determine the cell mechanical properties. It is shown that the existing

Farritor, Shane

110

Size dependent thermal conductivity of single-walled carbon nanotubes Ajing Cao and Jianmin Qu  

E-print Network

Size dependent thermal conductivity of single-walled carbon nanotubes Ajing Cao and Jianmin Qu-dependent thermal conductivity in single-walled carbon nanotubes with lengths up to micrometers at room temperature. It is found that the size-dependent thermal conductivity of single-walled carbon nanotubes can be described

Chen, Wei

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

Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia Wang  

E-print Network

1 Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia Wang deployment would worsen the situation even more [29]. The increase in the size of the DFZ routing ta- ble has

Keinan, Alon

113

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

NASA Astrophysics Data System (ADS)

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 convergence has slowed down to less than a few mm/a, the slab now tearing off leading hot asthenospheric mantle to flow in between the trailing slab and the crust. A successful recipe for ultrapotassic magmas requires K/Na fractionation at some previous stage. Melts from fluid-absent melting of carbonaceous pelites at >3 GPa are ultrapottasic phonolites (SiO2 ~64 wt%) and have K2O/Na2O up to 9 because of residual cpx with jadeite80. The effect of CO2 is to stabilize residual jadeite, to lower SiO2, and to increase K2O/Na2O ratios (as compared to CO2 free melts with K2O/Na2O of 1-3 and SiO2 = 73-77 wt%). The carbonaceous pelite melts were equilibrated with fertile, refractory but cpx bearing mantle, and wherlite. At sufficient pressures (3.5 GPa) and XCO2 in the volatile component, hybridization of the carbonaceous pelite melts produces highly subsilicic kamafugites, with K2O/Na2O only slightly lowered, and XMg's >0.70 as characteristic of primitive melts. The essential role of CO2 is to reduce the olivine saturation volume and to shift the olivine-cpx-opx cotectic to lower SiO2. The Italian kamafugites are ultracalcic (CaO/Al2O3 = 1.2-1.4), and although carbonaceous pelite melts have little CaO and 20 wt% Al2O3, the assimilation of cpx and production of aluminous opx leads to ultracalcic compositions when equilibrated with refractory peridotite or wherlite. Temperatures necessary for the fluid absent carbonaceous pelite melting are 1050-1150 °C, far above any reasonable subduction geotherm. Hybridization in the mantle requires 1320-1400 °C (at 3.0-3.5 GPa). The proposition is, that the carbonaceous pelite melts only form in thermally relaxing slabs typical for an ending subduction. Slab break off causes inflow of hot asthenospheric mantle, which further heats the trailing edge of the slab. Normally, subduction ends through continental collision at the surface, and the melts from the trailing edge appear to freeze in the relatively cool mantle below the orogen and await the next thermal event in order to form group II kimberlites. In the particular Italian situation, where large scale plate tectonic movements changed the convergence into a strike slip, temperatures of the trailing slab edge and the asthenosphere are apparently sufficient to keep the carbonaceaous slab melts liquid during hydridization in the mantle, leading to the surface kamafugites. The short longevity of the ultrapotassic magmatism (800 ka) collaborates the concept of a one-time event, i.e. the one-time melting of the trailing slab edge during it's break-off.

Schmidt, M. W.

2007-12-01

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

2012-12-28

115

Treatability of PCB-contaminated soils with quicklime (CaO)  

Microsoft Academic Search

The possibility that quicklime (calcium oxide, CaO) can destroy PCBs has received much attention over the past year. Observations at an EPA remediation site, where lime-containing kiln dusts were used for interim stabilization of PCB-containing wastes prompted the EPA to sponsor a small research project to investigate quicklime-PCB interactions. That study reported decreases in PCB content in synthetic, PCB-spiked soil

D. Mauro; B. B. Taylor

1992-01-01

116

Mechanism of CaO reaction with H 2S: Diffusion through CaS product layer  

Microsoft Academic Search

Heterogeneous non-catalytic reaction between CaO and H2S to capture sulfur in coal-fired gasifier is studied in a differential bed flow-through reactor. Particles of CaO (<10?m) are exposed to simulated fuel gas containing up to 5000ppm H2S in the temperature range 700–900°C. The effects of reaction temperature, H2S concentration, and sorbent surface area on the extent of sulfur capture and conversion

Rajeev Agnihotri; Shriniwas S. Chauk; Suhas K. Mahuli; Liang-Shih Fan

1999-01-01

117

[Development of ceramic standard samples used for X-ray fluorescence spectrometric analysis].  

PubMed

The preparation of 17 kinds of ceramic standard samples (CSS) is introduced briefly in the present paper, and the experimental results of the sintered CSS by using EPMA and XRF are discussed in detail. The conclusions can be mainlydrawn that the CSS, which have high density, low water absorption and good homogeneity of element distribution, have similar phase structure (or matrix) to the bodies of ancient ceramics, and perfectly meet the requirements of being used as ceramic standard samples. This set of CSS are expected to play an important role in x-ray fluorescence spectrometric quantitative analysis of Na2O, MgO, Al2O3, SiO2, K2O, CaO, TiO2 and Fe2O3 in the body of ancient ceramics and can provide accurate and reliable data for study and identification of ancient ceramics. PMID:21284202

Zhu, Ji-hao; Feng, Song-lin; Chu, Feng-you; Feng, Xiang-qia; Xie, Guo-xi; Yan, Ling-tong; Li, Liz

2010-11-01

118

Major and trace elements in igneous rocks from Apollo 15.  

NASA Technical Reports Server (NTRS)

The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow.

Helmke, P. A.; Blanchard, D. P.; Haskin, L. A.; Telander, K.; Weiss, C.; Jacobs, J. W.

1973-01-01

119

Volatile fractionation and tektite source material  

NASA Technical Reports Server (NTRS)

The arguments used by Love and Woronow (1988) to assess the role played in the origin of bediasites by extensive volatile fractionation are critically examined. Using the ratios of 'refractory' oxides, CaO, Al2O3, and MgO, to the 'volatile' oxides, Na2O and K2O, these authors concluded that vapor fractionation did not play a significant role. In this paper, experimental evidence is presented that shows that the assumption of volatility for the alkali elements (as least with respect to silica) to be not valid under the conditions under which tektites formed. It is shown that the results of vapor fractionation in experiments on glasses of tektite composition are approximately parallel the trends seen in bediasite analysis.

Walter, Louis S.

1989-01-01

120

Semimicro chemical and x-ray fluorescence analysis of lunar samples  

USGS Publications Warehouse

Major and selected minor elements were determined in seven whole rock fragments, five portions of pulverized lunar rock, and the lunar soil. Three different rock types were represented: vesicular, fine-grained basaltic rocks; medium-to coarse-grained, vuggy gabbroic rocks; and breccia. The ranges (in percent) for the major constituents of the lunar samples are: SiO2, 38 to 42; Al2O3, 8 to 14; total iron as FeO, 15 to 20; MgO, 6 to 8; CaO, 10 to 12; Na2O, 0.5 to 1; K2O, 0.05 to 0.4; TiO2, 8 to 13; MnO, 0.2 to 0.3; and Cr2O3, 0.2 to 0.4. The high reducing capacity of the samples strongly suggests the presence of Ti(III).

Rose, H.J., Jr.; Cuttitta, F.; Dwornik, E.J.; Carron, M.K.; Christian, R.P.; Lindsay, J.R.; Ligon, D.T.; Larson, R.R.

1970-01-01

121

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

122

Development of CaO coatings by thermal and chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We conducted several experiments to test electrically insulating CaO coatings on a V-4Cr-4Ti alloy for application in the Li environment of liquid metal blankets in fusion reactors. Two processes that involve double Ca deposition/oxidation steps were developed to successfully coat V-4Cr-4Ti alloy samples with stable CaO. During the study, we examined several geometrical arrangements, using tabs and/or rod specimens. After Ca deposition from the vapor phase, the specimens were oxidized in an Ar-10 vppm O 2 environment at ?600 °C to convert the deposited metal into oxide, whereupon they exhibited insulating characteristics. Several coated specimens were then exposed to Li-2.8 at.%Ca at 500-700 °C to determine chemical compatibility and mechanical integrity. Depth profile analysis of the coatings was conducted to evaluate the compositional changes in the coatings and to assess the transport, if any, of substrate and coating constituents. Microstructural characteristics of the coatings were evaluated by scanning electron microscopy. The preliminary results indicate that CaO is a viable coating for V-Li advanced blankets.

Natesan, K.; Uz, M.; Smith, D. L.

2002-12-01

123

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

2013-12-15

124

Sampling and major element chemistry of the recent (A.D. 1631-1944) Vesuvius activity  

USGS Publications Warehouse

Detailed sampling of the Vesuvius lavas erupted in the period A.D. 1631-1944 provides a suite of samples for comprehensive chemical analyses and related studies. Major elements (Si, Ti, Al, Fetotal, Mn, Mg, Ca, Na, K and P), volatile species (Cl, F, S, H2O+, H2O- and CO2), and ferrous iron (Fe2+) were determined for one hundred and forty-nine lavas and five tephra from the A.D. 1631-1944 Vesuvius activity. The lavas represent a relatively homogeneous suite with respect to SiO2, TiO2, FeOtotal, MnO and P2O5, but show systematic variations among MgO, K2O, Na2O, Al2O3 and CaO. The average SiO2 content is 48.0 wt.% and the rocks are classified as tephriphonolites according to their content of alkalis. All of the lavas are silica-undersaturated and are nepheline, leucite, and olivine normative. There is no systematic variation in major-element composition with time, over the period A.D. 1631-1944. The inter-eruption and intra-eruption compositional differences are the same magnitude. The lavas are highly porphyritic with clinopyroxene and leucite as the major phases. Fractionation effects are not reflected in the silica content of the lavas. The variability of MgO, K2O, Na2O, and CaO can be modelled as a relative depletion or accumulation of clinopyroxene. ?? 1993.

Belkin, H.E.; Kilburn, C.R.J.; de Vivo, B.

1993-01-01

125

Age, origin, and tectonic implications of Palaeozoic rapakivi granites in the North Qaidam orogen, Northwest China  

NASA Astrophysics Data System (ADS)

Palaeozoic rapakivi granites occur in the western segment of the China Central Orogenic System. Exhibiting typical rapakivi texture (Fig. 1), these granites contain magmatic microgranular enclaves of intermediate compositions. SHRIMP zircon U-Pb ages for the granites and enclaves are 433 × 5 Ma and 433 × 3 Ma, respectively. The rapakivi granites are magnesian to ferroan, calc-alkalic to alkalic, and are characterized by high FeOt/(FeOt + MgO) (0.74-0.91) and Ga/Al ratios, and SiO2, Na2O + K2O and rare earth element (apart from Eu) contents, but low CaO, Ba, and Sr contents. These are typical A-type granite geochemical features. The granites and enclaves exhibit a uniform decrease in TiO2,CaO, Na2O, K2O, FeO, and MgO with increasing SiO2, and both lithologies have similar trace element patterns. Whole-rock ?Nd(t) values vary from -9.2 to -8.7 for the granites and from -9.0 to -8.4 for the enclaves, but zircon ?Hf(t) values vary more widely from -5.8 to -0.2 and -4.6 to +5.1, respectively. Our data suggest that the granites and enclaves have crystallized from different magmas. The granites appear to have been derived from old continental crust, whereas the enclaves required a source having a juvenile component. The spherical shape and undeformed nature of the granites and their geochemical characteristics, coupled with the (ultra)-high pressure metamorphism (494 to 460Ma) and evolution of Palaeozoic granitoid magmatism in the North Qaidam orogen, indicate that the rapakivi granites were generated in a post-collisional setting. These rocks are therefore an example of Palaeozoic rapakivi granites emplaced in a post-collisional, extensional orogenic setting.

Wang, X.; Hu, N.; Castro, A.; Wang, T.; Lu, X.

2013-12-01

126

Biomineral microstructures in ferromanganese nodules: evidence of the biological and abiogenous origin  

NASA Astrophysics Data System (ADS)

Manganese oxides, which are widespread and of great practical importance, are formed and transformed by the active role of microorganisms. Manganese aggregates occur as both crystallized varieties and disordered fine-grained phases with significant ore grade and up to 50-60 vol % of X-ray amorphous components. X-ray amorphous nanosizedMn oxides in Fe-Mn nodules from the Pacific Ocean floor were examined from the standpoint of their biogenic origin. SEM examination showed abundant mineralized biofilms on the studied samples. The chemical composition of bacterial mass is as follows (wt %): 28.34 MnO, 17.14 Fe2O3, 7.11 SiO2, 2.41 CaO, 17.90 TiO2, 1.74Na2O,1.73 A12O3,1.30 MgO, 1.25P2O5,1.25 SO3,0.68 CoO, 0.54 CuO, 0.53 NiO, and 0.50 K2O. The chemical composition of fossilized cyanobacterial mats within the interlayer space of nodules is as follows (wt %): 48.35 MnO, 6.23 Fe2O3, 8.76 MgO, 5.05 A12O3, 4.45 SiO2, 3.63 NiO, 2.30 Na2O, 2.19 CuO, 1.31 CaO, and 0.68 K2O is direct evidence for participation of bacteria in Mn oxide formation. This phase consists of mineralized glycocalix consisting of nanosized flakes of todorokite. Native metals (Cu, Fe, and Zn) as inclusions 10-20 ?m in size were identified in ferromanganese nodules as well. The formation of native metals can be explained by their crystallization at highly reducing conditions maintained by organic matter.

Lysyuk, G. N.

2011-10-01

127

DUSTER: collection of meteoric CaO and carbon smoke particles in the upper stratosphere  

NASA Astrophysics Data System (ADS)

Nanometer CaO and pure carbon smoke particles were collected at 38-km altitude in the upper stratosphere in the Arctic during June 2008 using DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval), a balloon-borne instrument for the non-destructive collection of solid particles between 200 nm to 40 microns. We report the collection of micron sized CaCO3 (calcite) grains. Their morphologies show evidence of melting and condensation after vaporization suggest at temperatures of approximately 3500 K. The formation environment of the collected grains was probably a dense dust cloud formed by the disintegration of a carbonaceous meteoroid during deceleration in the Earth's atmosphere.

Rietmeijer, F. J. M.; Della Corte, V.; Rotundi, A.; Ferrari, M.; Palumbo, P.

2014-04-01

128

Effect of CaO Addition on Iron Recovery from Copper Smelting Slags by Solid Carbon  

NASA Astrophysics Data System (ADS)

We investigated the effect of flux (lime) addition on the reduction behavior of iron oxide in copper slag by solid carbon at 1773 K (1500 °C). In particular, we quantified the recovery of iron by performing typical kinetic analysis and considering slag foaming, which is strongly affected by the thermophysical properties of slags. The iron oxide in the copper slag was consistently reduced by solid carbon over time. In the kinetic analysis, we determined mass transfer coefficients with and without considering slag foaming using a gas holdup factor. The mass transfer of FeO was not significantly changed by CaO addition when slag foaming was ignored, whereas the mass transfer of FeO when slag foaming was considered was at a minimum in the 20 mass pct CaO system. Iron recovery, defined as the ratio of the amount of iron clearly transferred to the base metal ingot to the initial amount of iron in the slag phase before reduction, was maximal (about 90 pct) in the 20 mass pct CaO system. Various types of solid compounds, including Mg2SiO4 and Ca2SiO4, were precipitated in slags during the FeO reduction process, and these compounds strongly affected the reduction kinetics of FeO as well as iron recovery. Iron recovery was the greatest in the 20 mass pct CaO system because no solid compounds formed in this system, resulting in a highly fluid slag. This fluid slag allowed iron droplets to fall rapidly with high terminal velocity to the bottom of the crucible. A linear relationship between the mass transfer coefficient of FeO considering slag foaming and foam stability was obtained, from which we concluded that the mass transfer of FeO in slag was effectively promoted not only by gas evolution due to reduction reactions but also by foamy slag containing solid compounds. However, the reduced iron droplets were finely dispersed in foamy and viscous slags, making actual iron recovery a challenge.

Heo, Jung Ho; Kim, Byung-Su; Park, Joo Hyun

2013-12-01

129

Nb-doped CaO: an efficient electron donor system  

NASA Astrophysics Data System (ADS)

Transition metal atoms incorporated into insulating materials (oxides in particular) can deeply modify their adsorption properties. In particular, charge transfer to adsorbed species can be induced by the presence of substitutional dopants, which introduce new electronic states in the band gap of the host crystal. Here we show, by means of density functional theory calculations, that Nb represents an excellent dopant to turn the rather inactive CaO(100) surface into an electron-rich support. The charge transfer ability of the doped material is shown by comparing the adsorption properties of the electronegative Au atoms on pure and Nb-doped CaO. While in the first case the CaO-Au bonding is relatively weak and the Au atom is essentially neutral, in the Nb-doped system a much stronger adhesion is found due to a net charge transfer from the Nb dopant and to the formation of a gold anion. This mechanism occurs also for Nb in high oxidation states. Nb is thus an excellent modifier of the calcium oxide properties.

Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco

2014-08-01

130

Nb-doped CaO: an efficient electron donor system.  

PubMed

Transition metal atoms incorporated into insulating materials (oxides in particular) can deeply modify their adsorption properties. In particular, charge transfer to adsorbed species can be induced by the presence of substitutional dopants, which introduce new electronic states in the band gap of the host crystal. Here we show, by means of density functional theory calculations, that Nb represents an excellent dopant to turn the rather inactive CaO(100) surface into an electron-rich support. The charge transfer ability of the doped material is shown by comparing the adsorption properties of the electronegative Au atoms on pure and Nb-doped CaO. While in the first case the CaO-Au bonding is relatively weak and the Au atom is essentially neutral, in the Nb-doped system a much stronger adhesion is found due to a net charge transfer from the Nb dopant and to the formation of a gold anion. This mechanism occurs also for Nb in high oxidation states. Nb is thus an excellent modifier of the calcium oxide properties. PMID:24935643

Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco

2014-08-01

131

Mechanochemical degradation of ?-hexachlorocyclohexane by a planetary ball mill in the presence of CaO.  

PubMed

Although the use of the insecticide ?-hexachlorocyclohexane (HCH) is now prohibited in many countries because of its hazardousness, stockpiles of ?-HCH still exist. In this study, we subjected ?-HCH to mechanochemical (MC) treatment with a planetary ball mill in the presence of CaO to investigate the feasibility of using this method for the treatment of ?-HCH stockpiles. We confirmed the degradation of ?-HCH and investigated the degradation mechanism. The major intermediates were identified to be 1,3,4,5,6-pentachlorocyclohexene (?-PCCH) and chlorobenzenes (CBzs). Analysis of the steric structure of ?-HCH and identification of the degradation intermediates suggested that successive dehydrochlorination led to the formation of trichlorobenzenes. Products of further degradation (dichlorobenzenes, monochlorobenzene, and benzene) were also detected. Surprisingly, methane and ethane were also detected, which suggests cleavage of the C-C bonds of the cyclohexane ring and hydrogenation. All of the chlorine atoms in the ?-HCH could be transformed into inorganic chloride compounds by the MC treatment with CaO. Our results indicate that ?-HCH can be completely dechlorinated by MC treatment. PMID:22055315

Nomura, Yugo; Fujiwara, Kazuo; Terada, Akihiko; Nakai, Satoshi; Hosomi, Masaaki

2012-01-01

132

Impacts of the 2010 Amazon drought on forest structure and function using CAO AToMS  

NASA Astrophysics Data System (ADS)

The 2010 Amazon mega-drought is thought to have had a widespread impact on forest condition, including tree mortality. However, no large-scale, high-resolution information exists on changes in forest structure, function, turnover or other processes in response to the drought. With the possibility of increasing drought frequency in the Amazon basin, it is now critical that we develop repeat, large-area studies to assess impacts and recovery. Using the Carnegie Airborne Observatory Airborne Taxonomic Mapping System (AToMS), we assessed the impacts of the 2010 drought by repeat flying of approximately 500,000 hectares of lowland humid tropical forest in the Peru Amazon. The CAO AToMS Visible-to-Near-Infrared (VNIR) and Visible-to-Shortwave-Infrared (VSWIR) imaging spectrometers recorded changes in forest canopy spectral, chemical and physiological state from 2009 to 2011. Areas of greatest functional change were observed near the Peru-Brazil border in areas under heavy forest use for selective logging. The CAO AToMS waveform Light Detection and Ranging (LiDAR) instruments measured highest rates of treefall and canopy gap formation in areas subjected to combined drought and logging, and on low fertility soils. The results provide the first spatially-explicit, large-scale and ecologically detailed information on the response of Amazonian forests to drought.

Asner, G. P.; Martin, R. E.; Knapp, D. E.; Kennedy-Bowdoin, T.; Kellner, J.

2012-12-01

133

MAGNETIC BEHAVIOR OF IRON IONS IN THE P2O5·CaO GLASS MATRIX  

NASA Astrophysics Data System (ADS)

The temperature dependence of the magnetic susceptibility of xFe2O3·(100-x)-[P2O5·CaO] glasses with 0CaO glass matrix, the Fe2+ ion content is higher than that of the Fe3+ ions for glasses with x?10 mol%. For the glasses with x>35 mol%, the evaluated values of the ?eff indicate either the presence of Fe+ ions or the coordination influence on the magnetic moment of iron ions, but the presence of small quantities of the antiferromagnetic or ferrimagnetic interactions between iron ions in studied temperature range cannot be excluded. The high temperature susceptibility results indicate that the iron ions are isolated or participate in dipole-dipole interactions for glasses with x?35 mol% and are antiferromagnetically coupled for higher contents of Fe2O3.

ARDELEAN, I.; ANDRONACHE, C.; P??CU??, P.

134

Development of natural crude drug resources from Taiwan (X). Pharmacognostical studies on the Chinese crude drug "han-lian-cao".  

PubMed

In a previous paper(1), it was reported that the drug "Han-lian-cao", in Taiwan was derived from the entire plant or aerial part of Eclipta prostrata L. and Alternanthera sessilis R. Brown. In this paper, the histological studies of "Han-lian-cao" derived from Wedelia and Hypericum plants, and of 3 species of Wedelia related plants distributed in Taiwan were made. The results showed that it was possible to classify these species by their external and internal characteristics. In addition, a key to the characteristics of the whole plants of Eclipta, Alternanthera, Wedelia and Hypericum plants are hereby given. PMID:1605130

Chen, J Y; Lin, C C; Namba, T

1992-01-01

135

Exploring the ability of chlorophyll b to bind to the CP43? protein induced under iron deprivation in a mutant of Synechocystis PCC 6803 containing the cao gene  

Microsoft Academic Search

Cyanobacteria, unlike plants and green algae, do not contain chlorophyll (Chl) b. This is because of the absence of the cao gene which encodes the enzyme that catalyses a two step oxygenation of chlorophyllide a to chlorophyllide b. Recently, however, the cao gene of higher plants was engineered into Synechocystis PCC 6803 leading to Chl b synthesis in this cyanobacterium

James Duncan; Thomas Bibby; Ayumi Tanaka; James Barber

2003-01-01

136

OCAO Computer Refreshment Policy The NOAA CAO is responsible for budgeting and procuring all personal computers and other  

E-print Network

6/20/2007 OCAO Computer Refreshment Policy Purpose: The NOAA CAO is responsible for budgeting and procuring all personal computers and other support computers used by OCAO staff. To facilitate adequate capital planning and clarify acquisition policies, the following Computer Refreshment Policy

137

Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture  

E-print Network

Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture Nicholas S. Siefert Virginia 26507, United States ABSTRACT: We present experimental results of coal gasification-coal gasification kinetic rate. The syngas composition from the gasifier was roughly 20% methane, 70% hydrogen

Litster, Shawn

138

Superconductivity in Iron Telluride Thin Films under Tensile Stress L. X. Cao,1,* X. Y. Wang,2  

E-print Network

Superconductivity in Iron Telluride Thin Films under Tensile Stress Y. Han,1 W. Y. Li,1 L. X. Cao,1 for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese a tensile stress state, superconductivity of 13 K was introduced into FeTe, a nonsuperconducting parent

Wang, Wei Hua

139

An Air Traffic Prediction Model based on Kernel Density Estimation Yi Cao,1 Lingsong Zhang,2 and Dengfeng Sun3  

E-print Network

through sophisticated flight dynamics [1]. However, for the Air Traffic Control Sys- tem Command Center at an Air Route Traffic Control Center (simply denoted as Center hereafter) level [2]. It forecasts aircraftAn Air Traffic Prediction Model based on Kernel Density Estimation Yi Cao,1 Lingsong Zhang,2

Sun, Dengfeng

140

A diameter distribution model for even-aged beech in Denmark Thomas Nord-Larsen a,*, Quang V. Cao b  

E-print Network

A diameter distribution model for even-aged beech in Denmark Thomas Nord-Larsen a,*, Quang V. Cao b 2006 Abstract We developed a diameter distribution model for even-aged stands of European beech in Denmark using the Weibull distribution. The model parameters were estimated using a large dataset from

Cao, Quang V.

141

Genetic structure of the invasive Chromolaena odorata W H YE, H P MU, H L CAO & X J GE  

E-print Network

Genetic structure of the invasive Chromolaena odorata in China W H YE, H P MU, H L CAO & X J GE as the main cause of the genetic structure observed in C. odorata. Keywords: biocontrol, Chromolaena odorata (L.) RM King and H. Robinson (Siam weed) is a perennial member of the Compositae family. This species

Brown, Cynthia S.

142

Phonon-Mediated Electron Transport through CaO Thin Films  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy has developed into a powerful tool for the characterization of conductive surfaces, for which the overlap of tip and sample wave functions determines the image contrast. On insulating layers, as the CaO thin film grown on Mo(001) investigated here, direct overlap between initial and final states is not enabled anymore and electrons are transported via hopping through the conduction-band states of the oxide. Carrier transport is accompanied by strong phonon excitations in this case, imprinting an oscillatory signature on the differential conductance spectra of the system. The phonons show a characteristic spatial dependence and become softer around lattice irregularities in the oxide film, such as dislocation lines.

Cui, Yi; Tosoni, Sergio; Schneider, Wolf-Dieter; Pacchioni, Gianfranco; Nilius, Niklas; Freund, Hans-Joachim

2015-01-01

143

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

144

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 ?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

145

Cathodic behavior of molten CaCl2-CaO and CaCl2-NaCl-CaO  

NASA Astrophysics Data System (ADS)

The cathodic behavior of molten CaCl2, CaCl2-CaO and equimolar CaCl2-NaCl-CaO was studied by cyclic voltammograms and constant potential polarization at temperatures of 1123 to 1173 K on molybdenum and titanium electrodes. The diffusion coefficient of Ca2+ (CaO) in molten CaCl2-CaO was calculated from the linear relationship between the square root of scan rate and the peak current density. The deposition potentials and the potential temperature coefficient of CaO in molten CaCl2-0.5mol%CaO and CaCl2-NaCl-0.5mol%CaO were also obtained from their cyclic voltammograms. The result shows that CaO is more easily reduced than CaCl2. The addition of NaCl in molten CaCl2-CaO induces the underpotential electrodeposition of CaO.

Wang, Shu-Lan; Wang, Wei; Li, Shi-Chao; Cao, Shan-Hui

2010-12-01

146

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.  

PubMed

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325?m achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. PMID:24525218

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

147

Crossover from two- to three-dimensional gold particle shapes on CaO films of different thicknesses  

NASA Astrophysics Data System (ADS)

The growth of Au particles on Mo(001)-supported CaO films has been investigated as a function of film thickness by means of scanning tunneling microscopy and spectroscopy. Whereas, monolayer Au islands develop in the low-thickness regime [1-25 monolayers (ML)], formation of three-dimensional (3D) deposits is revealed above 40-ML film thickness. The two-dimensional (2D) growth morphology is ascribed to a charge transfer out of the CaO/Mo support into the adparticles, resulting in a reinforcement of the Au-CaO interface interaction and a strong preference for a wetting growth of gold. In the limit of ultrathin films, this charge transfer is governed by electron tunneling from the Mo substrate into the Au islands and is driven by the different Fermi levels of both systems. Although tunneling transport breaks down beyond 5-10-ML film thickness, the signature of charge-mediated Au growth remains detectable for even thicker films. This finding suggests the presence of intrinsic charge centers in the CaO film that are able to donate electrons to the gold. We relate these donor centers to Mo ions that spontaneously have diffused from the Mo support into the CaO lattice during growth. Given the low mobility of Mo in the oxide matrix, the donor concentration diminishes with film thickness and, hence, the ability of the CaO to transfer electrons into the Au deposits. Consequently, the 2D growth behavior of Au changes into the 3D regime that is characteristic for metals on inert oxide surfaces. Spectroscopic characterization of the Au particles revealed pronounced electron quantization and Coulomb charging effects due to the reduced island size.

Shao, Xiang; Nilius, Niklas; Freund, Hans-Joachim

2012-03-01

148

CAOS - the new high resolution spectrograph for the 0.91m telescope at Serra La Nave .  

NASA Astrophysics Data System (ADS)

We report on the status of the new high-resolution spectrograph CAOS under construction for the 0.91m telescope at Serra La Nave, Italy. Starting from defined scientific motivations, we derived the best instrumental requirements to meet observational goals within typical constraints like good performances and reduced overall cost. The new instrument will be able to enlarge present observational research activity at INAF-OACt, allowing spectropolarimetry at high S/N ratios.

Spanò, P.; Leone, F.; Bruno, P.; Catalano, S.; Martinetti, E.; Scuderi, S.

149

Liaoxia Cao et S.Q. Wu (Gnetales): ephedroids from the Early Cretaceous Yixian Formation in Liaoning, northeastern China  

Microsoft Academic Search

Gnetalean compression-impression fossils are described from the Early Cretaceous Yixian Formation, Liaoning Province, north-eastern\\u000a China, and assigned to six species of Liaoxia Cao et S.Q. Wu. The fossils have opposite-decussate phyllotaxis and cones comprising 2–12 pairs of bracts. Ovulate cones\\u000a have seeds typically in a distal position. The species differ from each other and from previously described fossils in the

C. Rydin; S. Q. Wu; E. M. Friis

2006-01-01

150

Entangled quantum electronic wavefunctions of the Mn4CaO5 cluster in photosystem II  

NASA Astrophysics Data System (ADS)

It is a long-standing goal to understand the reaction mechanisms of catalytic metalloenzymes at an entangled many-electron level, but this is hampered by the exponential complexity of quantum mechanics. Here, by exploiting the special structure of physical quantum states and using the density matrix renormalization group, we compute near-exact many-electron wavefunctions of the Mn4CaO5 cluster of photosystem II, with more than 1 × 1018 quantum degrees of freedom. This is the first treatment of photosystem II beyond the single-electron picture of density functional theory. Our calculations support recent modifications to the structure determined by X-ray crystallography. We further identify multiple low-lying energy surfaces associated with the structural distortion seen using X-ray crystallography, highlighting multistate reactivity in the chemistry of the cluster. Direct determination of Mn spin-projections from our wavefunctions suggests that current candidates that have been recently distinguished using parameterized spin models should be reassessed. Through entanglement maps, we reveal rich information contained in the wavefunctions on bonding changes in the cycle.

Kurashige, Yuki; Chan, Garnet Kin-Lic; Yanai, Takeshi

2013-08-01

151

-CaO Slags by Al in Fe-Al(-Si) Melts  

NASA Astrophysics Data System (ADS)

Kinetic models considering mass transport in, (i) metal phase only and (ii) both metal and slag phases (mixed control or two-phase mass transfer) were developed for the reduction of SiO2 in a SiO2-Al2O3-CaO slag by Al in an Al-Fe melt. The models were validated with experiments of the reaction with Fe-Al melt and SiO2-Al2O3-CaO-MgOsat slags at 1873 K (1600 °C). The models predict that the rate of reaction is slower in the mixed control model because of the added resistance of slag phase mass transport. The mixed control becomes applicable when the slag contains low amounts of SiO2. In this case, when the initial Al content in the metal increases, the normalized rate of reaction decreases. The increased Al content in the metal retards the reaction due to the limited SiO2 provided to the reaction interface in the mixed control model. Sensitivity analyses were done using the models for the ratios of mass transfer coefficients of Si to Al, and Al2O3 to Si, along with slag density, which did not impose a significant effect.

Park, Jiwon; Sridhar, Seetharaman; Fruehan, Richard J.

2014-08-01

152

Inhibitory Effects of Daiokanzoto (Da-Huang-Gan-Cao-Tang) on P-Glycoprotein  

PubMed Central

We have studied the effects of various Kampo medicines on P-glycoprotein (P-gp), a drug transporter, in vitro. The present study focused on Daiokanzoto (Da-Huang-Gan-Cao-Tang), which shows the most potent inhibitory effects on P-gp among the 50 Kampo medicines studied, and investigated the P-gp inhibitory effects of Daiokanzoto herbal ingredients (rhubarb and licorice root) and their components by an ATPase assay using human P-gp membrane. Both rhubarb and licorice root significantly inhibited ATPase activity, and the effects of rhubarb were more potent than those of licorice root. The content of rhubarb in Daiokanzoto is double that in licorice root, and the inhibition patterns of Daiokanzoto and rhubarb involve both competitive and noncompetitive inhibition, suggesting that the inhibitory effects of Daiokanzoto are mainly due to rhubarb. Concerning the components of rhubarb, concentration-dependent inhibitory effects were observed for (?)-catechin gallate, (?)-epicatechin gallate, and (?)-epigallocatechin gallate. In conclusion, rhubarb may cause changes in the drug dispositions of P-gp substrates through the inhibition of P-gp. It appears that attention should be given to the interactions between these drugs and Kampo medicines containing rhubarb as an herbal ingredient. PMID:22969825

Watanabe, Yuka; Ikarashi, Nobutomo; Satoh, Toshiyuki; Ito, Kiyomi; Ochiai, Wataru; Sugiyama, Kiyoshi

2012-01-01

153

First-principles simulations of CaO and CaSiO3 liquids: structure, thermodynamics and diffusion  

NASA Astrophysics Data System (ADS)

We have performed first-principles molecular dynamics simulations of CaO and CaSiO3 liquids over broad ranges of pressure (0-150 GPa) and temperature (2,500-8,000 K) within density-functional theory. The simulated liquid structure changes considerably on compression with the mean cation-anion coordination numbers increasing nearly linearly with volume. The Ca-O coordination number increases from 5 (7) near the ambient pressure to 8 (10) at high pressure for CaO (CaSiO3) liquid. The Si-O coordination number increases from 4 to 6 over the same pressure regime. Our results show that both liquids are much more compressible than their solid counterparts implying the possibility of liquid-solid density crossovers at high pressure. The Grüneisen parameter of both the liquids increases with pressure, which is opposite in case of crystalline phases. The calculated self-diffusion coefficients strongly depend on temperature and pressure, thereby requiring non-Arrhenian representation with variable activation volume. The diffusivity differences between the two liquids tend to be large at low-temperature and low-pressure regime. Also, comparisons with MgSiO3 liquid suggest that network modifier cations Ca and Mg behave similarly though Ca is more coordinated and more mobile as compared to Mg.

Bajgain, Suraj K.; Ghosh, Dipta B.; Karki, Bijaya B.

2015-01-01

154

Li/Mo codoping of CaO films: a means to tailor the equilibrium shape of Au deposits.  

PubMed

Using scanning tunneling microscopy, we have investigated how the doping of CaO thin films affects the growth behavior of gold. Whereas 3D deposits develop on pristine films, 2D islands form after inserting 4% of Mo into the CaO lattice. Adding small amounts of Li to the Mo-doped CaO reinstalls the initial 3D growth regime. We assign this morphology crossover to charge transfer processes between the dopants and the ad-metal. Whereas Mo acts as an electron donor and provides excess charges to be transferred into the gold, Li creates electron traps in the oxide lattice that interrupt the charge flow toward the metal. The different Au charge states in the presence of the dopants are derived from different growth morphologies with anionic gold favoring a 2D mode due to an enhanced interface adhesion. Our work demonstrates how oxide doping can be exploited to tailor the equilibrium geometry of ad-particles on supported metal catalysts. PMID:22280016

Shao, Xiang; Nilius, Niklas; Freund, Hans-Joachim

2012-02-01

155

Canopy spectral and chemical diversity from lowland to tree line in the Western Amazon using CAO-VSWIR  

NASA Astrophysics Data System (ADS)

Canopy chemistry and spectroscopy offer insight into community assembly and ecosystem processes in high-diversity tropical forests. Results from one lowland site in the Peruvian Amazon suggests both an environmental and an evolutionary component of canopy trait development however, the degree to which larger environmental differences influence diversity in canopy traits and their respective spectroscopic signatures across remains poorly understood. The spectranomics approach explicitly connects phylogenetic, chemical and spectral patterns in tropical canopies providing the basis for analysis, while high-fidelity, airborne remote sensing measurements extend plot-level data to landscape-scale, achieving a comprehensive view of the region. In 2011, the Carnegie Airborne Observatory (CAO) was used to sample a large region of the Western Amazon Basin in southeastern Peru, extending from lowlands to tree line in the Andean mountains. The CAO Visible-Shortwave Imaging Spectrometer (VSWIR) collected 480-band high-fidelity imaging spectroscopy data of the forest canopy, while its high-resolution LiDAR captured information on canopy structure and the underlying terrain. The data were used to quantify relationships between environmental gradients and canopy chemical and spectral diversity. Results suggest strong environmental control with additional phylogenetic influence over canopy spectral and chemical properties, particularly those related to structure, defense and metabolic function. Data from CAO-VSWIR extends the large range in canopy chemical and spectral diversity related to environmental factors across the Western Amazon Basin.

Martin, R. E.; Asner, G. P.

2012-12-01

156

Micelle-Assisted Synthesis of Al2O3·CaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol  

PubMed Central

Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3·CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3·CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3·CaO nanocatalyst was found as 3.3?eV. PMID:24311980

Imtiaz, Ayesha; Khaleeq-ur-rahman, Muhammad; Adnan, Rohana

2013-01-01

157

Tephra record from the Sea of Marmara for the last 70 ka and its paleoceanographic implications  

NASA Astrophysics Data System (ADS)

Sea of Marmara (SoM) is a gateway between the Mediterraean and Black seas, and a tectonically active basin located on a transform plate boundary. Tephra record in the SoM is therefore very important for dating palaeoceanographic, paleoclimatic and tectonic events. We report three tephra units in cores from the SoM extending back to ca 70 ka BP and including an upper marine and a lower lacustrine units separated by a 12 ka (uncalib.) boundary. The uppermost tephra unit is up to 8 mm thick layer in the marine unit. It is heterogenous phonolitic with high total alkali content of 12.4-15.7 wt % and K2O/Na2O of 0.9 to 1.2. The middle and lower tephra layers occur in the lacustrine unit in ca 29 m-long Core MD-01-2430. The middle tephra (MT-1) is a 70 mm-thick homogeneously rhyolitic layer. The lower tephra (MT-2) is 140 mm thick and has a phonolitic-trachytic composition with CaO content of 1.7-1.9 wt % and bimodal K2O/Na2O of 1.0-1.4. Using their geochemical composition and stratigraphic analysis, we assign the tephra units, from top to bottom, to Vesuvius AP2 Pumice, Santorini Cape Riva and Campanian Ignimbrite, which have been previously dated at 3.5 ka BP, 21.95 ka BP, and 39.3 ka BP (all calender ka). The continuous sedimentary record in the Core MD-01-2430 covering the last ca 70 ka indicates that the SoM was lacustrine, disconnected from the Mediterraean Sea during MIS4, MIS3 and most of MIS2. This implies that the sill depth of the Çanakkale Strait (Dardanelles) was shallower than the present-day -65 m sill depth during MIS3 and MIS4. Figure 1: Morphotectonic map of the Sea of Marmara showing location of the studied cores (red stars). Figure 2: Geochemical biplots of tephra glass composition. a) Total alkali silica diagram b) FeO versus total alkalies for allocating cryptotephras from core MNTKS34 and ML01 to the AP2 tephra from Vesuvius. c) FeO versus CaO for correlating tephra MT1 with the Y-2 tephra from Santorini. d) SiO2 versus CaO for discriminating the MT2 tephra (Campanian Ignimbrite).

Cagatay, M.; Wulf, S.; Guichard, F.; Ozmaral, A.; Sancar; Akçer-Ön, S.; Henry, P.; Gasperini, L.

2013-12-01

158

Conversion of melt-derived microfibrous borate (13-93B3) and silicate (45S5) bioactive glass in a simulated body fluid.  

PubMed

Microfibrous bioactive glasses are showing a considerable capacity to heal soft tissue wounds, but little information is available on the mechanism of healing. In the present study, the conversion of microfibrous borate bioactive glass (diameter = 0.2-5 ?m) with the composition designated 13-93B3 (5.5 Na2O, 11.1 K2O, 4.6 MgO, 18.5 CaO, 3.7 P2O5, 56.6 B2O3 wt%) was evaluated in vitro as a function of immersion time in a simulated body fluid (SBF) at 37 °C using structural and chemical techniques. Silicate 45S5glass microfibers (45 SiO2, 24.5 Na2O, 24.5 CaO, 6 P2O5 wt%) were also studied for comparison. Microfibrous 13-93B3 glass degraded almost completely and converted to a calcium phosphate material within 7-14 days in SBF, whereas >85 % of the silica remained in the 45S5 microfibers, forming a silica gel phase. An amorphous calcium phosphate (ACP) product that formed on the 13-93B3 microfibers crystallized at a slower rate to hydroxyapatite (HA) when compared to the ACP that formed on the 45S5 fibers. For immersion times >3 days, the 13-93B3 fibers released a higher concentration of Ca into the SBF than the 45S5 fibers. The fast and more complete degradation, slow crystallization of the ACP product, and higher concentration of dissolved Ca in SBF could contribute to the capacity of the microfibrous borate 13-93B3 glass to heal soft tissue wounds. PMID:23233025

Liu, Xin; Rahaman, Mohamed N; Day, Delbert E

2013-03-01

159

Treatability of PCB-contaminated soils with quicklime (CaO)  

SciTech Connect

The possibility that quicklime (calcium oxide, CaO) can destroy PCBs has received much attention over the past year. Observations at an EPA remediation site, where lime-containing kiln dusts were used for interim stabilization of PCB-containing wastes prompted the EPA to sponsor a small research project to investigate quicklime-PCB interactions. That study reported decreases in PCB content in synthetic, PCB-spiked soil following the application of quicklime and heat. META Environmental, Inc., as a contractor to EPRI, recently completed research designed to evaluate the effectiveness of quicklime for treating PCBs in soil and sand matrices under several reaction conditions, and to examine the underlying dechlorination chemistry involved, if any. Experiments were run with PCB-spiked sand and with actual PCB-contaminated soil. A variety of experimental conditions were employed including tests in open and closed containers, at ambient and elevated temperatures, and over a range of one hour to four days. Granular quicklime, fly ash, and kiln dust were all tested for reaction with PCBs. Early experiments showed that a mixture of sand/quicklime/water at 1:3:1.5 by weight, placed in an insulated container reached a maximum temperature of 216[degree]C. Treatability experiments were subsequently run under controlled heat at room temperature, at 80[degree]C, and at 200[degree]C (following the initial temperature increase which occurs when water is added to quicklime). Little or no loss of PCBs was observed in open or closed containers at ambient or at 800[degree]C over any period of time studied. A significant decrease of PCBs levels was observed only in the high temperature experiments (above 200[degree]C), however the fate of the PCBs in those experiments was not determined. The conditions and the results of the PCB treatment tests are presented in this report, as well as recommendations for further studies.

Mauro, D.; Taylor, B.B. (Meta Environmental, Inc., Watertown, MA (United States))

1992-12-01

160

Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture  

SciTech Connect

We present experimental results of coal gasification with and without the addition of calcium oxide and potassium hydroxide as dual-functioning catalyst–capture agents. Using two different coal types and temperatures between 700 and 900 °C, we studied the effect of these catalyst–capture agents on (1) the syngas composition, (2) CO{sub 2} and H{sub 2}S capture, and (3) the steam–coal gasification kinetic rate. The syngas composition from the gasifier was roughly 20% methane, 70% hydrogen, and 10% other species when a CaO/C molar ratio of 0.5 was added. We demonstrated significantly enhanced steam–coal gasification kinetic rates when adding small amounts of potassium hydroxide to coal when operating a CaO–CaCO{sub 3} chemical looping gasification reactor. For example, the steam–coal gasification kinetic rate increased 250% when dry mixing calcium oxide at a Ca/C molar ratio of 0.5 with a sub-bituminous coal, and the kinetic rate increased 1000% when aqueously mixing calcium oxide at a Ca/C molar ratio of 0.5 along with potassium hydroxide at a K/C molar ratio of 0.06. In addition, we conducted multi-cycle studies in which CaCO{sub 3} was calcined by heating to 900 °C to regenerate the CaO, which was then reused in repeated CaO–CaCO{sub 3} cycles. The increased steam–coal gasification kinetics rates for both CaO and CaO + KOH persisted even when the material was reused in six cycles of gasification and calcination. The ability of CaO to capture carbon dioxide decreased roughly 2–4% per CaO–CaCO{sub 3} cycle. We also discuss an important application of this combined gasifier–calciner to electricity generation and selling the purge stream as a precalcined feedstock to a cement kiln. In this scenario, the amount of purge stream required is fixed not by the degradation in the capture ability but rather by the requirements at the cement kiln on the amount of CaSO{sub 4} and ash in the precalcined feedstock.

Siefert, Nicholas S.; Shekhawat, Dushyant; Litster, Shawn; Berry, David, A

2013-08-01

161

Kinetics of wetting for MgO, CaO, and BeO by Pd, Pt, and Rh melts  

NASA Astrophysics Data System (ADS)

The wetting of magnesium, calcium, and beryllium oxides (MgO, CaO, and BeO) is considered, depending on the ratios of the surface tensions of the oxides to the melts at inequality ?sg/?lg < 1 characteristic of metallophobic solid surfaces. It is shown that the changes in the wetting angle with temperature during isothermal exposure are determined by the ratio of the surface tensions of the phases ?MgO/?Me. It is found that the wetting angle moves down or up when the ratios of the surface tensions increase or decrease, respectively, depending on the values of ?sg and ?lg.

Timofeev, A. I.; Chentsov, V. P.

2015-01-01

162

Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature  

NASA Astrophysics Data System (ADS)

The electronic structure of CaO films of 10-60 monolayer thickness grown on Mo(001) has been investigated with synchrotron-mediated x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Upon annealing or reducing the thickness of the film, a rigid shift of the CaO bands to lower energy is revealed. This evolution is explained with a temperature-induced diffusion of Mo ions from the metal substrate to the oxide and their accumulation in the interface region of the film. The Mo substitutes divalent Ca species in the rocksalt lattice and is able to release electrons to the system. The subsequent changes in the Mo oxidation state have been followed with high-resolution XPS measurements. While near-interface Mo transfers extra electrons back to the substrate, generating an interface dipole that gives rise to the observed band shift, near-surface species are able to exchange electrons with adsorbates bound to the oxide surface. For example, exposure of O2 results in the formation of superoxo species on the oxide surface, as revealed from STM measurements. Mo interdiffusion is therefore responsible for the pronounced donor character of the initially inert oxide, and largely modifies its adsorption and reactivity behavior.

Cui, Yi; Pan, Yi; Pascua, Leandro; Qiu, Hengshan; Stiehler, Christian; Kuhlenbeck, Helmut; Nilius, Niklas; Freund, Hans-Joachim

2015-01-01

163

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

164

Liquidus Temperatures in the ``Cu2O''-FeO-Fe2O3-CaO System at Molten Metallic Copper Saturation  

NASA Astrophysics Data System (ADS)

Calcium ferrite slags, used in continuous copper-converting processes, can be described by the “Cu2O”-FeO-Fe2O3-CaO system at copper metal saturation. Equilibration/quenching/electron probe X-ray microanalysis (EPMA) techniques with primary phase substrate support have been used to experimentally determine liquidus and solidus data for this system for the primary phase fields of cuprite, dicalcium ferrite, and spinel from 1100 °C to 1250 °C. The resulting measurements are presented as liquidus and solidus isotherms in the “Cu2O”-“Fe2O3”-CaO system in equilibrium with metallic copper.

Nikolic, Stanko; Hayes, Peter C.; Jak, Evgueni

2009-12-01

165

Effect of CaO and SiO2 additives on magnetic properties of SrZn2-W type hexagonal ferrite  

Microsoft Academic Search

An experiment was carried out to investigate the effect of CaO and SiO2 additives on the magnetic and physical properties of Sr-Zn W-type hexagonal ferrite. The specimens were prepared by the conventional manufacturing method without atmosphere control. It was found that the magnetic properties of SrO·2ZnO·8Fe2 O3 are considerably improved on adding 1 wt% CaO and SiO2 together. The optimum

H. Yamamoto; T. Mitsuoka

1994-01-01

166

Microstructure and properties of K2O doped superconducting YBa2Cu3O7?x  

Microsoft Academic Search

K doped YBa2Cu2Ox powders have been obtained by incorporating K2CO3 to previously coprecipitated amorphous hydroxide mixtures. Synthesis was performed at 900‡C and an orthorhombic 1 2 3 phase was the final product. Sintering of isopressed bars was carried out from 920 to 940‡C. K doping up to 5 at % led to the development of dense bodies with good superconducting

J. Tartaj; J. F. Fernandez; P. Duran; C. Moure

1994-01-01

167

The determination of glycyrrhizic acid in Glycyrrhiza uralensis Fisch. ex DC. (Zhi Gan Cao) root and the dried aqueous extract by LC–DAD  

Microsoft Academic Search

A rapid, sensitive and specific reversed phase high-performance liquid chromatographic (LC) method with photodiode array detection (DAD) has been developed for the determination of glycyrrhizic acid in both the raw herb and a commercially prepared dried aqueous extract of Glycyrrhiza uralensis Fisch. ex DC. root (Zhi Gan Cao, liquorice). It was determined that extracting the raw herb in aqueous methanol

J. R. Hennell; S. Lee; C. S. Khoo; M. J. Gray; A. Bensoussan

2008-01-01

168

A picosecond electron gun for surface analysis M. Aeschlimann,a) E. Hull, J. Cao,b) C. A. Schmuttenmaer, L. G. Jahn,@ Y. Gao,b)  

E-print Network

A picosecond electron gun for surface analysis M. Aeschlimann,a) E. Hull, J. Cao,b) C. A investigations for a new design of an ultrashort pulsed laser activated electron gun for time resolved surface gun, in spite of an unusually long focal length and a small convergence angle of the pulsed electron

Cao, Jianming

169

Use of CaO as an activator for producing a price-competitive non-cement structural binder using ground granulated blast furnace slag  

SciTech Connect

The use of calcium oxide (CaO) demonstrates a superior potential for the activation of ground granulated blast furnace slag (GGBFS), and it produces a higher mechanical strength than calcium hydroxide [Ca(OH){sub 2}]. The mechanical strength differences between CaO- and Ca(OH){sub 2}-activated GGBFS binders are explored using isothermal calorimetry, powder X-ray diffraction, thermogravimetric and differential thermal analysis (TGA and DTA) as well as compressive strength testing. Calcium silicate hydrate (C–S–H), Ca(OH){sub 2} and a hydrotalcite-like phase are found as reaction products in all samples. The TGA and DTA results indicate that the use of CaO produces more C–S–H, although this is not likely to be the primary cause of higher strength development in the CaO-activated GGBFS. Rather, other factors such as porosity may govern the strength at a higher order of magnitude. Significant reduction of Ca(OH){sub 2} occurs only with the use of Ca(OH){sub 2}, followed by the formation of carbonate (CaCO{sub 3}), indicating carbonation. -- Highlights: •CaO showed a better potential for the activation of GGBFS than Ca(OH){sub 2}. •Strength test, XRD, TGA/DTA and isothermal calorimetry are used. •C-S-H, Ca(OH){sub 2}, and a hydrotalcite-like phase are found in all samples. •The use of Ca(OH){sub 2} causes some degree of carbonation.

Kim, Min Sik; Jun, Yubin; Lee, Changha, E-mail: clee@unist.ac.kr; Oh, Jae Eun, E-mail: ohjaeeun@unist.ac.kr

2013-12-15

170

Structure of polydisperse electrorheological fluids: Experiment M. Shen, J.G. Cao, H.T. Xue, J.P. Huang *, L.W. Zhou  

E-print Network

, such as electrorheological (ER) fluids, fer- rofluids, magnetorheological fluids, and electro-magneto- rheological fluidsStructure of polydisperse electrorheological fluids: Experiment and theory M. Shen, J.G. Cao, H (ER) fluids are often determined by the spatial arrangement of the suspended particles. We investigate

Huang, Ji-Ping

171

A Cost-Effective LSH Filter for Fast Pairwise Mining Gang Zhao, Yun Xiong, Longbing Cao, Dan Luo, Xuchun Su and Yangyong Zhu  

E-print Network

A Cost-Effective LSH Filter for Fast Pairwise Mining Gang Zhao, Yun Xiong, Longbing Cao, Dan Luo LSH- based method, namely Cost-effective LSH filter (Ce-LSH for short), for pairwise mining. Compared with previous LSH-type methods, it uses a lower fixed number of LSH functions and is thus more cost-effective

Cao, Longbing

172

Detection and Prediction of Adverse and Anomalous Events in Medical Robots Kai Liang, Feng Cao, Zhuofu Bai, Mark Renfrew, M. Cenk C avusoglu, Andy Podgurski, Soumya Ray  

E-print Network

Detection and Prediction of Adverse and Anomalous Events in Medical Robots Kai Liang, Feng Cao, zxb31, mark.renfrew, mcc14, podgurski, sray}@case.edu Abstract Adverse and anomalous (A&A) events Intelligence (www.aaai.org). All rights reserved. event reports filed by manufacturers with the Food and Drug

Cavusoglu, Cenk

173

Growth of Thin InAlP Native Oxides for GaAs Metal-Oxide-Semiconductor Devices Mr. Ying Cao1  

E-print Network

Growth of Thin InAlP Native Oxides for GaAs Metal-Oxide-Semiconductor Devices Mr. Ying Cao1 ; Ms thermal native oxides towards thicknesses suitable for use in GaAs metal-oxide-semiconductor (MOS) devices, we observed that thin 7 nm oxide films showed Schottky-diode-like behavior with relatively large

174

FOURIER TRANSFORM INFRARED PHOTOACOUSTIC SPECTROSCOPY CHARACTERIZATION OF SULFUR-OXYGEN SPECIES RESULTING FROM THE REACTION OF SO2 WITH CAO AND CACO3  

EPA Science Inventory

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) has been used to investigate the reaction of SO2 in He with CaO and CaCO3 particles at temperatures between 25 and 900 C. SO2 reacts with CaC at 25 C, while the reaction of Ca-CO3 with SO2 is first evident at 550 C ...

175

Long lasting blue phosphorescence and photostimulated luminescence in 12CaO?7Al2O3:Eu thin films grown by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Long lasting blue emitting Eu-doped 12CaO?7Al2O3 thin films have been prepared on quartz substrates by pulsed laser deposition combined with post-annealing. The 12CaO?7Al2O3 phase is formed after annealing the films above 900 °C in vacuum ambient. Upon 323 nm excitation, the thin films exhibit a blue long lasting emission peaked at 444 nm, assigned to the 5d-4f transitions of Eu2+. The films annealed at 950 °C have stronger luminescence and longer lasting time than that annealed at 900 °C. The phosphorescence intensity of vacuum annealed film is better than that annealed in H2/N2 atmosphere, which might be due to the increase of shallow trap numbers during the vacuum annealing process. Thermoluminescence curves demonstrate that vacuum and H2/N2 atmosphere annealing could introduce a large number of both shallow and deep traps into 12CaO?7Al2O3:Eu thin films. After UV irradiation, excellent photostimulated luminescence can be observed under 980 nm excitation. Our results suggest that 12CaO?7Al2O3:Eu phosphor may serve as a promising blue luminescent materials used in fabrication of optical storage and illumination in dark environments.

Zhu, Hancheng; Liu, Yuxue; Yan, Duanting; Bian, Hongyu; Li, Shengnan; Liu, Chunguang; Xu, Changshan; Wang, Xiaojun

2014-09-01

176

Shape transition of unstrained flattest single-walled carbon nanotubes under pressure Weihua Mu, Jianshu Cao, and Zhong-can Ou-Yang  

E-print Network

Shape transition of unstrained flattest single-walled carbon nanotubes under pressure Weihua Mu single-walled carbon nanotubes under pressure Weihua Mu,1,2,3,a) Jianshu Cao,1,4,b) and Zhong-can Ou section of a single walled carbon nanotube successively deforms from the original round shape to oval

Cao, Jianshu

177

Hydrogen-rich gas production via CaO sorption-enhanced steam gasification of rice husk: a modelling study.  

PubMed

Gasification is a thermochemical process in which solid or liquid fuels are transformed into synthesis gas through partial oxidation. In this paper, a kinetic model of rice husk gasification has been developed, which is interesting for the applications of the syngas produced. It is a zero-dimensional, steady-state model based on global reaction kinetic, empirical correlation of pyrolysis and is capable of predicting hydrogen yield in the presence of sorbent CaO. The model can also be used as a useful tool to investigate the influence of process parameters including steam/biomass ratio, CaO/fuel ratio (CaO/Fuel), and gasification temperature on hydrogen efficiency, CO2 capture ratio (CCR), and average carbonation conversion (Save). Similar to hydrogen formation, CCR also increases with increasing CaO/Fuel, but an opposite trend is exhibited in Save. Model predictions were compared with available data from the literature, which showed fairly good agreement. PMID:25403373

Beheshti, Sayyed Mohsen; Ghassemi, Hojat; Shahsavan-Markadeh, Rasoul; Fremaux, Sylvain

2014-12-01

178

Environmental controls on plant chemical traits: Using the CAO-VSWIR to characterize patterns in a mediterranean-type ecosystem  

NASA Astrophysics Data System (ADS)

Here we present results from a new imaging spectrometer, the Carnegie Airborne Observatory's (CAO) Visible-Short Wave Infrared (VSWIR) sensor, and we use these data to map key plant functional traits in a semi-arid ecosystem, Jasper Ridge Biological Preserve (Woodside, CA USA). We considered four fundamental plant traits: leaf nitrogen per mass (Nmass, %), leaf carbon per mass (Cmass, %), leaf water fraction (WL), and canopy water fraction (WC).With these maps we ask the following questions: (1) How do these traits vary with environmental gradients and land use history, independent of species composition? (2) Does information about plant community improve our ability to explain trait patterns? And (3) what does the variation within plant communities tell us about the underlying processes driving or limiting this ecosystem? We show that the new CAO-VSWIR combined with partial least squares regression can effectively map these four plant chemical traits across multiple plant functional types (observed v. predicted R2s ranging from 0.55 for WL to 0.84 for Cmass). To consider how these traits varied with environmental gradients we used simultaneous autoregressive modeling and found, in general, that environment and land-use history together explained about a quarter of the variation in each trait, but that information about plant community boundaries dramatically improved our predictive power. While 29 - 44% of the variation in these four traits remained unexplained, when we considered the trait distributions within each plant community we found that most plant communities were sharply peaked (leptokurtic) or near normal, while a few communities were more evenly distributed (platykurtic) for each trait. These results show that, even though environmental gradients play a small but significant role, most of the plant communities at Jasper Ridge are characterized by a narrow range of trait patterns. For the few communities that are highly divergent, possible causal factors include resource limitation, competition, and/or past disturbances.

Dahlin, K.; Asner, G. P.; Field, C. B.

2012-12-01

179

A Systematic Review of the Mysterious Caterpillar Fungus Ophiocordyceps sinensis in Dong-ChongXiaCao (???? D?ng Chóng Xià C?o) and Related Bioactive Ingredients  

PubMed Central

The caterpillar fungus Ophiocordyceps sinensis (syn.† Cordyceps sinensis), which was originally used in traditional Tibetan and Chinese medicine, is called either “yartsa gunbu” or “DongChongXiaCao (???? D?ng Chóng Xià C?o)” (“winter worm-summer grass”), respectively. The extremely high price of DongChongXiaCao, approximately USD $20,000 to 40,000 per kg, has led to it being regarded as “soft gold” in China. The multi-fungi hypothesis has been proposed for DongChongXiaCao; however, Hirsutella sinensis is the anamorph of O. sinensis. In Chinese, the meaning of “DongChongXiaCao” is different for O. sinensis, Cordyceps spp.,‡ and Cordyceps spƒ. Over 30 bioactivities, such as immunomodulatory, antitumor, anti-inflammatory, and antioxidant activities, have been reported for wild DongChongXiaCao and for the mycelia and culture supernatants of O. sinensis. These bioactivities derive from over 20 bioactive ingredients, mainly extracellular polysaccharides, intracellular polysaccharides, cordycepin, adenosine, mannitol, and sterols. Other bioactive components have been found as well, including two peptides (cordymin and myriocin), melanin, lovastatin, ?-aminobutyric acid, and cordysinins. Recently, the bioactivities of O. sinensis were described, and they include antiarteriosclerosis, antidepression, and antiosteoporosis activities, photoprotection, prevention and treatment of bowel injury, promotion of endurance capacity, and learning-memory improvement. H. sinensis has the ability to accelerate leukocyte recovery, stimulate lymphocyte proliferation, antidiabetes, and improve kidney injury. Starting January 1st, 2013, regulation will dictate that one fungus can only have one name, which will end the system of using separate names for anamorphs. The anamorph name “H. sinensis” has changed by the International Code of Nomenclature for algae, fungi, and plants to O. sinensis. PMID:24716152

Lo, Hui-Chen; Hsieh, Chienyan; Lin, Fang-Yi; Hsu, Tai-Hao

2013-01-01

180

X-ray fluorescence analysis with micro glass beads using milligram-scale siliceous samples for archeology and geochemistry  

NASA Astrophysics Data System (ADS)

A micro glass bead technique was developed to assay precious siliceous samples for geochemical and archeological analyses. The micro-sized (approximately 3.5 mm in diameter and 0.8 mm in height) glass beads were prepared by mixing and fusing 1.1 mg of the powdered sample and 11.0 mg of the alkali lithium tetraborate flux for wavelength-dispersive X-ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). The preparation parameters, including temperature and agitation during the fusing process, were optimized for the use of a commercial platinum crucible rather than a custom-made crucible. The procedure allows preparation of minute sample amounts of siliceous samples using conventional fusing equipment. Synthetic calibration standards were prepared by compounding chemical reagents such as oxides, carbonates, and diphosphates. Calibration curves showed good linearity with r values > 0.997, and the lower limits of detection were in the 10s to 100s of ?g g- 1 range (e.g., 140 ?g g- 1 for Na2O, 31 ?g g- 1 for Al2O3, and 8.9 ?g g- 1 for MnO). Using the present method, we determined ten major oxides in igneous rocks, stream sediments, ancient potteries, and obsidian. This was applicable to siliceous samples with various compositions, because of the excellent agreement between the analytical and recommended values of six geochemical references. This minimal-scale analysis may be available for precious and limited siliceous samples (e.g., rock, sand, soil, sediment, clay, and archeological ceramics) in many fields such as archeology and geochemistry.

Ichikawa, Shintaro; Nakamura, Toshihiro

2014-06-01

181

High-Mg# andesitic lavas of the Shisheisky Complex, Northern Kamchatka: implications for primitive calc-alkaline magmatism  

NASA Astrophysics Data System (ADS)

Primitive arc magmatism and mantle wedge processes are investigated through a petrologic and geochemical study of high-Mg# (Mg/Mg + Fe > 0.65) basalts, basaltic andesites and andesites from the Kurile-Kamchatka subduction system. Primitive andesitic samples are from the Shisheisky Complex, a field of Quaternary-age, monogenetic cones located in the Aleutian-Kamchatka junction, north of Shiveluch Volcano, the northernmost active composite volcano in Kamchatka. The Shisheisky lavas have Mg# of 0.66-0.73 at intermediate SiO2 (54-58 wt%) with low CaO (<8.8%), CaO/Al2O3 (<0.54), and relatively high Na2O (>3.0 wt%) and K2O (>1.0 wt%). Olivine phenocryst core compositions of Fo90 appear to be in equilibrium with whole-rock `melts', consistent with the sparsely phyric nature of the lavas. Compared to the Shisheisky andesites, primitive basalts from the region (Kuriles, Tolbachik, Kharchinsky) have higher CaO (>9.9 wt%) and CaO/Al2O3 (>0.60), and lower whole-rock Na2O (<2.7 wt%) and K2O (<1.1 wt%) at similar Mg# (0.66-0.70). Olivine phenocrysts in basalts have in general, higher CaO and Mn/Fe and lower Ni and Ni/Mg at Fo88 compared to the andesites. The absence of plagioclase phenocrysts from the primitive andesitic lavas contrasts the plagioclase-phyric basalts, indicating relatively high pre-eruptive water contents for the primitive andesitic magmas compared to basalts. Estimated temperature and water contents for primitive basaltic andesites and andesites are 984-1,143°C and 4-7 wt% H2O. For primitive basalts they are 1,149-1,227°C and 2 wt% H2O. Petrographic and mineral compositions suggest that the primitive andesitic lavas were liquids in equilibrium with mantle peridotite and were not produced by mixing between basalts and felsic crustal melts, contamination by xenocrystic olivine, or crystal fractionation of basalt. Key geochemical features of the Shisheisky primitive lavas (high Ni/MgO, Na2O, Ni/Yb and Mg# at intermediate SiO2) combined with the location of the volcanic field above the edge of the subducting Pacific Plate support a genetic model that involves melting of eclogite or pyroxenite at or near the surface of the subducting plate, followed by interaction of that melt with hotter peridotite in the over-lying mantle wedge. The strongly calc-alkaline igneous series at Shiveluch Volcano is interpreted to result from the emplacement and evolution of primitive andesitic magmas similar to those that are present in nearby monogenetic cones of the Shisheisky Complex.

Bryant, J. A.; Yogodzinski, G. M.; Churikova, T. G.

2011-05-01

182

The Vibrational Frequencies of CaO2, ScO2, and TiO2: A Comparison of Theoretical Methods  

NASA Technical Reports Server (NTRS)

The vibrational frequencies of several states of CaO2, ScO2, and TiO2 are computed at using density functional theory (DFT), the Hatree-Fock approach, second order Moller-Plesset perturbation theory (MP2), and the complete-active-space self-consistent-field theory. Three different functionals are used in the DFT calculations, including two hybrid functionals. The coupled cluster singles and doubles approach including the effect of unlinked triples, determined using perturbation theory, is applied to selected states. The Becke-Perdew 86 functional appears to be the cost effective method of choice, although even this functional does not perform well for one state of CaO2. The MP2 approach is significantly inferior to the DFT approaches.

Rosi, Marzio; Bauschlicher, Charles W., Jr.; Chertihin, George V.; Andrews, Lester; Arnold, James O. (Technical Monitor)

1997-01-01

183

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

184

The effect of Al2O3, CaO, Cr2O3 and MgO on devitrification of silica  

NASA Technical Reports Server (NTRS)

The effect of doping on devitrification of vitreous silica was studied at 1100, 1200, and 1300 C. Dispersion of dopants on a molecular scale was accomplished via a sol-gel technique. All dopants accelerated the devitrification of silica but to different degrees. The most active was CaO followed by MgO, Al2O3, and Cr2O3. Pure silica and silica containing Cr2O3 and Al2O3 devitrified to alpha-cristobalite only, whereas silica doped with CaO and MgO produced alpha-quartz and alpha-cristobalite. It appears that prolonged heat treatment would cause alpha-quartz to transform to alpha-cristobalite.

Zaplatynsky, Isidor

1988-01-01

185

Preparation of CaO as OLED getter material through control of crystal growth of CaCO{sub 3} by block copolymers in aqueous solution  

SciTech Connect

As the starting materials of organic light-emitting diode (OLED) getter, calcium carbonate (CaCO{sub 3}) particles with various shapes and crystal structures have been successfully prepared with additives (L64 or PEGPG), which contain blocks of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO). These CaCO{sub 3} particles were calcinated into highly crystalline calcium oxide (CaO) nanoparticles with high capacity of water adsorption up to 14.23 wt.%. The CaCO{sub 3} and CaO particles prepared at various conditions were characterized using the field emission scanning electron microscopy (FE-SEM), Fourier transform infrared microscopy (FT-IR), X-ray powder diffraction (XRD), and dynamic vapor sorption (DVS) method.

Park, Jae-Hyung [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Oh, Seong-Geun [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)], E-mail: seongoh@hanyang.ac.kr

2009-01-08

186

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

187

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

188

Biomass gasification with steam in fluidized bed: Effectiveness of CaO, MgO, and CaO-MgO for hot raw gas cleaning  

Microsoft Academic Search

The upgrading of the raw hot gas from a bubbling fluidized bed biomass gasifier is studied using cheap calcined minerals or rocks downstream from the gasifier. Biomass gasification is made with steam (not air) at 750--780 C and about 0.5--1.0 kg of biomass\\/h. Calcined solids used are dolomite (MgO-CaO), pure calcite (CaO), and pure magnesite (MgO). Variables studied have been

Jesús Delgado; María P. Aznar; José Corella

1997-01-01

189

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

190

Geological control of canopy structure and function in Panamanian forests as identified by CAO-AToMS  

NASA Astrophysics Data System (ADS)

Geological formations and their edaphic properties are known to control plant species composition in tropical forests. It has been speculated that these edaphic and compositional patterns might also be translated into functional patterns, but this has been difficult to test due to a lack of broad-scale but detailed canopy structural and functional data. Here we use the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS), which combines a 480-band visible-to-shortwave imaging spectrometer (VSWIR) with dual waveform LiDAR, to generate ultra-high resolution data on geomorphology, canopy structure, and canopy chemistry for forests in the vicinity of the Panama Canal. Using these remotely-sensed data, in conjunction with field data on soils and plant species composition, we demonstrate that geological formations regulate forest structure and chemistry in these forests via changes in soils and plant species composition. These chemical properties, moreover, correspond to canopy functional properties including photosynthetic investment and anti-herbivore defenses. Together, our findings indicate that forest canopy structure and function in these forests are an expression their geological history, over which variations due to contemporary variables such as climate are overlaid.

Higgins, M.; Asner, G. P.; Martin, R. E.; Knapp, D. E.

2012-12-01

191

Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites  

NASA Astrophysics Data System (ADS)

We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10-? (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized them by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties, such as real and imaginary parts of the dielectric constant, dielectric loss, and ac-conductivity of these composites were studied by capacitance and conductance measurements as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). X-ray diffraction analysis reveals that the characteristic behavior of the superconductor phase and the structure of Cu0.5Tl0.5Ba2Ca2Cu3O10-? are nearly undisturbed by doping with nanoparticles. Scanning electron microscopy images show the improvement in the intergranular linking between the superconducting grains occurring with increasing nanoparticle concentration. Microcracks are healed up with these nanoparticles, and superconducting volume fraction is also increased. Dielectric properties of these composites strongly depend on the frequency and temperature. Zero resistivity critical temperature and dielectric properties show opposite trends with the addition of nanoparticles to the Cu0.5Tl0.5Ba2Ca2Cu3O10-? superconductor matrix.

Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Tajammul Hussain, S.; Kamran, M.

2013-07-01

192

From insulator to electride: a theoretical model of nanoporous oxide 12CaO.7Al2O3.  

PubMed

Recently, a novel inorganic electride stable at room temperatures has been obtained by reducing a complex nanoporous oxide 12CaO.7Al2O3 (C12A7) in a Ca atmosphere (Matsuishi, S.; Toda, Y.; Miyakawa, M.; Hayashi, K.; Kamiya, T.; Hirano, M.; Tanaka, I.; Hosono, H. Science 2003, 301, 626). In this system, up to 2.3 x 1021/cm3 electrons can be accommodated in a three-dimensional network of cages formed by a positively charged oxide framework. We demonstrate theoretically that at all concentrations, ne, the electrons are neither associated with specific atoms nor fully delocalized. At low ne, the electrons are isolated from each other and resemble the color centers in insulating materials. They are well localized in some of the lattice cages and yield strong inhomogeneous lattice distortions that provide polaron-type cage-to-cage electron hopping. As ne increases, the electrons form a denser electron gas and become more evenly spread over all available lattice cages. At sufficiently high ne, the system becomes metallic but still retains partially localized character of the conducting electrons. We describe the nature of the electronic states at the Fermi level and predict the changes in the optical and magnetic properties of this system as a function of ne. PMID:17243831

Sushko, Peter V; Shluger, Alexander L; Hirano, Masahiro; Hosono, Hideo

2007-01-31

193

The mechanical properties and bioactivity of poly(methyl methacrylate)/SiO(2)-CaO nanocomposite.  

PubMed

The mechanical properties and bioactivity of poly(methyl methacrylate)/SiO(2)-CaO nanocomposite were investigated using dimethyldiethoxysilane (DMDES) and tetraethoxysilane (TEOS), which could produce two and four siloxane linkages, respectively, after a sol-gel reaction. Methyl methacrylate was co-polymerized with 3-(trimethoxysilyl)propyl methacrylate and then co-condensed with DMDES (specimen D) and TEOS (specimen T), respectively, with calcium nitrate tetrahydrate under acidic conditions. The fracture toughness of specimen D was much improved compared to that of specimen T, whereas its fracture strength, hardness, and apatite-forming ability in simulated body fluid (SBF) were slightly decreased. The improved fracture toughness of specimen D without losing apatite-forming ability was explained by the decrease of siloxane linkage numbers and the introduction of alkyl groups in silica structure because covalently bonded siloxane linkages produce hard and brittle fracture behavior in the nanocomposite while the alkyl groups help to make the silica as linear chain structure. The practical implication of these results is that this new nanocomposite can be applied to the filler materials for bone cement and dental composite resin because of its good bioactivity and improved mechanical properties. PMID:19304322

Lee, Kyu-Hyeon; Rhee, Sang-Hoon

2009-07-01

194

Cl 2 adsorption on supported alkali metals and on the MgO and CaO (001) supports: A DFT study  

NASA Astrophysics Data System (ADS)

The adsorption properties of Cl 2 molecules adsorbed on Li and Na atoms supported on various sites of MgO and CaO (100) surfaces have been examined at the DFT/B3LYP level of theory using the embedded cluster model. By comparison, the adsorption on the clean surfaces of the support has been investigated. Our calculations predict weakening of the Cl 2 bond due to the presence of the alkali metals, reflected by an elongation of the Cl 2 bond by 0.64 Å. Although the regular and defective sites are stronger binding sites in CaO (001) than in MgO (001), the interaction energy decreases as the atomic number of alkali atoms (Li and Na) increases. Metal atoms bind more strongly on the defect sites. The MgO and CaO (001) surfaces not only serve as the supports of Li and Na atoms but also participate in the interaction with Cl 2 molecule. Charge transfer takes place from the oxide surface to the adsorbed metal.

Abdel Aal, S.; Abdel Halim, W. S.; Shalabi, A. S.

2008-12-01

195

PII S0016-7037(02)01083-9 Iron oxidation state of a 2.45-Byr-old paleosol developed on mafic volcanics  

E-print Network

(Holland and Rye, 1997; Rye and Holland, 1998). The evalu- ation is mainly based on Fe retentionO, Na2O, K2O, and MnO) (Rye and Holland, 1998). Maximum PCO2 is necessary to obtain maximum PO2 in this equation. For instance, Rye et al., (1995) calculated the maximum PO2

Utsunomiya, Satoshi

196

Evidence from high-Ni olivines for a hybridized peridotite/ pyroxenite source for orogenic andesites from the central  

E-print Network

andesites from the central Mexican Volcanic Belt Susanne M. Straub and Alexandra B. LaGatta Lamont Doherty-alkaline andesite melts that combine the high SiO2, Na2O, and K2O abundances of the differentiated continental crust andesites and andesites of the central Mexican Volcanic Belt suggest that this dichotomy reflects

Langmuir, Charles H.

197

Petrogenesis of selected A-type granitic intrusions from Central Eastern Desert of Egypt  

NASA Astrophysics Data System (ADS)

The Pan-African orogeny in the Arabian-Nubian Shield was terminated by intrusion of A-type granites (~ 595 Ma; Greenberg, 1981) and its volcanic equivalents. Subsequent to the intrusions of these granitic bodies the shield was exhumed. Eroded A-type granite pebbles were found in the molasse sediments that were deposited in intermountain basins. Therefore the A-type granites provide information about the last stage of the Pan-African geochemical system. Preliminary whole-rock geochemical data of three granitic intrusions (Kadabora, Um Naggat and El shiekh Salem) from the Central Eastern Desert of Egypt; indicate that all of them are peraluminous and with A-type characteristics. These intrusions show low CaO content (average 0.43 %wt), high FeOT/MgO ratio (10.46-121.88), high Na2O+K2O (average 8.04 %wt), marked enrichment of high field strength elements (Y, Nb and Ga except Zr), depletion in MgO (0.01-0.11 %wt) and with low concentration of Sr and Ba. The studied granitoids were emplaced in within plate tectonic regime. References: Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Bull. Geol. Soc. Am. Part 1, v.92: 224-232.

Hassan, Tharwat; Asran, Asran; Amron, Taha; Hauzenberger, Christoph

2014-05-01

198

Fluid circulation, progressive deformation and mass-transfer processes in the upper crust: the example of basement-cover relationships in the External Crystalline Massifs, Switzerland  

NASA Astrophysics Data System (ADS)

Basement and cover rocks of the external zone in the Swiss Alps are affected by Tertiary ductile deformation under greenschist facies conditions (300-450°C; 3-4.5 kbar). The analyses of stable isotope systematics of veins and shear zones, as well as variation profiles of chemical elements across major shear zones, distinguish two types of fluid-rock interactions. (i) Closed systems: most syntectonic veins within the Helvetic carbonate cover have ? 18O compositions depending on the adjacent wall rock compositions and varying with respect to the initial chemical heterogeneity of each sedimentary layer. Within the granitic basement, chemical profiles across minor granite shear zones show equal volume gains and losses for each oxide Na 2O or K 2O. (ii) Open systems: variation profiles in major cover thrusts show a variable increase of 87Sr/ 86Sr ratios combined with a strong decrease in ? 18O approaching an isotopic equilibrium with the basement rocks. Within the major basement shear zones, decrease in CaO and increase in MgO content are observed with progressive deformation increase. A two-step tectonic and geochemical model is proposed to explain the coexistence of open and closed systems. Fluid sources and transport mechanisms of chemical elements are discussed.

Marquer, D.; Burkhard, M.

1992-09-01

199

The Oro Grande, New Mexico, chondrite and its lithic inclusion.  

NASA Technical Reports Server (NTRS)

The Oro Grande, New Mexico, U.S.A., chondrite was found in 1971. Electron microprobe analyses and microscopic examination show the following mineralogy: olivine (Fa 19.3 mole %), orthopyroxene (Fs 16.2 mole %), diopside, feldspar (An 13.6 mole %), chlorapatite, whitlockite, kamacite, taenite, troilite, chromite, and an iron-bearing terrestrial weathering product. A bulk chemical analysis of the meteorite shows the following results (weight %): Fe 0.84, Ni 1.46, Co 0.07, FeS 3.62, SiO2 34.18, TiO2 0.14, Al2O3 1.83, Cr2O3 0.55, Fe2O3 21.25, FeO 9.13, MnO 0.31, MgO 21.52, CaO 1.72, Na2O 0.70, K2O 0.08, P2O5 0.25, H2O(+) 2.14, H2O(-) 0.40, C 0.22, sum 100.41. On the basis of composition and texture the Oro Grande meteorite is classified as an H5 chondrite.

Fodor, R. V.; Keil, K.; Jarosewich, E.

1972-01-01

200

Mineralogical and chemical compositions of the paleosols of different ages buried under kurgans in the southern Ergeni region and their paleoclimatic interpretation  

NASA Astrophysics Data System (ADS)

The chemical and mineralogical compositions and the contents and properties of the organic matter were studied in the paleosols of different ages buried under the kurgan group "Kalmykia" in the southern part of the Ergeni Upland. The investigated sequence of soils included profiles developed on the given territory about 5100, 4410, 4260, 4120, 3960, and 600 yrs ago. The background light chestnut soil was also examined. The results of our study showed that the earlier established climate changes in this area during the second half of the Holocene are reflected in the chemical and mineralogical compositions of the soils. These characteristics can be used as indicators of the paleoclimatic conditions together with some petrophysical characteristics, such as the magnetic susceptibility of the soil samples. The study of the mineralogical composition of the clay fraction of the paleosols attests to the transformation of the smectitic phase, accumulation of illites, and destruction of chlorites manifested at different degrees. It is argued that the geochemical indices—CIA, Al2O3/(CaO + MgO + K2O + Na2O), Rb/Sr, and Ba/Sr—are sensitive to climate changes and reflect the transformation of the mineral soil mass and the soil genesis.

Tatyanchenko, T. V.; Alekseeva, T. V.; Kalinin, P. I.

2013-04-01

201

Reactions of yttria-stabilized zirconia with oxides and sulfates of various elements  

NASA Technical Reports Server (NTRS)

The reactions between partially stabilized zirconia, containing 8 weight-percent yttria, and oxides and sulfates of various elements were studied at 1200, 1300, and 1400 C for times to 800, 400, and 200 hours, respectively. These oxides and sulfates represent impurities and additives potentially present in gas turbine fuels or impurities in the turbine combustion air as well as the elements of the substrate alloys in contact with zirconia. Based on the results, these compounds can be classified in four groups: (1) compounds which did not react with zirconia (Na2SO4, K2SO4, Cr2O3, Al2O3 and NiO); (2) compounds that reached completely with both zirconia phases (CaO, BaO, and BaSO4); (3) compounds that reacted preferentially with monoclinic zirconia (Na2O, K2O, CoO, Fe2O3, MgO, SiO2, and ZnO); and (4) compounds that reacted preferentially with cubic zirconia (V2O5, P2O5).

Zaplatynsky, I.

1978-01-01

202

Calculation of Oxygen Fugacity in High Pressure Metal-Silicate Experiments and Comparison to Standard Approaches  

NASA Technical Reports Server (NTRS)

Calculation of oxygen fugacity in high pressure and temperature experiments in metal-silicate systems is usually approximated by the ratio of Fe in the metal and FeO in the silicate melt: (Delta)IW=2*log(X(sub Fe)/X(sub FeO)), where IW is the iron-wustite reference oxygen buffer. Although this is a quick and easy calculation to make, it has been applied to a huge variety of metallic (Fe- Ni-S-C-O-Si systems) and silicate liquids (SiO2, Al2O3, TiO2, FeO, MgO, CaO, Na2O, K2O systems). This approach has surely led to values that have little meaning, yet are applied with great confidence, for example, to a terrestrial mantle at "IW-2". Although fO2 can be circumvented in some cases by consideration of Fe-M distribution coefficient, these do not eliminate the effects of alloy or silicate liquid compositional variation, or the specific chemical effects of S in the silicate liquid, for example. In order to address the issue of what the actual value of fO2 is in any given experiment, we have calculated fO2 from the equilibria 2Fe (metal) + SiO2 (liq) + O2 = Fe2SiO4 (liq).

Righter, K.; Ghiorso, M.

2009-01-01

203

Heavy metal contamination of the Sacca di Goro lagoon area (Po River Delta, Northern Italy)  

NASA Astrophysics Data System (ADS)

The lagoon area of the Sacca di Goro, within the Po River delta, is ca. 20 km2 wide, with a mean depth of 1.5 m and a mean salinity of 29%o. It holds a major naturalistic interest as well as an economic one due to the aquaculture activities (mussels and clams). In this lagoon system, the quality of the sea-bottom sediments is crucial not only for the cultivated species, but also for the potential bio-accumulation problems in heavy metals. The definition of the qualitative status of the lagoon sediments is crucial for adopting the best management strategies and the protection of the environmental conditions. We determined the concentration in SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, CaO, Na2O, K2O, P2O5, Ba, Ce, Co, Cr, La, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Cu, Ga, Nd, S and Sr, of 31 samples homogeneously collected over the lagoon area. This large dataset allowed i) to define the environmental quality of the sediments, ii) to recognise the areas with the higher contamination risk; and iii) to emphasise the local occurrence of polluting phenomena associated to chromium, nickel, vanadium, cobalt, lead, zinc and copper.

Rapti-Caputo, Dimitra

2010-05-01

204

Biodegradable borosilicate bioactive glass scaffolds with a trabecular microstructure for bone repair.  

PubMed

Three-dimensional porous scaffolds of a borosilicate bioactive glass (designated 13-93B1), with the composition 6Na2O-8K2O-8MgO-22CaO-18B2O3-36SiO2-2P2O5 (mol%), were prepared using a foam replication technique and evaluated in vitro and in vivo. Immersion of the scaffolds for 30 days in a simulated body fluid in vitro resulted in partial conversion of the glass to a porous hydroxyapatite composed of fine needle-like particles. The capacity of the scaffolds to support bone formation in vivo was evaluated in non-critical sized defects created in the femoral head of rabbits. Eight weeks post-implantation, the scaffolds were partially converted to hydroxyapatite, and they were well integrated with newly-formed bone. When loaded with platelet-rich plasma (PRP), the scaffolds supported bone regeneration in segmental defects in the diaphysis of rabbit radii. The results indicate that these 13-93B1 scaffolds, loaded with PRP or without PRP, are beneficial for bone repair due to their biocompatibility, conversion to hydroxyapatite, and in vivo bone regenerative properties. PMID:24433915

Gu, Yifei; Wang, Gang; Zhang, Xin; Zhang, Yadong; Zhang, Changqing; Liu, Xin; Rahaman, Mohamed N; Huang, Wenhai; Pan, Haobo

2014-03-01

205

Non-crystalline composite tissue engineering scaffolds using boron-containing bioactive glass and poly(D,L-lactic acid) coatings.  

PubMed

The aim of this study was the fabrication of three-dimensional, highly porous, bioactive scaffolds using a recently developed bioactive glass powder, denominated '0106', with nominal composition (in wt%): 50 SiO(2), 22.6 CaO, 5.9 Na(2)O, 4 P(2)O(5), 12 K(2)O, 5.3 MgO and 0.2 B(2)O(3). The optimum sintering conditions for the fabrication of scaffolds by the foam-replica method were identified (sintering temperature: 670 degrees C and dwell time: 5 h). Composite samples were also fabricated by applying a biopolymer coating of poly((D,L)-lactic acid) (PDLLA) using a dip coating process. The average compressive strength values were 0.4 MPa for uncoated and 0.6 MPa for coated scaffolds. In vitro bioactivity studies in simulated body fluid (SBF) showed that a carbonate hydroxyapatite (HCAp) layer was deposited on uncoated and coated scaffolds after only 4 days of immersion in SBF, demonstrating the high in vitro bioactivity of the scaffolds. It was also confirmed that the scaffold structure remained amorphous (no crystallization) after the specific heat treatment used, with scaffolds exhibiting mechanical properties and bioactivity suitable for use in bone tissue engineering applications. PMID:19776493

Mantsos, T; Chatzistavrou, X; Roether, J A; Hupa, L; Arstila, H; Boccaccini, A R

2009-10-01

206

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

2010-02-01

207

New data on selected Ivory Coast tektites  

USGS Publications Warehouse

Fourteen Ivory Coast tektites exhibit a range of bulk indices of refraction of 1.5156 to 1.5217 ?? 0.0004 and of bulk specific gravities of 2.428 to 2.502 ??0.005. Seven of these Ivory Coast (IVC) tektites were analyzed for major and minor element content. Compared to tektites from other strewn fields, their SiO2 content is low (67.2-69.1 %), A12O3 relatively high (15.8-16.8 %), and total iron relatively high but with a more restricted range (6.3-6.8 % as FeO). Their lime content is low (0.71-1.35%) compared to Australasian tektites but their MgO CaO ratio (about 3.1) is unusually high. All other tektite groups have Na2O K2O ratios less than unity, but the Na2O K2O ratio of the IVC tektites is slightly greater than unity. Their K Rb ratios range from 200 to 256 and average 227, which is higher than those determined for Australasian tektites, but similar to some obtained for moldavites. The Li content (41-48 ppm) is about the same as that of the Australasian tektites, but the Cs and Rb are lower, being 1.9 to 2.9 and 57 to 86 ppm, respectively. The IVC tektites are high in Cr (260-375 ppm), Co (19-25 ppm) and Ni (101-167 ppm), and particularly in Pb (<10-18 ppm), Cu (13-21 ppm) and Ga (14-23 ppm). The high Cr Ni ratios of the IVC tektites (range 2-3.6) are similar to those found for australites, philippinites and thailandites, but not the javanites and indochinites. Evaluation of these and other reported data show that compositional similarities between the IVC tektites and green or black Bosumtwi Crater glasses strongly support the hypothesis of a common impact origin-i.e. the Bosumtwi Crater site. Comparison of the IVC tektite composition with those of returned lunar materials (gabbros, basalts, breccia and soils) do not support a lunar origin for the Ivory Coast tektites. ?? 1972.

Cuttitta, F.; Carron, M.K.; Annell, C.S.

1972-01-01

208

[Influence of cations on the laser Raman spectra of silicate glasses].  

PubMed

Na2O(K2O)-CaO(MgO)-SiO2, Na2O(K2O)-Al2O3-SiO2, Na2O(K2O)-B2O3-SiO2, Na2O(K2O)-PbO-SiO2 and PbO-BaO-SiO2 glass systems were investigated using laser Raman spectroscopic technique. The modification of short-range structure of glass caused by network modifier cations will influence Raman signature. Alkali and alkali-earth ions can weaken the bridging oxygen bond, thus lower the frequency of Si-O(b)-Si anti-symmetric stretching vibration. When coordina ted by oxygen ions, B3+ can form [BO4] tetrahedron and enter the silicon-oxygen network, but this effect had little impact on the frequency of Raman peaks located in the high-frequency region. Al3+ can also be coordinated by oxygen ions to form [AlO4] tetrahedron. [AlO4] will increase the disorder degree of network while entering network. Ba2+ can increase the density of electron cloud along the Si-O(nb) bond when it bonds with non-bridging oxygen, which will lead to a higher peak intensity of O-Si-O stretching vibration. The Raman peaks of alkli- and alkali-earth silicate glasses are mainly distributed in the region of 400 - 1 200 cm(-1), while in the spectrum of Na2O(K2O)-PbO-SiO2 glass system a 131 cm(-1) peak existed. The authors assigned it to the Pb-O symmetric stretching vibration. Some of the samples were produced in the laboratory according to the average compositions of ancient glasses, so this research is very significant to discriminating ancient silicate glasses of different systems by Laser Raman spectroscopic technique. PMID:22715771

Xiong, Yi; Zhao, Hong-xia; Gan, Fu-xi

2012-04-01

209

Nanostructural features and optical properties of Na 2O-P 2O 5-AgCl thin films  

NASA Astrophysics Data System (ADS)

Sodium phosphate glass systems with AgCl as dopant (0 and 15 mol%) have been synthesized by melt-quenching technique. The glasses in bulk form were characterized by X-ray diffraction, FT-IR spectroscopy and their thermal and electrical properties were investigated. These glasses were deposited on glass substrates by thermal evaporation method in thin film form and annealed at 600 °C. The influence of deposition in thin film form and annealing on structure and optical properties (transmittance, absorbance and optical gap) have showed that both doped and undoped as-deposited glass films have a porous, granular structure and considerable grain coarsening and densification occur upon annealing at 600 °C. The optical transmittance of the film is found to decrease in visible region as a function of annealing and doping. The annealed 15 mol% doped film shows a prominent absorbance peak at 430 nm, which is ascribed to Ag +(5s) ? O( n) electronic transitions.

Singh, Punita; Deepa, M.; Srivastava, A. K.; Sood, K. N.; Kar, M.

2010-04-01

210

Role of CaO addition in the local order around Erbium in SiO2 ?GeO2 ?P2O5 fiber preforms  

E-print Network

The development of materials for optical signal processing represents a major issue in present technology. In this contribution we present a study on Er-doped fiber preforms where particular attention is devoted on how the addition of CaO in the glass modifies the local environment of the rare earth. The results from photoluminescence and Extended X-ray Absorption Fine Structure (EXAFS) are compared and a clear link between the width of the emission line at 1.5 $\\mu$m and the amorphous/crystalline local structure around the Er3+ ion is evidenced.

D'Acapito, Francesco; Paul, M C; Lee, Thomas Sebastian; Blanc, Wilfried; Dussardier, Bernard; 10.1016/j.mseb.2007.09.079

2009-01-01

211

Cobalt-releasing 1393 bioactive glass-derived scaffolds for bone tissue engineering applications.  

PubMed

Loading biomaterials with angiogenic therapeutics has emerged as a promising approach for developing superior biomaterials for engineering bone constructs. In this context, cobalt-releasing materials are of interest as Co is a known angiogenic agent. In this study, we report on cobalt-releasing three-dimensional (3D) scaffolds based on a silicate bioactive glass. Novel melt-derived "1393" glass (53 wt % SiO2, 6 wt % Na2O, 12 wt % K2O, 5 wt % MgO, 20 wt % CaO, and 4 wt % P2O5) with CoO substituted for CaO was fabricated and was used to produce a 3D porous scaffold by the foam replica technique. Glass structural and thermal properties as well as scaffold macrostructure, compressive strength, acellular bioactivity, and Co release in simulated body fluid (SBF) were investigated. In particular, detailed insights into the physicochemical reactions occurring at the scaffold-fluid interface were derived from advanced micro-particle-induced X-ray emission/Rutherford backscattering spectrometry analysis. CoO is shown to act in a concentration-dependent manner as both a network former and a network modifier. At a concentration of 5 wt % CoO, the glass transition point (Tg) of the glass was reduced because of the replacement of stronger Si-O bonds with Co-O bonds in the glass network. Compressive strengths of >2 MPa were measured for Co-containing 1393-derived scaffolds, which are comparable to values of human spongy bone. SBF studies showed that all glass scaffolds form a calcium phosphate (CaP) layer, and for 1393-1Co and 1393-5Co, CaP layers with incorporated traces of Co were observed. The highest Co concentrations of ?12 ppm were released in SBF after reaction for 21 days, which are known to be within therapeutic ranges reported for Co(2+) ions. PMID:24476347

Hoppe, Alexander; Jokic, Bojan; Janackovic, Djordje; Fey, Tobias; Greil, Peter; Romeis, Stefan; Schmidt, Jochen; Peukert, Wolfgang; Lao, Jonathan; Jallot, Edouard; Boccaccini, Aldo R

2014-02-26

212

Kaishuang Cao SPECIALIST 2  

E-print Network

MANAGER UCPEA VII Deborah McIntosh Administrative Services Laboratory Services Infrastructure Management Information Services LABORATORY SERVICES MANAGER UCPEA VII Karen Lombard LABORATORY TECH 3 UCPEA V MarykeIntosh FACILITIES PROFESSIONAL PROJECT MANAGER UCPEA VII Phil Rusch FACILITIES PROFESSIONAL PROJECT MANAGER UCPEA

Alpay, S. Pamir

213

Kaishuang Cao SPECIALIST 2  

E-print Network

Koehler FISCAL MANAGER UCPEA VII Deborah McIntosh Administrative Services Laboratory Services Services Head, Paul W. Betts Assistant Dean, CLAS ACADEMIC RENOVATIONS PROJECT DIRECTOR UCPEA IX David Infrastructure Management Information Services LABORATORY SUPERVISOR UCPEA VII Karen Lombard LABORATORY TECH 3

Holsinger, Kent

214

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

USGS Publications Warehouse

The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite and kaolinite contents in feed coal. Corundum is a characteristic mineral formed during the combustion of boehmite-rich coal.Samples from the economizer were sieved into six size fractions (<120, 120-160, 160-300, 300-360, 360-500, and >500 mesh) and separated into magnetic, mullite+corundum+quartz (MCQ) and glass phases for mineralogical and chemical analysis. The corundum content increases but amorphous glass decreases with decreasing particle size. Fractions of small particle sizes are relatively high in mullite, probably because mullite was formed from fine clay mineral particles under high-temperature combustion condition. Similarly, fine corundum crystals formed in the boiler from boehmite in feed coal. The magnetic phase consists of hematite, magnetite, magnesioferrite, and MgFeAlO4 crystals. The MCQ phase is composed of 89% mullite, 6.1% corundum, 4.5% quartz, and 0.5% K-feldspar.Overall, the fly ash from the power plant is significantly enriched in Al2O3 with an average of 51.9%, but poor in SiO2, Fe2O3, CaO, MgO, Na2O, P2O5, and As. Arsenic, TiO2, Th, Al2O3, Bi, La, Ga, Ni, and V are high in mullite, and the magnetic matter is enriched in Fe2O3, CaO, MnO, TiO2, Cs, Co, As, Cd, Ba, Ni, Sb, MgO, Zn, and V. The remaining elements are high in the glass fraction. The concentration of K2O, Na2O, P2O5, Nb, Cr, Ta, U, W, Rb, and Ni do not clearly vary with particle size, while SiO2 and Hg decrease and the remaining elements clearly increase with decreasing particle size. ?? 2009 Elsevier B.V.

Dai, S.; Zhao, L.; Peng, S.; Chou, C.-L.; Wang, X.; Zhang, Y.; Li, D.; Sun, Y.

2010-01-01

215

Geochemistry of Mesoproterozoic sedimentary rocks of upper Vindhyan Group, southeastern Rajasthan and implications for weathering history, composition and tectonic setting of continental crust in the northern part of Indian shield  

NASA Astrophysics Data System (ADS)

The upper Vindhyan succession of southeastern Rajasthan is divisible into Kaimur, Rewa and Bhander Groups. The major and trace element (including rare earth elements) data of the upper Vindhyan shales and sandstones are investigated to determine the weathering history, composition, and tectonic setting of Mesoproterozoic continental crust. CIA (chemical index of alteration) values, A-CN-K plot (A = Al2O3, CN = CaO* + Na2O, K = K2O) and depletion in U, Na2O, CaO, Sr and Ba suggest that the source area experienced moderate to high degree of chemical weathering under warm and humid conditions. Provenance modeling indicates that the Kaimur sandstones are best modeled with a mixture having 40% granitic gneiss, 20% Tonalite-Trondhjemite-Granodiorite (TTG), 20% mafic enclaves and 20% Berach Granite of the Banded Gneissic Complex (BGC). A mixture of 60% granitic gneiss, 20% mafic enclaves and 20% Berach Granite of the BGC can model the Rewa and Bhander Groups. It is suggested that the upper Vindhyan sedimentation commenced at the time of Delhi-Sausar orogeny at about 1100-1000 Ma. The orogenic movements uplifted the parts of old continental crust in the BGC terrain creating positive areas, which exposed older crustal blocks containing TTG as important component. The debris of Kaimur sandstone probably derived from these uplifted blocks. As indicated by Palaeocurrent data, the Rewa and Bhander formations were derived from Bundelkhand Granitic Gneiss Complex (BGGC) occurring to the north of the basin and/or the Chotanagpur Granitic Gneiss Complex (CGGC) of eastern Indian shield. The derivation of Lower and upper groups of Vindhyan succession from different source terrains of identical composition suggests that at the time of Vindhyan sedimentation, the BGC of Rajasthan, the BGGC of Central India and the CGGC of eastern India had similar lithological composition. This implies that well before the origin of the Vindhyan basin these discrete terrains evolved as a single unit that existed as a Mesoarchaean nucleus in the northern part of the Indian shield.

Raza, Mahshar; Khan, Abdullah; Bhardwaj, V. R.; Rais, Sarwar

2012-04-01

216

Mineralogy, geochemistry and genesis of the modern sediments of Seyfe Lake, K?r?ehir, central Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

Seyfe Lake (K?r?ehir, Turkey) is located within a depression zone extending along a NW-SE-trending fault in central Anatolia. Evaporite and carbonate sediments occur at the bottom of the lake which is fed by high-sulfate spring and well waters circulating N-S through salt domes. The recent sediments of Seyfe Lake are deposited in delta, backshore, beach, mud-flat and shallow lake environments. In the mud-flat environment, calcite, gypsum, halite, and thenardite are associated with fine-grained detrital sediments. Sediments from the margin to the lake center are distributed as calcite, gypsum and halite ± thenardite, yielding an annular distribution pattern. An increase in Na2O, SO3, and S, and a decrease in CaO toward the lake center are due to sediment distribution. On the other hand, a positive correlation of SiO2 with MgO, K2O, Na2O, Al2O3, and Fe2O3 + TiO2 is attributed to the presence of smectite, illite and feldspar. In addition, a positive correlation of Sr and Ba with CaO is related to the amount of gypsum in the sediments. Strontium is associated with in situ gypsum crystals; it increases in the intermediate and central zones of the lake as a result of a relative increase in salinity toward the lake center. The association of Sr with gypsum in the sediments suggests that Ca and Sr were derived from Sr-bearing evaporites and their carbonate host rocks, which were the likely aquifers for the brine. The S- and O-isotopic compositions of sulfate crystals range from +19.1‰ to +21.7‰ and from +16.9‰ to +20.9‰ SMOW, respectively, suggesting precipitation in a closed lake system. A relative increase of oxygen and sulfur isotope ratios toward the lake center suggests dissolution of gypsum in the host rock, with contributions from circulating groundwater and sulfate reduction (possibly by bacterial reduction). 87Sr/86Sr isotope ratios range from 0.707286 to 0.707879, suggesting a non-marine Oligo-Pliocene evaporitic host rock source for precipitation in Seyfe Lake. The concentration of Sr- and S-isotope ratios in the gypsum crystals indicates formation by precipitation/recrystallization from brine rather than from seawater.

Önalgil, Nergis; Kadir, Selahattin; Külah, Tacit; Eren, Muhsin; Gürel, Ali

2015-02-01

217

Silicate melt inclusions in clinopyroxene phenocrysts from mafic dikes in the eastern North China Craton: Constraints on melt evolution  

NASA Astrophysics Data System (ADS)

Silicate melt inclusions (SMIs) in magmatic minerals provide key information on the chemical and mineralogical evolution of source magmas. The widespread Cretaceous mafic dikes in the Jiaojia region of the eastern North China Craton contain abundant SMIs within clinopyroxene phenocrysts. The daughter minerals in these SMIs include amphibole, plagioclase, pyrite and ilmenite, together with CO2 + CH4 and CH4 as the major volatile phase. The total homogenization temperatures of the SMIs range between 1280 and 1300 °C. The host clinopyroxene phenocrysts in these dolerite dikes are dominantly augite with minor diopside. From LA-ICPMS analyses of the SMIs, we identify two compositional groups: (1) low-MgO (6.0-7.6 wt.%) SMIs and (2) high-MgO (11.2-13.9 wt.%) SMIs. The Low-MgO group exhibits higher concentrations of TiO2, Al2O3, Na2O, P2O5 and lower CaO and CaO/Al2O3 ratio as compared to the high-MgO SMIs. The trace element patterns of the two types of SMIs are similar to those of the host mafic dikes. However, the low-MgO SMIs and host mafic dikes are clearly more enriched in all the trace elements as compared to the high-MgO type, especially with regard to the highly incompatible elements. The estimated capture temperatures and pressures are 1351-1400 °C and 1.6-2.1 GPa for the high-MgO SMIs and 1177-1215 °C and 0.6-1.1GPa for the low-MgO type. The high-MgO and low-MgO SMIs were trapped at depths of ?51-68 km and ?20-35 km, respectively. Computations show that the parental melt is mafic with SiO2 content 49.6 wt% and Mg# 80.0 with relatively low total alkali contents (1.35 wt% Na2O + K2O) and high CaO (15.2 wt%). Exploratory runs with the program MELTS and pMELTS show that the low-MgO and high-MgO SMIs were derived from the same parental melt through different degrees of crystallization. Clinopyroxene and a small amount of olivine were the fractionating phases during the evolution from parental melts to high MgO melts, while the low MgO melts experienced significant fractional crystallization of olivine and clinopyroxene. We postulate the newly accreted lithospheric clinopyroxenite as the major source for the Jiaojia dolerite dikes, with melting of the source at a depth of ?68-80 km.

Cai, Ya-Chun; Fan, Hong-Rui; Santosh, M.; Hu, Fang-Fang; Yang, Kui-Feng; Liu, Xuan; Liu, Yongsheng

2015-01-01

218

Enhanced dechlorination of chlorobenzene and in situ dry sorption of resultant Cl-compounds by CaO and Na2CO3 sorbent beds incorporated with Fe2O3.  

PubMed

The dechlorination of C(6)H(5)Cl and the in situ dry sorption of Cl-compounds produced by C(6)H(5)Cl decomposition in an alkaline sorbent of CaO or Na(2)CO(3) incorporated with Fe(2)O(3) were studied. A sample gas containing C(6)H(5)Cl at an initial concentration of 500 ppm balanced by either N(2), O(2) (5%)-N(2) or H(2)O (10%)-N(2) carrier gas was introduced into a lab-scale quartz tube reactor where CaO or Na(2)CO(3) sorbent was packed with Fe(2)O(3). Subsequently, the effect of Fe(2)O(3) addition to CaO or Na(2)CO(3) on the removal of C(6)H(5)Cl, achieved by the decomposition of C(6)H(5)Cl as well as the dry sorption of Cl-compounds produced by C(6)H(5)Cl decomposition, was investigated. It was found that the decomposition of C(6)H(5)Cl in CaO or Na(2)CO(3) sorbent bed incorporated with Fe(2)O(3) occurred in the lower temperatures, compared to the case when only CaO or Na(2)CO(3) sorbent bed was used. Thus, Fe(2)O(3) was found to play a catalytic role in the oxidative decomposition of C(6)H(5)Cl. Further, the decomposition of C(6)H(5)Cl in a bed containing only Fe(2)O(3) was promoted by the presence of O(2) and H(2)O in the reaction atmosphere. Moreover, a higher amount of Cl was absorbed in the combined CaO/Fe(2)O(3) and Na(2)CO(3)/Fe(2)O(3) beds, compared to the absorption of Cl-compounds in only CaO or Na(2)CO(3) sorbent bed. Finally, the comparison of CaO and Na(2)CO(3) sorbents showed that the decomposition of C(6)H(5)Cl and the in situ dry sorption of the resultant Cl-compounds in the combined Na(2)CO(3) and Fe(2)O(3) beds were higher than those in the combined CaO and Fe(2)O(3) beds. PMID:19101013

Matsuda, H; Ito, T; Kuchar, D; Tanahashi, N; Watanabe, C

2009-03-01

219

Petrogenesis of syntectonic granites emplaced at the transition from thrusting to transcurrent tectonics in post-collisional setting: Whole-rock and Sr-Nd-Pb isotope geochemistry in the Neoproterozoic Quatro Ilhas and Mariscal Granites, Southern Brazil  

NASA Astrophysics Data System (ADS)

The Neoproterozoic post-collisional period in southern Brazil (650-580 Ma) is characterized by substantial volumes of magma emplaced along the active shear zones that compose the Southern Brazilian Shear Belt. The early-phase syntectonic magmatism (630-610 Ma) is represented by the porphyritic, high-K, metaluminous to peraluminous Quatro Ilhas Granitoids and the younger heterogranular, slightly peraluminous Mariscal Granite. Quatro Ilhas Granitoids include three main petrographic varieties (muscovite-biotite granodiorite — mbg; biotite monzogranite — bmz; and leucogranite — lcg) that, although sharing some significant geochemical characteristics, are not strictly comagmatic, as shown by chemical and Sr-Nd-Pb isotope data. The most primitive muscovite-biotite granodiorite was produced by contamination of more mafic melts (possibly with some mantle component) with peraluminous crustal melts; the biotite monzogranite, although more felsic, has higher Ca, MgO, TiO2 and Ba, and lower K2O, FeOt, Sr and Rb contents, possibly reflecting some mixing with coeval mafic magmas of tholeiitic affinity; the leucogranite may be derived from pure crustal melts. The Mariscal Granite is formed by two main granite types which occur intimately associated in the same pluton, one with higher K (5-6.5 wt.% K2O) high Rb and lower CaO, Na2O, Ba and Zr as compared to the other (3-5 wt.% of K2O). The two Mariscal Granite varieties have compositional correspondence with fine-grained granites (fgg) that occur as tabular bodies which intruded the Quatro Ilhas Granoitoids before they were fully crystallized, and are inferred to correspond to the Mariscal Granite feeders, an interpretation that is reinforced by similar U-Pb zircon crystallization ages. The initial evolution of the post-collisional magmatism, marked by the emplacement of the Quatro Ilhas Granitoids varieties, activated sources that produced mantle and crustal magmas whose emplacement was controlled both by flat-lying and transcurrent structures. The transition from thrust to transcurrent-related tectonics coincides with the increase in the proportion of crustal-derived melts. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas and may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of orthogneiss protoliths.

Florisbal, Luana Moreira; Bitencourt, Maria de Fátima; Janasi, Valdecir de Assis; Nardi, Lauro Valentim Stoll; Heaman, Larry M.

2012-11-01

220

Geochronological and geochemical constraints on the petrogenesis of the early Paleoproterozoic potassic granite in the Lushan area, southern margin of the North China Craton  

NASA Astrophysics Data System (ADS)

We conducted a geochronological and geochemical study on the Paleoproterozoic potassic granites in the Lushan area, southern margin of the North China Craton (NCC) to understand the tectonic regime of the NCC at 2.2-2.1 Ga. This rock suite formed at 2194 ± 29 Ma. The rocks are rich in SiO2 (76.10-77.73 wt.%), and K2O (5.94-6.90 wt.%) with high K2O + Na2O contents from 7.56 wt.% to 8.48 wt.%, but poor in CaO (0.10-0.28 wt.%), P2O5 (0.02-0.05 wt.%) and MgO (0.01-0.30 wt.%, Mg# = 1.08-27.3), indicating they experienced fractional crystallization. Major element compositions suggest the potassic granites share an affinity with high K calc-alkaline granite. Even though the Lushan potassic granitic rocks have high A/CNK ratios (1.11-1.25), which can reach peraluminous feature, the very low P2O5 contents and negative correlation of P2O5 and SiO2 ruling out they are S-type granites. Different from peralkaline A-type granites, the Lushan potassic granites have variable Zr concentrations (160-344 ppm, 226 ppm on average) and 10,000 Ga/Al ratios (1.76-3.00), together with high zircon saturation temperatures (TZr = 826-885 °C), indicating they are fractionated aluminous A-type granites. Enriched LREE ((La/Yb)N = 9.72-81.8), negative Eu anomalies, and low Sr/Y with no correlations in Sr/Y and Sr/Zr versus CaO suggest the possible presence of Ca-rich plagioclase and absence of garnet in the residual. Magmatic zircon grains have variable ?Hf(t) values (-2.4 to +7.3) with zircon two-stage Hf model ages (TDMC) varying from 2848 Ma to 2306 Ma (mostly around ca. 2.5 Ga), and are plotted in the evolution line of crustal felsic rock. We propose that the rocks mainly formed by partial melting of ca. 2.50 Ga tonalitic-granodioritic crust as a result of upwelling mantle-derived magmas which provided thermal flux and source materials in an intra-continent rifting. The ca. 2.2 Ga magmatism suggests that intra-continental rifting occurred at 2.35-1.97 Ga at least in the southern margin of the NCC after its final cratonization in the late Neoarchean.

Zhou, Yanyan; Zhai, Mingguo; Zhao, Taiping; Lan, Zhongwu; Sun, Qianying

2014-11-01

221

Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites  

NASA Astrophysics Data System (ADS)

A combined study of whole-rock major-trace elements and Sr-Nd isotopes, zircon U-Pb ages, Hf and O isotopes as well as biotite geochemistry was carried out for Triassic granite intrusions from the Nanling Range in South China. The results provide insights into the effects of source composition and melting conditions on the geochemical diversity of granites. The granites of interest are peraluminous, and contain primary muscovite and tourmaline. They are characterized by high zircon ?18O values of > 9.0‰, high initial 87Sr/86Sr values of ~ 0.7200, and homogeneous ?Nd(t) values of - 11.3 to - 9.8, as well as variable zircon ?Hf(t) values of - 12.2 to - 5.8. Biotite geochemistry is similar to that of common peraluminous granites. An integrated interpretation of these petrological, mineralogical and geochemical data indicates that these granites were derived from partial melting of metasedimentary rocks under variable physicochemical conditions. The differences in whole-rock and biotite geochemistry between the intrusions are ascribed to the variable effects of source heterogeneity and melting temperature. The Luxi intrusion exhibits higher contents of MgO, FeOT, TiO2 and CaO than common melts derived from metasedimentary rocks, tight variations in major-trace elements and homogeneous Sr-Nd isotopic compositions, and homogeneous biotite composition with high Mg# [= Mg / (Mg + Fe) in molar] and lower whole-rock A/CNK values [= Al2O3 / (CaO + Na2O + K2O) in molar]. These can be explained by originating from a relatively mafic metasedimentary source. On the other hand, the geochemical diversity of granites can be caused by the difference in melting temperature in addition to the source heterogeneity. This is suggested by the Xiazhuang and Fucheng intrusions which exhibit similar range of SiO2. Nevertheless, the Fucheng intrusion is ferroan, and high in TiO2, (Na2O + K2O)/CaO, TiO2/MgO, Ga/Al and Zr + Nb + Ce + Y, but low in CaO, MgO and Mg#. Most of its major elements and their ratios are similar to those of A-type granites that were generated from F-rich rocks at high temperatures, consistent with the enrichment of Fe and F in its biotite. Thus, partial melting of a metasedimentary restite at reduced conditions after previous melt extraction is suggested to produce the geochemical feature of A-type granites in the Fucheng intrusion. In contrast, partial melting of fertile metasedimentary rocks would produce normal S-type granites like the Xiazhuang intrusion, with its geochemical variations ascrible to source heterogeneity and differential melting. Therefore, the geochemical composition of granites is primarily dictated by the composition of source rocks in addition to the physicochemical conditions of partial melting.

Gao, Peng; Zhao, Zi-Fu; Zheng, Yong-Fei

2014-12-01

222

Progress in tissue engineering to repair joint damage in osteoarthritis A/P Cao Tong Medical scientists now have "clear" evidence that the damaged cartilage tissue in osteoarthritis and  

E-print Network

Progress in tissue engineering to repair joint damage in osteoarthritis ­ A/P Cao Tong Medical joint disorders can be encouraged to regrow and regenerate, and are developing tissue engineering of tissue engineering to treat joint damage, the researchers summarized their own work and scanned global

Chaudhuri, Sanjay

223

Role of CaO addition in the local order around Erbium in SiO2GeO2P2O5 fiber preforms F. d'Acapito C. Maurizio  

E-print Network

Role of CaO addition in the local order around Erbium in SiO2­GeO2­P2O5 fiber preforms F. d/crystalline local structure around the Er3+ ion is evidenced. Keywords: Optic fibers; EXAFS; Erbium; Nanoparticles 1. Among the rare earths, erbium is especially interesting because the 4I13/2 - 4I15/2 transition at 1

Boyer, Edmond

224

Kinetic analysis of the carbonation reactions for the capture of CO 2 from air via the Ca(OH) 2–CaCO 3–CaO solar thermochemical cycle  

Microsoft Academic Search

A thermogravimetric analysis of the carbonation of CaO and Ca(OH)2 with 500ppm CO2 in air at 200–450°C is performed as part of a three-step thermochemical cycle to capture CO2 from air using concentrating solar energy. The rate of CaO-carbonation is fitted to an unreacted core kinetic model that encompasses intrinsic chemical reaction followed by intra-particle diffusion. In contrast, the Ca(OH)2-carbonation

V. Nikulshina; M. E. Gálvez; A. Steinfeld

2007-01-01

225

Ab initio study of the positronation of the CaO and SrO molecules including calculation of annihilation rates.  

PubMed

Ab initio multireference single- and double-excitation configuration interaction calculations have been performed to compute potential curves for ground and excited states of the CaO and SrO molecules and their positronic complexes, e(+)CaO, and e(+)SrO. The adiabatic dissociation limit for the (2)?(+) lowest states of the latter systems consists of the positive metal ion ground state (M(+)) and the OPs complex (e(+)O(-)), although the lowest energy limit is thought to be e(+)M + O. Good agreement is found between the calculated and experimental spectroscopic constants for the neutral diatomics wherever available. The positron affinity of the closed-shell X (1)?(+) ground states of both systems is found to lie in the 0.16-0.19 eV range, less than half the corresponding values for the lighter members of the alkaline earth monoxide series, BeO and MgO. Annihilation rates (ARs) have been calculated for all four positronated systems for the first time. The variation with bond distance is generally similar to what has been found earlier for the alkali monoxide series of positronic complexes, falling off gradually from the OPs AR value at their respective dissociation limits. The e(+)SrO system shows some exceptional behavior, however, with its AR value reaching a minimum at a relatively large bond distance and then rising to more than twice the OPs value close to its equilibrium distance. PMID:22522712

Buenker, Robert J; Liebermann, Heinz-Peter

2012-07-15

226

Magnetic interactions in the catalyst used by nature to split water: a DFT + U multiscale study on the Mn4CaO5 core in photosystem II  

NASA Astrophysics Data System (ADS)

An important approach in the design of new environmentally friendly materials is represented by the study of analogous systems already existing in nature. In the search for new water splitting catalysts, the corresponding natural analogue is represented by the oxygen-evolving complex of photosystem II, which is a large membrane protein complex present in photosynthetic organisms. The understanding of the catalytic strategy of its active Mn4CaO5 core is important to unravel the mechanisms of water oxidation in photosynthesis and can serve as an inspiring model for the design of biomimetic catalysts based on largely non-toxic, earth abundant elements. The magnetic interactions between Mn ions are studied in the present work by means of DFT + U broken symmetry ab initio molecular dynamics within a quantum mechanics/molecular mechanics framework. The room temperature dynamics of two different structural models (i.e. with total high-spin and total low-spin ground states) was stable during the simulated time. We observed large fluctuations of the magnetic coupling constants calculated on both the structural models of the complex, causing occasionally instantaneous swapping of the ferromagnetic/antiferromagnetic coupling between the metal centers.

Bovi, Daniele; Narzi, Daniele; Guidoni, Leonardo

2014-01-01

227

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

228

Geochemistry and origin of the early Mesoproterozoic mangerite-charnockite-rapakivi granite association of the Serra da Providência suite and associated gabbros, central-eastern Rondônia, SW Amazonian Craton, Brazil  

NASA Astrophysics Data System (ADS)

The Serra da Providência suite (SPS) is constituted of quartz mangerite-charnockite-rapakivi granite and coeval mafic rocks, intruded during the 1.60-1.53 Ga interval into Paleoproterozoic metamorphic basement (Jamari Complex) in the Juruena-Rondônia geochronologic province, SW Amazonian Craton. In this region the Serra da Providência suite consists of two batholiths and several small plutons represented by syeno-monzogranites and igneous quartz mangerite and charnockites. The Serra da Providência granites are ferroan, calc-alkalic to alkali-calcic and characterized by high Na2O + K2O, Rb, Zr, Y, Nb, Ta, Ce, Zn, Ga, and REE (except for Eu), moderate Ba, and low Sr, MgO, and CaO. Ga/Al, Y/Nb, FeOT/(FeOT + MgO) and K2O/Na2O ratios are high and Sr/Ba and Rb/Ba are low and are geochemically similar to typical A2-subtype granites. The SPS charnockites and quartz mangerites display values of FeOT, MgO, CaO, Ba, Rb, Sr, Nb/Ta and Zr/Hf similar to the SPS A-type granites. The occurrence of magnetite as an accessory phase and the high FeOT/(FeOT + MgO) in granites, charnockites and quartz mangerites suggest crystallization from a relatively oxidized magma and also explain the occurrence of titanite as a primary phase in these granites, similar to those reported in several localities of the Amazonian Craton. The parental magma of the mafic rocks of the SPS probably had mainly enriched sources and resulted from melting of heterogeneous mantle reservoirs with coherent chemical characteristics. Trace elements data indicate subduction-modified mantle sources for the mafic rocks that are in agreement with the post-collisional character of this magmatism. A large set of whole-rock Sm-Nd isotope data (Bettencourt et al., 1999; Scandolara, 2006; Santos et al., 2008 and this work) demonstrate that granites, charnockites and quartz mangerites of the study area are the product of magmas derived from interaction between enriched mantle derived magmas (in very subordinate proportions) and recycled crust in larger proportion. The source region is dominated by Paleoproterozoic material, but several samples yield Archaean model ages that are the first evidence for such ancient source materials in the SW Amazonian Craton. The Serra da Providência suite was emplaced during the post-collisional stage of the Juruena-Jamari arc and Madeirinha orogeny (Scandolara et al., 2011), and post-dates the collision between the Tapajós (Tapajós-Parima geochronological province, Pará, Brazil) and Bolívia (palaeocontinent which precedes Sunsás geochronological province) blocks. Its geochemical and structural features are coincident with those recognized in post-collisional granitoids. Geochemical data suggest that complex processes which involved crustal melting, fractional crystallization, magma mixing and, in some extent, crustal assimilation were responsible for the magmatism of the Serra da Providência suite. The magmas that constitute the Serra da Providência suite resulted from varying degrees of partial melting of a compositionally heterogeneous source. The nature of the source and the degree of melting exerted a significant control over compositional variation in some of the parental magmas which were also affected by subsequent fractional crystallization and mingling processes. Internal variations in composition observed in several bodies can be the result of incremental amalgamation of different magma pulses that varied mainly in the degree of partial melting.

Scandolara, Jaime E.; Fuck, Reinhardt A.; Dall'Agnol, Roberto; Dantas, Elton L.

2013-08-01

229

Chemical zonation in olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

Significant zonation in major, minor, trace, and volatile elements has been documented in naturally glassy olivine-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host olivine than in the melt (e.g., MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host olivine than in the melt (e.g., Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an olivine-depleted boundary layer in the adjacent melt in response to cooling and crystallization of olivine on the walls of the melt inclusions, concurrent with diffusive propagation of the boundary layer toward the inclusion center. Concentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease toward the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host olivine late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects. A model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to olivine growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150-13,000 °C h-1 from the liquidus down to ~1,000 °C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1,000 °C ranges from 40 s to just over 1 h. Based on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on olivine-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of olivine on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple olivine crystallization. All melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, olivine-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.

Newcombe, M. E.; Fabbrizio, A.; Zhang, Youxue; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.

2014-07-01

230

Petrography and Geochemistry of the Zamora Batholith in the south of the sub-Andean zone (Ecuador)  

NASA Astrophysics Data System (ADS)

The Zamora Batholith is an intrusive complex that is located in the extreme south-east of Ecuador. It has dimensions of 200 x 50 km approximately. It is mainly located in the Zamora Chinchipe province from which it takes its name. This study consisted in the petrographic and geochemical characterization of the Zamora Batholith in the area covered by 1: 50,000 geological maps of Centro Shaime, Guayzimi, Paquisha, Los Encuentros and El Pangui. Fieldwork was done by the "Proyecto Mapeo Geológico escala 1:50.000 (zonas prospectivas mineras)" of the Instituto Nacional de Investigación Geológico, Minero, Metalúrgico of Ecuador. This research was performed with 59 thin sections and 10 whole - rock chemical analysis done in the C.I.C of the Granada University. The Zamora Batholith intrudes Triassic to Jurassic volcanic rocks. It is overlaid by sandstones of the Hollin Formation of the Upper Aptian age and shale and limestone from the Napo Formation. Post-cretaceous deposits of ash and lava flows of andesitic to rhyolitic compositions cover the batholith. The petrography of the Zamora Batholith ranges from tonalite to monzogranite with the same qualitative mineralogy. The rocks are composed by different proportions of plagioclase, amphibole, feldspar K, quartz, biotite, opaque, pyroxene and epidote, as accessory minerals has zircon, sphene and apatite. To the south of the Conguime and Guayzimi towns, the dominant petrography is medium to coarse grained amphibole granodiorite with tonalitic and monzogranitic subordinates. To the north monzogranites are dominant rocks and subordinate granodiorites. To the East of Santa Elena the sienogranites are associated with El Hito porphyritic granite that intrudes to Zamora Batholith. Frequently the batholith has propylitic alteration; which produces a primary association of chlorite, epidote, calcite and pyrite. The granitoids have dioritic to granitic compositions (60.09 to 73.6 wt.% SiO2) and are I - type, medium to high-K calc-alkaline. They have affinities slightly peraluminous (ASI = 1,00 to 1,16). CaO is moderate to high (CaO ? 3.58), the alkalis have averaged of Na2O?3,09 and K2O?3,28. The concentrations of Na2O/K2O are moderate ranging between 0.7 and 1.7, with an average value of 1.04. The contents of Ba and Sr are moderate. The content of Zr is low (61 to 161 ppm). The multi-element diagrams normalized to chondritic values and to primitive mantle show Nb and Ta negative anomaly. Considering the multi-element diagrams, the rocks are slightly enriched in LILE (Large Ion-Lithophile-elements) mainly in Rb, Cs and Ba and slight positive anomalies in K and Sr, other incompatible elements have negative anomalies such as HFSE ( High Field Strength Elements) Ti, Nb, Ta. The values of (Eu/Eu*)N are in the range of 0.54 to 1.03. (Eu* = (SmN*GdN)1/2). Correlations between major element and silica, and relationships between trace elements indicate that fractional crystallization is a dominant process in the magma evolution. Most granitoids are also slightly peraluminous; but we believe this characteristic is due to rock alteration. The Zamora Batolith is a plutonic complex generated within a magmatic arc in normal conditions of maturity.

Villares, F. M.

2013-05-01

231

Reaction between Metapelite-derived Hydrous Partial Melt and Subsolidus Fertile Peridotite at 2-3 GPa - Generation of High-K Magmas in Subduction Zones  

NASA Astrophysics Data System (ADS)

Trace compositions of arc magmas display signatures of recycled sediments [1] and thermal and geodynamic models of subduction zones suggest that sediment contribution to sub-arc mantle occurs in the form of hydrous melts generated at the slab-mantle interface by fluid-present melting [2, 3] or in the mantle wedge by diapiric rise of downgoing sediments [4]. Partial melts of hydrous pelitic sediments are rhyolitic in P-T conditions of the mantle wedge and are out of equilibrium with the surrounding peridotite, which implies inevitable reaction between such melt and overlying peridotite. However, partial melting in the mantle wedge with slab input has mostly been studied in peridotite+H2O systems [e.g. 5] and experimental constraints on sediment-peridotite hybrid remain limited [6]. In this study, we explore the phase equilibria of a sediment melt-fluxed fertile peridotite with the aim of understanding genesis of high-K arc magmas. Experiments were performed in AuPd capsules using a piston cylinder, on a 1:3 mixture of rhyolitic melt with 7.3 wt.% H2O [3] and fertile peridotite from 1150-1350 °C at 2-3 GPa. Interstitial melt/fluid is present at 1150 °C, 2 GPa and 1150-1200 °C, 3 GPa. While residual opx+cpx+biotite are present at both pressures, olivine is present from 1200-1300 °C, 2 GPa and garnet from 1150-1300 °C, 3 GPa. Cpx and biotite disappear at 1200-1250 °C, 2 GPa and 1350 °C, 3 GPa. At 2 GPa, from 1200-1300 °C, the melt composition (on a volatile-free basis), shows an increase in SiO2 (50-51 wt.%), MgO (10-14 wt.%) and decrease in Al2O3 (16-14 wt.%), CaO (10-7 wt.%), Na2O (3-2 wt.%) and H2O (13-8 wt.%.). K2O increases from 5 to 7 wt.% till 1250 °C followed by a decrease to 5 wt.%, at 1300 °C. FeO* varies between 6 and 5 wt.%. At 3 GPa, from 1225-1350 °C, the reacted melt displays an increase in SiO2 (47-49 wt.%), FeO* (4.2-5.4 wt.%), MgO (11-14 wt.%), and decrease in Al2O3 (15-14 wt.%), CaO (12-7 wt.%), Na2O (4-3 wt.%) and H2O (16-11 wt.%). K2O displays an increase from 7 to 8 wt.%, till 1300 °C, followed by a decrease to 7 wt.%, after the disappearance of biotite. Our study demonstrates that shoshonitic melt can be generated from partial reactive crystallization of sediment-derived hydrous rhyolite in a fertile peridotite matrix at high melt:rock ratio. Thus, we propose that such a melt-rock reaction can produce high-K arc magmas with trace element signatures of recycled sediments. Also, the phlogopite-bearing websterite produced as a residue of reaction in our study, upon survival in the wedge, can produce post-collisional high K-magmas by later tectonic perturbation and rifting-induced decompression. [1] Plank & Langmuir (1993) Nature 362, 739-743. [2] Syracuse & Abers (2010) PEPI 183, 73-90. [3] Hermann & Spandler (2008) JPet 49, 717-740. [4] Behn et al. (2011) NatGeoSci 4, 641-646. [5] Grove et al. (2006) EPSL 249, 74-89. [6] Sekine & Wyllie (1982) CMP 81, 190-202.

Nelson, J. M.; Mallik, A.; Dasgupta, R.

2013-12-01

232

Growth of Megaspherulites In a Rhyolitic Vitrophyre  

NASA Technical Reports Server (NTRS)

Megaspherulites occur in the middle zone of a thick sequence of rhyolitic vitrophyre that occupies a small, late Eocene to early Oligocene volcanic-tectonic basin near Silver Cliff, Custer County, Colorado. Diameters of the megaspherulites range from 0.3 m to over 3.66 m, including a clay envelope. The megaspherulites are compound spherulites. consisting of an extremely large number (3.8 x 10(exp 9) to 9.9 x 10(exp 9)) of individual growth cones averaging 3 mm long by 1.25 mm wide at their termination. They are holocrystalline, very fine- to fine-grained, composed of disordered to ordered sanidine (orthoclase) and quartz, and surrounded by a thin K-feldspar, quartz rich rind, an inner clay layer with mordenite, and an outer clay layer composed wholly of 15 A montmorillonite. Whole rock analyses of the megaspherulites show a restricted composition from their core to their outer edge, with an average analyses of 76.3% SiO2, 0.34% CaO, 2.17% Na2O, 6.92% K2O, 0.83% H2O+ compared to the rhyolitic vitrophyre from which they crystallize with 71.07% SiO2, 0.57% CaO, 4.06% Na2O,4.l0% K2O, and 6.40% H2O+. The remaining oxides of Fe2O3 (total Fe), A12O3, MnO,MgO, TiO2, P2O5, Cr2O3, and trace elements show uniform distribution between the megaspherulites and the rhyolitic vitrophyre. Megaspherulite crystallization began soon after the rhyolitic lava ceased to flow as the result of sparse heterogeneous nucleation, under nonequilibrium conditions, due to a high degree of undercooling, delta T. The crystals grow with a fibrous habit which is favored by a large delta T ranging between 245 C and 295 C, despite lowered viscosity, and enhanced diffusion due to the high H2O content, ranging between 5% and 7%. Therefore, megaspherulite growth proceeded in a diffusion controlled manner, where the diffusion, rate lags behind the crystal growth rate at the crystal-liquid interface, restricting fibril lengths and diameters to the 10 micron to 15 micron and 3 micron and 8 micron ranges respectively. Once diffusion reestablishes itself at the crystallization front, a new nucleation event occurs at the terminated tips of the fibril cones and a new cone begins to develop with a similar orientation (small angle branching) to the earlier cones. During crystallization, these fibril cones impinge upon each other, resulting in fibril cone-free areas. These cone-free areas consist of coarser, fine-grained phases, dominated by quartz, which crystallized from the melt as it accumulated between the crystallizing K-feldspar fibrils of the cones. The anhydrous nature of the disordered to ordered sanidine (orthoclase) and quartz, suggests that water in the vitrophyre moved ahead of the crystallization front, resulting in a water rich fluid being enriched in Si, K, Na, Mg, Ca, Sr, Ba, and Y. The clay layers associated with the megaspherulites are therefore, the result of the deuteric alteration between the fractionated water and the vitrophyre, as indicated by the presence of the minerals mordenite and montmorillonite. This silica rich fluid also resulted in the total silicification of the megaspherulites within the upper 3 m of the vitrophyre.

Smith, Robert K.; Tremallo, Robin L.; Lofgren, Gary E.

2000-01-01

233

Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization  

NASA Astrophysics Data System (ADS)

Water-Rock Interaction is one of the most hot-debated issues among geologists, geophysicists, as well as geochemists. Abyssal peridotites recovered from the seafloor are often greatly affected or alterated by seawater in the form of serpentinization. The alteration to the peridotites makes it difficult to do the straightforward analysis for its primary composition as it was settled in the upper mantle, which confine the usage of these rare direct samples from the mantle in the scientific study, such as mantle dynamics, mantle composition and crust-mantle interaction. Besides, It was revealed recently that the serpentinization of abyssal peridotites may give birth to the hydrothermal activity. The elements migration during the serpentinization may perform a great role on the chemical composition of the hydrothermal fluid, which can support a hidden chemosynthetic ecosystem in the abyssal seabed. The research work focused on the major elements behavior during the serpentinization by studying the partially serpentinized samples of abyssal peridotite from Southwest Indian Ridge. The primary mineral assemblage of peridotite is olivine (Mg2SiO4), orthopyroxene (Mg2Si2O6), clinopyroxene (CaMgSi2O6) and spinel ((Mg,Fe)(Al,Cr)2O4). The major chemical composition are usually as SiO2 (30~45wt.%), MgO (20~45 wt.%), FeO and Fe2O3 (total 5~15 wt.%). Besides there are very few MnO, CaO, Al2O3, Cr2O3, NiO, Na2O, K2O and H2O. While on the other hand the serpentinized peridotite shows a more complicated mineral assemblage, besides the primary minerals there are more alteration minerals, such as serpentine (Mg3[Si2O5](OH)4), magnetite (Fe3O4), talc (Mg3[Si4O10](OH)2), brucite (Mg(OH)2), tremolite (Ca2Mg5[Si8O22](OH)2), chromite (FeCr2O4), chlorite ((Mg,Fe)6[(Si,Al)4O10](OH)8), and other accessary minerals like native metals, sulfides, clay minerals and hornblende. According to the EMPA analysis, the serpentinized sample shows the chemical composition as SiO2(~40 wt.%), MgO(~30 wt.%), total FeO(~7 wt.%), Al2O3(~1 wt.%), MnO(~0.4 wt.%), Cr2O3(~0.3 wt.%), NiO(~0.2 wt.%), CaO(~0.2 wt.%), and very few TiO2, Na2O and K2O. The overall percentages for all the elements mentioned above are usually around 80wt.%, about 20% less than full percent, which indicates the volatile matters in the altered samples. Based on the preliminary study, we get the general picture for the major elements behavior during the alteration. Taking the abyssal peridotite for example, it gains large quantities of H and O in the form of H2O, and other volatile elements like F, Cl, B from the seawater during serpentinization. It may also get additional Na, K, Mg from the seawater as shown from the standardized concentration in primary minerals as well as altered minerals. It loses Fe, Al, Ca, Si during the serpentinization seen from the EMPA mapping results. The element Mn, Cr and Ni are relatively immobile during the alteration. To get more precise deduction as to the element budget during the alteration process, much more sensitive analytical instruments like LA-ICP-MS are needed. And more work need to be done to get the quantitive estimation for transferring rate of each element.

Yu, X.; Dong, Y.; Li, X.; Chu, F.

2012-12-01

234

Bioactive borate glass scaffolds: in vitro and in vivo evaluation for use as a drug delivery system in the treatment of bone infection  

Microsoft Academic Search

The objective of this work was to evaluate borate bioactive glass scaffolds (with a composition in the system Na2O–K2O–MgO–CaO–B2O3–P2O5) as devices for the release of the drug Vancomycin in the treatment of bone infection. A solution of ammonium phosphate,\\u000a with or without dissolved Vancomycin, was used to bond borate glass particles into the shape of pellets. The in vitro degradation

Xin Liu; Zongping Xie; Changqing Zhang; Haobo Pan; Mohamed N. Rahaman; Xin Zhang; Qiang Fu; Wenhai Huang

2010-01-01

235

Evaluation of pyroplastic deformation in sanitaryware porcelain bodies  

Microsoft Academic Search

In this study, the effect of composition on the pyroplastic deformation of a sanitaryware porcelain bodies was investigated. Systematic compositional arrangements were made to combine different amounts of SiO2\\/Al2O3 and Na2O\\/K2O ratios. It was found that fleximeter analyses can be successfully utilised not only to measure the viscosity of a system but also to determine the pyroplastic deformation behaviour of

Derya Ye?im Tunçel; Emel Özel

236

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

237

Dilatometeric study of shrinkage during sintering process for porcelain stoneware body in presence of nepheline syenite  

Microsoft Academic Search

The shrinkage of porcelain stoneware body containing different values of nepheline syenite was investigated. Dilatomeric tests were carried out on suitable specimens to obtain the expansion-shrinkage behavior of ceramic bodies. The differences found in shrinkage data were evaluated by kinetic model and determination of activation energy. The results showed that the activation energy increases with Na2O+K2O\\/quartz ratio and reaches to

A. Salem; S. H. Jazayeri; E. Rastelli; G. Timellini

2009-01-01

238

In situ Raman spectroscopy investigation of bioactive glass reactivity: Simulated body fluid solution vs TRIS-buffered solution  

Microsoft Academic Search

In the present contribution, the innovative in situ Raman micro-spectroscopy was applied to investigate the in vitro reactivity of various bioactive glasses. All the investigated glasses belonged to the Na2O\\\\K2O–CaO–P2O5–SiO2 system, but contained sensibly different percentages of network modifiers. The glasses were immersed for increasing times, up to 96h, in simulated body fluid (SBF) and in tris-buffered (TRIS) solution. In

D. Bellucci; G. Bolelli; V. Cannillo; A. Cattini; A. Sola

2011-01-01

239

A Study of Melt Inclusions in Tin-Mineralized Granites From Zinnwald, Germany  

NASA Astrophysics Data System (ADS)

We have analyzed silicate melt inclusions from drill core samples from the eastern Erzgebirge region, Germany, to investigate magmatic-hydrothermal and mineralizing processes in compositionally evolved, tin-bearing granitic magmas. Silicate melt inclusions are small blebs of glass that are trapped or locked within phenocrysts and may contain high concentrations of volatiles that usually leave magma via degassing. Quartz phenocrysts were carefully hand picked from crushed samples of albite-, zinnwaldite- +/- lepidolite-bearing granitic dikes from Zinnwald and soaked in cold dilute HF to remove any attached groundmass. The cleaned phenocrysts were loaded into precious metal capsules with several drops of immersion oil to create a reducing environment at high temperature. The quartz-bearing capsules were inserted into quartz glass tubes, loaded into a furnace for heating at temperatures of 1025\\deg and 1050\\deg C (1atm) for periods of 20 to 30 hours, and subsequently the inclusions were quenched to glass. The inclusions were analyzed for major and minor elements (including F, Cl, and P) by electron microprobe and for H2O, trace elements, and ore elements by ion microprobe. The melt inclusion compositions are similar to that of the whole-rock sample from which the quartz separates were extracted. The average melt inclusion and whole-rock compositions are peraluminous, high in silica and rare alkalis, and low in MgO, CaO, FeO, MnO, and P2O5. Unlike the whole-rock sample, the melt inclusions contain from 0.5 to more than 4 wt.% F. The Cl contents of the inclusions are variable and range from hundreds of ppm to several thousand ppm. The variable and strong enrichments in F of the melt inclusions may correlate with (Na2O/Na2O+K2O) in the inclusions which is consistent with crystal fractionation of feldspars which drives the residual melt to increasing Na contents. Overall, the compositions of these melt inclusions are different from melt inclusions extracted from the highly peraluminous, tin-mineralized granites of the western Erzgebirge region. The latter represent extreme compositional evolution of P- and F-rich magmas. The inclusions from the albite-, zinnwaldite-, +/- lepidolite-bearing granitic dikes of Zinnwald are more similar, compositionally, to those in tin-mineralized rhyolites of Mexico and New Mexico; the Erzgebirge dike melt inclusions container comparatively greater abundances of Li, Sn, and F, however.

Sookdeo, C. A.; Webster, J. D.; Eschen, M. L.; Tappen, C. M.

2001-12-01

240

Partial melting of apatite-bearing charnockite, granulite, and diorite: Melt compositions, restite mineralogy, and petrologic implications  

NASA Technical Reports Server (NTRS)

Melting experiments (P = 6.9 kbar, T = 850-950 deg C, NNO is less than fO2 is less than HM) were done on mafic to felsic charnockites, a dioritic gneiss, and a felsic garnet granulite, all common rock types in the Grenville basement of eastern North America. A graphite-bearing granulite gneiss did not melt. Water (H2O(+) = 0.60 to 2.0 wt %) is bound in low-grade, retrograde metamorphic minerals and is consumed during the earliest stages of melting. Most melts are water-undersaturated. Melt compositions range from metaluminous, silicic granodiorite (diorite starting composition) to peraluminous or weakly metaluminous granites (all others). In general, liquids become more feldspathic, less silicic, and less peraluminous and are enriched in FeO, MgO, and TiO2 with increasing temperature. Residual feldspar mineralogy controls the CaO, K2O, and Na2O contents of the partial melts and the behavior of these elements can be used, particularly if the degree of source melting can be ascertained, to infer some aspects of the feldspar mineralogy of the source. K-feldspar, a common restite phase in the charnockite and granulite (but not the diorite) should control the behavior of Ba and, possibly, Eu in these systems and yield signatures of these elements that can distinguish source regions and, in some cases, bulk versus melt assimilation. Apatite, a common restite phase, is enriched in rare earth elements (REE), especially middle REE. Retention of apatite in the restite will result in steep, light REE-enriched patterns for melts derived from the diorite and charnockites.

Beard, James S.; Lofgren, Gary E.; Sinha, A. Krishna; Tollo, Richard P.

1994-01-01

241

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

PubMed Central

Scaffolds of 13–93 bioactive glass (6Na2O, 12K2O, 5MgO, 20CaO, 4P2O5, 53SiO2; 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) 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 (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.

2011-01-01

242

Electron- and Photon-stimulated Desorption of Alkali Atoms from Lunar Sample and a Model Mineral Surface  

NASA Technical Reports Server (NTRS)

We report recent results on an investigation of source mechanisms for the origin of alkali atoms in the tenuous planetary atmospheres, with focus on non-thermal processes (photon stimulated desorption (PSD), electron stimulated desorption (ESD), and ion sputtering). Whereas alkaline earth oxides (MgO, CaO) are far more abundant in lunar samples than alkali oxides (Na2O, K2O), the atmosphere of the Moon contains easily measurable concentrations of Na and K, while Ca and Mg are undetected there; traces of Ca have recently been seen in the Moon's atmosphere (10-3 of Na). The experiments have included ESD, PSD and ion sputtering of alkali atoms from model mineral surface (amorphous SiO2) and from a lunar basalt sample obtained from NASA. The comparison is made between ESD and PSD efficiency of monovalent alkalis (Na, K) and divalent alkaline earths (Ba, Ca).The ultrahigh vacuum measurement scheme for ESD and PSD of Na atoms includes a highly sensitive alkali metal detector based on surface ionization, and a time-of-flight technique. For PSD measurements, a mercury arc light source (filtered and chopped) is used. We find that bombardment of the alkali covered surfaces by ultraviolet photons or by low energy electrons (E>4 eV) causes desorption of hot alkali atoms. This results are consistent with the model developed to explain our previous measurements of sodium desorption from a silica surface and from water ice: electron- or photon-induced charge transfer from the substrate to the ionic adsorbate causes formation of a neutral alkali atom in a repulsive configuration, from which desorption occurs. The two-electron charge transfer to cause desorption of divalent alkaline eath ions is a less likely process.The data support the suggestion that PSD by UV solar photons is a dominant source process for alkalis in the tenuous lunar atmosphere.

Yakshinskiy, B. V.; Madey, T. E.

2003-01-01

243

Bizarre geochemistry of komatiites from the Crixás greenstone belt, Brazil  

NASA Astrophysics Data System (ADS)

Komatiite lava flows in the Crixás greenstone belt, Goiás, Brazil, have textures and volcanic structures typical of Archean komatiites, but are geochemically most unusual. The flows are porphyritic and massive, or layered with spinifex upper parts and olivine cumulate lower parts. MgO contents range from 18 to 40%. In such lavas, only olivine (and minor chromite) can have crystallized, but neither major nor trace elements fall on olivine control lines. In MgO variation diagrams, CaO and Sr fall on lines with slopes steeper than olivine control lines; SiO2, FeO, Na2O, K2O and Y show little systematic variation; Zr shows a large variation that does not correlate with MgO; and Al2O3 decreases markedly with decreasing MgO. The aberrant behaviour is highlighted by the REE (rare earth elements) in spinifex and olivine cumulate layers from three flows: in the spinifex layers, chondrite-normalized REE patterns are hump-shaped with maxima at Nd or Sm ((La/Sm)N=0.6, (Gd/Yb)N=1.6 2.3), whereas cumulate zones in the same flows have steadily sloping patterns, with LREE enriched relative to HREE ((La/Sm)N=1.3, (Gd/Yb)N=1.4). Neither normal magmatic processes acting during emplacement of the komatiites, nor thermal erosion and wall-rock assimilation can explain these effects, and we speculate that elements commonly thought of as “immobile” (e.g. Al, Zr, REE) migrated during hydrothermal alteration or metamorphism. A Pb-Pb whole rock isochron gave an age of 2,728±140 Ma and selected Sm-Nd analyses an apparent isochron age of 2,825±98 Ma (?Nd?0). The Pb-Pb age is believed to be the approximate time of emplacement. Interpretation of the Sm-Nd data is complicated by the evidence of mobility of REE.

Arndt, N. T.; Teixeira, N. A.; White, W. M.

1989-02-01

244

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

245

Copper-doped borosilicate bioactive glass scaffolds with improved angiogenic and osteogenic capacity for repairing osseous defects.  

PubMed

There is growing interest in the use of synthetic biomaterials to deliver inorganic ions that are known to stimulate angiogenesis and osteogenesis in vivo. In the present study, we investigated the effects of varying amounts of copper in a bioactive glass on the response of human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro and on blood vessel formation and bone regeneration in rat calvarial defects in vivo. Porous scaffolds of a borosilicate bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5, mol.%) doped with 0.5, 1.0 and 3.0wt.% CuO were created using a foam replication method. When immersed in simulated body fluid, the scaffolds released Cu ions into the medium and converted to hydroxyapatite. At the concentrations used, the Cu in the glass was not toxic to the hBMSCs cultured on the scaffolds in vitro. The alkaline phosphatase activity of the hBMSCs and the expression levels of angiogenic-related genes (vascular endothelial growth factor and basic fibroblast growth factor) and osteogenic-related genes (runt-related transcription factor 2, bone morphogenetic protein-2 and osteopontin) increased significantly with increasing amount of Cu in the glass. When implanted in rat calvarial defects in vivo, the scaffolds (3wt.% CuO) significantly enhanced both blood vessel formation and bone regeneration in the defects at 8weeks post-implantation. These results show that doping bioactive glass implants with Cu is a promising approach for enhancing angiogenesis and osteogenesis in the healing of osseous defects. PMID:25534470

Zhao, Shichang; Wang, Hui; Zhang, Yadong; Huang, Wenhai; Rahaman, Mohamed N; Liu, Zhongtang; Wang, Deping; Zhang, Changqing

2015-03-01

246

Oriented bioactive glass (13-93) scaffolds with controllable pore size by unidirectional freezing of camphene-based suspensions: microstructure and mechanical response  

PubMed Central

Scaffolds of 13-93 bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 2P2O5, 54SiO2; mol %), containing oriented pores with controllable diameter, were prepared by unidirectional freezing of camphene-based suspensions (10 vol% particles) on a cold substrate (?196°C or 3°C). By varying the annealing time (0–72 h) to coarsen the camphene phase, constructs with the same porosity (86 ± 1%) but with controllable pore diameters (15–160 ?m) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1 h at 690°C) was accompanied by a decrease in the porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, giving scaffolds with a porosity of 20–60% and average pore diameter of 6–120 ?m. The compressive stress vs. deformation response of the sintered scaffolds in the orientation direction was linear, followed by failure. The compressive strength and elastic modulus in the orientation direction varied from 180 MPa and 25 GPa, respectively, (porosity = 20%) to 16 MPa and 4 GPa, respectively, (porosity = 60%), which were 2–3 times larger than the values in the direction perpendicular to the orientation. The potential use of these 13-93 bioactive glass scaffolds for the repair of large defects in load-bearing bones, such as segmental defects in long bones, is discussed. PMID:20807594

Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang

2010-01-01

247

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

2012-07-01

248

Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars  

NASA Astrophysics Data System (ADS)

diffraction patterns of the three samples analyzed by Curiosity's Chemistry and Mineralogy (CheMin) instrument during the first year of the Mars Science Laboratory mission—the Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstone—show evidence for a significant amorphous component of unclear origin. We developed a mass balance calculation program that determines the range of possible chemical compositions of the crystalline and amorphous components of these samples within the uncertainties of mineral abundances derived from CheMin data. In turn, the chemistry constrains the minimum abundance of amorphous component required to have realistic compositions (all oxides ? 0 wt %): 21-22 wt % for Rocknest and 15-20 wt % for Cumberland, in good agreement with estimates derived from the diffraction patterns (~27 and ~31 wt %, respectively). Despite obvious differences between the Rocknest sand and the Sheepbed mudstone, the amorphous components of the two sites are chemically very similar, having comparable concentrations of SiO2, TiO2, Al2O3, Cr2O3, FeOT, CaO, Na2O, K2O, and P2O5. MgO tends to be lower in Rocknest, although it may also be comparable between the two samples depending on the exact composition of the smectite in Sheepbed. The only unambiguous difference is the SO3 content, which is always higher in Rocknest. The observed similarity suggests that the two amorphous components share a common origin or formation process. The individual phases possibly present within the amorphous components include: volcanic (or impact) glass, hisingerite (or silica + ferrihydrite), amorphous sulfates (or adsorbed SO42-), and nanophase ferric oxides.

Dehouck, Erwin; McLennan, Scott M.; Meslin, Pierre-Yves; Cousin, Agnès.

2014-12-01

249

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

250

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; Bastrakov, E.; Bowbridge, D.; Boyle, P.; Briggs, S.; Brown, D.; Brown, M.; Brownlie, K.; Burrows, P.; Burton, G.; Byass, J.; de Caritat, P.; Chanthapanya, N.; Cooper, M.; Cranfield, L.; Curtis, S.; Denaro, T.; Dhnaram, C.; Dhu, T.; Diprose, G.; Fabris, A.; Fairclough, M.; Fanning, S.; Fidler, R.; Fitzell, M.; Flitcroft, P.; Fricke, C.; Fulton, D.; Furlonger, J.; Gordon, G.; Green, A.; Green, G.; Greenfield, J.; Harley, J.; Heawood, S.; Hegvold, T.; Henderson, K.; House, E.; Husain, Z.; Krsteska, B.; Lam, J.; Langford, R.; Lavigne, T.; Linehan, B.; Livingstone, M.; Lukss, A.; Maier, R.; Makuei, A.; McCabe, L.; McDonald, P.; McIlroy, D.; McIntyre, D.; Morris, P.; O'Connell, G.; Pappas, B.; Parsons, J.; Petrick, C.; Poignand, B.; Roberts, R.; Ryle, J.; Seymon, A.; Sherry, K.; Skinner, J.; Smith, M.; Strickland, C.; Sutton, S.; Swindell, R.; Tait, H.; Tang, J.; Thomson, A.; Thun, C.; Uppill, B.; Wall, K.; Watkins, J.; Watson, T.; Webber, L.; Whiting, A.; Wilford, J.; Wilson, T.; Wygralak, A.; Albanese, S.; Andersson, M.; Arnoldussen, A.; Baritz, R.; Batista, M. J.; Bel-lan, A.; Birke, M.; Cicchella, C.; Demetriades, A.; Dinelli, E.; De Vivo, B.; De Vos, W.; Duris, M.; Dusza-Dobek, A.; Eggen, O. A.; Eklund, M.; Ernstsen, V.; Filzmoser, P.; Finne, T. E.; Flight, D.; Forrester, S.; Fuchs, M.; Fugedi, U.; Gilucis, A.; Gosar, M.; Gregorauskiene, V.; Gulan, A.; Halami?, J.; Haslinger, E.; Hayoz, P.; Hobiger, G.; Hoffmann, R.; Hoogewerff, J.; Hrvatovic, H.; Husnjak, S.; Janik, L.; Johnson, C. C.; Jordan, G.; Kirby, J.; Kivisilla, J.; Klos, V.; Krone, F.; Kwecko, P.; Kuti, L.; Ladenberger, A.; Lima, A.; Locutura, J.; Lucivjansky, P.; Mackovych, D.; Malyuk, B. I.; Maquil, R.; McLaughlin, M.; Meuli, R. G.; Miosic, N.; Mol, G.; Négrel, P.; O'Connor, P.; Oorts, K.; Ottesen, R. T.; Pasieczna, A.; Petersell, V.; Pfleiderer, S.; Po?avi?, M.; Prazeres, C.; Rauch, U.; Reimann, C.; Salpeteur, I.; Schedl, A.; Scheib, A.; Schoeters, I.; Sefcik, P.; Sellersjö, E.; Skopljak, F.; Slaninka, I.; Šorša, A.; Srvkota, R.; Stafilov, T.; Tarvainen, T.; Trendavilov, V.; Valera, P.; Verougstraete, V.; Vidojevi?, D.; Zissimos, A. M.; Zomeni, Z.

2012-02-01

251

(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

2011-04-01

252

Petrography and geochemistry of lower carboniferous greywacke and mudstones in Northeast Junggar, China: Implications for provenance, source weathering, and tectonic setting  

NASA Astrophysics Data System (ADS)

Northeast Junggar occupies an important position that links East Junggar and Chinese Altai. Numerous magmatic and sedimentary rocks of the Paleozoic in this area recorded the final amalgamation processes of East Junggar and Chinese Altai. This study analyzes the petrological and geochemical characteristics of sandstones and mudstones from the Early Carboniferous Nanmingshui formation in Northeast Junggar. The provenance and tectonic setting of these clastic rocks are discussed. Petrography indicates that the composition and texture maturity of the sandstones are low. The components of the sandstones are mainly volcanic fragments (61-87%), feldspars (9-30%), and monocrystalline quartz (2-18%), with a few polycrystalline quartz and other minerals. Slice observation indicates that the majority of the volcanic fragments of sandstones are basic-intermediate volcanic rocks with a few dacite and felsic plutonic fragments. The detrital modes of the sandstones reflect that these sandstones are derived from undissected arcs. A low to moderate chemical index of alteration and the Al2O3-CaO* + Na2O-K2O diagram reflect a low to moderate weathering degree in the source area. Trace and rare earth element (e.g., La, Th, Hf, Sc, Cr, Co, and Eu) contents and their ratios suggest that the source rocks of the clastic rocks are intermediate-basic rocks with some felsic rocks. Compared with sandstones, the source rocks for mudstones are more felsic. The petrography and geochemistry characteristics of the clastic rocks suggest that the proximal Dulate arc should be the primary source area. Mixing calculations based on REE data suggest that approximately two-thirds of the sandstone fragments are intermediate-basic volcanic rocks. The contents of the major and trace elements, as well as the stratum features, of the clastic rocks manifest that these clastic rocks resemble sedimentary rocks in a back-arc basin. The formation of this back-arc basin is caused by the southward subduction of the Zaysan-Erqis Ocean.

Tao, Huifei; Sun, Shu; Wang, Qingchen; Yang, Xiaofa; Jiang, Lin

2014-06-01

253

X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.  

PubMed

Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan. PMID:16038502

Nakayama, Kenichi; Nakamura, Toshihiro

2005-07-01

254

Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California  

USGS Publications Warehouse

As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

Moore, D.E.; Liou, J.G.; King, B.-S.

1981-01-01

255

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

256

A lower crustal mafic source for the ca. 2550 Ma Qôrqut Granite Complex in southern West Greenland  

NASA Astrophysics Data System (ADS)

The late Neoarchaean Qôrqut Granite Complex is the youngest large igneous intrusion in the Nuuk region in southern West Greenland, where basement is primarily of Eoarchaean and Mesoarchaean age with a tonalite-trondhjemite-granodiorite (TTG) composition. The Qôrqut granite is generally undeformed and it intruded during a prolonged period, starting at ca. 2730 Ma, characterised by crustal reworking, possibly related to syn- or post accretion tectonics or continental collision. We present major and trace element whole rock chemistry and combined U/Pb, Hf and O isotope data from zircon. We obtained a mean zircon U/Pb age of 2547 ± 4 Ma (MSWD = 0.63). Initial ?Hf values range from - 12 to - 18 requiring a long residence time and a rather homogeneous source. Sample averaged zircon ?18O values range from 6.1 ± 0.2‰ to 6.5 ± 0.3/0.7‰ best interpreted with a source region of mainly unweathered mantle derived igneous rocks. Compared to the regional TTG basement, the QGC is characterised by low CaO and Na2O and high K2O, LREE and Rb contents, and a stronger fractionated REE pattern with a negative Eu anomaly. We show that the homogeneous Hf isotope signature of the granite together with its low epsilon value and its pristine oxygen isotope composition are best explained with an Eoarchaean mafic source with a 176Lu/176Hf around 0.015-0.019. Trace element modelling confirms that a mafic source in REE and with an eclogitic residue and with plagioclase as a fractionating phase would generate appropriate melt compositions. Modelling requires residual rutile in the source which constrain the pressures to > ca. 13-18 kbar. Zirconium saturation temperatures suggest magma temperatures in the range 750-850 °C. The obtained P-T conditions suggest a lower crustal source region in a thickened crustal unit consistent with a post or late continental collisional setting.

Næraa, T.; Kemp, A. I. S.; Scherstén, A.; Rehnström, E. F.; Rosing, M. T.; Whitehouse, M. J.

2014-04-01

257

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

258

Petrological and geochemical comparition between the upper and lower rhyolite of the Binchuan basaltic profile,Emeishan LIP succession  

NASA Astrophysics Data System (ADS)

Emeishan basalt is well known worldwide,and it has been well tested from the geochemistry and petrology.However,the eruptional rock sequences is rare reported. Some former work reported that on the top of Emeishan basalt,there is always sit with rhyolite(or felsic-composition,mainly are rhyolite and trachyte ).This work is focusing on newly found rhyolite and trachyte succession at the bottom of Binchuan basalt pofile,and the comparition between the bottom and top felsic-composition of the Binchuan pofile basaltic related succession from petrological and geochemistry points. The bottom rhyolite is lack of phenocryst,and the filling of blowhole is observed quartz only. Otherwise,the phenocryst of the top rhyolite is mainly alkaline-feldspar. The upper layered rhyolite is less sillical rich than the lower part with the content of SiO2 65-70,68-74 respectively. Additionally,the content of TiO2 (0.82-0.87,0.57-0.70),Total Fe2O3(5.15-5.87,2.89-4.88),MgO(2.13-2.64,0.19-0.48),CaO(1.18-1.49,0.13-0.42), P2O5(0.18-0.25,0.02-0.25) of the upper layered rhyolite is more abundant than the lower layer. However,the amount of the Na2O,K2O of both upper and lower rhyolite can not be distinguished clearly as weathering effect suspectively. This may note that the two kinds of rhyolite are formed from different geological process. The upper may due to the crystallization differentiation of the mafic magmas ,while the lower is formed in the result of crust remelting.

Huixin, H.; Yu, W.

2013-12-01

259

Mineralogical effects on the detectability of the postperovskite boundary  

E-print Network

-silicate perovskite (Pv) to postperovskite (pPv) at lowermost mantle pressure-temperature (P - T) conditions may materials transported to the lowermost mantle by subducting slabs. The lower mantle is a multicomponent (MgO, SiO2, FeO, Al2O3, CaO, Na2O, etc.), multiphase (magnesium silicate perovskite (Pv), ferropericlase

Rhoads, James

260

April, 27, 2010 Forms of Energy  

E-print Network

Ash analysis of Huadian oil shale (mass%) SiO2 Al2O3 Fe2O3 CaO MgO TiO2 Na2O K20 52.9 17.74 6.65 14 impact of new turbines will be next to negligible, especially when it comes to atmospheric effects. #12

Toohey, Darin W.

261

Acta Materiala, 2007, 55(10), 3305-3313, doi:10.1016/j.actamat.2007.01.029 SSStttrrruuuccctttuuurrraaalll tttrrraaannnsssfffooorrrmmmaaatttiiiooonnnsss ooofff bbbiiioooaaaccctttiiivvveee ggglllaaassssss 444555SSS555 wwwiiittthhh ttthhheeerrrmmmaaalll  

E-print Network

compositions in the ternary Na2O, SiO2, CaO system with 6 wt.% P2O5 showed that the 45S5 Bioglass® (45 wt.% Si were established. KKeeyywwoorrddss:: Silicates; Bioactive glasses; Crystallization; Differential scanning calorimetry; X-ray diffraction I. Introduction Bioactive glasses are biocompatible and exhibit

Paris-Sud XI, Université de

262

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. PMID:22308383

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

263

Hydride ion as a two-electron donor in a nanoporous crystalline semiconductor 12CaO.7Al2O3.  

PubMed

The 12CaO.7Al2O3 (C12A7) crystal with a nanoporous lattice framework exhibits high electrical conductivity with an activation energy of approximately 1.5 eV when equilibrated in a hydrogen atmosphere above approximately 800 degrees C. The high conductivity is preserved in a quenched state below approximately 600 degrees C with a reduced activation energy of approximately 0.8 eV. Such complex behavior in electrical conductivity is associated with incorporation of hydride ions (H-) in cages of the lattice framework. Electromotive force measurements reveal that the major carrier for the conductivity is electron with a small contribution by proton (H+), ruling out the possibility of direct intercage migration of the H- ion. A combination of these observations with the ab initio calculations leads to the conclusion that the electrons are thermally generated from the H- ion by the dissociation into two electrons and an proton, which is further converted to an OH- ion via reaction with an extraframework oxide ion (O2-). The energy difference between the initial (H- + O2-) and the final (2e- + OH-) states as evaluated by the theoretical calculation is as small as approximately 1 eV, which agrees well with an experimentally obtained enthalpy change, approximately 1.4 eV. Thus, internal equilibration between the extraframework hydrogen and the oxygen species is responsible for the thermal generation of the carrier electron. It is also suggested that the same conductive (2e- + OH-) state is reached by the photoirradiation of H- -containing C12A7. In this case the photoionization of H- forms an electron and an Ho atom, which then forms an OH- ion and another electron with thermal assistance. The persistence of photoinduced conductivity is explained by the slow kinetics of the reverse process at room temperature. PMID:16375369

Hayashi, Katsuro; Sushko, Peter V; Shluger, Alexander L; Hirano, Masahiro; Hosono, Hideo

2005-12-22

264

Luminescence properties of ZrO{sub 2}-CaO eutectic crystals with ordered lamellar microstructure activated with Er{sup 3+} ions  

SciTech Connect

Er{sup 3+}-doped ZrO{sub 2}-CaO eutectic crystals with ordered microstructure have been grown by the laser floating zone method. The microstructure consists of alternating 2 {mu}m thick lamellae of calcia-stabilized zirconia (CaSZ) and CaZrO{sub 3} crystals. Er{sup 3+} enters both phases but at a higher concentration in CaSZ. Due to its higher refractive index, the latter phase acts as a light guiding medium. The optical properties of Er{sup 3+}-doped eutectic, as well as its components, CaSZ and CaZrO{sub 3} crystals, are analyzed. Absorption and emission spectra of CaZrO{sub 3} consist of narrow bands. For this crystal most of the Er{sup 3+} Stark level positions are given. In contrast, the bands for CaSZ are broad, as it corresponds to a defective material. Absorption oscillator strengths, radiative-transition probabilities and emission lifetimes have been measured at different temperatures, between 600 and 4 K. Absorption oscillator strengths are 1.5 times higher for Er{sup 3+} in CaZrO{sub 3} than in CaSZ, while multiphonon deexcitation probabilities are one order of magnitude smaller, with the exception of the lowest energy {sup 4}I{sub 13/2}{r_arrow}{sup 4}I{sub 15/2} emission, which presents the maximum quantum efficiency in both phases. {copyright} {ital 1997} {ital The American Physical Society}

Merino, R.I.; Pardo, J.A.; Pena, J.I.; de la Fuente, G.F.; Larrea, A.; Orera, V.M. [Instituto de Ciencia de Materiales de Aragon, Consejo Superior de Investigaciones Cientificas-Universidad de Zaragoza, 50009 Zaragoza (Spain)] [Instituto de Ciencia de Materiales de Aragon, Consejo Superior de Investigaciones Cientificas-Universidad de Zaragoza, 50009 Zaragoza (Spain)

1997-11-01

265

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

266

Characteristics of chemical weathering and water-rock interaction in Lake Nyos dam (Cameroon): Implications for vulnerability to failure and re-enforcement  

NASA Astrophysics Data System (ADS)

For the first time, comprehensive study of hydrogeochemistry of water seeps, role of chemical weathering on dam failure, estimation of minimum width of dam to resist failure and simulation of changes in dissolved ions and secondary mineral was conducted on the Lake Nyos dam. The salient results and conclusions were; the dam spring water represented a mixture of 60-70% rainwater and 30-40% Lake water (from 0 to -40 m). The chemistry of the observed waters was Ca-HCO3 for rainwater, Ca-Mg-HCO3 in boreholes, and Mg-Ca-HCO3- for spring water. The relative rate at which ions dissolved in water was HCO3- > Mg2+ > Ca2+ > Na+ > SiO2 > K+ > NO3- > SO42- > Cl-. Weathering of rocks resulted in the formation of clay minerals such as kaolinite and smectite. Relative mobility of elements compared to Alumina (Al2O3) indicated that in monzonites there was a loss of CaO, Na2O, K2O, P2O5 and gain of SiO2, Fe2O3, TiO2, MnO and MgO, while in basalts there was a loss of SiO2, Fe2O3, Ca2O, NaO, MgO and gain of TiO2, K2O and P2O5. Values of chemical alteration index that ranged from 49 to 82 suggest a weak to intermediate categories of chemical weathering that occurred at a rate of 5.7 mm/year. Paired to that rate, which suggests that the dam is not vulnerable to failure at the previously thought time scale, some other processes (physical weathering, secondary mineral formation and lake overflow) can cause instant failure. Hydrostatic pressure of 1.6 GN generated by Lake water can be supported only when the width of the dam is greater than 19 m. PHREEQC-based simulation for 10 years indicates decoupling of Ca and Mg, and Na and Mg. Multidisciplinary monitoring of the dam is advocated.

Fantong, Wilson Y.; Kamtchueng, Brice T.; Yamaguchi, Kohei; Ueda, Akira; Issa; Ntchantcho, Romaric; Wirmvem, Mengnjo J.; Kusakabe, Minoru; Ohba, Takeshi; Zhang, Jing; Aka, Festus T.; Tanyileke, Gregory; Hell, Joseph V.

2015-01-01

267

Archaean multiphase Porosozero sanukitoid pluton of the Kola region: petrological, geochronological and geochemical data  

NASA Astrophysics Data System (ADS)

The Porosozero sanukitoid intrusion is located in the greenstone belt of the Kolmozero-Voronja, north-eastern part Fennoscandian (Baltic) Shield. The Porosozero multiphase pluton was formed as a result of the 4 magmatic phases during the period ca. 60 million years. The main phase is represented by a differentiated series of gabbro-diorite - quartz monzodiorite - granodiorite - granite. The zircon TIMS ages of granodiorite and quartz monzodiorites are 2733±6 Ma and 2734±4 Ma, respectively. The second phase is composed of leucogranites formed during intrusion of the residual melt portion from intracrustal source. The age of zircon from leucogranite is 2712±6 Ma. The third phase is represented by the lamprophyre dykes with the zircon age 2680±8 Ma. The late pegmatite veins were formed during the fourth final phase. The volume relationships between the gabbro-diorite, quartz monzodiorites, granodiorites and granites are 5:55:27:13, respectively. The medium weighted composition of the initial melt, calculated from the rock compositions of the first phase is andesite (wt.%): SiO2 = 61.53, TiO2 = 0.58, Al2O3 = 15.74, Fe2O3 = 3.75, FeO = 3.07, MnO = 0.10, MgO = 3.06, CaO = 5.83, Na2O = 3.78, K2O = 2.37. The compositional variation is the result of fractional crystallization. The last magmas may have experienced some crustal contamination. All rocks of the first phase are enriched in Ba (500-800 ppm), Sr (450-700 ppm), K2O (1.8-3.2 wt. %), P2O5 (0.15-0.35), LREE [(La/Yb)N=15-23] and contain high concentrations of Cr (150-400 ppm) and Ni (60-140 ppm), possess high mg# values (0.45-0.65), and show a negative Nb-Ta anomaly. Sm-Nd isotopic data for sanukitoids indicate their formation from a mantle source enriched in LILE and LREE with ?Nd (2740) = +1.02 - +0.36, T(DM)=2.9-2.8 Ga. The Porosozero polyphasic pluton is similar to worldwide Archaean and Phanerozoic magmatic sanukitoide series. The Porosozero pluton formation is determined by the processes of mantle-crust interaction in suprasubduction conditions within the active continental margins. The high content of Ag and Au in rocks Porosozero pluton provides a general perspective for precious metals.

Kudryashov, Nikolai; Mokrushin, Artem; Petrovsky, Michail; Elizarov, Dmitry

2013-04-01

268

Curriculum Vitae Hui Cao 1 Hui Cao Aug. 22, 2013  

E-print Network

and B. Redding, "Multimode Optical Fiber Spectrometer", International patent application. Book and book-loss modes in deformed microdisks, Chapter 4 in "Trends in Nano- and Micro-Cavities," ed. O'Dae Kwon ultralow-loss modes in deformed microdisks", Chapter 4 in "Trends in Nano- and Micro-Cavities", ed. O' Dae

Cao, Hui

269

Probing the role of P dbnd O stretching mode enhancement in nerve-agent sensors: Simulation of the adsorption of diisopropylfluorophosphate on the model MgO and CaO surfaces  

NASA Astrophysics Data System (ADS)

The interactions of diisopropylfluorophosphate (DFP) with model MgO and CaO surfaces have been investigated using density functional (DFT) and Møller-Plesset second order perturbation techniques. The geometries were fully optimized at the DFT level. The calculated interaction energies and the corresponding thermodynamic properties show that DFP is physisorbed on these two model oxide surfaces and adsorption on the MgO surface is stronger. Analyses of the calculated IR and Raman spectra point to the enhancement of the P dbnd O stretching mode with respect to the isolated DFP and this property could be used to detect nerve-agents using surface-enhanced Raman spectroscopy.

Kolodziejczyk, Wojciech; Majumdar, D.; Roszak, Szczepan; Leszczynski, Jerzy

2007-12-01

270

O(-) identified at high temperatures in CaO-based catalysts for oxidative methane dimerization  

NASA Technical Reports Server (NTRS)

A technique called charge-distribution analysis (CDA) is employed to study mobile charge carriers in the oxidation catalysts CaO, CaO with 11 percent Na2O, and CaO with 10 percent La2O3. A threshold temperature of about 550-600 C is identified at which highly mobile charge carriers are present, and the CDA studies show that they are O(-) states. The present investigation indicates the usefulness of CDA in catalysis research with pressed powder samples and gas/solid reactions.

Freund, F.; Maiti, G. C.; Batllo, F.; Baerns, M.

1990-01-01

271

Leaching of silica bands and concentration of magnetite in Archean BIF by hypogene fluids: Beebyn Fe ore deposit, Yilgarn Craton, Western Australia  

NASA Astrophysics Data System (ADS)

The ~2,752-Ma Weld Range greenstone belt in the Yilgarn Craton of Western Australia hosts several Fe ore deposits that provide insights into the role of early hypogene fluids in the formation of high-grade (>55 wt% Fe) magnetite-rich ore in banded iron formation (BIF). The 1.5-km-long Beebyn orebody comprises a series of steeply dipping, discontinuous, <50-m-thick lenses of magnetite-(martite)-rich ore zones in BIF that extend from surface to vertical depths of at least 250 m. The ore zones are enveloped by a 3-km-long, 150-m-wide outer halo of hypogene siderite and ferroan dolomite in BIF and mafic igneous country rocks. Ferroan chlorite characterises 20-m-wide proximal alteration zones in mafic country rocks. The magnetite-rich Beebyn orebody is primarily the product of hypogene fluids that circulated through reverse shear zones during the formation of an Archean isoclinal fold-and-thrust belt. Two discrete stages of hypogene fluid flow caused the pseudomorphic replacement of silica-rich bands in BIF by Stage 1 siderite and magnetite and later by Stage 2 ferroan dolomite. The resulting carbonate-altered BIF is markedly depleted in SiO2 and enriched in CaO, MgO, LOI, P2O5 and Fe2O3(total) compared with the least-altered BIF. Subsequent reactivation of these shear zones and circulation of hypogene fluids resulted in the leaching of existing hypogene carbonate minerals and the concentration of residual magnetite-rich bands. These Stage 3 magnetite-rich ore zones are depleted in SiO2 and enriched in K2O, CaO, MgO, P2O5 and Fe2O3(total) relative to the least-altered BIF. Proximal wall rock hypogene alteration zones in mafic igneous country rocks (up to 20 m from the BIF contact) are depleted in SiO2, CaO, Na2O, and K2O and are enriched in Fe2O3(total), MgO and P2O5 compared with distal zones. Recent supergene alteration affects all rocks within about 100 m below the present surface, disturbing hypogene mineral and the geochemical zonation patterns associated with magnetite-rich ore zones. The key vectors for identifying hypogene magnetite-rich Fe ore in weathered outcrop include textural changes in BIF (from thickly to thinly banded), crenulated bands and collapse breccias that indicate volume reduction. Useful indicators of hypogene ore in less weathered rocks include an outer carbonate-magnetite alteration halo in BIF and ferroan chlorite in mafic country rocks.

Duuring, Paul; Hagemann, Steffen

2013-03-01

272

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

273

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

274

Glass and mineral analyses from first deposits of Peach Spring Supereruption (SW USA) illuminate initial tapping of a zoned magma chamber  

NASA Astrophysics Data System (ADS)

The Peach Spring supereruption (18.78±0.02 Ma) was sourced from Silver Creek caldera in the southern Black Mountains, Arizona (Ferguson et al. in press). The resulting ignimbrite, the Peach Spring Tuff (PST), blanketed >32,000 km2 of Arizona, California, and Nevada (Buesch, 1993). Underlying the ignimbrite is a thin (? 1m thick) basal layered deposit that consists of texturally distinct layers 1a-e (Valentine et al. 1989) and is present up to ~100 km from the source caldera. Basal layered deposits contain the first material erupted during the PST supereruption, preceding the main eruption event. Petrography and geochemistry of minerals and pumice clasts from basal layered deposits collected ~15-100 km from the caldera, combined with a survey of glass and crystal compositions from both outflow and basal deposits, permit (1) comparisons with the overlying ignimbrite, and (2) insights into the initial stages of the supereruption and extraction of magma from the chamber. Pumice clasts from a pumice-rich layer (1a2) of the basal deposit were characterized by LA-ICPMS and SEM. Unaltered glass has a uniform high-Si rhyolite composition (76.7% SiO2, 13.0% Al2O3, 3.6% Na2O, 5.3% K2O, 0.6% FeO, <0.1% MgO, 0.6% CaO, 0.1% TiO2). Mildly altered glass is similar but has lower Na2O and higher K2O. Pumice clasts are relatively crystal poor (<10% phenocrysts) with an assemblage dominated by sanidine (~Or55Ab43An2), with lesser plagioclase (~Ab73An19Or8), minor hornblende and biotite, and accessory magnetite, sphene, zircon, chevkinite, and apatite; no quartz was identified. Initial LA-ICPMS results for glass reveal REE patterns with large negative Gd (0.21: i.e. U-shaped REE pattern) and Eu (0.31) anomalies, very low Ba and Sr (?10 ppm), and high Rb (~250 ppm). These compositions are essentially identical to those of the most common pumice from distal outflow ignimbrite, but very different from crystal-rich (>30%) trachyte pumice that dominates the intracaldera fill and is present at the tops of proximal outflow sections (Pamukcu et al. in press). A broader survey by EMP of minerals and glass shards from basal layered deposits and outflow ignimbrite (Buesch, 1993 and unpublished data, 1992) support the general conclusion that distal outflow is dominated by high-Si rhyolite, but demonstrate that trachyte is present throughout ignimbrite and basal deposits. Although SiO2 concentration is dominantly ~76-78 wt%, a small but persistent population ranges from ~66-72 wt%. Likewise, 6% (in layer 1a2) to 40% of all plagioclase in basal and outflow deposit samples is relatively calcic (An>27), indicating trachyte origin. The above data (1) confirm the existence of two compositions of erupted magma (phenocryst-poor, high-Si rhyolite, crystal-rich trachyte); (2) demonstrate that the initial eruption (basal layer) tapped the same magmas as the ignimbrite; and (3) reveal that, although rhyolite dominates outside the caldera, trachyte like that in intracaldera deposits was also tapped throughout the eruption. These relations are consistent with eruption from a vertically stratified magma chamber with trachyte (cumulate?) beneath rhyolite, but indicate that either chamber stratification was imperfectly developed or some magma from deeper levels was entrained throughout the eruption.

Mccracken, R. G.; Miller, C. F.; Buesch, D.; Gualda, G. A.; Covey, A.

2012-12-01

275

Enhanced stability of CaO and/or La2O3 promoted Pd/Al2O3 egg-shell catalysts in partial oxidation of methane to syngas.  

PubMed

An egg-shell Pd/Al2O3 catalyst showed higher activity than a regular Pd/Al2O3 catalyst in the partial oxidation of methane to syngas, but a common problem of this reaction is the catalyst deactivation on stream. We attempted to modify the egg-shell catalyst via impregnation with some metal oxide additives. Although the addition of MgO did not show any beneficial effect, the addition of CaO and/or La2O3 significantly improved the stability due to the suppression of carbon deposition and phase transformation of the Al2O3 support. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and thermogravimetric analysis (TGA). PMID:23860276

Wang, Jinlong; Yu, Hongbo; Ma, Zhen; Zhou, Shenghu

2013-01-01

276

Characterization of 12CaO x 7Al2O3 doped indium tin oxide films for transparent cathode in top-emission organic light-emitting diodes.  

PubMed

12CaO x 7Al2O3, insulator (C12A7) doped indium tin oxide (ITO) (ITO:C12A7) films were fabricated using a radio frequency magnetron co-sputtering system with ITO and C12A7 targets. The qualitative and quantitative properties of ITO:C12A7 films, as a function of C12A7 concentration, were examined via X-ray photoemission spectroscopy and synchrotron X-ray scattering as well as by conducting atomic force microscopy. The work function of ITO:C12A7 (1.3%) films of approximately 2.8 eV obtained by high resolution photoemission spectroscopy measurements make them a reasonable cathode for top-emission organic light-emitting diodes. PMID:24245291

Jung, Chul Ho; Hwang, In Rok; Park, Bae Ho; Yoon, Dae Ho

2013-11-01

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

2012-07-15

278

Multi-component diffusion between molten SiO2 inclusions and surrounding felsic melt in an indochinite: Tektites as natural laboratories  

NASA Astrophysics Data System (ADS)

Tektites are natural glasses thought to have formed as a result of melting and quenching of distally ejected terrestrial material upon hypervelocity (>11 km/s) impact on Earth. Some tektites contain inclusions of lechatelierite (nearly pure SiO2 glass; 99-100 wt. % SiO2), generally thought to be the amorphous relicts of partially digested quartz grains (Koeberl, 1994). Electron and ion microprobe analyses of major and minor elements were performed on transects between lechatelierite inclusions and the surrounding felsic glass in an indochinite (sample from Newman et al., 1995). The surrounding glass is peraluminous with an average composition of 73.4 wt.% SiO2, 12.8 wt.% Al2O3, 4.5 wt. % FeO, 2.3 wt.% K2O, and < 2 wt.% (each) CaO, MgO, Na2O, and TiO2. The boundary between the lechatelierite and felsic glass is broad (~30 ?m), with complex concentration profiles reflecting diffusion between the two melts at high temperatures (>2200 °C for formation of lechatelierite; Bunch et al., 2012) prior to quenching. Although all components except SiO2 are pinned to near zero at the same point at the lechatelierite end of the profiles, the shapes of the oxide concentration profiles differ, with Ca and Mg falling off from their far-field values first, followed in order by Fe, Ti, Al, Na, and K. K has apparently propagated the longest distance, diffusing faster than other components from the surrounding melt toward the lechatelierite. Furthermore, concentration profiles of K2O systematically increase, reach a maximum, then decrease closest to lechatelierite, indicating uphill diffusion of K against its concentration gradient. All concentration profiles are asymmetric, becoming steepest towards the most silicic portions of the interdiffusion zone approaching lechatelierite, likely due to the sharp compositional contrast between matrix glass and inclusions. Sato (1974) observed similar alkali enrichment in coronas around quartz xenocrysts in basalt and andesite, where K, and to a lesser degree Na, diffused against their concentration gradients. The uphill diffusion of alkalis in corona glass surrounding quartz was interpreted by Sato (1974) with a diffusion model assuming non-ideality of alkali elements in silicate melt, in which diffusion occurs according to the chemical potential gradient of each species. Preliminary calculations using the MELTS (Ghiorso and Sack, 1995) activity-composition model to transform the composition profiles across lechatelierite and felsic glass into chemical potential profiles (at 2200 °C) indicate that all components, including K2O, diffuse down their own chemical potential gradients. We will investigate these phenomena further in attempt to model the observed profiles. A deeper understanding of this problem may inform the factors controlling diffusion coefficients in silicate melts derived from crustal material, as well as the thermal histories of tektites. Bunch T.E. et al. (2012) P NATL ACAD SCI 109:1903-1912 Ghiorso M.S., Sack R.O. (1995) CONTRIB MINERAL PETR 119:197-212 Koeberl C. (1994) GEOL S AM S 133-151 Newman S. et al. (1995) LPS XXVI 26:1039-1040 Sato H. (1974) CONTRIB MINERAL PETROL 50:49-64

Macris, C. A.; Eiler, J. M.; Asimow, P. D.; Stolper, E. M.

2013-12-01

279

Melt inclusions and origin of granite in migmatitic granulites from the Kerala Khondalite Belt, Southern India  

NASA Astrophysics Data System (ADS)

Both glassy and crystallized melt inclusions (MI) occur in garnet in metapelitic granulites from the Kerala Khondalite Belt. These rocks were metamorphosed and partially melted at UHT conditions during the Pan-African event, and MI represent droplets of the anatectic melt, originated by dehydration melting of biotite and trapped by garnet growth at supersolidus conditions. An extensive ESEM-BSE mapping study, along with EMPA analysis and re-heating experiments, has been carried out to characterize these anatectic MI. The inclusions range from 4 to 35 ?m in diameter and occur as clusters in garnets. In spite of the long time it took for these rocks to cool below 350 °C (at least 60 m.y.), different degrees of crystallization were observed in the same cluster, ranging from totally crystallized to totally glassy. The crystallized MI are referred to as "nanogranites" (Cesare et al., 2009) and always contain quartz, Mg-rich biotite (XFe=0.23) and two feldspars in a fine-grained polycrystalline aggregate. Based on microstructural evidence, biotite crystallized as first phase, preferentially on the walls of the MI, while quartz and feldspars crystallized later, often forming graphic intergrowths and/or melt pseudomorph-like structures (? 50 nm) similar to coarser structures (? tens of microns scale) observed in the host rocks. The glassy inclusions are rare (about 15% of the total) and smaller in size (?15 ?m in diameter) compared to the crystallized nanogranite MI. Both MI types often show negative crystal-shape and contain trapped crystalline phases that are accessories in the host rock, including rutile, titanite, zircon, apatite and Zn-rich spinel. Partially crystallized MI have been also recognized, containing an amorphous phase identified as a residual melt Where Cl and Ca are preferentially partitioned. Re-heating experiments in a HT hearing stage succeeded in re-homogenizing the nanogranite inclusions. EMP data on 40 re-homogenized MI show an average SiO2=73 wt%, K2O =6.7 wt%, Na2O =1 wt% and CaO <1 wt%. EMP analyses on the primary glassy inclusions in not re-heated samples provide similar compositions, while the differentiated melt in partially crystallized MI has higher CaO content and lower K2O content. The EMP characterization therefore confirms the work hypothesis that the different types of MI had the same original composition, except for the different trapped accessories, and that melt in partially crystallized MI is the result of a differentiation of the original trapped melt via crystal fractionation. The low Na content of melt in inclusions is consistent with the scarcity or absence of plagioclase in the melanosome of the studied samples, and with the UHT conditions at which the rocks melted. In fact, in the Q-Ab-An diagram melts plot far from the haplogranitic minima. Our results show that MI studies represent a powerful novel approach in the petrology of crustal melting and S-type granite genesis, and highlight the potential pitfalls of assuming anatectic melt as having a minimum melt composition. References Cesare, B., Ferrero, S., Salvioli-Mariani, E., Pedron, D., Cavallo, A., 2009. Nanogranite and glassy inclusions: the anatectic melt in migmatites and granulites. Geology 37, 627-630.

Ferrero, Silvio; Cesare, Bernardo; Salvioli Mariani, Emma; Cavallo, Andrea

2010-05-01

280

Vibrational features of phospho-silicate glasses: Periodic B3LYP simulations  

NASA Astrophysics Data System (ADS)

B3LYP periodic calculations with double-? polarised basis set using C RYSTAL06 code have been run on a bioactive phospho-silicate glass similar in composition to Bioglass ® 45S5 (46.1 SiO 2, 24.4 Na 2O, 26.9 CaO and 2.6 P 2O 5 mol%) and a phosphorous-free soda-lime glass (49.5 SiO 2, 24.2 Na 2O and 26.4 CaO mol%). Initial structures have been obtained through a melt-quench process by classical molecular dynamics techniques and the effect of phosphorous on the glass network structure and dynamics have been assessed by B3LYP vibrational spectra.

Corno, Marta; Pedone, Alfonso

2009-07-01

281

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

282

Ageing of pulsed-laser-deposited bioactive glass films  

Microsoft Academic Search

Bioactive glasses are osteoinductive biomaterials of great interest for medical applications as filler material in bone defects and as coating of implants.Bioactive glass thin films have been deposited on silicon plates by ArF laser ablation of silica-based glass targets (53% SiO2, 23% Na2O, 20% CaO, 4% P2O5). Ablation experiments have been carried out in vacuum (10?4mbar) and in a reactive

P González; J Serra; S Liste; S Chiussi; B León; M Pérez-Amor

2002-01-01

283

Chemical compositions of impact melt breccias and target rocks from the Tenoumer impact crater, Mauritania  

Microsoft Academic Search

The impact melt breccias from the Tenoumer crater (consisting of a fine-grained intergrowth of plagioclase laths, pyroxene crystals, oxides, and glass) display a wide range of porosity and contain a large amount of target rock clasts.Analyses of major elements in impact melt rocks show lower contents of SiO2, Al2O3, and Na2O, and higher contents of MgO, Fe2O3, and CaO, than

Giovanni Pratesi; Marco Morelli; Angelo Pio Rossi; Gian Gabriele Ori

2005-01-01

284

Biological performance of boron-modified bioactive glass particles implanted in rat tibia bone marrow  

Microsoft Academic Search

The aim of the present study was to characterize the neoformed bone tissue around boron-modified bioactive glass particles implanted in rat tibia bone marrow by histologic, histomorphometric and microchemical evaluation. Melt-derived glasses were prepared from a base 45S5 bioactive glass of nominal composition (45% SiO2, 24.5% CaO, 24.5% Na2O and 6% P2O5 in wt%). The glass composition was modified by

Alejandro A. Gorustovich; José M. Porto López; María B. Guglielmotti; Rómulo L. Cabrini

2006-01-01

285

Fluoride-containing bioactive glasses: Surface reactivity in simulated body fluids solutions  

Microsoft Academic Search

The issue of the contribution of the addition of F to glass bioactivity is not well resolved. This work reports on the surface reactivity in different solutions (DMEM and Tris) for some potentially bioactive glasses based on the composition of 45S5 glass, in which CaF2 is substituted alternately for (part of) CaO and Na2O. The reactivity of F-containing glasses has

G. Lusvardi; G. Malavasi; L. Menabue; V. Aina; C. Morterra

2009-01-01

286

Osteoblast response to bioactive glasses in vitro correlates with inorganic phosphate content  

Microsoft Academic Search

Inorganic phosphate (Pi) is a physiological regulator of osteoblasts and chondrocytes, suggesting that phosphate may contribute to the biological response of these cells to bioactive glasses like Bioglass® 45S5, which is composed of 45% SiO2, 24.5% CaO, 24.5% Na2O, and 6% P2O5. We investigated the effect of varying the Pi content of bioactive glass disks (0%, 3%, 6% and 12%

S. Lossdörfer; Z. Schwartz; C. H. Lohmann; D. C. Greenspan; D. M. Ranly; B. D. Boyan

2004-01-01

287

Low-pressure differentiation of tholeiitic lavas as recorded in segregation veins from Reykjanes (Iceland), Lanzarote (Canary Islands) and Masaya (Nicaragua)  

NASA Astrophysics Data System (ADS)

Segregation veins are common in lava sheets and result from internal differentiation during lava emplacement and degassing. They consist of evolved liquid, most likely replaced by gas-filter pressing from a ˜50% crystallised host lava. Pairs of samples, host lavas and associated segregation veins from the Reykjanes Peninsula (Iceland), Lanzarote (Canary Islands) and the Masaya volcano (Nicaragua) show extreme mineralogical and compositional variations (MgO in host lava, segregation veins and interstitial glass ranges from 8-10 wt%, 3-6 wt%, and to less than 0.01 wt%, respectively). These samples allow the assessment of the internal lava flow differentiation mechanism, since both the parental and derived liquid are known in addition to the last magma drops in the form of late interstitial glasses. The mineralogical variation, mass-balance calculated from major- and trace element composition, and transitional metal partition between crystals and melts are all consistent with fractional crystallisation as the dominant differentiation mechanism. The interstitial glasses are highly silicic (SiO2 = 70-80 wt%) and represent a final product of high-degree (75-97%) fractional crystallisation of olivine tholeiite at a pressure close to one atmosphere. The tholeiitic liquid-line-of-decent and the composition of the residual melts are governed by the K2O/Na2O of the initial basaltic magma. The granitic minimum is reached if the initial liquid has a high K2O/Na2O whereas trondhjemitic composition is the final product of magma with low initial K2O/Na2O.

Martin, E.; Sigmarsson, O.

2007-11-01

288

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

289

Trondhjemitic melts produced by in-situ differentiation of a tholeiitic lava flow, Reykjanes Peninsula, Iceland.  

NASA Astrophysics Data System (ADS)

How the continental crust began to form early in Earth's history is unconstrained. However, it is reasonable to presume that higher heat flow in the past, resulted in more frequent interaction of mantle plumes and mid- oceanic ridges. If true, then Iceland could be a good analogue for processes occurring on Earth at its youth stage. This is supported by the relatively high abundance of silicic rocks in Iceland but their rarity on other oceanic hot spots. The origin of Icelandic silicic rocks has been a subject of a lively debate but has been shown to be principally formed by partial melting of hydrothermally altered basaltic crust. However, in rare cases, their origin by fractional crystallization from mantle derived basalts is suggested. Segregation veins in lava flows frequently contain interstitial glasses of silicic compositions. Moreover, they allow an exceptional overview of the fractional crystallization mechanism. These veins form by gas filter pressing during cooling and degassing of solidifying lava flows, after approximately 50% fractional crystallization of anhydrous minerals. Pairs of samples, host lava and associated segregation veins, from Reykjanes Peninsula (Iceland), Lanzarote (Canary Island) and Masaya's volcano (Nicaragua), allow the assessment of a near-complete fractional crystallization of olivine tholeiitic basalt at pressure close to one atmosphere. Interstitial glass patches in segregation veins represent the final product of this process (80 97 % of fractional crystallization). These ultimate liquids are of granitic composition in the case of Lanzarote and Masaya but overwhelmingly trondhjemitic at Reykjanes. It appears that the initial K2O/Na2O of the basaltic liquid controls the evolution path of the residual liquid composition produced at pressure close to 0.1 MPa (1 bar). Granitic liquids are generated from basalts of high initial K2O/Na2O whereas low initial K2O/Na2O leads to trondhjemitic compositions. The trondhjemitic composition of glass patches from the segregation vein at Reykjanes Peninsula differs from Icelandic silicic magmas but is close to those of the Archaean TTG (trondhjemite-tonalite-granodiorite) suite. Taken at face value, this may imply that fractional crystallisation of olivine tholeiites (low K2O/Na2O) could have played a significant role during the formation of the early continental crust. At higher pressure, where garnet is on liquidus, fractional crystallisation can generate the observed trace element patterns observed in TTG. The progressive cooling, crystallization and degassing of basaltic magma ocean, thought to have been prevailing during the Hadean, could have led to high degree of fractional crystallization producing significant volume of trondhjemitic melts that because of its buoyancy contributed to the formation of the earliest continental crust.

Martin, E.; Sigmarsson, O.

2006-12-01

290

Search for solid conductors of Na/+/ and K/+/ ions - Five new conductors  

NASA Technical Reports Server (NTRS)

Five new conductors of positive Na and K ions, for use as separators in high energy secondary batteries, have been discovered. They include: (1) the pyrochlores NaTaWO6 and NaTa2O5F; (2) the bcc form of NaSbO3; and (3) the niobates 2Na2O-3Nb2O5 and 2K2O-3Nb2O5, with the alkali ions probably in open layers of the completely determined structure. On the basis of approximately 40 structure types, generalizations have been made regarding the relation between structure and ionic transport.

Singer, J.; Kautz, H.; Fielder, W.; Fordyce, J.

1975-01-01

291

Chemical Durability of Dicor and Fluorocanasite-based Glass-ceramics  

Microsoft Academic Search

Fluorocanasite (Al2O3-CaO-F-K2O-Na 2O-SiO2) glass-ceramics exhibit fracture toughness values of up to 5.0 MPa·m1\\/2. However, their chemical durability is not adequate for dental applications. The objective of this study was to test the hypothesis that an increased concentration of Al2O3 can increase the chemical durability of fluorocanasite-based glass-ceramics. Glass frits containing 2 wt% (CAN2), 5 wt% (CAN5), and 10 wt% Al2O

K. J. Anusavice; N.-Z. Zhang

1998-01-01

292

Glass-to-metal seals comprising relatively high expansion metals  

NASA Technical Reports Server (NTRS)

A glass suitable for glass-to-metal seals that has a resistance to attack by moisture and a high coefficient of linear thermal expansion is introduced. Linear expansion covers the range from 12 to 14 x 10 to the minus 6 C between room temperature and 500 C. The glass is essentially composed of, by molar percent, about 9% of K2O, about 10% of Na2O, about 70% of SiO2, about 6% Al2O3, and about 5% of MgO.

Hirayama, C. (inventor)

1974-01-01

293

Carboniferous-Permian extensive magmatism in the West Junggar, Xinjiang, northwestern China: its geochemistry, geochronology, and petrogenesis  

NASA Astrophysics Data System (ADS)

Located between the Tarim, Kazakhstan, and Siberian plates, the West Junggar terrane is a key component of the Paleozoic Central Asian Orogenic Belt (CAOB) with widespread late Paleozoic igneous rocks. In this paper, we report petrological, geochronological, and geochemical data for selected granitoids from the West Junggar. Based on geochronology, the I-type and A-type granites were formed predominantly at 347.9-319.0 Ma and at 321.4-290 Ma respectively. The early-stage I-type granites are characterized by low SiO2, Na2O, and K2O contents with Na2O/K2O ratios > 1 and are metaluminous to weakly-peraluminous. They are enriched in large ion lithophile elements (LILE) and in Sr but depleted in high field strength elements (HFSE), with (87Sr/86Sr)i ratios of 0.7028-0.7044 and ?Nd(t) values varying from + 5.74 to + 7.76. The late-stage I-type granites are characterized by low contents of Si2O and K2O and relatively high contents of FeO, MgO, and Na2O with Na2O/K2O ratios > 1, and are metaluminous to weakly-peraluminous. They are also enriched in LILE and depleted in HFSE with Eu anomalies, (87Sr/86Sr)i ratios of 0.703-0.704, and ?Nd(t) values varying from + 5.20 to + 8.00. The A-type granites have high SiO2 contents, high K calc-alkaline-shoshonitic affinities, positive ?Nd(t) values (5.76-7.77), and low initial 87Sr/86Sr ratios (0.7017-0.7045). Along with reported Sr-Nd isotopic data and regional geologic evidence the Early Carboniferous I-type granites are interpreted as products of partial melting of trapped oceanic crust triggered by underplated mantle wedge-derived basaltic magma; the Late Carboniferous-Early Permian I-type granites as derivatives of partially melted trapped oceanic crust; and the A-type granites as resulting from partial melting of trapped juvenile oceanic crust in an extensional regime. The A-type granitoids with high positive ?Nd(t) values and high Zr-saturation temperatures could be genetically related to a mantle plume or a regional-scale mantle upwelling in the CAOB.

Gao, Rui; Xiao, Long; Pirajno, Franco; Wang, Guo-can; He, Xin-xing; Yang, Gang; Yan, Sheng-wu

2014-09-01

294

Influence of the non-bridging oxygen groups on the bioactivity of silicate glasses  

Microsoft Academic Search

The effect of the composition and bonding configuration of the bioactive silica-based glasses on the initial stage in vitro bioactivity is presented. Information of the IR active Si–O groups of glass in the system SiO2–P2O5–CaO–Na2O–K2O–MgO–B2O3 was obtained by fourier transform Infrared (FTIR) spectroscopy. Two different bands associated to non-bridging oxygen stretching vibrations (Si–O–1NBO and Si–O–2NBO) and a gradual shifting of

J. Serra; P. González; S. Liste; S. Chiussi; B. León; M. Pérez-Amor; H. O. Ylänen; M. Hupa

2002-01-01

295

Study of natural glasses through their behaviour as membrane electrodes  

USGS Publications Warehouse

THE low-temperature chemical alteration of natural glass occurs in two stages: an initial stage in which it remains glassy but absorbs as much as 6 per cent water1, and a final stage in which devitrification to clay minerals, with release of silica, occurs2,3. During the first stage the composition of the glass may change, with gain of K2O and water and loss of Na2O (Smith, R. L., personal communication). This change is due to ion exchange. ?? 1962 Nature Publishing Group.

Truesdell, A.H.

1962-01-01

296

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

297

Petrology and geochemistry of Mesozoic granitic rocks from the Nansha micro-block, the South China Sea: Constraints on the basement nature  

NASA Astrophysics Data System (ADS)

There are several micro-blocks dispersed in the South China Sea (SCS), e.g., Xisha-Zhongsha block, Nansha block and Reed-Northeastern Palawan block, etc., but detailed petrological constraints on their basement nature were previously lacking. The magmatic ages for granitic rock samples from two dredge stations in the Nansha micro-block vary from 159 to 127 Ma, which are comparable to magmatic activities occurred in the northern margin (Pearl river mouth), HongKong and East China. Petrographic characteristics, major-, trace element and Sr-Nd isotopic data of nine samples from two dredged station performed in the Nansha micro-block, the SCS, are reported. Petrographically, these granitic rocks can be divided into two groups which underwent a complex history of magmatic process, i.e., tonalitic rock (Group I) and monzogranitic rock (Group II). The Rittmann index ( ?) for these rocks (1.9-3.1) suggest that they belong to calc-alkaline rocks. Group I rocks which is of typical I-type, have higher contents of TiO 2, Al 2O 3, FeO, MgO, CaO, Na 2O and P 2O 5, but lower values of SiO 2 and K 2O, when compared with those of Group II with I-type characteristics. Group I rocks are produced by partial melting of older Precambrian basement with the variable influence of mantle-derived magma which results from the interaction of released fluids from the subducted slab and the overlying mantle wedge in a general convergent margin setting, and Group II rocks result from partial melting of lower crustal basic rocks (amphibolite) and/or further partial melting of the Group I rocks associated with the variable influence from the underplating mantle-derived magma resulting from lithospheric extensional regime. Both Groups I and II have undergone assimilation and fractional crystallization (AFC) processes during its petrogenesis. This study therefore demonstrates that there exists a continental basement within micro-blocks in the South China Sea, and further supports the idea that a Middle Jurassic to Mid-Cretaceous subduction zone existed across the temporary Taiwan, Palawan to Southern Vietnam, which was associated with westward to northestward convergence of the Pacific Plate during Late Mesozoic. We suggest that this subduction zone may have been connected with the paleo-Pacific plate subduction zone offshore eastern China during Mesozoic era. This study provides petrologic data for the pre-Cenozoic tectonic evolution of the South China Sea.

Yan, Quanshu; Shi, Xuefa; Liu, Jihua; Wang, Kunshan; Bu, Wenrui

2010-01-01

298

Aklimaite, Ca4[Si2O5(OH)2](OH)4 · 5H2O, a new natural hydrosilicate from Mount Lakargi, the Northern Caucasus, Russia  

NASA Astrophysics Data System (ADS)

A new mineral aklimaite, Ca4[Si2O5(OH)2](OH)4 · 5H2O, has been found near Mount Lakargi, Upper Chegem caldera, Kabardino-Balkaria, the Northern Caucasus, Russia, in the skarnified limestone xenolith in ignimbrite. This hydrothermal mineral occurs in a cavity of altered larnite skarn and is associated with larnite, calcium humite-group members, hydrogarnets, bultfonteinite, afwillite, and ettringite. Aklimaite forms transparent, colorless (or occasionally with pinkish tint) columnar or lath-shaped crystals up 3 × 0.1 × 0.01 mm in size, flattened on {001} and elongated along {010}; they are combined in spherulites. The luster is vitreous; the cleavage parallel to the {001} is perfect. D calc = 2.274 g/cm3. The Mohs' hardness is 3-4. Aklimaite is optically biaxial, negative, 2 V meas > 70°, 2 V calc = 78°, ? = 1.548(2), ? = 1.551(3), ? = 1.553(2). The IR and Raman spectra are given. The chemical composition (wt %, electron microprobe) is as follows: 0.06 Na2O, 0.02 K2O, 45.39 CaO, 0.01 MnO, 0.02 FeO, 24.23 SiO2, 0.04 SO3, 3.22 F, 27.40 H2O(calc.), -1.36 -O=F2; the total is 99.03. The empirical formula calculated on the basis of 2Si apfu with O + OH + F = 16 is as follows: (Ca4.02Na0.01)?4.03[Si2.00O5.07(OH)1.93][(OH)3.16F0.84] ?4.00 · 5H2O. The mineral is monoclinic, space group C2/ m, a = 16.907(5), b = 3.6528(8), c = 13.068(4) Å, ? = 117.25(4)·, V= 717.5(4) Å3, Z = 2. Aklimaite is representative of the new structural type, the sorosilicate with disilicate groups [Si2O5(OH)2]. The strongest reflections in the X-ray powder patterns [ d, Å ( hkl)] are: 11.64(100)(001), 2.948(32)(310, 203), 3.073(20) (, ), 2.320(12)(005, 510), 2.901 (11)(004), 8.30(10). The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Zadov, A. E.; Pekov, I. V.; Zubkova, N. V.; Gazeev, V. M.; Chukanov, N. V.; Yapaskurt, V. O.; Kartasheov, P. M.; Galuskin, E. V.; Galuskina, I. O.; Pertsev, N. N.; Gurbanov, A. G.; Pushcharovsky, D. Yu.

2013-12-01

299

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

300

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

301

Diffusion reaction in a thermal gradient: Implications for the genesis of anorthitic plagioclase, high alumina basalt and igneous mineral layering  

NASA Astrophysics Data System (ADS)

Piston-cylinder experiments investigating the interaction between basaltic andesite melt and partially molten gabbro in a thermal gradient provide insight into melt-rock reaction processes occurring during magma differentiation in the crust. In two experiments juxtaposing basaltic andesite and gabbro at 0.5 GPa pressure for durations of either 13 or 26 days, diffusive chemical exchange between the two materials results in mineral layering and notable mineral compositions such as anorthitic plagioclase. Specifically, the basaltic andesite gains Al 2O 3, MgO and CaO from the gabbro and loses Na 2O, K 2O, SiO 2 and FeO to it with a plagioclase-rich layer developing at the interface between the two materials in a process termed diffusion-reaction. The percent crystallinity of the basaltic andesite increases during the process and the plagioclase crystals within the interface region develop anorthitic cores (up to An 90) that abruptly shift in composition to thin rims that are in Na-Ca exchange equilibrium with the co-existing melt. Both the mineralogical layering and bulk compositional change occurring at the interface are reproduced in model simulations of diffusion-reaction. Isotopic tracers ( 45Ca, 6Li, 84Sr and 136Ba) initially deposited at the basaltic andesite-gabbro interface in the 13-day experiment were detected in the cores of the anorthitic plagioclase after the experiment, demonstrating that the melt chemically communicates with the plagioclase cores over the duration of the diffusion-reaction experiment. The formation of anorthitic plagioclase during diffusion-reaction may explain its widespread occurrence in terrestrial volcanic rocks without requiring the presence of ultra-calcic melts. Textures and mineralogical changes in the gabbro indicate that chemical transport occurs throughout the experiments despite temperatures at the cold end of the experimental capsule approaching 500 °C. For instance, apatite, FeNiS, olivine and almost pure albite occur at distinct, specific horizons in the gabbro within the 26-day experiment. Because the bulk element profiles indicating chemical transport reflect analyses of almost completely solid gabbro, equilibration between minerals and fluids/melts must be rapid. The overall effect of the diffusion-reaction process is to make an ascending magma more primitive in composition (and in this case, produce anorthitic plagioclase) while making surrounding crustal wall rocks more evolved. Several observations within igneous rocks support the occurrence of this process, suggesting that the genesis of porphyritic high alumina basalt, ubiquitously observed at convergent margins, could reflect a diffusion-reaction process in the crust.

Lundstrom, Craig; Boudreau, Alan; Pertermann, Maik

2005-09-01

302

Osumilite-(Mg): Validation as a mineral species and new data  

NASA Astrophysics Data System (ADS)

Osumilite-(Mg), the Mg-dominant analogue of osumilite, has been approved by the CNMNC IMA as a new mineral species. The holotype sample has been found at Bellerberg, Eifel volcanic area, Germany. Fluorophlogopite, sanidine, cordierite, mullite, sillimanite, topaz, pseudobrookite and hematite are associated minerals. Osumilite-(Mg) occurs as short prismatic or thick tabular hexagonal crystals reaching 0.5 × 1 mm in size in the cavities in basaltic volcanic glasses at their contact with thermally metamorphosed xenoliths of pelitic rocks. The mineral is brittle, with Mohs' hardness 6.5. Cleavage was not observed. Color is blue to brown. D meas = 2.59(1), D calc = 2.595 g/cm3. No bands corresponding to H2O and OH-groups are in the IR spectrum. Osumilite-(Mg) is uniaxial (+), ? = 1.539(2), ? = 1.547(2). The chemical composition (electron microprobe, average of 5 point analyses, wt %) is: 0.08 Na2O, 3.41 K2O, 0.04 CaO, 7.98 MgO, 0.28 MnO, 21.57 Al2O3, 3.59 Fe2O3, 62.33 SiO2, total 99.28. The empirical formula is: (K0.72Na0.03Ca0.01)(Mg1.97Mn0.04)[Al4.21Fe{0.45/3+}Si10.32]O30. The simplified formula is: KMg2Al3(Al2Si10)O10. The crystal structure was refined on a single crystal, R = 0.0294. Osumilite-(Mg) is hexagonal, space group P6/ mcc; a = 10.0959(1), c = 14.3282(2)Å, V = 1264.79(6) Å3, Z = 2. The strongest reflections in the X-ray powder diffraction pattern [ d, Å I %) ( hkl)] are: 7.21 (37) (002), 5.064 (85) (110), 4.137 (45) (112), 3.736 (43) (202), 3.234 (100) (211), 2.932 (42) (114), 2.767 (51) (204). A type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

Chukanov, N. V.; Pekov, I. V.; Rastsvetaeva, R. K.; Aksenov, S. M.; Belakovskiy, D. I.; Van, K. V.; Schüller, W.; Ternes, B.

2013-12-01

303

Explosive eruption of rhyodacitic magma at the Cordón-Caulle volcanic complex, southern Chile  

NASA Astrophysics Data System (ADS)

After lying dormant for decades, the Cordón-Caulle volcanic complex (CCVC) reactivated again on 4 June, 2011 with an explosive eruption that produced a sustained vertical ash column reaching roughly 14,000 m a.s.l. This explosive phase produced a tephra plume that dispersed E-SE across the Chilean Patagonia into Argentina, and within a week encircled the globe prompting widespread disruption to air traffic and several airport closures. After about 3 weeks of fluctuating explosive activity, a lava flow began effusing from the same vent as the initial activity. We analyzed pumice and ash samples of the Plinian fall from 4 June for their major and trace element makeup, mineralogical characteristics, and 3D textural relationships within pyroclasts. The light beige, phenocryst-poor (<5 vol%) pumice contains plagioclase (~1mm) as its primary phase, and magnetite, orthopyroxene and clinopyroxene in sub-equal amounts. The crystals often form intergrowth clusters but may also be found separate and enclosed in highly vesicular microlite-free glass. As shown by XRF analyses on bulk pumice and ash samples collected from two localities southeast of the vent, the current eruptives comprise the following (in wt.%): SiO2 = 69.6, TiO2 = 0.70, Al2O3 = 14.3, Fe2O3 = 4.56, MnO = 0.11, MgO = 0.54, CaO = 2.3, Na2O = 5.14, K2O = 2.75, P2O5 = 0.11; and, (in ppm): Cr = 6.7, Ni = 2.3, Rb = 70.3, Sr = 163.3, Y = 51.7, Zr = 328, Ba = 702, Pb = 23.7. Interestingly, these compositions are virtually identical to those of magma erupted during 1960 and closely resemble rhyodacite erupted in 1921 from nearby vents. The primary difference between the present eruption and its recent predecessors is the much greater eruptive vigour of the current phase. Another distinction between the present and past historical eruptions is the presence of conspicuous mafic-felsic mingling textures in a small percentage (~0.5 vol%) of the current pumice. Textural and chemical analyses of the mafic blobs are currently underway in order to establish their role in the eruption. The apparent compositional homogeneity of silicic magmas erupted recently at CCVC highlights several important problems regarding magma chamber longevity, eruption triggering, and dynamics of explosive-effusive eruption cycles at CCVC. We are currently addressing some of these topics through further analytical and textural characterization of the eruption products, field relations, and experimental reproduction of salient petrological features.

Castro, J. M.; Schipper, C.

2011-12-01

304

Chaotic Mixing of Granitic and Basaltic Liquids  

NASA Astrophysics Data System (ADS)

Chaotic mixing in magma chambers may play a central role in determining the timing and dynamics of volcanic eruptions. The dynamics of such chaotic mixing has been investigated solely in analog systems and in numerical simulations to date. Here we report the first experimental study of the dynamics of chaotic mixing in molten silicates of geological relevance. A newly developed device for the simulation of chaotic dynamics has been successfully employed for this purpose. Its development is based on the importance of chaotic dynamics for mixing processes; and previous studies evidencing that chaotic dynamics could equally control magma mixing processes in nature (Perugini et al., 2006. EPSL, 234: 669-680 and references therein). The special device for chaotic mixing silicate melts at high temperatures (up to 1700°C) has been built after the journal-bearing or eccentric-cylinder geometry for viscous fluids for the study of chaotic mixing in slow flows (Swanson and Ottino, 1990. J. Fluid Mech., 213:227-249). In order to generate chaos in a flow, the streamlines must be time dependent, resulting from alternating movements between the two cylinders. The mixing experiments were performed using end-members of: haplogranite [In wt.%: SiO2(71.6), Al2O3(12.4), Na2O(7.0), K2O(9.0)] and haplobasalt [SiO2(48.6), Al2O3(16.3), CaO(23.8), MgO (11.4)]. The haplogranite was doped with trace amounts of Rb, Sr, Ba, Zr and REE oxides. The experimental protocol started with a single run of alternating movements of spindle and crucible. It lasted for 110 minutes at a temperature of 1400°C. The experiment terminated by stopping all movement and letting the sample cool to room temperature. A cylinder of the resultant mixed glassy sample was recovered by drilling. Horizontal sections of this cylinder at varying heights were prepared for microprobe and ICP-MS- Laser Ablation analyses. Preliminary optical and microprobe studies reveal crystal-free filaments of intermediary compositions, changing with depth, in complex chaotic patterns. The general morphology of experimental flow patterns matches theoretical predictions well. We will present the chemical analytical evaluation of these experiments in the context of the effectiveness of the interplay between convection and diffusion, under chaotic dynamics, in enhancing mixing in silicate melts. The results are strong evidence that the treatment of or testing for mixing based solely on the presence of straight lines on inter-elemental plots is flawed.

Decampos, C.; Ingrisch, W. E.; Perugini, D.; Dingwell, D. B.; Poli, G.

2008-12-01

305

Neogene ignimbrites in the area of Arequipa, southern Peru: correlations, flow directions and sources  

NASA Astrophysics Data System (ADS)

In the area of Arequipa, the ignimbrites termed "sillars" are indurated, more or less welded pyroclastic flow deposits of rhyolitic composition. Our stratigraphic study and Ar-Ar date ages, show four main ignimbrite units: (1) two middle Miocene units (between 13.07±0.05 and 14.8±0.15 Ma) including the "base of Rio Chili" and the "Old sillar"; (2) a Middle to Early Pliocene unit (4.87±0.02 Ma), represented by the "La Joya sillar", (3) two Late Pliocene units (1.64±0.07 Ma), including a "white sillar" which grades into an overlying "pinkish unit", and finally (4) early Pleistocene (1.02±0.09 Ma) pumice-flow deposits channeled in the Rio Yura valley on the west flank of the Chachani volcanic complex. All these units are intercalated with alluvial sediments of variable thickness. The mineral assemblage encompasses plagioclase, biotite, quartz, sanidine, magnetite and ilmenite. Amphibole is only present in the "old sillar" and "La Joya sillar", which are unique in being porphyric. Crystals display large compositional variations because they are weathered. However, the MnO v. FeO diagram for biotites allows us to separate three compositional groups which correspond to (1) the "base of Rio Chili", (2) the Pliocene ignimbrites, and (3) the "old sillar". Harker diagrams of whole rock (pumice) analyses, show two distinct fractional crystallization trends with parallel evolutions. The first trend, which shows an evolution within Miocene ignimbrites, is more enriched in K_2O, Nb, Y and less enriched in Ba, Sr, Na_2O, CaO and P_2O_5 than the second Pliocene trend. We cannot locate source(s) for the Miocene ignimbrites because intense deformation and erosion have taken place after their emplacement; in addition AMS is not a valid method in this case because the flows are channelized in valleys, thus strongly influenced by the paleotopography. The source of the Pliocene ignimbrites, however, can be located by the AMS directions toward the NE of Arequipa depression, probably beneath the Chachani volcanic complex. The Pleistocene "Rio Yura Tuffs" source should be found on the north flank of Chachani, beneath Cerro Nocarani.

Paquereau, P.; Thouret, J.-C.; Wörner, G.; Fornari, M.; Roperch, P.

2003-04-01

306

Chemistry of micas from kimberlites and xenoliths - II. Primary- and secondary-textured micas from peridotite xenoliths  

NASA Astrophysics Data System (ADS)

Micas from coarse granular Iherzolites in S. African kimberlites may be separated into two groups; those showing primary textural relationships with coexisting silicates and those with secondary, alteration relationships with other silicates. Primary-textured micas form a tight cluster with a mean composition from 10 coarse garnet lherzolites of: SiO 2 41.0, TiO 2 0.18, Al 2O 3 13.5, Cr 2O 3 0.82, total Fe as FeO 2.60, MnO 0.02, MgO 26.0, NiO 0.22, CaO 0.01, BaO 0.29, Na 2O 0.31, K 2O 10.0, Rb 2O 0.028, Cl 0.08, F 0.43 wt%. Primary-textured micas in aggregates with clinopyroxene have higher TiO 2 and four specimens which look similar to the primary group but have textural ambiguities have still higher TiO 2 Micas with secondary textures have wide ranges of composition which may be correlated with details of the textural parageneses. Micas from kelyphitic rims around garnets tend to be Cr-rich while those from veinlets are Cr-poor. Both groups tend to have higher FeO and TiO 2 than the primary group. Micas produced by alteration of, or filling veinlets through, orthopyroxene have a wide compositional range which overlaps that of the primary-textured micas, especially for harzburgite specimens. The primary-textured micas show a positive correlation with coexisting pyroxenes for MgO/(MgO + FeO) and TiO 2, but not for Cr 2O 3. Secondary-textured micas do not show correlations with coexisting pyroxenes for any elements. The 'primary-metasomatic' micas described by Harte and Gurney (1975) and metasomatic and other micas described by Boettcher et al. (1979) and Boettcher and O'neil (1979) are richer in FeO and TiO 2 than the present primary-textured micas, and are attributed to crystallization from fractionated fluids.

Delaney, J. S.; Smith, J. V.; Carswell, D. A.; Dawson, J. B.

1980-06-01

307

Geochemical and technological characterization of clays of Corumbataí Formation, Paraná Basin, in the state of São Paulo, Brazil for the application in the ceramic industry.  

NASA Astrophysics Data System (ADS)

The Corumbataí Formation is a geological unit of the Paraná Basin comprises a range of predominantly argillaceous facies. These clays are important from an economic point of view, because they represent important mineral deposits suppliers of raw materials for the ceramic industry in the production of ceramic tiles.The study presents preliminary results of a research that aims to study the clays municipalities Tambaú, Ferreira and Santa Rosa of Viterbo in the State of São Paulo for their application and diversification of ceramic products. The methodology used was based on a detailed description of facies using the methodology in principles of analysis of Basin Miall (1984), followed by mineralogical identification by X-ray Diffraction, chemical analysis of major elements by X-ray Fluorescence and technological tests ceramic. According to the geological surveys of mines studied through columnar sections were identified the following lithofacies from base to top: Massive, Laminated, Intercalated and Altered. The mineralogy present on these lithofacies is composed by minerals: quartz, microclineo, albite, calcite, dolomite and hematite and by clay minerals illite, kaolinite and montmorillonite. The quartz represents the mineral more present in diffraction and occurs with d001 of 3.33Å in all lithofacies studied. The illite clay mineral represents the most frequent in studied samples presenting d 001 10Å in three conditions (natural, heated and treated with ethylene glycol) in which the blade was subjected to the analysis of X-ray diffraction, the presence of kaolinite or montmorillonite occurs or not in samples. It was observed a increased frequency of some minerals in the lithofacies studied, carbonates (calcite and dolomite), hematite and feldspar occurring in the intermediate portions of the profile with a predominance in lithofacies Intercalated. The illita clay mineral occurs throughout the profile, but with greater frequency in the lithofacies Massive and Laminated. The clay minerals kaolinite and montmorillonite occur in portions intermediate and top of the profiles studied in the intercalated and altered lithofacies. The chemical results of major elements by X-ray fluorescence confirmed the mineralogical results, with average values of 63.74 % of SiO2, 12.50 of Al2O3, 4.35% of of K2O, 0.45% of Na2O, 2,72% of CaO and 1,87 of MgO. The results chemical and mineralogical subsidized testing and ceramic formulations due to be executed later so defining the main applications of these clays in the production of ceramic products. The authors acknowledge the finantial support of Fundação de Amparo à Pesquisa do Estado de São Paulo-FAPESP, (Process, number 2012/24219-9).

Christofoletti, Sergio Ricardo; Torres Moreno, Maria Margarita; Batezelli, Alessandro; Zanardo, Antenor

2014-05-01

308

The geochemistry of phosphorus in granite rocks and the effect of aluminium  

NASA Astrophysics Data System (ADS)

Phosphorus has been shown to have a profound influence on the evolution of silicate melt systems. It also controls the geochemical behavior of rare earths, uranium, thorium, strontium and other elements through the relationships between melt and accessory phosphates. Based on experimental data, Harrison and Watson (1984) proposed a model of saturation behavior of apatite in crustal melts as a function of temperature and silica content. Subaluminous granites fit in well with such a model, but departures are evident in the case of peraluminous granites. A systematic study of the distribution of P 2O 5 in granitoids from all over the world shows that there are two modes to describe phosphorus enrichment in peraluminous granitic rocks: (1) The Hoyos-type trend, which is parallel to the one in Harrison and Watson's (HW) model but with higher P 2O 5 concentrations at the same silica contents and (2) The Pedrobernardo-type trend, implying an increase in phosphorus in the most SiO 2-rich differentiates of strongly peraluminous, low-Ca granites. Pedrobernardo-type leucogranites are characterized by the presence of rare phosphates or P-rich feld-spars. Since they have excess P 2O 5 over CaO to form normative apatite, we here propose the term "perphosphorous granites". High phosphorus contents appear to be due to elevated apatite solubility in peraluminous granitic melts rather than to high amounts of restitic apatite. Both the Hoyos- and Pedrobernardo-type departures from the HW model can be "corrected" by using the expression: P 2O 5corrected = P 2O 5HW × efactor, where P 2O 5HW is the prediction according to the HW model, and "factor" is (ASI-1) × ( {6429}/{T}) , ASI being the {Al 2O 3}/{(CaO+Na 2O+K 2O) } molar ratio. We suggest that such departures could be caused by a decrease in the Ca activity in the melt as a result of increased peraluminousity. The Pedrobernardo-type trend is a limiting case in which Ca-activity in the melt is nearly zero and calcium, instead of phosphorus, becomes the essential structural constituent (ESC) of the apatite. When this happens, phosphorus starts behaving as an incompatible element that is concentrated in late fluids. High P 2O 5 contents are more characteristic of S- than other granite types. No significant departures from the HW model have been found for I-, A- or M-type granites. In Central Iberia, granites associated with U, Sn and W mineralizations usually have high phosphorus contents. Values of P 2O 50.5 wt% at SiO 270 wt.% are good indicators of economic mineralization.

Bea, F.; Fershtater, G.; Corretgé, L. G.

1992-12-01

309

Petrology and Geochemistry of the Trachyte Mesa Magma Sheets, Henry Mountains, Utah.  

NASA Astrophysics Data System (ADS)

Trachyte Mesa (TM) is a satellite laccolithic intrusion peripheral to the Mount Hillers intrusive center in the Henry Mountains of south-central Utah. The TM outcrops are characteristically composed of plagioclase- hornblende porphyry which contain rare mafic crustal xenoliths. On the basis of geophysical evidence, Morgan and others (GSA Annual Meeting Field Guide, 2005) have suggested that the Mount Hillers center fed TM via several "magma fingers" as opposed to dikes. Moreover, on the basis of outcrop relationships, they proposed that the TM developed its laccolithic shape through inflation related to successive emplacement of several magma "sheets." Given the well-exposed nature of the TM sheets, numerous samples were collected and analyzed to evaluate geochemical characteristics and potential compositional variations within and among the sheets. Our preliminary results indicate that the analyzed sheets are compositionally classified as dacite, and fall within the range of values published by other authors for laccolithic rocks of the Henry Mountains (e.g. Nelson and Davidson, 1997). The TM samples are characterized by the following compositional ranges: SiO2=62.5-65.5%; TiO2=.44-.53%; Al2O3 =17.5-19%; Fe2O3=3.4-4.7%; MnO=.05-.15%; MgO=0.4-1.5%; CaO=4.8-7%; Na2O=3.5-4.3%; K2O=2-2.6%; P2O5=.19-.23%; Nb=4-9ppm; Zr=120-160ppm; Y=14-18ppm; Sr=650-950ppm; Rb=25-40ppm; Pb=12-25ppm; V=53-77ppm; and Ba=950-1100ppm. Within individual sheets, the observed compositional variation of major and trace elements is relatively small, with no obvious evidence of systematic geochemical change. Similarly, among various sheets, the compositional variation of most major and trace elements also appears to be small, however, our existing data do not preclude the possibility of real but subtle geochemical variations between individual sheets. At present, however, our data and observations suggest that the TM laccolith was formed from a rather homogeneous magma characterized by a lack of significant geochemical differentiation. Consequently, it may be inferred that the emplacement of the TM was a relatively rapid as opposed to a prolonged and/or episodic event.

Matty, D. J.; Student, J. J.; Morgan, S. S.

2006-12-01

310

Origin of granite at Cabo de Santo Agostinho, Northeast Brazil  

NASA Astrophysics Data System (ADS)

A 4 km2 exposure of shallowly-emplaced leucogranite on the Atlantic coast at Cabo de Santo Agostinho, 30 km south of Recife, Brazil has been extensively studied chemically and isotopically. Twenty-three major-element analyses indicate that the Cabo granite ranges from peralkaline to peraluminous; Na2O+K2O is very high (7.4 to 10.4 wt.%), with CaO low (˜0.3%) and MgO vanishing (<0.06%). Microprobe analyses confirm the presence of arfvedsonite (biotite absent), and nearly total absence of plagioclase. The rocks are moderately to highly enriched in LREE (La 45 to 350 times chondritic), with extremely pronounced negative Eu anomalies (Eu/Eu*=0.02 to 0.07). Whole-rock ? 18O is consistent at +8.5±0.3%.oSMOW A Rb-Sr isochron age of isotopically slightly disturbed samples is 104.8±1.8 Ma, with initial87Sr/86Sr=0.7084±0.0011. Sr is depleted (2 20 ppm) but Ba is 200 750 ppm. Crystallization path calculations and petrographic observations suggest that magma formed at a pressure close to 6 kbar but rose to a crustal level equivalent to roughly 1 kbar. Quartz, the liquidus phase at moderate H2O concentrations and pressures above 2 kbar, was resorbed during decompression as the magma moved upwards. Ultimately, quartz and alkali feldspar coprecipitated. Feldspar was not retained in the source rock nor removed early from the fractionating magma. Therefore the strong negative Eu anomaly and low Sr abundance are characteristics inherited from the source. A high H2O concentration necessary for a large degree of melting was lacking, hence the Cabo magma composition must reflect a small degree of partial melting of a rather quartz-rich rock such as a feldspathic arenite. In a pre-drift reconstruction of Gondwanaland, the Cabo granite fits on the southernmost and youngest end of the trend of the Niger-Nigerian igneous centers with which it has close affinity. The Cabo granite occupies the western end of the trace of the ancestral Ascension mantle plume which presumably served as the heat source.

Long, Leon E.; Sial, Alcides N.; Nekvasil, Hanna; Borba, Glicia S.

1986-09-01

311

A comparative evaluation of the CF:CS and CRS models in 210Pb chronological studies applied to hydrographic basins in Brazil.  

PubMed

The Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported?excess (210)Pb models have been applied to a (210)Pb data set providing of eighteen sediments profiles sampled at four riverine systems occurring in Brazil, South America: Corumbataí River basin (S1=Site 1, São Paulo State), Atibaia River basin (S2=Site 2, São Paulo State), Ribeirão dos Bagres basin (S3=Site 3, São Paulo State) and Amazon River mouth (S4=Site 4, Amapá State). These sites were chosen for a comparative evaluation of the performance of the CF:CS and CRS models due to their pronounced differences on the geographical location, geological context, soil composition, biodiversity, climate, rainfall, and water flow regime, among other variable aspects. However, all sediments cores exhibited a common denominator consisting on a database built from the use of the same techniques for acquiring the sediments major chemical composition (SiO2, Al2O3, Na2O, K2O, CaO, MgO, Fe2O3, MnO, P2O5, TiO2 and LOI-Loss on Ignition) and unsupported/excess (210)Pb activity data. In terms of sedimentation rates, the performance of the CRS model was better than that of the CF:CS model as it yielded values more compatible with those expected from field evidences. Under the chronological point of view, the CRS model always provided ages within the permitted range of the (210)Pb-method in the studied sites, whereas the CF:CS model predicted some values above 150 years. The SiO2 content decreased in accordance with the LOI increase in all cores analyzed and such inverse relationship was also tracked in the SiO2-LOI curves of historical trends. The SiO2-LOI concentration fluctuations in sites S1 and S3 also coincided with some Cu and Cr inputs in the drainage systems. PMID:25005051

Bonotto, D M; García-Tenorio, R

2014-09-01

312

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

313

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

314

Hillesheimite, (K,Ca,?)2(Mg,Fe,Ca,?)2[(Si,Al)13O23(OH)6](OH) · 8H2O, a new phyllosilicate mineral of the Günterblassite group  

NASA Astrophysics Data System (ADS)

A new mineral, hillesheimite, has been found in the Graulai basaltic quarry, near the town of Hillesheim, the Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. It occurs in the late assemblage comprising nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite-group minerals, and åkermanite. Colorless flattened crystals of hillesheimite reaching 0.2 × 1 × 1.5 mm in size and aggregates of the crystals occur in miarolitic cavities in alkali basalt. The mineral is brittle, with Mohs' hard-ness 4. Cleavage is perfect parallel to (010) and distinct on (100) and (001). D calc = 2.174 g/cm3, D meas = 2.16(1) g/cm3. IR spectrum is given. Hillesheimite is biaxial (-), ? = 1.496(2), ? = 1.498(2), ? = 1.499(2), 2 V meas = 80°. The chemical composition (electron microprobe, mean of 4 point analyses, H2O determined from structural data, wt %) is as follows: 0.24 Na2O, 4.15 K2O, 2.14 MgO, 2.90 CaO, 2.20 BaO, 2.41 FeO, 15.54 Al2O3, 52.94 SiO2, 19.14 H2O, total is 101.65. The empirical formula is: K0.96Na0.08Ba0.16Ca0.56Mg0.58Fe{0.37/2+}[Si9.62Al3.32O23(OH)6][(OH)0.82(H2O)0.18] · 8H2O. The crystal structure has been determined from X-ray single-crystal diffraction data, R = 0.1735. Hillesheimite is orthorhombic, space group Pmmn, the unit-cell dimensions are: a = 6.979(11), b = 37.1815(18), c = 6.5296(15) Å; V=1694(3) Å3, Z = 2. The crystal structure is based on the block [(Si,Al)13O25(OH)4] consisting of three single tetrahedral layers linked via common vertices and is topologically identical to the triple layers in günterblassite and umbrianite. The strong reflections [ d Å ( I %)] in the X-ray powder diffraction pattern are: 6.857(58), 6.545(100), 6.284(53), 4.787(96), 4.499(59), 3.065(86), 2.958(62), 2.767(62). The mineral was named after its type locality. Type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

Chukanov, N. V.; Zubkova, N. V.; Pekov, I. V.; Belakovskiy, D. I.; Schüller, W.; Ternes, B.; Blass, G.; Pushcharovsky, D. Yu.

2013-12-01

315

High-Mg carbonatitic microinclusions in some Yakutian diamonds—a new type of diamond-forming fluid  

NASA Astrophysics Data System (ADS)

The composition of microinclusions in 26 fibrous cubic and coated diamonds from the Daldyn-Alakit kimberlite field, Yakutia were studied using EPMA and FTIR and the carbon isotopic composition of 4 of the diamonds was studied using SIMS. Fifteen diamonds carry carbonatitic high-density fluids (HDFs) with high MgO content (17-28 wt.%) whereas the MgO content of fluids in other diamonds does not exceed 14 wt.%. We propose that the two groups are distinct and evolved separately. The low-Mg suite is similar to previously reported carbonatitic to silicic HDFs from Africa and Brazil. The high-Mg suite is carbonatitic, but its composition is distinct from previously defined end-members. As the MgO content decreases from 28 to 17 wt.%, CaO, Na 2O, K 2O and Cl also decrease while the silica, Al 2O 3, TiO 2 and P 2O 5 contents remain constant. Additionally, the water band in the FTIR spectra of high-Mg HDFs is wider relative to the water band in the spectra of low-Mg carbonatitic HDFs. By combining EPMA and FTIR data, we have constrained the major element composition of the high-Mg carbonatitic end-member, which comprises 78 wt.% carbonates, 9% silicates, 6% water, 5% apatite and 2% halides. The composition of the high-Mg suite is closer to that of near-solidus melts of fertile carbonate peridotites and harzburgites. Thus, it should be possible to produce the Mg-rich HDF either by incipient melting, or by cooling and crystallization of a proto-kimberlitic melt at depth. However, the peridotitic system alone cannot explain the high alkali and Cl content of the fluids. We suggest that the elevated alkali and Cl content of the high-Mg carbonatites are related to interaction of carbonate peridotite with saline fluids, or of peridotite with chloride-carbonate melts. The major element composition of the high-Mg carbonatitic HDF is dominated by the low-fraction melts of the peridotite while the content of potassium and other incompatible elements is influenced by the contribution of the saline or carbonatitic fluids.

Klein-BenDavid, Ofra; Logvinova, Alla M.; Schrauder, Marcus; Spetius, Zladislav V.; Weiss, Yaakov; Hauri, Erik H.; Kaminsky, Felix V.; Sobolev, Nikolay V.; Navon, Oded

2009-11-01

316

Heavy metal accumulation in balsam pear and cowpea related to the geochemical factors of variable-charge soils in the Pearl River Delta, South China.  

PubMed

Variable-charge (v-c) soils in subtropical areas contain considerable amounts of iron/aluminum (Fe/Al) oxides that can strongly influence the fate of heavy metals in agricultural ecosystems. However, the relationship between heavy metal accumulation in vegetables and the geochemical factors associated with v-c soils in subtropical regions remains unknown. The present study investigated heavy metal accumulation under field conditions in the Pearl River Delta (PRD) by measuring the content of 8 heavy metals (zinc (Zn), arsenic (As), copper (Cu), mercury (Hg), lead (Pb), chromium (Cr), nickel (Ni) and cadmium (Cd)) in 43 pairs of v-c soil and vegetable (balsam pear and cowpea) samples. Soil physicochemical properties including pH, texture, organic matter and oxide minerals (Fe2O3, SiO2, Al2O3, CaO, MgO, K2O and Na2O) were also analyzed. Heavy metal accumulation from soil to vegetables was assessed based on bioconcentration factors (BCFs). The results showed that soil extractable Fe, oxide minerals and chemical weathering indices of v-c soils strongly affected heavy metal accumulation, whereas the content of Zn, Cu, Cr and Ni in vegetables was strongly affected by the soil clay content. Significant correlations were found between the BCFs of heavy metals and oxide minerals. However, no significant relationship was found between pH and heavy metal accumulation (except for Cu) in balsam pear and cowpea. Correlation analyses showed that a lower oxalate/DCB- extractable Fe content might indicate greater heavy metal (Zn, Cu, Hg, Cr and Ni) accumulation in vegetables. Therefore, it can be deduced that oxalate/DCB- extractable Fe content is a critical geochemical factor that determines the bioavailability of heavy metals and that iron biogeochemical cycles play vital roles in the fate of heavy metals in vegetable fields in this area. These findings provide new insights into the behaviors and fate of heavy metals in subtropical v-c soils and can be used to develop possible guidelines for vegetable safety management. PMID:24855639

Chang, Chun-Ying; Xu, Xiang-Hua; Liu, Chuan-Ping; Li, Shu-Yi; Liao, Xin-Rong; Dong, Jun; Li, Fang-Bai

2014-07-01

317

Textural and Compositional Variations in a Large Mafic Enclave from the Purico-Chascon Volcanic Complex: Understanding Mafic Recharge in a Large Continental Magmatic System  

NASA Astrophysics Data System (ADS)

Mafic enclaves in silicic volcanic rocks provide vital information regarding the role of mafic replenishment in the long-term evolution and triggering of eruptions in silicic magma systems. In this study, we are investigating textural and compositional variations in a single large (~25 x 10 cm) mafic enclave from the Cerro Chascon lava dome in the Purico-Chascon Volcanic Complex of Northern Chile. The Cerro Chascon lava dome is predominantly high-K crystal-rich dacite, similar to other major volcanic units in the region, but is rare in that it contains significant basaltic-andesite mafic enclaves. The mafic enclave analyzed in this study is porphyritic containing plagioclase + amphibole + clinopyroxene + olivine + Fe-Ti oxides in a groundmass of high-silica (~69-73 wt.% SiO2) glass with plagioclase and amphibole micro-phenocrysts, and acicular plagioclase microlites. There is also strong evidence for the incorporation of crystalline material from the dacite host. In particular, the mafic enclave contains large embayed quartz crystals that are rimmed with clinopyroxene, and large plagioclase crystals with heavily sieved high anorthite (An70-85) rims and clear cores that are compositionally indistinguishable from plagioclase crystals in the host (An45-50). There do not appear to be significant variations in the distribution of the xenocrysts within the enclave, but there are significant variations in the texture, composition, and microlite content of the groundmass glass. More specifically, there is a systematic increase in the amount of vesicularity (~3-5 vol.%) and decrease in vesicle size from the enclave interior to the enclave-host contact. These textural variations are accompanied by small but significant variations in the major element chemistry, (SiO2 and K2O increase from rim-ward, and CaO, Na2O, and Cl decrease) and a rim-ward increase in the proportion of plagioclase microlites. The random distribution of xenocrysts and systematic textural, chemical, and modal (microlites) variations within the mafic enclave indicate the transfer of crystalline material into the enclave occurred prior to the formation of the textural, chemical, and microlite gradients. We believe that the xenocrysts were incorporated prior to the emplacement of the enclave into the dacite host, and that the variations in vesicularity, major element chemistry, and microlite content formed post emplacement. Furthermore, there is strong evidence that the observed major element variations resulted from the increase in microlite crystallization near the enclave-host contact. The rim-ward increase in vesicularity is consistent with this model, assuming the amount of crystallization is sufficient to cause vapor oversaturation in the residual melt.

Burns, D. H.; Tepley, F. J.; de Silva, S. L.; Carter, Z. G.

2011-12-01

318

Experimental and Petrological Constraints on Lunar Differentiation from the Apollo 15 Green Picritic Glasses  

NASA Technical Reports Server (NTRS)

Phase equilibrium experiments on the most magnesian Apollo 15C green picritic glass composition indicate a multiple saturation point with olivine and orthopyroxene at 1520 C and 1.3 GPa (about 260 km depth in the moon). This composition has the highest Mg# of any lunar picritic glass and the shallowest multiple saturation point. Experiments on an Apollo 15A composition indicate a multiple saturation point with olivine and orthopyroxene at 1520 C and 2.2 GPa (about 440 km depth in the moon). The importance of the distinctive compositional trends of the Apollo 15 groups A, B, and C picritic glasses merits the reanalysis of NASA slide 15426,72 with modern electron microprobe techniques. We confirm the compositional trends reported by Delano (1979, 1986) in the major element oxides SiO2, TiO2, Al2O3, Cr2O3, FeO, MnO, MgO, and CaO, and we also obtained data for the trace elements P2O5, K2O, Na2O, NiO, S, Cu, Cl, Zn, and F. Petrogenetic modeling demonstrates that the Apollo 15 A-B-C glass trends could not have been formed by fractional crystallization or any continuous assimilation/fractional crystallization (AFC) process. The B and C glass compositional trends could not have been formed by batch or incremental melting of an olivine + orthopyroxene source or any other homogeneous source, though the A glasses may have been formed by congruent melting over a small pressure range at depth. The B compositional trend is well modeled by starting with an intermediate A composition and assimilating a shallower, melted cumulate, and the C compositional trend is well modeled by a second assimilation event. The assimilation process envisioned is one in which heat and mass transfer were separated in space and time. In an initial intrusive event, a picritic magma crystallized and provided heat to melt magma ocean cumulates. In a later replenishment event, the picritic magma incrementally mixed with the melted cumulate (creating the compositional trends in the green glass data set), ascended to the lunar surface, and erupted as a fire fountain. A barometer created from multiple saturation points provides a depth estimate of other glasses in the A-B-C trend and of the depths of assimilation. This barometer demonstrates that the Apollo 15 A-B-C trend originated over a depth range of approx.460 km to approx.260 km within the moon.

Elkins-Tanton, Linda T.; Chatterjee, Nilanjan; Grove, Timothy L.

2003-01-01

319

Origin of two types of rhyolites in the Tarim Large Igneous Province: Consequences of incubation and melting of a mantle plume  

NASA Astrophysics Data System (ADS)

The Early Permian Tarim Large Igneous Province (LIP) in northwestern China contains a large area of silicic volcanics (~ 48,000 km2) which are spatially and temporally associated with mafic-ultramafic rocks. In order to understand the behavior of crust above a mantle plume, selected rhyolitic samples are investigated in terms of U-Pb zircon dating, geochemical and isotopic analyses. The Tarim rhyolites have high A/CNK ratios (= molar Al2O3/CaO + Na2O + K2O), Fe#, Ga/Al ratios, concentrations of high field strength elements (HFSEs) such as Zr and Nb, and rare earth elements (REEs), along with high zircon saturation temperatures (872-940 °C), typical of aluminous A-type granitoids. Two contrasting rock types have been recognized. The low Nb-Ta type rhyolites are mainly associated with the first phase of the Tarim flood basalt magmatism at ~ 290 Ma. They are characterized by negative Nb-Ta anomalies, low ?Nd(t) and ?Hf(t) values, and high 87Sr/86Sr(t) and ?18Ozircon values, consistent with a derivation from continental crustal source. The high Nb-Ta type rhyolites and their plutonic equivalents are associated with the second episode of Tarim magmatism (283-272 Ma). They are characterized by small negative to positive Nb-Ta anomalies, oceanic island basalt (OIB)-like trace element ratios, low 87Sr/86Sr(t) and high ?Nd(t) and ?Hf(t) values. These high Nb-Ta rhyolites are best interpreted as hybrid products of crystal fractionation of mafic magmas, coupled with crustal assimilation. The temporal and compositional evolution of the Tarim rhyolites reflects various extents of thermal and mass exchange between mantle-derived basaltic magma and crustal material above a mantle plume. When the plume head rises to the base of the Tarim craton, it first melts enriched components in the lithospheric mantle (~ 290 Ma), part of which may have ponded near the crust-mantle boundary and induced crustal anatexis leading to the formation of the low Nb-Ta type rhyolites. At ~ 280 Ma, large magma chambers and plumbing systems were formed due to increasing magma supply rate during decompression melting of the mantle plume. This led to the formation of a mafic-ultramafic and felsic association of which the high Nb-Ta type rhyolites are a part.

Liu, Hai-Quan; Xu, Yi-Gang; Tian, Wei; Zhong, Yu-Ting; Mundil, Roland; Li, Xian-Hua; Yang, Yue-Heng; Luo, Zhen-Yu; Shang-Guan, Shi-Mai

2014-09-01

320

Geochronology and geochemistry of late Paleozoic volcanic rocks on the western margin of the Songnen-Zhangguangcai Range Massif, NE China: Implications for the amalgamation history of the Xing'an and Songnen-Zhangguangcai Range massifs  

NASA Astrophysics Data System (ADS)

We here elucidate the tectonic evolution of the Xing'an and Songnen-Zhangguangcai Range massifs during the early Carboniferous-early Permian, based on zircon U-Pb dating and whole-rock geochemical analyses of volcanic rocks of the Songnen-Zhangguangcai Range Massif in the Sunwu area, Heilongjiang Province, NE China. Euhedral-subeuhedral zircons from three rhyolites and one dacite from the study area display fine-scale oscillatory growth zoning, indicating a magmatic origin. Zircon U-Pb dating by LA-ICP-MS indicates that these acidic volcanic rocks formed in the early Carboniferous-early Permian; i.e., early Carboniferous (~ 351 Ma), early late Carboniferous (~ 319 Ma), and early Permian (295-293 Ma). The early Carboniferous rhyolites exhibit chemical affinities to A-type rhyolites, implying an extensional environment. Their positive ?Hf(t) values (+ 8.67 to + 13.4 except for one spot of + 1.63) and Hf two-stage model ages (TDM2 = 562-988 Ma) indicate that the primary magma was possibly derived from partial melting of newly accreted continental crust. The early late Carboniferous rhyolites and dacites (~ 319 Ma) exhibit calc-alkaline peraluminous signature [molar Al2O3/(CaO + K2O + Na2O) ratio, or A/CNK = 1.04-1.22]. The ?Hf(t) values and TDM2 ages of zircons from the 319 Ma dacites are in the range of + 5.33 to + 9.32 and 907-1268 Ma, respectively, suggesting that the primary magma was derived from partial melting of newly accreted crust. The early Permian rhyolites (295-293 Ma) show chemical affinities to A-type rhyolites, implying an extensional tectonic environment; their positive ?Hf(t) values (+ 8.82 to + 13.8) and Hf two-stage model ages (484-743 Ma) indicate that the primary magma was derived from partial melting of newly accreted crust. Combined with the geochemical features of coeval igneous rocks from the eastern margin of the Xing'an Massif, these data reveal the late Paleozoic tectonic history and relationships of the Xing'an and Songnen-Zhangguangcai Range massifs, i.e., early Carboniferous westward subduction of the Paleo-Asian oceanic plate beneath the Xing'an Massif, followed by early late Carboniferous collision and amalgamation of microcontinental blocks, and early Permian post-collisional extension.

Li, Yu; Xu, Wen-Liang; Wang, Feng; Tang, Jie; Pei, Fu-Ping; Wang, Zi-Jin

2014-09-01

321

Petrogenesis, geochronology, and tectonic significance of granitoids in the Tongshan intrusion, Anhui Province, Middle-Lower Yangtze River Valley, eastern China  

NASA Astrophysics Data System (ADS)

The Tongshan copper deposit in Anhui Province is a typical mid-sized skarn and porphyry type deposit in the Anqing-Guichi district along the Middle-Lower Yangtze River Valley, eastern China. The Tongshan intrusion is closely related to this mineralization. The intrusion mainly comprises rocks that are quartz diorite porphyry, quartz monzonite porphyry, and granodiorite porphyry. Plagioclase in these rocks is mostly andesine (An = 31.0-42.9), along with minor oligoclase. Biotite is magnesium-rich [Mg/(Mg + Fe) = 0.52-0.67] and aluminum-poor (Al2O3 = 12.32-14.09 wt.%), and can be classified as magnesio-biotite. Hornblende is TiO2-poor (<1.96 wt.%) and magnesium-rich [Mg/(Mg + Fe) > 0.60], and is magnesio-hornblende or edenite. The SHRIMP zircon U-Pb age of the quartz monzonite porphyry is 145.1 ± 1.2 Ma, which corresponds to the middle Yanshanian period. Whole-rock geochemical results show that the rocks are silica-rich (SiO2 = 60.23-66.23 wt.%) and alkali-rich (K2O + Na2O = 4.97-8.72 wt.%), and low in calcium (CaO = 2.61-5.66 wt.%). Trace element results show enrichments in large ion lithophile element (e.g., K, Rb, and Ba) and depletions in some high field strength elements (e.g., Nb, Ta, P, and Ti). The total rare earth element (REE) content of the rocks is low (?REE < 200 ?g/g), and they exhibit light REE enrichment [(La/Yb)N > 10] and small positive Eu anomalies (average ?Eu = 1.16). These mineralogical, geochronological, and geochemical results show that the intrusion has a mixed crust-mantle source. The Tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust. Hornblende thermobarometry yielded magmatic crystallization temperatures of 652-788 °C and an average crystallization pressure of 1.4 kbar, which corresponds to a depth of approx. 4.7 km. Biotite thermobarometry yielded similar temperatures and lower pressures of 735-775 °C and 0.6 kbar (depth 2.1 km), respectively. The parental magma had a high oxygen fugacity and was produced in a volcanic arc setting related to subduction of the paleo-Pacific plate.

Zhang, Zhi-Yu; Du, Yang-Song; Teng, Chuan-Yao; Zhang, Jing; Pang, Zhen-Shan

2014-01-01

322

Geochemistry and U-Pb SHRIMP zircon chronology of granitoids and microgranular enclaves from Jhirgadandi Pluton of Mahakoshal Belt, Central India Tectonic Zone, India  

NASA Astrophysics Data System (ADS)

The northern part of Central India Tectonic Zone (CITZ) is delineated by an arc-shaped supracrustal belt commonly referred to as Mahakoshal Belt, which is considered as a product of intense rifting of sialic crust that occurred at ca 2400-2600 Ma. Several granitoid plutons intrude the Parsoi Formation of Mahakoshal Belt. Among these, an elliptical small stock-like granitoid body trending E-W is exposed in and around Jhirgadandi region of Mahakoshal Belt, referred herein as Jhirgadandi Pluton. It is composed of minor amount of mafic rocks (diorite) and predominant granitoids. Country-rock pelitic xenoliths and microgranular enclaves (ME) are commonly hosted in granitoids but are absent in diorite. The ME exhibit typical magmatic texture with a Bt(±Cpx ± Hbl)-Pl-Kf-Qtz-Mag-Ap assemblage, similar to that in host granitoids but with contrasting mineral proportions. Whole-rock molar Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios of diorite (0.63-0.72), ME (0.69-1.21) and granitoids (0.83-1.05) suggest their nature largely metaluminous (I-type) to rarely peraluminous (S-type) granitoids. On most binary plots involving silica, two distinct compositional paths can be recognized; one formed by an array of differentiating diorite and ME, and another by fractionating granitoids gradually depleting in compatible elements. It is most likely that ME were generated by progressive and concurrent mixing of coeval pristine mafic (diorite) and granitoid magmas and fractionation processes. However, coherent and identical trace elements (except for Sr, Th, Y and Ni) and REE patterns for ME-granitoid pairs most likely suggest partial to near-complete chemical equilibration through varying degrees of diffusion process across the ME - partly crystalline host granitoid boundary. High-precision U-Pb SHRIMP zircon 206Pb/238U ages for ME (1758 ± 19 Ma) and host granitoid (1753 ± 9.1 Ma) from Jhirgadandi Pluton further support the notion that they were coeval. The obtained age (˜1750 Ma) of Jhirgadandi Pluton also points to the existence and role of Super-Columbian continental component in the evolution of Mahakoshal Belt of the CITZ.

Bora, Sita; Kumar, Santosh; Yi, Keewook; Kim, Namhoon; Lee, Tae Ho

2013-07-01

323

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

324

Lanthanum and neodymium solubility in simplified SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-Al{sub 2}O{sub 3}-CaO high level waste glass  

SciTech Connect

Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigated for SiO{sub 2}B{sub 2}O{sub 3}Na{sub 2}OAl{sub 2}O{sub 3}CaO compositions quenched from 1200 degrees C, for varying La /(La + Nd) (atomic) and increasing rare-earth oxides contents. In this system and beyond the solubility limit, rare-earths (RE) elements are reported to form apatite phases with the general formula Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}. In the current study, speciation of these trivalent RE{sup 3+} cations in both amorphous network and crystal phases was determined from X-ray diffraction, scanning electron microscopy, optical absorption at 10 K, Raman spectroscopy, and electron probe microanalysis. It appeared that RE{sub 2}O{sub 3} solubility was higher for La -rich formulations than for Nd -rich ones and that an increase in the RE oxide content reduces the connectivity of the network building units through formation of non-bridging oxygens at the expense of the oxygen bridges. This depolymerization of the glass network did not affect neodymium environment which consisted in silicate tetrahedra. The composition of the apatite crystals was found to be affected by the La /(La + Nd) of the parent glass and deviation from the ideal composition (Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}) occurred in the neodymium end of the system. It thus appears that both RE{sub 2}O{sub 3} solubility and crystal composition are strongly dependent on the type and crystal chemistry of the RE elements. (authors)

Kidari, Abdessamad; Bardez-Giboire, Isabelle [CEA, DEN, DTCD/SECM/LDMC - Marcoule, Bagnols-sur-Ceze F-30207, (France); Dussossoy, Jean-Luc; Magnin, Magali [CEA, DEN, DTCD/SECM/LMPA - Marcoule, Bagnols-sur-Ceze F-30207, (France); Brackx, Emmanuelle [CEA, DEN, DTEC/SGCS/LMAC - Marcoule, Bagnols-sur-Ceze F-30207, (France); Caurant, Daniel [Ecole Nationale Superieure de Chimie de Paris, Laboratoire de Chimie de la Matiere Condensee de Paris, UMR CNRS 7574, Paris, (France)

2012-08-15

325

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

326

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 Na 2O 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 La N/Yb N = 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 La N/Yb N = 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 La N/Yb N = 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 Gd N/Yb N-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 (K 2O/Na 2O, La N/Yb N, La N/Sm N, 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

327

Caos en el mercado de commodities  

Microsoft Academic Search

Este artículo aplica seis técnicas y herramientas (análisis gráfico, gráfico de recurrencia, entropía de espacio temporal, coeficiente de Hurst, exponente de Lyapunov y dimensión de correlación), a las series de retornos del cobre, oro, petróleo, plata, zinc, aluminio, plomo y níquel, con el fin de corroborar la existencia de un comportamiento caótico en el mercado de commodities. Se encuentra evidencia

Christian Espinosa Méndez

2010-01-01

328

THE CAOS PROJECTS (COMPUTER ASSISTED ORTHOPAEDIC SYSTEMS)  

Microsoft Academic Search

Recent technological advances in electronics, robotics, software engineering and reduction in hardware costs have been accompanied by increasing pressure on theatre time and reductions in health care spending. The above has coincided with technical innovations in orthopaedics, increasing awareness of the hazards of low dose radiation, greater patient expectations and the need to decrease morbidity associated with the learning phase

A. M. M. A. MOHSEN; T. J. Cain; K. P. Sherman; M. R. K. Karpinski; R. Phillips; K. D. F. Dyer; J. G. Griffiths; B. C. Tompsett; W. J. Viant; G. Kirkham; G. F. Remy; M. A. Bell

329

Carbonatization of oceanic crust by the seafloor hydrothermal activity and its significance as a CO2 sink in the Early Archean1  

NASA Astrophysics Data System (ADS)

Early Archean (3.46 Ga) hydrothermally altered basaltic rocks exposed near Marble Bar, eastern Pilbara Craton, have been studied in order to reveal geological and geochemical natures of seafloor hydrothermal carbonatization and to estimate the CO 2 flux sunk into the altered oceanic crust by the carbonatization. The basaltic rocks are divided into basalt and dolerite, and the basalt is further subdivided into type I, having original igneous rock textures, and type II, lacking these textures due to strong hydrothermal alteration. Primary clinopyroxene phenocrysts are preserved in some part of the dolerite samples, and the alteration mineral assemblage of dolerite (chlorite + epidote + albite + quartz ± actinolite) indicates that the alteration condition was typical greenschist facies. In other samples, all primary minerals were completely replaced by secondary minerals, and the alteration mineral assemblage of the type I and type II basalts (chlorite + K-mica + quartz + carbonate minerals ± albite) is characterized by the presence of K-mica and carbonate minerals and the absence of Ca-Al silicate minerals such as epidote and actinolite, suggesting the alteration condition of high CO 2 fugacity. The difference of the alteration mineral assemblages between basalt and dolerite is probably attributed to the difference of water/rock ratio that, in turn, depends on their porosity. Carbonate minerals in the carbonatized basalt include calcite, ankerite, and siderite, but calcite is quite dominant. The ? 13C values of the carbonate minerals are -0.3 ± 1.2‰ and mostly within the range of marine carbonate, indicating that the carbonate minerals were formed by seafloor hydrothermal alteration and that carbonate carbon in the altered basalt was derived from seawater. Whole-rock chemical composition of the basaltic rocks is essentially similar to that of modern mid-ocean ridge basalt (MORB) except for highly mobile elements such as K 2O, Rb, Sr, and Ba. Compared to the least altered dolerite, all altered basalt samples are enriched in K 2O, Rb, and Ba, and are depleted in Na 2O, reflecting the presence of K-mica replacing primary plagioclase. In addition, noticeable CO 2 enrichment is recognized in the basalt due to the ubiquitous presence of carbonate minerals, but there was essentially neither gain nor loss of CaO. This suggests that the CO 2 in the hydrothermal fluid (seawater) was trapped by using Ca originally contained in the basalt. The CaO/CO 2 ratios of the basalt are generally the same as that of pure calcite, indicating that Ca in the basalt was almost completely converted to calcite during the carbonatization, although Mg and Fe were mainly redistributed into noncarbonate minerals such as chlorite. The carbon flux into the Early Archean oceanic crust by the seafloor hydrothermal carbonatization is estimated to be 3.8 × 10 13 mol/yr, based on the average carbon content of altered oceanic crust of 1.4 × 10 -3 mol/g, the alteration depth of 500 m, and the spreading rate of 1.8 × 10 11 cm 2/yr. This flux is equivalent to or greater than the present-day total carbon flux. It is most likely that the seafloor hydrothermal carbonatization played an important role as a sink of atmospheric and oceanic CO 2 in the Early Archean.

Nakamura, Kentaro; Kato, Yasuhiro

2004-11-01

330

The petrogenesis and tectonic implications of the granitoid gneisses from Xingxingxia in the eastern segment of Central Tianshan  

NASA Astrophysics Data System (ADS)

As part of Central Asian Orogenic Belt (CAOB), the Central Tianshan zone plays a crucial role in the reconstruction of the tectonic evolution of the CAOB. Furthermore, it is bordered by the Tarim Craton to the south, and the comparable evolutionary history between them enables the Central Tianshan zone to provide essential information on the crustal evolution of the Tarim Craton. The eastern segment of the Central Tianshan tectonic zone is characterized by the presence of numerous Precambrian metamorphic rocks, among which the Xingxingxia Group is the most representative one. The granitoids gneisses, intruded into the Xingxingxia Group, consist of two major lithological assemblages: (1) biotite-monzonitic gneisses and (2) biotite-plagioclase gneisses. These metamorphosed granitoid rocks are characterized by enrichment in SiO2, Al2O3 and K2O and depletion in MgO and FeOT. The Rittmann index (?) spreads between 1.44 and 2.21 and ACNK (Al2O3/(CaO + Na2O + K2O)) ranges from 1.03 to 1.08, indicating that these granitoid gneisses are high-K calc-alkaline and peraluminous. Trace element data indicate that the studied samples are enriched in LREE with moderate REE fractionated patterns ((La/Yb)N = 10.5-75.3). The concentrations of HREE of the garnet-bearing gneisses are significantly higher than those of garnet-free gneisses. The former show pronounced negative Eu anomalies (Eu/Eu* = 0.32-0.57), while the latter are characterized by negligible negative Eu anomalies to moderate positive Eu anomalies (Eu/Eu* = 0.80-1.35). In addition, the enrichment of LILE (Rb, Th, K, Pb) and depletion of HFSE (Ta, Nb, P, Ti) of the examined granitoid gneisses are similar to typical volcanic-arc granites. Zircons U-Pb dating on the biotite monzonitic gneiss yields a weighted mean 206Pb/238U age of 942.4 ± 5.1 Ma, suggesting their protoliths were formed in the early Neoproterozoic, which is compatible with the time of the assembly of supercontinent Rodinia. The zircons have a large ?Hf(t) variation from -5.6 to +3.2, suggesting that both old crust-derived magmas and mantle-derived juvenile materials contributed to the formation of their protoliths. Based on field observation, and petrological, geochemical and geochronological investigations, we infer that the granitoid gneisses from Xingxingxia were probably formed on a continental arc that resulted from the interaction of Australia and the Tarim Craton during the assembly of the Rodinia supercontinent, and that the Central Tianshan zone was a part of the Tarim Craton during that time. Besides, the Grenvillian orogenic events may have developed better in the Tarim Craton than previously expected.

Wang, Zhong-Mei; Han, Chun-Ming; Xiao, Wen-Jiao; Su, Ben-Xun; Sakyi, Patrick Asamoah; Song, Dong-Fang; Lin, Li-Na

2014-07-01

331

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

332

Experimental investigations of low-Ca pyroxene stability and olivine-pyroxene-liquid equilibria at 1-atm in natural basaltic and andesitic liquids  

NASA Astrophysics Data System (ADS)

This paper reports experiments carried out at 1-atm under conditions of controlled oxygen fugacity, using natural andesites and andesite mixed with augite+synthetic pigeonite or augite+orthopyroxene. The experimental results are used (1) to investigate the controls of Mg# (Mg/[Mg+Fe2+]) and temperature on low-Ca pyroxene stability (pigeonite vs orthopyroxene), (2) to quantify the effects of variations in bulk composition on the position of multiple saturation boundaries in mineral component projection schemes and (3) to develop a thermodynamic model for silica activity for melts saturated with olivine and pyroxene. Over the Mg# range of 0.80 0.30 the minimum temperature of pigeonite stability in natural compositions is equivalent to the Lindsley (1983) boundary determined for pure Ca-Mg-Fe pigeonites. For the low variance, 5-phase assemblage oliv-aug-low-Ca pyroxene-plag-liquid, expressions involving liquid (Na2O+K2O)/(Na2O+K2O+CaO),Mg# and TiO2 content predict temperature and the movement of multiple saturation boundaries in pseudoternary projections in response to changing melt composition. The equilibrium for the low pressure melting of low-Ca pyroxene to olivine+liquid is formulated as a geothermometer and monitor of silica activity. Equilibrium constants estimated from thermochemical data and activities calculated for experimentally produced olivine and pyroxenes are used to develop a model for silica activity in liquid.

Grove, T. L.; Juster, T. C.

1989-11-01

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

New data on selected Ivory Coast tektites.  

NASA Technical Reports Server (NTRS)

Fourteen Ivory Coast tektites exhibit a range of bulk indices of refraction of 1.5156 to 1.5217 plus or minus 0.0004 and of bulk specific gravities of 2.428 to 2.502 plus or minus 0.005. Seven of these Ivory Coast (IVC) tektites were analyzed for major and minor element content. Compared to tektites from other strewn fields, their SiO2 content is low (67.2-69.1%), Al2O3 relatively high (15.8-16.8%), and total iron relatively high but with a more restricted range (6.3-6.8% as FeO). Their lime content is low (0.71-1.35%) compared to Australasian tektites but their MgO/CaO ratio (about 3.1) is unusually high. All other tektite groups have Na2O/K2O ratios less than unity, but the Na2O/K2O ratio of the IVC tektites is slightly greater than unity. Their K/Rb ratios range from 200 to 256 and average 227.

Cuttitta, F.; Carron, M. K.; Annell, C. S.

1972-01-01

335

A petrologic study of the Teanaway Basalt: Eocene slab window volcanism in central WA  

NASA Astrophysics Data System (ADS)

The Teanaway Basalt (TB) includes subaerial basalt to andesite flows, mafic to felsic tuffs, and rhyolite domes in the Central Cascades of Washington State. These volcanics overlie the extensive ~47 Ma Teanaway Dike Swarm (TDS) that cuts the underlying Swauk Formation. This study focuses on the tectonic setting of eruption and geochemical variations relating to geography and stratigraphy within the TB. The western-most area of the TB, Easton Ridge (ER), is compared with the eastern-most area of the TB, Liberty Ridge (LR) - 40 km to the east of ER. The bimodal TB consists predominantly of basaltic andesite and andesite (45.3-63.1 wt% SiO2) with subordinate rhyolite (75.9-79.4 wt% SiO2). The mafic rocks classify as primarily medium-K tholeiites (0.1-3.0 wt% K2O), but a few samples classify as alkaline. Enrichment in LILE and depletion in HFSE on spidergrams are indicative of an arc setting. However, compared with the modern Cascade Arc, the TB is distinctly higher in Fe2O3T (8.8-17.1 wt%) and TiO2 (1.1-2.7 wt%), and distinctly lower in Al2O3 (11.2-14.6) and K2O, with a similar range of Mg #s (0.15-0.48). Most tectonic discrimination plots characterize the TB as MORB, but some indicate an arc or within-plate setting. Preliminary Pb isotopic data (206Pb/204Pb = 19.13-19.19, 207Pb/204Pb = 15.62-15.64, and 208Pb/204Pb = 38.78-38.90) indicate the TB and TDS are more enriched than Cascade Arc rocks in 206Pb/204Pb and 208Pb/204Pb. Overall, these geochemical data are consistent with a model in which asthenospheric mantle ascending through a slab window interacts with mantle wedge that has previously acquired arc chemical traits. The existence of a slab window in this region during the mid-Eocene is compatible with plate reconstructions and evidence of extension that have been attributed to subduction of the Resurrection-Kula ridge (Haeussler et al., 2003). Harker plots show lavas at LR are generally more enriched than those at ER in Fe2O3T (11.9-17.1 wt% vs 8.8-15.7 wt%) MnO (0.16-0.28 wt% vs 0.11-0.24 wt%), and TiO2 (1.2-2.4 wt% vs 0.8-2.7 wt%), and have a narrower range of CaO (1.5-9.4 wt%) and Na2O (1.5-3.3 wt%) concentrations. Both LR and ER samples display modest LREE enrichment (La/Yb = 2.1-3.7) and similar incompatible element ratios, suggesting similar sources. ER samples show a broader range of REE contents but extend to lower levels, and have smaller negative Eu anomalies (Eu/Eu* = 0.55-0.96). Pearce element ratio plots suggest much of the variation reflects different degrees of plag+cpx fractionation. Alkaline lavas are restricted to ER and the central area of the TB. Differences in concentration at similar Mg# (most notably in Fe2O3T, TiO2, MnO, and Na2O) suggest multiple parent magmas, probably from similar mantle sources. With increasing stratigraphic height in the ~1.6 km thick LR section, there are general decreases in SiO2 (60 to 54 wt%), and general increases in CaO (4 to 8 wt%), MnO (0.1-0.15 wt%), and P2O5 (0.2-0.65 wt%). Mg# displays several cycles of decrease followed by increase, each extending over 400-1000m. These trends are suggestive of an evolving system that experienced multiple replenishment events.

Roepke, E.; Tepper, J. H.; Ivener, D.

2013-12-01

336

Optical character of Er 3+\\/Yb 3+ co-doped P 2O 5–CaO–Na 2O–Al 2O 3–AgO phosphate glass  

Microsoft Academic Search

The up-conversion (UC) and near infrared (NIR) luminescence of Er3+\\/Yb3+ co-doped phosphate glass are investigated. In the UC emission range, the 523nm, 546nm green emissions and the 659nm red emission are observed. With the increasing pump power, the intensity ratios of I523\\/I659, I546\\/I659 and I523\\/I546 increase gradually. The phenomenon is reasonably interpreted by theoretical analysis based on steady state rate

Chengguo Ming; Feng Song; Yin Yu; Gong Zhang; Qingru Wang; Hua Yu; Tongqing Sun; Jianguo Tian

2011-01-01

337

The effects of Na 2O\\/SiO 2 molar ratio, curing temperature and age on compressive strength, morphology and microstructure of alkali-activated fly ash-based geopolymers  

Microsoft Academic Search

Fly ashes (FA) are byproducts of electricity production from mineral coal in thermoelectric power plants. The pozzolanic properties of FA have been utilized in various applications, including structural concrete, yet the large part of FA is still discarded into the environment. To promote greater FA usage, this study aims to produce a dense matrix, with mechanical properties satisfactory for civil

Alexandre Silva de Vargas; Denise C. C. Dal Molin; Antônio C. F. Vilela; Felipe José da Silva; Bruno Pavão; Hugo Veit

2011-01-01

338

Spectral analysis of Er3+-, Er3+\\/Yb3+- and Er3+\\/Tm3+\\/Yb3+-doped TeO2 ZnO WO3 TiO2 Na2O glasses  

Microsoft Academic Search

In this paper, we present the spectroscopic properties of Er3+-, Er3+\\/Yb3+- and Er3+\\/Tm3+\\/Yb3+-doped novel tellurite glasses. From the measured absorption spectra, Judd-Ofelt (JO) intensity parameters (Omega2, Omega4 and Omega6) have been evaluated for the Er3+-doped glass. With 980 nm excitation three strong upconversion emission bands centered at 505, 520 and 630 nm were observed for both Er3+- and Er3+\\/Yb3+-codoped glasses

G. Lakshminarayana; Jianrong Qiu; M. G. Brik; G. A. Kumar; I. V. Kityk

2008-01-01

339

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

340

Acidulated pegmatitic mica: A promising new multi-nutrient mineral fertilizer  

Microsoft Academic Search

Scrap grade pegmatitic phlogopite mica contains 5–7% K (~8% K2O), 10–14% Mg (~23% MgO), 1–2% Ca (~2.9% CaO), 0.03% Mn and 109 ppm Zn. On acidulation upto 65% of K and Mg and 15–100% Mn and Zn were recovered. Less than 13% of Ca was recovered in solution. Water soluble and Nh4OAc extractable K and Mg of acidulated mica of

T. J. Weerasuriya; S. Pushpakumara; P. I. Cooray

1993-01-01

341

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.

342

Nickel speciation in multi-oxydes components silicate glasses: new UV-VIS-NIR spectroscopic results and geochemical implications  

NASA Astrophysics Data System (ADS)

Silicate glasses are usually considered as good analogues for natural melts and thus frequently synthesized to study their structural properties. The optical spectra of Nickel are well constrained in crystal phases [1]. Only recent studies permit real advances of Ni speciation in glasses [2, 3]. In alkali and alkaline-earth silicate glasses, Ni2+is always found as predominantly [5]Ni2+ with some minor [4]Ni2+, whereas in borosilicate and borate glasses with the same network modifying cations, Nickel could be observed as [4]Ni2+, [5]Ni2+ and/or [6]Ni2+, depending on the glass composition and especially on the proportion and nature of alkali/ alkaline-earth cations. The short-range structure of a new large compositional range of Ni-doped (1000 ppm) multi-oxides silicate glasses has been investigated by UV-VIS-NIR spectroscopy. The glasses were synthesized to study the separate and combined influences of alkali (K, Na), alkaline-earth elements (Ca, Mg) and Al on Ni speciation. First, our spectral results on non-magnesian system confirm a high [4]Ni2+ content in silico-potassic (11.5 to 28.7 wt.% K2O) glasses compared to the predominance of [5]Ni2+ (± [4]Ni2+) in purely silico-sodic glasses (15 to 27.5 wt.% Na2O) and a mixing of variable proportions of [4]Ni2+ and [5]Ni2+ in mixed chemical compositions (Si-K-Ca and Si-Na-Ca with each element varying independently from ~10 to ~25 wt.%). Mixed Si-K-Ca glasses (fixed ~10 wt.% K2O and 9.1 to 26.4 wt.% CaO) show significant [5]Ni2+ spectral band appearance with the increase of Ca concentration. At constant Ca (~10 wt.% CaO) and variable K (14.3 to 29.7 wt.% K2O), [4]Ni2+ spectral band intensities remain predominant. Na rich silicate glasses always favor [5]Ni2+while, for high K concentration, Ni2+ is mainly found as [4]Ni2+. This behaviour of Ni2+ as a function of glass composition is coherent with [4]Ni2+ being predominant in presence of large charge compensating, low field strength cations such as K. In that case, Ni2+ is found in network forming position but does not take that role because of its low charge as compared to network forming cations such as Si4+. With higher field strength cations such as Ca or Na, Ni2+is mostly found as network modifier. Al3+ ? Si4+ substitution (15 wt.% Al2O3) in alkali-alkaline earth systems show clear decrease of [4]Ni2+ spectral band intensities revealing preferential use of Na+ and Ca2++ Na+ to charge compensate oxygen anions associated to Al3+. This reveals the importance of the competition between cations for the charge compensating effect. [6]Ni2+ in glasses has only been observed in borate ones with low alkali content [4]. Our results on the structural investigation of pseudo-basaltic magnesian glasses (CMNAS system with 7 to 20 wt.% MgO) show first evidences of combined presence of [6]Ni2+, [5]Ni2+ and [4]Ni2+ in purely silicate glasses. The presence of the 3A2g(F) - 3T2g(P) electronic transition on the optical spectra of the investigated glasses allow identification of [6]Ni2+. The intensity of the band corresponding to this transition increases at the expense of the [5]Ni2+ band in relation with the increase of the MgO content of the glass. The discovery of the MgO addition effect on Ni coordination with the appearance of [6]Ni2+ gives new insights on the olivine-liquid partitioning of Ni. According to our results, the resulting effect would be an increase affinity of Ni for a melt with high MgO content, considering the glass to be a snapshot of the liquid structure. This could explain, the partition coefficient (DNiol-liq) decrease coupled with the increase of the MgO content of the equilibrium melt observed in several experimental studies [5]. [1] Burns, Mineralogical Applications of crystal field theory, Cambridge University Press, 1993. [2] Galoisy, L. & Calas, G., 1993a, Structural environment of Nickel: Part 1. Spectroscopic determination of coordination states, Geochem. Cosmochim. Acta., 57, 3613 - 3626. [3] Galoisy L., Calas G., Cormier L., Marcq B and Thibault M.H., 2005, Overview of the environment of Ni in oxide

Antoine, Bénard; Laurence, Galoisy; Georges, Calas

2010-05-01

343

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

344

The age and origin of felsic intrusions of the Thetford Mines ophiolite, Quebec.  

USGS Publications Warehouse

This ophiolite was obducted in the early Ordovician during the closing of the proto-Atlantic. The tectonized peridotite of the lower unit of the ophiolite is intruded by felsic dykes and pods, including isolated lenses of massive rodingite, small bodies of strongly deformed diorite, and younger, less deformed monzonite. These intrusions are found only near the base of the ophiolite, and are considered to have been emplaced before the ophiolite reached its present position. The young group of intrusions consists of biotite-muscovite quartz monzonite and leuco-quartz monzonite. Analysed samples have high K2O, high (K2O X 100)/Na2O + K2O) ratios, and high initial Sr ratios, indicating that the magma source was continental and that these felsic rocks formed by partial melting of continental sediments. Whole-rock and mineral isochron ages suggest that the felsic intrusions are approx 456 + or - 4 m.y. old and that they were metamorphosed approx 418 + or - 7 m.y. ago. The detachment of the ophiolite occurred approx 491 + or - 3 m.y. ago. The felsic dykes were intruded approx 35 m.y. later, during the Taconic orogeny. The lengthy time between detachment and final nappe emplacement recorded by the felsic dykes may be a requirement for formation of abundant asbestiform chrysotile. Whole-rock analyses (16) and Rb, Sr and 87Sr/86Sr data from the Colline de Granite, King Mts., Vimy Ridge and Black Lake samples are presented.-P.Br.

Clague, D.A.; Frankel, C.S.; Eaby, J.S.

1985-01-01

345

Study on the laser-induced darkening in Nd-doped laser glasses  

Microsoft Academic Search

Laser induced darkening in the soda-lime silicate (15Na2O·15CaO·70SiO2) based glass and type N31 barium metaphosphate Ba(PO3)2 based glass were studied by exposing the glass samples in frequency-quadrupled Nd:YAG (266 nm, 5 ns) laser and Ti:Sapphire (800 nm, 120 fs) laser. Both types of the glasses were doped with Nd2O3 at doping levels less than 3 wt%. Hole center HC1 formed

Qinling Zhou; Lei Xu; Liying Liu; Wencheng Wang; Congshan Zhu; Fuxi Gan

2004-01-01

346

Fluoride-containing bioactive glasses: Fluoride loss during melting and ion release in tris buffer solution  

Microsoft Academic Search

Melt-derived bioactive glasses (SiO2–P2O5–CaO–Na2O–CaF2; CaF2 0 to 17.76mol%) lost fluoride during melting, but nominal and analysed CaF2 contents in the glass correlated linearly. Analysed CaO contents were increased, showing that fluoride was lost as hydrofluoric acid after reaction with atmospheric water during melting. Weight loss on ignition reduced linearly with increasing CaF2, suggesting that CaF2 impedes absorption of atmospheric water.

Delia S. Brauer; Mohammed Mneimne; Robert G. Hill

2011-01-01

347

Bioactivity of electro-thermally poled bioactive silicate glass  

Microsoft Academic Search

A 45S5 bioactive glass (nominal composition: 46.1mol.% SiO2, 2.6mol.% P2O5, 26.9mol.% CaO, 24.4mol.% Na2O) was electrothermally poled by applying voltages up to 750V for 45min at 200°C, and the thermally stimulated depolarization currents (TSDCs) were recorded. Changes in chemical composition and electrical properties after poling were investigated by TSDC measurements, impedance spectroscopy and scanning electron microscopy with energy dispersive X-ray

C. R. Mariappan; D. M. Yunos; A. R. Boccaccini; B. Roling

2009-01-01

348

Influence of sodium content on the properties of bioactive glasses for use in air abrasion.  

PubMed

Air abrasion is used in minimally invasive dentistry for preparing cavities, while removing no or little sound dentine or enamel, and the use of bioactive glass (rather than alumina) as an abrasive could aid in tooth remineralization. Melt-derived bioactive glasses (SiO2-P2O5-CaO-CaF2-Na2O) with low sodium content (0 to 10 mol% Na2O in exchange for CaO) for increased hardness, high phosphate content for high bioactivity and fluoride content for release of fluoride and formation of fluorapatite were produced, and particles between 38 and 80 µm in size were used for cutting soda-lime silicate glass microscope slides and human enamel. Vickers hardness increased with decreasing Na2O content, owing to a more compact silicate network in low sodium content glasses, resulting in shorter cutting times. Cutting times using bioactive glass were significantly longer than using the alumina control (29 µm) when tested on microscope slides; however, glasses showed more comparable results when cutting human enamel. The bioactive glasses formed apatite in Tris buffer within 6 h, which was significantly faster than Bioglass® 45S5 (24 h), suggesting that the hardness of the glasses makes them suitable for air abrasion application, while their high bioactivity and fluoride content make them of interest for tooth remineralization. PMID:24287337

Farooq, Imran; Tylkowski, Maxi; Müller, Steffen; Janicki, Tomasz; Brauer, Delia S; Hill, Robert G

2013-12-01

349

Chemical Analyses of Pre-Holocene Rocks from Medicine Lake Volcano and Vicinity, Northern California  

USGS Publications Warehouse

Chemical analyses are presented in an accompanying table (Table 1) for more than 600 pre-Holocene rocks collected at and near Medicine Lake Volcano, northern California. The data include major-element X-ray fluorescence (XRF) analyses for all of the rocks plus XRF trace element data for most samples, and instrumental neutron activation analysis (INAA) trace element data for many samples. In addition, a limited number of analyses of Na2O and K2O by flame photometry (FP) are included as well assome wet chemical analyses of FeO, H2O+/-, and CO2. Latitude and longitude location information is provided for all samples. This data set is intended to accompany the geologic map of Medicine Lake Volcano (Donnelly-Nolan, in press); map unit designations are given for each sample collected from the map area.

Donnelly-Nolan, Julie M.

2008-01-01

350

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

351

87Sr 86Sr ratios for basalt from Loihi Seamount, Hawaii  

USGS Publications Warehouse

87Sr 86Sr ratios of 15 samples of basalt dredged from Loihi Seamount range from 0.70334 to 0.70368. The basalt types range from tholeiite to basanite in composition and can be divided into six groups on the basis of abundances of K2O, Na2O, Rb and Sr and 87Sr 86Sr ratio. The isotopic data require that the various basalt types be derived from source regions differing in Sr isotopic composition. The Loihi basalts may be produced by mixing of isotopically distinct sources, but the tholeiites and alkalic basalts from Loihi do not show a well-developed inverse trend between Rb/Sr and 87Sr 86Sr that is characteristic of the later stages of Hawaiian volcanoes such as Haleakala and Koolau. ?? 1983.

Lanphere, M.

1983-01-01

352

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, H.P., Jr.; Hon, K.; Tsvetkov, A.

1996-01-01

353

Metasediments of the Palaeoarchaean Dniester-Bug Suite of the South-Western Ukrainian Shield: composition, age, and sources  

NASA Astrophysics Data System (ADS)

Supracrustal rocks of the Dniester-Bug Suite are the oldest formation of the Ukrainian Shield (Esipchuk et al., 2008). They occur in the south-western shield as enclaves within enderbites. We have documented a W-E trending and subvertical enclave in the Odessa quarry (N 48°13'57", E 29°59'20") composed of mafic metavolcanics and very subordinate metasediments. SIMS zircon ages from a quartzite vary from 3.8 to 3.1 Ga, the majority of concordant values being 3.7-3.5 Ga (Bibikova et al., 2012). Younger metamorphic zircons are also present. In the south this enclave is bounded by a 3.1 Ga old enderbite which contains a xenolith of a metavolcanite identical to those alternating with metasediments (Lobach-Zhuchenko et al., 2012). So, the formation of supracrustals is constrained by the interval 3.4-3.2.Ga. Sedimentary lithologies have been recognised as pure quartzites and garnet, garnet-magnetite, and magnetite quartzites. Metasediments form lenses of different length, and their thickness varies from a few centimetres to 2.5 m. All supracrustal rocks experienced multiple deformation coeval with two high-grade (up to granulite facies) metamorphic events accompanied by migmatization. The second deformation resulted in W-E trending lens-like and banded structures and penetrative steep to vertical mineral and aggregate lineation, which suggests widely developed ductile shearing. Geochemically, the sediments are subdivided into quartzites, alumina-iron quartzites and iron quartzites (Algoma-type IF). High abundances in quartzites and alumina-iron quartzites of Al2O3 (2-8 and 3-20 wt %), CaO (0.9-3.64 and 1.4-3.6 wt %), MgO (0.7-4.4 and 3.5-6.7 wt %), TiO2 (0.07-0.23 and 0.56-1.28 wt %), respectively, and the ratio Na2O/Al2O3 of 0.05-0.20 point to their terrigenic origin. According to Herron's classification of terrigenic rocks (Herron, 1988) predominant sediments are Fe-sandstones; some of rocks correspond to quartz arenites and Fe-Al shales; in addition, Fe quartzites (IF) are present. The high Sc content also suggests the clastic origin of these rocks. The chemical index of alteration (Nesbitt, Young, 1982; 42-48 in quartzites and 40-89 in IF) indicates a weak weathering grade. The Zr-Hf ratio of 30-40 suggests an input of continental component. The K2O/Al2O3 ratio of 0.02-0.07 indicates an important role of plagioclase in an weathering area. Most samples have the concentration of LREE 10-50 times higher, and of HREE 1-9 times higher than in chondrites. The enrichment of LREE is thought to have been due to metamorphism. The IF displays a negative Eu anomaly, which also could have resulted from metamorphism (Fryer, 1983). In comparison with the average Algoma-type IF (Gross and McLeod, 1980) IF from the Odessa quarry have lower abundances of Co, Ni, Cr, Zn, and higher abundances of Cu and V; abundances of all transitional metals in the alumina-iron quartzites are higher. The Fe/Mn ratios are of 28-88 in quartzites and 420 in IF, and according to Rosen et al. (1994) these values suggest that sedimentation occurred in shallow basins. Thus, all geochemical features indicate the terrigenic origin of quartzites, Al-Fe quartzites and IF in contrast to most chemical sediments of Archaean Algoma-type IF.

Lobach-Zhuchenko, S. B.; Bibikova, E. V.; Balagansky, V. V.

2012-04-01

354

Chemical composition and mineralogy of borate from Rio Grande deposit, Uyuni (Bolivia) as raw materials for industrial applications  

NASA Astrophysics Data System (ADS)

Bolivia has large tailings as a result of the historic and present-day Sn mining activity developed extensively in that country. Tailings produced in these mining activities have an appropriate composition to reprocess them and make silicate glass and glass-ceramics, obtaining the valorization of wastes and reducing the visual and chemical impact. Reprocessing the wastes to make glass and glass-ceramics prevents the leaching of heavy metals from those wastes because they are retained in the structure of the glass. Furthermore, an option to increase the economic value of these glasses is the introduction of boron and other additives to produce borosilicate glass. In this study a characterization of the Rio Grande borate deposit for its use in the manufacture of borosilicate glass is presented. Mineralogy was determined by X-ray diffraction (XRD), and Fourier transforms infrared spectroscopy (FTIR); textures were observed by scanning electron microscopy (SEM) and chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS). The Rio Grande borate deposit is located in an area of about 50 km2 close to the south of the Salar of Uyuni, in the Río Grande de Lípez Delta. Borates occur in the contact between fluvio-deltaic and lacustrine sediments from water raising the surface by capillarity. The borates crop out in an extent area but towards the west they are covered by fluvio-deltaic sediments, which can be up to 2 m thick. These borates occur as lenses 50-100 m in diameter and layers up to 1 m thick. They usually form brittle nodules with a cotton-ball texture. Chemical composition of the Rio Grande borates is CaO, 11.82-13.83 wt%; Na2O, 13.50-19.35 wt%; K2O, 0.05- 1.04 wt%; MgO, 0.42-1.46 wt%; B2O3, 36.21-42.60 wt%; SiO2, up to 0.53 wt% and SO2, up to 0.60 wt%. Trace elements are low: Sr content is between 151-786 ppm, Al 12-676 ppm, Mn between 1-17 ppm, As 2-10 ppm and Fe between 9-376 ppm. The most abundant borate mineral in this deposit is ulexite (NaCaB5.5H20), halite can reach up to 17 wt% and gypsum up to 1.2 wt.%. Calcite occurs in minor contents. Ulexite exhibits a fibrous morphology with fibers oriented parallel each other. Purity of borates from the Rio Grande deposits makes them suitable for the most restrictive applications. Chemistry of these borates is in accordance with the necessary composition for obtaining borosilicate glasses. Acknowledgements: This work was partly financed by the project AECID: A3/042750/11, and the SGR 2009SGR-00444.

Guillen Vargas, Julio; Arancibia, Jony Roger Hans; Alfonso, Pura; Garcia-Valles, Maite; Parcerisa, David; Martinez, Salvador

2014-05-01

355

Kasatkinite, Ba2Ca8B5Si8O32(OH)3 · 6H2O6, a new mineral from the Bazhenovskoe deposit, the Central Urals, Russia  

NASA Astrophysics Data System (ADS)

A new mineral, kasatkinite, Ba2Ca8B5Si8O32(OH)3 · 6H2O, has been found at the Bazhenovskoe chrysotile asbestos deposit, the Central Urals, Russia in the cavities in rhodingite as a member of two assemblages: (l) on prehnite, with pectolite, calcite, and clinochlore; and (2) on grossular, with diopside and pectolite. Kasatkinite occurs as spherulites or bunches up to 3 mm in size, occasionally combined into crusts. Its individuals are acicular to hair-like, typically split, with a polygonal cross section, up to 0.5 mm (rarely, to 6 mm) in length and to 20 ?m in thickness. They consist of numerous misoriented needle-shaped subindividuals up to several dozen ?m long and no more than 1 ?m thick. Kasatkinite individuals are transparent and colorless; its aggregates are snow white. The luster is vitreous or silky. No cleavage was observed; the fracture is uneven or splintery for aggregates. Individuals are flexible and elastic. The Mohs' hardness is 4-4.5. D meas = 2.95(5), D calc = 2.89 g/cm3. Kasatkinite is optically biaxial (+), ? = 1.600(5), ? = 1.603(2), ? = 1.626(2), 2 V meas = 30(20)°, 2 V calc = 40°. The IR spectrum is given. The 11B MAS NMR spectrum shows the presence of BO4 in the absence of BO3 groups. The chemical composition of kasatkinite (wt %; electron microprobe, H2O by gas chromatography) is as follows: 0.23 Na2O, 0.57 K2O, 28.94 CaO, 16.79 BaO, 11.57 B2O3, 0.28 Al2O3, 31.63 SiO2, 0.05 F, 9.05 H2O, -0.02 -O=F2; the total is 99.09. The empirical formula (calculated on the basis of O + F = 41 apfu, taking into account the TGA data) is: Na0.11K0.18Ba1.66Ca7.84B5.05Al0.08Si8.00O31.80(OH)3.06F0.04 · 6.10H2O. Kasatkinite is monoclinic, space group P21/ c, P2/ c, or Pc; the unit-cell dimensions are a = 5.745(3), b = 7.238(2), c = 20.79 (1) Å, ? = 90.82(5)°, V = 864(1) Å3, Z = 1. The strongest reflections ( d Å- I[ hkl]) in the X-ray powder diffractions pattern are: 5.89-24[012], 3.48-2.1[006], 3.36-24[114]; 3.009-100[, 121, ], 2.925-65[106, , 122], 2.633-33[211, 124], 2.116-29[, 133, 028]. Kasatkinite is named in honor of A.V. Kasatkin (b. 1970), a Russian amateur mineralogist and mineral collector who has found this mineral. Type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Pekov, I. V.; Chukanov, N. V.; Filinchuk, Ya. E.; Zadov, A. E.; Kononkova, N. N.; Epanchintsev, S. G.; Kaden, P.; Kutzer, A.; Göttlicher, J.

2013-12-01

356

Petrogenesis of magmatic albite granites associated to cogenetic A-type granites: Na-rich residual melt extraction from a partially crystallized A-type granite mush  

NASA Astrophysics Data System (ADS)

The uncommon association of cogenetic and nearly contemporaneous potassic K-feldspar A-type granites and sodic albite granites is observed within the 347 Ma-old bimodal Saint-Jean-du-Doigt (SJDD) intrusion, Brittany, France. A-type granites outcrop as small bodies (< 1 km2) of fine-grained, pinkish to yellowish rock or as meter-thick sills in-between mafic layers. They emplaced early within the thermally “cool” part of the SJDD pluton directly beneath the Precambrian host rock, forming the pluton roof. Albite granites are fine-grained hololeucocratic yellowish rocks emplaced slightly after the A-type granites in the thermally mature part of the pluton. They form meter-thick sills that mingle with adjacent mafic layers and represent ca. 1 vol.% of the outcropping part of the pluton. The two granite types are similar in many respects with comparable Sr-Nd-Hf isotope compositions (87Sr/86Sr347 = 0.7071 for A-type granites vs. 0.7073 for albite granites; ?Nd347 = + 0.2 vs. + 0.3; ?Hf347zircon = + 2.47 vs. + 2.71, respectively) and SiO2 contents (74.8 vs. 74.4 wt.%). On the other hand, they have contrasting concentrations in K2O (5.30 vs. 1.97 wt.%), Na2O (2.95 vs. 4.73 wt.%) and CaO (0.48 vs. 2.04, respectively) as well as in some trace elements like Sr (59 vs. 158 ppm in average), Rb (87 vs. 35 ppm), Cr (170 vs. 35 ppm) and Ga (30 vs. 20 ppm). The isotopic composition of the A-type and albite granites is very distinct from that of the associated and volumetrically dominant mafic rocks (i.e. 87Sr/86Sr347 = 0.7042; ?Nd347 = + 5.07; ?Hf347zircon = + 8.11), excluding a direct derivation of the felsic rocks through fractional crystallization from the basaltic magma. On the other hand, small volumes of hybrid, enclave-bearing granodiorite within the SJDD lopolith suggest mixing processes within a reservoir located at deeper crustal levels. A-type granites may therefore form by magma mixing between the mafic magma and crustal melts. Alternatively, they might derive from the pure melting of an immature biotite-bearing quartz-feldspathic crustal protolith induced by early mafic injections at low crustal levels. Strong field evidences coupled to mineral chemistry and elemental geochemistry strongly support a magmatic origin for the albite granite. Sr, Nd, Hf zircon isotope data, U-Pb zircon ages, as well as data on petrography, mineral chemistry and elemental geochemistry attest that A-type and albite granites are closely related. Our preferred petrogenetic model is to consider the albite granite magma as a compositionally extreme melt that was extracted from a partially crystallized A-type granite mush at a late stage of crystallization. Alternatively, albite granites could form by melting of plagioclase-rich layers formed during A-type granite differentiation.

Barboni, Mélanie; Bussy, François

2013-09-01

357

Petrogenesis and geochronology of Cretaceous adakitic, I- and A-type granitoids in the NE Yangtze block: Constraints on the eastern subsurface boundary between the North and South China blocks  

NASA Astrophysics Data System (ADS)

The position of the subsurface boundary between the North China block (NCB) and South China block (SCB) has been debated, mainly using evidence from surface geology and geophysical observations. Here, petrochemical and geochronological data on four early Cretaceous granitic plutons from a focused area east of the Tan-Lu fault, NE Yangtze block, are reported to provide constraints on their petrogenesis and tectonic affinity. The Chuzhou intermediate intrusions consist mainly of quartz monzonite and granodiorite, and formed at ca. 125-127 Ma. They have high MgO, Al2O3, Sr, and low Rb, Y and Yb contents, together with high Sr/Y and La/Yb ratios, indicating an adakitic affinity. They also show strongly negative whole-rock ?Nd(t) and zircon ?Hf(t) (- 26 to - 16) values, and old Hf crustal model ages (2.2-2.8 Ga). Coupled with their negative Nb-Ta anomalies, high K2O/Na2O (0.91-1.18) and low Ce/Pb (1.08-5.40) ratios, these data suggest that the Chuzhou adakites were derived from thickened Archean to Paleoproterozoic lower crust. In contrast, the Fanchang, Qingyang and Huangshan intermediate-silicic complexes are dominantly composed of I-type granodiorite and quartz monzonite and A-type monzogranite and alkali feldspar granite. The I-type intrusions (126-138 Ma) were emplaced slightly earlier than the A-type intrusions (121-129 Ma), and distributed around A-type intrusions with clear intrusive boundaries. The I- and A-type rocks have lower MgO, CaO, Co, Sr, and higher Rb, Nb, Th and HREE contents than the adakitic rocks, with strong depletion in Ba, Sr, P, Eu and Ti for the A-type rocks. They have higher whole-rock ?Nd(t) (- 9 to - 5) and zircon ?Hf(t) (- 13-0) values, and younger Nd model ages (TDM2 = 1.1-1.4 Ga) and zircon Hf model ages (Tcrust = 1.2-2.0 Ga) than the adakitic rocks. These features indicate that the I- and A-type granites originated by partial melting of Mesoprotorozoic-Neoproterozoic lower crust, followed by fractional crystallization of plagioclase, K-feldspar and ferromagnesian minerals. The completely different isotopic compositions suggest that the Chuzhou adakites and three I- and A-type complexes were derived from different lower crustal domains, the former with NCB affinity and the latter with SCB affinity. Thus, a subsurface boundary between the NCB and SCB in the area east of the Tan-Lu fault can be constrained to a position between the Chuzhou and Ningwu-Fanchang area, possibly near Nanjing city. The association of Cretaceous bimodal volcanic rocks, within-plate mafic rocks and rift basins, suggests that the early Cretaceous rocks in the NE Yangtze block were produced in a lithospheric extensional setting, probably related to mantle-derived magma underplating and lithospheric thinning.

Su, Yuping; Zheng, Jianping; Griffin, William L.; Zhao, Junhong; O?Reilly, Suzanne Y.; Tang, Huayun; Ping, Xianquan; Xiong, Qing

2013-08-01

358

Geochemistry and Magmagenesis of the Early May 2008 Rhyolitic Magma Erupted by Chaiten Volcano, Southern Andes Volcanic Zone  

NASA Astrophysics Data System (ADS)

Chaiten volcano, located in the southern portion of the Southern Andes Volcanic Zone, is a 2 km diameter Holocene obsidian rhyolitic dome inside a 3 km wide caldera formed by an Upper Pleistocene basaltic to andesitic sequence. Chaiten volcano started a plinian eruption on May 1 evolving to subplinian and weak strombolian with time. Eruption has produced a significant evolution of craters geometry, volume of pyroclastic materials, gas and water emissions, large amount of fall out ash, new rhyolitic dome that is still growing, minor pyroclastic flows to the north, lateral blast to the east, and several lahars and mud flows mainly to the south along the river partially burying the Chaiten city. Six glassy, fibrous and banded, highly porous, crystal poor (zoned and twinned plagioclase, hornblende, orthopyroxene and magnetite) rhyolitic pumice and obsidian (including explosion breccias with andesitic to basaltic country rock fragments)fragments and three ash samples (also crystal poor including cristoballite, quartz, feldspars and biotite) representative of the early stage of the explosive eruption have major, trace and REE whole rock geochemical composition indicating an important crustal input in the magmagenesis (high SiO2=73-75, low Al2O3=12.75-14.80, MgO=0.1-0.6, CaO=1.4-1.9, TiO2=0.15-0.28, S=0.01-0.13, moderated K2O=2,7-3.0, Na2O=3.9-4.8 and Rb=95-121ppm, high Ba= 619-665 and Cs=5.71-7.75 and low Sr =142-161, Nb=8.00- 8.75, Y=13-14, Zr=106-121 and La/Yb=20-23 ratios, depleted HREE and HREE patterns and Eu moderate negative anomaly), as also does the previously documented <9,370 yBP rhyolitic pumice and obsidian dome, the last also showing crustal Sr, Nd and Pb isotopic signature (Lopez et al., 1993, Stern et al., 2002, Naranjo and Stern, 2004). Early May samples are depleted in MHEE and HREE and have higher La/Yb (20- 23), Rb/Ba (0.15-0.18), Ba/Sr (3.8-4.7) and Rb/Sr (0.65-0.85) ratios compare to basaltic to andesitic lavas from the Michinmahuida volcano, located 15 km to the east and to the Upper Pleistocene rhyolite from Yate volcano, approximately 100 km to the north. Geochemical data suggest that Chaiten rhyolites (both old and current eruption) were not produced by fractional crystallization of a basaltic magma derived from an astenospheric or lithospheric mantle source, as could be the case of the nearby Michinmahuida volcano. Also, Chaiten rhyolites appears to be derived from a less mafic source than the rhyolite from Yate volcano (Mella, 2008). Preliminary non-modal dynamic melting models for mafic and intermediate source suggests that 5-10 percent of partial melting of an intermediate source (modal composition including 10 Cpx, 30 Hb, 45 Pl, 4 Bt, 1 Mt) is the best fit model. As indicate by precursory and early eruption volcanotectonic seismicity, this intermediate source could be an amphibolite (facies either acquired during accretion or within the crust) located at 10-15 km depth, in a 30 km thickness crust with relatively high geothermal gradient, as it was previously proposed by Lopez et al. (1993). Crystals may be relict from the magma plumbing system. Lopez, L., Kilian, R., Kempton, P. D.., Tagiti, M. 1993. Rev. Geol.. Chile 22(1):33-55. Mella, M., 2008. Tese de Doutoramento, Universidade de Sao Paulo, 180 p. Brasil. Naranjo, J.A., Stern C., 2004. Rev. Geol. Chile 31(2): 225-240. Stern, C., Navarro, X. and Munoz, J. 2002. Anal. Inst. Patagonia 30: 167-174.

Munoz, J. O.; Basualto, D.; Moreno, H.; Peña, P.; Mella, M.

2008-12-01

359

Earth Based Views of Solute Profiles on Mars (Invited)  

NASA Astrophysics Data System (ADS)

'Historical accounts of planetary evolution are mostly written in stone' (1), but the last chapter of that history is embedded in its soil. Soil properties reflect the effects of prevailing environmental boundary conditions. Solute profiles are powerful indicators of the direction and magnitude of water flow. I briefly review the chemistry of salt profiles from deserts formed by upward vs. downward migrating water, use this as a basis for interpreting aspects of Mars hydrological history. The Noachian-aged Meridiani Planum land surface is exposed in the Endurance and Victoria Craters. These craters have been estimated to be ~ <10 My in age (2). During that time, wind erosion has sculpted the exposed walls, with possible secondary effects of moisture. The measurements by the MER Opportunity allow for an analysis of both post-excavation alteration of the craters and the pre-excavation alteration of the landscape by aqueous processes. Crater profiles include APXS 'asis' (fresh surface), brushed , and RAT'd samples. Using RAT'd samples as a baseline, the gains and losses of elements in the surficial samples can be assessed (Fig. 1). The calculations reveal similar trends of surface alteration within a crater (Victoria) and between two craters (Fig. 1). The asis samples are enriched in Na2O, Al2O3, CaO, and Br (and depleted in MgO, SO3, Cl, K2O, MnO, FeO) relative to the RAT'd material. Brushing drastically reduces these differences. These data show that the alteration is very surficial. The RAT'd samples appear to represent pre-impact chemical profiles of the sediment (Fig. 2). It has previously been reported that the upper ~1m at Victoria has been visibly altered by diagenesis (3). Both Endurance (4) and Victoria craters have remarkably similar depth profiles (relative to the lowest sampling point) of SO3, Cl, and Br. The salt profiles, combined with observations of physical alteration, suggest modest pedogenic alteration of the landsurface sometime prior to impact. The sequence of the SO3 and Cl is consistent only with downward aqueous transport, as clearly illustrated by comparison to Earth soils that form by groundwater evaporation vs. downward moving meteoric water. While the total water required to create the profiles is not easy to constrain, the meter scale depth of the alteration requires precipitation events well beyond mere surficial wetting. (1) Grotzinger et al. (2005). Earth and Planetary Science Letters 240:11-72. (2) Golombek, M.P. (2012) Timescale of small crater modification on Meridiani Planum, Mars. 43rd Lunar and Planetary Science Conference. (3) Arvidson et al. (2011). J. of Geophysical Research 116, E00F15, doi:10.1029/2010JE003746, 2011 (4) Amundson et al. (2008) Geochim. Cosmochim. Acta 72:3845-3864.

Amundson, R.

2013-12-01

360

Interaction of model F-bearing silicic melt with chloride fluid, uraninite, and columbite at 750°C and 1000-2000 bar and its implications for estimation of the ore-forming capability of the upper crustal magma chamber beneath the Strel'tsovka caldera, eastern Transbaikalia  

NASA Astrophysics Data System (ADS)

The experimental study of an F-bearing silicic melt—U, Nb, Ta minerals—chloride-fluoride fluid system is focused on ascertaining the origin of uranium deposits spatially related to intraplate silicic volcanism. The first series of experiments on uranium solubility in silicic melts close in composition to ore-bearing rhyolite of the unique Strel’tsovka Mo-U ore field has been performed in order to determine more precisely the ore genesis. As starting solid phases, model homogeneous glass of the chemical composition (wt %) 72.18 SiO2, 12.19 Al2O3, 1.02 FeO, 0.20 MgO, 0.33 CaO, 4.78 Na2O, 3.82 K2O, 1.44 Li2O, and 2.4 F (LiF, NaF, KF, CaF2, MgF2); synthetic UO2 and UO3·0.33H2O; and natural columbite were used. The starting solutions contained 1.0 m Cl and 10-2 m F. The runs were conducted in a gas vessel at a pressure of 1000 bar and in a high-pressure hydrothermal vessel at 2000 bar. The O2 (H2) fugacity was set by Ni-NiO, Co-CoO, Fe3O4-Fe2O3, and Cu-Cu2O buffers. The equilibrium between melt and solution for major elements is reached during the first day, whereas 5-7 days are required for ore elements (U, Nb, Ta) to come into equilibrium. The solubility of Nb and especially Ta in Cl-F solutions equilibrated with F-bearing melt is extremely low. The solubility of U is much higher (10-4-10-5 mol/kg H2O). The energy dispersive spectroscopy of run products allowed us to establish that columbite dissolved incongruently with formation of U- and F-bearing pyrochlores. The performed experiments have shown that a silicic melt close to the rhyolitic magma of the Strel’tsovka caldera in composition is not able to generate postmagmatic ore-forming solutions containing more than 10-6-10-5 mol U/kg H2O under the relatively low pressure necessary for the existence of the first type of fluid. The amount of uranium that could have precipitated from this fluid in the zone of ore deposition is estimated at 216-9000 t. This estimate is two orders of magnitude lower than the total uranium resources of the deposits localized in the Strel’tsovka caldera. Thus, the upper crustal silicic magma chamber hardly was a source of uranium for Mo-U deposits of the Strel’tsovka ore field.

Redkin, A. F.; Velichkin, V. I.; Aleshin, A. P.; Borodulin, G. P.

2009-08-01

361

Stability of Basalt plus Anhydrite plus Calcite at HP-HT: Implications for Venus, the Earth and Mars  

NASA Technical Reports Server (NTRS)

"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 the temperature at Venus surface. 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 might 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 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 (SiO240-45 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 approx.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.

2010-01-01

362

Differentiation of nelsonitic magmas in the formation of the ~1.74 Ga Damiao Fe-Ti-P ore deposit, North China  

NASA Astrophysics Data System (ADS)

The ~1.74 Ga Damiao anorthosite complex, North China, is composed of anorthosite and leuconorite with subordinate melanorite, mangerite, oxide-apatite gabbronorite, perthite noritic (i.e., jotunitic) and ferrodioritic dykes. The complex hosts abundant vein-, pod- and lens-like Fe-Ti-P ores containing variable amounts of apatite (10-60 modal%) and Fe-Ti oxides. In addition to Fe-Ti-P ores, there are also abundant Fe-Ti ores which are closely associated with Fe-Ti-P ores in the deposit. Most of Fe-Ti-P ores are dominated by Fe-Ti oxides and apatite, devoid of silicate minerals, mineralogically similar to the common nelsonites elsewhere. In contrast, Fe-Ti ores are dominated by Fe-Ti oxides with minor apatite (<5 modal %). The parental magma of these ores, estimated from olivine and apatite compositions using mineral-melt partition coefficients, has composition similar to the ferrodioritic dykes. Fe-Ti-P ores have variable Fe-Ti oxides and apatite proportions, indicating that they are cumulates. Their simple assemblage of Fe-Ti oxides and apatite and local net-texture suggest that the Fe-Ti-P ores in Damiao have formed from nelsonitic melts immiscibly separated from the ferrodioritic magma during late-stage differentiation. Fe-Ti ores are also cumulates and have mineral compositions similar to Fe-Ti-P ores. The close association between Fe-Ti and Fe-Ti-P ores indicates that the Fe-Ti ores may have also formed from the nelsonitic melts. We proposed that differentiation of nelsonitic melts accompanied by gravity settling is responsible for the formation of Fe-Ti and Fe-Ti-P ores. Such a differentiation process in nelsonitic melts is well supported by variations of Sr, Y, Th, U, REE and Eu/Eu* of apatite in Fe-Ti-P ores. Using oxides/apatite ratio of 2:1 and compositions of apatite and calculated primary oxides, we estimate the composition of the nelsonitic melt as ~52.0 wt% Fe2O3t, ~18.5 wt% CaO, ~14.2 wt% P2O5, ~8.7 wt% TiO2, ~4.0 wt% Al2O3 and ~1.1 wt% MgO with minor SiO2, K2O, Na2O and F. Such a nelsonitic melt is suggested to be possibly conjugated with Si-rich melts compositionally similar to the Damiao jotunitic dykes (~50 wt% SiO2 and ~15 wt% Fe2O3t) which may subsequently evolve to mangeritic rocks in Damiao. Our modeling also indicates that the onset of immiscibility occurs at a time when the evolved melt has ~44 wt% SiO2, ~21 wt% Fe2O3t, ~3.0 wt% TiO2 and ~2.6 wt% P2O5. High oxygen fugacity and phosphorous content in magmas may play important roles in the immiscibility of nelsonitic magmas, including promoting iron enrichments and widening the two-liquid field.

Chen, Wei Terry; Zhou, Mei-Fu; Zhao, Tai-Ping

2013-06-01

363

Explosive Eruption of Aphyric Rhyolitic Liquid During May 2008 from Chaitén Volcano, Chile  

NASA Astrophysics Data System (ADS)

Rhyolitic liquid erupted as Plinian fallout in May 2008 from Chaitén volcano represents a near-aphyric hydrous melt extracted and erupted rapidly from a source region deeper than at least four kilometers. We studied pumice lumps (to 18 cm) most likely erupted between May 2 and 9 but collected later from a strand line of beach near the port of Chaitén, 30 km south of the volcano. Most lumps have fibrous tube vesicles; the largest lump has a density of 0.80 g/cm3. Crystals compose less than 0.1 vol percent dense-rock equivalent. Rare phenocrysts, 0.5 to 1.0 mm in maximum diameter, are all subhedral and dominated by plagioclase, with lesser ferrohypersthene, amphibole and titanomagnetite. Backscatter imaging of grain mounts also revealed accessory apatite, zircon and pyrrhotite. No microlites were found in the matrix glass from these samples. A whole-rock analysis gives SiO2 = 75.9 wt.%, TiO2 = 0.27, Al2O3 = 13.5, FeOt = 1.30, MnO = 0.05, MgO = 0.27, CaO = 1.43, Na2O = 4.11, K2O= 3.11 and P2O5 = 0.07. Trace-element concentrations indicate that the rhyolite is not highly evolved, with moderate Rb (105 ppm) and U (3.33 ppm), and higher Sr concentrations (153 ppm) than would be typical of highly fractionated liquids. The magma chemical composition is very similar to a rhyolite dome erupted 5.6-9.4 ka at Chaitén (Naranjo and Stern, 2004; Stern et al. 2002). Electron probe analysis shows that plagioclase grains are mainly ~ An40, with rare cores as calcic as An80. Orthopyroxenes are nearly all ~ En50. Amphiboles are far more aluminous than expected for crystals forming from a shallow high-silica rhyolite magma: their Al2O3 ranges from 10.8 to 13.8 wt.%. Though the amphiboles are not euhedral, they also lack marginal reaction rinds or other evidence of breakdown due to decompression and consequent dehydration. We interpret mineral and glass compositions and textures to indicate that the magma was extracted from an intermediate-composition crystal-rich (e.g., 40-70 %) mush. The few (subhedral) phenocrysts are unlikely to have grown from the rhyolitic melt after its extraction, and instead derive from the mush zone. Published experimental phase equilibria (Costa et al., 2004) demonstrate that similar high-silica liquid can coexist with the observed phenocryst compositions in a granodioritic bulk composition with >4 % H2O in the melt at temperatures of 860 ± 20°C. The hydrous nature of the extracted rhyolitic melt likely requires that the mush had not previously reached its solidus, and thus had not lost water through plutonic consolidation and degassing. After extraction of the crystal-poor rhyolitic liquid from its source, the resident amphiboles would have started to decompose had they resided for more than a few days at depths less than ~ 4 km prior to eruption. Later erupted magmas, including the currently growing lava dome may have experienced different ascent histories. Costa, F., et al., 2004, J. Petrol., v. 45, p. 855-881.; Naranjo, J.A.and Stern, C.R. 2004. Rev. Geol. Chile v. 31, No.2, 225-240.; Stern, C.R. et al., 2002, Anal. Inst. Patagonia, v. 30, 167-174.

Lowenstern, J. B.; Sisson, T. W.; Pallister, J.; Lara, L.; Muñoz, J.

2008-12-01

364

Friedrichbeckeite, K (?0.5Na0.5)2 (Mg0.8Mn0.1Fe0.1)2 (Be0.6 Mg0.4)3 [Si12O30], a new milarite-type mineral from the Bellerberg volcano, Eifel area, Germany  

NASA Astrophysics Data System (ADS)

Friedrichbeckeite is a new milarite-type mineral. It was found in a single silicate-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, eastern Eifel volcanic area, Germany. It forms thin tabular crystals flattened on {0001}, with a maximum diameter of 0.6 mm and a maximum thickness of 0.1 mm. It is associated with quartz, tridymite, augite, sanidine, magnesiohornblende, enstatite, pyrope, fluorapatite, hematite, braunite and roedderite. Friedrichbeckeite is light yellow, with white to light cream streak and vitreous lustre. It is brittle with irregular fracture and no cleavage, Mohs hardness of 6, calculated density is 2.686 gcm-3. Optically, it is uniaxial positive with n? = 1.552(2) and n? = 1.561(2) at 589.3 nm and a distinct pleochroism from yellow (//?) to light blue (//?). Electron microprobe analyses yielded (wt.%): Na2O 2.73, K2O 4.16, BeO 4.67, MgO 11.24, MnO 2.05, FeO 1.76, Al2O3 0.15, SiO2 73.51, (? CaO, TiO2 = 0.06) sum 100.33 (BeO determined by LA-ICP-MS). The empirical formula based on Si = 12 is K0.87 Na0.86 (Mg1.57Mn0.28Fe0.24)?2.09 (Be1.83 Mg1.17)?3.00 [Si12O30], and the simplified formula can be given as K (?0.5Na0.5)2 (Mg0.8Mn0.1Fe0.1)2 (Be0.6 Mg0.4)3 [Si12O30]. Friedrichbeckeite is hexagonal, space-group P6/ mcc, with a = 9.970(1), c = 14.130(3) Å, V = 1216.4(3) Å3, and Z = 2. The strongest lines in the X-ray powder diffraction pattern are ( d in Å / I obs / hkl): 3.180 / 100 / 121, 2.885 / 70 / 114, 4.993 / 30 / 110, 4.081 / 30 / 112, 3.690 / 30 / 022. A single-crystal structure refinement ( R1 = 3.62 %) confirmed that the structure is isotypic with milarite and related [12] C [9] B 2 [6] A 2 [4] T23 [[4] T112O30] compounds. The C-site is dominated by potassium, the B-site is almost half occupied by sodium, and the A-site is dominated by Mg. The site-scattering at the T2-site can be refined to a Be/(Be + Mg) value close to 0.61; the T1-site is occupied by Si. Micro-Raman spectroscopy reveals an increasing splitting of scattering bands around 550 cm-1 for friedrichbeckeite. The mineral can be classified as an unbranched ring silicate or as a beryllo-magnesiosilicate. With respect to the end-member formula K (?0.5Na0.5)2 Mg2 Be3 [Si12O30] friedrichbeckeite represents the Mg-dominant analogue of almarudite, milarite or oftedalite. The mineral and its paragenesis were formed during pyrometamorphic modifications of the silicate-rich xenoliths enclosed in Quaternary leucite-tephritic lava of the Bellerberg volcano. Holotype material of friedrichbeckeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named friedrichbeckeite in honour of the Austrian mineralogist and petrographer Friedrich Johann Karl Becke (1855-1931).

Lengauer, C. L.; Hrauda, N.; Kolitsch, U.; Krickl, R.; Tillmanns, E.

2009-07-01

365

Pristine Rhyolite Glass Melt Inclusions in Quartz Phenocrysts From the 1.1 Ga Midcontinent Rift System, Keweenaw Peninsula, Michigan  

NASA Astrophysics Data System (ADS)

Pristine rhyolite glass from the Proterozoic eon is rarely reported in the literature. Glass-bearing melt inclusions (MI) have been identified in quartz phenocrysts from rhyolite cobbles found in rift related conglomerates within the Portage Lake Volcanics (PLV) near Calumet, Michigan. The rhyolites represent an aspect of mantle plume related bi-modal magmatism that is contemporaneous with the 1.1 Ga Midcontinent Rift System (MRS). Previous studies classified felsic rocks from the PLV into two types, one that is similar to Icelandic rhyolites (Type I) and another similar to Cenozoic topaz rhyolites (Type II). The MRS rhyolite magmas are thought to have been at high temperatures (900-1100 °C) and low water contents prior to eruption. Low-grade burial metamorphism and hydrothermal alteration has affected some rocks in the region. The MI in this study have been categorized based on their phase assemblages and preservation history. Type 1 MI contain clear glass and a shrinkage bubble, Type 2 contain clear glass, a shrinkage bubble and 1 or more, coarser grained (> 3 um) crystals, and Type 3 MI are totally devitrified or otherwise breached. The MI range in size from 1 to over 200 um in diameter and have a negative hexagonal bi-pyramidal morphology. Major element oxide compositions (75.4-SiO2, 0.09-TiO2, 11.3-Al2O3, 2.2-FeO, 0.04- MnO, 0.06-MgO, 0.84-CaO, 5.9-K2O and 2.85-Na2O in wt %) determined by EPMA for Type 1 MI are similar to whole rock compositions reported for rhyolites in the MRS. The water contents of MI are low, as evidenced by the high totals (98.67 wt %) from the EPMA and the fact that a water peak was not observed during Raman analysis (indicating that the MI contain less than 1 wt % H2O). LA-ICPMS analysis for additional trace elements (Cu, Rb, Sr, Zr, Nb, Cs, Ba, La, Ce, Eu, Yb, Ta, Th and U) were preformed on both Type 1 and Type 2 MI. Discrimination based on Ba/Rb and Ba/Th indicate that the MI are most similar to the Type II rhyolites in the region. Cathodoluminescence of quartz phenocrysts reveals several periods of resorption and new quartz growth over what we tentatively interpret as non-magmatic cores. Ti tends to increase rimward from 50-220 ppm in the magmatic growth zones corresponding to a temperature change of 675-850 °C, respectively (using the TitaniQ method with a fixed TiO2 activity equal to 1). If the TiO2 activity were lower (0.6 for example) a temperature change of 730-930 °C would be possible. Magmatic quartz crystallization temperatures may have increased by more than 175 °C from core to rim, presumably due to recharge by hotter magma sometime prior to eruption. Our results indicate that the quartz host protected the chemical integrity of the original melt that had been trapped over 1 billion years ago in select MI. Other factors including the stable tectonic history of the region and the low volatile content of the magma, may have favored the preservation of the rhyolite glass MI. The eruptive style of much of the felsic magmatism in the MRS remains an enigma in part due to a lack of exposure and few constraints on magma volatile contents and eruption temperatures. The MI described here, even those from cobbles, can be important to understanding the role of volatiles, magma chamber evolution, thermal history, and the eruptive styles related to MRS bi-modal magmatism.

Student, J. J.; Wark, D. A.; Mutchler, S. R.; Bodnar, R. J.

2006-12-01

366

Steklite, KAl(SO4)2: A finding at the Tolbachik Volcano, Kamchatka, Russia, validating its status as a mineral species and crystal structure  

NASA Astrophysics Data System (ADS)

Steklite KAl(SO4)2 has been found in sublimates of the Yadovitaya (Poisonous) fumarole at the second cinder cone of the northern breach of the Great Fissure Tolbachik Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. Steklite was approved as a valid mineral species by the Commission on New Minerals, Nomenclature, and Mineral Classification of the International Mineralogical Association on June 2, 2011 (IMA no. 2011-041). The name steklite is left for this mineral, as it was named by Chesnokov et al. (1995) for its technogenic analog from a burnt dump of coal mine no. 47 at Kopeisk, the Southern Urals, Russia. It is named after the Russian word steklo, meaning glass, in allusion to the visual similarity of its lamellae to thin glass platelets. At Tolbachik, steklite is associated with alumoklyuchevskite, langbeinite, euchlorine, fedotovite, chalcocyanite, hematite, and lyonsite. It occurs as hexagonal or irregular-shaped lamellar crystals with the major form {001} reaching 30 ?m in thickness and 0.2 mm (occasionally up to 1 mm) in width. The crystals are frequently split. They are combined into openwork aggregates or thin crusts up to 1.5 × 2.5 cm in area. Steklite is transparent and colorless, with vitreous luster. The cleavage is perfect, parallel to (001). The mineral is brittle. The Mohs' hardness is 2.5. D calc is 2.797 g/cm3. Steklite is optically uniaxial, (-), ? = 1.546(2), ? = 1.533(3). The chemical composition (wt %, electron-microprobe data) is as follows: 0.09 Na2O, 18.12 K2O, 0.08 CaO, 0.03 MnO, 2.02 Fe2O3, 18.18 Al2O3, 61.80 SO3. The total is 100.37. The empirical formula calculated on the basis of eight O atoms is: (K0.997Na0.008Ca0.004)?1.009(Al0.925Fe{0.066/3+}Mg0.003Mn0.001)?0.995S2.01O8. Steklite is trigonal, space group P321, a = 4.7281(3), c = 7.9936(5) Å, V = 154.76(17)Å3, Z =1. The strongest reflections in the X-ray powder diffraction pattern ( d, Å- I[ hkl]) are: 8.02-34[001], 4.085-11[100], 3.649-100[011, 101], 2.861-51[012, 102], 2.660 - 19[003], 2.364-25[110], 2.267-14[111, 111, 103], 1.822-12[022, 202]. In the structure of steklite examined in microtwinned crystal with R = 0.0732, the SO4 tetrahedral anions are shared-corners with distorted AlO6 trigonal prisms to form {?/2}[(Al, Fe) (SO4)2]- layers coplanar to (001). The K+ cations are in the interlayer space. The type specimen of steklite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Murashko, M. N.; Pekov, I. V.; Krivovichev, S. V.; Chernyatyeva, A. P.; Yapaskurt, V. O.; Zadov, A. E.; Zelensky, M. E.

2013-12-01

367

Fluor-ferro-leakeite, NaNa2(FC2+2Fe3+2Li)Si8O22F2, a new alkali amphibole from the Canada Pinabete pluton, Questa, New Mexico, U.S.A.  

USGS Publications Warehouse

Fluor-ferro-leakeite is a new amphibole species from the Canada Pinabete pluton, Questa, New Mexico, U.S.A.; it occurs in association with quartz, alkali feldspar, acmite, ilmenite, and zircon. It forms as anhedral bluish black crystals elongated along c and up to 1 mm long. It is brittle, H = 6, Dmeas = 3.37 g/cm3, Dcalc = 3.34 g/cm3. In plane-polarized light, it is strongly pleochroic, X = very dark indigo blue, Y = gray blue, Z = yellow green; X ??? c = 10?? (in ??obtuse), Y = b, Z ??? a = 4?? (in ?? obtuse), with absorption X > Y > Z. Fluor-ferro-leakeite is biaxial positive, ?? = 1.675(2), ??= 1.683(2), ?? = 1.694(1); 2V = 87(2)??; dispersion is not visible because of the strong absorption. Fluor-ferro-leakeite is monoclinic, space group C2/m, a = 9.792(1), b = 17.938(1), c = 5.3133(4) A??, ??= 103.87(7)??, V = 906.0(1) A??3, Z = 2. The ten strongest X-ray diffraction lines in the powder pattern are [d(I,hkl)]: 2.710(100,151), 2.536(92,202), 3.404(57,131), 4.481(54,040), 8.426(45,110), 2.985(38,241), 2.585(38,061), 3.122(29,310), 2.165(26,261), and 1.586(25,403). Analysis by a combination of electron microprobe, ion microprobe, and crystal-structure refinement (Hawthorne et al. 1993) gives SiO2 51.12, Al2O3 1.13, TiO2 0.68, Fe2O3 16.73, FeO 8.87, MgO 2.02, MnO 4.51, ZnO 0.57, CaO 0.15, Na2O 9.22, K2O 1.19, Li2O 0.99, F 2.87, H2Ocalc 0.60, sum 99.44 wt%. The formula unit, calculated on the basis of 23 O atoms, is (K0.23Na0.76)(Na1.97Ca0.03)(Mg 0.46Fe2+1.4Mn2+0.59Zn0.07Fe3+1.93-Ti 0.08Al0.02Li0.61])(Si7.81Al 0.19)O22(F1.39OH0.61). A previous crystal-structure refinement (Hawthorne et al. 1993) shows Li to be completely ordered at the M3 site. Fluor-ferro-leakeite, ideally NaNa2(Fe2+2Fe3+2Li)Si8O22F2, is related to leakeite, NaNa2(Mg2Fe3+3Li)Si 8O22(OH)2, by the substitutions Fe2+ ??? Mg and F ??? OH.

Hawthorne, F.C.; Oberti, R.; Ungaretti, L.; Ottolini, L.; Grice, J.D.; Czamanske, G.K.

1996-01-01

368

Vigrishinite, Zn2Ti4 - x Si4O14(OH,H2O,?)8, a new mineral from the Lovozero alkaline complex, Kola Peninsula, Russia  

NASA Astrophysics Data System (ADS)

A new mineral vigrishinite, epistolite-group member and first layer titanosilicate with species-defining Zn, was found at Mt. Malyi Punkaruaiv, in the Lovozero alkaline complex, Kola Peninsula, Russia. It occurs in a hydrothermally altered peralkaline pegmatite and is associated with microcline, ussingite, aegirine, analcime, gmelinite-Na, and chabazite-Ca. Vigrishinite forms rectangular or irregularly shaped lamellae up to 0.05 × 2 × 3 cm flattened on [001]. They are typically slightly split and show blocky character. The mineral is translucent to transparent and pale pink, yellowish-pinkish or colorless. The luster is vitreous. The Mohs' hardness is 2.5-3. Vigrishinite is brittle. Cleavage is {001} perfect. D meas = 3.03(2), D calc = 2.97 g/cm3. The mineral is optically biaxial (-), ? = 1.755(5), ? = 1.82(1), ? = 1.835(8), 2 V meas = 45(10)°, 2 V calc = 50°. IR spectrum is given. The chemical composition (wt %; average of 9 point analyses, H2O is determined by modified Penfield method) is as follows: 0.98 Na2O, 0.30 K2O, 0.56 CaO, 0.05 SrO, 0.44 BaO, 0.36 MgO, 2.09 MnO, 14.39 ZnO, 2.00 Fe2O3, 0.36 Al2O3, 32.29 SiO2, 29.14 TiO2, 2.08 ZrO2, 7.34 Nb2O5, 0.46 F, 9.1 H2O, -0.19 O=F2, total is 101.75. The empirical formula calculated on the basis of Si + Al = 4 is: H7.42(Zn1.30Na0.23Mn0.22Ca0.07Mg0.07K0.05Ba0.02)?1.96(Ti2.68Nb0.41Fe{0.18/3+}Zr0.12)?3.39(Si3.95Al0.05)?4 20.31F0.18. The simplified formula is: Zn2Ti4- x Si4O14(OH,H2O,?)8 ( x < 1). Vigrishinite is triclinic, space group P , a = 8.743(9), b = 8.698(9), c = 11.581(11)Å, ? = 91.54(8)°, ? = 98.29(8)°, ? = 105.65(8)°, V = 837.2(1.5) Å3, Z = 2. The strongest reflections in the X-ray powder pattern ( d, Å, - I[ hkl]) are: 11.7-67[001], 8.27-50[100], 6.94-43[01, 10], 5.73-54[11, 002], 4.17-65[020, 2, 200], and 2.861-100[30, 22, 004, 11]. The crystal structure model was obtained on a single crystal, R = 0.171. Vigrishinite and murmanite are close in the structure of the TiSiO motif, but strongly differ from each other in part of large cations and H-bearing groups. Vigrishinite is named in honor of Viktor G. Grishin (b. 1953), a Russian amateur mineralogist and mineral collector, to pay tribute to his contribution to the mineralogy of the Lovozero Complex. The type specimen is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.

Pekov, I. V.; Britvin, S. N.; Zubkova, N. V.; Chukanov, N. V.; Bryzgalov, I. A.; Lykova, I. S.; Belakovskiy, D. I.; Pushcharovsky, D. Yu.

2013-12-01

369

Günterblassite, (K,Ca)3 - x Fe[(Si,Al)13O25(OH,O)4] · 7H2O, a new mineral: the first phyllosilicate with triple tetrahedral layer  

NASA Astrophysics Data System (ADS)

A new mineral, günterblassite, has been found in the basaltic quarry at Mount Rother Kopf near Gerolstein, Rheinland-Pfalz, Germany as a constituent of the late assemblage of nepheline, leucite, augite, phlogopite, åkermanite, magnetite, perovskite, a lamprophyllite-group mineral, götzenite, chabazite-K, chabazite-Ca, phillipsite-K, and calcite. Günterblassite occurs as colorless lamellar crystals up to 0.2 × 1 × 1.5 mm in size and their clusters. The mineral is brittle, with perfect cleavage parallel to (001) and less perfect cleavage parallel to (100) and (010). The Mohs hardness is 4. The calculated and measured density is 2.17 and 2.18(1) g/cm3, respectively. The IR spectrum is given. The new mineral is optically biaxial and positive as follows: ? = 1.488(2), ? = 1.490(2), ? = 1.493(2), 2 V meas = 80(5)°. The chemical composition (electron microprobe, average of seven point analyses, H2O is determined by gas chromatography, wt %) is as follows: 0.40 Na2O, 5.18 K2O, 0.58 MgO, 3.58 CaO, 4.08 BaO, 3.06 FeO, 13.98 Al2O3, 52.94 SiO2, 15.2 H2O, and the total is 98.99. The empirical formula is Na0.15K1.24Ba0.30Ca0.72Mg0.16F{0.48/2+}[Si9.91Al3.09O25.25(OH)3.75] · 7.29H2O. The crystal structure has been determined from a single crystal, R = 0.049. Günterblassite is orthorhombic, space group Pnm21; the unit-cell dimensions are a = 6.528(1), b = 6.970(1), c = 37.216(5) Å, V = 1693.3(4) Å3, Z = 2. Günterblassite is a member of a new structural type; its structure is based on three-layer block [Si13O25(OH,O)4]. The strong reflections in the X-ray powder diffraction pattern [ d Å ( I, %) are as follows: 6.532 (100), 6.263 (67), 3.244 (49), 3.062 (91), 2.996 (66), 2.955 (63), and 2.763 (60). The mineral was named in honor of Günter Blass (born in 1943), a well-known amateur mineralogist and specialist in electron microprobe and X-ray diffraction. The type specimen of günterblassite is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.

Chukanov, N. V.; Rastsvetaeva, R. K.; Aksenov, S. M.; Pekov, I. V.; Zubkova, N. V.; Britvin, S. N.; Belakovskiy, D. I.; Schüller, W.; Ternes, B.

2012-12-01

370

Zvyaginite, NaZnNb2Ti[Si2O7]2O(OH,F)3(H2O)4 + x ( x < 1), a new mineral of the epistolite group from the Lovozero Alkaline Pluton, Kola Peninsula, Russia  

NASA Astrophysics Data System (ADS)

A new mineral, zvyaginite, a member of the epistolite group, has been found at Mt. Malyi Punkaruaiv, Lovozero Alkaline Complex, Kola Peninsula, Russia. It occurs in a hydrothermally altered peralkaline pegmatite and is associated with ussingite, microcline, aegirine, sphalerite, vigrishinite, and sauconite. Zvyaginite forms rectangular or irregular-shaped lamellae up to 0.1 × 1 × 2 cm in size when flattened [001]. The mineral is translucent to transparent and colorless, pearly-white, yellowish brownish, pale pink, or violet pink. The luster is nacreous on crystal faces and greasy on broken surfaces. Its Mohs' hardness is 2.5-3. Zvyaginite is brittle. The cleavage parallel to {001} is perfect. D meas = 2.88(3), D calc = 2.94 g/cm3. The mineral is optically biaxial (-), ? = 1.626(5), ? = 1.714(3), ? = 1.740(5), 2 V meas = 45(15)°, 2 V calc = 55°. The IR spectrum is given. Chemical composition is as follows (wt %; average of five point analyses; H2O was determined using the modified Penfield method): 4.74 Na2O, 0.22 K2O, 0.77 CaO, 1.36 MnO, 0.24 FeO, 9.61 ZnO, 0.19 Al2O3, 29.42 SiO2, 12.33 TiO2, 27.22 Nb2O5, 1.94 F, 12.65 H2O, -0.82 -O = F2, for a total of 99.87. The empirical formula calculated on the basis of Si + Al = 4 is: Na1.24K0.04Ca0.11Mn0.16Fe0.03Zn0.96Nb1.66Ti1.25(Si3.97Al0.03)?4O15.07(OH)2.10F0.83(H2O)4.64. The simplified formula is: NaZnNb2Ti[Si2O7]2O(OH,F)3(H2O)4 + x ( x < 1), Zvyaginite is triclinic, , a = 8.975(3), b = 8.979(3), c = 12.135(4) Å, ? = 74.328(9)°, ? = 80.651(8)°, ? = 73.959(8)°, V = 900.8(6) Å3, Z = 2. The strongest reflections in the X-ray powder pattern ( d, Å- I[ hkl]) are: 11.72-100[001], 5.83-40[002], 5.28-53[-1-11, 112], 4.289-86[200, 021], 3.896-36[-1-12, -201, 003, 022, 113], 2.916-57[310, 132, 004], 2.862-72[130, 312]. The model of the crystal structure was obtained on a single crystal, R = 0.159. Zvyaginite and epistolite are similar in the structure of the NbTiSiO motif, but differ from each other in composition of O layer in HOH block. Zvyaginite is named in honor of Boris B. Zvyagin (1921-2002), Russian crystallographer, crystal chemist and physicist. The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Pekov, I. V.; Lykova, I. S.; Chukanov, N. V.; Yapaskurt, V. O.; Belakovskiy, D. I.; Zolotarev, A. A.; Zubkova, N. V.

2014-12-01

371

Microtektite spherules from proximal K-Pg sections: alteration patterns and clues to precursor melt lithologies  

NASA Astrophysics Data System (ADS)

In the proximal K-Pg ejecta deposits all around the Gulf of Mexico, impact melt from the Chicxulub crater occurs predominantly in the form of glassy spherules or 'microtektites', which are considered droplets of melt that travelled ballistically from the point of impact and quenched rapidly during flight. In most localities, spherules are severely altered. Pristine, unaltered glass is very scarce and is rarely found in the center of a smectite/chlorite shell. Although the micro-tektite glass has been shown to be heterogeneous even on the ?m-scale, geochemical data have solely been reported from bulk samples. Simple binary mixing between the sedimentary carbonate and the currently described underlying crystalline basement does not fully account for the variety of tektite impact melt products, which severely complicates their interpretation. Using LA-ICP-MS, we have conducted spatially resolved analysis of trace elements in fresh, unaltered microtektite glasses and their surrounding alteration phase. This approach is unique amongst previous studies, in that it offers the opportunity to study in situ and with high spatial resolution the mixing of different target lithologies and the variation of the trace element budget during alteration. We present data from three groups of microtektite glasses at the Mimbral (NE Mexico) and Beloc (Haiti) locality: high-SiO2 green and red glasses, high-Ca yellow glass, and black glasses. All green and red glasses exhibit low oxides totals (85-90 wt%) as determined by Electron Microprobe analyses, suggesting the presence of H2O or hydrous alteration products. Raman spectroscopy clearly shows the spectrum of a hydrated glass, not an alteration phase. Their relatively high Raman index of polymerization (compared to black glass) is consistent with a normalized (water-free basis) major element composition high in SiO2 and low in network modifiers (Mg, Ca and Fe). Black and yellow glasses are not hydrated but are surrounded by a double-layered alteration rim consisting of (1) an immobile product layer depleted in SiO2, Na2O, CaO, MgO, K2O and enriched in H2O, Fe2O3, Al2O3 and TiO2. REE are depleted but still reflect the CI-normalized pattern of the precursor glass phase; (2) a palagonite/smectite phase. Most REE are below LOD and provide no clue to the composition of the precursor phase. This step-wise alteration is expressed as successive palagonite lamellae, enriched in Fe-Ti oxides that have accumulated at the alteration fronts. The type of alteration seems to be controlled by the composition of the glass. SiO2-rich green glasses (>67 wt% SiO2) seem to undergo simple hydration, whereas black SiO2 poor glasses (<65 wt% SiO2) are subjected to palagonitisation. This is consistent with the alteration mechanism postulated by Glass et al. (1997) for Cenozoic microtektites. References GLASS, B. P., MUENOW, D. W., BOHOR, B. F., & MEEKER, G. P. 1997. Fragmentation and hydration of tektites and microtektites. Meteoritics and Planetary Science, 32, 333-341.

Belza, J.; Goderis, S.; Smit, J.; Vanhaecke, F. F.; Baert, K.; Terryn, H.; Claeys, P. F.

2013-05-01

372

Voronkovite, Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH,O)4Cl · H2O, a new mineral species of the eudialyte group from the Lovozero alkaline pluton, Kola Peninsula, Russia  

NASA Astrophysics Data System (ADS)

This paper describes a new member of the eudialyte group named in honor of Alexander Alexandrovich Voronkov (1928-1982), the prominent Russian crystallographer. The new mineral has been found in the Shkatulka hyperalkaline pegmatite body at Mt. Alluaiv, Lovozero alkaline pluton, Kola Peninsula, Russia. The mineral is associated with microcline, sodalite, nepheline, aegirine, terskite, lomonosovite, vuonnemite, shkatulkalite, manganoneptunite, and sphalerite. Voronkovite occurs as rounded, poorly faced crystals up to 2-5 mm across. The new mineral is light brown, with vitreous luster and conchoidal fracture. The streak is white. Voronkovite is transparent and brittle; the Mohs hardness is 5; cleavage or parting is not observed. D(meas) = 2.97(2) g/cm3 (volumetric method); D(calc) = 2.95 g/cm3. The new mineral is uniaxial, positive, pleochroic from lemon yellow along X to brownish pink along Y, and is not luminescent in UV light. Voronkovite easily dissolves and gelates in acid at room temperature. The new mineral is trigonal, space group R3, a = 14.205(7), c = 30.265(15) Å, V = 5289(8) Å3, Z = 3. The strongest reflections in the X-ray diffraction pattern [ d, Å ( I)( hkl)] are 2.970(100)(315), 4.316(85)(205), 2.848(84)(404), 3.221(43)(208), 3.536(41)(027), 3.039(41)(119). The chemical composition (electron microprobe, H2O determined with chemical analysis) is as follows, wt %: 15.84 Na2O, 0.28 K2O, 3.08 CaO, 1.76 SrO, 4.65 MnO, 3.53 FeO, 0.93 La2O3, 1.36 Ce2O3, 0.68 Nd2O3, 0.15 Al2O3, 49.48 SiO2, 0.33 TiO2, 14.11 ZrO2, 0.23 HfO2, 0.91 Nb2O5, 0.44 Cl, 0.21 F, 1.56 H2O, 0.19 -O = (Cl,F)2; total is 99.34. The empirical formula calculated on the basis of Si + Al = 26 ( Z = 3) is as follows: (Na13.96Sr0.54K0.19)?14.69(Na1.64Ca0.92Ce0.26 La0.18)?3.00(Mn2.06Ca0.81Nd0.13)?3.00(F1.54Zr0.60Na0.48Nb0.21Ti0.13Hf0.04)?3.00Zr3.00(Si1.91Al0.09)?2.00(Si24O72)[(OH)2.98 O1.02]?4(Cl0.39F0.35)?0.74 · 1.23H2O. The simplified formula is Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH,O)4Cl · H2O. The IR spectrum of the mineral and description of its crystal structure are given. The position of voronkovite in the crystallochemical taxonomy of eudialyte group is discussed, and the relationship to other members, oneillite and raslakite, are characterized. The type material is deposited at the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Khomyakov, A. P.; Nechelyustov, G. N.; Rastsvetaeva, R. K.

2009-12-01

373

Monogenetic scoria cones, proxies of an evolutive magma chamber. Llaima volcano, Chile  

NASA Astrophysics Data System (ADS)

Stratovolcanoes are often associated with monogenetic scoria cones (MSC) around their flanks, which can show compositional variations compared to a main volcanic edifice (ME). Such variations are the representation of the state of the magma chamber at the time the MSC were formed. Using textural analysis, whole-rock and mineral chemistry, we investigate the relationship between the products of the ME and MSC at Llaima volcano, Chile; to make inferences about the plumbing system and determine the evolutionary changes of the magma chamber. Thirty MSC and their associated lava flows have been recognized, occurring on the NE, NW and SW flanks of the ME. They do not show clear stratigraphic relationships. Only three lava flows had been dated by C14, ages ranging from 3340 to 320 × 50 yr B.P1, the ages of the other cones have been inferred based in their morphologic state and degree of vegetation. Whole-rock XRF analyses show relevant compositional variations: SiO2 from 50-61 wt%, Na2O+K2O from 2.5-6 wt%, MgO from 2-6 wt% and CaO from 5-12 wt%. At the NE flank, such variations seem to be related to the distance from the ME, where the distal cones have a relatively more primitive composition. The petrography shows that plagioclase is the main mineral phase, with variable contents of olivine and clinopyroxene. At the NE, the olivine-clinopyroxene ratio varies from 3:1 to 1:10, from the closest to the farthest cones. The compositional range of plagioclase (Andesine-Bytownite) and olivine (Fo60-80) is the average, with a few cones to the NE displaying an intermediate olivine composition (Fo40-60). The pyroxene is mainly Augite, with presence of Diopside at the ME. Crystal Size Distribution (CSD) measurements of the mineral phases have also been undertaken. The CSDs of Plagioclase show linear yet slightly curved trends with similar slopes, which is typical of open magmatic systems2. For Olivine, the CSDs are generally convex, but lavas from the ME and the younger MSC display kinked patterns, representing two crystal populations usually associated with magma mingling. For the clinopyroxene, the CSDs show variation on the slope of the curves, suggesting differences in the magma residence time for each cone, where steeper slopes indicated shorter times2. This could be the case for the farther cones at the NE. Our data, from the ME and MSC are a strong indicator that the source of the melts is the magma chamber, which appears to generate more evolved products with time. This is inferred at the NE, where the oldest and most distant cones show a more primitive composition and a larger content of clinopyroxene when compared with the younger, closer cones and with historic products of the ME. In contrast, these products have a slightly more evolved composition and a larger olivine content. The CSDs of olivine and clinopyroxene of each cone give insight to the state of the magma chamber, showing evidence of magma mingling and variations in the magma residence times between eruptive events. 1. Naranjo & Moreno, (2005). Carta Geol. Chile. 88:1-65 2. Marsh, (1988b). Con. Mine and Petr. 99:277-91

Schonwalder, D. A.; Cortes, J. A.; Calder, E. S.; Ruth, D. C.

2013-12-01

374

A Initio Studies of Polarisabilities of Ions in Crystals.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. This thesis is concerned with the ab initio calculation of polarisabilities of ions in crystals. For a binary salt the Clausius-Mossotti equation relates the refractive index to the in-crystal polarisability of the ion-pair. However, there is no experimental means of separating the sum into anion and cation components. Theoretical models which use isolated ion polarisabilities to do this are physically unrealistic and have met with little success. A much better model has been developed using ab initio all-electron CHF calculations. The in-crystal environment is represented by a 'molecular' cluster embedded in a point-charge lattice. The physical features important to the success of the model are the nearest-neighbour overlap compression and the isotropic part of the electrostatic potential arising from the point -charge lattice. Calculations on simple first row alkali halides show the cation to be independent of these forces whereas the anion becomes, smaller, more bound and less polarisable in the crystal. When corrections for correlation are added the agreement with Clausius-Mossotti polarisabilities is at the 5% level or better. This implies a reduction in polarisability by factors of up to 2 with respect to the free ion. The polarisabilities for the anions in LiF, NaF, KF, LiCl, NaCl, KCl, LiBr, NaBr, KBr, CaF _2, BeO, MgO, CaO, Li_2O, Na_2O, K_2O, BeS, CaS, Li_2S, Na_2 S and K_2S were calculated. Anion polarisability is found to vary with lattice parameter but hardly at all with coordination number. Calculations on Be_2C show that in-crystal compression is sufficient to stabilise even C^{4 -}, which has a polarisability of over 20 au. Anions at the surface of LiF and MgO were also modelled. Because anisotropic overlap and electrostatic factors tend to cancel, the ion in 5-, 4- and 3-coordinate surface sites has a polarisability only a few per cent greater than in the bulk solid. Implications for active-site theories are discussed. A calculation of the geometric derivatives of the bromide polarisability in NaBr provides physical insight into models for simulating ionic melts. Calculations on NH_sp{4}{+} and CH_3NH_sp{3 }{+} show that of electronic properties of polyatomic cations also are independent of the crystal. CHF calculation of molecular polarisability was used to examine additivity of methyl-substituted alkanes, amines and ammonium cations, (CH_3)_ {x}CH_{4-x}, (CH_3)_{x} NH_{3-x} and (CH _3)_{x} NH_sp{4-x}{+} (x = 1...4). Calculations on polyatomic anions, OH^{-} and BH_sp{4}{-}, in sodium hydroxide and sodium borohydride environment show the same trends in electronic properties as those on monatomic anions.

Tole, Philip

375

Petrogenesis of Late Cretaceous I-type granites in the southern Yidun Terrane: New constraints on the Late Mesozoic tectonic evolution of the eastern Tibetan Plateau  

NASA Astrophysics Data System (ADS)

The collision between the Lhasa and Qiangtang terranes, prior to the Indo-Asian collision, is a critical aspect in terms of development of the Tibetan Plateau. It has been demonstrated that the occurrence of the Late Cretaceous granites (110-80 Ma) in the Yidun Terrane, eastern Tibetan Plateau (ETP) associates with the Lhasa-Qiangtang collision. The Xiuwacu Late Cretaceous pluton in the southern Yidun Terrane, consists three phases including biotite granitic porphyry (phase 1), monzogranite (phase 2), and alkali-feldspar leucogranite (phase 3), which have zircon U-Pb ages ranging from 85.5 Ma to 84.4 Ma. All these three phases are metaluminous or slightly peraluminous granites (A/CNK = 0.96-1.07), with high SiO2 (70.0-76.0 wt.%), K2O + Na2O (7.5-10.7 wt.%), and Ga/Al (2.5-4.7), and relatively low CaO (0.39-1.67 wt.%), MgO (0.01-0.57 wt.%), and P2O5 (0.01-0.17 wt.%). The granites are enriched in light rare earth elements (LREEs), Rb, Th, U and Ta, but depleted in heavy REEs (HREEs), Ba, Sr, P, and Ti, with significantly negative Eu anomalies (Eu/Eu* = 0.24-0.59). Comparing to classic A-type granites, these samples present higher Sr (10.1-256 ppm, mostly > 100 ppm) and lower FeO*/MgO ratios (1.2-9.9) and Zr + Nb + Ce + Y (248-483 ppm, mostly < 350 ppm). However, they show highly fractionated I-type granites affinities. All these phases have relatively high (87Sr/86Sr)i (0.7075-0.7098), negative ?Nd(t) (- 8.0 to - 6.9) and ?Hf(t) (- 7.6 to - 3.2) values, and ancient Nd and Hf model ages (1.7-1.3 Ga), which indicates similar origins predominately through partial melting of ancient mafic-intermediate lower continental crust. Besides, variable zircon ?18O values (5.9‰ to 8.4‰, partly < 6.5‰) and the occurrences of mafic microgranular enclaves (MMEs) within the granites probably indicate a contribution of mantle components. Although the Xiuwacu Late Cretaceous intrusions show higher SiO2 values and lower Sr/Y ratios comparing to other three high Sr/Y I-type intrusions (Relin, Hongshan, and Tongchanggou) in the southern Yidun Terrane, similar (87Sr/86Sr)i, ?Nd(t), ?Hf(t), and ?18O contents in all of these four intrusions point to a common source. We propose that both the Xiuwacu intrusions and the other three intrusions in the southern Yidun Terrane were generated under a late- or post-collision environment related to the Lhasa-Qiangtang collision during the Late Cretaceous. Decompression induced upwelling of mantle-derived magmas to underplate and provided heat for the anatexis of thickened lower crust. Then, those Late Cretaceous magmas were brought into the southern Yidun Terrane by mixing of lower continental crust-derived melts and minor mantle-derived magmas, and the following fractional crystallization. Occurrence of these late- or post-collision magmas probably indicates that the timing of both the Lhasa-Qiangtang collision and the eastern Tibetan Plateau uplifting was earlier than the Late Cretaceous, and that the Lhasa-Qiangtang collision did not cease at least until ca. 80 Ma. Afterwards, tectonic setting of the eastern Tibetan Plateau was progressively to be under a control mainly of the subduction of the Neo-Tethys Ocean and subsequent Indo-Asian collision.

Wang, Xin-Song; Hu, Rui-Zhong; Bi, Xian-Wu; Leng, Cheng-Biao; Pan, Li-Chuan; Zhu, Jing-Jing; Chen, You-Wei

2014-11-01

376

Mineralogy and geochemistry of the IRG Misky gold deposit, southern Peru  

NASA Astrophysics Data System (ADS)

The Misky gold deposit is one of the several Intrusion Related gold deposits that occur in the ocoña river basin, southern Peru. They are hosted in magmatic rocks from the Nazca-Palpa-Ocoña belt, from the Coastal Batholith. In this study, a petrologic and geochemical characterisation of the host rocks of the Misky deposit is presented to contribute to prove the deposit model. XRD, electron microscopy and electron microprobe analyses were used to characterize the ore and major and trace elements of host rocks were analysed by ICP-Ms. The Misky deposit, Cretaceous in age, consists mainly in quartz veins of lenticular morphology that can be more than 3 Km long and less than 1 m wide. At least two generations of magmatic host rocks are differentiated by the field relationships. The older generation is composed of plutonic rocks of the Incahuasi Unit constituted by diorites, quartz-monzonites, quartz-diorites and granodiorites in minor amounts. These rocks are crosscut by dykes of gabbro, tonalite and quartz diorite porphyries. Parallel to these dykes there is a NEE-SWW fault system. Gold veins are emplaced filling these fractures. Gabbro is rich in hornblende and present titanite reaction rims around ilmenite, which suggests relatively reduced conditions and high H2O contents. Hydrothermal alteration, associated with the gold mineralization, produced sericitization, chloritization and silicification in the surroundings of the veins. The Misky deposit has a Au-As-Pb-Zn-Cu association. Gold appears mainly in veins disseminationed in the host rocks near the contact with these veins. Gold occurs as enclosed grains within pyrite, or as electrum located in fractures of pyrite. In addition other sulphides as sphalerite, galena and chalcopyrite are abundant. Arsenopyrite, sulphosalts, bismuthinite and native bismuth also occur in lesser amounts. Calcocite, malachite and hematite are supergene minerals. The gold content can reach up to 130 pp Au and up to 0.6 wt% Cu. Major elements of the host rocks have a SiO2 content from 49.02 to 60.81 wt % and Al2O3 from 14.32 to 19.04 wt % (except one sample of 11.67 wt%. CaO can reach up to 9.34 wt%, Na2O up to 3.59 wt% and K2O up to 2.41 wt%. Geochemically these rocks are I-type calcalcaline and metaluminous. The Nb/Y and Y+Nb/Rb diagrams indicate that these host rocks are related to a volcanic arc-setting and formed in post-collision environment. Trace element patterns show LILE (K, Rb, Sr, Cs, Ba Be) and HFSE (Zr, Nb, Hf, Ta, Ti) depletion and enrichment for U, Th. Rocks from the late dykes are richer in REE. The chondrite normalised REE patterns show enrichment of the LREE and flattening of the HREE. Eu presents a positive anomaly for gabbro and diorite of the late dykes and does not show anomaly in the older rocks. Petrologic and geochemical characteristics of the host rocks of the Misky gold deposit are in accordance with the suitable setting for the intrusion gold related deposits.

Palacios, Silvia; Alfonso, Pura; Proenza, Joaquín Antonio

2014-05-01

377

Burovaite-Ca, (Na,K)4Ca2(Ti,Nb)8[Si4O12]4(OH,O)8·12H2O, a new labuntsovite-group mineral species and its place in low-temperature mineral formation in pegmatites of the Khibiny pluton, Kola Peninsula, Russia  

NASA Astrophysics Data System (ADS)

This paper presents data on burovaite-Ca, the first Ti-dominant member of the labuntsovite group with a calcium D-octahedron. The idealized formula of burovaite-Ca is (K,Na)4Ca2(Ti,Nb)8[Si4O12]4(OH,O)8 · 12H2O. The mineral has been found in the hydrothermal zone of aegirine-microcline pegmatite located in khibinite at Mt. Khibinpakhkchorr, the Khibiny pluton, Kola Peninsula, Russia. Radiaxial intergrowths of burovaite-Ca and labuntsovite-Mn associated with lemmleynite-Ba, analcime, and apophyllite have been identified in caverns within microcline. The mean composition of the mineral is as follows, wt %: 3.72 Na2O, 2.76 K2O, 4.22 CaO, 0.47 SrO, 0.23 BaO, 0.01 MnO, 0.30 Fe2O3, 0.14 Al2O3, 42.02 SiO2, 17.30 TiO2, 15.21 Nb2O5, 12.60 H2O (measured); the total is 98.98. Its empirical formula has been calculated on the basis of [(Si,Al)16O48]: {(Na3.10K1.07Ca0.37Sr0.04Ba0.04)4.62}(Ca1.28Zn0.01)1.29(Ti4.97Nb2.56Fe0.08Ta0.02)7.63(Si15.93Al0.07)16O48(OH6.70O0.93)7.63 · 12H2O. The strongest lines in the X-ray powder diffraction pattern of burovaite-Ca ( I-d Å] are as follows: 70-7.08, 40-6.39, 40-4.97, 30-3.92, 40-3.57, 100-3.25, 70-3.11, 50-2.61, 70-2.49, 40-2.15, 50-2.05, 70-1.712, 70-1.577, and 70-1.444. The structure of burovaite-Ca was solved by A.A. Zolotarev, Jr. The mineral is monoclinic, space group C2/ m. The unit-cell dimensions are a = 14.529(3), b = 14.203(3), c = 7.899(1), ? = 117.37(1)°, V = 1447.57 Å3. Burovaite-Ca is an isostructural Ti-dominant analogue of karupmøllerite-Ca and gjerdingenite-Ca. Two stages of mineral formation—pegmatite proper and hydrothermal—have been recognized in the host pegmatite. The hydrothermal stage included K-Ba-Na, Na-K-Ca, and Na-Sr substages. Burovaite-Ca is related to the intermediate Na-K-Ca substage. At the first substage, labuntsovite-Mn and lemmleynite-Ba were formed, and tsepinite-Na, paratsepinite-Nd, and tsepinite-Sr were formed at the final substage. Thus, the sequence of crystallization of labuntsovite-group minerals is characterized by the replacement of the potassium regime by the sodium regime of alkaline solutions in the evolved host pegmatite.

Azarova, Yu. V.; Shlyukova, Z. V.; Zolotarev, A. A.; Organova, N. I.

2009-12-01

378

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