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Sample records for silicate melt inclusions

  1. Volatile diffusion in silicate melts and its effects on melt inclusions

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    P. Scarlato

    2005-06-01

    Full Text Available A compendium of diffusion measurements and their Arrhenius equations for water, carbon dioxide, sulfur, fluorine, and chlorine in silicate melts similar in composition to natural igneous rocks is presented. Water diffusion in silicic melts is well studied and understood, however little data exists for melts of intermediate to basic compositions. The data demonstrate that both the water concentration and the anhydrous melt composition affect the diffusion coefficient of water. Carbon dioxide diffusion appears only weakly dependent, at most, on the volatilefree melt composition and no effect of carbon dioxide concentration has been observed, although few experiments have been performed. Based upon one study, the addition of water to rhyolitic melts increases carbon dioxide diffusion by orders of magnitude to values similar to that of 6 wt% water. Sulfur diffusion in intermediate to silicic melts depends upon the anhydrous melt composition and the water concentration. In water-bearing silicic melts sulfur diffuses 2 to 3 orders of magnitude slower than water. Chlorine diffusion is affected by both water concentration and anhydrous melt composition; its values are typically between those of water and sulfur. Information on fluorine diffusion is rare, but the volatile-free melt composition exerts a strong control on its diffusion. At the present time the diffusion of water, carbon dioxide, sulfur and chlorine can be estimated in silicic melts at magmatic temperatures. The diffusion of water and carbon dioxide in basic to intermediate melts is only known at a limited set of temperatures and compositions. The diffusion data for rhyolitic melts at 800°C together with a standard model for the enrichment of incompatible elements in front of growing crystals demonstrate that rapid crystal growth, greater than 10-10 ms-1, can significantly increase the volatile concentrations at the crystal-melt interface and that any of that melt trapped

  2. Understanding Vesuvius magmatic processes: Evidence from primitive silicate-melt inclusions in medieval scoria clinopyroxenes (Terzigno formation)

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    Lima, A.; Belkin, H.E.; Torok, K.

    1999-01-01

    Microthermometric investigations of silicate-melt inclusions and electron microprobe analyses were conducted on experimentally homogenized silicate-melt inclusions and on the host clinopyroxenes from 4 scoria samples of different layers from the Mt. Somma-Vesuvius medieval eruption (Formazione di Terzigno, 893 A.D.). The temperature of homogenization, considered the minimum trapping temperature, ranges from 1190 to 1260??5 ??C for all clinopyroxene-hosted silicate melt inclusions. The major and minor-element compositional trends shown by Terzigno scoria and matrix glass chemical analysis are largely compatible with fractional crystallization of clinopyroxene and Fe-Ti oxides. Sulfur contents of the homogenized silicate-melt inclusions in clinopyroxene phenocrysts compared with that in the host scoria show that S has been significantly degassed in the erupted products; whereas, Cl has about the same abundance in the inclusions and in host scoria. Fluorine is low (infrequently up to 800 ppm) in the silicate-melt inclusions compared to 2400 ppm in the bulk scoria. Electron microprobe analyses of silicate-melt inclusions show that they have primitive magma compositions (Mg# = 75-91). The composition of the host clinopyroxene phenocrysts varies from typical plinian-related (Mg#???85) to non-plinian related (Mg#???85). The mixed source of the host clinopyroxenes and primitive nature of the silicate-melt inclusions implies that these phenocrysts, in part, may be residual and/or have a polygenetic origin. The similar variation trends of major and minor-elements between homogenized silicate-melt inclusions from the Terzigno scoria, and silicate-melt inclusions in olivine and diopside phenocrysts from plinian eruptions (Marianelli et al., 1995) suggest that the trapped inclusions represent melts similar to those that supplied the plinian and sub-plinian magma chambers. These geochemical characteristics suggest that the Vesuvius magmatic system retained a vestige of the most

  3. The stability of hibonite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions

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    Beckett, J. R.; Stolper, E.

    1993-01-01

    Phase fields in which hibonite (Hib) and silicate melt coexist with spinel (Sp), CaAl4O7 (CA2), gehlenitic melilite (Mel), anorthite (An), or corundum (Cor) in the system CaO-MgO-Al203-SiO2-TiO2 (CMAST) were determined and activity models developed for Mel and Hib solid solutions. Experimentally determined partition coefficients for Ti between Hib and coexisting melt, D sub t, vary from 0.8 to 2.1 and generally decrease with increasing TiO2 content in the liquid (L). Based on Ti partioning between Hib and melt, bulk inclusion compositions and Hib-saturated liquid use phase diagrams, the Hib in Fluffy Type A inclusions (FTA's) from Allende and at least some of the Hib from Hib-rich inclusions is relict; much of the Hib from Hib-glass spherules probably crystallized from a melt under nonequilibrium conditions. Bulk compositions for all of these Ca-Al-rich inclusions (CAI's) are consistent with an origin as Mel + Hib + Sp + perovskite (Pv) proto-inclusions in which Mel was partially altered. In some cases, the proto-inclusion was partially or completely melted with vaporization occurring over a period of time sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. If equilibration temperatures based on Hib-bearing CAI's reflect condensation in a cooling gas of solar composition, then Hib + Cor condensed at approximately 1260 C (referenced to 10 exp -3 atm) and Hib + Sp + Mel at approximately 1215 +/- 10 C. Simple thermochemical models for the substitution of trace elements into the Ca-site of meteoritic Hib suggest that virtually all Eu is divalent in early condensate Hibs but that Eu(2+)/Eu(3+) decreases by a factor of 20 or more during the course of condensation, primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phases condense. The relative sizes of Eu and Yb anomalies in meteoritic Hibs and CAI's may be influenced by

  4. Degassing-induced crystallization in silicate melt inclusion: evaluating the role of post-entrapment changes in melt inclusion from the SW volcanic flows of Deccan Large Igneous Province (Deccan LIP) lava.

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    Rani Choudhary, Babita

    2017-04-01

    Melt inclusions represent sampling of magma during their growth in magma chambers and during ascent to the surface. Several studies of melt inclusions in Large Igneous Provinces (LIPs) in different parts of the world have been documented in the literature (Sobolev et al. 2011; Kamenetsky et al. 2012). Melt inclusions study from Deccan LIP can provide new insights into the physio-chemical conditions and evolution of this important LIP. The Deccan LIP was fissure eruption mainly emplaced over a very short duration at 66 Ma (Schoene et al. 2015). To better characterize and explain the diversity in geochemical composition, petrogenesis and volatile degassing, melt inclusions studies have been carried out in clinopyroxene and plagioclase feldspar from a suite of samples in the Western Ghats section. Samples were obtained from the upper three formations (the Wai subgroup). The inclusions are primary and range in shape and size varies from a few microns, up to 100 microns. The inclusions are crystalline, and contain daughter phases. Some are glassy, with or without a shrinkage bubble. The melt inclusions show substantial variations in major element composition. Inclusions are significantly enriched in TiO2 (3.68 to 0.08 wt%) and FeO (18.3 to 2.63 wt%). SiO2 ranges from 43.4-66.8 wt% and classification diagrams of total alkali (Na2O+K2O) Vs. silica melt inclusions show that most inclusions are of sub-alkaline to mildly alkaline composition. Al2O3 ranges from 9.7- 22.4wt % and MgO 18.3-1.6. EPMA measurements demonstrated the presence of daughter crystals, such as magnetite and titanomagnetite, and high FeO, TiO2 and CaO within melt inclusions among the silicate daughter crystal clusters. Volatiles are determined have wide range in composition in both plagioclase- and pyroxene-hosted melt inclusions by using FTIR technique, values up to 2wt% H2Ototal and 1808 ppm CO2. Moreover the variability in composition and volatiles the melt from the samples in a single flow suggests

  5. The formation of the Yichun Ta-Nb deposit, South China, through fractional crystallization of magma indicated by fluid and silicate melt inclusions

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    Li, Shenghu; Li, Jiankang; Chou, I.-Ming; Jiang, Lei; Ding, Xin

    2017-04-01

    The Yichun Ta-Nb deposit, which is located in Jiangxi Province, South China, can be divided into four lithological zones (from bottom upward): two-mica granite, muscovite granite, albite granite, and lepidolite-albite granite zones. It remains controversial whether these distinct vertical zones were formed through late magmatic-hydrothermal metasomatic alteration or fractional crystallization of magma. To investigate the evolution mechanism of rock- and ore-forming fluid in this deposit, we studied fluid and melt inclusions in quartz and lepidolite in these four granite zones. These fluid inclusions are mainly composed of H2O-NaCl, and have homogenization temperatures ranging from 160 °C to 240 °C, with densities between 0.86 and 0.94 g/cm3 and salinities between 0.5 and 6.5 wt% NaCl equivalent. Raman spectroscopic analyses showed that the daughter minerals contained in silicate melt inclusions are mainly quartz, lepidolite, albite, muscovite, microcline, topaz, and sassolite. From the lower to upper granite zones, the albite contents in silicate melt inclusions increase, while the muscovite contents decrease gradually until muscovite is substituted by lepidolite in the lepidolite-albite granite zone. Additionally, the calculated densities of the silicate melt inclusions exhibit decreasing trends from bottom upward. The total homogenization temperatures of silicate melt inclusions, which were observed under external pressures created in the sample chamber of a hydrothermal diamond-anvil cell, decreased from 860 °C in the lower lithological zone to 776 °C in the upper lithological zone, and the initial melting temperatures of solid phases were 570-710 °C. The calculated initial H2O contents of granitic magma showed an increasing trend from the lower (∼2 wt% in the two-mica granite zone) to the upper granitic zones (∼3 wt% in the albite granite zone). All of these features illustrate that the vertical granite zones in the Yichun Ta-Nb deposit formed through

  6. Melt inclusions as a 'window' through the crust: What drives the most productive region of silicic volcanism on Earth?

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    Barker, S. J.; Rowe, M. C.; Baker, J. A.; Kenworthy, C.; Wilson, C. J. N.; Wysoczanski, R. J.; Rooyakkers, S. M.

    2016-12-01

    The Taupo Volcanic Zone (TVZ) is globally unique in the intensity of its magmatic-volcanic-geothermal flux. However, the causes of this anomaly are not yet understood, as primary magmas (basalts) are extensively modified in the TVZ during their ascent to the surface, overprinting the geochemical features required to infer conditions under which they formed. Moreover, the small amounts of basalt that do erupt are likely buried or destroyed by explosive and voluminous rhyolitic (super)eruptions. Our novel study addresses this issue by applying forensic geochemical techniques to glassy melt inclusions trapped within olivine crystals, separated from volcanic rocks throughout the TVZ, ranging in age from 0 to 350 ka. Our approach is motivated by the recent identification of high-Mg olivine xenocrysts inherited from primitive basalts in large-volume TVZ rhyolites, which contain trapped basaltic melt inclusions with the most primitive magma compositions ever recorded in the TVZ. These inclusions provide a novel and unique "window" into mantle processes driving voluminous rhyolitic volcanism. Here we present major and trace element data from olivine melt inclusions from across and along the arc and, for the first time, quantify the spatial and temporal compositional variability of magmas feeding the TVZ. Our data reveals the unique subduction and rifting processes behind the extreme, globally unique heat flow and eruptive rate of this end member continental arc.

  7. The stability of hibonite, melilite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions from carbonaceous chondrites

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    Beckett, J. R.; Stolper, E.

    1994-01-01

    Phase fields in which hibonite and silicate melt coexist with spinel CaAl4O7, gehlenitic melilite, anorthite or corundum at 1 bar in the system CaO-MgO-Al2O3-SiO2-TiO2 were determined. The hibonites contain up to 1.7 wt% SiO2. For TiO2, the experimentally determined partition coefficients between hibonite and coexisting melt D(sub i)(sup Hib/L), vary from 0.8 to 2.1 and generally decrease with increasing TiO2 in the liquid. Based on Ti partitioning between hibonite and melt, bulk inclusion compositions and hibonite-saturated liquidus phase diagrams, the hibonite in hibonite-poor fluffy Type A inclusions from Allende and at least some hibonite from hibonite-rich inclusions is relict, although much of the hibonite from hibonite-glass spherules probably crystallized metasably from a melt. Bulk compositions for all of these CAIs are consistent with an origin as melite + hibonite + spinel + perovskite phase assembalges that were partially altered and in some cases partially or completely melted. The duration of the melting event was sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. Simple thermochemical models developed for meteoritic melilite and hibonite solid solutions were used to obtain equilibration temperatures of hibonite-bearing phase assemblages with vapor. Referenced to 10(exp -3) atm, hibonite + corundum + vapor equilibrated at approximately 1260 C and hibonite + spinel +/- melilite + vapor at 1215 +/- 10 C. If these temperatures reflect condensation in a cooling gas of solar composition, then hibonite +/- corundum condensed first, followed by spinel and then melilite. The position of perovskite within this sequence is uncertain, but it probably began to condense before spinel. This sequence of phase appearances and relative temperatures is generally consistent with observed textures but differs from expectations based on classical condensation calculations in that

  8. New approach on volatile contents determination in silicate melt inclusions: A coupling X-ray microtomography and geochemical approach in Los Humeros caldera complex (Eastern Mexican Volcanic Belt)

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    Creon, L.; Levresse, G.; Carrasco Nuñez, G.

    2016-12-01

    Volatile contents and magma degassing behavior are known to affect the style, frequency, and intensity of near-surface magmatic processes. For this reason, much effort have been devoted to characterize the volatile evolution of shallow magmatic systems to better constrain volcanic history. Silicate melt inclusions (SMI) represent samples of melt that were isolated from the bulk magma at depth, thus preserving the PTX conditions of the pre-eruptive material. SMI are often affected by the formation of a bubble after trapping; this is a natural consequence of the PVTX properties of crystal-melt-volatile systems. Previous workers have recognized that bubble formation is an obstacle, which affects the interpretation of SMI trapping conditions based only on analysis of the glass phase. Indeed, they explained that bubbles can contain a significant percentage of the volatiles, particularly for those with low solubility in the melt (e.g. CO2). In this study, we propose to define the pre-eruptive PTX conditions of Los Humeros magma chamber using SMI from the various eruption events within 460 and 30 Ka. An innovative analytical coupling has been used in order to determine: (1) the volume of the SMI glass and bubble, using high resolution 3D X-ray microtomography; (2) the density and composition of the bubbles, using Raman spectroscopy; (3) the volatile element contents in glass, using NanoSIMS; and, (4) the major elements composition of the glass, using EPMA. The recalculated volatile concentrations of the total SMI (glass + bubble), illustrate clearly that the volatile content determinations using only the glass phase, underestimate drastically the total volatile content and therefore induce significant error on the determination of the pre-eruptive volcanic budget and on the constrain on the volcanic and thermal history. This study had moreover highlighted the complex evolution of Los Humeros composite magma chamber and, gave constrains for geothermal exploration purpose.

  9. Silicic magma accumulation beneath Mount Mazama, Oregon, 71 ka to 24 ka constrained by SHRIMP measurements of dissolved volatile concentrations in melt inclusions

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    Wright, H. M.; Bacon, C. R.; Vazquez, J. A.; Sisson, T. W.

    2010-12-01

    Dissolved volatile contents of melt inclusions trapped in pyroxene and plagioclase crystals from 7 silicic eruptions preceding the climactic ~7.7 ka Mazama eruption were measured by SIMS with the Stanford-USGS SHRIMP-RG. Melt inclusions in crystals were intersected, polished, and crystals were mounted in indium in Al mounts. A 1.2-3.0 nA (depending on the session), O2- primary beam was accelerated and focused to a 15-25 μm spot on the sample surface, which generated positive secondary ions of analyzed Li, Be, B, C, OH, F, Mg, Si, SiH, S, Cl, Ca, AlO, KO, Rb, and Sr. Measurements were made at high mass resolution (6000-7000). Trace element and volatile concentrations were calculated using a best-fit regression to count rate ratios (normalized to 30Si) vs. variable known concentrations in experimental and natural rhyolite glass standards. Pumiceous samples were chosen from dacitic to rhyodacitic eruptive deposits, consisting of the 71ka dacite of Pumice Castle, 70ka dacite below Llao Rock, 50ka dacite of the Watchman, 35ka dacite of Munson Valley, 35ka Williams Crater tephra, 27ka Redcloud Cliff rhyodacite, and 24ka andesite S of Bear Bluff. Melt inclusions are abundant in spongy, mineral-inclusion-rich interiors of pyroxene crystals in early (71-35ka) eruptive deposits and are less abundant throughout pyroxenes from later eruptions (35-24ka) and in plagioclase crystals. Over the entire time interval, most trace element and volatile concentrations remain approximately constant between melt inclusion populations. However, there are some variations in water and carbon dioxide concentration. A large proportion of inclusions in the smaller eruptive deposits (0.003-0.4 km3) of the dacite of the Watchman, dacite of Munson Valley, and Williams Crater tephra have low water contents, ~1 wt% H2O, corresponding to a saturation pressure of 25MPa, or ~1km depth (at 870°, approximate average temperature for these deposits, e.g., Druitt and Bacon, Contrib Mineral Petrol 1989

  10. Bursting the bubble of melt inclusions

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    Lowenstern, Jacob B.

    2015-01-01

    Most silicate melt inclusions (MI) contain bubbles, whose significance has been alternately calculated, pondered, and ignored, but rarely if ever directly explored. Moore et al. (2015) analyze the bubbles, as well as their host glasses, and conclude that they often hold the preponderance of CO2 in the MI. Their findings entreat future researchers to account for the presence of bubbles in MI when calculating volatile budgets, saturation pressures, and eruptive flux.

  11. Lithium diffusion in silicate melts

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    Cunningham, G. J.; Henderson, P.; Lowry, R. K.; Nolan, J.; Reed, S. J. B.; Long, J. V. P.

    1983-10-01

    The diffusion properties of Li in an andesitic and pitchstone melt have been determined over the temperature range 1300-1400°C. The diffusion data have been fitted to an Arrhenius relationship between log D0 and 1/ T, and give relatively small activation energies of diffusion: 21.4±5.8 kcal mol -1 in the andesite and 20.1±2.8 kcal mol -1 in the pitchstone. Li +, unlike several other cations, shows similar diffusivities in these melt compositions to that in a basaltic melt. Despite the similar ionic radius of Li + to that of Co 2+, the diffusion properties of the two ions are very different from each other.

  12. The infidelity of melt inclusions?

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    Kent, A. J.

    2008-12-01

    Melt inclusions provide important information about magmatic systems and represent unique records of magma composition and evolution. However, it is also clear that melt inclusions do not necessarily constitute a petrological 'magic bullet', and potential exists for trapped melt compositions to be modified by a range of inclusion-specific processes. These include trapping of diffusional boundary layers, crystallization of the host mineral after trapping and dissolution of co-trapped minerals during homogenization, diffusional exchange between trapped liquid and the host mineral and external melt, and cryptic alteration of trapped material during weathering or hydrothermal alteration. It clearly important to identify when melt inclusions are unmodified, and which compositional indices represent the most robust sources of petrogenetic information. In this presentation I review and discuss various approaches for evaluating compositions and compositional variations in inclusion suites. An overriding principle is that the variations evident in melt inclusions should be able to be understood in terms of petrological processes that are known, or can be reasonably inferred to also effect bulk magma compositions. One common approach is to base petrological conclusions on species that should be more robust, and many workers use variations in incompatible trace elements for this purpose. However important information may also be obtained from a comparison of variations in melt inclusions and the lavas that host them, and in most cases this comparison is the key to identifying inclusions and suites that are potentially suspect. Comparisons can be made between individual inclusions and lavas, although comparison of average inclusion composition and the host lava, after correction for differences in crystal fractionation, may also be valuable. An important extension of this is the comparison of the variability of different species in inclusions and host lavas. This also provides

  13. Initiation of large-volume silicic centers in the Yellowstone hotspot track: insights from H2O- and F-rich quartz-hosted rhyolitic melt inclusions in the Arbon Valley Tuff of the Snake River Plain

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    Drew, Dana L.; Bindeman, Ilya N.; Loewen, Matthew W.; Wallace, Paul J.

    2016-01-01

    During the onset of caldera cluster volcanism at a new location in the Snake River Plain (SRP), there is an increase in basalt fluxing into the crust and diverse silicic volcanic products are generated. The SRP contains abundant and compositionally diverse hot, dry, and often low-δ18O silicic volcanic rocks produced through time during the formation of individual caldera clusters, but more H2O-rich eruptive products are rare. We report analyses of quartz-hosted melt inclusions from pumice clasts from the upper and lower Arbon Valley Tuff (AVT) to gain insight into the initiation of caldera cluster volcanism. The AVT, a voluminous, caldera-forming rhyolite, represents the commencement of volcanism (10.44 Ma) at the Picabo volcanic field of the Yellowstone hotspot track. This is a normal δ18O rhyolite consisting of early and late erupted members (lower and upper AVT, respectively) with extremely radiogenic Sr isotopes and unradiogenic Nd isotopes, requiring that ~50 % of the mass of these elements is derived from melts of Archean upper crust. Our data reveal distinctive features of the early erupted lower AVT melt including: variable F concentrations up to 1.4 wt%, homogenous and low Cl concentrations (~0.08 wt%), H2O contents ranging from 2.3 to 6.4 wt%, CO2 contents ranging from 79 to 410 ppm, and enrichment of incompatible elements compared to the late erupted AVT, subsequent Picabo rhyolites, SRP rhyolites, and melt inclusions from other metaluminous rhyolites (e.g., Bishop Tuff, Mesa Falls Tuff). We couple melt inclusion data with Ti measurements and cathodoluminescence (CL) imaging of the host quartz phenocrysts to elucidate the petrogenetic evolution of the AVT rhyolitic magma. We observe complex and multistage CL zoning patterns, the most critical being multiple truncations indicative of several dissolution-reprecipitation episodes with bright CL cores (higher Ti) and occasional bright CL rims (higher Ti). We interpret the high H2O, F, F/Cl, and

  14. Kinetics of iron oxidation in silicate melts

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    Magnien, V.; Neuville, D.R.; Cormier, L.; Mysen, B.O.; Pinet, O.; Richet, P

    2004-07-01

    High-temperature XANES experiments at the Fe K-edge have been used to study the kinetics of iron oxidation in a supercooled melt of Fe-bearing pyroxene composition. These experiments, made just above the glass transition between 600 and 700 deg C, show that variations in relative abundances of ferric and ferrous iron can be determined in situ at such temperatures. The kinetics of iron oxidation do not vary much with temperature down to the glass transition. This suggests that rate-limiting factor in this process is not oxygen diffusion, which is coupled to relaxation of the silicate network, but diffusion of network modifying cations along with a counter flux of electrons. To give a firmer basis to redox determinations made from XANES spectroscopy, the redox state of a series of a samples was first determined from wet chemical, Moessbauer spectroscopy and electron microprobe analyses. (authors)

  15. Sulfide and silicate melt inclusions in the D. João de Castro Volcanic Seamount, a hydrothermally active area on the Terceira Rift, Azores

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    Marques, A. F. A.; Scott, S. D.; Madureira, P.; Rosa, C. J. P.; Lourenço, N.; Conceição, P.; TerRiftic Team

    2012-04-01

    The Azores plateau is a bathymetric high located in the North Atlantic encompassing a triple junction where the American, Eurasia and African plates meet. The Terceira Rift (TR), within the plateau, defines the Eurasia/African plate boundary and corresponds to a 550 Km long, ESE trending line of volcanic islands and seamounts (e.g. D. João de Castro - DJC) alternating with deep basins (e.g. Hirondelle - HIR) [1, 2]. Fresh basalts from the TR, in particular the DJC and HIR areas, were sampled from 2007 to 2009 [EMEPC 2007/2008/2009 cruises]. The team is now studying their melt inclusions [MI] in order to understand processes of magma evolution and mixing as well as the behavior of trace metals and volatiles in the pre-erupted magmas. Petrographic observations indicate that in DJC and HIR, basalts are porphyritic, vesicular, with a microcrystalline groundmass composed mostly of plagioclase laths ± olivine ± clinopyroxene ± skeletal Fe-Ti oxides ± glass. Phenocrysts are subhedral to euhedral with corroded rims. Clinopyroxene (aluminian diopside) is the main phenocryst phase, followed by olivine (Fo83 - DJC; Fo80 - HIR) and minor plagioclase (often as microphenocrysts). Incompatible trace elements in groundmass, glass, and exposed MI in clinopyroxene depict enriched patterns above the OIB field. REE patterns are similar in the groundmass and glass from DJC and HIR. Exposed MI from HIR depicts less enriched REE patterns than the groundmass, whilst DJC MI show similar REE patterns to the groundmass. MI were found in most mineral phases studied. They are distributed randomly (azonal) and appear glassy, partially devitrified or completely opaque with one or more vapor bubbles. Glassy to devitrified MI may show interpenetrating arrays of mineral phases, skeletal Fe-Ti oxides, and included euhedral Cr-spinel. Sulfide globules are common in clinopyroxene-hosted MI and are dispersed within the groundmass. Globules are small, less than 10 μm, and contain distinct mineral

  16. Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

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    Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing

    2017-12-01

    The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.

  17. Silicate melt inclusion evidence for extreme pre-eruptive enrichment and post-eruptive depletion of lithium in silicic volcanic rocks of the western United States: implications for the origin of lithium-rich brines

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    Hofstra, Albert H.; Todorov, T.I.; Mercer, C.N.; Adams, D.T.; Marsh, E.E.

    2013-01-01

    To evaluate whether anatectic and/or highly fractionated lithophile element-enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption, lithification, and weathering to generate significant Li brine resources, pre-eruptive melt compositions, preserved in inclusions, and the magnitude of post-eruptive Li depletions, evident in host rhyolites, were documented at six sites in the western United States. Each rhyolite is a member of the bimodal basalt-rhyolite assemblage associated with extensional tectonics that produced the Basin and Range province and Rio Grande rift, an evolving pattern of closed drainage basins, and geothermal energy or mineral resources. Results from the 0.8 Ma Bishop tuff (geothermal) in California, 1.3 to 1.6 Ma Cerro Toledo and Upper Bandelier tephra (geothermal) and 27.9 Ma Taylor Creek rhyolite (Sn) in New Mexico, 21.7 Ma Spor Mountain tuff (Be, U, F) and 24.6 Ma Pine Grove tuff (Mo) in Utah, and 27.6 Ma Hideaway Park tuff (Mo) in Colorado support the following conclusions. Melt inclusions in quartz phenocrysts from rhyolite tuffs associated with hydrothermal deposits of Sn, Mo, and Be are extremely enriched in Li (1,000s of ppm); those from Spor Mountain have the highest Li abundance yet recorded (max 5,200 ppm, median 3,750 ppm). Forty-five to 98% of the Li present in pre-eruptive magma was lost to the environment from these rhyolite tuffs. The amount of Li lost from the small volumes (1–10 km3) of Li-enriched rhyolite deposited in closed basins is sufficient to produce world-class Li brine resources. After each eruption, meteoric water leaches Li from tuff, which drains into playas, where it is concentrated by evaporation. The localized occurrence of Li-enriched rhyolites may explain why brines in arid lacustrine basins seldom have economic concentrations of Li. Considering that hydrothermal deposits of Sn, Mo, Be, U, and F may indicate potential for Li brines in nearby basins, we surmise that the

  18. The evolution of immiscible silicate and fluoride melts: Implications for REE ore-genesis

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    Vasyukova, O.; Williams-Jones, A. E.

    2016-01-01

    The Mid-Proterozoic peralkaline Strange Lake pluton (Québec-Labrador, Canada) exhibits extreme enrichment in high field strength elements (HFSE), including the rare earth elements (REE), particularly in pegmatites. On the basis of a study of melt inclusions, we proposed recently that fluoride-silicate melt immiscibility played an important and perhaps dominant role in concentrating the REE within the pluton. Here we present further evidence for silicate-fluoride immiscibility at Strange Lake from a sample of the hypersolvus granite, which contains an inclusion composed largely of REE and HFSE minerals. The inclusion (∼5 cm in diameter) comprises a narrow rim containing chevkinite-(Ce) and zircon in a fluorite matrix, a core of fluorbritholite-(Ce) and bastnäsite-(Ce) and a transition zone between the rim and the core consisting of a fine-grained intergrowth of bastnäsite-(Ce), gagarinite-(Y) and fluorite. We propose that the inclusion formed as a result of silicate-fluoride immiscibility, which occurred early in the emplacement history of the Strange Lake pluton, and that it represents the fluoride melt. After separation of the two melts, the boundary between them acted as a locus of crystallisation, where crystals formed repeatedly due to heterogeneous (surface catalysed) nucleation. Zircon crystallised shortly after melt phase separation, and was followed by the growth of perthite together with arfvedsonite and quartz. As a result, the silicate melt surrounding the fluoride inclusion became enriched in volatiles that facilitated crystallisation of progressively larger crystals in the inclusion; large crystals of arfvedsonite and perthite were succeeded by even larger crystals of quartz. Massive crystallisation of chevkinite-(Ce) followed, forming the rim of the inclusion. The fluoride melt, which constituted the matrix to the silicate minerals and chevkinite-(Ce), crystallised after chevkinite-(Ce), forming fluorbritholite-(Ce) and fluorite. Aqueous fluid

  19. Modeling the viscosity of silicate melts containing manganese oxide

    Directory of Open Access Journals (Sweden)

    Kim Wan-Yi

    2013-01-01

    Full Text Available Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.

  20. Coordination of Actinides in Silicate Melts

    OpenAIRE

    F. Farges; Brown, G; Wu, Z.

    1997-01-01

    The structural environments around Th(IV) and U(VI) at concentrations ranging from 90 ppm to 7 wt.% were investigated in glasses and melts of Na di- and trisilicate compositions between 293 and 1550 K using x-ray absorption fine structure (XAFS) spectroscopy. Data for model compounds were collected at temperatures up to 2000 K in order to quantify the magnitude of anharmonic effects. Data for glasses and melts were collected and analyzed considering anharmonic (cumulant-expansion), curved-wav...

  1. Activity composition relationships in silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Glazner, A.F.

    1990-01-01

    Equipment progress include furnace construction and electron microprobe installation. The following studies are underway: phase equilibria along basalt-rhyolite mixing line (olivine crystallization from natural silicic andensites, distribution of Fe and Mg between olivine and liquid, dist. of Ca and Na between plagioclase and liquid), enthalpy-composition relations in magmas (bulk heat capacity of alkali basalt), density model for magma ascent and contamination, thermobarometry in igneous systems (olivine/plagioclase phenocryst growth in Quat. basalt), high-pressure phase equilibria of alkali basalt, basalt-quartz mixing experiments, phase equilibria of East African basalts, and granitic minerals in mafic magma. (DLC)

  2. Experimental calibration of a new oxybarometer for silicic magmas based on the partitioning of vanadium between magnetite and silicate melt

    Science.gov (United States)

    Arató, Róbert; Audétat, Andreas

    2016-04-01

    Oxygen fugacity is an important parameter in magmatic systems that affects the stability of mineral phases and fluid species. However, there is no well-established method to reconstruct the oxygen fugacity of slowly cooled magmas such as granite, for example, because existing oxybarometers (e.g., magnetite-ilmenite method) are susceptible to re-equilibration processes during slow cooling and thus lead to erroneous results when applied for granitic rocks. In this study, we aim at developing an oxybarometer that is based on the partitioning of vanadium (a redox-sensitive element) between magnetite inclusions and silicate melt inclusions preserved in quartz phenocrysts, where they were protected from subsolidus alteration and can be measured as entities by LA-ICP-MS. In the first - experimental - part of this study we investigated the effects of temperature (800-950 ° C), pressure (1-2 kbar), oxygen fugacity (from ΔFMQ+0.7 to ΔFMQ+4.0), magnetite composition, and melt composition on the partition coefficient of vanadium between magnetite and melt (DVmgt-melt). The experiments were carried out in cold-seal pressure vessels and the starting material was a mixture of V-doped haplogranite glasses or natural obsidian powder with variable aluminum saturation index (ASI), and synthetic, V-free magnetite of 10-20 μm grain size. The vanadium partition coefficient was found to depend strongly on oxygen fugacity, and to lesser (but still considerable) degrees on melt composition and temperature. A more than 1.5 log unit decrease in DVmgt-melt values with increasing oxygen fugacity can be explained by a change of the dominant valence state of V in the silicate melt. For a given oxygen fugacity buffer DVmgt-melt decreases with increasing temperature, but this reflects mostly the change in absolute fO2 values while the net temperature effect is in fact positive. DVmgt-melt depends significantly on melt composition, resulting in higher D-values with increasing aluminum

  3. The solubility of gold in silicate melts: First results

    Science.gov (United States)

    Borisov, A.; Palme, H.; Spettel, B.

    1993-01-01

    The effects of oxygen fugacity and temperature on the solubility of Au in silicate melts were determined. Pd-Au alloys were equilibrated with silicate of anorthite-diopside eutectic composition at different T-fO2 conditions. The behavior of Au was found to be similar to that of Pd reported recently. Au solubilities for alloys with 30 to 40 at. percent Au decrease at 1400 C from 12 ppm in air to 160 ppb at a log fO2 = -8.7. The slope of the log(Me-solubility) vs. log(fO2) curve is close to 1/4 for Au and the simultaneously determined Pd suggesting a formal valence of Au and Pd of 1+. Near the IW buffer Pd and Au solubilities become even less dependent on fO2 perhaps reflecting the presence of some metallic Au and Pd.

  4. Formation Mechanism of Spinel-Type Inclusions in High-Alloyed Stainless Steel Melts

    Science.gov (United States)

    Park, Joo Hyun

    2007-08-01

    Fundamental thermodynamics of the relationship between high-alloyed stainless steel melts (Fe-20 mass pct Cr-13 mass pct Ni-3 mass pct Si) and the inclusions were investigated. The formation mechanism of the inclusions containing the spinel crystals was developed based on the experimental results and from the compositions of the inclusions in the steel samples taken during plant operations. The molar content of alumina in the inclusions was found to be linearly proportional to the increase of aluminum content, indicating that the inclusions could contain alumina even with less than about 200 ppm aluminum in the steel melt, e.g., steel melts that were mainly deoxidized by silicon. Furthermore, the composition of the inclusions is shown to be a function of the activity of the deoxidizers such as aluminum and silicon in the steel melt. From the analysis of the plant samples, it was found that the contents of MgO and Al2O3 in the calcium silicate type inclusions increased continuously as the steel melt transfers from the argon oxygen decarburization (AOD) converter to the tundish. This composition change in the inclusions originated from the reduction of MgO and Al2O3 in the slags or refractories by silicon in the steel melt. Increases of MgO and Al2O3 contents were prominent in tundish samples, and thus, the spinel phase could be crystallized in the calcium silicate inclusion matrix in the tundish; and finally the spinel crystals grew during cooling of the steel melt through the continuous casting (CC) mold and in the slabs. On the other hand, manganese silicate type inclusions containing chromium oxide were observed after tapping of the molten steel to the ladle. The MnO and Cr2O3 in these inclusions was initially reduced by silicon in the steel melt in the ladle treatment (LT) process, followed by further reduction by aluminum through the LT to the CC mold. The fractions of inclusions containing spinel crystals in cast slabs were negligible at the alumina content of

  5. Aubrite basalt vitrophyres: High sulfur silicate melts and a snapshot of aubrite formation. [Abstract only

    Science.gov (United States)

    Fogel, R. A.

    1994-01-01

    Two aubrite basalt vitrophyre clasts have been found within AMNH thin sections from the Parsa EH3 chondrite and the Khor Temiki aubrite. Polished sections of the Parsa Aubrite Inclusion (PAI) and the Khor Temiki Inclusion (KTI) were studied by optical, electron probe microanalysis (EPMA), and scanning electron microscopy (SEM) techniques with broad-beam and low absorbed EPMA currents used to minimize glass volatile loss. Some data have previously been reported for PAI and KTI may possibly correlate to a previously reported inclusion in Khor Tiimiki. In polished sections, PAI and KTI are approximately equal 4 mm in diameter and contain a large volume of glass. The clasts have similar textural characteristics and are akin to lunar vitrophyre textures. The glasses have high alkali rhyodacitic compositions Al-though PAI is peraluminous, KTI is significantly peralkaline. Additionally, the glasses have elevated sulfur concentrations that are extremely high by geochemical standards. SEM examination for beam overlap of microscopic CaS, FeS, and (Mg, Mn, Fe) S inclusions showed no such contamination. Furthermore, homogeneity of glass S content and low FeO contents help rule out contamination. Materials research data show that under reducing conditions alumino-silicate melts can dissolve up to several weight percent sulfur in the absence of Fe. The high S and alkali contents, the lack of associated high shock features, and the rationalized phase equilibria suggest that PAI and KTI are igneous melting products of an E-chondrite-like source material. Although large-scale impact melting cannot totally be ruled out, the above observations eliminate the possibility of in-situ shock melting.

  6. Multiphase solid inclusions in ultrahigh-pressure metamorphic rocks: A snapshot of anatectic melts during continental collision

    Science.gov (United States)

    Gao, Xiao-Ying; Chen, Yi-Xiang; Zhang, Qiang-Qiang

    2017-09-01

    Partial melting of crustal rocks may take place during continental collision, giving rise to anatectic melts. Their composition and evolution are major concerns in the chemical geodynamics of continental subduction zones. They are often recorded by multiphase solid (MS) inclusions enclosed by peritectic minerals in ultrahigh-pressure (UHP) metamorphic terranes inside collisional orogens. These MS inclusions generally show negative crystal shapes with the wedge-shaped off-shoot structure in garnet, omphacite and kyanite. They contain a number of silicate, carbonate and sulfate minerals such as K-feldspar, plagioclase, quartz, epidote, calcite and barite, with occasional occurrences of magnetite, zircon and pyrite. An integrated study of petrology, mineralogy and geochemistry indicates that the MS inclusions are the primary crystallization product of former silicate and carbonate melts. The silicate melts were derived from dehydration melting of hydrous minerals such as phengite and paragonite in UHP metamorphic rocks, and the carbonate melts were produced by partial melting of subducted carbonate minerals. Some MS inclusions show remarkably high Na contents, suggesting their derivation from dehydration melting of paragonite. In contrast, K-bearing MS inclusions are produced by dehydration melting of K-bearing hydrous minerals like phengite. Many studies have been devoted to the mineralogical and geochemical compositions of MS inclusions in UHP metamorphic rocks, with the aim to determine the time and mechanism of crustal anataxis during collisional orogeny. Various analytical methods were used to characterize the morphology, texture, mineral chemistry and trace element composition of MS inclusions. The results provide insights into the physicochemical properties of anatectic melts in continental subduction zones. The partial melting of deeply subducted crustal rocks would lead to their significant differentiation in lithochemistry and geochemistry. This process has

  7. Evidence of yttrium silicate inclusions in YSZ-porcelain veneers.

    Science.gov (United States)

    Stoner, Brian R; Griggs, Jason A; Neidigh, John; Piascik, Jeffrey R

    2014-04-01

    This report introduces the discovery of crystalline defects that can form in the porcelain veneering layer when in contact with yttria-stabilized zirconia (YSZ). The focus was on dental prostheses and understanding the defects that form in the YSZ/porcelain system; however the data reported herein may have broader implications toward the use and stability of YSZ-based ceramics in general. Specimens were cut from fully sintered YSZ plates and veneering porcelain was applied (veneer. Local EDAX (SEM) was performed in the regions of visible inclusions and showed significant increases in yttrium concentration. TEM specimens also showed apparent inclusions in the porcelain and selected area electron diffraction was performed on these regions and found the inclusions to be crystalline and identified as either yttrium-silicate (Y2 SiO5 ) or yttrium-disilicate (Y2 Si2 O7 ). Micro-CT data showed that yttrium-silicate precipitates were distributed throughout the thickness of the porcelain veneer. Future studies are needed to determine whether many of the premature failures associated with this materials system may be the result of crystalline flaws that form as a result of high temperature yttrium diffusion near the surfaces of YSZ. © 2013 Wiley Periodicals, Inc.

  8. Chemical zonation in olivine-hosted melt inclusions

    Science.gov (United States)

    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

    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

  9. Complexation of Sr in aqueous fluids equilibrated with silicate melts: effect of melt and fluid composition

    Science.gov (United States)

    Borchert, Manuela; Wilke, Max; Schmidt, Christian; Kvashnina, Kristina

    2010-05-01

    At crustal conditions, the fluid-melt partitioning of Sr is mainly controlled by the salinity of the fluid and the composition of the melt (Borchert et al., 2010). The data show a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) to a maximum of 0.3 at an ASI of 1.05. Because fluid-melt partitioning of a given element depends on its complexation in the fluid and its incorporation in the melt, these data imply a change in the Sr speciation at least one of the two phases. For silicate melts, Kohn et al. (1990) found only small changes in the first coordination shell of Sr in a suite of melts with various degrees of polymerization, and argued that incorporation of Sr in the melt should not play a major role in controlling Sr partitioning. For the aqueous fluid, Bai and Koster van Groos (1999) and Webster et al. (1989) suggested a control of the Sr partition coefficient by SrCl2 complexes based on the correlation between partition coefficient and Cl concentration in the fluid after quenching. Both hypotheses cannot explain our partitioning data. Thus, new information on Sr complexation is required. Here, we studied the complexation of Sr in peraluminous or peralkaline melt dissolved in aqueous fluids in-situ at elevated PT conditions using hydrothermal diamond-anvil cells (HDAC) and X-ray absorption near edge structure (XANES) spectroscopy. The starting materials were peraluminous or peralkaline glass and H2O or a chloridic solution. The glass was doped with high concentrations of 5000 or 10000 ppm Sr. We used bulk compositions with 10 to 15 wt.% glass to ensure that the melt was completely dissolved in the fluid at high PT conditions. For qualitative evaluation, we analyzed the starting glasses and various crystalline compounds and standard solutions. The experiments were performed at beamline ID26 at ESRF (Grenoble, France) using a high resolution emission spectrometer and Si(311) monochromator crystals for high resolution and Si

  10. Water content estimation of natural glasses and melt inclusions: a Raman spectroscopy study

    Science.gov (United States)

    Sicola, Stefania; Di Genova, Danilo; Romano, Claudia; Vona, Alessandro; Fanara, Sara; Hess, Kai-Uwe; Dingwell, Donald B.; Landi, Patrizia

    2017-04-01

    Water is the most abundant volatile dissolved in silicate melts and strongly affects melt structure, magma transport and eruptive style. Raman spectroscopy can give insight into the silicate structure and water content of silicate melts. This technique presents several advantages such as: 1) high-spatial resolution; 2) non-destructive character; 3) minor sample preparation 4) crystals detection; and 5) the possibility to perform in-situ investigations at high temperature and pressure. Several approaches to estimate the water content of silicate glasses (mostly iron-free) and melt inclusions have been presented based on internal and/or external calibration. Here, we discuss these different approaches using a wide range of chemical composition of glasses, which has never been investigated so far. We used 25 natural samples from basaltic to rhyolitic composition and water content up to 7wt% (independently measured). By using two different Raman spectrometers we also explore potential causes for variations in the estimation of water content due to instrumental effects. Based on the results of this study, we show that the difference in instrumental response is the main factor against a unique calibration for the estimation of water content. On the other hand, the choice of the analytical procedure depends significantly on the iron content and its oxidation state. We applied the proposed model to a set of melt inclusions trapped in crystals belonging to the Green Tuff eruption (Pantelleria Island, Italy) in order to provide insights on magma pre-eruptive storage conditions (i.e. dissolved water content and iron oxidation state). Finally, we show a simple correlation between the glass structure as inferred by Raman spectroscopy and the glass transition temperature.

  11. Volatile loss during homogenization of lunar melt inclusions

    Science.gov (United States)

    Ni, Peng; Zhang, Youxue; Guan, Yunbin

    2017-11-01

    Volatile abundances in lunar mantle are critical factors to consider for constraining the model of Moon formation. Recently, the earlier understanding of a ;dry; Moon has shifted to a fairly ;wet; Moon due to the detection of measurable amount of H2O in lunar volcanic glass beads, mineral grains, and olivine-hosted melt inclusions. The ongoing debate on a ;dry; or ;wet; Moon requires further studies on lunar melt inclusions to obtain a broader understanding of volatile abundances in the lunar mantle. One important uncertainty for lunar melt inclusion studies, however, is whether the homogenization of melt inclusions would cause volatile loss. In this study, a series of homogenization experiments were conducted on olivine-hosted melt inclusions from the sample 74220 to evaluate the possible loss of volatiles during homogenization of lunar melt inclusions. Our results suggest that significant loss of H2O could occur even during minutes of homogenization, while F, Cl and S in the inclusions remain unaffected. We model the trend of H2O loss in homogenized melt inclusions by a diffusive hydrogen loss model. The model can reconcile the observed experimental data well, with a best-fit H diffusivity in accordance with diffusion data explained by the ;slow; mechanism for hydrogen diffusion in olivine. Surprisingly, no significant effect for the low oxygen fugacity on the Moon is observed on the diffusive loss of hydrogen during homogenization of lunar melt inclusions under reducing conditions. Our experimental and modeling results show that diffusive H loss is negligible for melt inclusions of >25 μm radius. As our results mitigate the concern of H2O loss during homogenization for crystalline lunar melt inclusions, we found that H2O/Ce ratios in melt inclusions from different lunar samples vary with degree of crystallization. Such a variation is more likely due to H2O loss on the lunar surface, while heterogeneity in their lunar mantle source is also a possibility. A

  12. Sulfur Saturation Limits in Silicate Melts and their Implications for Core Formation Scenarios for Terrestrial Planets

    Science.gov (United States)

    Holzheid, Astrid; Grove, Timothy L.

    2002-01-01

    This study explores the controls of temperature, pressure, and silicate melt composition on S solubility in silicate liquids. The solubility of S in FeO-containing silicate melts in equilibrium with metal sulfide increases significantly with increasing temperature but decreases with increasing pressure. The silicate melt structure also exercises a control on S solubility. Increasing the degree of polymerization of the silicate melt structure lowers the S solubility in the silicate liquid. The new set of experimental data is used to expand the model of Mavrogenes and O'Neill(1999) for S solubility in silicate liquids by incorporating the influence of the silicate melt structure. The expected S solubility in the ascending magma is calculated using the expanded model. Because the negative pressure dependence of S solubility is more influential than the positive temperature dependence, decompression and adiabatic ascent of a formerly S-saturated silicate magma will lead to S undersaturation. A primitive magma that is S-saturated in its source region will, therefore, become S-undersaturated as it ascends to shallower depth. In order to precipitate magmatic sulfides, the magma must first cool and undergo fractional crystallization to reach S saturation. The S content in a metallic liquid that is in equilibrium with a magma ocean that contains approx. 200 ppm S (i.e., Earth's bulk mantle S content) ranges from 5.5 to 12 wt% S. This range of S values encompasses the amount of S (9 to 12 wt%) that would be present in the outer core if S is the light element. Thus, the Earth's proto-mantle could be in equilibrium (in terms of the preserved S abundance) with a core-forming metallic phase.

  13. Constraints from olivine-hosted melt inclusions in primitive magmas

    OpenAIRE

    Jennings, Eleanor S.; Gibson, Sally A.; Maclennan, John; Heinonen, Jussi S.

    2017-01-01

    We present major and trace element compositions of 154 re-homogenised olivine-hosted melt inclusions found in primitive rocks (picrites and ferropicrites) from the Mesozoic Paraná–Etendeka and Karoo Continental Flood Basalt (CFB) provinces. The major element compositions of the melt inclusions, especially their Fe/Mg ratios, are variable and erratic, and attributed to the re-homogenisation process during sample preparation. In contrast, the trace element compositions of both the picrite and f...

  14. Silicate and Carbonatite Melts in the Mantle: Adding CO2 to the pMELTS Thermodynamic Model of Silicate Phase Equilibria

    Science.gov (United States)

    Antoshechkina, P. M.; Shorttle, O.

    2016-12-01

    The current rhyolite-MELTS algorithm includes a mixed H2O-CO2 vapor phase, and a self-consistent speciation model for CO2 and CaCO3 in the silicate liquid (Ghiorso & Gualda 2012; 2015). Although intended primarily to model crustal differentiation and degassing, GG15 captures much of the experimentally-observed melting behavior of CO2-rich mafic lithologies, including generation of small-degree carbonatite melts, a miscibility gap between carbonatite and silicate liquids at low P and a smooth transition to a single carbonated-silicate melt at high P (e.g. Dasgupta et al. 2007). However, solid and liquid carbonate phases were not used in calibration of GG15, and it is suitable only for P MySQL database, adapted from LEPR (Hirschmann et al. 2008). Here, we further extend our database, e.g. to include multiple carbonate phases, and combine the calibration scheme with the libalphaMELTS interface to the rhyolite-MELTS, pMELTS, and H2O-CO2 fluid thermodynamic models (see magmasource.caltech.edu/alphamelts). We use a Monte-Carlo type calibration approach to fit the observed phases and compositions, though stop short of a fully Bayesian formulation. The CO2-fluid experimental database has been updated to include more recent and higher P studies, adding approximately 40 pure fluid plus liquid constraints that conform to the selection criteria used in GG15. To further expand the database, we plan to use some or all of: solid carbonate-bearing experiments; coexisting silicate and carbonatite liquids; phase-present, and phase-absent constraints. As a first approximation, we include four carbonate phases: pure calcite and aragonite, and binary solutions for dolomite-ankerite and magnesite-siderite. Following GG15, we have adopted the CO2 fluid model of Duan & Zhang (2006) and added CO2 and CaCO3 species to the pMELTS liquid model. A key question that we hope to address during calibration is whether a Na2CO3 liquid species is justified instead of, or in addition to, CaCO3 for the

  15. Structural controls and mechanisms of diffusion in natural silicate melts

    Science.gov (United States)

    Henderson, P.; Nolan, J.; Cunningham, G. C.; Lowry, R. K.

    1985-04-01

    The diffusion properties of Na, Cs, Ba, Fe and Eu ions have been determined experimentally for a pantellerite melt and of these ions plus Li, Mn and Co in pitchstone melt, using the radiotracer residual-activity method, and narrow platinum capillaries, over the temperature range 1,200 1,400° C. In addition, Eu diffusion in a basaltic and an andesitic melt was determined. Diffusion of all cations follows an Arrhenius relationship, activation energy values being high for diffusion in the pantellerite melt (e.g. Eu: 100 kcal mol-1) except in the case of Na (24.3 kcal mol-1). Activation energies of diffusion in the pitchstone melt are similar to values recorded earlier for andesitic and basaltic melts. The new data are used, along with previously published data for diffusion in other composition melts, to examine the compositional and structural controls on diffusion. The range of diffusivities shows a marked change with melt composition; over two orders of magnitude for a basaltic melt, and nearly four orders for a pantellerite melt (both at 1,300° C). Diffusivity of all cations (except Li and Na) correlates positively with the proportion of network modifying cations. In the case of Li and Na the correlation is negative but the diffusivity of these ions correlates positively with the proportion of Na or of Na + K ions in the bulk melt. Diffusion behaviour in the pantellerite melt departs from the relationships shown by the data for other melt compositions, which could be partly explained by trivalent ions (such as Fe) occupying network forming positions. The diffusivity of alkali metal ions is strongly dependent on ionic radius, but this is not the case with the divalent and trivalent ions; diffusivity of these ions remains relatively constant with change in radius but decreases with increase in ionic charge. A compensation diagram shows four distinct but parallel trends for the majority of the cations in four melt types but the data for Li and Na plot on a separate

  16. Termochemical Models For Slags and Silicate Melts, Review and Perspectives

    Science.gov (United States)

    Ottonello, G.

    Thermochemical models devoted to the comprehension of reactive and mixing properties of silicate melts and slags may be roughly grouped into four main classes: 1) fictive chemical; 2) quasi chemical; 3) fictive structural; 4) polymeric. In the first class we may group the fictive regular mixture approach of Ghiorso and Carmichael [1,2]and its extensions [3-5]and the subregular model of Berman and Brown [6]. To the second class belong the modified quasi chemical approach of Pelton and coworkers [7,8] , and the Kapoor - Froberg cellular model and its extensions [9-11]. The third class has much to share with the second one (and indeed the cellular model could be ascribed to this class as well). To this class belong the "central surround model" of Sastri and Lahiri [12] , the associated solution models of Bjorkman [13], Hastie and coworkers [14]and Goel and coworkers [15], the two sublattice model of Hillert and coworkers [16]and the polynomial expansions of Hoch and Arpshofen [17] . The fourth class encompasses the models of Masson[18-20] , Toop-Samis [21,22]and its extensions [23-25] . The phylosophy beyond each one of the four classes is basically different. Benefits and drawbacks are present in any of them, and applications are often limited to simple systems (or to sufficiently complex systems, in the case of arbitrary deconvolutions of type 1) and to limited P-T ranges. The crucial aspects of the various models will be outlined to some extent. It will be shown that, often, model conflictuality is only appartent and that, in some cases, model failure is unperceived by acritical utilizers. New perspectives in the future research devoted to the comprehension of melt reactivity in compositionally complex systems, with special enphasis on the solubility of gaseous components and unmixing, will be finally discussed. References: [1] Ghiorso M.S. and Carmichael I.S.E. (1980) Contrib. Mineral. Petrol., 71, 323-342. [2] Ghiorso M.S., Carmichael I.S.E., Rivers M.L. and Sack

  17. Energetics of silicate melts from thermal diffusion studies

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.

    1992-07-01

    Efforts are reported in the following areas: laboratory equipment (multianvils for high P/T work, pressure media, SERC/DL sychrotron), liquid-state thermal diffusion (silicate liquids, O isotopic fractionation, volatiles, tektites, polymetallic sulfide liquids, carbonate liquids, aqueous sulfate solutions), and liquid-state isothermal diffusion (self-diffusion, basalt-rhyolite interdiffusion, selective contamination, chemical diffusion).

  18. Partitioning behavior of chlorine and fluorine in the system apatite melt fluid. II: Felsic silicate systems at 200 MPa

    Science.gov (United States)

    Webster, James D.; Tappen, Christine M.; Mandeville, Charles W.

    2009-02-01

    Hydrothermal experiments were conducted to determine the partitioning of Cl between rhyolitic to rhyodacitic melts, apatite, and aqueous fluid(s) and the partitioning of F between apatite and these melts at ca. 200 MPa and 900-924 °C. The number of fluid phases in our experiments is unknown; they may have involved a single fluid or vapor plus saline liquid. The partitioning behavior of Cl between apatite and melt is non-Nernstian and is a complex function of melt composition and the Cl concentration of the system. Values of DClapat/melt (wt. fraction of: Cl in apatite/Cl in melt) vary from 1 to 4.5 and are largest when the Cl concentrations of the melt are at or near the Cl-saturation value of the melt. The Cl-saturation concentrations of silicate melts are lowest in evolved, silica-rich melts, so with elevated Cl concentrations in a system and with all else equal, the maximum values of DClapat/melt occur with the most felsic melt. In contrast, values of DFapat/melt range from 11 to 40 for these felsic melts, and many of these are an order of magnitude greater than those applying to basaltic melts at 200 MPa and 1066-1150 °C. The Cl concentration of apatite is a simple and linear function of the concentration of Cl in fluid. Values of DClfluid/apat for these experiments range from 9 to 43, and some values are an order of magnitude greater than those determined in 200-MPa experiments involving basaltic melts at 1066-1150 °C. In order to determine the concentrations and interpret the behavior of volatile components in magmas, the experimental data have been applied to the halogen concentrations of apatite grains from chemically evolved rocks of Augustine volcano, Alaska; Krakatau volcano, Indonesia; Mt. Pinatubo, Philippines; Mt. St. Helens, Washington; Mt. Mazama, Oregon; Lascar volcano, Chile; Santorini volcano, Greece, and the Bishop Tuff, California. The F concentrations of these magmas estimated from apatite-melt equilibria range from 0.06 to 0.12 wt% and are

  19. Pt, Au, Pd and Ru Partitioning Between Mineral and Silicate Melts: The Role of Metal Nanonuggets

    Science.gov (United States)

    Malavergne, V.; Charon, E.; Jones, J.; Agranier, A.; Campbell, A.

    2012-01-01

    The partition coefficients of Pt and other Pt Group Elements (PGE) between metal and silicate D(sub Metal-Silicate) and also between silicate minerals and silicate melts D(sub Metal-Silicate) are among the most challenging coefficients to obtain precisely. The PGE are highly siderophile elements (HSE) with D(sub Metal-Silicate) >10(exp 3) due to the fact that their concentrations in silicates are very low (ppb to ppt range). Therefore, the analytical difficulty is increased by the possible presence of HSE-rich-nuggets in reduced silicate melts during experiments). These tiny HSE nuggets complicate the interpretation of measured HSE concentrations. If the HSE micro-nuggets are just sample artifacts, then their contributions should be removed before calculations of the final concentration. On the other hand, if they are produced during the quench, then they should be included in the analysis. We still don't understand the mechanism of nugget formation well. Are they formed during the quench by precipitation from precursor species dissolved homogeneously in the melts, or are they precipitated in situ at high temperature due to oversaturation? As these elements are important tracers of early planetary processes such as core formation, it is important to take up this analytical and experimental challenge. In the case of the Earth for example, chondritic relative abundances of the HSE in some mantle xenoliths have led to the concept of the "late veneer" as a source of volatiles (such as water) and siderophiles in the silicate Earth. Silicate crystal/liquid fractionation is responsible for most, if not all, the HSE variation in the martian meteorite suites (SNC) and Pt is the element least affected by these fractionations. Therefore, in terms of reconstructing mantle HSE abundances for Mars, Pt becomes a very important player. In the present study, we have performed high temperature experiments under various redox conditions in order to determine the abundances of Pt, Au

  20. Skaergaard parental magma constrained by melt inclusions of cumulus plagioclase

    Science.gov (United States)

    Jakobsen, J. K.; Kent, A. J. R.; Tegner, C.; Brooks, C. K.

    2003-04-01

    Cumulus plagioclase of the 55 Ma Skaergaard intrusion, East Greenland, contains two types melt inclusions. Their form varies from rounded to elongate bodies up to 250 micrometer long often parallel to albite twins. Type-1 inclusions are polycrystalline and composed of plagioclase, augite, magnetite, ilmenite and accessory K-feldspar, biotite, and amphibole. Their abundance varies throughout the intrusion but it is greatest in the Middle Zone but absent in the Hidden Zone. A previous study of type-1 inclusions of the Middle Zone estimated they represent SiO2-poor (46 wt%) and FeO-rich (17 wt%) ferrobasalt calculated by summing mineral compositions weighted by mode (Hanghøj et al., 1995, CMP 120, 265-269). Our study aims to homogenise the crystallised melt inclusion by experimental reheating. Preliminary data of Lower Zone C shows higher SiO2 (50 wt%) and lower FeO (11-12 wt%) and lower titanium than Hanghøj et al. (1995) and all other estimates of Skaergaard magmas. We presently speculate that the unusual composition of the homogenised inclusions is an artefact of overshooting the homogenization temperature (1160°C which is higher than the expected liquidus temperature of 1100 °C) and/or diffusional exchange between host crystal and the melt inclusions. We will continue to test these hypothesis. Type-2 inclusions are glassy or microcrystalline with small oxide crystals. They are found in very high abundance in autoliths thought to represent the Hidden Zone. Homogenised type-2 inclusions have 48 wt% SiO2 and 12 wt% FeO which is similar to chilled margin samples suggested as parental Skaergaard magmas. The rare earth element patterns of the type-2 inclusions are similar to coeval continental flood basalts of the Blosseville coast. We conclude that type-2 melt inclusions represent the parental liquid to the Skaergaard intrusion.

  1. Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia

    Directory of Open Access Journals (Sweden)

    Elena Badanina

    2012-11-01

    Full Text Available In this paper we show that the pegmatite-forming processes responsible for the formation of the Malkhan pegmatites started at magmatic temperatures around 720 °C. The primary melts or supercritical fluids were very water- and boron-rich (maximum values of about 10% (g/g B2O3 and over the temperature interval from 720 to 600 °C formed a pseudobinary solvus, indicated by the coexistence of two types of primary melt inclusions (type-A and type-B representing a pair of conjugate melts. Due to the high water and boron concentration the pegmatite-forming melts are metastable and can be characterized either as genuine melts or silicate-rich fluids. This statement is underscored by Raman spectroscopic studies. This study suggested that the gel state proposed by some authors cannot represent the main stage of the pegmatite-forming processes in the Malkhan pegmatites, and probably in all others. However there are points in the evolution of the pegmatites where the gel- or gel-like state has left traces in form of real gel inclusions in some mineral in the Malkhan pegmatite, however only in a late, fluid dominated stage.

  2. Eclogite-associated potassic silicate melts and chloride-rich fluids in the mantle: a possible connection

    Science.gov (United States)

    Safonov, O.; Butvina, V.

    2009-04-01

    Relics of potassium-rich (4-14 wt. % of K2O and K2O/Na2O > 1.0) melts are a specific features of some partially molten diamondiferous eclogite xenoliths in kimberlites worldwide [1, 2]. In addition, potassic silicic melt inclusions with up to 16 wt. % of K2O are associated with eclogite phases in kimberlitic diamonds (O. Navon, pers. comm.). According to available experimental data, no such potassium contents can be reached by "dry" and hydrous melting of eclogite. These data point to close connection between infiltration of essentially potassic fluids, partial melting and diamond formation in mantle eclogites [2]. Among specific components of these fluids, alkali chlorides, apparently, play an important role. This conclusion follows from assemblages of the melt relics with chlorine-bearing phases in eclogite xenoliths [1], findings of KCl-rich inclusions in diamonds from the xenoliths [3], and concentration of Cl up to 0.5-1.5 wt. % in the melt inclusions in diamonds. In this presentation, we review our experimental data on reactions of KCl melts and KCl-bearing fluids with model and natural eclogite-related minerals and assemblages. Experiments in the model system jadeite(±diopside)-KCl(±H2O) at 4-7 GPa showed that, being immiscible, chloride liquids provoke a strong K-Na exchange with silicates (jadeite). As a result, low-temperature ultrapotassic chlorine-bearing (up to 3 wt. % of Cl) aluminosilicate melts form. These melts is able to produce sanidine, which is characteristic phase in some partially molten eclogites. In addition, in presence of water Si-rich Cl-bearing mica (Al-celadonite-phlogopite) crystallizes in equilibrium with sanidine and/or potassic melt and immiscible chloride liquid. This mica is similar to that observed in some eclogitic diamonds bearing chloride-rich fluid inclusions [4], as well as in diamonds in partially molten eclogites [2]. Interaction of KCl melt with pyrope garnet also produce potassic aluminosilicate melt because of high

  3. Activity composition relationships in silicate melts. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Glazner, A.F.

    1990-12-31

    Equipment progress include furnace construction and electron microprobe installation. The following studies are underway: phase equilibria along basalt-rhyolite mixing line (olivine crystallization from natural silicic andensites, distribution of Fe and Mg between olivine and liquid, dist. of Ca and Na between plagioclase and liquid), enthalpy-composition relations in magmas (bulk heat capacity of alkali basalt), density model for magma ascent and contamination, thermobarometry in igneous systems (olivine/plagioclase phenocryst growth in Quat. basalt), high-pressure phase equilibria of alkali basalt, basalt-quartz mixing experiments, phase equilibria of East African basalts, and granitic minerals in mafic magma. (DLC)

  4. Melting and solidification of bismuth inclusions in aluminium

    DEFF Research Database (Denmark)

    Thoft, N.B.; Bohr, J.; Buras, B.

    1995-01-01

    Supercooling of crystalline bismuth inclusions in aluminium crystals has been observed and studied with different techniques: x-ray diffraction, in situ Rutherford backscattering/channelling spectrometry and transmission electron microscopy. The results of the measurements with different experime......Supercooling of crystalline bismuth inclusions in aluminium crystals has been observed and studied with different techniques: x-ray diffraction, in situ Rutherford backscattering/channelling spectrometry and transmission electron microscopy. The results of the measurements with different...... experimental methods (and on different samples) agree remarkably well. The inclusions melt at temperatures at or below the bismuth bulk melting point, and the solid/liquid phase transition exhibits a hysteresis of 100-150 K. Average inclusion sizes ranged from a few nm to some tens of nm. The x-ray diffraction...

  5. Effect of melting conditions on striae in iron-bearing silicate melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Yue, Yuanzheng

    2012-01-01

    Chemical striae are present in a broad range of glass products, but due to their negative impact on e.g., the optical and mechanical properties, elimination of striae from melts is a key issue in glass technology. By varying melting temperatures, retentions times and redox conditions of an iron......-bearing calciumaluminosilicate melt, we quantify the effect of each of the three melting parameters on the stria content in the melt. The quantification of the stria content in the melt is conducted by means of image analysis on casted melt samples. We find that in comparison to an extension of retention time an increase...... of melt temperature and/or a decrease of viscosity play a more important role in decreasing the stria content. We also demonstrate that the extent of striation is influenced by the crucible materials that causes a change of redox state of the melt, and hence its viscosity. We discuss the effect of other...

  6. Experimental calibration of a new oxybarometer for silicic magmas based on vanadium partitioning between magnetite and silicate melt

    Science.gov (United States)

    Arató, Róbert; Audétat, Andreas

    2017-07-01

    Partition coefficients of vanadium between magnetite and rhyolitic silicate melt, DVmgt/melt, were experimentally determined as a function of oxygen fugacity (0.7-4.0 log units above the fayalite-magnetite-quartz buffer), temperature (800-1000 °C), melt alumina saturation index (ASI = 0.74-1.14), magnetite composition (0.2-14 wt% TiO2) and pressure (1-5 kbar; at H2O saturation). Experiments were performed by equilibrating small (≤20 μm), V-free magnetite grains in V-doped silicate melts (∼100 ppm V) and then analyzing both phases by LA-ICP-MS. Attainment of equilibrium was demonstrated by several reversal experiments. The results suggest that DVmgt/melt depends strongly on fO2, increasing by 1.5-1.7 log units from the MnO-Mn3O4 buffer to the Ni-NiO buffer, and to lesser (but still considerable) extents on melt alumina saturation index (ASI; increasing by 0.3-0.7 log units over 0.4 ASI units) and temperature (increasing by 0.3-0.7 log units over a 200 °C interval at a fixed fO2 buffer). Magnetite composition and melt water content seem to have negligible effects. The data were fitted by the following linear regression equation: in which temperature is given in K, ASI refers to molar Al2O3/(CaO + Na2O + K2O) and ΔFMQ refers to the deviation of fO2 (in log units) from the fayalite-magnetite-quartz buffer. This equation reproduces all of our data within 0.3 log units, and 89% of them within 0.15 log units. The main advantages of this new oxybarometer over classical magnetite-ilmenite oxybarometry are (1) that it can be applied to rocks that do not contain ilmenite, and (2) that it is easier to apply to slowly-cooled rocks such as granites.

  7. Primary crustal melt compositions: Insights into the controls, mechanisms and timing of generation from kinetics experiments and melt inclusions

    Science.gov (United States)

    Acosta-Vigil, Antonio; London, David; Morgan, George B.; Cesare, Bernardo; Buick, Ian; Hermann, Jörg; Bartoli, Omar

    2017-08-01

    We explore the controls, mechanisms and timing of generation of primary melts and their compositions, and show that the novel studies of melt inclusions in migmatites can provide important insights into the processes of crustal anatexis of a particular rock. Partial melting in the source region of granites is dependent on five main processes: (i) supply of heat; (ii) mineral-melt interface reactions associated with the detachment and supply of mineral components to the melt, (iii) diffusion in the melt, (iv) diffusion in minerals, and (v) recrystallization of minerals. As the kinetics of these several processes vary over several orders of magnitude, it is essential to evaluate in Nature which of these processes control the rate of melting, the composition of melts, and the extent to which residue-melt chemical equilibrium is attained under different circumstances. To shed light on these issues, we combine data from experimental and melt inclusion studies. First, data from an extensive experimental program on the kinetics of melting of crustal protoliths and diffusion in granite melt are used to set up the necessary framework that describes how primary melt compositions are established during crustal anatexis. Then, we use this reference frame and compare compositional trends from experiments with the composition of melt inclusions analyzed in particular migmatites. We show that, for the case of El Hoyazo anatectic enclaves in lavas, the composition of glassy melt inclusions provides important information on the nature and mechanisms of anatexis during the prograde suprasolidus history of these rocks, including melting temperatures and reactions, and extent of melt interconnection, melt homogenization and melt-residue equilibrium. Compositional trends in several of the rehomogenized melt inclusions in garnet from migmatites/granulites in anatectic terranes are consistent with diffusion in melt-controlled melting, though trace element compositions of melt inclusions

  8. A study of redox kinetic in silicate melt; Etude cinetique des reactions d'oxydoreduction dans les silicates

    Energy Technology Data Exchange (ETDEWEB)

    Magnien, V

    2005-12-15

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  9. Glass Forming Ability of Sub-Alkaline Silicate Melts

    Science.gov (United States)

    Vetere, F. P.; Iezzi, G.; Behrens, H.; Holtz, F.; Ventura, G.; Misiti, V.; Mollo, S.; Perugini, D.

    2014-12-01

    The glass forming ability (GFA) and critical cooling rate (Rc) of six natural sub-alkaline melts from basalt to rhyolite (i.e., B100, B80R20, B60R40, B40R60, B20R80, and R100) have been quantified through cooling-induced solidification experiments of 9000, 1800, 180, 60, 7 and 1 °C/h conducted at ambient pressure and air buffering conditions, in a temperature range between 1300 °C (superliquidus region) and 800 °C (glass transition region), The phase proportion in each run-product was determined by image analysis on about 500 BS-SEM microphotographs. The phase assemblage consists of glass, clinopyroxene, spinel, and plagioclase with the occurrence of sporadic olivine, orthopyroxene and melilite. Both the glass and crystalline fractions are well correlated with the composition of residual melt. Generally, the amount of crystals decreases with increasing cooling rate. However, some exceptions occurs showing no correlations or even opposite trends. For the example of, Al2O3 and CaO in clinopyroxenes from B100, B80R20, B60R40 and B40R60, their concentrations scale as a function of both cooling rate and the degree of clinopyroxene crystallization. The value of Rc changes of 5 order of magnitude from <1 to ~9000 °C/h when the melt composition changes from R100 to B100, respectively. The most important Rc variations are measured between B80R20 and B60R40, levelling off towards B100. This trend scales with NBO/T (non bridging oxygen per tetrahedron) and can be modelled by the following master sigmoid equation: Rc = a / 1+e-(NBO/T-xo/b), where a, b and xo are fitting parameters equal to 9214, 0.040 and 0.297, respectively. Our data can be used to retrieve the solidification conditions of aphyric, degassed and oxidised lavas. Indeed, the relationship between crystal content and cooling kinetics suggests that the solidification path is more complex than previously assumed and strongly non-linear. This finding has also implications to design glass-ceramics based on natural

  10. Partitioning Behavior of Mn, Fe, Co, Ni and Zn between an Octahedral Site in Olivine and Silicate Melt

    OpenAIRE

    Hashizume, Hideo; Hariya, Yu

    1992-01-01

    Partition coefficients of Mn2+, Fe2+, Co2+, Ni2+ and Zn2+ between olivine and silicate melt have been determined in the system Mg2SiO4-SiO2-H2O at high pressure and temperature. A partition coefficient is defined by the ratio of the concentration of an element in olivine to that of the element in silicate melt. Olivine has two octahedral sites (M1 and M2 sites). Elements are partitioned among an M1, an M2 sites and silicate melt. We distributed the bulk concentration of the element in olivine...

  11. Application of mean-field model of polymer melt intercalation in organo-silicates for nanocomposites.

    Science.gov (United States)

    Meneghetti, Paulo; Qutubuddin, Syed

    2005-08-15

    The mean-field, lattice-based model of polymer melt intercalation in organically-modified layered silicates (OLS) originally developed by Vaia and Giannelis was applied for different polymers such as poly(methyl methacrylate) (PMMA), polypropylene (PP), and poly(ethylene oxide) (PEO). The nature of each polymer controls significantly the intercalation of the system. The internal energy change caused by the interaction of polymer, surfactant and clay is the strongest factor in determining the equilibrium structure of the nanocomposite system.

  12. Velocity of a freely rising gas bubble in a soda-lime silicate glass melt

    Science.gov (United States)

    Hornyak, E. J.; Weinberg, M. C.

    1984-01-01

    A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

  13. Evolution of melt-vapor surface tension in silicic volcanic systems: Experiments with hydrous melts

    Science.gov (United States)

    Mangan, M.; Sisson, T.

    2005-01-01

    We evaluate the melt-vapor surface tension (??) of natural, water-saturated dacite melt at 200 MPa, 950-1055??C, and 4.8-5.7 wt % H2O. We experimentally determine the critical supersaturation pressure for bubble nucleation as a function of dissolved water and then solve for ?? at those conditions using classical nucleation theory. The solutions obtained give dacite melt-vapor surface tensions that vary inversely with dissolved water from 0.042 (??0.003) J m-2 at 5.7 wt% H2O to 0.060 (??0.007) J m-2 at 5.2 wt% H2O to 0.073 (??0.003) J m-2 at 4.8 wt% H2O. Combining our dacite results with data from published hydrous haplogranite and high-silica rhyolite experiments reveals that melt-vapor surface tension also varies inversely with the concentration of mafic melt components (e.g., CaO, FeOtotal, MgO). We develop a thermodynamic context for these observations in which melt-vapor surface tension is represented by a balance of work terms controlled by melt structure. Overall, our results suggest that cooling, crystallization, and vapor exsolution cause systematic changes in ?? that should be considered in dynamic modeling of magmatic processes.

  14. Volatiles and trace elements in melt inclusions from Siberian Traps

    Science.gov (United States)

    Novikova, S.; Edmonds, M.; Maclennan, J.; Svensen, H.

    2014-12-01

    The eruption of the Siberian Traps Large Igneous Province (LIP) was synchronous with the largest known mass extinction, at the Permo-Triassic boundary. Understanding the volatile budget of the eruptions and hence their potential effects on climate is of critical importance. The volcanism spanned an enormous territory (5 million km2) over 0.8 Ma and the magmas feeding the eruptions were heterogeneous in their chemistry in space and time. In terms of volatiles in pre-eruptive magmas, there are multiple possible sources: the mantle (including metasomatized lithosphere) and crustal rocks and sediments. Discriminating between these sources requires not only microanalysis of volatiles in melt inclusions, but also analysis of trace elements. Crucially, the magmas sampled for this study did not intersect and assimilate evaporite deposits or brines prior to emplacement as sills or eruption as lavas, in contrast to previous studies, which might allow mantle-derived volatile heterogeneity to be preserved in the melts. We present a new dataset of clinopyroxene-hosted melt inclusion geochemistry. Crystalline inclusions in clinopyroxene with Mg# from 69.2 to 82.6 were homogenized at temperatures of 1190°C and fO2 of FMQ-1 in a high temperature gas mixing furnace. We show that, for this particular suite of lavas, considerable variability exists in trace and volatile element ratios (e.g. La/Yb, Nb/Y, Ba/La, F/Nd, Cl/K) that may be explained entirely by mantle heterogeneity. The most depleted melts (e.g. low La/Yb) have the highest range and values of S/Dy, Cl/K and F/Nd ratios; and the most "enriched" melts (highest La/Yb) exhibit low volatile/trace element ratios. These trends are consistent with mixing between end member sources: low degrees of melting of a volatile-poor source and high degrees of melting of a volatile-rich component with a depleted trace element signature (which might be consistent with minimally devolatilised recycled oceanic crust). There is no clear

  15. A Silicate Inclusion in Puente del Zacate, a IIIA Iron Meteorite

    Science.gov (United States)

    Olsen, Edward J.; Davis, Andrew M.; Clayton, Robert N.; Mayeda, Toshiko K.; Moore, Carleton B.; Steele, Ian M.

    1996-09-01

    The IIIA and IIIB iron meteorites are considered to have formed in the cores of asteroids. A silicate inclusion within the IIIA meteorite Puente del Zacate consisting of olivine (Fa_4), low-calcium pyroxene (Fs_6Wo_1), chromium diopside (Fs_3Wo47), plagioclase (An14Or_4), graphite, troilite, chromite, daubreelite, and iron metal resembles inclusions in IAB iron meteorites. The oxygen isotopic composition of the Puente del Zacate inclusion is like chromite and phosphate inclusions in other IIIA and IIIB irons. The Puente del Zacate inclusion may have been derived from the lower mantle of the IIIAB parent asteroid.

  16. Controls on the solubility of rhenium in silicate melt: Implications for the osmium isotopic composition of Earth's mantle

    Science.gov (United States)

    Bennett, Neil R.; Brenan, James M.

    2013-01-01

    The solubility of Re and Au in haplobasaltic melt has been investigated at 1673-2573 K, 0.1 MPa-2 GPa and IW-1 to +2.5, in both carbon-saturated and carbon-free systems. Results extend the existing, low pressure and temperature, dataset to more accurately predict the results of metal-silicate equilibrium at the base of a terrestrial magma ocean. Solubilities in run-product glasses were measured by laser ablation ICP-MS, which allows for the explicit assessment of contamination by metal inclusions. The Re and Au content of demonstrably contaminant-free glasses increases with temperature, and shows variation with oxygen fugacity (fO2) similar to previous results, although lower valence states for Re (1+, 2+) are suggested by the data. At 2 GPa, and ΔIW of +1.75 to +2, the metal-silicate partition coefficient for Re (DMet/Sil) is defined by the relation LogDMet/SilRe=0.50(±0.022)×10/T(K)+3.73(±0.095) For metal-silicate equilibrium to endow Earth's mantle with the observed time-integrated chondritic Re/Os, (and hence 187Os/188Os), DMet/Sil for both elements must converge to a common value. Combined with previously measured DMet/Sil for Os, the estimated temperature at which this convergence occurs is 4500 (±900) K. At this temperature, however, the Re and Os content of the equilibrated silicate is ˜100-fold too low to explain mantle abundances. In the same experiments, much lower Dmet/sil values have been determined for Au, and require the metal-silicate equilibration temperature to be <3200 K, as hotter conditions result in an excess of Au in the mantle. Thus, the large disparity in partitioning between Re or Os, and Au at core-forming temperatures argues against their mantle concentrations set solely by metal-silicate equilibrium at the base of a terrestrial magma ocean.

  17. Trace element partitioning between aqueous fluids and silicate melts measured with a proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Adam, J.; Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia). School of Earth Sciences; Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1996-12-31

    A series of experiments were performed to examine the capacity of H{sub 2}O-fluids to concentrate and transport incompatible elements through peridotitic mantle and metamorphosed (eclogitic) ocean crust. Two naturally occurring rock compositions, trondhjemitic and basanitic, were used in experiments. The proton microprobe was used to determine the trace element concentrations in the solutes from H{sub 2}O-fluids equilibrated at 900-1100 degree C, 2.0 GPa with water saturated melts of trondhjemitic and basanitic compositions. Partitioning data for H{sub 2}O-fluids and silicate melts show that H{sub 2}O-fluids equilibrated with mantle peridotites will not be strongly enriched in trace elements relative to their wallrocks, and thus they melts do not strongly concentrate alkaline earths Th and U, relative to high-field strength elements. 3 refs., 1 tab., 2 figs.

  18. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

    Science.gov (United States)

    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper

    2016-03-01

    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  19. Polymerisation, basicity, oxidation state and their role in ionic modelling of silicate melts

    Directory of Open Access Journals (Sweden)

    R. Moretti

    2005-06-01

    Full Text Available In order to describe and quantify the reactivity of silicate melts, the ionic notation provided by the Temkin formalism has been historically accepted, giving rise to the study of melt chemical equilibria in terms of completely dissociated ionic species. Indeed, ionic modelling of melts works properly as long as the true extension of the anionic matrix is known. This information may be attained in the framework of the Toop-Samis (1962a,b model, through a parameterisation of the acid-base properties of the dissolved oxides. Moreover, by combining the polymeric model of Toop and Samis with the «group basicity» concept of Duffy and Ingram (1973, 1974a,b, 1976 the bulk optical basicity (Duffy and Ingram, 1971; Duffy, 1992 of molten silicates and glasses can be split into two distinct contributions, i.e. the basicity of the dissolved basic oxides and the basicity of the polymeric units. Application to practical cases, such as the assessment of the oxidation state of iron, require bridging of the energetic gap between the standard state of completely dissociated component (Temkin standard state and the standard state of pure melt component at P and T of interest. On this basis it is possible to set up a preliminary model for iron speciation in both anhydrous and hydrous aluminosilicate melts. In the case of hydrous melts, I introduce both acidic and basic dissociation of the water component, requiring the combined occurrence of H+ cations, OH- free anions and, to a very minor extent, of T-OH groups. The amphoteric behaviour of water revealed by this study is therefore in line with the earlier prediction of Fraser (1975.

  20. [A study of phonon vibration like modes for aggregation structure in silicate melts by high temperature Raman spectrum].

    Science.gov (United States)

    Xu, Pei-Cang; Li, Ru-Bi; Shang, Tong-Ming; Zhou, Jian; Sun, Jian-Hua; You, Jing-Lin

    2010-05-01

    Silicate melts are special fractal dimension system that is metastable state of near-way order and far-way disorder. In this paper, the size of nanometer aggregation structure and the frequences of phonon vibration like mode in the low dimension silicate series (CaO-Al2O3-SiO2 and Na2-Al2O3-SiO2 series) synthesized via high temperature melting and sol gel methods were measured by means of small-angle X-ray scattering (SAXS), low wavenumber Raman spectrum (LWRS) and high temperature Raman spectrum (HTRS in situ measuring). The nanometer self-similarity aggregation structure(it's size is about a few nm to a few tens nm) and phonic phonon vibration like modes of low temperature silicate gel, high temperature silicate melts and it's quenching glasses phases were obtained. So a quantitative method by HTRS for measuring the aggregation size in the high temperature melts was established. The results showed that the aggregation size of the silicate melts is smaller at high temperature than at room temperature and the number of bridge oxygen in one Si-O tetrahedron in network structure units is decreasing at high temperature. This study work provides important theory and information for deliberating geochemistry characteristic, crystallization & evolution of natural magma and enhancing performance of low dimension silicate matelials.

  1. High-temperature apparatus for chaotic mixing of natural silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Morgavi, D.; Petrelli, M.; Vetere, F. P.; González-García, D.; Perugini, D., E-mail: diego.perugini@unipg.it [Department of Physics and Geology, Petro-Volcanology Research Group (PVRG), University of Perugia, Piazza Università, Perugia 06100 (Italy)

    2015-10-15

    A unique high-temperature apparatus was developed to trigger chaotic mixing at high-temperature (up to 1800 °C). This new apparatus, which we term Chaotic Magma Mixing Apparatus (COMMA), is designed to carry out experiments with high-temperature and high-viscosity (up to 10{sup 6} Pa s) natural silicate melts. This instrument allows us to follow in time and space the evolution of the mixing process and the associated modulation of chemical composition. This is essential to understand the dynamics of magma mixing and related chemical exchanges. The COMMA device is tested by mixing natural melts from Aeolian Islands (Italy). The experiment was performed at 1180 °C using shoshonite and rhyolite melts, resulting in a viscosity ratio of more than three orders of magnitude. This viscosity ratio is close to the maximum possible ratio of viscosity between high-temperature natural silicate melts. Results indicate that the generated mixing structures are topologically identical to those observed in natural volcanic rocks highlighting the enormous potential of the COMMA to replicate, as a first approximation, the same mixing patterns observed in the natural environment. COMMA can be used to investigate in detail the space and time development of magma mixing providing information about this fundamental petrological and volcanological process that would be impossible to investigate by direct observations. Among the potentials of this new experimental device is the construction of empirical relationships relating the mixing time, obtained through experimental time series, and chemical exchanges between the melts to constrain the mixing-to-eruption time of volcanic systems, a fundamental topic in volcanic hazard assessment.

  2. The effect of inversion of matrix and inclusions composition in liquation phospho-silicate glasses.

    Science.gov (United States)

    Sitarz, M

    2011-08-15

    Silico-phosphate glasses of XCaPO(4)-SiO(2) and XCaPO(4)-AlPO(4)-SiO(2) (X=Na(+) and/or K(+)) system have been the subject of the presented investigations. Glasses belonging to those systems are characterized by a liquation phenomenon-spherical amorphous inclusions dispersed in an amorphous matrix. Thorough EDX investigations have shown that introduction of aluminum ions into the structure of phospho-silicate glasses results in inversion of matrix and inclusions composition, when XCaPO(4) exceeds 25-35% mol. Such a substantial influence of aluminum ions on phospho-silicate glasses texture as well as matrix and inclusions composition (inversion) must be a result of structural changes. (27)Al MAS NMR research stated that aluminum ions in structures of XCaPO(4)-AlPO(4)-SiO(2) phospho-silicate glasses always acts as a glass-forming ion-i.e. aluminum always occupies fourfold coordinated sites. (23)Na and (31)P MAS NMR research has shown that the inversion of matrix and inclusions composition, brought about by introduction of aluminum ions into the structure of phospho-silicate glasses, is an outcome of a change in phosphorous and alkaline ions coordination. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Paracetamol-loaded poly(epsilon-caprolactone) layered silicate nanocomposites prepared using hot-melt extrusion.

    Science.gov (United States)

    Campbell, Kayleen; Qi, Sheng; Craig, Duncan Q M; McNally, Tony

    2009-12-01

    Composites of paracetamol loaded poly(epsilon-caprolactone) with layered silicates (nanoclays) were prepared using hot-melt extrusion. The paracetamol crystals and layered silicates formed both intercalated and partially exfoliated nanocomposite morphologies depending on composition. The dissolution and initial burst effect were retarded slightly by the nanoclay. T(m) and T(c) of poly(caprolactone) (PCL) were unaffected by the presence of nanoclay, but the crystalline content decreased. The highly dispersed nanoplatelets hindered the mobility of PCL chains and alter the crystallization behavior of PCL. The T(g) of PCL increased by up to 15 degrees C on addition of a synthetic fluromica, as the nanoclay constrained chain motion and tethered PCL chains through hydrogen bonding to hydroxyl groups on the edges of the clay platelets. The tensile mechanical properties of PCL were unaffected when a naturally derived clay (montmorillonite) and paracetamol were blended. In contrast, the modulus of PCL increased by 500% and the stress and elongation at break decreased by 30% for composites prepared with a partially synthetic fluoromica. The study has therefore demonstrated that nanocomposite formation is a potentially highly useful means of manipulating the mechanical properties of melt extrusion systems. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

  4. Uranium in the silicate inclusions of stony-iron and iron meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Crozaz, G.; Sibley, S.F.; Tasker, D.R. (Washington Univ., St. Louis, MO (USA). Dept. of Earth and Planetary Sciences; Washington Univ., St. Louis, MO (USA). McDonnell Center for the Space Sciences)

    1982-05-01

    The microdistribution of U has been studied, using fission track techniques, in eleven mesosiderites, seven pallasites and four iron meteorites with silicate inclusions. When concentrated, U is usually found in phosphates: merrillite and/or chlorapatite. As in stony meteorites, the U concentrations in a given phosphate phase are highly variable from meteorite to meteorite and sometimes also exhibit variations in the same meteorite. Uranium is found to be concentrated in merrillite in all the mesosiderites except Bondoc where none was observed. No U-rich phase was identified in six of the seven pallasites. In the seventh, Marjalahti, there are merrillite grains with concentrations ranging from 0.06 to 0.14 ppm. Where observed, the phosphates from silicate inclusions in the irons appear to have U concentrations similar to the mesosiderites.

  5. A micro-scale investigation of melt production and extraction in the upper mantle based on silicate melt pockets in ultramafic xenoliths from the Bakony-Balaton Highland Volcanic Field (Western Hungary)

    DEFF Research Database (Denmark)

    Bali, Eniko; Zanetti, A.; Szabo, C.

    2008-01-01

    Mantle xenoliths in Neogene alkali basalts of the Bakony-Balaton Highland Volcanic Field (Western Hungary) frequently have melt pockets that contain silicate minerals, glass, and often carbonate globules. Textural, geochemical and thermobarometric data indicate that the melt pockets formed...

  6. What can we learn from melt inclusions in migmatites and granulites?

    Science.gov (United States)

    Cesare, B.; Acosta-Vigil, A.; Bartoli, O.; Ferrero, S.

    2015-12-01

    With less than two decades of activity, research on melt inclusions (MI) in crystals from rocks that have undergone crustal anatexis - migmatites and granulites - is a recent addition to crustal petrology and geochemistry. Studies on this subject started with glassy inclusions in anatectic crustal enclaves in lavas, and then progressed to regionally metamorphosed and partially melted crustal rocks, where melt inclusions are normally crystallized into a cryptocrystalline aggregate (nanogranitoid). Since the first paper on melt inclusions in the granulites of the Kerala Khondalite Belt in 2009, reported and studied occurrences are already a few tens. Melt inclusions in migmatites and granulites show many analogies with their more common and long studied counterparts in igneous rocks, but also display very important differences and peculiarities, which are the subject of this review. Microstructurally, melt inclusions in anatectic rocks are small, commonly 10 μm in diameter, and their main mineral host is peritectic garnet, although several other hosts have been observed. Inclusion contents vary from glass in enclaves that were cooled very rapidly from supersolidus temperatures, to completely crystallized material in slowly cooled regional migmatites. The chemical composition of the inclusions can be analyzed combining several techniques (SEM, EMP, NanoSIMS, LA-ICP-MS), but in the case of crystallized inclusions the experimental remelting under confining pressure in a piston cylinder is a prerequisite. The melt is generally granitic and peraluminous, although granodioritic to trondhjemitic compositions have also been found. Being mostly primary in origin, inclusions attest for the growth of their peritectic host in the presence of melt. As a consequence, the inclusions have the unique ability of preserving information on the composition of primary anatectic crustal melts, before they undergo any of the common following changes in their way to produce crustal magmas

  7. Deep mixing of mantle melts beneath continental flood basalt provinces: Constraints from olivine-hosted melt inclusions in primitive magmas

    OpenAIRE

    Jennings, ES; Gibson, Sally Anne; Maclennan, John Campbell; Heinonen, JS

    2016-01-01

    We present major and trace element compositions of 154 re-homogenised olivine-hosted melt inclusions found in primitive rocks (picrites and ferropicrites) from the Mesozoic Paraná–Etendeka and Karoo Continental Flood Basalt (CFB) provinces. The major element compositions of the melt inclusions, especially their Fe/Mg ratios, are variable and erratic, and attributed to the re-homogenisation process during sample preparation. In contrast, the trace element compositions of both the picrite and f...

  8. Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting.

    Science.gov (United States)

    Zheng, Zeng; Wang, Lianfeng; Jia, Min; Cheng, Lingyu; Yan, Biao

    2017-02-01

    Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO3) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320-722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO3 composites can be a potential biomedical metallic materials in the medical field. Copyright © 2016. Published by Elsevier B.V.

  9. Immiscible silicate liquids at high pressure: the influence of melt structure on elemental partitioning

    Energy Technology Data Exchange (ETDEWEB)

    Vicenzi, E. [Princeton Materials Laboratory, Princeton, NJ (United States); Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia); Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    Micro-PIXE analyses have been applied to study partitioning of trace elements between immiscible silicate melts stabilised at 0.5 and 1.0 GPa over a temperature range of 1160-1240 deg C in the system SiO{sub 2}-FeO-Al{sub 2}0{sub 3}-K{sub 2}0 (+P{sub 2}0{sub 5}). The system was doped with a suite of trace elements of geochemical interest: Rb, Ba, Pb, Sr, La, Ce, Sm, Ho, Y, Lu, Th, U, Zr, Hf, Nb and Ta at approximately 200 ppm level for all elements except for the REE`s, Ba and Ta (600-1200 ppm). Trace element partitioning was found to be a complex function of cation field strength (charge/radius{sup 2}). Although field strength is important in determining the nature and degree of partitioning, the authors emphasised that it is only one component of the underlying mechanism for the way in which elements distribute themselves between two silicate liquids. 8 refs., 2 figs.

  10. The role of liquid-liquid immiscibility and crystal fractionation in the genesis of carbonatite magmas: insights from Kerimasi melt inclusions

    Science.gov (United States)

    Guzmics, Tibor; Zajacz, Zoltán; Mitchell, Roger H.; Szabó, Csaba; Wälle, Markus

    2015-02-01

    We have reconstructed the compositional evolution of the silicate and carbonate melt, and various crystalline phases in the subvolcanic reservoir of Kerimasi Volcano in the East African Rift. Trace element concentrations of silicate and carbonate melt inclusions trapped in nepheline, apatite and magnetite from plutonic afrikandite (clinopyroxene-nepheline-perovskite-magnetite-melilite rock) and calciocarbonatite (calcite-apatite-magnetite-perovskite-monticellite-phlogopite rock) show that liquid immiscibility occurred during the generation of carbonatite magmas from a CO2-rich melilite-nephelinite magma formed at relatively high temperatures (1,100 °C). This carbonatite magma is notably more calcic and less alkaline than that occurring at Oldoinyo Lengai. The CaO-rich (32-41 wt%) nature and alkali-"poor" (at least 7-10 wt% Na2O + K2O) nature of these high-temperature (>1,000 °C) carbonate melts result from strong partitioning of Ca (relative to Mg, Fe and Mn) in the immiscible carbonate and the CaO-rich nature (12-17 wt%) of its silicate parent (e.g., melilite-nephelinite). Evolution of the Kerimasi carbonate magma can result in the formation of natrocarbonatite melts with similar composition to those of Oldoinyo Lengai, but with pronounced depletion in REE and HFSE elements. We suggest that this compositional difference results from the different initial parental magmas, e.g., melilite-nephelinite at Kerimasi and a nephelinite at Oldoinyo Lengai. The difference in parental magma composition led to a significant difference in the fractionating mineral phase assemblage and the element partitioning systematics upon silicate-carbonate melt immiscibility. LA-ICP-MS analysis of coeval silicate and carbonate melt inclusions provides an opportunity to infer carbonate melt/silicate melt partition coefficients for a wide range of elements. These data show that Li, Na, Pb, Ca, Sr, Ba, B, all REE (except Sc), U, V, Nb, Ta, P, Mo, W and S are partitioned into the carbonate

  11. Deep mixing of mantle melts beneath continental flood basalt provinces: Constraints from olivine-hosted melt inclusions in primitive magmas

    Science.gov (United States)

    Jennings, Eleanor S.; Gibson, Sally A.; Maclennan, John; Heinonen, Jussi S.

    2017-01-01

    We present major and trace element compositions of 154 re-homogenised olivine-hosted melt inclusions found in primitive rocks (picrites and ferropicrites) from the Mesozoic Paraná-Etendeka and Karoo Continental Flood Basalt (CFB) provinces. The major element compositions of the melt inclusions, especially their Fe/Mg ratios, are variable and erratic, and attributed to the re-homogenisation process during sample preparation. In contrast, the trace element compositions of both the picrite and ferropicrite olivine-hosted melt inclusions are remarkably uniform and closely reflect those of the host whole-rocks, except in a small subset affected by hydrothermal alteration. The Paraná-Etendeka picrites and ferropicrites are petrogenetically related to the more evolved and voluminous flood basalts, and so we propose that compositional homogeneity at the melt inclusion scale implies that the CFB parental mantle melts were well mixed prior to extensive crystallisation. The incompatible trace element homogeneity of olivine-hosted melt inclusions in Paraná-Etendeka and Karoo primitive magmatic rocks has also been identified in other CFB provinces and contrasts with findings from studies of basalts from mid-ocean ridges (e.g. Iceland and FAMOUS on the Mid Atlantic Ridge), where heterogeneity of incompatible trace elements in olivine-hosted melt inclusions is more pronounced. We suggest that the low variability in incompatible trace element contents of olivine-hosted melt inclusions in near-primitive CFB rocks, and also ocean island basalts associated with moderately thick lithosphere (e.g. Hawaii, Galápagos, Samoa), may reflect mixing along their longer transport pathways during ascent and/or a temperature contrast between the liquidus and the liquid when it arrives in the crust. These thermal paths promote mixing of mantle melts prior to their entrapment by growing olivine crystals in crustal magma chambers. Olivine-hosted melt inclusions of ferropicrites from the Paran

  12. The solubility of carbon monoxide in silicate melts at high pressures and its effect on silicate phase relations. [in terrestrial and other planetary interiors

    Science.gov (United States)

    Eggler, D. H.; Mysen, B. O.; Hoering, T. C.; Holloway, J. R.

    1979-01-01

    Autoradiographic analysis and gas chromatography were used to measure the solubility in silicate melts of CO-CO2 vapors (30 to 40% CO by thermodynamic calculation) in equilibrium with graphite at temperatures up to 1700 deg C and pressures to 30 kbar. At near-liquidus temperatures CO-CO2 vapors were found to be slightly more soluble than CO2 alone. As a result of the apparently negative temperature dependence of CO solubility, the solubility of CO-CO2 at superliquidus temperatures is less than that of CO2. Melting points of two silicates were depressed more by CO than by CO2. Phase boundary orientations suggest that CO/CO + CO2 is greater in the liquid than in the vapor. The effect of the presence of CO on periodotite phase relations was investigated, and it was found that melts containing both CO and CO2 are nearly as polymerized as those containing only CO2. These results suggest that crystallization processes in planetary interiors can be expected to be about the same, whether the melts contain CO2 alone or CO2 and CO.

  13. Anionic Pt in Silicate Melts at Low Oxygen Fugacity: Speciation, Partitioning and Implications for Core Formation Processes on Asteroids

    Science.gov (United States)

    Medard, E.; Martin, A. M.; Righter, K.; Malouta, A.; Lee, C.-T.

    2017-01-01

    Most siderophile element concentrations in planetary mantles can be explained by metal/ silicate equilibration at high temperature and pressure during core formation. Highly siderophile elements (HSE = Au, Re, and the Pt-group elements), however, usually have higher mantle abundances than predicted by partitioning models, suggesting that their concentrations have been set by late accretion of material that did not equilibrate with the core. The partitioning of HSE at the low oxygen fugacities relevant for core formation is however poorly constrained due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variables like temperature, pressure, and oxygen fugacity. To better understand the relative roles of metal/silicate partitioning and late accretion, we performed a self-consistent set of experiments that parameterizes the influence of oxygen fugacity, temperature and melt composition on the partitioning of Pt, one of the HSE, between metal and silicate melts. The major outcome of this project is the fact that Pt dissolves in an anionic form in silicate melts, causing a dependence of partitioning on oxygen fugacity opposite to that reported in previous studies.

  14. Petrogenesis of arc lavas from the Rucu Pichincha and Pan de Azucar volcanoes (Ecuadorian arc): Major, trace element, and boron isotope evidences from olivine-hosted melt inclusions

    Science.gov (United States)

    Le Voyer, Marion; Rose-Koga, Estelle F.; Laubier, Muriel; Schiano, Pierre

    2008-12-01

    Primary melt inclusions in olivine phenocrysts (Fo74-89) of basic lavas from Pichincha and Pan de Azucar volcanoes (in the front and rear arcs of the Ecuadorian Andes, respectively) were analyzed by electron microprobe for major elements and by ion microprobe for trace element and boron isotope compositions. Although melt inclusions in the most magnesium-rich olivines contain relatively primitive magmas, their compositions are not directly linked to those of the whole rocks through a differentiation scheme. They are characterized by nepheline-normative compositions with low SiO2 contents (39.8-47.9 wt%) and unusually high CaO contents (up to 15.4 wt%), which cannot be derived from melting of a simple peridotitic mantle. We explain their formation by the presence of amphibole-bearing olivine-clinopyroxenites in the source of these melts. The trace elements patterns of the melt inclusions show the typical trace element features of arc magmas, such as enrichment in LILE and LREE, and negative anomalies in Nb and Ti. Across-arc variations of mobile versus less mobile incompatible element ratios indicate a decreasing input of a mobile phase from the slab to the mantle wedge with the distance to the trench, along with a decrease in the degree of melting. Boron isotope compositions are highly variable within each volcano (δ11B from -9.5 ± 1.3‰ to +3.5 ± 1.4‰ for the Pichincha melt inclusions and from -17.9 ± 0.8‰ to -1.9 ± 1.4‰ for the Pan de Azucar melt inclusions) and suggest trapping of isotopically heterogeneous melts. Modeling of both dehydration and fusion of the slab indicates that the Pichincha melt inclusions were formed by melting a source enriched by the addition of 1% of a heterogeneous aqueous fluid derived from the dehydration of both the sediments and the altered oceanic crust (after 74 and 76% of B loss, respectively). The phase that metasomatizes the source of the Pan de Azucar melt inclusions can be either an input of 0.1% of a heterogeneous

  15. The influence of the cooling rate of a 2PbO . SiO2 melt on the constitution of silicate anions

    OpenAIRE

    Götz, J; Hoebbel, Dagobert; Wieker, Wolfgang

    1980-01-01

    The kinetics of crystallization in a 2Pbo · SiO2 melt have been investigated. A TTT-diagram was constructed, which describes the kinetic parameters for the formation of crystalline phases in the system. By means of silicate anion analysis the relationship between the cooling rates of the melt and the structure of silicate units in solid 2PbO · SiO2 has been studied. Substantial differences in the thermal treatment of the melt lead to alterations of the silicate anion constitution, which cause...

  16. Chromite-rich mafic silicate chondrules in ordinary chondrites: Formation by impact melting

    Science.gov (United States)

    Krot, Alexander N.; Rubin, Alan E.

    1993-01-01

    Chromium-rich chondrules constitute less than 0.1 percent of all ordinary chondrite (OC) chondrules and comprise three groups: chromian-spinel chondrules, chromian-spinel inclusions, and chromite-rich mafic silicate (CRMS) chondrules. Chromian-spinel chondrules (typically 100-300 microns in apparent diameter) exhibit granular, porphyritic and unusual textures and occur mainly in H chondrites. Their morphologies are distinct from the irregularly shaped chromian-spinel inclusions of similar mineralogy. Chromian-spinel chondrules and inclusions consist of grains of chromian-spinel embedded in plagioclase (Pl) or mesostasis of Pl composition. Many also contain accessory ilmenite (Ilm), high-Ca pyroxene (Px), merrillite (Mer), and rare olivine (Ol); some exhibit concentric mineral and chemical zoning. CRMS chondrules (300-1100 microns in apparent diameter) are generally larger than chromian-spinel chondrules and occur in all metamorphosed OC groups. Most CRMS chondrules are nearly spherical although a few are ellipsoidal with a/b aspect ratios ranging up to 1.7. Textures include cryptocrystalline, granular, radial, barred, and porphyritic varieties; some contain apparently relict grains. The chondrules consist of chromite (Chr), Ol and Pl, along with accessory Mer, troilite (Tr), metallic Fe-Ni (Met), Px and Ilm. The mesostasis in CRMS chondrules is nearly opaque in transmitted light; thus, they can be easily recognized in the optical microscope. Based on the similarity of mineralogy and chemistry between CRMS chondrules of different textures (opaque chromite-rich mesostasis, skeletal morphology of Ol grains, similar bulk compositions) we suggest that these chondrules form a genetically related population.

  17. Fractional crystallization of olivine melt inclusion in shock-induced chondritic melt vein

    Science.gov (United States)

    Miyahara, M.; El Goresy, A.; Ohtani, E.; Kimura, M.; Ozawa, S.; Nagase, T.; Nishijima, M.

    2009-12-01

    The formation of ringwoodite, wadsleyite and majorite from their parental low-pressure polymorphs in melt veins in chondritic meteorites is usually interpreted to be the result of shock-induced solid-state phase transformation. Formation and survival of individual mineral melt enclaves in the chondritic high-pressure melt was not considered a viable possibility. We report evidence for melting of individual large olivine fragments entrained in melt veins, their survival as melt enclaves in the chondritic melts and their subsequent fractional crystallization at high-pressures and temperatures. The fractionally crystallized olivine melt enclaves appear to be ubiquitous in chondrites. In contrast, Ca-poor pyroxene fragments in the same veins and Ca-poor pyroxene in chondrules entrained do not show any sign of melting. Texture and compositions of olivine fragments are indicative of fractional crystallization from individual olivine melts alone. Fragments of original unzoned olivine (Fa 24-26) melted, and melts subsequently fractionally crystallized to Mg-rich wadsleyite (Fa 6-10) and Mg-poor ringwoodite (Fa 28-33) with a compositional gap of ≤26 mol% fayalite. In contrast, compositions of ringwoodite and wadsleyite that emerged from solid-sate phase transformations are identical to that of parental olivine thus erasing any source of enigma. The olivine monomineralic melts barely show any signs of mixing with the chondritic liquid prior to or during their individual fractional crystallization. Our findings demonstrate that the formation of high-pressure minerals during shock events in asteroids also results from melting and fractional crystallization from some individual mineral melts that barely mixed with the chondritic melt host, a mechanism previously not recognized or accepted.

  18. The solubility of iridium in silicate melts: New data from experiments with Ir 10Pt 90 alloys

    Science.gov (United States)

    Borisov, A.; Palme, H.

    1995-02-01

    Solubilities of Ir in silicate melts of anorthite-diopside eutectic composition were determined by equilibrating IrPt-loops with silicates at a wide range of oxygen fugacities, from air to about 1.7 log units below the iron-wdstite buffer (IW-1.7) at 1300 and 1480°C. Instead of pure Ir metal, Ir 10Pt 90-alloys were used to avoid formation of tiny Ir nuggets in the silicate glass. Although nugget formation was less severe than in experiments with pure Ir metal, some samples were still contaminated as indicated by sporadically high Ir contents. These samples were subdivided and the separates were analysed again. Samples with high Ir were eliminated. The procedure was repeated several times until compositional uniformity of subsamples was achieved. In a log (Ir solubility) vs. log (F O 2)-diagram the most reliable data plot along a line with a slope of about 1/4 suggesting Ir 1+ as the formal Ir species in the melt, similar to earlier findings for Pd. The Ir solubility was found to be temperature independent within the range of temperatures used in the present experiments. The results with Ir 10Pt 90-alloys were recalculated to solubilities for pure Ir metal. These solubilities are significantly lower than earlier data (e.g., 1.52 ppb at IW-1 and 1478°C). As a result, calculated metal/silicate melt partition coefficients are extremely high (10 8-10 12 at an oxygen fugacity corresponding to IW-2). Because of the uncertainty introduced by the presence of Ir nuggets it cannot be completely excluded that some of the solubility data are upper limits only. This would, however, only increase Ir metal/silicate partition coefficients and thus make arguments against a global core-mantle equilibrium stronger.

  19. Mantle-derived trace element variability in olivines and their melt inclusions

    Science.gov (United States)

    Neave, David A.; Shorttle, Oliver; Oeser, Martin; Weyer, Stefan; Kobayashi, Katsura

    2018-02-01

    Trace element variability in oceanic basalts is commonly used to constrain the physics of mantle melting and the chemistry of Earth's deep interior. However, the geochemical properties of mantle melts are often overprinted by mixing and crystallisation processes during ascent and storage. Studying primitive melt inclusions offers one solution to this problem, but the fidelity of the melt-inclusion archive to bulk magma chemistry has been repeatedly questioned. To provide a novel check of the melt inclusion record, we present new major and trace element analyses from olivine macrocrysts in the products of two geographically proximal, yet compositionally distinct, primitive eruptions from the Reykjanes Peninsula of Iceland. By combining these macrocryst analyses with new and published melt inclusion analyses we demonstrate that olivines have similar patterns of incompatible trace element (ITE) variability to the inclusions they host, capturing chemical systematics on intra- and inter-eruption scales. ITE variability (element concentrations, ratios, variances and variance ratios) in olivines from the ITE-enriched Stapafell eruption is best accounted for by olivine-dominated fractional crystallisation. In contrast, ITE variability in olivines and inclusions from the ITE-depleted Háleyjabunga eruption cannot be explained by crystallisation alone, and must have originated in the mantle. Compatible trace element (CTE) variability is best described by crystallisation processes in both eruptions. Modest correlations between host and inclusion ITE contents in samples from Háleyjabunga suggest that melt inclusions can be faithful archives of melting and magmatic processes. It also indicates that degrees of ITE enrichment can be estimated from olivines directly when melt inclusion and matrix glass records of geochemical variability are poor or absent. Inter-eruption differences in olivine ITE systematics between Stapafell and Háleyjabunga mirror differences in melt

  20. Bubble formation and decrepitation control the CO2 content of olivine-hosted melt inclusions

    Science.gov (United States)

    Maclennan, J.

    2017-02-01

    The CO2 contents of olivine-hosted melt inclusions have previously been used to constrain the depth of magma chambers in basaltic systems. However, the vast majority of inclusions have CO2 contents which imply entrapment pressures that are significantly lower than those obtained from independent petrological barometers. Furthermore, a global database of melt inclusion compositions from low H2O settings, indicates that the distribution of saturation pressures varies surprisingly little between mid-ocean ridges, ocean islands, and continental rift zones. 95% of the inclusions in the database have saturation pressures of 200 MPa or less, indicating that melt inclusion CO2 does not generally provide an accurate estimate of magma chamber depths. A model of the P-V-T-X evolution of olivine-hosted melt inclusions was developed so that the properties of the inclusion system could be tracked as the hosts follow a model P-T path. The models indicate that the principal control on the saturation of CO2 in the inclusion and the formation of vapor bubbles is the effect of postentrapment crystallization on the major element composition of the inclusions and how this translates into variation in CO2 solubility. The pressure difference between external melt and the inclusion is likely to be sufficiently high to cause decrepitation of inclusions in most settings. Decrepitation can account for the apparent mismatch between CO2-based barometry and other petrological barometers, and can also account for the observed global distribution of saturation pressures. Only when substantial postentrapment crystallization occurs can reconstructed inclusion compositions provide an accurate estimate of magma chamber depth.

  1. Melt-inclusion-hosted excess 40Ar in quartz crystals of the Bishop and Bandelier magma systems

    Science.gov (United States)

    Winick, J.A.; McIntosh, W.C.; Dunbar, N.W.

    2001-01-01

    40Ar/39Ar experiments on melt-inclusion-bearing quartz (MIBQ) from the Bishop and Bandelier Tuff Plinian deposits indicate high concentrations of excess 40Ar in melt inclusions. Two rhyolite glass melt inclusion populations are present in quartz; exposed melt inclusions and trapped melt inclusions. Air-abrasion mill grinding and hydrofluoric acid treatments progressively remove exposed melt inclusions while leaving trapped melt inclusions unaffected. Laser step-heating of MIBQ yields increasing apparent ages as a function of exposed melt inclusion removal, reflecting the higher nonatmospheric 40Ar concentrations hosted in trapped melt inclusions. Exposed melt inclusion-free MIBQ from the Bishop, Upper Bandelier, and Lower Bandelier Tufts yield total-gas ages of 3.70 ?? 1.00 Ma, 11.54 ?? 0.87 Ma, and 14.60 ?? 1.50 Ma, respectively. We interpret these old apparent ages as compelling evidence for the presence of excess 40Ar in MIBQ. Trapped melt inclusions in sanidine phenocrysts may contain excess 40Ar concentrations similar to those in MIBQ. This excess 40Ar has the potential to increase single-crystal laser-fusion ages of sanidine by tens of thousands of years, relative to the actual eruption age.

  2. Trace element partitioning between ilmenite, armalcolite and anhydrous silicate melt: Implications for the formation of lunar high-Ti mare basalts

    NARCIS (Netherlands)

    van Kan, M.; Mason, P.R.D.; van Westrenen, W.

    2011-01-01

    We performed a series of experiments at high pressures and temperatures to determine the partitioning of a wide range of trace elements between ilmenite (Ilm), armalcolite (Arm) and anhydrous lunar silicate melt, to constrain geochemical models of the formation of titanium-rich melts in the Moon.

  3. A melt inclusion study of the Sudbury Igneous Complex (Ontario, Canada): preliminary results

    Science.gov (United States)

    Watts, Kathleen; Hanley, Jacob; Kontak, Daniel; Ames, Doreen

    2013-04-01

    The 1.85 Ga Sudbury Igneous Complex (SIC), Ontario, Canada, is an intrusive complex representing the crystallized melt sheet that formed within a large impact crater. The SIC has been extensively studied due to its rich endowment in magmatic sulfide ores (Ni-Cu-PGEs). The nature and origin of the SIC melt sheet and its subsequent evolution still remain controversial. In this study, analyses of primary melt inclusions hosted in cumulus apatite within three mafic units of the SIC (gabbro, norite and sublayer quartz diorite) are used to decipher the thermometric and chemical characteristics of the evolving melt sheet as it crystallized. Apatite-hosted melt inclusions commonly display a negative crystal shape, occur parallel to the c-axis, and often occur within a central growth zone, which suggest a primary origin. The compositions of coeval (co-entrapped) melt inclusions are distinct and may represent either the products of immiscibility (low or high temperature field; c.f. the Skaergaard Intrusion: Jakobsen et al., Geology, 2005), or a product of early, high-temperature, impact-generated emulsification (prior to and independent of crystallization of the melt sheet). The compositions of homogenized (1100-1200oC for 3 hrs) melt inclusions, determined by SEM-EDS and EMP analyses of opened, homogenized melt inclusions, equate to two distinct compositions: (1) Type-I are SiO2-rich, ranging from tonalitic to granodioritic in composition (60-70 wt% SiO2, up to 11 wt% FeO); and (2) Type-II are Fe-rich with syenogabbroic to essexitic to alkali gabbroic compositions (27-49 wt% SiO2, 16-44 wt% FeO). Trace element data, obtained by LA-ICPMS analyses of single inclusions and surrounding host apatite, are used to infer D values between apatite and the two melt types, and between the coexisting melt types. Apparent Dap-melt values for both Type-I and Type-II inclusions show that the REE, Sr, and Y are compatible in apatite, and As is weakly compatible or incompatible in apatite

  4. Metal/sulfide-silicate intergrowth textures in EL3 meteorites: Origin by impact melting on the EL parent body

    Science.gov (United States)

    van Niekerk, Deon; Keil, Klaus

    2011-10-01

    We document the petrographic setting and textures of Fe,Ni metal, the mineralogy of metallic assemblages, and the modal mineral abundances in the EL3 meteorites Asuka (A-) 881314, A-882067, Allan Hills 85119, Elephant Moraine (EET) 90299/EET 90992, LaPaz Icefield 03930, MacAlpine Hills (MAC) 02635, MAC 02837/MAC 02839, MAC 88136, Northwest Africa (NWA) 3132, Pecora Escarpment 91020, Queen Alexandra Range (QUE) 93351/QUE 94321, QUE 94594, and higher petrologic type ELs Dar al Gani 1031 (EL4), Sayh al Uhaymir 188 (EL4), MAC 02747 (EL4), QUE 94368 (EL4), and NWA 1222 (EL5). Large metal assemblages (often containing schreibersite and graphite) only occur outside chondrules and are usually intergrown with silicate minerals (euhedral to subhedral enstatite, silica, and feldspar). Sulfides (troilite, daubréelite, and keilite) are also sometimes intergrown with silicates. Numerous authors have shown that metal in enstatite chondrites that are interpreted to have been impact melted contains euhedral crystals of enstatite. We argue that the metal/sulfide-silicate intergrowths in the ELs we studied were also formed during impact melting and that metal in EL3s thus does not retain primitive (i.e., nebular) textures. Likewise, the EL4s are also impact-melt breccias. Modal abundances of metal in the EL3s and EL4s range from approximately 7 to 30 wt%. These abundances overlap or exceed those of EL6s, and this is consistent either with pre-existing heterogeneity in the parent body or with redistribution of metal during impact processes.

  5. Olivine-hosted melt inclusions as an archive of redox heterogeneity in magmatic systems

    Science.gov (United States)

    Hartley, Margaret E.; Shorttle, Oliver; Maclennan, John; Moussallam, Yves; Edmonds, Marie

    2017-12-01

    The redox state of volcanic products determines their leverage on the oxidation of Earth's oceans and atmosphere, providing a long-term feedback on oxygen accumulation at the planet's surface. An archive of redox conditions in volcanic plumbing systems from a magma's mantle source, through crustal storage, to eruption, is carried in pockets of melt trapped within crystals. While melt inclusions have long been exploited for their capacity to retain information on a magma's history, their permeability to fast-diffusing elements such as hydrogen is now well documented and their retention of initial oxygen fugacities (fO2) could be similarly diffusion-limited. To test this, we have measured Fe3+/ΣFe by micro-XANES spectroscopy in a suite of 65 olivine-hosted melt inclusions and 9 matrix glasses from the AD 1783 Laki eruption, Iceland. This eruption experienced pre-eruptive mixing of chemically diverse magmas, syn-eruptive degassing at the vent, and post-eruptive degassing during lava flow up to 60 km over land, providing an ideal test of whether changes in the fO2 of a magma may be communicated through to its cargo of crystal-hosted melt inclusions. Melt inclusions from rapidly quenched tephra samples have Fe3+/ΣFe of 0.206 ± 0.008 (ΔQFM of +0.7 ± 0.1), with no correlation between their fO2 and degree of trace element enrichment or differentiation. These inclusions preserve the redox conditions of the mixed pre-eruptive Laki magma. When corrected for fractional crystallisation to 10 wt.% MgO, these inclusions record a parental magma [Fe3+/ΣFe](10) of 0.18 (ΔQFM of +0.4), significantly more oxidised than the Fe3+/ΣFe of 0.10 that is often assumed for Icelandic basalt magmas. Melt inclusions from quenched lava selvages are more reduced than those from the tephra, having Fe3+/ΣFe between 0.133 and 0.177 (ΔQFM from -0.4 to +0.4). These inclusions have approached equilibrium with their carrier lava, which has been reduced by sulfur degassing. The progressive re

  6. Coordinated Hard Sphere Mixture (CHaSM): A fast approximate model for oxide and silicate melts at extreme conditions

    Science.gov (United States)

    Wolf, A. S.; Asimow, P. D.; Stevenson, D. J.

    2015-12-01

    Recent first-principles calculations (e.g. Stixrude, 2009; de Koker, 2013), shock-wave experiments (Mosenfelder, 2009), and diamond-anvil cell investigations (Sanloup, 2013) indicate that silicate melts undergo complex structural evolution at high pressure. The observed increase in cation-coordination (e.g. Karki, 2006; 2007) induces higher compressibilities and lower adiabatic thermal gradients in melts as compared with their solid counterparts. These properties are crucial for understanding the evolution of impact-generated magma oceans, which are dominated by the poorly understood behavior of silicates at mantle pressures and temperatures (e.g. Stixrude et al. 2009). Probing these conditions is difficult for both theory and experiment, especially given the large compositional space (MgO-SiO2-FeO-Al2O3-etc). We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme P-T conditions (Wolf et al., 2015). The Coordinated Hard Sphere Mixture (CHaSM) extends the Hard Sphere mixture model, accounting for the range of coordination states for each cation in the liquid. Using approximate analytic expressions for the hard sphere model, this fast statistical method compliments classical and first-principles methods, providing accurate thermodynamic and structural property predictions for melts. This framework is applied to the MgO system, where model parameters are trained on a collection of crystal polymorphs, producing realistic predictions of coordination evolution and the equation of state of MgO melt over a wide P-T range. Typical Mg-coordination numbers are predicted to evolve continuously from 5.25 (0 GPa) to 8.5 (250 GPa), comparing favorably with first-principles Molecular Dynamics (MD) simulations. We begin extending the model to a simplified mantle chemistry using empirical potentials (generally accurate over moderate pressure ranges, consuming classical MD calculations. This approach also sheds light on the universality

  7. Thermal and Magmatic Evolution of a Silicic Center: Melt Residence and Accumulation at Laguna del Maule, Chile

    Science.gov (United States)

    Dufek, J.; Andersen, N. L.; Singer, B. S.

    2016-12-01

    The assembly of large silicic magmatic centers encompasses processes that span many time and length scales from the initial processes of mantle melting and extraction, to the transport, interaction, differentiation, and residence in the crust. These magmatic systems are coupled to their crustal containers, exchanging mass and energy, and responding to evolving tectonic conditions and crustal lithologies. In this work, we use multiscale numerical models in conjunction with recent information from the on-going geophysical and geochemical investigation of one large silicic center, Laguna del Maule (Chile), to examine the response of the crust to sustained input of magmas from the mantle. The Laguna del Maule (LdM) volcanic field in Chile has been one of the most active rhyolitic centers following deglaciation, and this part of the arc has likely been active for 25 MY (Hildreth et al, 2010). Laguna del Maule has attracted recent attention as the locus of some of the largest sustained deformation signals at a volcano that is not currently erupting, with deformation rates exceeding 20 cm/yr since 2007 (Le Mevel et al, 2015). The area is also a site of active geothermal energy exploration. In this work we use two primary models to examine the evolution of the Laguna del Maule system. We use a combined magmatic-tectonic model modified from (Dufek and Bergantz, 2005; Karakas and Dufek, 2015) to examine the long-term history of the melt in the crust, including melt residence time and the spatio-temporal relationship of melt in the crust. In particular we examine the development of a substantial lower crustal magma body in addition to an upper crustal reservoir of silicic magmas. In these simulations we infer the evolving thermal anomaly and melt volume in the crust as well as describe geochemical trends, chronometers (Zr saturation) and physical properties such as density and predicted seismic velocities. In order to evaluate more recent and resolved episodes of magmatism, a

  8. Trace Elements in Olivine in Italian Potassic Volcanic Rocks Distinguish Between Mantle Metasomatism by Carbonatitic and Silicate Melts

    Science.gov (United States)

    Foley, S. F.; Ammannati, E.; Jacob, D. E.; Avanzinelli, R.; Conticelli, S.

    2014-12-01

    material into the mantle wedge. Our data indicate opposite effects for metasomatism by silicate- and carbonate-rich melts, namely the removal and growth of olivine, respectively. This new line of evidence establishes olivine as a key tool to investigate the role of carbonatitic and silicate melts in the Earth's mantle.

  9. Energetics of silicate melts from thermal diffusion studies. Annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D.

    1992-07-01

    Efforts are reported in the following areas: laboratory equipment (multianvils for high P/T work, pressure media, SERC/DL sychrotron), liquid-state thermal diffusion (silicate liquids, O isotopic fractionation, volatiles, tektites, polymetallic sulfide liquids, carbonate liquids, aqueous sulfate solutions), and liquid-state isothermal diffusion (self-diffusion, basalt-rhyolite interdiffusion, selective contamination, chemical diffusion).

  10. Melt inclusion constraints on petrogenesis of the 2014-2015 Holuhraun eruption, Iceland

    Science.gov (United States)

    Hartley, Margaret E.; Bali, Enikö; Maclennan, John; Neave, David A.; Halldórsson, Sæmundur A.

    2018-02-01

    The 2014-2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine-plagioclase-augite-melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1 ± 0.7 kbar (7.5 ± 2.5 km), which is in agreement with the depths of earthquakes (6 ± 1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1-12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H2O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12-0.29 m s-1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.

  11. Redox dynamics in multicomponent, iron-bearing silicate melts and glasses: Application to the float-glass processing of high-temperature silicate glassmelts

    Science.gov (United States)

    Cook, Glen Bennett

    Processing high-strain-point glasses by the float process is challenged by the relative thermochemical properties of glassmelts and the liquid-metal float medium. As the chemical reaction between the glassmelt and the float metal involves dynamic reduction of the glassmelt, this research has examined the constraints on high-temperature float processing of glassmelts by combining metal-alloy/oxide reaction thermodynamics and Wagnerian kinetic models for redox reactions in silicate melts. The dynamic response of Fe-bearing, p-type (polaronic) semiconducting amorphous silicates to a chemical potential gradient of oxygen has been shown to be rate-limited by the chemical diffusion of network-modifying cations. The persistence of this mechanism to very low Fe concentrations in Fe-doped magnesium aluminosilicate glasses was proven with Rutherford backscattering spectroscopy. Three glasses, with 0.1, 0.5, and 1.25 mol. % FeO were reacted with air at temperatures from 710-845sp°C. For all compositions and temperatures, oxidation was dominated by network modifier diffusion; an activation energy of 475 kJ*molsp{-1} characterized the process. Chemical dynamics in a high-temperature float environment were characterized on liquid-liquid reaction couples between two low-Fe sodium-aluminoborosilicate (NABS) glassmelts (0.01 and 0.08 mol. % FeO) and Au-30Sn and Au-28Ge (atomic basis) alloys. Experiments were performed in the temperature range 1250-1450sp°C for 30 min; wavelength-dispersive and Rutherford backscattering spectroscopies were employed. These exothermic liquid-metal alloys display large negative deviations from ideal solution behavior, with significantly depressed chemical activities. Diffusion of Sn or Ge in the NABS glassmelts (depth and concentration) was limited at all temperatures to levels comparable to conventional soda-lime (NCS) float glass (˜2 min on pure Sn at 1100sp°C). Incorporation of Sn or Ge was reduced significantly in the higher-Fe-content NABS

  12. Hydrothermal Fluids, Nebular Vapors and Silicate MELTS As Seem through the Eyes of Minerals

    Science.gov (United States)

    Sack, R. O.

    2014-12-01

    Three cases where advances in mineral thermochemistry provide new insights into geological processes are discussed: (I) Sb-rich fahlores are used to constrain compositions of hydrothermal fluids and processes responsible for Ag-Pb-Zn sulfide ores from three Ag mining districts, Keno Hill, (Yukon, Canada); Julcani, (Angaraes, Peru); Coeur d'Alene, (Idaho, USA), confirming that the Ag initially contained in galena solid solutions was a substantial contributor to the total Ag mined in each of them; (II) Al8/3O4-rich MgAl2O4-Al8/3O4 spinels may have condensed from the primordial solar nebula, with their Al8/3O4 annealed out with cooling, as AgSbS2 is "annealed" out of galena in Ag-Pb-Zn ore deposits. Such spinels may explain inconsistencies between mineral condensation sequences recorded in Ca-Al-rich inclusions (CAIs) in carbonaceous chondrites and those calculated assuming spinel was MgAl2O4. A new thermodynamical model and corundum-bearing CAIs, suggest we may anticipate realization of higher temperatures and pressures of canonical condensation than currently in vogue; (III) Fassitic pyroxenes in the composition space CaMgSi2O6 (Di) - CaTiAlSiO6 (Gr) - CaTi1/2Mg1/2AlSiO6 (AlBf) - CaAl2SiO6 (CATS) exhibit at least one prominent gap evident in composition data from CAIs. This may be interpreted as due to the near superposition of the extension of the Di- AlBf gap into this fassaite tetrahedron, with an isolated two-phase region formed by the double intersections of the (Gr+CATS) - AlBf critical curve with the surfaces of constant Ti(Al)-1 exchange potential characteristic of CAIs. A thermodynamic model for fassaites may provide context for critical thinking about CAI petrogenesis, as well as presaging potential refinements to the thermochemical model for pyroxenes in MELTS.

  13. Partitioning of the Transition Metals Mn, Fe, Co, Ni and Zn between Orthopyroxene and Silicate Melt : Ionic Size Effect to the Partitioning Behavior

    OpenAIRE

    Hashizume, Hideo; Hariya, Yu

    1992-01-01

    Partition coefficients of Mn2+, Fe2+, CO2+, Ni2+, and Zn2+ between orthopyroxene and silicate melt have been determined in the system Mg2SiO4-SiO2-H2O at pressures of 1 and 3 GPa and at a temperature of 1400℃. The partition coefficient was defined by the ratio of the concentration of an element in orthopyroxene to that of the element in silicate melt. Partition coefficients were plotted on a partition coefficient versus ionic radius (PC-IR) diagram. Partition coefficients were linearly relate...

  14. Pre-eruptive volatile content, melt-inclusion chemistry, and microthermometry of interplinian Vesuvius lavas (pre-AD 1631)

    Science.gov (United States)

    Belkin, H.E.; de Vivo, B.; Torok, K.; Webster, J.D.

    1998-01-01

    Silicate-melt inclusions from lavas and pyroclastics from a selected suite of pre-A.D. 1631 interplinian Mt. Somma-Vesuvius lavas and scoria have been experimentally homogeneized and studied by microthermometry, electron microprobe (EMPA) and secondary-ion mass spectrometry (SIMS) to examine pre-eruptive volatile content and magma evolution. The melt inclusions have a bubble about 0.06% their volume, uncommonly contain non-condensable gas but do not contain any dense fluid phases. Clinopyroxene-hosted inclusions yield homogenization temperatures (Th) from 1170 to 1260??C, most between 1220 and 1240??C; plagiclase-hosted inclusions have Th from 1210 to 1230??C; these values are typical for the Vesuvius environment. The dominant factor controlling major element variability in the inclusions is clinopyroxene fractionation; MgO varies from 5 to 3 wt%, SiO2 varies from 60 to 48 wt%. total alkalis vary from 15 to 4 wt%, and CaO varies from 13 to 5 wt%. H2O varies from 2.7 to 0.6 wt% and is decoupled from incompatible element evolution suggesting vapor saturation during trapping. Chlorine and F vary from 1.- wt% to 0 and 0.63 to 0 wt%, respectively. Bulk rock and limited matrix glass analyses show that the lavas lost about half of their F and Cl content except for the A.D. 472-1631 lava which contains similar Cl abundances as the bulk rock. SO3 varies from 0.5 to 0 wt% and compared with matrix glass and bulk rock demonstrate that the lavas have lost essentially all sulfur. The samples can be classified into three age groups, ??? 25 000 yr B.P., 25 000-17 000 yr B.P., and A.D. 472-1631. There is a systematic increase in some components, e.g., total alkalis, SO3, Cl, Li, B, and Sr with the youth of the sample and a decrease in others, e.g., Zr and Y. However, on average these samples seem less evolved than later A.D. 1631-1944 lavas.

  15. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    Science.gov (United States)

    Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

    2016-01-01

    Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.

  16. The solvation radius of silicate melts based on the solubility of noble gases and scaled particle theory.

    Science.gov (United States)

    Ottonello, Giulio; Richet, Pascal

    2014-01-28

    The existing solubility data on noble gases in high-temperature silicate melts have been analyzed in terms of Scaling Particle Theory coupled with an ab initio assessment of the electronic, dispersive, and repulsive energy terms based on the Polarized Continuum Model (PCM). After a preliminary analysis of the role of the contracted Gaussian basis sets and theory level in reproducing appropriate static dipole polarizabilities in a vacuum, we have shown that the procedure returns Henry's law constants consistent with the values experimentally observed in water and benzene at T = 25 °C and P = 1 bar for the first four elements of the series. The static dielectric constant (ɛ) of the investigated silicate melts and its optical counterpart (ɛ(∞)) were then resolved through the application of a modified form of the Clausius-Mossotti relation. Argon has been adopted as a probe to depict its high-T solubility in melts through an appropriate choice of the solvent diameter σs, along the guidelines already used in the past for simple media such as water or benzene. The σs obtained was consistent with a simple functional form based on the molecular volume of the solvent. The solubility calculations were then extended to He, Ne, and Kr, whose dispersive and repulsive coefficients are available from theory and we have shown that their ab initio Henry's constants at high T reproduce the observed increase with the static polarizability of the series element with reasonable accuracy. At room temperature (T = 25 °C) the calculated Henry's constants of He, Ne, Ar, and Kr in the various silicate media predict higher solubilities than simple extrapolations (i.e., Arrhenius plots) based on high-T experiments and give rise to smooth trends not appreciably affected by the static polarizabilities of the solutes. The present investigation opens new perspectives on a wider application of PCM theory which can be extended to materials of great industrial interest at the core of

  17. The solvation radius of silicate melts based on the solubility of noble gases and scaled particle theory

    Science.gov (United States)

    Ottonello, Giulio; Richet, Pascal

    2014-01-01

    The existing solubility data on noble gases in high-temperature silicate melts have been analyzed in terms of Scaling Particle Theory coupled with an ab initio assessment of the electronic, dispersive, and repulsive energy terms based on the Polarized Continuum Model (PCM). After a preliminary analysis of the role of the contracted Gaussian basis sets and theory level in reproducing appropriate static dipole polarizabilities in a vacuum, we have shown that the procedure returns Henry's law constants consistent with the values experimentally observed in water and benzene at T = 25 °C and P = 1 bar for the first four elements of the series. The static dielectric constant (ɛ) of the investigated silicate melts and its optical counterpart (ɛ∞) were then resolved through the application of a modified form of the Clausius-Mossotti relation. Argon has been adopted as a probe to depict its high-T solubility in melts through an appropriate choice of the solvent diameter σs, along the guidelines already used in the past for simple media such as water or benzene. The σs obtained was consistent with a simple functional form based on the molecular volume of the solvent. The solubility calculations were then extended to He, Ne, and Kr, whose dispersive and repulsive coefficients are available from theory and we have shown that their ab initio Henry's constants at high T reproduce the observed increase with the static polarizability of the series element with reasonable accuracy. At room temperature (T = 25 °C) the calculated Henry's constants of He, Ne, Ar, and Kr in the various silicate media predict higher solubilities than simple extrapolations (i.e., Arrhenius plots) based on high-T experiments and give rise to smooth trends not appreciably affected by the static polarizabilities of the solutes. The present investigation opens new perspectives on a wider application of PCM theory which can be extended to materials of great industrial interest at the core of

  18. Noble gas solubility in silicate melts:a review of experimentation and theory, and implications regarding magma degassing processes

    Directory of Open Access Journals (Sweden)

    A. Paonita

    2005-06-01

    Full Text Available Noble gas solubility in silicate melts and glasses has gained a crucial role in Earth Sciences investigations and in the studies of non-crystalline materials on a micro to a macro-scale. Due to their special geochemical features, noble gases are in fact ideal tracers of magma degassing. Their inert nature also allows them to be used to probe the structure of silicate melts. Owing to the development of modern high pressure and temperature technologies, a large number of experimental investigations have been performed on this subject in recent times. This paper reviews the related literature, and tries to define our present state of knowledge, the problems encountered in the experimental procedures and the theoretical questions which remain unresolved. Throughout the manuscript I will also try to show how the thermodynamic and structural interpretations of the growing experimental dataset are greatly improving our understanding of the dissolution mechanisms, although there are still several points under discussion. Our improved capability of predicting noble gas solubilities in conditions closer to those found in magma has allowed scientists to develop quantitative models of magma degassing, which provide constraints on a number of questions of geological impact. Despite these recent improvements, noble gas solubility in more complex systems involving the main volatiles in magmas, is poorly known and a lot of work must be done. Expertise from other fields would be extremely valuable to upcoming research, thus focus should be placed on the structural aspects and the practical and commercial interests of the study of noble gas solubility.

  19. Solubility and Partitioning of Carbon and Sulfur in Fe-rich Alloy and Silicate Melt Systems at High Pressures and Temperatures: Implications for Earth's Heterogeneous Accretion

    Science.gov (United States)

    Li, Y.; Dasgupta, R.; Tsuno, K.; Monteleone, B.; Shimizu, N.

    2015-12-01

    The partitioning of C and S between Fe-rich alloy and silicate melt are critical to understand the origin and distribution of these two volatile elements in terrestrial planets. Thirty-five experiments in graphite capsule have been performed at 2-8 GPa and 1600-2200 °C to investigate the effects of P, T, fO2, H2O, and melt composition on C and S partitioning in Fe-Ni±S±Si alloy and silicate melt systems. The results show that C-solubility in Si-free alloy melt is ~5.5 wt% and is little affected by P, T, or the presence of 0-5 wt.% S [1]. However, C-solubility in Si-bearing alloy decreases from ~5.5 to ~1.8 wt% with increasing Si content to 10 wt.%. C-solubility in silicate melt is mainly controlled by fO2 and the bulk H2O content. At fO2 from IW-0.6 to IW-1.5, C-solubility drops from ~90 to ~10 ppm. However, at fO2 below IW-1.5, C-solubility increases up to 240 ppm with decreasing fO2 if the melt H2O content is 0.3-0.8 wt.%; whereas C-solubility decreases or only slightly increases if melt H2O is IW-1 CO32- peak was undetectable in IR-spectra and a strong correlation between Raman peak intensities of H2 and CH4 was observed. varied from 130 to 4600 and is mainly controlled by fO2 and melt H2O content, as in the case for C-solubility in silicate melt but in an opposite way. varied from 0.4 to 38, mainly controlled by fO2, P, and T. Our new results along with previous data suggest that in a magma ocean, in particular at dry conditions, much more C than S would have segregated in the core. To satisfy the C/S ratios currently estimated for Earth's core and silicate mantle [2], a C-rich but S-poor material needs to be delivered to the silicate Earth after complete core formation. Alternatively, a C- and S-rich material was delivered to the Earth during the late stage of core formation, but with S preferentially segregated in the core in the form of sulfide. [1] Li et al. (2015), EPSL. [2]McDonough (2014), Treatise Geochem.

  20. Silicate glasses and sulfide melts in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure, Virginia, USA

    Science.gov (United States)

    Belkin, H.E.; Horton, J. Wright

    2009-01-01

    Optical and electron-beam petrography of melt-rich suevite and melt-rock clasts from selected samples from the Eyreville B core, Chesapeake Bay impact structure, reveal a variety of silicate glasses and coexisting sulfur-rich melts, now quenched to various sulfi de minerals (??iron). The glasses show a wide variety of textures, fl ow banding, compositions, devitrifi cation, and hydration states. Electron-microprobe analyses yield a compositional range of glasses from high SiO2 (>90 wt%) through a range of lower SiO2 (55-75 wt%) with no relationship to depth of sample. Some samples show spherical globules of different composition with sharp menisci, suggesting immiscibility at the time of quenching. Isotropic globules of higher interfacial tension glass (64 wt% SiO2) are in sharp contact with lower-surface-tension, high-silica glass (95 wt% SiO2). Immiscible glass-pair composition relationships show that the immiscibility is not stable and probably represents incomplete mixing. Devitrifi cation varies and some low-silica, high-iron glasses appear to have formed Fe-rich smectite; other glass compositions have formed rapid quench textures of corundum, orthopyroxene, clinopyroxene, magnetite, K-feldspar, plagioclase, chrome-spinel, and hercynite. Hydration (H2O by difference) varies from ~10 wt% to essentially anhydrous; high-SiO2 glasses tend to contain less H2O. Petrographic relationships show decomposition of pyrite and melting of pyrrhotite through the transformation series; pyrite? pyrrhotite? troilite??? iron. Spheres (~1 to ~50 ??m) of quenched immiscible sulfi de melt in silicate glass show a range of compositions and include phases such as pentlandite, chalcopyrite, Ni-As, monosulfi de solid solution, troilite, and rare Ni-Fe. Other sulfi de spheres contain small blebs of pure iron and exhibit a continuum with increasing iron content to spheres that consist of pure iron with small, remnant blebs of Fe-sulfi de. The Ni-rich sulfi de phases can be explained by

  1. Local structural variation with oxygen fugacity in Fe2SiO4+x fayalitic iron silicate melts

    Science.gov (United States)

    Alderman, O. L. G.; Lazareva, L.; Wilding, M. C.; Benmore, C. J.; Heald, S. M.; Johnson, C. E.; Johnson, J. A.; Hah, H.-Y.; Sendelbach, S.; Tamalonis, A.; Skinner, L. B.; Parise, J. B.; Weber, J. K. R.

    2017-04-01

    The structure of molten Fe2SiO4+x has been studied using both high-energy X-ray diffraction and Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy, combined with aerodynamic levitation and laser beam heating. A wide range of Fe3+ contents were accessed by varying the levitation and atmospheric gas composition. Diffraction measurements were made in the temperature (T) and oxygen partial pressure ranges 1624(21) Iron K-edge XANES measurements covered the ranges 1557(33) oxidation state from XANES spectra. XANES pre-edge peak areas imply average Fe-O coordination numbers, nFeO, close to 5 for all Fe3+/ΣFe. Diffraction measurements yielded values of 4.4(2) oxidation during cooling, enabled by stirring of the melt by the levitation gas flow. As such, the oxidation state of hot komatiitic and other highly fluid melts may not be retained, even during rapid cooling, as it is for cooler basaltic and more silicic magmas.

  2. Determination of Magma Ascent Rates From D/H Fractionation in Olivine-Hosted Melt Inclusions

    Science.gov (United States)

    Gaetani, G. A.; Bucholz, C. E.; Le Roux, V.; Klein, F.; Ghiorso, M. S.; Wallace, P. J.; Sims, K. W. W.

    2016-12-01

    The depths at which magmas are stored and the rates at which they ascend to Earth's surface are important controls on the dynamics of volcanic eruptions. Eruptive style is influenced by the rate at which magma ascends from the reservoir to the surface through its effect on vapor bubble nucleation, growth, and coalescence. However, ascent rates are difficult to quantify because few accurate geospeedometers are appropriate for a process occurring on such short timescales. We developed a new approach to determining ascent rates on the basis of D/H fraction associated with diffusive H2O loss from olivine-hosted melt inclusions. The utility of this approach was demonstrated on olivine-hosted melt inclusions in a hyaloclastite recovered from within Dry Valley Drilling Project core 3 from Hut Point Peninsula, Antarctica. All of the melt inclusions are glassy and contain vapor bubbles. The volumes of melt inclusions and vapor bubbles were determined by X-ray microtomography, and the density of CO2 within each bubble was determined using Raman spectroscopy. Olivines were then polished to expose individual inclusions and analyzed for volatiles and dDVSMOW by secondary ion mass spectrometry. Total CO2 was reconstructed by summing CO2 in the included glass and vapor bubble. Entrapment pressures calculated on the basis of reconstructed CO2 and maximum H2O concentrations using the MagmaSat solubility model [1] indicate a depth of origin of 24 km - in good agreement with the seismically determined depth to the Moho beneath Ross Island [2]. Magma ascent rates were determined using a finite difference model for melt inclusion dehydration during magma ascent. The positive correlation between H2O and CO2 is consistent with diffusive loss during ascent, but does not provide direct information on magma ascent rate. In contrast, the slope of the negative correlation between H2O and dDVSMOW is a reflection of transport time and, therefore, ascent rate. If it is assumed that magmas did

  3. Calcium isotopic fractionation in mantle peridotites by melting and metasomatism and Ca isotope composition of the Bulk Silicate Earth

    Science.gov (United States)

    Kang, Jin-Ting; Ionov, Dmitri A.; Liu, Fang; Zhang, Chen-Lei; Golovin, Alexander V.; Qin, Li-Ping; Zhang, Zhao-Feng; Huang, Fang

    2017-09-01

    To better constrain the Ca isotopic composition of the Bulk Silicate Earth (BSE) and explore the Ca isotope fractionation in the mantle, we determined the Ca isotopic composition of 28 peridotite xenoliths from Mongolia, southern Siberia and the Siberian craton. The samples are divided in three chemical groups: (1) fertile, unmetasomatized lherzolites (3.7-4.7 wt.% Al2O3); (2) moderately melt-depleted peridotites (1.3-3.0 wt.% Al2O3) with no or very limited metasomatism (LREE-depleted cpx); (3) strongly metasomatized peridotites (LREE-enriched cpx and bulk rock) further divided in subgroups 3a (harzburgites, 0.1-1.0% Al2O3) and 3b (fertile lherzolites, 3.9-4.3% Al2O3). In Group 1, δ44/40Ca of fertile spinel and garnet peridotites, which experienced little or no melting and metasomatism, show a limited variation from 0.90 to 0.99‰ (relative to SRM 915a) and an average of 0.94 ± 0.05‰ (2SD, n = 14), which defines the Ca isotopic composition of the BSE. In Group 2, the δ44/40Ca is the highest for three rocks with the lowest Al2O3, i.e. the greatest melt extraction degrees (average 1.06 ± 0.04 ‰, i.e. ∼0.1‰ heavier than the BSE estimate). Simple modeling of modal melting shows that partial melting of the BSE with 103 ln ⁡αperidotite-melt ranging from 0.10 to 0.25 can explain the Group 2 data. By contrast, δ44/40Ca in eight out of nine metasomatized Group 3 peridotites are lower than the BSE estimate. The Group 3a harzburgites show the greatest δ44/40Ca variation range (0.25-0.96‰), with δ44/40Ca positively correlated with CaO and negatively correlated with Ce/Eu. Chemical evidence suggests that the residual, melt-depleted, low-Ca protoliths of the Group 3a harzburgites were metasomatized, likely by carbonate-rich melts/fluids. We argue that such fluids may have low (≤0.25‰) δ44/40Ca either because they contain recycled crustal components or because Ca isotopes, similar to trace elements and their ratios, may be fractionated by kinetic and

  4. Sulphur-Rich Melt At Upper Crustal Levels At Cerro La Torta, Central Andes: Evidence From Melt Inclusions Assemblages.

    Science.gov (United States)

    Cannatelli, C.; Godoy, B.; Alvear, B.; Moncada, D.

    2016-12-01

    Central Andes present some of the biggest and most important porphyry copper ore deposits in the world. Porphyry copper ore formation is related to precipitation of ore minerals from sulphur and chlorine-rich fluids. Genesis of these deposits occurred 4 km below surface, while mineralized fluids are released by magmatic melts located between 5 and 15 km depth (Sillitoe, 2010). Cerro La Torta is part of a cluster of mineral present. Melt Inclusions size ranges from 10-40 µm, suggesting an intermediate cooling rate (Roedder 1979). Out hypothesis is that during cooling, Group I MIA is trapped as result of a metal sulfur-rich event, leading to the suggestion that sulphide-bearing MIAs from Cerro La Torta are the evidence of mineralized magmas ponding at shallow crustal levels. Furthermore, the presence of MIAs in the mush-type magmas related to the APMB implies that such systems are suitable to porphyry copper ore generation. Roedder, 1979. The Evolution of the Igneous Rocks. 15-57 Sillitoe, 2010. Econ. Geol. 105:3-41 Tierney et al., 2016. Geology 44:683-686. doi:10.1130/G37968.1Ward et al., 2014. Earth Planet Sci Letters 404:43-54

  5. Influence of small particles inclusion on selective laser melting of Ti-6Al-4V powder

    Science.gov (United States)

    Gong, Haijun; Dilip, J. J. S.; Yang, Li; Teng, Chong; Stucker, Brent

    2017-12-01

    The particle size distribution and powder morphology of metallic powders have an important effect on powder bed fusion based additive manufacturing processes, such as selective laser melting (SLM). The process development and parameter optimization require a fundamental understanding of the influence of powder on SLM. This study introduces a pre-alloyed titanium alloy Ti-6Al-4V powder, which has a certain amount of small particles, for SLM. The influence of small particle inclusion is investigated through microscopy of surface topography, elemental and microstructural analysis, and mechanical testing, compared to the Ti-6Al-4V powder provided by SLM machine vendor. It is found that the small particles inclusion in Ti-6Al-4V powder has a noticeable effect on extra laser energy absorption, which may develop imperfections and deteriorate the SLM fatigue performance.

  6. No iron isotope fractionation between molten alloys and silicate melt to 2000 degrees C and 7.7 GPa : experimental evidence and implications for planetary differentiation and accretion

    OpenAIRE

    Poitrasson, Franck; Roskosz, M.; Corgne, A.

    2009-01-01

    Whether core-mantle differentiation of terrestrial planets fractionates iron isotope is currently a debated issue. Melting experiments corresponding to the conditions inferred for core differentiation in an early silicate magma ocean were performed at 1750 and 2000 degrees C, and from 1 to 7.7 GPa to address this question. The starting mixtures correspond to a devolatilized CI chondrite composition and oxygen fugacity conditions were similar to 2 log units below the iron-wustite buffer. Scann...

  7. Insights on chaotic dynamics: mixing experiments between natural silicate melts from Vulcano island (Aeolian Islands, Italy)

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Vetere, Francesco; Petrelli, Maurizio; Perugini, Diego

    2017-04-01

    keywords: Magma mixing, chaotic dynamics, time series experiments Magma mixing is a petrologic phenomenon which is recognized as potential trigger of highly explosive eruptions and its evidence is commonly observable in natural rocks. Here we tried to replicate the dynamic conditions of mixing performing a set of chaotic mixing experiments between shoshonitic and rhyolitic magmas from Vulcano island. Vulcano is the southernmost island of the Aeolian Archipelago (Aeolian Islands, Italy); it is completely built by volcanic rocks with variable degree of evolution ranging from basalt to rhyolite (e.g. Keller 1980; Ellam et al. 1988; De Astis 1995; De Astis et al. 2013) and its magmatic activity dates back to about 120 ky. Last eruption occurred in 1888-1890. The chaotic mixing experiments were performed by using the new ChaOtic Magma Mixing Apparatus (COMMA), held at the Department of Physics and Geology, University of Perugia. This new experimental device allows to track the evolution of the mixing process and the associated modulation of chemical composition between different magmas. Experiments were performed at 1200°C and atmospheric pressure with a viscosity ratio higher than three orders of magnitude. The experimental protocol was chosen to ensure the occurrence of chaotic dynamics in the system and the run duration was progressively increased (e.g. 10.5 h, 21 h, 42 h). The products of each experiment are crystal-free glasses in which the variation of major elements was investigated along different profiles using electron microprobe (EMPA) at Institute für Mineralogie, Leibniz Universität of Hannover (Germany). The efficiency of the mixing process is estimated by calculating the decrease of concentration variance in time and it is shown that the variance of major elements exponentially decays. Our results confirm and quantify how different chemical elements homogenize in the melt at differing rates. It is also observable that the mixing structures generated

  8. Melt Inclusion Analysis of RBT 04262 with Relationship to Shergottites and Mars Surface Compositions

    Science.gov (United States)

    Potter, S. A.; Brandon, A. D.; Peslier, A. H.

    2015-01-01

    Martian meteorite RBT 04262 is in the shergottite class. It displays the two lithologies typically found in "lherzolitic shergottites": one with a poikilitic texture of large pyroxene enclosing olivine and another with non-poikilitic texture. In the case of RBT 04262, the latter strongly ressembles an olivine- phyric shergottite which led the initial classification of this meteorite in that class. RBT 04262 has been studied with regards to its petrology, geochemistry and cosmic ray exposure and belongs to the enriched oxidized end-member of the shergottites. Studies on RBT 04262 have primarily focused on the bulk rock composition or each of the lithologies independently. To further elucidate RBT 04262's petrology and use it to better understand Martian geologic history, an in-depth study of its melt inclusions (MI) is being conducted. The MI chosen for this study are found within olivine grains. MI are thought to be trapped melts of the crystallizing magma preserved by the encapsulating olivine and offer snapshots of the composition of the magma as it evolves. Some MI, in the most Mg-rich part of the olivine of olivine-pyric shergottites, may even be representative of the meteorite parent melt.

  9. Chemical zonation in olivine-hosted melt inclusions: A record of syn-eruptive cooling

    Science.gov (United States)

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

    2013-12-01

    During the last few minutes to hours of a volcanic eruption, olivine-hosted melt inclusions (MIs) cool and crystallize olivine on their walls, producing olivine-depleted boundary layers in the melt adjacent to their olivine hosts. Competition between diffusive relaxation of these boundary layers into the centers of the MIs and replenishment of the boundary layers by continued olivine crystallization produces concentration profiles that are preserved in glassy MIs. The concentration profile of a given element in a single MI depends on the diffusion coefficient of the element in the melt, its partition coefficient between melt and olivine, and the growth rate of the olivine. Concentration profiles thus differ from element to element in a single MI, and also from inclusion to inclusion depending on the size of the MI and its thermal history. An implication of this chemical zonation is that analyses of zoned MIs, even if made near the centers of the MIs, will be diffusively fractionated relative to a simple olivine extraction path (i.e., the diffusion of fast-diffusing elements such as Ca can extend to the center of a ~150 μm radius MI). We have developed a model that uses measured MgO concentration profiles across compositionally zoned, naturally glassy, olivine-hosted MIs to constrain the thermal histories of the MIs in the last few minutes to hours of an eruption. We have applied this model to MIs sampled from three different magmatic settings: (1) glassy rims of pillow basalts sampled from the Siqueiros transform fault; (2) a hornito on Santiago Island, (Galapagos); (3) a lava flow on a submarine flank of Fernandina Island (Galapagos). Cooling rates of five MIs from the Siqueiros transform fault range from ~0.08-3 K/s. Most MIs from this sample suite require two-stage, linear cooling histories from liquidus temperatures to ~1000°C with a slower-cooling first stage followed by a faster-cooling second stage, over a time period of a few minutes to just over one hour

  10. Homogenization Temperature Measurements in Hydrothermal Diamond-Anvil Cell for Melt and Fluid Inclusions from the Jiajika Pegmatite Deposit, China

    Science.gov (United States)

    Li, J.; Chou, I.; Yuan, S.; Burruss, R. C.

    2009-12-01

    We measured the total homogenization temperatures (Th) of volatile-rich melt and fluid inclusions under elevated external pressures in a hydrothermal diamond-anvil cell (HDAC) to understand fluid evolution in the Jiajika pegmatite deposit in China, the largest spodumene deposit in Asia. Three types of inclusions were investigated: 1. CH4-H2O (~10 vol. %) bearing aluminosilicate melt inclusions hosted in quartz from granite; 2. CO2-NaCl-H2O (~80 vol. %) inclusions with daughter minerals mainly hosted in spodumene from pegmatite dikes; and 3. CO2-NaCl-H2O inclusions mainly hosted in quartz from pegmatite dikes. During normal microthermometric measurements at atmospheric pressure, most of these inclusions decrepitated at ~300°C. Therefore, we extended the method of Schmidt et al. (1998, Am. Mineral. 83, 995) and Darling and Bassett (2002, Am. Mineral., 87, 67) to melt inclusions in HDAC and conducted long-duration experiments with type 1 and 2 inclusions at one kbar Ar pressure in cold-seal pressure vessels (CSPV) as described by Thomas et al. (2006, Chapter 9 in Mineralogical Association of Canada Short Course, 36, 189). Results in both HDAC and CSPV experiments showed that Th's of type 1 and 2 inclusions were between 600 and 700 °C and between 500 and 700 °C, respectively. In HDAC experiments for type 1 inclusions, daughter minerals melted and coexisted with the fluid phase before total homogenization; however, in type 2 inclusions, daughter minerals dissolved completely in the CO2-NaCl-H2O solution at Th. Results obtained for type 3 inclusions showed that the CO2-rich and CO2-poor inclusions homogenized to liquid CO2 and aqueous phases at 260 - 570 and 240 - 350°C, respectively. Also, Th’s decrease linearly as the external pressure increases; the reduction of Th was ~1.5 °C/kbar, which is similar to ~1.2 °C/kbar reported by Darling and Bassett (ibid.) for the same type of natural fluid inclusions, but is much less than ~4.6 °C/kbar reported by Schmidt et

  11. Geochemical heterogeneities in magma beneath Mount Etna recorded by 2001-2006 melt inclusions

    Science.gov (United States)

    Schiavi, Federica; Rosciglione, Alberto; Kitagawa, Hiroshi; Kobayashi, Katsura; Nakamura, Eizo; Nuccio, Pasquale Mario; Ottolini, Luisa; Paonita, Antonio; Vannucci, Riccardo

    2015-07-01

    We present a geochemical study on olivine and clinopyroxene-hosted melt inclusions (MIs) from 2001 to 2006 Etna basaltic lavas and pyroclastites. Three MI suites are distinguished on the basis of trace element fingerprinting. Type-1 MIs (from 2001 Upper South and 2002 Northeast vents) share their trace element signature with low-K lavas erupted before 1971. Critical trace element ratios (e.g., K/La, Ba/Nb), along with Pb isotope data of Type-1 MIs provide evidence for a heterogeneous mantle source resulting from mixing of three end-members with geochemical and isotopic characteristics of EM2, DMM, and HIMU components. Type-1 MIs composition does not support involvement of subduction-related components. Type-2 (from 2001 Lower and 2002 South vents) and Type-3 (2004 eruption) MIs reveal "ghost plagioclase signatures," namely lower concentrations in strongly incompatible elements, and positive Sr, Ba, and Eu anomalies. Both Type-1 and Type-2 MIs occur in 2006 olivines, which highlight the occurrence of mixing between Type-1 and Type-2 end-members. Type-2/Type-3 MIs testify to en route processes (plagioclase assimilation and volatile fluxing) peculiar for "deep dike fed" eruptions. The latter are strongly controlled by tectonics or flank instability that occasionally promote upraise of undegassed, more radiogenic primitive magma, which may interact with plagioclase-rich crystal mush/cumulates before erupting. Type-2/Type-3 MIs approach the less radiogenic Pb isotopic composition of plagioclase from prehistoric lavas, thus suggesting geochemical overprinting of present-day melts by older products released from distinct mantle sources. Our study emphasizes that MIs microanalysis offers new insights on both source characteristics and en route processes, allowing to a link between melt composition and magma dynamics.

  12. Removal of Non-metallic Inclusions from Nickel Base Superalloys by Electromagnetic Levitation Melting in a Slag

    Science.gov (United States)

    Manjili, Mohsen Hajipour; Halali, Mohammad

    2018-02-01

    Samples of INCONEL 718 were levitated and melted in a slag by the application of an electromagnetic field. The effects of temperature, time, and slag composition on the inclusion content of the samples were studied thoroughly. Samples were compared with the original alloy to study the effect of the process on inclusions. Size, shape, and chemical composition of remaining non-metallic inclusions were investigated. The samples were prepared by Standard Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel (ASTM E 768-99) method and the results were reported by means of the Standard Test Methods for Determining the Inclusion Content of Steel (ASTM E 45-97). Results indicated that by increasing temperature and processing time, greater level of cleanliness could be achieved, and numbers and size of the remaining inclusions decreased significantly. It was also observed that increasing calcium fluoride content of the slag helped reduce inclusion content.

  13. Removal of Non-metallic Inclusions from Nickel Base Superalloys by Electromagnetic Levitation Melting in a Slag

    Science.gov (United States)

    Manjili, Mohsen Hajipour; Halali, Mohammad

    2017-11-01

    Samples of INCONEL 718 were levitated and melted in a slag by the application of an electromagnetic field. The effects of temperature, time, and slag composition on the inclusion content of the samples were studied thoroughly. Samples were compared with the original alloy to study the effect of the process on inclusions. Size, shape, and chemical composition of remaining non-metallic inclusions were investigated. The samples were prepared by Standard Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel (ASTM E 768-99) method and the results were reported by means of the Standard Test Methods for Determining the Inclusion Content of Steel (ASTM E 45-97). Results indicated that by increasing temperature and processing time, greater level of cleanliness could be achieved, and numbers and size of the remaining inclusions decreased significantly. It was also observed that increasing calcium fluoride content of the slag helped reduce inclusion content.

  14. Experimental observations on noble metal nanonuggets and Fe-Ti oxides, and the transport of platinum group elements in silicate melts

    Science.gov (United States)

    Anenburg, Michael; Mavrogenes, John A.

    2016-11-01

    Platinum group element (PGE) nanonuggets are a nuisance in experimental studies designed to measure solubility or partitioning of noble metals in silicate melts. Instead of treating nanonuggets as experimental artifacts, we studied their behaviour motivated by recent discoveries of PGE nanonuggets in a variety of natural settings. We used an experimental setup consisting of AgPd, Pt or AuPd capsules and Fe(-Ti) oxide-saturated hydrous peralkaline silicate melts to maximise nanonugget production. TABS (Te, As, Bi, Sb, Sn) commonly occur in PGM (platinum group minerals), prompting addition of Bi to our experiments to investigate its properties as well. Three-dimensional optical examination by 100× objective and immersion oil reveals variable colour which correlates with nanonugget size and shape due to plasmon resonance effects. We observe two textural types: (1) intermediate-sized nanonuggets dispersed in the glass and adhering to oxides, and (2) abundant fine nanonuggets dispersed in the glass with coarse euhedral crystals in contact with oxides. Slow cooling removes dispersed nanonuggets and greatly coarsens existing oxide-associated metal crystals. Nanonugget-free halos are commonly observed around oxide grains. All metal phases are composed of major (Ag, Pd) and trace (Pt, Ir, Au) capsule material. Our results show reduction processes, imposed by growing oxides, causing local metal saturation in the oxide rich zones with preferential nucleation on smaller oxide grains. The redox gradient then blocks additional metals from diffusing into oxide rich zones, forming halos. As the entire experimental charge is reduced throughout the run, nanonuggets form in the distal glass. Bismuth contents of metal phases do not depend on Bi2O3 amounts dissolved in the melt. Further PGM crystallisation consumes nanonuggets as feedstock. We conclude that the appearance of metallic PGE phases happens in two stages: first as nanonuggets and then as larger PGM. Once formed

  15. Volatiles in Olivine Hosted Melt Inclusions from Small Eruptive Centers of the Central Southern Volcanic Zone (CSVZ), Chile

    Science.gov (United States)

    Wacaster, S.; Hickey-Vargas, R.; Wallace, P.

    2008-12-01

    This study is a geochemical analysis of basaltic scoria cones of the CSVZ, where bulk rock analyses have revealed two predominant lava types. We consider the relationship of cones to nearby stratovolcanos and the proximity of both to the Liquine-Ofqui Fault Zone to understand how primitive melts with wide ranging compositions are generated. We characterize melt inclusions to see if they show similar trends as bulk rocks and to evaluate degassing of melts during ascent and crystallization. We report new CO2, H2O, F, S, and Cl data collected by SIMS and FTIR. Type 1 and Type 2 lavas have been identified in prior studies. Type 1 rocks have significant 238U/232Th excesses and higher abundances of fluid mobile elements. Type 2 lavas and scorias have higher LREE/HREE ratios, lower abundances of fluid mobile elements, lower 87Sr/86Sr and U- series isotopes near secular equilibrium. Type 1, usually associated with composite volcanic centers, erupt at one cone in our field area, while Type 2 is found only at other individual cones aligned with the LOFZ. We characterize olivine-hosted melt inclusions with emphasis on volatile element analyses to test the hypotheses of flux melting beneath Type 1 centers versus a lesser extent of decompression melting beneath Type 2 centers. Melt inclusions show the following overall ranges of volatiles: CO2: below detection-1208 ppm; H2O(Total): 0.11-3.9 wt percent: F: 52-1442 ppm; S: 34-2884 ppm, and Cl: 177-1606 ppm. Inclusions from lavas are generally more degassed when compared to those from scoria for CO2 and H2O. Some Cl and F values are lower in inclusions from lavas, but not all. Sulfur is variably degassed in melt inclusions from both lavas and scoria. Melt inclusions from Type 2 Caburgua scoria show evidence for variable degassing and crystallization pressures. One subset of the inclusions were trapped at low pressures (P CO2 CO2 (1.5-4.0 wt % and 300-800 ppm and all under 1100 bars). Type I San Jorge melt inclusions also show

  16. Experimental investigation of the degassing behavior of Hg via proxy heavy metals in natural and synthetic silicate melts

    Science.gov (United States)

    Johnson, A. D.; Canil, D.

    2009-12-01

    The degassing behavior of Bi, Tl, Au, Cd and Pb from silicate liquids have been investigated at 0.1 MPa. These metals were chosen on the basis that they may be used as a proxy for Hg. Natural basalt, dacite, and synthetic rhyolite (Ab-Or-Qz minimum eutectic) were doped with a heavy metal cocktail (Bi, Pb, Tl, Au, Re, Sb, Sn, In, Cd, Mo, As, Cu) and diffusion experiments were conducted in air at 0.1 MPa between 1200 - 1450 °C in open Pt capsules. Trace element concentration gradients for Bi, Tl, Au, Cd and Pb were measured normal to the polished melt(glass)/gas interface by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) after the experiment. Diffusion coefficients (Dx) were extracted for elements using a semi-infinite one-dimensional diffusion model. The effects of ligands on diffusivity were measured by adding Cl or S to experimental runs. Results show Au and Tl (which bracket Hg in the periodic table) are the most volatile in dacite at 1260°C (logDAu = -10.66 ± 0.20 m2/s and logDTl = -11.03 ± 0.15 m2/s ) followed by Cd, Pb and Bi (logDCd = -11.58 ± 0.07 m2/s, logDPb = -11.77 ± 0.2 m2/s, logDBi = -12.11 ± 0.2 m2/s;). The effect of starting composition on metal diffusion shows the diffusivity of Tl at 1260°C decreases from logDTl = -10.84 ± 0.22 m2/s in basalt to logDTl = -11.03 ± 0.15 m2/s and logDTl = -11.60 ± 0.20 m2/s in dacite and synthetic Ab-Or-Qz respectively. Decreasing diffusivity would be expected with increasing silica content that inhibits diffusion. We apply our diffusivities in a 1-D bubble growth model to observe differences in metal ratios in gas bubbles that would form in volcanic plumes. In this way, we see the changing heavy metal ratios in the gas phase may be useful in eruption prediction. This work may also help better constrain the behavior/mobility of Hg (using these metals as a proxy) in nature and its loading effect from volcanoes on the atmosphere and biosphere.

  17. Magmatic Processes in Monogenetic Eruptions, Procida Island, Campi Flegrei, Italy: Geochemical Evidence From Melt Inclusions

    Science.gov (United States)

    Severs, M. J.; Fedele, L.; Esposito, R.; Bodnar, R.; Petrosino, P.; Lima, A.; de Vivo, B.; Shimizu, N.

    2008-12-01

    Campi Flegrei is an active volcanic complex located in the greater Naples area, which has produced more than 50 eruptions over the past 60,000 years. These have ranged from small eruptions such as Monte Nuovo eruption of 1538 CE to extremely large eruptions such as the Campanian Ignimbrite (150-200 DRE; Barbieri et al., 1978). The volcanic field includes the mainland area located to the west of Naples and also the two islands of Ischia and Procida. The volcanic products range from basalts to shoshonitic phonolites and trachytes, with the more evolved magmas being more abundant. Three eruptive units from Procida Island have been studied to observe geochemical trends over time within a small area and to better understand magmatic processes between monogenetic eruptions. Juvenile samples from Pozzo Vecchio, Breccia Museo, and Solchiara were collected to examine the geochemistry of the mineral phases present and melt inclusions (MIs) found within the phenocrysts. Solchiara contained phenocrysts of olivine and clinopyroxene, whereas Breccia Museo and Pozzo Vecchio samples contained clinopyroxene and sanidine as the dominant phenocryst phases. Melt inclusions from Solchiara have narrow compositional ranges in major and trace elements (i.e., CaO, TiO2, Zr, Dy, La) over a large range in SiO2 contents (47 to 55 wt%) while MI from the Breccia Museo have a limited range of SiO2 contents (57 to 61 wt%) with a wider range for major and trace elements (i.e., FeO, Al2O3, CaO, La, Th, Rb). Pozzo Vecchio MI from clinopyroxene and sanidine define different chemical compositions, but petrographic evidence does not suggest a xenocrystic origin for either mineral phase. This suggests that Pozzo Vecchio is the result of magma mixing. Modeling of fractional crystallization of olivine, clinopyroxene, and sanidine are capable of producing most of the trends in major and trace elements between the most primitive samples to the most evolved samples. Volatile concentrations between the

  18. Trace element partitioning between plagioclase and silicate melt: The importance of temperature and plagioclase composition, with implications for terrestrial and lunar magmatism

    Science.gov (United States)

    Sun, Chenguang; Graff, Michelle; Liang, Yan

    2017-06-01

    Trace element partition coefficients between anorthitic plagioclase and basaltic melts (D) have been determined experimentally at 0.6 GPa and 1350-1400 °C in a lunar high-Ti picritic glass and a mid-ocean ridge basalt (MORB). Plagioclases with 98 mol% and 86 mol% anorthite were produced in the lunar picritic melt and MORB melt, respectively. Based on the new experimental partitioning data and those selected from the literature, we developed parameterized lattice strain models for the partitioning of monovalent (Na, K, Li), divalent (Ca, Mg, Ba, Sr, Ra) and trivalent (REE and Y) cations between plagioclase and silicate melt. Through the new models we showed that the partitioning of these trace elements in plagioclase depends on temperature, pressure, and the abundances of Ca and Na in plagioclase. Particularly, Na content in plagioclase primarily controls divalent element partitioning, while temperature and Ca content in plagioclase are the dominant factors for REE partitioning in plagioclase. From these models, we also derived a new expression for DRa/DBa that can be used for Ra-Th dating on volcanic plagioclase phenocrysts, and a new model for plagioclase-melt noble gas partitioning. Applications of these partitioning models to fractional crystallization of MORB and lunar magma ocean (LMO) indicate that (1) the competing effect of temperature and plagioclase composition leads to small variations of plagioclase-melt DREE during MORB differentiation, but (2) the temperature effect is especially significant and can vary anorthite-melt DREE by over one order of magnitude during LMO solidification. Temperature and plagioclase composition have to be considered when modeling the chemical differentiation of mafic to felsic magmas involving plagioclase.

  19. Correlations between Pb isotopes and volatile elements in melt inclusions from Sao Miguel, Azores

    Science.gov (United States)

    Moreira, M. A.; Rose-Koga, E. F.; Koga, K. T.; Vlastelic, I.; Shimizu, N.; Whitehouse, M.

    2009-12-01

    Sao Miguel is the biggest eastern-most island of the Azores archipelago in the northern Atlantic and is known to have a very peculiar isotopic systematics including Sr, Nd and Pb. We studied 4 lavas of Sao Miguel, one is from the 1563 historical lava flow Queimado peak eruption, one is from Picos Volcanic zone and the two others are Pliocene ankaramites from the Nordest. The olivine phenocrysts of these samples have been documented for helium isotopes and show very radiogenic 3He/4He ratios (<6Ra). We analyzed 9 primitive olivine-hosted melt inclusions for both Pb isotopes and volatile element concentrations (H2O, CO2, F, S, and Cl). The Pb isotope ratios were measured by a multicollection SIMS 1280 (NMNH Stockholm, Sweden) and volatiles by a monocollection SIMS 1280 (WHOI, USA). The repeated 207Pb/206Pb measurements of the GOR132 glass standard (20 ppm Pb) yielded a 0.15% relative variation (1 sigma of the distribution). All the melt inclusions have 207Pb/206Pb (0.782 to 0.797) and 208Pb/206Pb (1.969 to 2.041) lower than MORB value (DMM: 0.857, 2.053), i.e., more radiogenic compositions. We found positive linear correlations between 207Pb/206Pb and CO2, F, S, and Cl. The correlations further improve when Pb isotope ratios are plotted against F/P2O5, and Cl/K2O. The Sao Miguel source is characterized by a mixing between a low 207Pb/206Pb and low 208Pb/206Pb in the Nordest coming from a long time residence of high (U+Th)/Pb recycled material, and a component with higher ratios, more similar to other islands from the central group. The low 3He/4He ratio measured on Nordest samples also suggests a high (U+Th)/3He in its source, which may be due to degassing presumably during an early stage of the recycling. The low 207Pb/206Pb with low volatiles samples could also be explain this early degassing. Samples with the highest 207Pb/206Pb are richer in volatile suggesting the presence of a volatile rich lithology beneath the Azores central group, which was also proposed by

  20. Magma evolution at Copahue volcano (Chile/Argentina border): insights from melt inclusions

    Science.gov (United States)

    Cannatelli, C.; Aracena, C.; Leisen, M.; Moncada, D.; Roulleau, E.; Vinet, N.; Petrelli, M.; Paolillo, A.; Barra, F.; Morata, D.

    2016-12-01

    Copahue volcano is an active stratovolcano in the Andean Southern Volcanic Zone (SVZ), straddling at the border between Central Chile and Argentina. The volcano's eruptive style during its history has changed from mainly effusive in the Pleistocene to explosive in the Holocene. The prehistoric eruptions can be divided into pre-glacial (PG), syn-glacial (SG) and post-glacial (PM) stages, with products ranging from basaltic andesites to andesites. In order to investigate the evolution of the magma source and volatiles through time, we have focused our study on the eruptive products from the SG to the 2014 eruption (SUM2014). Sampled rocks are glomero-porphyritic, with a paragenetic mineral sequence of feldspars, ortho- and clinopyroxene, and olivine in order of abundance. All samples present a variable number of vesicles, with SUM2014 samples containing the biggest amount. Feldspar composition varies from Na-rich (andesine) in SG to Ca-rich (labradorite) in SUM2014. Two pyroxene types are present in SG and PM samples (augite and enstatite), while SUM2014 presents augite, pigeonite and enstatite. Thermobarometric estimation, based on mineral chemistry, show a bimodal distribution for SG and SUM2014 (P=10-12 kbars and 5-8 kbars) and only one interval for PM (P=7-8 kbars). Melt Inclusions Assemblages (MIAs) are found in all mineral phases, mostly re-crystallized, with one or more bubbles and daughter oxide minerals. Compositions vary from trachy-andesitic to dacitic for SG, andesitic to trachydacitic for PM, and basaltic andesitic to trachydacitic for SUM2014. Major elements systematics show the existence of a bimodal distribution of pyroxene and feldspar hosted-MIA in SUM2014, which together with the co-presence of pigeonite (low-Ca pyroxene) and augite and the bimodal distribution of P, can be interpreted as evidence of mixing of two types of magmas, evolving at different depths. Trace elements systematics for MIA in SG, PM and SUM2014 show a negative anomaly for Nb

  1. Melt inclusion constraints on volatile systematics and degassing history of the 2014-2015 Holuhraun eruption, Iceland

    Science.gov (United States)

    Bali, E.; Hartley, M. E.; Halldórsson, S. A.; Gudfinnsson, G. H.; Jakobsson, S.

    2018-02-01

    The mass of volatiles emitted during volcanic eruptions is often estimated by comparing the volatile contents of undegassed melt inclusions, trapped in crystals at an early stage of magmatic evolution, with that of the degassed matrix glass. Here we present detailed characterisation of magmatic volatiles (H2O, CO2, S, Fl and Cl) of crystal-hosted melt and fluid inclusions from the 2014-2015 Holuhraun eruption of the Bárðarbunga volcanic system, Iceland. Based on the ratios of magmatic volatiles to similarly incompatible trace elements, the undegassed primary volatile contents of the Holuhraun parental melt are estimated at 1500-1700 ppm CO2, 0.13-0.16 wt% H2O, 60-80 ppm Cl, 130-240 ppm F and 500-800 ppm S. High-density fluid inclusions indicate onset of crystallisation at pressures ≥ 0.4 GPa ( 12 km depth) promoting deep degassing of CO2. Prior to the onset of degassing, the melt CO2 content may have reached 3000-4000 ppm, with the total magmatic CO2 budget estimated at 23-55 Mt. SO2 release commenced at 0.12 GPa ( 3.6 km depth), eventually leading to entrapment of SO2 vapour in low-density fluid inclusions. We calculate the syn-eruptive volatile release as 22.2 Mt of magmatic H2O, 5.9-7.7 Mt CO2, and 11.3 Mt of SO2 over the course of the eruption; F and Cl release were insignificant. Melt inclusion constraints on syn-eruptive volatile release are similar to estimates made during in situ field monitoring, with the exception of H2O, where field measurements may be heavily biased by the incorporation of meteoric water.

  2. Syneruptive deep magma transfer and shallow magma remobilization during the 2011 eruption of Shinmoe-dake, Japan—Constraints from melt inclusions and phase equilibria experiments

    Science.gov (United States)

    Suzuki, Yuki; Yasuda, Atsushi; Hokanishi, Natsumi; Kaneko, Takayuki; Nakada, Setsuya; Fujii, Toshitsugu

    2013-05-01

    The 2011 Shinmoe-dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian events and subsequent explosions (Jan 26-28), lava accumulation in the crater (end of January), and vulcanian eruptions (February-April). We have studied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes in the silicic magma mush. Most of the ejecta, including brown and gray colored pumice clasts (Jan 26-28), ballistically ejected dense lava (Feb 1), and juvenile particles in ash from the phreatomagmatic and vulcanian events are magma mixing products (SiO2 = 57-58 wt.%; 960-980 °C). Mixing occurred between silicic andesite (SA) and basaltic andesite (BA) magmas at a fixed ratio (40%-30% SA and 60%-70% BA). The SA magma had SiO2 = 62-63 wt.% and a temperature of 870 °C, and contains 43 vol.% phenocrysts of pyroxene, plagioclase, and Fe-Ti oxide. The BA magma had SiO2 = 55 wt.% and a temperature of 1030 °C, and contains 9 vol.% phenocrysts of olivine and plagioclase. The SA magma partly erupted without mixing as white parts of pumices and juvenile particles. The two magmatic end-members crystallized at different depths, requiring the presence of two separate magma reservoirs; shallower SA reservoir and deeper BA reservoir. An experimental study reveals that the SA magma had been stored at a pressure of 125 MPa, corresponding to a depth of 5 km. The textures and forms of phenocrysts from the BA magma indicate rapid crystallization directly related to the 2011 eruptive activity. The wide range of H2O contents of olivine melt inclusions (5.5-1.6 wt.%) indicates that rapid crystallization was induced by decompression, with olivine crystallization first (≤ 250 MPa), followed by plagioclase addition. The limited occurrence of olivine melt inclusions trapped at depths of existed in the SA reservoir in the precursor stage, were finally erupted together. Magnetite phenocrysts in the Feb 18 ash reveal the

  3. High-Temperature Fractionation of Iron Isotopes During Metal Segregation From a Silicate Melt: Experimental Study of Kinetic and Equilibrium Fractionation

    Science.gov (United States)

    Roskosz, M.; Luais, B.; Watson, H.; Toplis, M. J.; Alexander, C. M.; Mysen, B. O.

    2005-12-01

    Advances in mass spectrometry make it possible to measure isotopic variations of iron in meteoritic and igneous materials. However, interpreting these data is hampered by a lack of theoretical and experimental knowledge concerning how Fe isotopes fractionate during magmatic processes. As a first step in this direction we have performed experiments in which metallic iron was reduced and segregated from a silicate melt at one bar as a function of f(O2) and time. The starting material was a glass of anorthite-diopside eutectic composition, to which 9 wt% Fe2O3 was added. Experiments were performed at 1500 circC and f(O2) in the range 10-0.7 to 10-8 bars. A proportion of this iron is extracted through formation of an alloy with the Pt-capsule in which the melt was held. The silicate and metallic portions were physically separated and bulk analyses of each fraction performed using standard MC-ICP-MS methods. Furthermore, a Cameca 6f ion microprobe was used to measure isotopic profiles in metallic samples, such that kinetic and equilibrium effects may be disentangled and quantified. Large isotopic variations are observed and attributed to kinetic fractionation during incorporation of iron into the initially Fe-free Pt-capsule. This process leads to the formation of isotopically light metal and a heavy silicate. For instance, in samples heat-treated for 24 hours, metal fractions have δ56Fe/54Fe from 0 to -2‰, whereas silicate fractions have δ56Fe/54Fe from 0 to 4.8‰. These values are positively correlated with the fraction of iron lost to the platinum. Ion-probe analyses and time-series experiments confirm that Fe isotopes are strongly fractionated during diffusion of Fe in the Pt,Fe alloy, and the observed profiles are used to calculate the diffusion coefficients of individual iron isotopes. With increasing time at fixed oxygen fugacity, iron in the alloy reaches a constant isotopic composition. At these conditions, assumed to represent equilibrium, iron in the

  4. Immiscible iron- and silica-rich melt in basalt petrogenesis documented in the Skaergaard intrusion

    DEFF Research Database (Denmark)

    Jakobsen, Jakob Kløve; Veksler, Ilya; Tegner, Christian

    2005-01-01

    Silicate liquid immiscibility in basalt petrogenesis is a contentious issue. Immiscible iron and silica-rich liquids were reported in melt inclusions of lunar basalt and in groundmass glasses of terrestrial volcanics. In fully crystallized plutonic rocks, however, silicate liquid immiscibility has...

  5. The distribution of H2O between silicate melt and nominally anhydrous peridotite and the onset of hydrous melting in the deep upper mantle

    Science.gov (United States)

    Novella, Davide; Frost, Daniel J.; Hauri, Erik H.; Bureau, Helene; Raepsaet, Caroline; Roberge, Mathilde

    2014-08-01

    The partitioning of H2O between a mantle peridotite assemblage and low degree hydrous melt has been investigated at 6 GPa (corresponding to ∼180 km depth) at a temperature of 1400 °C. Peridotite mineral phases were analysed from 6 melting experiments performed in a natural chemical system. The experiments contained ∼80 wt% of a low degree hydrous melt that was obtained through a series of experiments where the melt composition was iteratively adjusted until saturation with the appropriate peridotite assemblage was achieved. The melt is fluid-undersaturated at the conditions of the experiment. Ion microprobe measurements of the mineral phases indicate olivine H2O concentrations of 434±61 ppm wt and average clinopyroxene (cpx) concentrations of 1268±173 ppm wt H2O. Orthopyroxene (opx) and garnet contain 700±46 ppm wt and 347±83 ppm wt H2O, respectively. The H2O content of the hydrous melts was determined by mass balance to be 11±0.5 wt% H2O. H2O partition coefficients between minerals and melt (DH2Omin/melt=XH2Omin/XH2Omelt) are 0.0040±0.0006 for olivine, 0.0064±0.0004 for opx, 0.0115±0.0016 for cpx and 0.0032±0.0008 for garnet. Using the determined H2O partition coefficients the onset and extent of melting at conditions equivalent to 180 km below mid-ocean ridges was determined as a function of mantle H2O content. Current estimates for the H2O content of the depleted mantle (50-200 ppm wt H2O) are insufficient to induce mantle melting at this depth, which requires ∼700 ppm wt H2O to produce 0.1% melting and 1600 ppm wt H2O for 1% melting, along an adiabat with a potential temperature of 1327 °C. Melting can occur at these conditions within the mantle source of ocean island basalts, which are estimated to contain up to 900 ppm wt H2O. If adiabatic temperatures are 200 °C higher within such plume related sources, then melt fractions of over 1% can be reached at 180 km depth. In addition, a model for the distribution of H2O between peridotite mineral

  6. Silicate volcanism on Io

    Science.gov (United States)

    Carr, M. H.

    1986-03-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  7. Magma transport and olivine crystallization depths in Kīlauea’s East Rift Zone inferred from experimentally rehomogenized melt inclusions

    Science.gov (United States)

    Tuohy, Robin M; Wallace, Paul J.; Loewen, Matthew W; Swanson, Don; Kent, Adam J R

    2016-01-01

    Concentrations of H2O and CO2 in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO2concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO2 is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai‘i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO2 in shrinkage bubbles. The measured CO2 concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n=10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n=38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO2 values than naturally quenched inclusions, indicating at least partial dissolution of CO2 from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO2 in the vapor bubbles suggests that 55-85% of the dissolved CO2 in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at crystallized over a much wider range of depths (∼1-16 km). The wider depth range requires magma transport during the Kapoho eruption from deep beneath the summit region and/or from deep beneath Kīlauea’s east rift zone. The deeply derived olivine crystals and their host magma mixed with stored, more evolved magma in the rift zone, and the mixture was later erupted at Kapoho.

  8. Melt inclusion study of the most recent basanites from El Hierro and Lanzarote, Canary Islands

    Science.gov (United States)

    Gomez-Ulla, Alejandra; Sigmarsson, Olgeir; Huertas, Maria Jose; Ancochea, Eumenio

    2015-04-01

    The latest eruptions of both Lanzarote (one of the oldest and easternmost of the Canary Island archipelago) and El Hierro (the youngest and westernmost) produced basanite lavas. Major, volatile and trace element concentrations of melt inclusion (MI) hosted in olivine for both eruptions have been analysed. The basanites display primitive mantle normalized trace element spectra suggesting a magma source largely composed of recycled oceanic crust. In addition, beneath Lanzarote an interaction with a carbonatitic fluid phase or metasome would explain eccentric Ba/U and other trace element ratios. Contribution of carbonatitic component would readily account for extremely volatile-rich (Cl, F, S) MI from Lanzarote (Cl=1577-2500 ppm) whereas the maximum for El Hierro is 1080 ppm. The submarine character of the 2011-12 eruption off El Hierro appears to have affected the degassing behavior, whereas estimated sulfur emission to the atmosphere during the historical Lanzarote eruptions are amongst the highest observed so far. An estimated magma volume (VDRE) of 0.02 km3 yields atmospheric mass loading of 0.2 Mt SO2 from the 1824 Lanzarote eruption. Scaling the volume of the 1824 Lanzarote eruption to that of the previous Timanfaya eruption (1730-6; 5 km3) results in estimated 12 Mt SO2, an atmospheric mass loading only outnumbered by the historical Laki and Eldgjá eruptions in Iceland. The significantly greater volatile budget of basanites from Lanzarote compared to El Hierro is thus controlled by more fertile source composition closer to the African continent.

  9. The Ignimbrite Campana Magma Chamber: Pre-eruptive P-t-x Conditions From Melt Inclusion Data

    Science.gov (United States)

    Marianelli, P.; Proto, M.; Sbrana, A.

    The Ignimbrite Campana (36 ka) represents the most powerful eruption characterizing the volcanic history of the Campi Flegrei caldera. The eruption was fed by a stratified magma chamber (Civetta et al., 1997). This study, based on melt inclusion investigations in phenocrysts of pumice, is aimed to better constrain depth, thermal conditions and composition of magmas hosted in the magma chamber. Samples from the Breccia Museo products (proximal deposits of the Ignimbrite Campana) were selected, due to their sin-eruptive and sin-depositional quenching. On the basis of melt inclusions investigations important informations about crystallization conditions (P, T, X) and volatile contents have been obtained. Glass compositions fall in the trachyte field close to the trachyte-phonolite boundary, similarly to the others Ignimbrite Campana products. The temperature of homogenization ranges between 850 and 1135°C. These values of temperature, that can be assumed as crystallization temperatures, correlate to the host crystal compositions with the highest one corresponding to melt inclusions trapped in less Fe-rich pyroxene. FTIR analyses on double -polished melt inclusions were carried out in order to investigate H2O and CO2 contents. Preliminary results indicate values of H2O that range from about 2 up to 8.0wt%, whereas CO2 was not detected. Lowest values of H2O (modal value = 2- 3wt%) correspond to the melt inclusions from layers at the top of the Breccia Museo (pumice flow deposits). Minimum pressures of crystallization are estimated in the range 100-200 MPa, assuming saturation conditions for the trapped melts and calculating the solubility of H2O in trachytic magmas according to the model of Moore et al. (1998). References Civetta L., Orsi G., Pappalardo L., Fisher R.V., Heiken G., Ort M. (1997): Geochemical zoning, mingling, eruptive dynamics and depositional processes ­ the Campanian Ignimbrite, Campi Flegrei caldera, Italy. J. Volcanol. Geoth. Res., 75: 183

  10. Lead isotope signatures of Kerguelen plume-derived olivine-hosted melt inclusions: Constraints on the ocean island basalt petrogenesis

    Science.gov (United States)

    Borisova, Anastassia Y.; Faure, François; Deloule, Etienne; Grégoire, Michel; Béjina, Frédéric; de Parseval, Philippe; Devidal, Jean-Luc

    2014-06-01

    The nature of magmatic sources reflected by isotopic composition of the ocean island basalt (OIB) remains an on-going question in igneous geochemistry. To constrain the magmatic sources for OIB related to the Kerguelen plume activity, we performed detailed microanalytical investigation of the 21.4 Ma picritic basalt (MD109-D6-87) dredged during the “Marion Dufresne” cruise on a seamount between Kerguelen Archipelago and Heard Island. Lead isotope compositions of olivine-hosted melt inclusions and matrix glasses were measured by Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS). We also performed major and trace element microanalyses and mapping of the inclusions and the host olivine phenocrysts by electron microprobe (wavelength-dispersive X-ray spectroscopy, WDS). The observed significant major element (K2O/P2O5, Al2O3/TiO2) and Pb isotope (207Pb/206Pb and 208Pb/206Pb) heterogeneities of parental melts (MgO = 7-10 wt.%) during early high pressure crystallisation stage (200-300 MPa, Fo82-86 mol%), and relative homogeneity at later lower-pressure crystallisation stage (Assimilant” melts during magma residence and transport. Lead isotope composition of the parental basaltic melts was inherited from both heterogeneous mantle and the Kerguelen Plateau crust. High K2O/P2O5 (> 4), Al2O3/TiO2 (> 4) ratios are attributed to assimilation of the plateau basaltic crust (≥ 50 wt.%) by the melts in the magma chamber at palaeodepths from 6 to 9 km. The crustal assimilation may have happened through plagioclase dissolution. The large chemical and isotopic heterogeneity of the parental OIB melts found by in situ microanalyses in this study suggests that the bulk rock chemistry alone cannot provide enough information to constrain the nature of the magmatic sources.

  11. Clinopyroxene-melt element partitioning during interaction between trachybasaltic magma and siliceous crust: Clues from quartzite enclaves at Mt. Etna volcano

    Science.gov (United States)

    Mollo, S.; Blundy, J. D.; Giacomoni, P.; Nazzari, M.; Scarlato, P.; Coltorti, M.; Langone, A.; Andronico, D.

    2017-07-01

    A peculiar characteristic of the paroxysmal sequence that occurred on March 16, 2013 at the New South East Crater of Mt. Etna volcano (eastern Sicily, Italy) was the eruption of siliceous crustal xenoliths representative of the sedimentary basement beneath the volcanic edifice. These xenoliths are quartzites that occur as subspherical bombs enclosed in a thin trachybasaltic lava envelope. At the quartzite-magma interface a reaction corona develops due to the interaction between the Etnean trachybasaltic magma and the partially melted quartzite. Three distinct domains are observed: (i) the trachybasaltic lava itself (Zone 1), including Al-rich clinopyroxene phenocrysts dispersed in a matrix glass, (ii) the hybrid melt (Zone 2), developing at the quartzite-magma interface and feeding the growth of newly-formed Al-poor clinopyroxenes, and (iii) the partially melted quartzite (Zone 3), producing abundant siliceous melt. These features makes it possible to quantify the effect of magma contamination by siliceous crust in terms of clinopyroxene-melt element partitioning. Major and trace element partition coefficients have been calculated using the compositions of clinopyroxene rims and glasses next to the crystal surface. Zone 1 and Zone 2 partition coefficients correspond to, respectively, the chemical analyses of Al-rich phenocrysts and matrix glasses, and the chemical analyses of newly-formed Al-poor crystals and hybrid glasses. For clinopyroxenes from both the hybrid layer and the lava flow expected relationships are observed between the partition coefficient, the valence of the element, and the ionic radius. However, with respect to Zone 1 partition coefficients, values of Zone 2 partition coefficients show a net decrease for transition metals (TE), high-field strength elements (HFSE) and rare earth elements including yttrium (REE + Y), and an increase for large ion lithophile elements (LILE). This variation is associated with coupled substitutions on the M1, M2 and

  12. Inclusions, Porosity, and Fatigue of AlSi10Mg Parts Produced by Selective Laser Melting

    Science.gov (United States)

    Tang, Ming

    dendrite arm spacings in metal powder particles of different diameters were measured and also agree with literature correlations, showing the expected increase in secondary dendrite arm spacing with increasing particle diameter. It is well-known that the fatigue behavior of cast aluminum alloy parts is largely determined by the internal defects, particularly pores and inclusions, such as oxides. This study shows that such imperfections are also present in AlSi10Mg parts produced by SLM, and serve as sites for failure initiation. The effect of hatch spacing and building orientation on tensile and fatigue properties was tested. Similar defects were found both on polished cross-sections and on fracture surfaces. The results imply that the oxide-driven pores dominate the fatigue resistance of the samples in this work. The larger oxide particles which are associated with the crack initiation likely form by oxidation of metal vapor during part manufacture. Residual porosity in parts produced by SLM mainly results from lack-of-fusion, entrapped gas, pores left in powder, evaporation of elements, and collapse of key-holes. Lack-of-fusion porosity is caused by the the insufficient overlap of melt pools in powder bed fusion and is particularly detrimental to fatigue performance due to the stress concentration at the sharp edges of the pores. The third part of this work deals with predicting lack-of-fusion porosity quantitatively by a geometrically-based model and designing processing parameters for build rate improvement without introducing porosity. The inputs into the simulation are hatch spacing, layer thickness, melt-pool cross-sectional area, and hatch rotation angle. Comparison with several data sets from the literature shows that the simulations correctly predict process conditions at which lack-of-fusion porosity becomes apparent, as well as the rate at which porosity increases with changes in process conditions such as beam speed, layer thickness, and hatch spacing

  13. Tracking the Martian Mantle Signature in Olivine-Hosted Melt Inclusions of Basaltic Shergottites Yamato 980459 and Tissint

    Science.gov (United States)

    Peters, T. J.; Simon, J. I.; Jones, J. H.; Usui, T.; Moriwaki, R.; Economos, R.; Schmitt, A.; McKeegan, K.

    2014-01-01

    The Martian shergottite meteorites are basaltic to lherzolitic igneous rocks that represent a period of relatively young mantle melting and volcanism, approximately 600-150 Ma (e.g. [1,2]). Their isotopic and elemental composition has provided important constraints on the accretion, evolution, structure and bulk composition of Mars. Measurements of the radiogenic isotope and trace element concentrations of the shergottite meteorite suite have identified two end-members; (1) incompatible trace element enriched, with radiogenic Sr and negative epsilon Nd-143, and (2) incompatible traceelement depleted, with non-radiogenic Sr and positive epsilon 143-Nd(e.g. [3-5]). The depleted component represents the shergottite martian mantle. The identity of the enriched component is subject to debate, and has been proposed to be either assimilated ancient martian crust [3] or from enriched domains in the martian mantle that may represent a late-stage magma ocean crystallization residue [4,5]. Olivine-phyric shergottites typically have the highest Mg# of the shergottite group and represent near-primitive melts having experienced minimal fractional crystallization or crystal accumulation [6]. Olivine-hosted melt inclusions (MI) in these shergottites represent the most chemically primitive components available to understand the nature of their source(s), melting processes in the martian mantle, and origin of enriched components. We present trace element compositions of olivine hosted melt inclusions in two depleted olivinephyric shergottites, Yamato 980459 (Y98) and Tissint (Fig. 1), and the mesostasis glass of Y98, using Secondary Ionization Mass Spectrometry (SIMS). We discuss our data in the context of understanding the nature and origin of the depleted martian mantle and the emergence of the enriched component.

  14. Glass science tutorial lecture {number_sign}6: The melting of silicate glasses, a review of selected topics

    Energy Technology Data Exchange (ETDEWEB)

    Swarts, E.L.

    1995-03-01

    This report summarizes a two-day lecture given at Westinghouse Hanford Company in March, 1995 and includes the data used in the presentation. Topics included the special needs of a low-level waste vitrification process, glass melting, mechanisms of the formation of foam, glass refining (bubble removal), and homogenization (reduction of chemical heterogeneity to acceptable levels). 96 refs.

  15. Melt inclusions are not reliable proxies for magmatic liquid composition: evidence from crystal-poor andesites and dacites in the Tequila volcanic field, Mexico

    Science.gov (United States)

    Frey, H. M.; Lange, R. A.

    2009-12-01

    A compositional study of >200 melt inclusions in plagioclase and orthopyroxene phenocrysts from six crystal-poor (2-5 vol%) andesite and dacite lavas (60-68 wt% SiO2) from the Tequila volcanic field in the Mexico arc is used to evaluate whether melt inclusions in phenocrysts accurately record magmatic liquid compositions. The crystal-poor andesites and dacites were erupted contemporaneously with crystal-poor rhyolites, and there is a continuum in the SiO2 concentration of the erupted magmas. The liquid line of descent defined by the whole-rock compositions ranges from andesite to rhyolite (60-77 wt% SiO2), as illustrated on Harker diagrams. The crystal-poor andesites and dacites are multiply saturated with five to seven mineral phases (plagioclase + orthopyroxene + titanomagnetite + ilmenite + apatite ± augite ± hornblende), most of which crystallized via degassing during magma ascent (Frey and Lange, 2009). By comparison with phase equilibrium experiments from the literature, it is shown that the vast majority of crystals are phenocrysts and not xenocrysts. Textural evidence of rapid crystal growth includes skeletal, hopper, and swallow-tail morphologies and abundant melt inclusions. The inclusions range in size from a few microns to > 50 μm and occur as isolated pockets and extensive channels that mimic the crystal morphology. Inclusions are typically brown glass, with occasional microphenocrysts of titanomagnetite and/or apatite within or adjacent to the melt inclusions. The compositions of the melt inclusions in the plagioclase and orthopyroxene phenocrysts, when plotted on Harker diagrams, vary systematically from one another and from the liquid line of descent defined by the whole rock compositions of erupted magmas. For example, melt inclusions in plagioclase are systematically depleted in Al2O3 relative to the whole rock samples, whereas those in coexisting orthopyroxenes are systematically enriched in Al2O3. The opposite trend is found for FeO, where it

  16. Distinguishing Mantle Components by Sr and Nd Isotope Analysis of Single Melt Inclusions: Case Study on Italian Potassium-rich Lavas

    Science.gov (United States)

    Koornneef, J.; Nikogosian, I.; van Bergen, M.; Smeets, R.; Bouman, C.; Schwieters, J. B.; Davies, G. R.

    2014-12-01

    Melt inclusions record more extreme isotopic variability than their bulk host lavas and offer the potential to better constrain mantle components that contribute to magmatism. Isotopic analyses of melt inclusions are, however, challenging because of their limited size. To date, Sr and Pb isotope data have been obtained for oceanic islands by application of in situ analysis techniques, either by SIMS or LA-(MC)-ICPMS. Comprehensive studies of inclusions from other settings have yet to be performed. Here, we report the first combined Sr and Nd isotope data on individual melt inclusions from Pliocene-Quaternary K-rich lavas from mainland Italy, obtained using wet chemistry techniques and TIMS analysis. We use newly developed 1013 Ohm resistors mounted in the feedback loop of Faraday cup amplifiers. Compared to default 1011 Ohm resistors, use of 1013 Ohm resistors results in a 10-fold improvement of the signal-to-noise ratio and more precise data when analysing small ion beams (primitive melts that were trapped in the phenocrysts. The isotopic variability is interpreted to be the result of (1) mixing of melts derived from a heterogeneous mantle modified by subduction-related metasomatism, (2) mingling of distinct batches of olivine-bearing magma within a plumbing system, and (3) local assimilation of crustal material. These preliminary data suggest that combined analysis of individual melt inclusions for trace elements and Sr-Nd isotope ratios is a promising tool for identifying distinct components in magma source regions in complex tectonic settings.

  17. Formation Mechanism of Oxide-Sulfide Complex Inclusions in High-Sulfur-Containing Steel Melts

    Science.gov (United States)

    Shin, Jae Hong; Park, Joo Hyun

    2018-02-01

    The [S] content in resulfurized steel is controlled in the range of 200 to 800 ppm to ensure good machinability and workability. It is well known that "MgAl2O4(spinel)+CaS" complex inclusions are formed in molten steel during the ladle refining process, and these cause nozzle clogging during continuous casting. Thus, in the present study, the "Refractory-Slag-Metal-Inclusions (ReSMI)" multiphase reaction model was employed in conjunction with experiments to investigate the influence of slag composition and [S] content in the steel on the formation of oxide-sulfide complex inclusions. The critical [S] and [Al] contents necessary for the precipitation of CaS in the CaO-Al2O3-MgO-SiO2 (CAMS) oxide inclusions were predicted from the composition of the liquid inclusions, as observed by scanning electron microscopy-electron dispersive spectrometry (SEM-EDS) and calculated using the ReSMI multiphase reaction model. The critical [S] content increases with increasing content of SiO2 in the slag at a given [Al] content. Formation mechanisms for spinel+CaS and spinel+MnS complex inclusions were also proposed.

  18. Lead isotopic compositions in olivine-hosted melt inclusions from HIMU basalts and possible link to sulfide components

    Science.gov (United States)

    Yurimoto, Hisayoshi; Kogiso, Tetsu; Abe, Kanshi; Barsczus, Hans G.; Utsunomiya, Atsushi; Maruyama, Shigenori

    2004-08-01

    Pb isotopic compositions of melt inclusions in olivine phenocrysts of lava samples from Mangaia and Rarotonga, Cook-Austral islands, have been determined by secondary ion mass spectrometry. The Pb isotopic compositions of melt inclusions from Rarotonga are consistent with those of bulk rock. On the other hand, Pb isotopic compositions of sulfide-free melt inclusions from Mangaia Island are widely distributed along the join between HIMU (i.e. highly radiogenic Pb) and less radiogenic components. The variation is much wider than that in bulk-rock samples that are invariably end-member HIMU values. In contrast, Pb isotopic compositions of sulfide and carbonate inclusions are restricted to HIMU end-member values. The variations in Pb isotopic ratios can be explained by mixing between the HIMU component and another component with less radiogenic Pb, and suggests that the HIMU component is enriched in sulfide and carbonate phases as well as Pb compared with the less radiogenic component. It seems paradoxical that a sulfide-rich component is associated with highly radiogenic Pb, because sulfides generally have extremely low U/Pb and Th/Pb ratios, which result in quite unradiogenic Pb. Subducted oceanic crust is not a likely source for such a sulfide-rich component because sulfides in subducted crust may not survive dehydration processes in subduction zones, although it can produce highly radiogenic Pb. The association of highly radiogenic Pb and sulfides implies that sulfides and radiogenic Pb in the HIMU source originate from distinct reservoirs. A possible origin of the sulfides is the Earth's core, because the core is the largest sulfur budget in the Earth. The highly radiogenic Pb may originate from subducted oceanic crust which resides at the core-mantle boundary. Alternative source for radiogenic Pb is Ca-perovskite in the lower mantle, which is the main host of incompatible elements in the lower mantle and has high U/Pb and Th/Pb ratios. The core-derived sulfides

  19. Magma storage beneath Grímsvötn volcano, Iceland, constrained by clinopyroxene-melt thermobarometry and volatiles in melt inclusions and groundmass glass

    Science.gov (United States)

    Haddadi, B.; Sigmarsson, O.; Larsen, G.

    2017-09-01

    Basalt eruptions at Grímsvötn volcano, Iceland, are generally of low intensity; however, occasionally, an order of magnitude larger eruptions occur. In order to discuss the reasons for this difference, the degassing budget of S and Cl and crystallization conditions of the eruptive magma were determined from volatile concentration measured in melt inclusion (MI) and groundmass glass and thermobarometry, respectively. Tephra of two of the largest historical eruptions (2011 and 1873) and two much smaller eruptions (2004 and 1823) were investigated. Sulfur and Cl concentrations are higher in groundmass glass of the smaller eruptions due to incomplete outgassing caused by melt quenching in contact with glacial water. Sulfur concentration and degassing budget correlate with erupted magma volumes. Higher volatile concentrations of MI from the larger eruptions reflect important recharge of gas-rich magma from depth. The recharge causes a high-magnitude eruption followed by increased eruption frequency over the following decades. Pressure and temperature estimates of crystallization are obtained through equilibrium clinopyroxene-glass pairs, where crystals adjacent to, and in textural equilibrium with, both groundmass glass and that of MI were measured. An average crystallization pressure of 4 ± 1 kbar corresponding to approximately 15 ± 5 km depth was obtained together with a considerable temperature range, 1065-1175°C. Similar crystallization depths are obtained for the basalt of the 2014-2015 Bárðarbunga rifting event and to a low resistivity layer revealed by magnetotelluric surveys. Therefore, an important magma storage depth is inferred at lower crustal depth above the center of the Iceland mantle plume.

  20. Crustal origin for coupled 'ultra-depleted' and 'plagioclase' signatures in MORB olivine-hosted melt inclusions: evidence from the Siqueiros Transform Fault, East Pacific Rise

    Science.gov (United States)

    Danyushevsky, Leonid; Perfit, Michael; Eggins, Stephen; Falloon, Trevor

    2002-11-01

    Geochemical data from melt inclusions in olivine phenocrysts in a picritic basalt from the Siqueiros Transform Fault on the northern East Pacific Rise provide insights into the petrogenesis of mid-ocean ridge basalts (MORB). The fresh lava contains 10% of olivine phenocrysts (Fo89.3-91.2) and rare, small (<1 mm) plagioclase phenocrysts with subhedral to irregular shapes with a range of compositions (An80-90, An57-63). Melt inclusions in olivine phenocrysts are glassy, generally rounded in shape and vary in size from a few to 200 µm. Although most of the inclusions have compositions that are generally consistent with being representative of parental melts for the pillow-rim glasses, several inclusions are clearly different. One inclusion, which contains a euhedral grain of high-Al, low-Ti spinel, has a composition unlike any melt inclusions previously described from primitive phenocrysts in MORB. It has a very high Al2O3 ( 20 wt%), very low TiO2 ( 0.04 wt%) and Na2O ( 1 wt%) contents, and a very high CaO/Na2O value ( 14). The glass inclusion is strongly depleted in all incompatible elements (La =0.052 ppm Yb =0.34; La/Sm(n) 0.27), but it has large positive Sr and Eu anomalies (Sr/Sr* 30; Eu/Eu* 3) and a negative Zr anomaly. It also has low S (0.015 wt%) and relatively high Cl (180 ppm). We suggest that this unusual composition is a consequence of olivine trapping plagioclase in a hot, strongly plagioclase-undersaturated magma and subsequent reaction between plagioclase and the host olivine producing melt and residual spinel. Two other melt inclusions in a different olivine phenocryst have compositions that are generally intermediate between 'normal' inclusions and the aluminous inclusion, but have even higher CaO and Sr contents. They are also depleted in incompatible elements, but to a lesser degree than the aluminous inclusion, and have smaller Sr and Eu anomalies. Similar inclusions have also been described in high-Fo olivine phenocrysts from Iceland and

  1. Primary carbonatite melt from deeply subducted oceanic crust

    Energy Technology Data Exchange (ETDEWEB)

    Walter, M.J.; Bulanova, G.P.; Armstrong, L.S.; Keshav, S.; Blundy, J.D.; Gudfinnesson, G.; Lord, O.T.; Lennie, A.R.; Clark, S.M.; Smith, C.B.; Gobbo, L.

    2008-07-01

    Partial melting in the Earth's mantle plays an important part in generating the geochemical and isotopic diversity observed in volcanic rocks at the surface. Identifying the composition of these primary melts in the mantle is crucial for establishing links between mantle geochemical 'reservoirs' and fundamental geodynamic processes. Mineral inclusions in natural diamonds have provided a unique window into such deep mantle processes. Here they provide exper8imental and geochemical evidence that silicate mineral inclusions in diamonds from Juina, Brazil, crystallized from primary and evolved carbonatite melts in the mantle transition zone and deep upper mantle. The incompatible trace element abundances calculated for a melt coexisting with a calcium-titanium-silicate perovskite inclusion indicate deep melting of carbonated oceanic crust, probably at transition-zone depths. Further to perovskite, calcic-majorite garnet inclusions record crystallization in the deep upper mantle from an evolved melt that closely resembles estimates of primitive carbonatite on the basis of volcanic rocks. Small-degree melts of subducted crust can be viewed as agents of chemical mass-transfer in the upper mantle and transition zone, leaving a chemical imprint of ocean crust that can possibly endure for billions of years.

  2. Somma-Vesuvius Plinian Eruptions fed by mafic magma: insights from bubbles in melt inclusions

    Science.gov (United States)

    Esposito, R.; Redi, D.; Cannatelli, C.; Danyushevsky, L. V.; Lima, A.; Bodnar, R. J.; De Vivo, B.

    2014-12-01

    MI. This study shows that the CO2-rich fluid phase, which might exsolve from Plinian melts contain a significant amount of H2O. In addition, the first melting temperature of the fluids in the vapor bubble (~ -58ºC) suggests that volatile components, other than CO2, are included in the vapor bubbles.

  3. Boron Isotopes and Trace Elements Analyses on Olivine-Hosted Melt Inclusions from Rucu Pichincha and Pan de Azucar Volcanoes, Ecuadorian arc

    Science.gov (United States)

    Le Voyer, M.; Rose-Koga, E. F.; Eissen, J.; Schiano, P.

    2006-12-01

    Geochemical investigations of olivine-hosted melt inclusions from Rucu Pichincha and Pan de Azucar, which are part of a frontal and a rear volcanic arc in Ecuador, respectively, suggest that these liquids are produced by melting of either a pyroxenite or a peridotitic mantle metasomatised by a melt from a dehydrated slab. Our initial findings show: 1) nepheline normative compositions (SiO2 from 40.5% to 47.5%; Al2O3 from 15.5% to 20 %; and CaO from 7% to 13.5%); 2) B concentrations ranging from 1 to 12 ±2 ppm, and δ^{11}B ranging from 28 ± 4‰ to 1 ±5‰; 3) higher volatile (F, Cl, and S) and incompatible elements (K2O, LREE, Ba) concentrations in Pan de Azucar melt inclusions than in those from Rucu Pichincha. We suggest that 1) two sources are possible: a pyroxenite or a phlogopite-rich metasomatised peridotitic mantle; 2) the variable and negative B isotopic values indicate a contribution of a melt from dehydrated slab (AOC and sediments), which metasomatises the sub-arc mantle before the generation of arc magma; 3) due to the systematic chemical variations, we conclude that the melts from Pan de Azucar represents smaller degree of partial melting of a source very similar to that of the Rucu Pichincha source, but enriched in phlogopite.

  4. The effects of sulfur, silicon, water, and oxygen fugacity on carbon solubility and partitioning in Fe-rich alloy and silicate melt systems at 3 GPa and 1600 °C: Implications for core-mantle differentiation and degassing of magma oceans and reduced planetary mantles

    Science.gov (United States)

    Li, Yuan; Dasgupta, Rajdeep; Tsuno, Kyusei

    2015-04-01

    The partition coefficient of carbon between Fe-rich alloy melt and silicate melt, D C metal /silicate and solubility of C-O-H volatiles in reduced silicate melts are key parameters that need to be quantified in order to constrain the budget and origin of carbon in different planetary reservoirs and subsequent evolution of volatiles in magma oceans (MO) and silicate mantles. In this study, three sets of graphite-saturated experiments have been performed at 3 GPa and 1600 °C to investigate the effects of oxygen fugacity (fO2), sulfur, silicon, and water on the dissolution and partitioning of carbon between Fe-rich alloy melt and silicate melt. The results show that the presence of 0-5 wt% sulfur in alloy melt does not have considerable effect on carbon solubility (∼5.6 wt%) in alloy melt, determined by electron microprobe, whereas the presence of 0-10 wt% silicon decreases the carbon solubility from ∼5.6 wt% to 1.8 wt%. Carbon solubility (11-192 ppm) in silicate melt, determined by SIMS, is strongly controlled by fO2 and the bulk water content. Decreasing log ⁡ fO2 from IW-0.6 to IW-4.7 or increasing bulk water content from 0.07 to 0.55 wt% results in significant increase of carbon solubility in silicate melt. Raman and FTIR spectroscopic analyses of silicate glasses show that the carbon species is mostly methane, which is further confirmed by the strong, positive correlation between the non-carbonate carbon and non-hydroxyl hydrogen in silicate melt. The D C metal /silicate ranging from 180 to 4600 decreases with decreasing fO2 or increasing bulk water in silicate melt. In addition, increasing Si in alloy melt also decreases D C metal /silicate . Our results demonstrate that fO2 and bulk water contents in silicate melt play an important role in determining the fractionation of carbon in planetary MO. A reduced, hydrous MO may have led to a considerable fraction of carbon retained in the silicate mantle, whereas an oxidized, dry MO may have lost almost its

  5. An Ultra-Depleted Mantle Component in the Ontong Java Plateau Revealed by Major, Trace and Volatile Element Abundances in Olivine-Hosted Melt Inclusions

    Science.gov (United States)

    Jackson, M. G.; Cabral, R. A.; Rose-Koga, E. F.; Koga, K. T.; Price, A. A.; Hauri, E. H.; Michael, P. J.

    2014-12-01

    The Ontong Java Plateau (OJP) represents the most voluminous large igneous province (LIP) preserved in the geologic record. The most voluminous volcanic stages of the OJP—the Kroenke and Kwaimbaita stages, which dominate the accessible portions of the plateau—have relatively flat primitive mantle normalized rare earth element (REE) patterns, or spidergrams. With the exception of relatively small volumes of late-stage melts—referred to as the Singgalo stage—that are characterized by slightly enriched REE spidergrams, the volcanic stages that dominated the eruptive history of the OJP exhibit remarkably homogeneous, flat REE patterns. Here we isolate, for the first time, olivine-hosted melt inclusions from OJP. We show that the melt inclusions have two clear populations defined by having distinct trace element characteristics. The first population has relatively flat trace element patterns that are similar to that observed in whole rock lavas from the most voluminous volcanic stages (Kroenke and Kwaimbaita stages) recorded in the OJP. In contrast, a second group of melt inclusions, referred to as UDM (ultra-depleted melt) inclusions, exhibit strikingly depleted REE spidergrams; these trace element patterns are far more depleted than any previously reported lava from OJP. The UDM have unique trace element signatures that preclude an origin by assimilation of hydrothermally-altered oceanic crust or re-melting the depleted mantle source left over after melt extraction during construction of the OJP. We interpret the new UDM compositions to be the result of melting of a previously unrecognized ultra-depleted component hosted in the OJP mantle source.

  6. 40Ar- 39Ar dating of plagioclase grain size separates from silicate inclusions in IAB iron meteorites and implications for the thermochronological evolution of the IAB parent body

    Science.gov (United States)

    Vogel, Nadia; Renne, Paul R.

    2008-02-01

    In order to better constrain the thermochronological evolution of the IAB parent body we performed a 40Ar/ 39Ar age study on individual silicate inclusions of the IAB irons Caddo County, Campo del Cielo, Landes, and Ocotillo. In contrast to earlier studies, several plagioclase separates of different grain sizes and quality grades were extracted from each inclusion to reduce the complexity of the age spectra and study the influence of these parameters on the Ar-Ar ages. In nearly all inclusions we found significantly different Ar-Ar ages among the separates (Caddo County: 4.472 ± 0.02-4.562 ± 0.02 Ga; Campo del Cielo 2: 4.362 ± 0.04-4.442 ± 0.03 Ga; Landes 2: 4.412 ± 0.05-4.522 ± 0.04 Ga; Ocotillo: 4.382 ± 0.04-4.462 ± 0.03 Ga). These ages were calculated using the new 40K decay constant published by [Mundil R., Renne P. R., Min K. and Ludwig K. R. (2006) Resolvable miscalibration of the 40Ar/ 39Ar geochronometer. Eos Trans. AGU 87, Fall Meet. Suppl., Abstract V21A-0543]. The ages did not systematically correlate with the respective grain size of the separate as expected, i.e., smaller grains did not necessarily show younger ages due to later closure to Ar diffusion or easier re-opening of the system in the course of a reheating event compared to larger grains. Based on the large range of Ar-Ar ages we suggest that the individual inclusions are composed of silicate grains from different locations within the IAB parent body. While some grains remained in a hot (deep) environment that allowed Ar diffusion over an extended time period—in some cases combined with grain coarsening—, others cooled significantly earlier (near surface) through the K/Ar blocking temperature. These different grains where brought together during an impact followed by mixing and reassembly of the debris as proposed by Benedix et al. [Benedix G. K., McCoy T. J., Keil K. and Love S. G. (2000) A petrologic study of the IAB iron meteorites: constraints on the formation of the IAB

  7. Zonation of volatile and major elements in basaltic melt inclusions: a snapshot of syn-eruptive processes

    Science.gov (United States)

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

    2011-12-01

    Significant zonation in volatile and major elements has been discovered in olivine-hosted melt inclusions (MIs) from glassy pillow margins from the Siqueiros Fracture Zone [samples previously studied in 1]. For the most part, components that are compatible in olivine (e.g. MgO) are depleted at the edges of the zoned MIs relative to their centers, whereas components that are incompatible in olivine (e.g. Al2O3, SiO2, Na2O, and S) are enriched near the MI edges. H2O and F are exceptions in that they are incompatible, yet in several MIs they are depleted near the olivine-melt boundary. FeO and CaO are also exceptions in that they show complex features attributable to uphill diffusion. Another complexity is the similarity between the shapes of the SiO2 and Na2O profiles (despite significant differences in measured self and tracer diffusivities of these components [2, 3]), suggesting that the diffusion of these components is strongly coupled. All MIs from this sample suite exhibit zoning profiles, as do a suite of MIs from the Galapagos Islands and the inclusions studied in [4], so this feature may be common in rapidly quenched, glassy inclusions. Preservation of strong zonation in the Siqueiros MIs suggests that it formed in response to crystallization of olivine on the walls of the MIs during or just prior to eruption because, based on known diffusion coefficients, such profiles would be erased by diffusion on time scales on the order of 1 hr. The MgO concentration profiles in several Siqueiros MIs have been used to constrain the cooling history of the inclusions using the results of [5]. The profiles are consistent with an initial slow cooling rate followed by a period of more rapid cooling over a total timescale of ~10 min. Given that they are incompatible in olivine, the observed decreases in the concentrations of H2O and F toward the edges of some Siqueiros inclusions could suggest either uphill diffusion of H2O and F (as observed for H2O in [6] in a granitic

  8. Melt, fluid and crystal inclusions in olivine phenocrysts from Kerguelen plume-derived picritic basalts: evidence for interaction with the Kerguelen Plateau lithosphere.

    NARCIS (Netherlands)

    Borisova, A.U.; Nikogosian, I.; Shimizu, N.; Weis, D.; Scoates, J.S.; Touret, J.L.R.; Damasceno, D.

    2002-01-01

    Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picritic basalts dredged during the "Marion Dufresne" MD 109 cruise (Dredge 6) from a seamount located between the Kerguelen Archipelago and Heard Island (Southern Indian Ocean). A two-stage polybaric

  9. Exceptionally high Water, Other Volatile and LILE Concentrations in Olivine-Hosted Melt Inclusions from the Yellowstone Hotspot and Columbia River Flood Basalts

    Science.gov (United States)

    Mukasa, S. B.; Stefano, C.; Leeman, W. P.; Shimizu, N.

    2009-12-01

    The Yellowstone hotspot track, comprising the Snake River Plain (SRP) and Yellowstone Plateau volcanic field, is widely attributed to mantle melting in response to impingement of a deep seated mantle plume on the southwesterly migrating North American Plate. Origin of the mid-Miocene Columbia River Basalts (CRB) and coeval basalts in Oregon and northern Nevada is also attributed by many to effects of the Yellowstone plume, although the lithosphere in that region consists of accreted Permian to Cretaceous oceanic terranes. Propagation of Basin & Range extension into this region raises the possibility that some of these basalts may be melts of lithospheric rather than plume mantle. Other complicating factors such as lateral variation in lithosphere age, composition, and thickness may also contribute. Water and other volatiles (S, F, Cl), as well as major and trace elements have been analyzed in over 150 olivine-hosted melt inclusions from 15 basalt samples taken throughout the CRB-SRP region and covering both lavas contemporaneous with formation of the local caldera - during passage of the North American Plate over the hypothesized plume - and post-caldera lavas erupted well after that event. H2O concentrations as high as 3.3 wt% have been observed in melt inclusions in a syn-caldera Gerritt Basalt at Mesa Falls, Idaho. Some melt inclusions from the Malheur Gorge area of east central Oregon preserve H2O concentrations as high as 4.2 wt%. The highest H2O concentrations are in all cases found in the most primitive melt inclusions, and thus are interpreted as magmatic minima. These values significantly exceed the maximum H2O concentrations observed in Hawaiian melt inclusions of 0.9 wt%. Maximum observed concentrations of other volatiles are 2854 ppm S in the Malheur Gorge, 2606 ppm F in Picture Gorge Basalt (within the CRB), and 1100 ppm F in a Gerritt Basalt flow. High large-ion lithophile-element (LILE) concentrations in these melt inclusions - particularly Ba - and

  10. F, Cl, and S contents of olivine-hosted melt inclusions in mafic dikes and the environmental impact of flood volcanism in the Paraná-Etendeka LIP

    Science.gov (United States)

    Marks, Linda; Trumbull, Robert; Keiding, Jakob; Veksler, Ilya; Wenzel, Thomas; Markl, Gregor; Wiedenbeck, Michael

    2014-05-01

    Large Igneous Provinces (LIPs) have been proposed to trigger mass-extinction events by the release of large quantities of volcanic gases which results in major climatic perturbations causing worldwide ecological stress and collapse. A prerequisite for understanding the proposed link between LIP volcanism and biological crisis is reliable information about the total gas emissions during these events. We present the first estimations of total F, Cl and S emissions from the Paraná-Etendeka LIP in the South Atlantic. Data from this province are of special interest because it is among the world's largest LIPs but is not associated to a mass extinction event. We have determined pre-eruption concentrations of F, Cl and S by in-situ analysis of melt inclusions preserved in olivine phenocrysts from basaltic dikes in the Etendeka province of NW Namibia. The melt inclusions have Mg-rich basaltic bulk compositions with about 8 to 18 wt.% MgO, overlapping the compositional range of the host rocks. A major feature of the melt inclusions is their wide variation in major and minor element concentrations, including F, Cl and S. This is attributed to trapping of variably-mixed melt fractions during crystallization of olivine in the roots of the dike system. Fluorine concentrations vary from about 190 to 450 ppm, Cl from destruction of the ozone layer.

  11. Crystal-Melt Elemental Partitioning in Silicic Magmatic Systems: an Example From the Peach Spring Tuff High-Silica Rhyolite, Southwest USA

    Science.gov (United States)

    Padilla, A. J.; Gualda, G. A. R.

    2014-12-01

    Partition coefficients (Kd) are critical in quantitative models of magmatic evolution. High-SiO2 rhyolites (HSR) are characterized by saturation in numerous phases, thus requiring a comprehensive Kd dataset, including both major and accessory minerals. While a large body of published Kd exists, most studies are limited to small suites of elements (e.g. REE) in few (2-3) minerals, using various methods, bulk compositions, and conditions. We use SEM-EDS and LA-ICP-MS analysis to determine crystal rim and unaltered glass compositions in a single sample of Peach Spring Tuff HSR, which reflect equilibration between crystals and melt at or near the time of eruption. We present Kd for 45 elements in 8 minerals: sanidine, plagioclase, biotite, amphibole, titanite, apatite, zircon, and chevkinite. We show that titanite strongly partitions REE from melt, with significant preference for middle (MREE) over light (LREE) and heavy (HREE) REE. Apatite and amphibole share a similar MREE-enriched pattern but with absolute Kd up to ~2 orders of magnitude lower than titanite; while apatite displays a slight preference for LREE over HREE, amphibole shows a higher affinity for HREE than LREE. Zircon strongly partitions HREE, Hf, and U, with little affinity for LREE. Chevkinite concentrates LREE and Th significantly more than any other phase. Biotite Kd are generally <10, the highest being for transition metals and Ba. Both feldspars show strong preference for Sr, Ba, and Eu. We find that our dataset is largely consistent with published studies that use similar (in-situ) techniques and compositions (HSR). We observe a large variation in other studies that we partly attribute to contamination from inclusions, particularly for compositions measured by whole-crystal methods. Our Kd suggest that accessory minerals play a dominant role in partitioning trace elements, and in particular they collectively control the distribution of REE and high field strength elements. Large ion lithophile

  12. Experimental Modeling of Peridotite Melting with Alkali-Carbonate Fluid at P = 3.9 GPa, T=1250°C

    Science.gov (United States)

    Kostyuk, Anastasia; Gorbachev, Nikolay; Nekrasov, Alexey

    2014-05-01

    The close association of alkaline and ultramafic rocks with carbonatites, apatite and sulfide mineralization, as well as features of the melt compositions, tell us about the mantle source and the importance of alkaline-carbonate fluids in the genesis of these rocks. Experimental modeling of formation of alkali silicate, carbonate and sulfide melts was carried out in the system peridotite-alkaline-carbonate fluid (K, Na)2CO3 with additives of apatite, nickel-containing pyrrhotite, ilmenite and zircon as accessory minerals at P= 3.9 GPa and T=1250°C. Composition of coexisting melts, phase relationships, behavior of titanium, phosphorus, sulfur and zircon have been studied in this system. Liquidus association of phlogopite-clinopyroxene-zircon-X-phase (not diagnosed titanium and phosphorus-containing aluminosilicate phase) cemented by intergranular silicate glass with inclusions of carbonate and sulphide phases at partial (10%) melting of peridotite. Morphology, composition and relations of silicate glass, carbonate and sulfide globules indicate the existence of immiscible silicate, carbonate and sulfide melts at the experimental conditions. The composition of the silicate melt is phonolite, carbonate melt - significantly calcium composition with an admixture of alkali metal and silicate components. Solubility of zircon in silicate melt reached up to 0.8 wt.% of ZrO2, in coexisting carbonate melt - up to 1.5 wt.%. Absence of ilmenite and apatite in the experimental samples due to their high solubility in the coexisting phases. Concentration of TiO2 and P2O5 in silicate melt reached 2 wt. %. The concentration of TiO2 in the carbonate melt up to 1.7 wt.% and P2O5 up to 14 wt.%. The sulfur concentration in these melts does not exceed 0.2 wt.%. Concentrators of titanium and phosphorus among liquidus minerals were X-phase and phlogopite - 8 wt.% TiO2 and up to 3 wt.% P2O5 in the X-phase; up to 6 wt.% TiO2 and up to 2.5 wt.% of P2O5 in the phlogopite. The distribution

  13. Isotope geochemistry and fluid inclusion study of skarns from Vesuvius

    Science.gov (United States)

    Gilg, H.A.; Lima, A.; Somma, R.; Belkin, H.E.; de Vivo, B.; Ayuso, R.A.

    2001-01-01

    We present new mineral chemistry, fluid inclusion, stable carbon and oxygen, as well as Pb, Sr, and Nd isotope data of Ca-Mg-silicate-rich ejecta (skarns) and associated cognate and xenolithic nodules from the Mt. Somma-Vesuvius volcanic complex, Italy. The typically zoned skarn ejecta consist mainly of diopsidic and hedenbergitic, sometimes "fassaitic" clinopyroxene, Mg-rich and Ti-poor phlogopite, F-bearing vesuvianite, wollastonite, gehlenite, meionite, forsterite, clinohumite, anorthite and Mg-poor calcite with accessory apatite, spinell, magnetite, perovskite, baddeleyite, and various REE-, U-, Th-, Zr- and Ti-rich minerals. Four major types of fluid inclusions were observed in wollastonite, vesuvianite, gehlenite, clinopyroxene and calcite: a) primary silicate melt inclusions (THOM = 1000-1050??C), b) CO2 ?? H2S-rich fluid inclusions (THOM = 20-31.3??C into the vapor phase), c) multiphase aqueous brine inclusions (THOM = 720-820??C) with mainly sylvite and halite daughter minerals, and d) complex chloride-carbonate-sulfate-fluoride-silicate-bearing saline-melt inclusions (THOM = 870-890??C). The last inclusion type shows evidence for immiscibility between several fluids (silicate melt - aqueous chloride-rich liquid - carbonate/sulfate melt?) during heating and cooling below 870??C. There is no evidence for fluid circulation below 700??C and participation of externally derived meteoric fluids in skarn formation. Skarns have considerably variable 206Pb/204Pb (19.047-19.202), 207Pb/204Pb (15.655-15.670), and 208Pb/204Pb (38.915-39.069) and relatively low 143Nd/144Nd (0.51211-0.51244) ratios. The carbon and oxygen isotope compositions of skarn calcites (??13CV-PDB = -5.4 to -1.1???; ??18OV-SMOW = 11.7 to 16.4???) indicate formation from a 18O- and 13C-enriched fluid. The isotope composition of skarns and the presence of silicate melt inclusion-bearing wollastonite nodules suggests assimilation of carbonate wall rocks by the alkaline magma at moderate depths (< 5

  14. Reworking of Archean mantle in the NE Siberian craton by carbonatite and silicate melt metasomatism: Evidence from a carbonate-bearing, dunite-to-websterite xenolith suite from the Obnazhennaya kimberlite

    Science.gov (United States)

    Ionov, Dmitri A.; Doucet, Luc S.; Xu, Yigang; Golovin, Alexander V.; Oleinikov, Oleg B.

    2018-03-01

    The Obnazhennaya kimberlite in the NE Siberian craton hosts a most unusual cratonic xenolith suite, with common rocks rich in pyroxenes and garnet, and no sheared peridotites. We report petrographic and chemical data for whole rocks (WR) and minerals of 20 spinel and garnet peridotites from Obnazhennaya with Re-depletion Os isotope ages of 1.8-2.9 Ga (Ionov et al., 2015a) as well as 2 pyroxenites. The garnet-bearing rocks equilibrated at 1.6-2.8 GPa and 710-1050 °C. Some xenoliths contain vermicular spinel-pyroxene aggregates with REE patterns in clinopyroxene mimicking those of garnet. The peridotites show significant scatter of Mg# (0.888-0.924), Cr2O3 (0.2-1.4 wt.%) and high NiO (0.3-0.4 wt.%). None are pristine melting residues. Low-CaO-Al2O3 (≤0.9 wt.%) dunites and harzburgites are melt-channel materials. Peridotites with low to moderate Al2O3 (0.4-1.8 wt.%) usually have CaO > Al2O3, and some have pockets of calcite texturally equilibrated with olivine and garnet. Such carbonates, exceptional in mantle xenoliths and reported here for the first time for the Siberian mantle, provide direct evidence for modal makeover and Ca and LREE enrichments by ephemeral carbonate-rich melts. Peridotites rich in CaO and Al2O3 (2.7-8.0 wt.%) formed by reaction with silicate melts. We infer that the mantle lithosphere beneath Obnazhennaya, initially formed in the Mesoarchean, has been profoundly modified. Pervasive inter-granular percolation of highly mobile and reactive carbonate-rich liquids may have reduced the strength of the mantle lithosphere leading the way for reworking by silicate melts. The latest events before the kimberlite eruption were the formation of the carbonate-phlogopite pockets, fine-grained pyroxenite veins and spinel-pyroxene symplectites. The reworked lithospheric sections are preserved at Obnazhennaya, but similar processes could erode lithospheric roots in the SE Siberian craton (Tok) and the North China craton, where ancient melting residues and

  15. CO2 and H2O Contents of Melt Inclusions from the 1891 Basaltic Balloon Eruption of Foerstner Submarine Volcano, Italy

    Science.gov (United States)

    Balcanoff, J. R.; Carey, S.; Kelley, K. A.; Boesenberg, J. S.

    2016-12-01

    Eruptions that produce basaltic balloon products are an uncommon eruption style only observed in five cases during historical times. Basaltic balloon products form in gas rich shallow submarine eruptions, which produce large hollow clasts with sufficient buoyancy to float on seawater. Foerstner submarine volcano, off the coast of Pantelleria (Italy), erupted with this style in 1891 and is the only eruption where the vent site (250 m water depth) has been studied and sampled in detail with remotely operated vehicles (ROVs). Here, we report Fournier Transform Infrared Spectroscopy (FTIR) and electron microprobe (EMP) analyses of major elements and dissolved volatiles in melt inclusions from olivine and plagioclase phenocrysts picked from highly vesicular clasts recovered from the seafloor. The trachybasaltic melt is enriched in alkalis with notably high phosphorus (1.82-2.38 wt%), and melt inclusions show elevated H2O concentrations of 0.17 to 1.2 wt.% and highly elevated CO2 concentrations of 928 to 1864 ppm. Coexisting matrix glass is completely degassed with respect to carbon dioxide but has variable water contents up to 0.19 %. The maximum carbon dioxide value implies saturation at 1.5 kb, or 4.5 km below the volcano. Trends in the CO2 and H2O data are most compatible with calculated open system degassing behavior. This is consistent with a proposed balloon formation mechanism involving a hybrid strombolian eruption style with the potential accumulation of gas-rich pockets below the vent as gas bubbles moved upwards independent of the low viscosity basaltic melt. Discharge of the gas-rich pockets led to the discharge of meter-sized slugs of magma with large internal vesicles (several tens of centimeters). A subset of these clasts had bulk densities that were lower than seawater, allowing them to rise to the sea surface where they either exploded or became water saturated and sank back to the seafloor.

  16. Effect of layered silicates and reactive compatibilization on structure and properties of melt-drawn HDPE/PA6 microfibrillar composites

    Czech Academy of Sciences Publication Activity Database

    Kelnar, Ivan; Kaprálková, Ludmila; Kratochvíl, Jaroslav; Padovec, Z.; Růžička, M.; Hromádková, Jiřina

    2016-01-01

    Roč. 73, č. 6 (2016), s. 1673-1688 ISSN 0170-0839 R&D Projects: GA ČR(CZ) GA13-15255S Institutional support: RVO:61389013 Keywords : nanocomposite * blend * melt drawing Subject RIV: JI - Composite Materials Impact factor: 1.430, year: 2016

  17. Lower crustal hydrothermal circulation at slow-spreading ridges: evidence from chlorine in Arctic and South Atlantic basalt glasses and melt inclusions

    Science.gov (United States)

    van der Zwan, Froukje M.; Devey, Colin W.; Hansteen, Thor H.; Almeev, Renat R.; Augustin, Nico; Frische, Matthias; Haase, Karsten M.; Basaham, Ali; Snow, Jonathan E.

    2017-12-01

    Hydrothermal circulation at slow-spreading ridges is important for cooling the newly formed lithosphere, but the depth to which it occurs is uncertain. Magmas which stagnate and partially crystallize during their rise from the mantle provide a means to constrain the depth of circulation because assimilation of hydrothermal fluids or hydrothermally altered country rock will raise their chlorine (Cl) contents. Here we present Cl concentrations in combination with chemical thermobarometry data on glassy basaltic rocks and melt inclusions from the Southern Mid-Atlantic Ridge (SMAR; 3 cm year-1 full spreading rate) and the Gakkel Ridge (max. 1.5 cm year-1 full spreading rate) in order to define the depth and extent of chlorine contamination. Basaltic glasses show Cl-contents ranging from ca. 50-430 ppm and ca. 40-700 ppm for the SMAR and Gakkel Ridge, respectively, whereas SMAR melt inclusions contain between 20 and 460 ppm Cl. Compared to elements of similar mantle incompatibility (e.g. K, Nb), Cl-excess (Cl/Nb or Cl/K higher than normal mantle values) of up to 250 ppm in glasses and melt inclusions are found in 75% of the samples from both ridges. Cl-excess is interpreted to indicate assimilation of hydrothermal brines (as opposed to bulk altered rock or seawater) based on the large range of Cl/K ratios in samples showing a limited spread in H2O contents. Resorption and disequilibrium textures of olivine, plagioclase and clinopyroxene phenocrysts and an abundance of xenocrysts and gabbroic fragments in the SMAR lavas suggest multiple generations of crystallization and assimilation of hydrothermally altered rocks that contain these brines. Calculated pressures of last equilibration based on the major element compositions of melts cannot provide reliable estimates of the depths at which this crystallization/assimilation occurred as the assimilation negates the assumption of crystallization under equilibrium conditions implicit in such calculations. Clinopyroxene-melt

  18. Origin of diamond and growth inclusions thereof on evidence derived from physicochemical experiment

    Science.gov (United States)

    Litvin, Yuriy

    2010-05-01

    The conception of carbonate-silicate parent media for the bulk of mantle-derived diamonds (Litvin, 2007) is compatible with a great body of mineralogical data on substances captured in situ by diamonds from their growth melts. Also, the conception is in excellent agreement with the results of physicochemical experiment based on the criterion of diamonds and their inclusions syngenesis. The criterion reveals the behavior of growth melts under diamond formation. The multi-component diamond-forming media are changeable by contents of major and minor components, but bounded by carbonatite compositions. The generalized composition of the parent media, which fragments are included into natural diamonds, is revealed by the multi-component heterogeneous system MgO - CaO - FeO (Fe, Fe2O3) - MnO - NiO (Ni) - Na2O - K2O - Al2O3 - Cr2O3 (Cr) - TiO2 - ZrO2 - SiO2 - P2O5 - CuS (Cu2S) - FeS (Fe2S) - NiS - KCl - NaCl - SiC - Fe3C - CO2 (CO, CH4) - H2O - C. The principal mineralogical responsibility in diamond genesis appertains to carbon solutions in completely miscible melts of the major carbonate and silicate components (the silicate components belong to both peridotite-pyroxenite and eclogite-grospydite parageneses). The growth melts contain the minor components including admixed soluble components and phases (oxides, phosphates, chlorides, compounds of the C - O - H - N fluid system, etc.) as well as coexisting insoluble immiscible solid and liquid phases (sulfides, metals). On the basis of carbonatite (carbonate-silicate) conception, genetic classification of growth inclusions of minerals, melts and fluids in mantle-derived diamonds has been developed (Litvin, 2009). The classification reveals origin of the inclusions by clearing up their physicochemical links both with the major components of carbonate-silicate growth melts and minor soluble and insoluble components and phases which are contained therein. 1. The major silicate, alumina-silicate and carbonate components are

  19. Geochemistry of olivine-hosted melt inclusions in the Baekdusan (Changbaishan) basalts: Implications for recycling of oceanic crustal materials into the mantle source

    Science.gov (United States)

    Choi, Hyun-Ok; Choi, Sung Hi; Schiano, Pierre; Cho, Moonsup; Cluzel, Nicolas; Devidal, Jean-Luc; Ha, Kyoochul

    2017-07-01

    We determined the major and trace element concentrations of olivine-hosted melt inclusions in basalts from the active Baekdusan volcano situated on the border between China and North Korea in order to understand better the nature of the mantle source and the geodynamic processes that gave rise to volcanism at this site. Rehomogenized melt inclusions (after 'Fe-loss' correction) can be divided into three groups: a low-Si alkaline group, a high-Si alkaline group, and a high-Si sub-alkaline group. The low-Si group is composed of picrobasalt to basanite, and the high-Si group consists of (trachy)basalt to basaltic (trachy)andesite. The low-Si group has generally higher TiO2, CaO, and P2O5, but lower Al2O3, Na2O, and K2O contents at a given MgO concentration compared with those in the high-Si group. The CaO and P2O5 contents are positively correlated, indicating the presence of a calcium phosphate, probably tuite [γ-Ca3(PO4)2], in the source. The melt inclusions are enriched in light rare earth elements [(La/Yb)N = 7.8-30.4]. On a primitive-mantle-normalized incompatible element plot, the low-Si group has positive anomalies in Ba and P compared with typical oceanic island basalt (OIB). On the other hand, the high-Si group exhibits remarkable positive anomalies in Eu, Ba, Rb, K, Pb, P, and Ti, implying that K-hollandite and tuite are essential phases in the source. The high-Si subalkaline group has lower abundances of incompatible elements than the high-Si alkaline group, reflecting different degrees of partial melting from the same source. In contrast to OIB, Baekdusan magmatism is characterized by positively fractionated (Zr/Hf)N ratios, and is best approximated by admixture of partial melts derived from both clinopyroxene-rich eclogite and garnet peridotite. Intraplate volcanism in northeastern Asia is closely associated with deep subduction of the Pacific plate. The subducting Pacific slab flattens and stagnates in the mantle transition zone under northeastern Asia

  20. Experimental determination of carbon partitioning between upper mantle minerals and silicate melts: initial results and comparison to trace element partitioning (Nb, Rb, Ba, U, Th, K)

    Science.gov (United States)

    Rosenthal, A.; Hauri, E. H.; Hirschmann, M. M.; Davis, F. A.; Withers, A. C.; Fogel, M. L.

    2012-12-01

    Inventories of C in the mantle and magmatic fluxes of C between the mantle and the Earth's outer envelopes are poorly constrained in part owing to challenges in determining undegassed C concentrations of pristine basalts. Saal et al. [1] proposed that the behavior of Nb could be used as a proxy for C, owing to apparently similar behavior of the two elements in Siqueiros Transform MORB, but higher C/Nb ratios in popping rocks [2] call into question the applicability of the C/Nb proxy. Here, we present experimentally determined carbon partition coefficients (D's) between nominally volatile-free mantle minerals (olivine, OL; orthopyroxene, OPX; clinopyroxene, CPX; garnet, GA) and melts at 0.8-3 GPa, and 1250-1500°C. We conducted piston-cylinder experiments using an olivine-tholeiite + 4 wt% CO2, doped with Nb, Rb, U, Th, and 13C to enhance detection limits. To promote growth of crystals big enough for SIMS analyses, experiments were either long (D12C, but a few have the opposite. Continuous exchange of the liquid (initially rich in 13C) with the graphite capsules (rich in 12C) may yield D's with 13C>12C. D's with 12C>13C are likely owing to either low count rates or comparatively high analytical contamination. Concentrations in minerals vary from 0.20-3.46 ppm for C, 25-176 ppm for H2O, and 0.05-1.21 ppm for F, whereas liquids tend to much higher values (C≤0.9 wt%; H2O≤1.5 wt%; F≤34 ppm; P≤0.25 wt%; S≤43 ppm; Cl≤77 ppm). Resulting D's indicate that C is highly incompatible in all major mantle mineral phases, with D's for OL, OPX and CPX of close to 5x10-4, and for GA ~2.2x10-4. D's for H2O (2x10-4 to ~3x10-2) and F (~2.3x10-3 to ~5.8x10-2) are comparable to those found in previous studies. Trace element partition determinations are in progress, but comparison to previous studies indicates that carbon is significantly more incompatible during mantle melting than Nb, U, or Th, and has behavior approximately similar to Ba. We therefore suggest that

  1. The origin of halide melt phases in layered intrusions, and their significance to platinum-group element mobility

    Science.gov (United States)

    Hanley, J. J.

    2007-12-01

    Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles became increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids, and the partitioning behavior of Cl in fluid-melt systems. Previously unreported, the latest stage volatiles in the layered intrusions were halide melts (slightly hydrous molten salts) of relatively simply composition (NaCl with minor KCl or CaCl2) with salinities in excess of 90 wt% eq. NaCl or CaCl2. These volatiles were trapped at minimum temperatures of 760-800°C, near the eutectic temperature for water-saturated granitic liquid at moderate crustal pressures. Trace element analysis of the salt melt inclusions by laser ablation ICP-MS (ETH Zürich) show that they contain no detectable concentrations of ore and accessory metals. This is in contrast to the earlier, lower salinity volatiles which contain ppm-concentrations of Pt, Pd, As, Bi, Sb as well as abundant S and base metals. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic or felsic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H2O ratios for the parental silicate liquid (> 9 for a granitic residue). Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show

  2. Synchrotron x-ray spectroscopy of EuHN O3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2007-01-01

    A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.

  3. Petrogenetic characteristics of molten slag from the pyrolysis/melting treatment of MSW.

    Science.gov (United States)

    Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki; Motomura, Yoshinobu; Watanabe, Koichiro

    2009-03-01

    MSW slag materials derived from four pyrolysis melting plants in Japan were studied from the viewpoint of petrology in order to discriminate the glass and mineral phases and to propose a petrogenetic model for the formation process of molten slag. Slag material is composed of two major components: melt and refractory products. The melt products that formed during the melting process comprise silicate glass, and a suite of minerals as major constituents. The silicate glass is essentially composed of low and high silica glass members (typically 30% and 50% of SiO(2), respectively), from which minerals such as spinels, melilite, pseudowollastonite, and metallic inclusions have been precipitated. The refractory products consist mainly of pieces of metals, minerals and lithic fragments that survived through the melting process. Investigations demonstrated that the low silica melts (higher Ca and Al contents) were produced at upper levels of high temperature combustion chamber HTCC, at narrower temperature ranges (1250-1350 degrees C), while the high silica melts formed at broader temperature ranges (1250-1450 degrees C), at the lower levels of HTCC. The recent temperature ranges were estimated by using CaOAl(2)O(3)SiO(2) (CAS) ternary liquidus diagram that are reasonably consistent with those reported for a typical combustor. It was also understood that the samples with a higher CaO/SiO(2) ratio (>0.74-0.75) have undergone improved melting, incipient crystallization of minerals, and extensive homogenization. The combined mineralogical and geochemical examinations provided evidence to accept the concept of stepwise generation of different melt phases within the HTCC. The petrogenesis of the melt products may therefore be described as a two-phase melt system with immiscible characteristics that have been successively generated during the melting process of MSW.

  4. Residual glasses and melt inclusions in basalts from DSDP Legs 45 and 46 - Evidence for magma mixing. [Deep Sea Drilling Project

    Science.gov (United States)

    Dungan, M. A.; Rhodes, J. M.

    1978-01-01

    Microprobe analyses of natural glasses in basalts recovered by Legs 45 and 46 of the Deep Sea Drilling Project are reported and interpreted in the context of other geochemical, petrographic and experimental data on the same rocks (Rhodes et al., 1978). Residual glass compositions in the moderately evolved aphyritic and abundantly phyric basalts within each site indicate that none of the units is related to any other or to a common parent by simple fractional crystallization. The compositional trends, extensive disequilibrium textures in the plagioclase phenocrysts and the presence in evolved lavas of refractory plagioclase and olivine phenocrysts bearing primitive melt inclusions provide evidence that magma mixing had a major role in the genesis of the Leg 45 and 46 basalts. The magma parental to these basalts was most likely characterized by high Mg/(Mg + Fe/+2/), CaO/Al2O3, CaO/Na2O and low lithophile concentrations. A mixing model involving incremental enrichment of magmaphile elements by repeated episodes of mixing of relatively primitive and moderately evolved magmas, followed by a small amount of fractionation is consistent with the characteristics of the basalts studied.

  5. Intraplate mantle oxidation by volatile-rich silicic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Audrey M.; Médard, Etienne; Righter, Kevin; Lanzirotti, Antonio

    2017-11-01

    The upper subcontinental lithospheric mantle below the French Massif Central is more oxidized than the average continental lithosphere, although the origin of this anomaly remains unknown. Using iron oxidation analysis in clinopyroxene, oxybarometry, and melt inclusions in mantle xenoliths, we show that widespread infiltration of volatile (HCSO)-rich silicic melts played a major role in this oxidation. We propose the first comprehensive model of magmatism and mantle oxidation at an intraplate setting. Two oxidizing events occurred: (1) a 365–286 Ma old magmatic episode that produced alkaline vaugnerites, potassic lamprophyres, and K-rich calc-alkaline granitoids, related to the N–S Rhenohercynian subduction, and (2) < 30 Ma old magmatism related to W–E extension, producing carbonatites and hydrous potassic trachytes. These melts were capable of locally increasing the subcontinental lithospheric mantle fO2 to FMQ + 2.4. Both events originate from the melting of a metasomatized lithosphere containing carbonate + phlogopite ± amphibole. The persistence of this volatile-rich lithospheric source implies the potential for new episodes of volatile-rich magmatism. Similarities with worldwide magmatism also show that the importance of volatiles and the oxidation of the mantle in intraplate regions is underestimated.

  6. F, Cl, and S concentrations in olivine-hosted melt inclusions from mafic dikes in NW Namibia and implications for the environmental impact of the Paraná-Etendeka Large Igneous Province

    Science.gov (United States)

    Marks, Linda; Keiding, Jakob; Wenzel, Thomas; Trumbull, Robert B.; Veksler, Ilya; Wiedenbeck, Michael; Markl, Gregor

    2014-04-01

    Large Igneous Provinces (LIPs) have been proposed to trigger mass-extinction events by the release of large quantities of volcanic gases which results in major climatic perturbations causing worldwide ecological stress and collapse. A prerequisite for understanding the proposed link between LIP volcanism and biological crisis is reliable information about the total gas emissions during these events. In this paper we present the first estimations of total F, Cl and S emissions from the Paraná-Etendeka LIP in the South Atlantic. Data from this province are of special interest because it is among the world's largest LIPs but is not associated with a mass extinction event. We have determined pre-eruption concentrations of F, Cl and S by in situ analysis of melt inclusions preserved in olivine phenocrysts from basaltic dikes in the Etendeka province of NW Namibia. The melt inclusions have Mg-rich basaltic bulk compositions with about 8 to 18 wt.% MgO, overlapping the compositional range of the host rocks. A major feature of the melt inclusions is their wide variation in major and minor element concentrations, including F, Cl and S. This is attributed to trapping of variably-mixed melt fractions during crystallization of olivine in the roots of the dike system. Fluorine concentrations vary from about 190 to 450 μg/g, Cl from destruction of the ozone layer.

  7. Constraining the H2O and CO2 Contents of Basaltic Arc Magmas from Melt Inclusions: Diffusive H Loss and Shrinkage Bubble Formation, and Implications for the CO2 Contents of Primary Melts

    Science.gov (United States)

    Wallace, P. J.; Walowski, K. J.; Aster, E. M.

    2016-12-01

    The volatiles H2O and CO2 play a major role in arc magmatism, and tracking their return flux from the subducted slab to the Earth's surface is important for understanding global geochemical cycles. Melt inclusions (MIs) are a commonly used tool for measuring the concentrations of volatiles in magmas. However, recent studies have shown that MIs are imperfect storage containers that can lose H by diffusion through the mineral host and CO2 due to formation of a vapor bubble in the inclusion. Here, we use data for MIs from primitive basaltic magmas in the Lassen region of the Cascade arc [1] to show how post-entrapment processes can be distinguished from magmatic variability. Using the highest measured H2O from MIs at each volcanic center, we use correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) to demonstrate that primary geochemical variability results from variable addition of a hydrous subduction component to the mantle wedge. However, volcanic centers in the Lassen region and at nearby Mt. Shasta with the highest Sr/Nd, and therefore largest amount of a subduction component, have low H2O/Ce, suggesting that MIs in the most H2O-rich magmas were affected by diffusive H loss after trapping. For CO2 in MIs, we correct for the loss of CO2 to a vapor bubble formed by post-entrapment crystallization and thermal contraction [2]. The results suggest minimum magmatic values of 1500-6000 ppm CO2, but these likely reflect the depths of stalling and crystallization in the crust rather than primary magma values. Our results are similar to estimates for other arc volcanoes that range up to 4000 ppm CO2 (Fuego [3]), 3800 ppm (Klyuchevskoy [4]) and 7000 ppm (Jorullo [2]). The highest of these values overlap with the estimate of 0.6 - 1.3 wt% CO2 in primary arc magmas inferred from arc volcano CO2 emissions [5]. [1] Walowski et al. 2016, EPSL; [2] Aster et al. 2016, JVGR; [3] Moore et al. 2015, Am. Min.; [4] Mironov et al. 2015, EPSL; [5] Wallace 2005, JVGR.

  8. Molybdenum Valence in Basaltic Silicate Melts

    Science.gov (United States)

    Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

    2010-03-01

    XANES analyses of molybdenum were performed on basaltic glass run products experiments conducted at varying P, T, and fO2. The transition from Mo6+ to Mo4+ occurs around IW, only Mo4+ remains at IW-1 and below, conditions relevant to core formation.

  9. Interpreting the I-Xe system in individual silicate grains from Toluca IAB

    Science.gov (United States)

    Pravdivtseva, O. V.; Meshik, A. P.; Hohenberg, C. M.; Petaev, M.

    2009-12-01

    Detailed isotopic and mineralogical studies of silicate inclusions separated from a troilite nodule of the Toluca IAB iron meteorite reveal the presence of radiogenic 129Xe in chlorapatite, plagioclase, perryite, and pyroxene grains. Subsequent I-Xe studies of 32 neutron-irradiated pyroxene grains indicate that high-Mg and low-Mg pyroxenes have distinctive I-Xe signatures. The I-Xe system in high-Mg pyroxenes closed at 4560.5 ± 2.4 Ma, probably reflecting exsolution of silicates from the melt, while the low-Mg pyroxenes closed at 4552.0 ± 3.7 Ma, 8.5 Ma later, providing a means for determining the cooling rate at the time of exsolution. If the host Toluca graphite-troiliterich inclusion formed after the breakup and reassembly of the IAB parent body as has been suggested, the I-Xe ages of the high-Mg pyroxenes separated from this inclusions indicate that this catastrophic impact occurred not later than 4560.5 Ma, 6.7 Ma after formation of CAIs. The cooling rate at the time of silicates exsolution in Toluca is 14.5 ± 10.0 °C/Ma.

  10. Lattice thermal conductivity of silicate glasses at high pressures

    Science.gov (United States)

    Chang, Y. Y.; Hsieh, W. P.

    2016-12-01

    Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

  11. Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

    Science.gov (United States)

    Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

    2017-08-01

    Subduction of carbonated crust is widely believed to generate a flux of carbon into the base of the continental lithospheric mantle, which in turn is the likely source of widespread volcanic and non-volcanic CO2 degassing in active tectonic intracontinental settings such as rifts, continental margin arcs and back-arc domains. However, the magnitude of the carbon flux through the lithosphere and the budget of stored carbon held within the lithospheric reservoir are both poorly known. We provide new constraints on the CO2 budget of the lithospheric mantle below the Pannonian Basin (Central Europe) through the study of a suite of xenoliths from the Bakony-Balaton Highland Volcanic Field. Trails of secondary fluid inclusions, silicate melt inclusions, networks of melt veins, and melt pockets with large and abundant vesicles provide numerous lines of evidence that mantle metasomatism affected the lithosphere beneath this region. We obtain a quantitative estimate of the CO2 budget of the mantle below the Pannonian Basin using a combination of innovative analytical and modeling approaches: (1) synchrotron X-ray microtomography, (2) NanoSIMS, Raman spectroscopy and microthermometry, and (3) thermodynamic models (Rhyolite-MELTS). The three-dimensional volumes reconstructed from synchrotron X-ray microtomography allow us to quantify the proportions of all petrographic phases in the samples and to visualize their textural relationships. The concentration of CO2 in glass veins and pockets ranges from 0.27 to 0.96 wt.%, higher than in typical arc magmas (0-0.25 wt.% CO2), whereas the H2O concentration ranges from 0.54 to 4.25 wt.%, on the low end for estimated primitive arc magmas (1.9-6.3 wt.% H2O). Trapping pressures for vesicles were determined by comparing CO2 concentrations in glass to CO2 saturation as a function of pressure in silicate melts, suggesting pressures between 0.69 to 1.78 GPa. These values are generally higher than trapping pressures for fluid inclusions

  12. Tailoring polymer properties with layered silicates

    Science.gov (United States)

    Xu, Liang

    Polymer layered silicate nanocomposites have found widespread applications in areas such as plastics, oil and gas production, biomedical, automotive and information storage, but their successful commercialization critically depends on consistent control over issues such as complete dispersion of layered silicate into the host polymer and optimal interaction between the layered silicates and the polymers. Polypropylene is a commercially important polymer but usually forms intercalated structures with organically modified layered silicate upon mixing, even it is pre-treated with compatibilizing agent such as maleic anhydride. In this work, layered silicate is well dispersed in ammonium modified polypropylene but does not provide sufficient reinforcement to the host polymer due to poor interactions. On the other hand, interactions between maleic anhydride modified polypropylene and layered silicate are fine tuned by using a small amount of maleic anhydride and mechanical strength of the resultant nanocomposites are significantly enhanced. In particular, the melt rheological properties of layered silicate nanocomposites with maleic anhydride functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the maleic anhydride treated polypropylene based nanocomposites exhibit solid-like linear dynamic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized polypropylene based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interaction in maleic anhydride functionalized nanocomposites, which facilitates formation of a long-lived silicate network mediated by physisorbed polymer chains. Further, the transient shear stress of the maleic anhydride functionalized nanocomposites in start-up of steady shear is a function of the shear

  13. The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure

    Science.gov (United States)

    Barnes, S. J.

    1986-01-01

    The Cr distributions for a synthetic silicate melt equilibrated with bronzitic orthopyroxene and chromite spinel between 1334 and 1151 C over a range of oxygen fugacities between the nickel-nickel oxide and iron-wuestite buffers are studied. The occurrence, chemical composition, and structure of the orthopyroxene-silicate melt and the spinel-silicate melt are described. It is observed that the Cr content between bronzite and the melt increases with falling temperature along a given oxygen buffer and decreases with falling oxygen fugacity at a given temperature; however, the Cr content of the melt in equilibrium with spinel decreases with falling temperature and increases with lower oxygen fugacity.

  14. Fluid inclusion studies of ejected nodules from plinian eruptions of Mt. Somma-Vesuvius

    Science.gov (United States)

    Belkin, H.E.; de Vivo, B.

    1993-01-01

    Mt. Somma-Vesuvius (Naples, Italy) has erupted potassium-rich and silica-undersaturated products during a complicated history of plinian and non-plinian events. Coarse-grained cognate nodules are commonly found in the pyroclastics and are upper crustal in origin. We examined cumulate and subeffusive nodules from the 3800 y.B.P. Avellino. A.D. 79 Pompei, and A.D. 472 Pollena eruptions. Silicate-melt and liquid-vapor fluid inclusion studies in clinopyroxene from both types of nodules have been used to assess the fluids attending crystallization and to place constraints on the pressure and temperature of nodule formation. Thermometric and volumetric data from primary and pseudosecondary CO2-H2O and CO2 and coeval silicate-melt fluid inclusions indicate that they were trapped at a pressure of ???1 to ???2.5 kbar at ???1200??C. This suggests a crystallization depth of ???4 to ???10 km. The H2O-bearing fluid inclusions are abundant from plinian eruptions in contrast to non-plinian eruptions where H2O-bearing fluid inclusions were rare. The presence of primary H2O-CO2 fluid inclusions indicates that an immiscible, supercritical H2O-CO2 fluid was in the nodule-forming environment. The H2O-bearing fluid inclusions in plinian nodules may record a higher pre-eruptive H2O content in the bulk magma that is dramatically reflected in the eruption dynamics. ?? 1993.

  15. EVIDENCE FOR TWO-STAGE MELTING IN THE BRAHIN PALLASITE PARENT BODY

    Science.gov (United States)

    Sonzogni, Y.; Devouard, B.; Provost, A.; Devidal, J.

    2009-12-01

    We identified two types of melt inclusions in olivine crystals from the Brahin main-group pallasite, similar to those described in [1, 2]. Both types are abundant and coexist within a same olivine grain. The first type are isolated, 1-10 µm large, elongated to tubular, and oriented along the [001] axis of the olivine host (as determined by EBSD). These inclusions are phosphate-rich, typically made of stanfieldite, a bubble, often phosphoran olivine (21-32 wt% P2O5), plus occasional minute phases including metal-sulfide blebs and daubreelite. These isolated inclusions look primary, but microprobe mapping of P revealed the scars of former fractures joining these inclusions. The second type are 2-dimensional arrays of abundant chromite inclusions (phase as olivine based on its steochiometry, (Mg,Fe,Ca)4-x(Si1-xPx)2O8, and its structure (as evidenced by EBSD). The value of 32 wt% P2O5 is the highest of all P-rich olivines reported so far [3, 4, 5, 6]. Such high P contents suggest an extended solid solution between olivine and chopinite [7]. Melt inclusions in Brahin seem to record two distinct HT events. According to phase diagrams, a single silicate melt enriched in P might be sufficient to form these phosphate-rich inclusions at T chromite melt and a metal-sulfide one. The abundance of chromite requires temperatures > ca. 1800°C in order to accommodate Cr in the silicate melt. It seems likely that these secondary inclusions result from a shock that took place while the stony-iron assembly of the Brahin pallasite was already formed. On the other hand, the lack of metal-sulfide associated with the phosphate-rich inclusions may imply that the iron part of the Brahin pallasite was not present when these inclusions were formed. References: [1] Buseck P.R. 1977. Geochimica and Cosmochimica Acta 41:711-740. [2] Koviazin S.V. and Podgornykh N.M. 2006. 37th Lunar and Planetary Science Conference pp. 1235-1236. [3] Buseck P.R. and Clark J. 1984. Mineralogical Magazine 48

  16. Single and multiphase inclusions in metapelitic garnets of the Rhodope Metamorphic Province, NE Greece.

    Science.gov (United States)

    Mposkos, Evripidis; Perraki, Maria; Palikari, Sarra

    2009-08-01

    Single and multiphase inclusions in garnet porphyroblasts from the diamond-bearing pelitic gneisses were studied by means of combined Raman Spectroscopy and Electron Scanning Microscopy (SEM/EDX). They are either randomly distributed or with preferred orientation within the garnet host and their dimensions vary from less than 5 up to 60 microm. In the single-phase inclusions quartz, rutile, kyanite and graphite dominate. Biotite, zircon, apatite, monazite and allanite are also common. Two types of multiphase inclusions were recognized, hydrous silicate (Type I) and silicate-carbonate (Type II) ones. The carbon-bearing multiphase inclusions predominantly consist of Mg-siderite+graphite+CO(2)+muscovite+quartz formed by a high density carboniferous fluid rich in Fe, Mg, Si and less Ca, Mn, Al and K trapped in the growing garnet in a prograde stage of metamorphism at high-pressure (HP) conditions. The carbon-free multiphase inclusions predominantly consist of biotite+quartz+rutile+/-kyanite+muscovite formed through decompression-dehydration/melting reactions of pre-existing phengite. Single and multiphase inclusions are characterized by polygonal to negative crystal shape formed by dissolution-reprecipitation mechanism between the garnet host and the inclusions during the long lasting cooling period (>100 Ma) of the Kimi Complex.

  17. Multiphase Mineral Inclusions in Ferrikaersutite Megacrysts : Implications for Postmagmatic Alteration of the Kaersutite Host

    Directory of Open Access Journals (Sweden)

    Sobhi Nasir

    2009-06-01

    Full Text Available Primary and secondary multiphase mineral inclusions, without preserved fluid are found in ferrikaersutite megacrysts from the Cenozoic Harrat Ash Sham Volcanic Field in  ٍSyria. Mineral phases in the inclusions are magnetite, hematite, pseudobrookite and pyrrhotite. The kaersutite megacrysts formed from a hydrous basanitic melt at depth. Silicate minerals in the inclusions are olivine, plagioclase, phlogopite, hornblende, clino- and orthopyroxene. These silicate minerals crystallized from melt penetration and infillings of veins and fractures in the kaersutite. Magnetite and pyrrhotite inclusion formed through magmatic crystallization which was followed by low temperature alteration and re-equilibration. Late stage  near-surface alteration resulted in the formation of hematite,  limonite  and fine-grained weathering products  which comprise high-Fe-Si-,  Si-Mg-Al-,  Si-Fe-Al-,  Si-Al- and Si-Ti-Al-Fe-Ca-rich alterations. The composition of these late stage alteration products was governed by low-temperature post-magmatic alteration of kaersutite along cleavage planes and fractures.

  18. Evolution of carbonated melt to alkali basalt in the South China Sea

    Science.gov (United States)

    Zhang, Guo-Liang; Chen, Li-Hui; Jackson, Matthew G.; Hofmann, Albrecht W.

    2017-01-01

    CO2 is considered to play a key role in the melting of the deep upper mantle, and carbonated silicate melts have been widely predicted by partial melting experiments to exist at mantle depths of greater than 80 km. However, such melts have not been shown to exist in nature. Thus, the relationship between CO2 and the origin of silicate melts is highly speculative. Here we present geochemical analyses of rocks sampled from the South China Sea, at the Integrated Ocean Discovery Program Site U1431. We identify natural carbonated silicate melts, which are enriched in light rare earth elements and depleted in Nb and Ta, and show that they were continuously transformed to alkali basalts that are less enriched in light rare earth elements and enriched in Nb and Ta. This shows that carbonated silicate melts can survive in the shallow mantle and penetrate through the hot asthenosphere. Carbonated silicate melts were converted to alkali basaltic melts through reactions with the lithospheric mantle, during which precipitation of apatite accounts for reduction of light rare earth elements and genesis of positive Nb-Ta anomalies. We propose that an extremely thin lithosphere (less than 20 km in the South China Sea) facilitates extrusion of the carbonated silicate melts, whereas a thickened lithosphere tends to modify carbonated silicate melt to alkali basalt.

  19. Fluid Inclusions in Extraterrestrial Samples Fact or Fiction?

    Science.gov (United States)

    Bodnar, R. J.; Zolensky, M. E.; Gibson, E. K.

    2000-01-01

    Over the years there have been numerous reports of liquid inclusions in meteorites. Roedder reviews the reported occurrences of liquid inclusions in meteorites and states that "silicate-melt inclusions are expectable and apparently ubiquitous, but the presence of actual liquid inclusions (i.e., with moving bubbles at room temperature) would seem almost impossible." The reason for this conclusion is that meteorites (presumably) form in space at high temperatures and very low pressures where liquid water (or carbon dioxide) is not stable. Perhaps the most infamous report of fluid inclusions in meteorites was that of Warner et al. In that study, the authors reported the presence of two-phase, liquid-vapor inclusions in a diogenite from Antarctica. This report of fluid inclusions generated considerable interest in the meteorite community, and caused many to question existing models for the origin of the diogenites. This interest was short-lived however, as later investigations of the same samples showed that the inclusions were most likely artifacts. Rudnick et al. showed that many of the inclusions in meteorites prepared at the Johnson Space Center contained a fluid that fluoresced strongly under the laser beam on the Raman microprobe. They interpreted this to indicate that the inclusions contained Almag oil used in the preparation of thin sections. Presumably, the Almag oil entered empty vesicles along fractures that were opened intermittently during cutting. Here, the occurrence of unambiguous fluid inclusions that could not have been introduced during sample preparation are described in samples from two different extraterrestrial environments. One environment is represented by the SNC (martian) meteorites ALH 84001 and Nakhla. The second environment is represented by the Monahans 1998 meteorite that fell recently in the USA.

  20. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  1. Partitioning of rare earth elements between hibonite and melt and implications for nebular condensation of the rare earth elements

    Science.gov (United States)

    Drake, Michael J.; Boynton, William V.

    1988-01-01

    The effect of oxygen fugacity on the partitioning of REEs between hibonite and silicate melt is investigated in hibonite-growth experiments at 1470 C. The experimental procedures and apparatus are described, and the results are presented in extensive tables and graphs and characterized in detail. The absolute activity coefficients in hibonite are estimated as 330 for La, 1200 for Eu(3+), and 24,000 for Yb. It is inferred that ideal solution behavior cannot be assumed when calculating REE condensation temperatures for (Ca, Al)-rich inclusions in carbonaceous chondrites.

  2. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...... silicate nanocomposites and their structure-properties relationship. In the first part of the thesis, thermoplastic layered silicates were obtained by extrusion. Different modification methods were tested to observe the intercalation treatment effect on the silicate-modifier interactions. The silicate...

  3. Evolving magma storage conditions beneath Mount St. Helens inferred from chemical variations in melt inclusions from the 1980-1986 and current (2004-2006) eruptions: Chapter 33 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    Science.gov (United States)

    Blundy, Jon; Cashman, Katharine V.; Berlo, Kim; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    2008-01-01

    Major element, trace element, and volatile concentrations in 187 glassy melt inclusions and 25 groundmass glasses from the 1980-86 eruption of Mount St. Helens are presented, together with 103 analyses of touching FE-Ti oxide pairs from the same samples. These data are used to evaluate the temporal evolution of the magmatic plumbing system beneath the volcano during 1980-86 and so provide a framework in which to interpret analyses of melt inclusions from the current (2004-2006) eruption. Major and trace element concentrations of all melt inclusions lie at the high SiO2 end of the data array defined by eruptive products of the late Quaternary age from Mount St. Helens. For several major and trace elements, the glasses define a trend that is oblique to the whole-rock trend, indicating that different mineral assemblages were responsible for the two trends. The whole-rock trend can be ascribed to differentiation of hydrous basaltic parents in a deep-seated magma reservoir, probably at depths great enough to stabilize garnet. In contrast, the glass trends were generated by closed-system crystallization of the phenocryst and microlite mineral assemblages at low pressures. The dissolved H2O content of the melt inclusions from 1980-86, as measured by the ion microprobe, ranges from 0 to 6.7 wt. percent, with the highest values obtained from the plinian phase of May 18, 1980. Water contents decrease with increasing SiO2, consistent with decompression-driven crystallization. Preliminary data for dissolved CO2 in melt inclusions from the May 18 plinian phase from August 7, 1980, indicate that XH2O in a vapor phase was approximately constant at 0.80, irrespective of H2O content, suggestive of closed-system degassing with a high bubble fraction or gas streaming through the subvolcanic system. Temperature and f

  4. Infrared spectroscopy and hydrogen isotope geochemistry of hydrous silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Epstein, S.; Stolper, E.

    1992-01-01

    The focus of this project is the combined appication of infrared spectroscopy and stable isotope geochemistry to the study of hydrogen-bearing species dissolved in silicate melts and glasses. We are conducting laboratory experiments aimed at determining the fractionation of D and H between melt species (OH and H{sub 2}O) and hydrous vapor and the diffusivities of these species in glasses and melts. Knowledge of these parameters is critical to understanding the behavior of hydrogen isotopes during igneous processes and hydrothermal processes. These results also could be valuable in application of glass technology to development of nuclear waste disposal strategies.

  5. CO2-SO3-rich (carbonate-sulfate) melt/fluids in the lithosphere beneath El Hierro, Canary Islands.

    Science.gov (United States)

    Oglialoro, E.; Ferrando, S.; Malaspina, N.; Villa, I. M.; Frezzotti, M. L.

    2015-12-01

    Mantle xenoliths from the island of El Hierro, the youngest of the Canary Islands, have been studied to characterize fluxes of carbon in the lithosphere of an OIB volcanism region. Fifteen xenoliths (4-10 cm in diameter) were collected in a rift lava flow (15-41 ka) at a new xenolith locality in El Julan cliff (S-SW of the island). Peridotites consist of protogranular to porphyroblastic spinel harzburgites, lherzolites, and subordinate dunites. One spinel clinopyroxenite, and one olivine-websterite were also analyzed. Ultramafic xenoliths were classified as HEXO (harzburgite and dunite with exsolved orthopyroxene), HLCO (harzburgite and lherzolite containing orthopyroxene without visible exsolution lamellae), and HTR (transitional harzburgite with exsolved orthopyroxene porphyroclasts, and poikilitic orthopyroxene) following [1]. While HLCO and HTR peridotites contain mostly CO2 fluid inclusions, HEXO peridotites preserve an early association of melt/fluid inclusions containing dominantly carbonate/sulfate/silicate glass, evolving to carbonate/sulfate/phosphate/spinel aggregates, with exsolved CO2 (± carbonates, anhydrite and H2O). Chemical and Raman analyses identify dolomite, Mg-calcite, anhydrite, sulfohalite [Na6(SO4)2FCl] (± other anhydrous and hydrous alkali-sulfates), apatite, and Cr-spinel in the inclusions. Sulfides are noticeably absent. The microstructure and chemical composition of the metasomatic fluids indicate that the peridotites were infiltrated by a carbonate-sulfate-silicate melt/fluid enriched in CO2, H2O, and P. A mantle origin for this fluid is supported by high densities of CO2inclusions (> 1g/cm3), determined by Raman microspectroscopy and cross-checked by microthermometry. Consequently, El Julan peridotites provide the first evidence for liberating oxidized C and S fluxes from the Earth lithosphere in an OIB source region, and suggest that oxidation of sulfide to sulfate can occur during small-degree partial melting of the upper mantle

  6. Anthropogenic Origin of Siliceous Scoria Droplets from Pleistocene and Holocene Archeaological Sites in Northern Syria

    DEFF Research Database (Denmark)

    Thy, Peter; Willcox, George; Barfod, Gry

    2015-01-01

    to archaeological sites. We therefore conclude that melting of building earth in ancient settlements can occur during !res reaching modest temperatures. There is no evidence to suggest that siliceous scoria droplets result from very high temperature melting of soil and are the result of a cosmic event....

  7. Carbonatite melt-peridotite interaction at 5.5-7.0 GPa: Implications for metasomatism in lithospheric mantle

    Science.gov (United States)

    Sokol, Alexander G.; Kruk, Alexey N.; Chebotarev, Dimity A.; Palyanov, Yury N.

    2016-04-01

    Interaction between carbonatite melt and peridotite is studied experimentally by melting samples of interlayered peridotite-carbonatite-peridotite in graphite containers at 1200-1350 °C and 5.5-7.0 GPa in a split-sphere multianvil apparatus. Starting compositions are lherzolite and harzburgite, as well as carbonatite which may form in the upper part of a slab or in a plume-related source. Most experimental runs were of 150 h duration in order for equilibrium to be achieved. The interaction produced carbonatitic melts with low SiO2 (≤ 7 wt.%) and high alkalis. At 1200 °C, melt-peridotite interaction occurs through Mg-Ca exchange, resulting in elimination of orthopyroxene and crystallization of magnesite and clinopyroxene. At 1350 °C hybridization of the carbonatite and magnesite-bearing peridotite melts occurred with consumption of clinopyroxene and magnesite, and crystallization of orthopyroxene at MgO/CaO ≥ 4.3. The resulting peridotite-saturated melt has Ca# (37-50) depending on primary carbonatite composition. Compositions of silicate phases are similar to those of high-temperature peridotite but are different from megacrysts in kimberlites. CaO and Cr2O3 changes in garnet produced from the melt-harzburgite interaction at 1200 and 1350 °C perfectly match the observed trend in garnet from metasomatized peridotite of the Siberian subcontinental lithospheric mantle. K-rich carbonatite melts equilibrated with peridotite at 5.5-7.0 GPa and 1200-1350 °C correspond to high-Mg inclusions in fibrous diamond. Carbonatite melt is a weak solvent of entrained xenoliths and therefore cannot produce kimberlitic magma if temperatures are ~ 1350 °C on separation from the lithospheric peridotite source and ~ 1000 °C on eruption.

  8. Partitioning of siderophile elements between metallic liquids and silicate liquids under high-pressure and temperature

    Science.gov (United States)

    Nakatsuka, A.; Urakawa, S.

    2010-12-01

    High-pressure metal-silicate element partitioning studies have shown the possibility that the mantle abundance of siderophile elements is consistent with core-mantle equilibration at high pressures and high temperatures. Equilibrium conditions are, however, still under debates partly due to the uncertainty of partition coefficients, which vary not only with pressure, temperature and oxygen fugacity but also with composition. We have carried out partitioning experiments of siderophile elements between liquid metal and ultramafic silicate liquid at high pressure to evaluate the effects of composition on the partition coefficients. Partitioning experiments were conducted by KAWAI-type high pressure apparatus. We used natural peridotite and Fe alloy as starting materials and they were contained in graphite capsule. The quenched samples were examined by electron microprobe. Quenched textures indicate that metallic melts coexisted with silicate melts during experiment. The metallic melt contained 7-9 wt% of C. Oxygen fugacity varied from IW-3 to IW-1 in associated with the composition of the starting material. At the reduced condition, silicate melt was enriched in SiO2 compared to peridotite because of the oxidation of Si in metallic melts. When oxygen fugacity is close to IW buffur, silicate melt was enriched in FeO due to the oxidation of metallic Fe and it had high NBO/T = 3.5-4. The partition coefficients D for Co, Ni and Fe were dependent on oxygen fugacity as well as the chemical compositions.

  9. A dearth of intermediate melts at subduction zone volcanoes and the petrogenesis of arc andesites.

    Science.gov (United States)

    Reubi, Olivier; Blundy, Jon

    2009-10-29

    Andesites represent a large proportion of the magmas erupted at continental arc volcanoes and are regarded as a major component in the formation of continental crust. Andesite petrogenesis is therefore fundamental in terms of both volcanic hazard and differentiation of the Earth. Andesites typically contain a significant proportion of crystals showing disequilibrium petrographic characteristics indicative of mixing or mingling between silicic and mafic magmas, which fuels a long-standing debate regarding the significance of these processes in andesite petrogenesis and ultimately questions the abundance of true liquids with andesitic composition. Central to this debate is the distinction between liquids (or melts) and magmas, mixtures of liquids with crystals, which may or may not be co-genetic. With this distinction comes the realization that bulk-rock chemical analyses of petrologically complex andesites can lead to a blurred picture of the fundamental processes behind arc magmatism. Here we present an alternative view of andesite petrogenesis, based on a review of quenched glassy melt inclusions trapped in phenocrysts, whole-rock chemistry, and high-pressure and high-temperature experiments. We argue that true liquids of intermediate composition (59 to 66 wt% SiO(2)) are far less common in the sub-volcanic reservoirs of arc volcanoes than is suggested by the abundance of erupted magma within this compositional range. Effective mingling within upper crustal magmatic reservoirs obscures a compositional bimodality of melts ascending from the lower crust, and masks the fundamental role of silicic melts (>/=66 wt% SiO(2)) beneath intermediate arc volcanoes. This alternative view resolves several puzzling aspects of arc volcanism and provides important clues to the integration of plutonic and volcanic records.

  10. Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

    Science.gov (United States)

    Doherty, Angela; Bodnar, Robert; Vivo, Benedetto; Bohrson, Wendy; Belkin, Harvey; Messina, Antonia; Tracy, Robert

    2012-06-01

    The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72-84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57-78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

  11. Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

    Science.gov (United States)

    Doherty, Angela L.; Bodnar, Robert J.; De Vivo, Benedetto; Bohrson, Wendy A.; Belkin, Harvey E.; Messina, Antonia; Tracy, Robert J.

    2012-01-01

    The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

  12. Silicates in Alien Asteroids

    Science.gov (United States)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  13. Thermochemistry of Silicates

    Science.gov (United States)

    Costa, Gustavo; Jacobson, Nathan

    2015-01-01

    The thermodynamic properties of vapor and condensed phases of silicates are crucial in many fields of science. These quantities address fundamental questions on the formation, stability, transformation, and physical properties of silicate minerals and silicate coating compositions. Here the thermodynamic activities of silica and other species in solid solution have been measured by the analysis of the corresponding high temperature vapors using Knudsen Effusion Mass Spectrometry (KEMS). In first set of experiments KEMS has been used to examine the volatility sequence of species (Fe, SiO, Mg, O2 and O) present in the vapor phase during heating of fosterite-rich olivine (Fo93Fa7) up to 2400 C and to measure the Fe, SiO and Mg activities in its solid solution. The data of fosterite-rich olivine are essential for thermochemical equilibrium models to predict the atmospheric and surface composition of hot, rocky exoplanets (Lava Planets). In the second set of experiments the measured thermodynamic activities of the silica in Y2O3-SiO2 and Yb2O3-SiO2 systems are used to assess their reactivity and degradation recession as environmental barrier coatings (EBCs) in combustion environments (e.g. non-moveable parts of gas turbine engine).

  14. Fluid inclusions in stony meteorites

    Science.gov (United States)

    Warner, J. L.; Ashwal, L. D.; Bergman, S. C.; Gibson, E. K., Jr.; Henry, D. J.; Lee-Berman, R.; Roedder, E.; Belkin, H. E.

    1983-01-01

    The fluid inclusions presently described for five stony meteorites brings to seven the number of such meteorites confirmed. Homogenization temperatures are reproducible in each inclusion, and range from 25 C to over 225 C, with some vapor plus liquid inclusions remaining at 225 C, the highest temperature in these microthermometric experiments. Upon cooling, the fluid in some inclusions appears to freeze, as indicated by deformation and immobilization of the vapor bubble at low temperatures. Melting temperatures are by contrast difficult to observe and are not reproducible. Microthermometric data for the fluid in diogenite ALPHA 77256 and inclusions in four chondrites suggest that the fluid is aqueous, with a high solute content.

  15. The viscosity window of the silicate glass foam production

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    2017-01-01

    The production of silicate glass foam allows diverse resources and waste materials to be used in the production. Testing of such large palette of materials complicates and prolongs the optimisation process. Therefore, it is crucial to find a universal criterion for foaming silicate glass melts...... which can offer a practical starting point for the optimisation procedure. The melt viscosity might be the most important parameter for controlling the foaming process and the glass foam density. In this work, we attempt to define a viscosity range in which foaming of different glasses results...... in a maximum of foam expansion. The expansion maximum is obtained for different glasses (labware, E-glass, CRT panel, soda-lime-silica) by foaming with CaCO3 at isokom temperature and from literature data. In general, the viscosity window was found to be within 104–106 Pa s when foaming with MnO2 or metal...

  16. Metal - Silicate Separation in a Deformation Regime: Implications for Early Differentiation Processes

    Science.gov (United States)

    Rushmer, T.; Jones, J. H.; Gaetani, G.; Zanda, B.

    2001-12-01

    The segregation of metallic cores from silicate mantles is one of the earliest, and most important, differentiation process involved in the evolution of the Earth and other terrestrial planetary bodies. The physical segregation of Fe-rich metal from silicate imparted a strong geochemical signature on early silicate mantles due to the preferential incorporation of siderophile elements into the core. Reconciling our estimates of primary bulk silicate mantle with candidate planetary bulk compositions requires an understanding of the geochemical consequences of the different regimes in which core forming material may have been mobile. This includes not only the possible differentiation processes that occurred in the terrestrial planets, but also understanding the differentiation processes in the meteorite parent bodies. Although a magma ocean model is possible for efficient core formation, some scenarios call for segregation of the core from solid silicate and the geochemical consequences can be significantly different. Experimental studies are one way in which insight can be gained into the possible geochemical signatures of metal-silicate segregation. Deformation experiments in addition provide a dynamic component, which allows liquid metal to segregate from solid silicate. Starting materials are cored from a slab of the Kernouve fall which is composed of olivine, pyroxene, plagioclase, chromite and chlorapatite; Fe-Ni metal and sulfide form 20-25% of the sample. Experimental conditions are 1.0-1.4 GPa confining pressure with strain rates of 10-4/s to 10-6/s. Temperatures ranging from 900° C to 1050° C produce variable amounts of silicate melt and different mechanisms of metal segregation are observed. In experiments which are below the silicate solidus, mobility of FeS is extensive and deformation textures are cataclastic. Geochemical analyses shows that migration of Fe-S-Ni-O metal through fractures and along grain boundaries produces extensive modification to

  17. Core Formation on Asteroid 4 Vesta: Iron Rain in a Silicate Magma Ocean

    Science.gov (United States)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2017-01-01

    Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA's Dawn spacecraft, suggest that Vesta resembles H chondrites in bulk chemical composition, possibly with about 25% of a CM-chondrite like composition added in. For this model, the core is 15% by mass (or 8 volume %) of the asteroid. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. Melting in the Fe-Ni-S system begins at a cotectic temperature of 940 deg. C. Only about 40% of the total metal phase, or 3-4 volume % of Vesta, melts prior to the onset of silicate melting. Liquid iron in solid silicate initially forms isolated pockets of melt; connected melt channels, which are necessary if the metal is to segregate from the silicate, are only possible when the metal phase exceeds about 5 volume %. Thus, metal segregation to form a core does not occur prior to the onset of silicate melting.

  18. Melting ice

    Science.gov (United States)

    Benedetto, Elmo

    2018-01-01

    In this brief frontline, we want to describe the well-known fact that, when freshwater ice melts, the freshwater liquid level does not change. In the Italian Ministerial programs, fluid statics is introduced in the three years of middle school (students of 11–13 years) and during the first two years of high school (14–15 years). The Italian textbooks do not clearly explain why the abovementioned phenomenon occurs. The explanations are qualitative and they may lead to misinterpretation. I have noted that the students are very curious about this phenomenon. They sought a demonstration from books and from the web; and when they do not find it they asked me. Moreover, they have allowed me to observe that there are contradictory statements about the melting of icebergs. Some authors claim that they would not raise the sea-level, others say the opposite. Honestly speaking, I had never thought about this phenomenon and in classroom I tried to give them proof, expressing my opinion about the melting of icebergs.

  19. (Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements)

    Energy Technology Data Exchange (ETDEWEB)

    Wasserburg, G.J.

    1991-01-01

    This report consists of sections entitled resonance ionization mass spectrometry of Os, Mg self-diffusion in spinel and silicate melts, neotectonics: U-Th ages of solitary corals from the California coast, uranium-series evidence on diagenesis and hydrology of carbonates of Barbados, diffusion of H{sub 2}O molecules in silicate glasses, and development of an extremely high abundance sensitivity mass spectrometer.

  20. Investigation of synthesized Be-bearing silicate glass as laboratory reference sample at X-ray electron probe microanalysis of silicates

    Science.gov (United States)

    Belozerova, Olga Yu.; Mikhailov, Mikhail A.; Demina, Tamara V.

    2017-01-01

    The article discusses estimates of the stability and homogeneity in Be-Mg-Al-silicate glass produced by the authors and its applicability as a laboratory reference sample for X-ray electron probe microanalysis (EPMA) of Be-bearing silicate matters: crystals and quenching melt (glasses), silicates and oxides. The results were obtained using Superprobe-733 and Superprobe JXA-8200 (JEOL Ltd, Japan) devices. The sample homogeneity was studied on macro (10-100 μm) and micro (1-10 μm) levels and was evaluated by the scheme of dispersion analysis. The applicability of Be-bearing silicate glass as a reference sample for Mg, Al, Si determinations was tested on the international certified reference glasses and laboratory reference samples of minerals with a known composition. The obtained experimental metrological characteristics correspond to the "applied geochemistry" type of analysis (second category) and suggest that Be-bearing silicate glass is appropriate as a laboratory reference sample for EPMA of Be-bearing silicate matters, silicates and oxides. Using Be-Mg-Al-silicate glass as a reference sample we obtained satisfactory data on the composition of both some minerals including cordierite and beryllium cordierite, beryllium indialite, beryl and metastable phases (chrysoberyl, compounds with structure of β-quartz and petalite).

  1. Detection of structural heterogeneity of glass melts

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2004-01-01

    The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One is the hyp......The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One...... is discussed. The ordered structure of glass melts above the liquidus temperature is indirectly characterized by use of X-ray diffraction method. The new approaches are of importance for monitoring the glass melting and forming process and for improving the physical properties of glasses and glass fibers....

  2. Trace elements in Gem-Quality Diamonds - Origin and evolution of diamond-forming fluid inclusions

    Science.gov (United States)

    Pearson, Graham; Krebs, Mandy; Stachel, Thomas; Woodland, Sarah; Chinn, Ingrid; Kong, Julie

    2017-04-01

    In the same way that melt inclusions in phenocrysts have expanded our idea of melt formation and evolution in basalts, studying fluids trapped in diamonds is providing important new constraints on the nature of diamond-forming fluids. Fibrous and cloudy diamonds trap a high but variable density of fluid inclusions and so have been extensively studied using major and trace element compositions. In contrast, constraining the nature of the diamond-forming fluid for high purity gem-quality diamonds has been restricted by the rarity of available high quality trace element data. This is due to the extremely low concentrations of impurities that gem diamonds contain - often in the ppt range. The recent discovery of fluids in gem diamonds showing similar major element chemistry to fluid-rich diamonds suggest that many diamonds may share a common spectrum of parental fluids. Here we test this idea further. Recent advances in analytical techniques, in particular the development of the "off-line" laser ablation pre-concentration approach, have allowed fully quantitative trace element data to be recovered from "fluid-poor", high quality gem diamonds. We present trace element data for gem diamonds from a variety of locations from Canada, S. Africa and Russia, containing either silicate or sulphide inclusions to examine possible paragenetic or genetic differences between fluids. REE abundance in the "gem" diamonds vary from 0.1 to 0.0001 x chondrite. To a first order, we observe the same spectrum of trace element compositions in the gem diamonds as that seen in fluid-rich "fibrous" diamonds, supporting a common origin for the fluids. REE patterns range from extremely flat (Ce/Yb)n 2.5 to 5 (commonly in sulphide-bearing diamonds) to >70, the latter having significantly greater inter-element HFSE/LILE fractionation. In general, the fluids from the sulphide-bearing diamonds are less REE-enriched than the silicate-bearing diamonds, but the ranges overlap significantly. The very

  3. Disequilibrium partial melting experiments on the Leedey L6 chondrite: textural controls on melting processes

    Science.gov (United States)

    Feldstein, S. N.; Jones, R. H.; Papike, J. J.

    2001-11-01

    A series of experiments was designed to investigate the textural and compositional changes that take place during disequilibrium partial melting of chondritic material. Chips of the L6 chondrite, Leedey, were heated at 1200 ºC and logfO2 = IW-1 for durations of 1 hour to 21 days. We observed a progression of kinetically-controlled textural changes in melt and restite minerals and changes in the liquidus mineralogy in response to factors such as volatile loss. During the course of the experiments, both olivine and orthopyroxene recrystallized at different times. Rare relict chondrules could still be identified after 21 days. The silicate melts that form are very heterogeneous, in terms of both major and trace element chemistry, reflecting heterogeneity of the localized mineral assemblage, particularly with respect to phosphates and clinopyroxene. Metal-sulfide melts formed in short-duration runs are also heterogeneous. The experimental data are relevant to aspects of the genesis of primitive achondrites such as the acapulcoites. The observed textures are consistent with a model for acapulcoite petrogenesis in which silicate melting was limited to only a few volume % of the chondritic source rock. The experiments are also relevant to the behavior of chondritic material that has been partially melted in an impact environment.

  4. Material transport in laser-heated diamond anvil cell melting experiments

    Science.gov (United States)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  5. Potassium Silicate Foliar Fertilizer Grade from Geothermal Sludge and Pyrophyllite

    Directory of Open Access Journals (Sweden)

    Muljani Srie

    2016-01-01

    Full Text Available Potassium silicate fertilizer grade were successfully produced by direct fusion of silica (SiO2 and potasium (KOH and K2CO3 in furnaces at temperatures up to melting point of mixture. The geothermal sludge (98% SiO2 and the pyrophyllite (95% SiO2 were used as silica sources. The purposes of the study was to synthesise potassium silicate fertilizer grade having solids concentrations in the range of 31-37% K2O, and silica in the range of 48-54% SiO2. The weight ratio of silicon dioxide/potasium solid being 1:1 to 5:1. Silica from geothermal sludge is amorphous, whereas pyrophylite is crystalline phase. The results showed that the amount of raw materials needed to get the appropriate molar ratio of potassium silicate fertilizer grade are different, as well as the fusion temperature of the furnace. Potassium silicate prepared from potassium hydroxide and geothermal sludge produced a low molar ratio (2.5: 1 to 3: 1. The potassium required quite small (4:1 in weight ratio, and on a fusion temperature of about 900 °C. Meanwhile, the potassium silicate prepared from pyrophyllite produced a high molar ratio (1.4 - 9.4 and on a fusion temperature of about 1350 °C, so that potassium needed large enough to meet the required molar ratio for the fertilizer grade. The product potassium silicate solid is amorphous with a little trace of crystalline.

  6. Effect of cooling rate on crystallization in an aluminophosphosilicate melt

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; Yue, Yuanzheng

    2011-01-01

    The effect of cooling rate on spontaneous crystallization behavior of an alumino-phospho-silicate melt is studied by means of differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and viscometry. The cooling rates of 160, 2100 and 12000 K/s are attained by subjecting...

  7. Environmental silicate nano-biocomposites

    CERN Document Server

    Pollet, Eric

    2012-01-01

    Environmental Silicate Nano-Biocomposites focuses on nano-biocomposites, which are obtained by the association of silicates such as bioclays with biopolymers. By highlighting recent developments and findings, green and biodegradable nano-composites from both renewable and biodegradable polymers are explored. This includes coverage of potential markets such as packaging, agricultures, leisure and the fast food industry. The knowledge and experience of more than twenty international experts in diverse fields, from chemical and biochemical engineering to applications, is brought together in four different sections covering: Biodegradable polymers and Silicates, Clay/Polyesters Nano-biocomposites, Clay/Agropolymers Nano-biocomposites, and Applications and biodegradation of Nano-biocomposites. By exploring the relationships between the biopolymer structures, the processes, and the final properties Environmental Silicate Nano-Biocomposites explains how to design nano-materials to develop new, valuable, environmenta...

  8. Metallic Recovery and Ferrous Melting Processes

    Energy Technology Data Exchange (ETDEWEB)

    Luis Trueba

    2004-05-30

    The effects of melting atmosphere and charge material type on the metallic and alloy recovery of ferrous charge materials were investigated in two sets of experiments (Tasks 1 and 2). In addition, thermodynamic studies were performed (Task 3) to determine the suitability of ladle treatment for the production of ductile iron using scrap charge materials high in manganese and sulfur. Task 1--In the first set of experiments, the charge materials investigated were thin steel scrap, thick steel scrap, cast iron scrap, and pig iron in the rusty and clean states. Melting atmospheres in this set of experiments were varied by melting with and without a furnace cover. In this study, it was found that neither covered melting nor melting clean (non-rusty) ferrous charge materials improved the metallic recovery over the recovery experienced with uncovered melting or rusty charge materials. However, the silicon and manganese recoveries were greater with covered melting and clean materials. Silicon and manganese in the molten iron react with oxygen dissolved in the iron from uncovered melting and oxidized iron (surface rust). Silica and manganese silicates are formed which float to the slag decreasing recoveries of silicon and manganese. Cast iron and pig iron had higher metallic recoveries than steel scrap. Carbon recovery was affected by the carbon content of the charge materials, and not by the melting conditions. Irons with higher silicon contents had higher silicon recovery than irons with lower silicon contents. Task 2--In the second set of experiments, briquetted turnings and borings were used to evaluate the effects of briquette cleanliness, carbon additions, and melting atmosphere on metallic and alloy recovery. The melting atmosphere in this set of experiments was varied by melting in air and with an argon atmosphere using the SPAL process. In this set of experiments, carbon additions to the briquettes were found to have the greatest effect on metallic and alloy

  9. Multiple ways of producing intermediate and silicic rocks within Thingmúli and other Icelandic volcanoes

    DEFF Research Database (Denmark)

    Charreteur, Gilles; Tegner, Christian; Haase, Karsten

    2013-01-01

    Major and trace element compositions of rocks and coexisting phenocrysts of the ThingmA(0)li volcano suggest a revision of the existing models for the formation of intermediate and silicic melts in Iceland. The new data define two compositional tholeiitic trends with a significant gap between them...

  10. Retrograde Evolution of the Hemlo Gold Deposit, Ontario: Fractional Crystallization of a Sulfide Melt and Remobilization of Ore-Related Metals

    Science.gov (United States)

    Heiligmann, M.; Clark, J. R.; Williams-Jones, A. E.

    2003-12-01

    The Hemlo gold deposit is a greenstone-hosted, lode-gold system in north-central Ontario, Canada. The main stage of gold mineralization occurred prior to peak, amphibolite-facies metamorphism, and is characterized by disseminated Au-Mo in potassically altered, barite- and pyrite-rich schists. Locally extensive remobilization of this ore occurred at or immediately after peak metamorphism ( ˜630° C, 5-6 kb), and is represented by minerals such as stibnite, realgar, orpiment, zinkenite and cinnabar, which are unstable at high temperature. Volumetrically minor gold was subsequently precipitated in calc-silicate zones at ˜400° C. Minerals reflecting early remobilization occur either at grain boundaries or as solid inclusions along healed fractures devoid of fluid inclusions. Planes of solid inclusions, many of which are polyphase, radiate locally from the boundaries of large polyphase sulfide aggregates. Inclusions containing both liquid and sulfides are observed mainly at intersections of planes of solid-only and liquid-vapor inclusions. Solid inclusions are characterized by complex assemblages in the system As-Sb-Pb-S, that reflect contrasting conditions of fS2 and fO2. The low thermal stability of many of these minerals, the absence of liquid in the solid inclusion trails, the excessive hydrothermal solubility of stibnite above 300° C, and the evidence of contrasting fS2 and fO2 rule out hydrothermal processes as the cause of this remobilization. We therefore propose that the latter was the result of formation of an As-Sb-Pb-S melt, at or near peak metamorphic conditions, containing minor proportions of Au, Hg, Ag, Cu, Tl and Te, and support this hypothesis with results of preliminary experiments showing that realgar-stibnite-cinnabar-bearing solids homogenize to liquid at ˜435° C. The melt is envisaged to have formed as a result of exsolution of elements such as As, Sb and Au from arsenian pyrite during metamorphic recrystallization, melting of primary

  11. Transition metals in superheat melts

    Science.gov (United States)

    Jakes, Petr; Wolfbauer, Michael-Patrick

    1993-01-01

    A series of experiments with silicate melts doped with transition element oxides was carried out at atmospheric pressures of inert gas at temperatures exceeding liquidus. As predicted from the shape of fO2 buffer curves in T-fO2 diagrams the reducing conditions for a particular oxide-metal pair can be achieved through the T increase if the released oxygen is continuously removed. Experimental studies suggest that transition metals such as Cr or V behave as siderophile elements at temperatures exceeding liquidus temperatures if the system is not buffered by the presence of other oxide of more siderophile element. For example the presence of FeO prevents the reduction of Cr2O3. The sequence of decreasing siderophility of transition elements at superheat conditions (Mo, Ni, Fe, Cr) matches the decreasing degree of depletion of siderophile elements in mantle rocks as compared to chondrites.

  12. Inclusive pedagogy

    DEFF Research Database (Denmark)

    Korsgaard, Morten Timmermann; Mortensen, Stig Skov

    With a starting point in the tradition of geisteswissenschaftliche Pädagogik this article presents a challenge to inclusive education research to engage a continental perspective on educational research. The motivation is to entice inclusive education researchers to begin to ask educational...... questions of inclusion, as opposed to inclusive questions of education. Recent years has seen a call to re-think inclusive education research and this paper attempts to answer this call by turning to a Continental perspective and the emphasis on an at least relative autonomy for the theory and practice...... and the politicisation of inclusive education, and a positive aim in the form of an argument for a move towards constructing a pedagogical ideal of inclusion....

  13. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    Science.gov (United States)

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  14. Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

    Energy Technology Data Exchange (ETDEWEB)

    Schaller, T.; Dingwell, D.B.; Keppler, H.; Merwin, L.; Sebald, A. (Univ. Bayreuth (West Germany)); Knoeller, W. (Bruker Analytische Messtechnik, Rheinstetten (West Germany))

    1992-02-01

    Anhydrous nepheline, jadeite, and albite glasses doped with F as well as hydrous F-containing haplogranitic glasses were investigated using {sup 19}F combined rotation and multiple-pulse spectroscopy; {sup 19}F {yields} {sup 29}Si cross-polarization/magic angle spinning (MAS); and high-power {sup 19}F decoupled {sup 29}Si, {sup 23}Na, and {sup 27}Al MAS nuclear magnetic resonance methods. Fluorine preferentially coordinates with Al to form octahedral AlF{sub 6}{sup 3{minus}} complexes in all glasses studied. In addition, F anions bridging two Al cations, units containing octahedral Al coordinated by both O and F, or tetrahedral Al-F complexes might be present. The presence of Si-F bonds cannot be entirely ruled out but appears unlikely on the basis of the {sup 19}F {yields} {sup 29}Si CP/MAS spectra. There is no evidence for any significant coordination of F with alkalis in the glasses studied. Over the range of F contents studied (up to 5 wt.%), there seems to be hardly any dependence of F speciation on the concentration of F in the samples. The spectroscopic results explain the decrease of the viscosity of silicate melts with increasing F content by removal of Al from bridging AlO{sub 4}-units due to complexing with F, which causes depolymerization of the melt. The same mechanism can account for the shift of the eutectic point in the haplogranite system to more feldspar-rich compositions with increasing F content, and for the peraluminous composition of most F-rich granites. Liquid immiscibility in F-rich granitic melts might be caused by formation of (Na,K){sub 3}AlF{sub 6} units in the melt with little or no interaction with the silicate component. The presence of F in granitic melts might increase the solubility of high field strength cations by making nonbridging O atoms available which form complexes with these cations.

  15. Two types of impact melts with contrasting magnetic mineralogy from Jänisjärvi impact structure, Russian Karelia

    Science.gov (United States)

    Sergienko, Elena S.; Kosterov, Andrei; Kharitonskii, Petr V.

    2017-05-01

    Palaeomagnetic and rock magnetic studies of impact-related rocks can provide important constraints for deciphering geophysical records from suspected impact structures, their geochronology, and, in the case of very large impacts, their effect on the Earth as a whole. However, the palaeomagnetic record in impact-related rocks may be ambiguous because of the uncertain origin of their natural remanent magnetization (NRM). Towards this end, we carried out a comprehensive rock magnetic and mineralogical study of tagamites (impact melts) from the Jänisjärvi astrobleme, Russian Karelia. Chemical composition of magnetic minerals and non-magnetic matrix was evaluated by scanning electron microscopy (SEM) and X-ray analysis. Magnetic minerals were identified using thermomagnetic analysis at high and low temperatures, whereas their domain state was evaluated from hysteresis measurements and magnetic force microscopy. Jänisjärvi tagamites appear to belong to two essentially different types arising from the differences in the impact melt crystallization conditions. Type I tagamites were likely formed by an extremely rapid cooling of a superhot melt with initial temperatures well above 2000 °C. Type II tagamites originate from cooler and more iron-enriched melt. Common to the two types is that they both contain a substantial amount of fine inclusions in silicate matrix tens of nanometres to few micrometres in size, which appear to be a major, in some cases dominant, magnetic mineral carrying a significant part of rocks NRM. Structurally, these inclusions are heterogeneous objects consisting of two phases showing both chemical and magnetic contrast.

  16. Infrared spectroscopy and hydrogen isotope geochemistry of hydrous silicate glasses. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Epstein, S.; Stolper, E.

    1992-03-01

    The focus of this project is the combined appication of infrared spectroscopy and stable isotope geochemistry to the study of hydrogen-bearing species dissolved in silicate melts and glasses. We are conducting laboratory experiments aimed at determining the fractionation of D and H between melt species (OH and H{sub 2}O) and hydrous vapor and the diffusivities of these species in glasses and melts. Knowledge of these parameters is critical to understanding the behavior of hydrogen isotopes during igneous processes and hydrothermal processes. These results also could be valuable in application of glass technology to development of nuclear waste disposal strategies.

  17. [Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements]. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Wasserburg, G.J.

    1991-12-31

    This report consists of sections entitled resonance ionization mass spectrometry of Os, Mg self-diffusion in spinel and silicate melts, neotectonics: U-Th ages of solitary corals from the California coast, uranium-series evidence on diagenesis and hydrology of carbonates of Barbados, diffusion of H{sub 2}O molecules in silicate glasses, and development of an extremely high abundance sensitivity mass spectrometer.

  18. Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite.

    Science.gov (United States)

    Elmore, Amy R

    2003-01-01

    This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers >5 microm as possibly carcinogenic to humans, but fibers Cosmetic Ingredient Review (CIR. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the extensive pulmonary damage in humans was the result of direct occupational inhalation of the dusts and noted that lesions seen in animals were affected by particle size, fiber length, and concentration. The Panel considers that most of the formulations are not respirable and of the preparations that are respirable, the concentration of the ingredient is very low. Even so, the Panel considered that any spray containing these solids should be formulated to minimize their inhalation. With this admonition to the cosmetics industry, the CIR Expert Panel concluded that these ingredients are safe as currently used in cosmetic formulations. The Panel did note that the cosmetic ingredient, Talc, is a hydrated magnesium silicate. Because it has a unique crystalline structure that differs from ingredients addressed in this safety assessment, Talc is not included in this report.

  19. Influence of starting material on the degassing behavior of trachytic and phonolitic melts

    Science.gov (United States)

    Preuss, Oliver; Marxer, Holger; Nowak, Marcus

    2015-04-01

    The dynamic magmatic processes beneath volcanic systems, occurring during magma ascent, cannot be observed directly in nature. Simulation of magma ascent in the lab realized by continuous decompression (CD) of a volatile containing melt is essential to understand these processes that may lead to potentially catastrophic eruptions threatening millions of people in highly populated areas like Naples located between the Campi Flegrei Volcanic Field and the Monte Somma-Vesuvio strato-volcano. In this project, experimental simulations of Campanian Ignimbrite (CI) magma ascent will give insight to the mechanisms of the CI super eruption, thus providing tools for volcanic hazard assessment at the high risk Campanian Volcanic District and other comparable volcanic systems. Additionally, comparable experiments with the same conditions using the 'white pumice' composition of the catastrophic Vesuvius AD 79 (VAD79) eruption, have been conducted. So far, the experiments were performed in an internally heated argon pressure vessel coupled with a high-pressure low-flow metering valve and a piezoelectric nano-positioning system using a starting pressure of 200 MPa, H2O content of about 5 wt% and two different decompression rates (0.024 and 0.17 MPa/s) at a superliquidus temperature of 1050 ° C to ensure a crystal free melt and a homogeneous bubble nucleation. Experiments were conducted with both, glass powder and cylinders, subsequently decompressed to 75 and 100 MPa and rapidly quenched. Beside the results that e.g. decompression rate, volatile content, fluid solubility and target pressure affect the degassing behavior of the melt, the influence of the starting material on the degassing processes is significant. Analyses of BSE- and transmitted light microscopy images revealed a different degassing behavior of glass cylinder experiments compared to powders. Nitrogen has a very low solubility in hydrous silicate melts, supporting our suggestion that preexisting nitrogen rich

  20. Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Stolper, Edward

    2007-03-05

    The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.

  1. NON-AUTOCLAVE SILICATE BRICK

    Directory of Open Access Journals (Sweden)

    V. N. Yaglov

    2015-01-01

    Full Text Available The paper proposes a technology for obtaining bricks on the basis of lime-silica mixtures where chemical interactions are practically completely realized in dispersive state at the stage of preparation of binding contact maturing and raw mixture as a whole. The role of forming operation (moulding is changed in principle because in this case conversion of dispersive system into a rock-like solid occurs and due to this the solid obtains complete water-resistance in contact with water immediately after forming operation. Theoretical basis for the developed technology is capability of silicate dispersive substances (hydrated calcium silicate to transit in non-stable state, to form a rock-like water-resistant solid in the moment of mechanical load application during forming process. Specific feature of the proposed method is an exclusion of additional operations for autoclaving of products from the process of obtaining a silicate brick.Synthetic hydrated calcium silicate in contrast to natural ones are more uniform in composition and structure, they contain less impurities and they are characterized by dispersive composition and due to the mentioned advantages they find wider practical application. Contact-condensation binders permit to manipulate product properties on their basis and ensure maximum correspondence to the requirements of the concrete application. Raw material sources for obtaining synthetic hydrated calcium silicates are practically un-limited because calcium-silicon containing substances are found as in various technogenic wastes so in natural compounds as well. So the problem for obtaining hydrated calcium silicates having contact-condensation ability for structure formation becomes more and more actual one. This transition is considered as dependent principally on arrangement rate of substance particles which determined the level of its instability.

  2. Inclusive pedagogy

    DEFF Research Database (Denmark)

    Korsgaard, Morten Timmermann; Skov Mortensen, Stig

    This article will present a case for a shift in perspective in inclusive education research towards a continentally inspired approach. Drawing on the age old distinction between continental and Anglo-American educational research the aim is to flesh out what a shift to a continental approach...... will entail, and why it might be beneficial to research in inclusive education...

  3. Social inclusion and inclusive education

    Directory of Open Access Journals (Sweden)

    Marsela Robo

    2014-07-01

    In line with global debate on social inclusion and exclusion, the author brings the way this debate has now pervaded both the official and development policy discourse in Albania.Social inclusion is considered as one of the priorities of the current government, with poverty reduction as its main focus, which will be ensured not only through economic development. In the end, the article focuses on the role of education as a very important and useful tool for ensuring social inclusion.Social inclusion through education, in particular through vocational education, considered by the author as the only way towards sustainable development of Albanian society.

  4. Battery components employing a silicate binder

    Science.gov (United States)

    Delnick, Frank M [Albuquerque, NM; Reinhardt, Frederick W [Albuquerque, NM; Odinek, Judy G [Rio Rancho, NM

    2011-05-24

    A battery component structure employing inorganic-silicate binders. In some embodiments, casting or coating of components may be performed using aqueous slurries of silicates and electrode materials or separator materials.

  5. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    The occurrence of submarine silicic volcanics is rare at the mid-oceanic ridges, abyssal depths, seamounts and fracture zones. Hydrothermal processes are active in submarine silicic environments and are associated with host ores of Cu, Au, Ag, Pb...

  6. Electronic structure of iron in magnesium silicate glasses at high pressure

    Science.gov (United States)

    Gu, Chen; Catalli, Krystle; Grocholski, Brent; Gao, Lili; Alp, Ercan; Chow, Paul; Xiao, Yuming; Cynn, Hyunchae; Evans, William J.; Shim, Sang-Heon

    2012-12-01

    A recent study attributed the source of an iron partitioning change between silicate melt and minerals at deep mantle conditions to a high-spin to low-spin change in iron, which was found in a Fe-diluted Mg-silicate glass at a similar pressure. We conducted X-ray emission spectroscopy and nuclear forward scattering on iron-rich Mg-silicate glasses at high pressure and 300 K in the diamond-anvil cell: Al-free glass up to 135 GPa and Al-bearing glass up to 93 GPa. In both glasses, the spin moment decreases gradually from 1 bar and does not reach a complete low-spin state even at the peak pressures of this study. The gradual change may be due to the existence of diverse coordination environments for iron in the glasses and continuous structural adjustment of the disordered system with pressure. If the result can be extrapolated to iron in mantle melts, the small, gradual changes in the spin state of iron may not be the dominant factor explaining the reported sudden change in the partitioning behavior of iron between silicate melt and minerals at lower-mantle pressures.

  7. Melting of carbonated pelites at 8-13 GPa: generating K-rich carbonatites for mantle metasomatism

    Science.gov (United States)

    Grassi, Daniele; Schmidt, Max W.

    2011-07-01

    The melting behaviour of three carbonated pelites containing 0-1 wt% water was studied at 8 and 13 GPa, 900-1,850°C to define conditions of melting, melt compositions and melting reactions. At 8 GPa, the fluid-absent and dry carbonated pelite solidi locate at 950 and 1,075°C, respectively; >100°C lower than in carbonated basalts and 150-300°C lower than the mantle adiabat. From 8 to 13 GPa, the fluid-present and dry solidi temperatures then increase to 1,150 and 1,325°C for the 1.1 wt% H2O and the dry composition, respectively. The melting behaviour in the 1.1 wt% H2O composition changes from fluid-absent at 8 GPa to fluid-present at 13 GPa with the pressure breakdown of phengite and the absence of other hydrous minerals. Melting reactions are controlled by carbonates, and the potassium and hydrous phases present in the subsolidus. The first melts, which composition has been determined by reverse sandwich experiments, are potassium-rich Ca-Fe-Mg-carbonatites, with extreme K2O/Na2O wt ratios of up to 42 at 8 GPa. Na is compatible in clinopyroxene with D_{{Na}}^{{{{cpx}}/{{carbonatite}}}} = 10{-}18 at the solidus at 8 GPa. The melt K2O/Na2O slightly decreases with increasing temperature and degree of melting but strongly decreases from 8 to 13 GPa when K-hollandite extends its stability field to 200°C above the solidus. The compositional array of the sediment-derived carbonatites is congruent with alkali- and CO2-rich melt or fluid inclusions found in diamonds. The fluid-absent melting of carbonated pelites at 8 GPa contrasts that at ≤5 GPa where silicate melts form at lower temperatures than carbonatites. Comparison of our melting temperatures with typical subduction and mantle geotherms shows that melting of carbonated pelites to 400-km depth is only feasible for extremely hot subduction. Nevertheless, melting may occur when subduction slows down or stops and thermal relaxation sets in. Our experiments show that CO2-metasomatism originating from subducted

  8. Amended Silicated for Mercury Control

    Energy Technology Data Exchange (ETDEWEB)

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where

  9. Removal of lead from cathode ray tube funnel glass by generating the sodium silicate.

    Science.gov (United States)

    Hu, Biao; Zhao, Shuangshuang; Zhang, Shuhao

    2015-01-01

    In the disposal of electronic waste, cathode ray tube (CRT) funnel glass is an environmental problem of old television sets. Removal of the lead from CRT funnel glass can prevent its release into the environment and allow its reuse. In this research, we reference the dry progress productive technology of sodium silicate, the waste CRT glass was dealt with sodium silicate frit melted and sodium silicate frit dissolved. Adding a certain amount of Na ₂CO₃to the waste CRT glass bases on the material composition and content of it, then the specific modulus of sodium silicate frit is obtained by melting progress. The silicon, potassium and sodium compounds of the sodium silicate frit are dissolved under the conditions of high temperature and pressure by using water as solvent, which shows the tendency that different temperature, pressure, liquid-solid ratio and dissolving time have effect on the result of dissolving. At 175°C(0.75MPa), liquid-solid ratio is 1.5:1, the dissolving time is 1h, the dissolution rate of sodium silicate frit is 44.725%. By using sodium sulfide to separate hydrolysis solution and to collect lead compounds in the solution, the recovery rate of lead in dissolving reached 100% and we can get clean sodium silicate and high purity of lead compounds. The method presented in this research can recycle not only the lead but also the sodium, potassium and other inorganic minerals in CRT glass and can obtain the comprehensive utilization of leaded glass.

  10. Investigation of C-O-H-S fluids directly exsolved from melts associated with the Mt. Somma-Vesuvius magmas

    Science.gov (United States)

    Manning, C. E.; Esposito, R.; Lamadrid, H. M.; Redi, D.; Steele-MacInnis, M. J.; Bodnar, R. J.; De Vivo, B.; Cannatelli, C.; Lima, A.

    2016-12-01

    Undegassed deep melts can be trapped as melt inclusions (MI) hosted in phenocrysts growing in magma reservoirs. The host crystal acts as a pressure capsule, ideally preventing the melt from degassing. Sometimes, MI often contain a vapor bubble when observed at ambient conditions. Bubble-bearing MI represent a natural sample with which to investigate magmatic fluids that directly exsolve from a silicate melt. Some recent studies reported that most of the CO2 in bubble-bearing MI hosted in mafic minerals is stored in the vapor bubble. However, despite the detection of CO2 in bubbles, the expected accompanying H2O has not been found in mafic MI hosted in olivine. In this presentation, we describe the discovery of H2O in MI hosted in olivine associated with the Mt. Somma-Vesuvius (Italy) magmas. We reheated crystallized (or partially crystallized) olivine-hosted MI from various eruptions at Mt. Somma-Vesuvius. We quenched bubble-bearing MI from high T (1143-1238°C) to produce a bubble-bearing glass at room T. Using Raman spectroscopy, we detected liquid H2O at room T, vapor H2O at 150°C in the vapor bubbles of reheated MI, and native S and gypsum, in addition to CO2. In most MI, the H2O is hosted in sub-micron scale hydrous phases at the interface between the bubble and the glass and would not be detected during routine analysis. During MI heating experiments, the H2O is redissolved into the melt and then exsolves from the melt into the vapor bubble, where it remains after quenching, at least on the relatively short time scales of our observations. Our results suggest that a significant amount of H2O may be stored in vapor bubbles of bubble-bearing MI, especially for MI with (1) relatively low H2O content in the originally trapped melt, (2) relatively high proportion of H2O in the exsolved fluid, (3) relatively large volume % vapor bubble. In addition, we calculated that the composition of magmatic fluids directly exsolving from mafic melts associated with Mt. Somma

  11. Silicate dissolution boosts the CO2 concentrations in subduction fluids.

    Science.gov (United States)

    Tumiati, S; Tiraboschi, C; Sverjensky, D A; Pettke, T; Recchia, S; Ulmer, P; Miozzi, F; Poli, S

    2017-09-20

    Estimates of dissolved CO2 in subduction-zone fluids are based on thermodynamic models, relying on a very sparse experimental data base. Here, we present experimental data at 1-3 GPa, 800 °C, and ∆FMQ ≈ -0.5 for the volatiles and solute contents of graphite-saturated fluids in the systems COH, SiO2-COH ( + quartz/coesite) and MgO-SiO2-COH ( + forsterite and enstatite). The CO2 content of fluids interacting with silicates exceeds the amounts measured in the pure COH system by up to 30 mol%, as a consequence of a decrease in water activity probably associated with the formation of organic complexes containing Si-O-C and Si-O-Mg bonds. The interaction of deep aqueous fluids with silicates is a novel mechanism for controlling the composition of subduction COH fluids, promoting the deep CO2 transfer from the slab-mantle interface to the overlying mantle wedge, in particular where fluids are stable over melts.Current estimates of dissolved CO2 in subduction-zone fluids based on thermodynamic models rely on a very sparse experimental data base. Here, the authors show that experimental graphite-saturated COH fluids interacting with silicates at 1-3 GPa and 800 °C display unpredictably high CO2 contents.

  12. Distribution of rubidium between sodic sanidine and natural silicic liquid

    Science.gov (United States)

    Noble, D.C.; Hedge, C.E.

    1970-01-01

    Phenocrysts of sodic sanidine from twelve upper Cenozoic units of silicic ash-flow tuff and lava from the Western United States contain from 0.25 to 0.45 the Rb present in the associated groundmass materials. The ratios of potassium to rubidium in the sanidines are, on the average, about four times greater than those of the groundmass. Separation of phenocrystic sanidine from salic melts provides an efficient method for raising the Rb content and lowering the K/Rb ratio of the melts, although the amount of differentiation probably is limited by continuous reequilibration of the alkalis between crystal and liquid phases through ion exchange. Syenites of cumulate origin will have appreciably lower Rb contents and higher K/Rb ratios than the melts from which they precipitated. Available data on the distribution of Rb between synthetic biotite and K-sanidine demonstrate that the separation of biotite probably will not deplete salic melts in Rb relative to K. ?? 1970 Springer-Verlag.

  13. Silicate Earth’s missing niobium may have been sequestered into asteroidal cores

    Science.gov (United States)

    Münker, Carsten; Fonseca, Raúl O. C.; Schulz, Toni

    2017-11-01

    Geochemical models describing the behaviour of niobium during Earth’s growth rely on the general paradigm that niobium was delivered by Earth’s asteroidal building blocks at chondritic abundances. This paradigm is based on the observation that niobium is traditionally regarded as a refractory and strongly lithophile element, and thus stored in the silicate portions of Earth and differentiated asteroids. However, Earth’s silicate mantle is instead selectively depleted in niobium, in marked contrast to the silicate mantles of many asteroids and smaller planets that apparently lack any significant depletion in niobium. Here we present results of high-precision measurements for niobium and other lithophile elements in representative meteorites from various small differentiated asteroids. Our data, along with the results of low-pressure experiments, show that in more reduced asteroids--such as Earth’s first building blocks--niobium is moderately chalcophile and more so than its geochemical twin tantalum by an order of magnitude. Accordingly, niobium can be sequestered into the cores of more reduced asteroids during differentiation via the segregation of sulfide melts in a carbon-saturated environment. We suggest that the niobium deficit in Earth’s silicate mantle may be explained by the Earth’s silicate mantle preferentially accreting the silicate portions of reduced asteroidal building blocks.

  14. Low- 18O silicic magmas: why are they so rare?

    Science.gov (United States)

    Balsley, Steven D.; Gregory, Robert T.

    1998-10-01

    Low- 18O silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of low- 18O magmas in intracontinental caldera settings is remarkable given the evidence of intense low- 18O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km 3) have plagioclase δ 18O values of 6.8±0.1‰, whereas the Middle Tuff, a small-volume (est. 50-100 km 3) post-caldera collapse pyroclastic sequence, has plagioclase δ 18O values between 5.5 and 6.8‰. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3‰ relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5‰ depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone low- 18O rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the low- 18O Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of low- 18O material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyries before the magmatic 18O can be dramatically lowered. Partial melting of low- 18O subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small-volume, low- 18O magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  15. Low-(18)O Silicic Magmas: Why Are They So Rare?

    Energy Technology Data Exchange (ETDEWEB)

    Balsley, S.D.; Gregory, R.T.

    1998-10-15

    LOW-180 silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of 10W-l `O magmas in intracontinental caldera settings is remarkable given the evidence of intense 10W-l*O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km3) have plagioclase 6180 values of 6.8 + 0.1%., whereas the Middle Tuff, a small-volume (est. 50-100 km3) post-caldera collapse pyroclastic sequence, has plagioclase 8]80 values between 5.5 and 6.8%o. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3%0 relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5%o depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone 10W-180 rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the 10W-l 80 Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of 10W-180 material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyrins bejiire the magmatic 180 can be dramatically lowered. Partial melting of low- 180 subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small- volume, 10W-180 magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  16. Chemical Zoning of Feldspars in Lunar Granitoids: Implications for the Origins of Lunar Silicic Magmas

    Science.gov (United States)

    Mills, R. D; Simon, J. I.; Alexander, C.M. O'D.; Wang, J.; Christoffersen, R.; Rahman, Z..

    2014-01-01

    Fine-scale chemical and textural measurements of alkali and plagioclase feldspars in the Apollo granitoids (ex. Fig. 1) can be used to address their petrologic origin(s). Recent findings suggest that these granitoids may hold clues of global importance, rather than of only local significance for small-scale fractionation. Observations of morphological features that resemble silicic domes on the unsampled portion of the Moon suggest that local, sizable net-works of high-silica melt (>65 wt % SiO2) were present during crust-formation. Remote sensing data from these regions suggest high concentrations of Si and heat-producing elements (K, U, and Th). To help under-stand the role of high-silica melts in the chemical differentiation of the Moon, three questions must be answered: (1) when were these magmas generated?, (2) what was the source material?, and (3) were these magmas produced from internal differentiation. or impact melting and crystallization? Here we focus on #3. It is difficult to produce high-silica melts solely by fractional crystallization. Partial melting of preexisting crust may therefore also have been important and pos-sibly the primary mechanism that produced the silicic magmas on the Moon. Experimental studies demonstrate that partial melting of gabbroic rock under mildly hydrated conditions can produce high-silica compositions and it has been suggested by that partial melting by basaltic underplating is the mechanism by which high-silica melts were produced on the Moon. TEM and SIMS analyses, coordinated with isotopic dating and tracer studies, can help test whether the minerals in the Apollo granitoids formed in a plutonic setting or were the result of impact-induced partial melting. We analyzed granitoid clasts from 3 Apollo samples: polymict breccia 12013,141, crystalline-matrix breccia 14303,353, and breccia 15405,78

  17. The effects of sulfur, silicon, water, and oxygen fugacity on solubility and metal-silicate partitioning of carbon at 3 GPa and 1600 °C - Implications for core-mantle differentiation and degassing of magma oceans and reduced planetary mantles

    Science.gov (United States)

    Li, Y.; Dasgupta, R.; Tsuno, K.

    2014-12-01

    The partition coefficient of carbon between Fe-rich alloy melt and silicate melt, and solubility of C-O-H volatiles in reduced silicate melts are key to understand the origin and distribution of carbon in different planetary reservoirs and subsequent evolution of volatiles in magma oceans (MO) and silicate mantles. In this study, three sets of graphite-saturated experiments have been performed at 3 GPa and 1600 °C to investigate the effects of oxygen fugacity (fO2), sulfur, silicon, and water on the dissolution and partitioning of carbon between Fe-rich alloy melt and silicate melt. The results show that the presence of 0-5 wt% sulfur in alloy melt does not have considerable effect on carbon solubility (~5.6 wt%) in alloy melt, whereas the presence of 0-10 wt% silicon decreases it from ~5.6 wt% to 1.8 wt%. Carbon solubility (11-192 ppm) in silicate melt is strongly controlled by fO2 and the bulk water content. Decreasing fO2 from IW-0.6 to IW-4.7 or increasing bulk water content from 0.07 to 0.55 wt% results in significant increase of carbon solubility in silicate melt. Raman and FTIR spectroscopy of silicate glasses show that the carbon species is mostly methane, confirmed by the positive correlation between carbon and non-hydroxyl hydrogen in silicate melt. The decreases from 4600 to 180 with decreasing fO2 or increasing bulk water in silicate melt. In addition, increasing Si in metallic alloy melt also decreases . Our results show that fO2 and silicate melt bulk water contents play an important role in the fractionation of carbon in planetary MO. A reduced, hydrous MO may have led to a considerable fraction of carbon retained in the silicate mantle, whereas an oxidized, dry MO may have lost almost its entire carbon to the core. If delivery of bulk Earth carbon predominantly occurred after >90% of accretion, i.e., in a relatively oxidized MO (IW-2 to IW-1), then with applicable >1000, most carbon would also enter the segregating core. Finally, the predominance

  18. Transparent phosphosilicate glasses containing crystals formed during cooling of melts

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; He, W.

    2011-01-01

    to amorphous phase separation (APS), i.e., phosphate- and silicate-rich phases. It is due to the tendency of Mg2+ to form [MgO4] linking with [SiO4]. Molar substitution of P2O5 for SiO2 enhances the network polymerization of silicate-rich phase in the melts, and thereby the spontaneous crystallization of cubic......The effect of P2O5-SiO2 substitution on spontaneous crystallization of SiO2-Al2O3-P2O5- Na2O-MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P2O5 leads...

  19. Alkali-metal silicate binders and methods of manufacture

    Science.gov (United States)

    Schutt, J. B. (Inventor)

    1979-01-01

    A paint binder is described which uses a potassium or sodium silicate dispersion having a silicon dioxide to alkali-metal oxide mol ratio of from 4.8:1 to 6.0:1. The binder exhibits stability during both manufacture and storage. The process of making the binder is predictable and repeatable and the binder may be made with inexpensive components. The high mol ratio is achieved with the inclusion of a silicon dioxide hydrogel. The binder, which also employs a silicone, is in the final form of a hydrogel sol.

  20. The opportunity of silicate product manufacturing with simultaneous pig iron reduction from slag technogenic formations

    Science.gov (United States)

    Sheshukov, O. Yu.; Lobanov, D. A.; Mikheenkov, M. A.; Nekrasov, I. V.; Egiazaryan, D. K.

    2017-09-01

    There are two main kinds of slag in modern steelmaking industry: the electric arc furnace slag (EAF slag) and ladle furnace slag (LF slag). The all known slag processing schemes provide the iron-containing component reduction while silicate component stays unprocessed. On the contrary, the silicate processing schemes doesn't provide the utilization of the iron-containing component. The present-day situation doesn't solve the problem of total slag utilization. The aim of this work is to investigate the opportunity of silicate product obtaining with simultaneous pig iron reduction from EAF and LF slags. The tests are conducted by the method of simplex-lattice design. The test samples are heated and melted under reductive conditions, slowly cooled and then analyzed by XRD methods. The experiment results prove the opportunity: the Portland clinker and pig iron can be simultaneously produced on the basis of these slags with a limestone addition.

  1. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.; Wu, James K.

    2010-10-01

    We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 mu s.

  2. ARE INCLUSIVE DESIGNERS DESIGNING INCLUSIVELY?

    DEFF Research Database (Denmark)

    Herriott, Richard

    2013-01-01

    A large body of literature exists relating to Inclusive Design. The literature can be divided into theory concerning methodology and case studies concerning practice. With such a large body of theoretical literature available, the question arises as to how closely practice matches that theory....... This paper is a survey of the methods used in the execution of self-declared inclusively design products based on an analysis of academic papers, posters and oral presentations. The case studies are divided into two groups, product design and assistive technology. Design steps were assigned to six categories...

  3. Float processing of high-temperature complex silicate glasses and float baths used for same

    Science.gov (United States)

    Cooper, Reid Franklin (Inventor); Cook, Glen Bennett (Inventor)

    2000-01-01

    A float glass process for production of high melting temperature glasses utilizes a binary metal alloy bath having the combined properties of a low melting point, low reactivity with oxygen, low vapor pressure, and minimal reactivity with the silicate glasses being formed. The metal alloy of the float medium is exothermic with a solvent metal that does not readily form an oxide. The vapor pressure of both components in the alloy is low enough to prevent deleterious vapor deposition, and there is minimal chemical and interdiffusive interaction of either component with silicate glasses under the float processing conditions. Alloys having the desired combination of properties include compositions in which gold, silver or copper is the solvent metal and silicon, germanium or tin is the solute, preferably in eutectic or near-eutectic compositions.

  4. Composition dependence of spontaneous crystallization of phosphosilicate glass melts during cooling

    DEFF Research Database (Denmark)

    Liu, S.J.; Zhu, C.F.; Zhang, Y.F.

    2012-01-01

    Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type and crystallizat......Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type...... and crystallization degree. It is found that adding NaF into the studied compositions slightly decreases melt fragility and improves both the glass-forming ability and melt workability. This effect is associated with the unique structural role of NaF compared to the other modifier oxides. It is also found...

  5. Sulfur isotope fractionation between fluid and andesitic melt: An experimental study

    Science.gov (United States)

    Fiege, Adrian; Holtz, François; Shimizu, Nobumichi; Mandeville, Charles W.; Behrens, Harald; Knipping, Jaayke L.

    2014-01-01

    Glasses produced from decompression experiments conducted by Fiege et al. (2014a) were used to investigate the fractionation of sulfur isotopes between fluid and andesitic melt upon magma degassing. Starting materials were synthetic glasses with a composition close to a Krakatau dacitic andesite. The glasses contained 4.55–7.95 wt% H2O, ∼140 to 2700 ppm sulfur (S), and 0–1000 ppm chlorine (Cl). The experiments were carried out in internally heated pressure vessels (IHPV) at 1030 °C and oxygen fugacities (fO2) ranging from QFM+0.8 log units up to QFM+4.2 log units (QFM: quartz–fayalite–magnetite buffer). The decompression experiments were conducted by releasing pressure (P) continuously from ∼400 MPa to final P of 150, 100, 70 and 30 MPa. The decompression rate (r) ranged from 0.01 to 0.17 MPa/s. The samples were annealed for 0–72 h (annealing time, tA) at the final P and quenched rapidly from 1030 °C to room temperature (T).The decompression led to the formation of a S-bearing aqueous fluid phase due to the relatively large fluid–melt partitioning coefficients of S. Secondary ion mass spectrometry (SIMS) was used to determine the isotopic composition of the glasses before and after decompression. Mass balance calculations were applied to estimate the gas–melt S isotope fractionation factor αg-m.No detectable effect of r and tA on αg-m was observed. However, SIMS data revealed a remarkable increase of αg-m from ∼0.9985 ± 0.0007 at >QFM+3 to ∼1.0042 ± 0.0042 at ∼QFM+1. Noteworthy, the isotopic fractionation at reducing conditions was about an order of magnitude larger than predicted by previous works. Based on our experimental results and on previous findings for S speciation in fluid and silicate melt a new model predicting the effect of fO2 on αg-m (or Δ34Sg–m) in andesitic systems at 1030 °C is proposed. Our experimental results as well as our modeling are of high importance for the interpretation of S isotope

  6. Smyer H-Chondrite Impact-Melt Breccia and Evidence for Sulfur Vaporization

    Science.gov (United States)

    Rubin, Alan E.

    2002-01-01

    Smyer is an H-chondrite impact-melt breccia containing approx.20 vol% 0.5- to 13-mm-thick silicate-rich melt veins surrounding unmelted subrounded chondritic clasts up to 7 cm in maximum dimension. At the interface between some of the melt veins and chondritic clasts, there are troilite-rich regions consisting of unmelted. crushed 0.2- to 140-micron-size angular silicate grains and chondrule fragments surrounded by troilite and transected by thin troilite veins. Troilite fills every available fracture in the silicates. including some as thin as 0.1 microns. Little metallic Fe-Ni is present in these regions: the FeS/Fe modal ratio ranges from -25: 1 to approx.500: 1, far higher than the eutectic weight ratio of 7.5: 1. The texture of these regions indicates that the sulfide formed from a fluid of very low viscosity. The moderately high viscosity (0.2 poise) and large surface tension of liquid FeS, its inability to wet silicate grain surfaces at low oxygen fugacities. and the supereutectic FeS/Fe ratios in the troilite-rich regions indicate that the fluid was a vapor. It seems likely that during the shock event that melted Smyer, many silicates adjacent to the melt veins were crushed. Upon release of shock pressure. some of the troilite evaporated and dissociated. Molecules of S2 were transported and condensed into fractures and around tiny silicate grains: there, they combined with Fe from small adjacent metallic Fe-Ni grains to form troilite. The Ni content at the edges of some of these metal grains increased significantly; Co from these Ni-rich grains diffused into nearby kamacite. Impact-induced S volatilization may have played a major role in depleting the surface of 433 Eros (and other chondritic asteroids) in S.

  7. Melt containment member

    Science.gov (United States)

    Rieken, Joel R.; Heidloff, Andrew J.

    2014-09-09

    A tubular melt containment member for transient containment of molten metals and alloys, especially reactive metals and alloys, includes a melt-contacting layer or region that comprises an oxygen-deficient rare earth oxide material that is less reactive as compared to the counterpart stoichiometric rare earth oxide. The oxygen-deficient (sub-stoichiometric) rare earth oxide can comprise oxygen-deficient yttria represented by Y.sub.2O.sub.3-x wherein x is from 0.01 to 0.1. Use of the oxygen-deficient rare earth oxide as the melt-contacting layer or region material reduces reaction with the melt for a given melt temperature and melt contact time.

  8. Translating Inclusion

    DEFF Research Database (Denmark)

    Fallov, Mia Arp; Birk, Rasmus

    2018-01-01

    The purpose of this paper is to explore how practices of translation shape particular paths of inclusion for people living in marginalized residential areas in Denmark. Inclusion, we argue, is not an end-state, but rather something which must be constantly performed. Active citizenship, today......, is not merely a question of participation, but of learning to become active in all spheres of life. The paper draws on empirical examples from a multi-sited field work in 6 different sites of local community work in Denmark, to demonstrate how different dimensions of translation are involved in shaping active...... citizenship. We propose the following different dimensions of translation: translating authority, translating language, translating social problems. The paper takes its theoretical point of departure from assemblage urbanism, arguing that cities are heterogeneous assemblages of socio-material interactions...

  9. Differentiation of Asteroid 4 Vesta: Core Formation by Iron Rain in a Silicate Magma Ocean

    Science.gov (United States)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2017-01-01

    Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA's Dawn spacecraft while orbiting asteroid 4 Vesta, suggest that Vesta resembles H chondrites in bulk chemical composition, possible with about 25 percent of a CM-chondrite like composition added in. For this model, the core is 15 percent by mass (or 8 percent by volume) of the asteroid, with a composition of 73.7 percent by weight Fe, 16.0 percent by weight S, and 10.3 percent by weight Ni. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. The combination of the melting phase relationships for the silicate and metal phases, together with the moderately siderophile element concentrations together require that complete melting of the metal phase occurred (temperature is greater than1350 degrees Centigrade), along with substantial (greater than 40 percent) melting of the silicate material. Thus, core formation on Vesta occurs as iron rain sinking through a silicate magma ocean.

  10. Nanoscale zinc silicate from phytoliths

    Science.gov (United States)

    Qadri, S. B.; Gorzkowski, E. P.; Rath, B. B.; Feng, C. R.; Amarasinghe, R.; Freitas, J. A.; Culbertson, J. C.; Wollmershauser, J. A.

    2017-10-01

    We report a faster, less expensive method of producing zinc silicate nanoparticles. Such particles are used in high volume to make phosphors and anti-corrosion coatings. The approach makes use of phytoliths (plant rocks), which are microscopic, amorphous, and largely silicate particles embedded in plants, that lend themselves to being easily broken down into nanoparticles. Nanoparticles of Zn2SiO4 were produced in a two stage process. In the refinement stage, plant residue, mixed with an appropriate amount of ZnO, was heated in an argon atmosphere to a temperature exceeding 1400 °C for four to six hours and then heated in air at 650 °C to remove excess carbon. TEM shows 50-100 nm nanoparticles. Raman scattering indicates that only the -Zn2SiO4 crystalline phase was present. X-ray analysis indicated pure rhombohedral R 3 bar phase results from using rice/wheat husks. Both samples luminesced predominantly at 523 nm when illuminated with X-rays or UV laser light.

  11. Tunable Properties of Inclusion Complexes Between Amylose and Polytetrahydrofuran

    NARCIS (Netherlands)

    Rachmawati, Rachmawati; Woortman, Albert J. J.; Loos, Katja

    Amylose and polytetrahydrofuran (PTHF) are mixed in an aqueous solution to form inclusion complexes. DSC shows that immediate mixing results in complexes having lower melting temperatures compared with complexes prepared with longer mixing times. The washed complexes melt at higher temperatures

  12. Silicic magmas from the Emeishan large igneous province, Southwest China: Petrogenesis and their link with the end-Guadalupian biological crisis

    Science.gov (United States)

    Xu, Yi-Gang; Chung, Sun-Lin; Shao, Hui; He, Bin

    2010-09-01

    The Emeishan large igneous province in SW China comprises a bimodal mafic-silicic suite with the silicic rocks occurring at the uppermost part of the thick lava sequence. The silicic rocks have an age of 257-263 Ma, and are thus roughly coeval with the Guadalupian-Loping (G-L) boundary event. Most silicic rocks (trachyte and rhyolite) from the Emeishan province have rather uniform ɛNd values (+ 1 to + 2.9) that are comparable with the uncontaminated high-Ti basalts. This fact and the remarkably narrow ranges of incompatible element ratios (e.g., Zr/Nb) of the basalt-silicic suite indicate a genetic relationship between basalt and silicic members. The significant difference between the Emeishan rocks and the experimental melts of hydrated basaltic crust, suggests the fractional crystallization of basaltic magma, rather than crustal melting, as the major petrogenetic process for the formation of silicic rocks. Indeed, their major and trace element trends can be modeled by fractionation of the observed mineral phases (feldspar, clinopyroxene, Fe-Ti oxide and apatite). In contrast to the virtually closed system differentiation processes associated with trachytes, the rhyolites may have experienced interaction with upper crustal material during ascent. The geochemical characteristics and recent assessment of timing of the Emeishan volcanism suggest the Emeishan rhyolites as the potential source of the widespread clay bed at the G-L boundary in south China. This enhanced the causal link between the Emeishan eruption and the end-Guadalupian biological crisis.

  13. Silicates materials of high vacuum technology

    CERN Document Server

    Espe, Werner

    2013-01-01

    Materials of High Vacuum Technology, Volume 2: Silicates covers silicate insulators of special importance to vacuum technology. The book discusses the manufacture, composition, and physical and chemical properties of technical glasses, quartz glass, quartzware, vycor glass, ceramic materials, mica, and asbestos.

  14. Annealing studies of Bi and Kr inclusions in Al

    Energy Technology Data Exchange (ETDEWEB)

    Bjoern Thoft, N.

    1995-04-01

    This report contains the results of experimental investigations of melting, solidification and growth of Bi and Kr inclusions made by ion implantation into aluminium. The experimental techniques used of for this study were x-ray diffraction, transmission electron microscopy, Rutherford backscattering, ion channeling, and grazing-incidence small-angle x-ray scattering. The x-ray diffraction signal from crystalline Bi inclusions in Al has been recorded as a function of temperature during heating to temperatures above the bulk melting point and cooling to room temperature. Data from these measurements have been fitted using models (developed by Pawlow and Wronski) for the size-dependent melting temperature of small particles, and size distributions for the inclusions have been determined in this way. Transmission electron microscopy has confirmed the melting and solidification of the Bi inclusions in the temperature ranges, in which these processes were observed by x-ray diffraction, establishing the facts that the inclusions melt below the bulk melting point and that a large supercooling is seen. Information about the amount and depth distribution of the Bi confined in the Al matrix has been derived from Rutherford backscattering measurements. Melting and solidification of Bi inclusions have been observed by means of ion channeling. The results of the investigations of bismuth inclusions in aluminium are compared to previous, similar results for lead inclusions in aluminium. Finally, preliminary experiments have confirmed that growth of Kr inclusions in Al can be observed using grazing-incidence small-angle scattering. (au) (13 tabs., 46 ills., 77 refs.).

  15. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

    2018-01-01

    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  16. Reply to `Comment on "The beginnings of hydrous mantle wedge melting" by Till et al.' by Stalder

    Science.gov (United States)

    Till, Christy B.; Grove, Timothy L.; Withers, Anthony C.

    2012-12-01

    The comment of Stalder raises three main concerns regarding the interpretation of the experiments presented by Till et al. (2012): (1) our inability to uniquely distinguish between high-pressure hydrous silicate melt and solute-rich aqueous fluid leads to the incorrect interpretation of phase relations, (2) the temperature interval over which hydrous melting takes places is inordinately large and contrary to expectations, and/or (3) the possibility that the system may be above the second critical end point (SCEP) in this H2O-rich silicate system has been insufficiently discussed. In this reply, we provide clarification on these concerns and argue that with the extent of knowledge available today, the chemical characteristics of our experimental products at 3.2 and 4 GPa evince the presence of a silicate melt at temperatures thinking about the chemical compositional characteristics of SC fluids.

  17. Spade: An H Chondrite Impact-melt Breccia that Experienced Post-shock Annealing

    Science.gov (United States)

    Rubin, Alan E.; Jones, Rhian H.

    2006-01-01

    The low modal abundances of relict chondrules (1.8 Vol%) and of coarse (i.e. >= 2200 micron-size) isolated mafic silicate grains (1.8 Vol%) in Spade relative to mean H6 chondrites (11.4 and 9.8 vol%, respectively) show Spade to be a rock that has experienced a significant degree of melting. Various petrographic features (e.g., chromite-plagioclase assemblages, chromite veinlets, silicate darkening) indicate that melting was caused by shock. Plagioclase was melted during the shock event and flowed so that it partially to completely surrounded nearby mafic silicate grains. During crystallization, plagioclase developed igneous zoning. Low-Ca pyroxene that crystallized from the melt (or equilibrated with the melt at high temperatures) acquired relatively high amounts of CaO. Metallic Fe-Ni cooled rapidly below the Fe-Ni solws and transformed into martensite. Subsequent reheating of the rock caused transformation of martensite into abundant duplex plessite. Ambiguities exist in the shock stage assignment of Spade. The extensive silicate darkening, the occurrence of chromite-plagioclase assemblages, and the impact-melted characteristics of Spade are consistent with shock stage S6. Low shock (stage S2) is indicated by the undulose extinction and lack of planar fractures in olivine. This suggests that Spade reached a maximum prior shock level equivalent to stage S6 and then experienced post-shock annealing (probably to stage Sl). These events were followed by a less intense impact that produced the undulose extinction in the olivine, characteristic of shock stage S2. Annealing could have occurred if Spade were emplaced near impact melts beneath the crater floor or deposited in close proximity to hot debris within an ejecta blanket. Spade firmly establishes the case for post-shock annealing. This may have been a common process on ordinary chondrites (OC) asteroids.

  18. Magmas and inclusions of Monte Amiata volcano, Tuscany, Italy

    NARCIS (Netherlands)

    Bergen, M.J. van

    1984-01-01

    Mt. Amiata, a Pleistocene volcanic complex in south Tuscany consists mainly of silicic (62-67 wt.% Si02) lavas and domes, many of which contain abundant metamorphic and mafic igneous inclusions. The results of a detailed geochemical and petrological study indicate a bimodal magmatic system where

  19. Mesoporous Silicate Materials in Sensing

    Directory of Open Access Journals (Sweden)

    Paul T. Charles

    2008-08-01

    Full Text Available Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through cocondensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  20. Silicate darkening in the Kobe CK Chondrite: Evidence for shock metamorphism at high temperature

    Science.gov (United States)

    Tomeoka, Kazushige; Ohnishi, Ichiro; Nakamura, Noboru

    2001-11-01

    The Kobe CK4 chondrite, like most metamorphosed CK chondrites, exhibits pronounced silicate darkening of matrix and chondrule mesostases. Our petrographic and scanning electron microscopic study reveals that the matrix of Kobe consists mostly of intermixtures of two types of fine-grained olivine. One forms subhedral to anhedral normal crystals. The other fills interstices of the subhedral to anhedral olivine crystals, exhibiting a complex network of veinlets. The latter type of olivine contains high densities of small spherical vesicles (chlorapatite. The vesicular olivine is particularly abundant in regions of matrix that exhibit a relatively high degree of darkening and commonly fills chondrule mesostases. The vesicular olivine is clearly the principal cause of the silicate darkening in Kobe. The internal texture of the vesicular olivine closely resembles those of local melts produced from the matrices of experimentally and naturally shocked carbonaceous chondrites. The occurrence and texture of the vesicular olivine suggest that it resulted from recrystallization of partially melted matrix olivine by shock. Kobe exhibits light shock effects in olivine that are consistent with shock stage S2 that is too low to explain the occurrence of olivine melting. We suggest that the vesicular olivine in Kobe was produced by shock metamorphism at a relatively mild shock pressure (600 °C). Thus, it is probable that the shock effects in olivine, manifest as fracturing and deformation, were relatively minor, but heating was strong enough to cause partial melting of matrix olivine.

  1. Determination of Reactive Surface Area of Melt Glass

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier,W.L.; Roberts, S.; Smith, D.K.; Hulsey, S.; Newton,L.; Sawvel, A.; Bruton, C.; Papelis, C.; Um, W.; Russell, C. E.; Chapman,J.

    2000-10-01

    A comprehensive investigation of natural and manmade silicate glasses, and nuclear melt glass was undertaken in order to derive an estimate of glass reactive surface area. Reactive surface area is needed to model release rates of radionuclides from nuclear melt glass in the subsurface. Because of the limited availability of nuclear melt glasses, natural volcanic glass samples were collected which had similar textures and compositions as those of melt glass. A flow-through reactor was used to measure the reactive surface area of the analog glasses in the presence of simplified NTS site ground waters. A measure of the physical surface area of these glasses was obtained using the BET gas-adsorption method. The studies on analog glasses were supplemented by measurement of the surface areas of pieces of actual melt glass using the BET method. The variability of the results reflect the sample preparation and measurement techniques used, as well as textural heterogeneity inherent to these samples. Based on measurements of analog and actual samples, it is recommended that the hydraulic source term calculations employ a range of 0.001 to 0.01 m{sup 2}/g for the reactive surface area of nuclear melt glass.

  2. Structural Transitions and Strengths of Mg-Silicate Glasses to 80 GPa

    Science.gov (United States)

    Grocholski, B.; Catalli, K.; Shim, S.

    2008-12-01

    Early Earth's mantle may be molten to its deep interior. Therefore, physical processes in the magma ocean determine the initial conditions for the structure of the mantle. Seismologic studies have shown that the present-day mantle has melts atop the transition zone and the core-mantle boundary. Therefore, the properties of silicate melts are important for understanding the evolution of the Earth's mantle. We measured Raman scattering of silicate glasses, frozen forms of melts, with mantle related compositions, MgSiO3, Mg2SiO4, and CaSiO3, in the diamond-anvil cell up to 80 GPa. In MgSiO3 glass, Raman spectra show a structural transition associated with increases in the coordination number at 19-38 GPa and another transition likely related to changes in the Si-O polyhedral connectivity at 65-70 GPa. However, in CaSiO3 and Mg2SiO4 glasses, the former transition occurs at higher pressures (P) by 5-10 GPa and the latter transition does not occur to our maximum P, indicating that a less polymerized Si-O network increases the transition P. The compositional sensitivity of the transition P in silicate melts would result in dense MgSiO3 melt in a high-P structure and less dense Mg2SiO4 and CaSiO3 melts in low-P structures at mid-mantle depths. This density contrast will make Si-rich melts negatively buoyant but Si-poor melts postively buoyant, resulting in the Si-enriched deeper mantle. Therefore, the early magma ocean may be compositionally stratified and therefore contribute to the formation of "hidden geochemical reservoir". Our findings provide a physical mechanism for the early differentiation suggested from geochemical observations of short-lived 142Nd (Boyet and Carlson, 2005). We also measured the yield strength of MgSiO3, Mg2SiO4, and SiO2 glasses to 55 GPa in the diamond cell through the pressure gradients in the samples. The change in thickness with P was monitored visually by measuring the change in focal point from both sides of the sample. Yield strength does

  3. Primordial Compositions of Refractory Inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Grossman, L; Simon, S B; Rai, V K; Thiemens, M H; Hutcheon, I D; Williams, R W; Galy, A; Ding, T; Fedkin, A V; Clayton, R N; Mayeda, T K

    2008-02-20

    Bulk chemical and oxygen, magnesium and silicon isotopic compositions were measured for each of 17 Types A and B refractory inclusions from CV3 chondrites. After bulk chemical compositions were corrected for non-representative sampling in the laboratory, the Mg and Si isotopic compositions of each inclusion were used to calculate its original chemical composition assuming that the heavy-isotope enrichments of these elements are due to Rayleigh fractionation that accompanied their evaporation from CMAS liquids. The resulting pre-evaporation chemical compositions are consistent with those predicted by equilibrium thermodynamic calculations for high-temperature nebular condensates but only if different inclusions condensed from nebular regions that ranged in total pressure from 10{sup -6} to 10{sup -1} bar, regardless of whether they formed in a system of solar composition or in one enriched in OC dust relative to gas by a factor of ten relative to solar composition. This is similar to the range of total pressures predicted by dynamic models of the solar nebula for regions whose temperatures are in the range of silicate condensation temperatures. Alternatively, if departure from equilibrium condensation and/or non-representative sampling of condensates in the nebula occurred, the inferred range of total pressure could be smaller. Simple kinetic modeling of evaporation successfully reproduces observed chemical compositions of most inclusions from their inferred pre-evaporation compositions, suggesting that closed-system isotopic exchange processes did not have a significant effect on their isotopic compositions. Comparison of pre-evaporation compositions with observed ones indicates that 80% of the enrichment in refractory CaO + Al{sub 2}O{sub 3} relative to more volatile MgO + SiO{sub 2} is due to initial condensation and 20% due to subsequent evaporation for both Type A and Type B inclusions.

  4. Melt Cast High Explosives

    Directory of Open Access Journals (Sweden)

    Stanisław Cudziło

    2014-12-01

    Full Text Available [b]Abstract[/b]. This paper reviews the current state and future developments of melt-cast high explosives. First the compositions, properties and methods of preparation of trinitrotoluene based (TNT conventional mixtures with aluminum, hexogen (RDX or octogen (HMX are described. In the newer, less sensitive explosive formulations, TNT is replaced with dinitroanisole (DNANDNANDNAN and nitrotriazolone (NTONTONTO, nitroguanidine (NG or ammonium perchlorate (AP are the replacement for RDRDX and HMX. Plasticized wax or polymer-based binder systems for melt castable explosives are also included. Hydroxyl terminated polybutadiene (HPTB is the binder of choice, but polyethylene glycol, and polycaprolactone with energetic plasticizers are also used. The most advanced melt-cast explosives are compositions containing energetic thermoplastic elastomers and novel highly energetic compounds (including nitrogen rich molecules in whose particles are nanosized and practically defect-less.[b]Keywords[/b]: melt-cast explosives, detonation parameters

  5. Alkali Silicate Vehicle Forms Durable, Fireproof Paint

    Science.gov (United States)

    Schutt, John B.; Seindenberg, Benjamin

    1964-01-01

    The problem: To develop a paint for use on satellites or space vehicles that exhibits high resistance to cracking, peeling, or flaking when subjected to a wide range of temperatures. Organic coatings will partially meet the required specifications but have the inherent disadvantage of combustibility. Alkali-silicate binders, used in some industrial coatings and adhesives, show evidence of forming a fireproof paint, but the problem of high surface-tension, a characteristic of alkali silicates, has not been resolved. The solution: Use of a suitable non-ionic wetting agent combined with a paint incorporating alkali silicate as the binder.

  6. Model Dust Envelopes Around Silicate Carbon Stars

    Directory of Open Access Journals (Sweden)

    Kyung-Won Suh

    2006-03-01

    Full Text Available We have modeled dust envelopes around silicate carbon stars using optical properties for a mixture of amorphous carbon and silicate dust grains paying close attention to the infrared observations of the stars. The 4 stars show various properties in chemistry and location of the dust shell. We expect that the objects that fit a simple detached silicate dust shell model could be in the transition phase of the stellar chemistry. For binary system objects, we find that a mixed dust chemistry model would be necessary.

  7. Tailoring hierarchical structures in selective laser melted materials

    Science.gov (United States)

    Olsen, Jon; Zhou, Xin; Zhong, Yuan; Liu, Leifeng; Wang, Dianzheng; Yu, Chenfan; Wang, Yafei; Li, Kailun; Xing, Leilei; Ma, Jing; Cui, Daqing; Liu, Wei; Shen, Zhijian

    2017-07-01

    With selective laser melting the potential to manufacture a wide variety of geometries from different materials has presented itself. Interest in this technology keeps growing every year, and with that growth a deeper understanding of the process and resulting materials is urgently needed. In this paper we present a short overview of the structural elements that appear during selective laser melting, and explain how to tailor them to achieve specific structures and material properties. Melt-pools, texture and grains, subgrain cells, and inclusions are the elements discussed herein, and tailoring of these elements can have effects on density, and corrosion resistance, as well as mechanical properties in general.

  8. Slab melting and magma formation beneath the southern Cascade arc

    Science.gov (United States)

    Walowski, Kristina J.; Wallace, Paul J.; Clynne, Michael A.; Rasmussen, D.J.; Weis, D.

    2016-01-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO>7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  9. Wet melting along the Tonga Volcanic Arc

    Science.gov (United States)

    Cooper, L. B.; Plank, T.; Arculus, R. J.; Hauri, E. H.; Hall, P.

    2010-12-01

    Melting in the mantle at convergent margins is driven by water from the subducting slab. Previous work has found a strong role for water-fluxed melting from correlations between the concentration of water in the mantle source, (H2O)o, and the extent of melting beneath backarcs, Fba. Here we explore how wet melting beneath the Lau Backarc Basin relates to that beneath the Tonga Arc, Farc, by providing the first systematic study of water contents in Tonga arc magmas. We have measured volatiles and major and trace elements in melt inclusions, glasses, and whole rocks obtained from recently sampled submarine and subaerial Tonga arc volcanoes. The compositions are varied and range mostly between andesite and basalt/boninite, and least-degassed water contents range from 2 to 5 wt%. We estimate (H2O)o and Farc independently by combining pressure (P) and temperature (T) estimates from an olivine-orthopyroxene-melt thermobarometer with a wet melting productivity model. When P, T, and (H2O)o are known, Farc is uniquely constrained. Results for the volcanoes in the Tonga Arc are bimodal with respect to T: volcanoes located near active backarc spreading centers reflect cooler melting (~1275°C) than those located far from active spreading centers (~1365°C). The cooler primary T’s may result from removal of the heat of fusion during prior melting beneath the Lau backarc, Fba. In the northern portion of the arc, the warmest primary T’s may be due to proximity to the Samoan mantle plume. Farc varies non-systematically along-strike, indicating that Fba is the primary driver of along-arc variability in primary melt compositions. Farc can also be used to calculate the TiO2 concentration of the arc mantle source, (TiO2)o (a proxy for source depletion), which varies monotonically along the Tonga Arc. Arc volcanoes adjacent to the Southern Lau Rifts and Valu Fa Ridge melt mantle with a fertile N-MORB TiO2, while those adjacent to the northern extent of the Eastern Lau Spreading

  10. Siliceous microfossil extraction from altered Monterey rocks

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C.O.; Casey, R.E.

    1986-04-01

    Samples of altered Monterey rocks of differing lithologies were processed by various methods to develop new techniques for extracting siliceous microfossils. The preliminary use of thin sections made from the same rocks reduced the number of probable samples (samples worth further processing) by about one-third. Most of the siliceous microfossils contained in altered Monterey rocks appear to be highly recrystallized and are extremely fragile; however, some contained silicified and silica-infilled radiolarians and planktonic and benthonic foraminifera, which are very tough. In general the most useful techniques were gently hydrochloric acid, hydrogen peroxide, formic acid, monosodium glutamate, and regular siliceous microfossil extraction techniques. Unsuccessful techniques and a new siliceous microfossil flotation technique are also documented.

  11. Carbon Monoxide Silicate Reduction System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is a novel technology for producing large quantities of oxygen on the Moon. Oxygen yields of 15 kilograms per...

  12. Carbon Monoxide Silicate Reduction System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is an innovative method that for the first time uses the strong reductant carbon monoxide to both reduce iron...

  13. MELTED BUTTER TECHNOLOGY DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    L. V. Golubeva

    2014-01-01

    Full Text Available Summary. Melted butter is made from dairy butter by rendering the fat phase. It has specific taste and aroma, high-calorie content and good assimilability. Defects of butter which appeared during the storage causes by the development of microbiological processes or by the chemical oxidation. On the development of these processes influence quality and composition of fresh butter, its physical structure, content of the increased amount of gas phase and content of heavy metals, storage conditions. Microbiological spoilage of butter occurs generally due to damage of plasma which is good environment for the development of microorganisms. Defects of microbiological origin include: unclean, sour, moldy, yeasty, cheesy, bitter taste. Defects of test and smell chemical origin are formed due to hydrolytic digestion of lipids. It's prevailed at long storage of butter in the conditions of freezing temperatures. It's picked out the following main processes of spoiling: souring, acidifying and sallowness. Often these processes take place simultaneously.It has been investigated melted butter with lactated additive. The latter improves the microbiological and toxicological safety, prolongs the storage condition of the products. Technological efficiency of the additives is achieved by a multilayer products formation from the inactive bound water, preventing microorganisms growth and by the barrier layer with lactate inhibiting hydrolytic reactions. Oil samples were obtained with the batch-type butter maker application, then they were melted and after that lactated additive were supplemented. It has been studied organoleptic and physico-chemical indices of the melted butter samples. The fatty-acid composition of melted butter were studied. Comparative analysis of fatty-acid composition of cow's milk fat and produced melted butter has shown their similarity. Also in the last sample there is increased weight fraction of linoleic and linolenic acids. The obtained

  14. Peralkaline silicic volcanic rocks in northwestern nevada.

    Science.gov (United States)

    Noble, D C; Chipman, D W; Giles, D L

    1968-06-21

    Late Tertiary silicic ashflow tuffs and lavas peralkaline in chemical character (atomic Na + K greater than Al), mainly comendites, occur over wide areas in northwestern Nevada and appear to be widespread in southeastern Oregon. Such peralkaline rocks-which are not uncommon in the western United States-and other chemically unusual silicic rocks are found near the margins rather than toward the center of the Great Basin.

  15. Silicate-SiO reaction in a protoplanetary disk recorded by oxygen isotopes in chondrules

    Science.gov (United States)

    Tanaka, Ryoji; Nakamura, Eizo

    2017-07-01

    The formation of planetesimals and planetary embryos during the earliest stages of the solar protoplanetary disk largely determined the composition and structure of the terrestrial planets. Within a few million years of the birth of the Solar System, chondrule formation and the accretion of the parent bodies of differentiated achondrites and the terrestrial planets took place in the inner protoplanetary disk 1,2 . Here we show that, for chondrules in unequilibrated enstatite chondrites, high-precision Δ17O values (where Δ17O is the deviation of the δ17O value from a terrestrial silicate fractionation line) vary significantly (ranging from -0.49 to +0.84‰) and fall on an array with a steep slope of 1.27 on a three-oxygen-isotope plot. This array can be explained by the reaction between an olivine-rich chondrule melt and an SiO-rich gas derived from vaporized dust and nebular gas. Our study suggests that a large proportion of the building blocks of planetary embryos formed by successive silicate-gas interaction processes: silicate-H2O followed by silicate-SiO interactions under more oxidized and reduced conditions, respectively, within a few million years of the formation of the Solar System.

  16. On the origin of silicate-bearing diamondites

    Science.gov (United States)

    Dobosi, Gabor; Kurat, Gero

    2010-05-01

    Garnets and clinopyroxenes, intergrown with diamonds in 37 diamondites (“bort”, “polycrystalline diamond aggregates”, “polycrystalline diamond”, “framesite”), presumably from southern Africa, were analyzed for trace element contents by LA-ICP-MS. The intimate diamond-silicate intergrowths suggest that both precipitated from the same fluids during the same crystallization events. In this study we distinguish 5 chemical garnet groups: “peridotitic” (P), intermediate (I) and 3 “eclogitic” groups (E1, E2 and E3). Chondrite-normalized trace element patterns for the garnet groups roughly correlate with major element abundances. Most of P garnets show complex, mildly sinusoidal REEN patterns with relatively flat HREEN-MREEN, a small hump at Sm-Nd and depleted LREEN, and have relatively high contents of Nb, Ta, U, and Th. The REEN abundance patterns of E garnets differ by showing a continuous increase from LREE to HREE and depletion in LREE and highly incompatible elements relative to the P garnets. Of all garnet groups, E3 garnets are the poorest in highly incompatible trace elements and in Mg. Model equilibrium fluids for P garnets suggest crystallization from magnesian carbonate-bearing fluids/melts, which were very rich in incompatible trace elements — similar to kimberlites. Hypothetical equilibrium melts for E1 and E2 garnets are also magnesian and poorer in LREE and highly incompatible elements relative to typical kimberlitic or carbonatitic melts. Fluids that crystallized the P and most of the E garnets have similar mg numbers indicating a peridotitic source for both. The differences in Cr and highly incompatible element contents can be the result of differences in fluid formation and/or evolution rather than different source rock. The positive correlation of Cr2O3 and mg with the abundances of highly incompatible elements in garnets indicate fluid-rock fractionation processes rather than igneous fractional crystallization processes being

  17. Thermodynamics and Kinetics of Silicate Vaporization

    Science.gov (United States)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  18. Calcium-aluminum-rich inclusions recycled during formation of porphyritic chondrules from CH carbonaceous chondrites

    Science.gov (United States)

    Krot, Alexander N.; Nagashima, Kazuhide; van Kooten, Elishevah M. M.; Bizzarro, Martin

    2017-03-01

    We report on the mineralogy, petrography, and O-isotope compositions of ∼60 Ca, Al-rich inclusions (CAIs) incompletely melted during formation of porphyritic chondrules from the CH metal-rich carbonaceous chondrites and Isheyevo (CH/CB). These include (i) relict polymineralic CAIs in porphyritic chondrules, (ii) CAIs surrounded by chondrule-like igneous rims, (iii) igneous pyroxene-rich and Type C-like CAIs, and (iv) plagioclase-rich chondrules with clusters of relict spinel grains. 26Al-26Mg systematics were measured in 10 relict CAIs and 11 CAI-bearing plagioclase-rich chondrules. Based on the mineralogy, the CH CAIs incompletely melted during chondrule formation can be divided into grossite-rich (n = 13), hibonite-rich (n = 11), spinel ± melilite-rich (n = 33; these include plagioclase-rich chondrules with clusters of relict spinel grains) types. Mineralogical observations indicate that these CAIs were mixed with different proportions of ferromagnesian silicates and experienced incomplete melting and gas-melt interaction during chondrule formation. These processes resulted in partial or complete destruction of the CAI Wark-Lovering rims, replacement of melilite by Na-bearing plagioclase, and dissolution and overgrowth of nearly end-member spinel by chromium- and iron-bearing spinel. Only two relict CAIs and two CAI-bearing chondrules show resolvable excess of radiogenic 26Mg; the inferred initial 26Al/27Al ratios are (1.7 ± 1.3) × 10-6, (3.7 ± 3.1) × 10-7, (1.9 ± 0.9) × 10-6 and (4.9 ± 2.6) × 10-6. There is a large range of Δ17O among the CH CAIs incompletely melted during chondrule formation, from ∼-37‰ to ∼-5‰; the unmelted minerals in individual CAIs, however, are isotopically uniform and systematically 16O-enriched relative to the host chondrules and chondrule-like igneous rims, which have Δ17O ranging from ∼-7‰ to ∼+4‰. Most of the CH CAIs incompletely melted during chondrule formation are mineralogically and isotopically

  19. Tenoumer impact crater, Mauritania: Impact melt genesis from a lithologically diverse target

    Science.gov (United States)

    Schultze, Dina Simona; Jourdan, Fred; Hecht, Lutz; Reimold, Wolf Uwe; Schmitt, Ralf-Thomas

    2016-02-01

    Impact melt rocks from the 1.9 km diameter, simple bowl-shaped Tenoumer impact crater in Mauritania have been analyzed chemically and petrologically. They are heterogeneous and can be subdivided into three types based on melt matrix color, occurrence of lithic clast components, amount of vesiculation (melt degassing), different proportions of carbonate melt mingled into silicate melt, and bulk rock chemical composition. These heterogeneities have two main causes (1) due to the small size of the impact crater, there was probably no coherent melt pool where a homogeneous mixture of melts, derived from different target lithologies, could be created; and (2) melt rock heterogeneity occurring at the thin section scale is due to fast cooling during and after the dynamic ejection and emplacement process. The overall period of crystal growth from these diverse melts was extremely short, which provides a further indication that complete chemical equilibration of the phases could not be achieved in such short time. Melt mixing processes involved in the generation of impact melts are, thus, recorded in nonequilibrium growth features. Variable mixing processes between chemically different melt phases and the formation of hybrid melts can be observed even at millimeter scales. Due to extreme cooling rates, different mixing and mingling stages are preserved in the varied parageneses of matrix minerals and in the mineral chemistry of microlites. 40Ar39Ar step-heating chronology on specimens from three melt rock samples yielded five concordant inverse isochron ages. The inverse isochron plots show that minute amounts of inherited 40Ar* are present in the system. We calculated a weighted mean age of 1.57 ± 0.14 Ma for these new results. This preferred age represents a refinement from the previous range of 21 ka to 2.5 Ma ages based on K/Ar and fission track dating.

  20. Crust behavior and erosion rate prediction of EPR sacrificial material impinged by core melt jet

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gen; Liu, Ming, E-mail: ming.liu@mail.xjtu.edu.cn; Wang, Jinshi; Chong, Daotong; Yan, Junjie

    2017-04-01

    Highlights: • A numerical code was developed to analyze melt jet-concrete interaction in the frame of MPS method. • Crust and ablated concrete layer at UO{sub 2}-ZrO{sub 2} melt and concrete interface periodically developed and collapsed. • Concrete surface temperature fluctuated around a low temperature and ablation temperature. • Concrete erosion by Fe-Zr melt jet was significantly faster than that by UO{sub 2}-ZrO{sub 2} melt jet. - Abstract: Sacrificial material is a special ferro-siliceous concrete, designed in the ex-vessel core melt stabilization system of European Pressurized water Reactor (EPR). Given a localized break of RPV lower head, the melt directly impinges onto the dry concrete in form of compact jet. The concrete erosion behavior influences the failure of melt plug, and further affects melt spreading. In this study, a numerical code was developed in the frame of Moving Particle Semi-implicit (MPS) method, to analyze the crust behavior and erosion rate of sacrificial concrete, impinged by prototypic melt jet. In validation of numerical modeling, the time-dependent erosion depth and erosion configuration matched well with the experimental data. Sensitivity study of sacrificial concrete erosion indicates that the crust and ablated concrete layer presented at UO{sub 2}-ZrO{sub 2} melt and concrete interface, whereas no crust could be found in the interaction of Fe-Zr melt with concrete. The crust went through stabilization-fracture-reformation periodic process, accompanied with accumulating and collapsing of molten concrete layer. The concrete surface temperature fluctuated around a low temperature and ablation temperature. It increased as the concrete surface layer was heated to melting, and dropped down when the cold concrete was revealed. The erosion progression was fast in the conditions of small jet diameter and large concrete inclination angle, and it was significantly faster in the erosion by metallic melt jet than by oxidic melt jet.

  1. 3D Compressible Melt Transport with Adaptive Mesh Refinement

    Science.gov (United States)

    Dannberg, Juliane; Heister, Timo

    2015-04-01

    Melt generation and migration have been the subject of numerous investigations, but their typical time and length-scales are vastly different from mantle convection, which makes it difficult to study these processes in a unified framework. The equations that describe coupled Stokes-Darcy flow have been derived a long time ago and they have been successfully implemented and applied in numerical models (Keller et al., 2013). However, modelling magma dynamics poses the challenge of highly non-linear and spatially variable material properties, in particular the viscosity. Applying adaptive mesh refinement to this type of problems is particularly advantageous, as the resolution can be increased in mesh cells where melt is present and viscosity gradients are high, whereas a lower resolution is sufficient in regions without melt. In addition, previous models neglect the compressibility of both the solid and the fluid phase. However, experiments have shown that the melt density change from the depth of melt generation to the surface leads to a volume increase of up to 20%. Considering these volume changes in both phases also ensures self-consistency of models that strive to link melt generation to processes in the deeper mantle, where the compressibility of the solid phase becomes more important. We describe our extension of the finite-element mantle convection code ASPECT (Kronbichler et al., 2012) that allows for solving additional equations describing the behaviour of silicate melt percolating through and interacting with a viscously deforming host rock. We use the original compressible formulation of the McKenzie equations, augmented by an equation for the conservation of energy. This approach includes both melt migration and melt generation with the accompanying latent heat effects. We evaluate the functionality and potential of this method using a series of simple model setups and benchmarks, comparing results of the compressible and incompressible formulation and

  2. Siderophile elements in the upper mantle of the Earth: New clues from metal-silicate partition coefficients

    Science.gov (United States)

    Holzheid, A.; Borisov, A.; Palme, H.

    1993-03-01

    New, precise data on the solubilities of Ni, Co, and Mo in silicate melts at 1400 C and fO2 from IW to IW-2 are presented. The results suggest NiO, CoO as stable species in the melt. No evidence for metallic Ni or Co was found. Equilibrium was ensured by reversals with initially high Ni and Co in the glass. Mo appears to change oxidation state at IW-1, from MoO3 to MoO2. Metal-silicate partition coefficients calculated from these data and recent data on Pd indicate similar partition coefficients for Pd and Mo at the conditions of core formation. This unexpected result constrains models of core formation in the Earth.

  3. Crystalline Silicate-perovskite in S6 L6 Chondrite ACFER 040: A Relatively High Shock Pressure of Only 25-26GPa

    Science.gov (United States)

    Hu, J.; Sharp, T. G.; Trickey, R.

    2011-12-01

    Many L6 chondrites are highly shocked and contain high-pressure minerals in and adjacent to shock melt veins and melt pockets. Pressure and duration estimates from shock features are used to understand impact events on the L chondrite parent body (Sharp and DeCarli, 2004; Xie et al, 2006; Ohtani et al, 2004). The crystallization assemblages in shock melt veins and pockets constrain the shock pressures to a maximum of about 25 GPa in most L6 chondrites. Acfer 040 is a highly shocked (S6) L5-6 chondrite with numerous melt veins and pockets. Akimotoite and vitrified silicate-perovskite were identified in Acfer 040 suggesting a relatively high shock pressure relative to other L6 S6 chondrites (Sharp et al, 1997). However, that study was limited to a very small amount of melt-vein material and no crystalline perovskite was found. Tomioka and Fujino (1997) also found silicate perovskite in Tenham, but they were unable to get sufficient diffraction data to fully characterize it. Recently, Miyahara et al (2011) found olivine that transformed to perovskite plus magneseowustite in a Martian meteorite. They also have limited electron diffraction data from the perovskite. In this study, we use laser-Raman spectroscopy, FESEM and FIB-TEM to reinvestigate the melt-vein matrix and high-pressure mineralogy of Acfer 040 and search for crystalline-silicate perovskite. Two distinct crystallization assemblages are identified in the melt veins and pockets: 1) akimotoite + vitrious silicate-perovskite and 2) ringwoodite + vitrious silicate-perovskite. Transformed fragments of high- and low-Ca pyroxenes are also amorphous, suggesting that both pyroxenes transformed to perovskite that subsequently vitrified during decompression. Some of transformed pyroxenes appear crystalline in SEM images. Preliminary TEM data from a FIB sample suggest that some of the silicate perovskite has survived. Detailed analysis of diffraction data will be presented. The abundance of vitrified silicate

  4. The roles of fractional crystallization, magma mixing, crystal mush remobilization and volatile-melt interactions in the genesis of a young basalt-peralkaline rhyolite suite, the greater Olkaria volcanic complex, Kenya Rift valley

    Science.gov (United States)

    Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.

    2008-01-01

    The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All

  5. GLASS MELTING PHENOMENA, THEIR ORDERING AND MELTING SPACE UTILISATION

    Directory of Open Access Journals (Sweden)

    Němec L.

    2013-12-01

    Full Text Available Four aspects of effective glass melting have been defined – namely the fast kinetics of partial melting phenomena, a consideration of the melting phenomena ordering, high utilisation of the melting space, and effective utilisation of the supplied energy. The relations were defined for the specific melting performance and specific energy consumption of the glass melting process which involve the four mentioned aspects of the process and indicate the potentials of effective melting. The quantity “space utilisation” has been treated in more detail as an aspect not considered in practice till this time. The space utilisation was quantitatively defined and its values have been determined for the industrial melting facility by mathematical modelling. The definitions of the specific melting performance and specific energy consumption have been used for assessment of the potential impact of a controlled melt flow and high space utilisation on the melting process efficiency on the industrial scale. The results have shown that even the partial control of the melt flow, leading to the partial increase of the space utilisation, may considerably increase the melting performance, whereas a decrease of the specific energy consumption was determined to be between 10 - 15 %.

  6. Carbonate-silicate ratio for soil correction and influence on nutrition, biomass production and quality of palisade grass

    Directory of Open Access Journals (Sweden)

    Renato Ferreira de Souza

    2011-10-01

    Full Text Available Silicates can be used as soil correctives, with the advantage of being a source of silicon, a beneficial element to the grasses. However, high concentrations of silicon in the plant would affect the digestibility of the forage. To evaluate the influence of the substitution of the calcium carbonate by calcium silicate on the nutrition, biomass production and the feed quality of the palisade grass [Urochloa brizantha (C. Hochstetter ex A. Rich. R. Webster], three greenhouse experiments were conducted in completely randomized designs with four replications. Experimental units (pots contained a clayey dystrophic Rhodic Haplustox, a sandy clay loam dystrophic Typic Haplustox and a sandy loam dystrophic Typic Haplustox. Each soil received substitution proportions (0, 25, 50, 75 and 100 % of the carbonate by calcium silicate. The increase in the proportion of calcium silicate elevated the concentrations and accumulations of Si, Ca, Mg, and B, reduced Zn and did not alter P in the shoot of plants. The effects of the treatments on the other nutrients were influenced by the soil type. Inclusion of calcium silicate also increased the relative nutritional value and the digestibility and ingestion of the forage, while the concentration and accumulation of crude protein and the neutral detergent and acid detergent fibers decreased. Biomass production and feed quality of the palisade grass were generally higher with the 50 % calcium silicate treatment.

  7. Hydration characteristics of calcium silicate cements with alternative radiopacifiers used as root-end filling materials.

    Science.gov (United States)

    Camilleri, Josette

    2010-03-01

    Mineral trioxide aggregate (MTA) is composed of calcium silicate cement and bismuth oxide added for radiopacity. The bismuth oxide in MTA has been reported to have a deleterious effect on the physical and chemical properties of the hydrated material. This study aimed to investigate the hydration mechanism of calcium silicate cement loaded with different radiopacifiers for use as a root-end filling material. Calcium silicate cement loaded with barium sulfate, gold, or silver/tin alloy was hydrated, and paste microstructure was assessed after 30 days. In addition, atomic ratio plots of Al/Ca versus Si/Ca and S/Ca and Al/Ca were drawn, and X-ray energy dispersive analysis of the hydration products was performed to assess for inclusion of heavy metals. The leachate produced from the cements after storage of the cements in water for 28 days and the leaching of the radiopacifiers in an alkaline solution was assessed by using inductively coupled plasma. The hydrated calcium silicate cement was composed of calcium silicate hydrate, calcium hydroxide, ettringite, and monosulfate. Unhydrated cement particles were few. No heavy metals were detected in the calcium silicate hydrate except for the bismuth in MTA. Calcium was leached out early in large quantities that reduced with time. The barium and bismuth were leached in increasing amounts. Copper was the most soluble in alkaline solution followed by bismuth and barium in smaller amounts. The bismuth oxide can be replaced by other radiopacifiers that do not affect the hydration mechanism of the resultant material. Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  8. High Resolution Melting Analysis for fast and cheap polymorphism screening of marine populations

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Anne-Leila Meistertzheim, Isabelle Calves, Sébastien Artigaud, Carolyn S. Friedman, Christine Paillard, Jean Laroche & Claude Ferec ### Abstract This protocol permits the mutation scanning of PCR products by high-resolution DNA melting analysis requiring the inclusion of a saturating intercalating dye in the PCR mix without labelled probe. During a scanning process, fluorescent melting curves of PCR amplicons are analyzed. Mutations modifying melting curve shapes, are allowed...

  9. Viscosity Measurement for Tellurium Melt

    Science.gov (United States)

    Lin, Bochuan; Li, Chao; Ban, Heng; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2006-01-01

    The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

  10. Petrogenesis and geodynamic significance of silicic volcanism in the western Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Petrone, C. M.; Ferrari, L.; Orozco, M. A.; Lopez Martinez, M.

    2012-04-01

    Silicic volcanism in the western Trans-Mexican Volcanic Belt (WTMVB) was defined a Pliocene ignimbrite flare-up associated with the rifting of the Jalisco block from mainland Mexico (Frey et al., 2007; GSAB). With the integration of new and published geochronologic, geochemical, and isotope data we revise this interpretation and propose a new petrogenetic model. The oldest silicic volcanism consists of large silicic domes and minor pyroclastic flows (~370 km3) emplaced to the north of Guadalajara above a thick succession of ~11 to 8.7 Ma basaltic lavas, which yielded Ar-Ar and obsidian FT ages of ~7.5 to 5 Ma. Shortly after (4.9 to 2.9 Ma) large amount of rhyolitic lavas and ash flow tuffs (~500 km3) were emplaced in a WNW-ESE trending belt from Guadalajara to Compostela. Rhyolitic domes and flows (~430 km3) were emplaced also in the Pleistocene mostly between Tequila and Guadalajara with the late Pleistocene La Primavera caldera (~35 km3) as the sole explosive volcanic episodes. As a whole, silicic volcanism occurred from Late Miocene to the Pleistocene, and was dominated by dome and lava flows. Most rhyolites have high LILE/HFSE values and negative spikes at Nb, P and Ti. They also show the same Ba/Nb and K/Rb values and slightly higher Rb/Sr ratios as the 11-8 Ma basalts. Rhyolite Sr isotope data (87Sr/86Sr init = 0.70371 - 070598) are only slightly more radiogenic than the 11-8 basalts (87Sr/86Sr init = 0.70349-0.70410), whereas Nd isotope ratios are indistinguishable from them. Sr and Nd isotope ratios of the rhyolites are also similar to the crust nearby, indicating that they can be compatible either with fractional crystallization (FC) of basalts or with crust assimilation/melting. However REE contents are too low to be the result of basalt FC. Isotope and REE data can be successfully modelled with an initial crustal melt which subsequently undergone fractional crystallization of feldspar and quartz. Late Miocene slab detachment and subsequent slab rollback

  11. Interconnectivity of Fe O S liquid in polycrystalline silicate perovskite at lower mantle conditions

    Science.gov (United States)

    Terasaki, Hidenori; Frost, Daniel J.; Rubie, David C.; Langenhorst, Falko

    2007-05-01

    An important aspect of planetary core formation concerns whether interconnectivity of liquid metal can occur in crystalline silicates, which at low melt fractions requires that the dihedral angle between the two phases is Shannon, M.C., Agee, C.B., 1998. Percolation of core melts at lower mantle conditions. Science 280, 1059-1061] previously reported that dihedral angles in mantle assemblages decrease from 108° at upper mantle conditions to 71° at lower mantle conditions as a result of mineral phase transformations. Furthermore [Terasaki, H., Frost, D.J., Rubie, D.C., Langenhorst, F., 2005. The effect of oxygen and sulphur on dihedral angle between Fe-O-S melt and solid silicates under high pressure: implications for Martian core formation. Earth Planet. Sci. Lett. 232, 379-392] observed that dihedral angles between Fe-O-S liquid and solid silicates (olivine and ringwoodite) decrease to 66° at high oxygen and sulphur fugacities. Therefore, it may be possible for liquid metal to form an interconnected network at lower mantle conditions at high O and S fugacities. We have investigated the effects of the FeO content of perovskite, with Mg/(Mg + Fe) (Mg#) = 0.84-1.00, on the dihedral angle up to 23.5 GPa and 2223 K. Observed dihedral angles decrease significantly from 102° to 79° with increasing FeO content of the perovskite phase. This tendency is in good agreement with our previous dihedral angle results for olivine and ringwoodite. The dihedral angle is, however, still higher than the critical value of 60° at pressures of the top of the lower mantle, i.e. at this depth efficient core-mantle differentiation is not possible by a percolation mechanism.

  12. Centrifuge assisted percolation of Fe-S melts in partially molten peridotite: Time constraints for planetary core formation

    Science.gov (United States)

    Bagdassarov, N.; Solferino, G.; Golabek, G. J.; Schmidt, M. W.

    2009-10-01

    The mechanism which segregates molten Fe-S into metallic cores of planetary bodies is still not fully understood. Due to the high interfacial energy and wetting angle between Fe-S melts and silicate mantle minerals, the continuous percolative flow of such melts cannot be efficient for the core segregation in planetary bodies. A series of percolation experiments has been realized on a partially molten fertile garnet peridotite, employing a centrifuging piston cylinder. A high temperature garnet peridotite with Mg# ~0.90 composed of 60 vol.% olivine, 15 vol.% orthopyroxene, 6 vol.% clinopyroxene and 19 vol.% garnet has been used as the silicate matrix. Peridotite powders with the 100-200 or 20-30 µm grain size were mixed with 5-30 vol.% Fe-S of eutectic composition Fe 70S 30. The aggregates were centrifuged at 500-700 g at temperatures below and above the melting point of the peridotite. The centrifuge experiments revealed a negligible percolation of Fe-S melts through the unmolten peridotite matrix. Only at T > 1260 °C, i.e. above the solidus of the peridotite, and starting with 5 vol.% of Fe 70S 30 the vertical melt gradient achieved 1-2 vol.%/mm. In samples with 15 vol.% Fe 70S 30 the vertical separation achieved 2-2.5 vol.%/mm after 10 h of centrifuging at 500 g. An increase in the degree of partial silicate melting in the peridotite leads to an increase of the Fe-S separation rate from the peridotite matrix. Fe-S contents >10 vol.% cause an increase of the Fe-S melt droplet size and of the effective percolation velocity of Fe-S melt. A threshold dividing fast (>10 cm per year) and slow percolations (<1 mm per year) of Fe -S melt is found around 14-15 vol.% of Fe 70S 30. The experimentally determined permeabilities of Fe-S melt in the unmolten peridotite with 7-10 vol.% of Fe 70S 30 melt are 10 - 18 -10 - 19 m 2, which is 2-3 orders of magnitude lower than the values calculated previously from static experiments. The presence of the silicate melt increases the

  13. OXYGEN BUBBLE DEVELOPMENT ON A PLATINUM ELECTRODE IN BOROSILICATE GLASS MELT BY THE EFFECT OF ALTERNATING CURRENT

    Directory of Open Access Journals (Sweden)

    Jiri Matej

    2014-10-01

    or on alternating reduction and re-forming of oxidic layer on the electrode in the transition range, has been suggested. Start of bubble evolution at low alternating current density has also been observed in simple sodium-calcium-silicate glass melt. A relation between bubble release and platinum corrosion caused by reduced silicon has been suggested

  14. Vacuum melting and mechanical testing of simulated lunar glasses

    Science.gov (United States)

    Carsley, J. E.; Blacic, J. D.; Pletka, B. J.

    1992-01-01

    Lunar silicate glasses may possess superior mechanical properties compared to terrestrial glasses because the anhydrous lunar environment should prevent hydrolytic weakening of the strong Si-O bonds. This hypothesis was tested by melting, solidifying, and determining the fracture toughness of simulated mare and highlands composition glasses in a high vacuum chamber. The fracture toughness, K(IC), of the resulting glasses was obtained via microindentation techniques. K(IC) increased as the testing environment was changed from air to a vacuum of 10 exp -7 torr. However, this increase in toughness may not result solely from a reduction in the hydrolytic weakening effect; the vacuum-melting process produced both the formation of spinel crystallites on the surfaces of the glass samples and significant changes in the compositions which may have contributed to the improved K(IC).

  15. Melting of the Primitive Mercurian Mantle, Insights into the Origin of Its Surface Composition

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Rapp, J. F.; Ross, D. K.; Pando, K. M.; Danielson, L. R.; Fontaine, E.

    2016-01-01

    Recent findings of the MESSENGER mission on Mercury have brought new evidence for its reducing nature, widespread volcanism and surface compositional heteregeneity. MESSENGER also provided major elemental ratios of its surface that can be used to infer large-scale differentiation processes and the thermal history of the planet. Mercury is known as being very reduced, with very low Fe-content and high S and alkali contents on its surface. Its bulk composition is therefore likely close to EH enstatite chondrites. In order to elucidate the origin of the chemical diversity of Mercury's surface, we determined the melting properties of EH enstatite chondrites, at pressures between 1 bar and 3 GPa and oxygen fugacity of IW-3 to IW-5, using piston-cylinder experiments, combined with a previous study on EH4 melting at 1 bar. We found that the presence of Ca-rich sulfide melts induces significant decrease of Ca-content in silicate melts at low pressure and low degree of melting (F). Also at pressures lower than 3 GPa, the SiO2-content decreases with F, while it increases at 3 GPa. This is likely due to the chemical composition of the bulk silicate which has a (Mg+Fe+Ca)/Si ratio very close to 1 and to the change from incongruent to congruent melting of enstatite. We then tested whether the various chemical compositions of Mercury's surface can result from mixing between two melting products of EH chondrites. We found that the majority of the geochemical provinces of Mercury's surface can be explained by mixing of two melts, with the exception of the High-Al plains that require an Al-rich source. Our findings indicate that Mercury's surface could have been produced by polybaric melting of a relatively primitive mantle.

  16. Apatite: a new redox proxy for silicic magmas?

    Science.gov (United States)

    Miles, Andrew; Graham, Colin; Hawkesworth, Chris; Gillespie, Martin; Bromiley, Geoff; Hinton, Richard

    2015-04-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this presentation we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively[1]. This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO2=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions[2]. [1] Stephens, W. E., Whitley, J. E., Thirlwall, M. F. and Halliday, A. N. (1985) The Criffell zoned pluton: correlated behaviour of rare earth element abundances with isotopic systems. Contributions to Mineralogy and

  17. MELTS_Excel: A Microsoft Excel-based MELTS interface for research and teaching of magma properties and evolution

    Science.gov (United States)

    Gualda, Guilherme A. R.; Ghiorso, Mark S.

    2015-01-01

    thermodynamic modeling software MELTS is a powerful tool for investigating crystallization and melting in natural magmatic systems. Rhyolite-MELTS is a recalibration of MELTS that better captures the evolution of silicic magmas in the upper crust. The current interface of rhyolite-MELTS, while flexible, can be somewhat cumbersome for the novice. We present a new interface that uses web services consumed by a VBA backend in Microsoft Excel©. The interface is contained within a macro-enabled workbook, where the user can insert the model input information and initiate computations that are executed on a central server at OFM Research. Results of simple calculations are shown immediately within the interface itself. It is also possible to combine a sequence of calculations into an evolutionary path; the user can input starting and ending temperatures and pressures, temperature and pressure steps, and the prevailing oxidation conditions. The program shows partial updates at every step of the computations; at the conclusion of the calculations, a series of data sheets and diagrams are created in a separate workbook, which can be saved independently of the interface. Additionally, the user can specify a grid of temperatures and pressures and calculate a phase diagram showing the conditions at which different phases are present. The interface can be used to apply the rhyolite-MELTS geobarometer. We demonstrate applications of the interface using an example early-erupted Bishop Tuff composition. The interface is simple to use and flexible, but it requires an internet connection. The interface is distributed for free from http://melts.ofm-research.org.

  18. Experimental Constraints on the Partitioning Behavior of F, Cl, and OH Between Apatite and Basaltic Melt

    Science.gov (United States)

    McCubbin, Francis M.; Barnes, Jessica J.; Vander Kaaden, Kathleen E.; Boyce, Jeremy W.; Ustunisik, Gokce; Whitson, Eric S.

    2017-01-01

    The mineral apatite is present in a wide range of planetary materials. The presence of volatiles (F, Cl, and OH) within its crystal structure (X-site) have motivated numerous studies to investigate the partitioning behavior of F, Cl, and OH between apatite and silicate melt with the end goal of using apatite to constrain the volatile contents of planetary magmas and mantle sources. A number of recent experimental studies have investigated the apatite-melt partitioning behavior of F, Cl, and OH in magmatic systems. Apatite-melt partitioning of volatiles are best described as exchange equilibria similar to Fe-Mg partitioning between olivine and silicate melt. However, the partitioning behavior is likely to change as a function of temperature, pressure, oxygen fugacity, apatite composition, and melt composition. In the present study, we have conducted experiments to assess the partitioning behavior of F, Cl, and OH between apatite and silicate melt over a pressure range of 0-6 gigapascals, a temperature range of 950-1500 degrees Centigrade, and a wide range of apatite ternary compositions. All of the experiments were conducted between iron-wustite oxidation potentials IW minus 1 and IW plus 2 in a basaltic melt composition. The experimental run products were analyzed by a combination of electron probe microanalysis and secondary ion mass spectrometry (NanoSIMS). Temperature, apatite crystal chemistry, and pressure all play important roles in the partitioning behavior of F, Cl, and OH between apatite and silicate melt. In portions of apatite ternary space that undergo ideal mixing of F, Cl, and OH, exchange coefficients remain constant at constant temperature and pressure. However, exchange coefficients vary at constant temperature (T) and pressure (P) in portions of apatite compositional space where F, Cl, and OH do not mix ideally in apatite. The variation in exchange coefficients exhibited by apatite that does not undergo ideal mixing far exceeds the variations

  19. Valence State Partitioning of Cr and V Between Olivine-Melt and Pyroxene-Melt in Experimental Basalts of a Eucritic Composition

    Science.gov (United States)

    Karner, J. M.; Jones, J. H.; Le, L.

    2017-01-01

    The partitioning of multivalent elements in basaltic systems can elucidate the oxygen fugacity (fO2) conditions under which basalts formed on planetary bodies (Earth, Moon, Mars, asteroids). Chromium and V are minor and trace elements in basaltic melts, partition into several minerals that crystallize from basaltic melts, exist in multiple valence states at differing fO2 conditions, and can therefore be used as oxybarometers for basaltic melts. Chromium is mostly 3+ in terrestrial basaltic melts at relatively high fO2 values (= IW+3.5), and mostly 2+ in melts at low fO2 values (= IW-1), such as those on the Moon and some asteroids. At intermediate fO2s, (i.e., IW-1 to IW+3.5), basaltic melts contain both Cr3+ and Cr2+. Vanadium in basaltic melts is mostly 4+ at high fO2, mostly 3+ at low fO2, and a mix of V3+ and V4+ at intermediate fO2 con-ditions. Understanding the partitioning of Cr and V into silicate phases with changing fO2 is therefore critical to the employment of Cr and V oxybarometers. In this abstract we examine the equilibrium partitioning of Cr and V between olivine/melt and pyroxene/melt in experimental charges of a eucritic composition produced at differing fO2 conditions. This study will add to the experimental data on DCr and DV (i.e., olivine/melt, pyroxene/melt) at differing fO2, and in turn these D values will be used to assess the fO2 of eucrite basalts and perhaps other compositionally similar planetary basalts.

  20. Hydrothermal Synthesis of Dicalcium Silicate Based Cement

    Science.gov (United States)

    Dutta, N.; Chatterjee, A.

    2017-06-01

    It is imperative to develop low energy alternative binders considering the large amounts of energy consumed as well as carbon dioxide emissions involved in the manufacturing of ordinary Portland cement. This study is on the synthesis of a dicalcium silicate based binder using a low temperature hydrothermal route.The process consists of synthesizing an intermediate product consisting of a calcium silicate hydrate phase with a Ca:Si ratio of 2:1 and further thermal treatment to produce the β-Ca2SiO4 (C2S) phase.Effect of various synthesis parameters like water to solid ratio, dwell time and temperature on the formation of the desired calcium silicate hydrate phase is reported along with effect of heating conditions for formation of the β-C2S phase. Around 77.45% of β-C2S phase was synthesized by thermal treatment of the intermediate phase at 820°C.

  1. Silicate mineral dissolution during heap bioleaching.

    Science.gov (United States)

    Dopson, Mark; Halinen, Anna-Kaisa; Rahunen, Nelli; Boström, Dan; Sundkvist, Jan-Eric; Riekkola-Vanhanen, Marja; Kaksonen, Anna H; Puhakka, Jaakko A

    2008-03-01

    Silicate minerals are present in association with metal sulfides in ores and their dissolution occurs when the sulfide minerals are bioleached in heaps for metal recovery. It has previously been suggested that silicate mineral dissolution can affect mineral bioleaching by acid consumption, release of trace elements, and increasing the viscosity of the leach solution. In this study, the effect of silicates present in three separate samples in conjunction with chalcopyrite and a complex multi-metal sulfide ore on heap bioleaching was evaluated in column bioreactors. Fe(2+) oxidation was inhibited in columns containing chalcopyrite samples A and C that leached 1.79 and 1.11 mM fluoride, respectively but not in sample B that contained 0.14 mM fluoride. Microbial Fe(2+) oxidation inhibition experiments containing elevated fluoride concentrations and measurements of fluoride release from the chalcopyrite ores supported that inhibition of Fe(2+) oxidation during column leaching of two of the chalcopyrite ores was due to fluoride toxicity. Column bioleaching of the complex sulfide ore was carried out at various temperatures (7-50 degrees C) and pH values (1.5-3.0). Column leaching at pH 1.5 and 2.0 resulted in increased acid consumption rates and silicate dissolution such that it became difficult to filter the leach solutions and for the leach liquor to percolate through the column. However, column temperature (at pH 2.5) only had a minor effect on the acid consumption and silicate dissolution rates. This study demonstrates the potential negative impact of silicate mineral dissolution on heap bioleaching by microbial inhibition and liquid flow. Copyright 2007 Wiley Periodicals, Inc.

  2. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  3. Valence and metal/silicate partitioning of Mo: Implications for conditions of Earth accretion and core formation

    Science.gov (United States)

    Righter, K.; Danielson, L. R.; Pando, K. M.; Shofner, G. A.; Sutton, S. R.; Newville, M.; Lee, C.-T.

    2016-03-01

    To better understand and predict the partition coefficient of Mo at the conditions of the deep interior of Earth and other terrestrial planets or bodies, we have undertaken new measurements of the valence and partitioning of Mo. X-ray absorption near edge structure (XANES) K-edge spectra for Mo have been measured in a series of Fe-bearing glasses produced at 1 bar and higher PT conditions. High pressure experiments have been carried out up to 19 GPa in order to better understand the effect of pressure on Mo partitioning. And, finally, a series of experiments at very low fO2 conditions and high Si content metallic liquids has been carried out to constrain the effect of Si on the partitioning of Mo between metallic liquids and silicate melt. The valence measurements demonstrate that Mo undergoes a transition from 4+ to 6+ near IW-1, in general agreement with previous 1 bar studies on FeO-free silicate melts. High pressure experiments demonstrate a modest pressure dependence of D (Mo) metal/silicate and, combined with previous results, show a significant decrease with pressure that must be quantified in any predictive expression. Finally, the effect of dissolved Si in Fe-rich metallic liquid is to decrease D (Mo) significantly, as suggested by previous work in metallurgical systems. The effect of pressure, temperature, oxygen fugacity, metallic liquid composition, and silicate melt composition can be quantified by using multiple linear regression of available experimental data for Mo. Our XANES results show that Mo will be 4+ at conditions of core formation, so only experiments carried out at fO2 of IW-1 and lower were used in the regressions. Application of predictive expressions to Earth accretion shows that D (Mo) decreases to values consistent with an equilibrium scenario for early Earth core-mantle. The Mo content of the primitive upper mantle (PUM) can be attained by metal-silicate equilibrium involving S-, C-, and Si-bearing metallic liquid, and peridotite

  4. Occurrence and mineral chemistry of chromite and related silicates from the Hongshishan mafic-ultramafic complex, NW China with petrogenetic implications

    Science.gov (United States)

    Ruan, Banxiao; Yu, Yingmin; Lv, Xinbiao; Feng, Jing; Wei, Wei; Wu, Chunming; Wang, Heng

    2017-10-01

    The Hongshishan mafic-ultramafic complex is located in the western Beishan Terrane, NW China, and hosts an economic Ni-Cu deposit. Chromite as accessory mineral from the complex is divided into three types based on its occurrence and morphology. Quantitative electron probe microanalysis (EPMA) have been conducted on the different types of chromites. Type 1 chromite occurs as inclusions within silicate minerals and has relatively homogeneous composition. Type 2 chromite occurs among serpentine, as interstitial phase. Type 3 chromite is zoned and exhibits a sudden change in compositions from core to rim. Type 1 chromite occurs in olivine gabbro and troctolite showing homogeneous composition. This chromite is more likely primary. Interstitial type 2 and zoned type 3 chromite has compositional variation from core to rim and is more likely modified. Abundant inclusions of orthopyroxene, phlogopite and hornblende occur within type 2 and type 3 chromites. The parental melt of type 1 chromite has an estimated composition of 14.5 wt% MgO, 12.3 wt% Al2O3 and 1.9 wt% TiO2 and is characterized by high temperature, picritic affinity, hydrous nature and high Mg and Ti contents. Compositions of chromite and clinopyroxene are distinct from those of Alaskan-type complexes and imply that the subduction-related environment is not reasonable. Post orogenic extension and the early Permian mantle plume are responsible for the emplacement of mafic-ultramafic complexes in the Beishan Terrane. The cores of zoned chromites are classified as ferrous chromite and the rims as ferrian chromite. The formation of ferrian rim involves reaction of ferrous chromite, forsterite and magnetite to produce ferrian chromite and chlorite, or alternaively, the rim can be simply envisioned as the result of external addition of magnetite in solution to the already formed ferrous chromite.

  5. Melting graft wound syndrome

    Directory of Open Access Journals (Sweden)

    Shiou-Mei Chen

    2017-09-01

    Full Text Available Melting graft wound syndrome is characterized by progressive epidermal loss from a previously well-taken skin graft, healed burn, or donor site. It may result in considerable morbidity and require prolonged treatment. We report a 23-year-old flame-burned patient with second- to third-degree burns involving more than 70% of the total body surface area, whose condition was complicated with septic shock. The patient presented with erosions and ulcers occurring on previously well-taken skin graft recipient sites over both legs and progressive epidermal loss on donor sites over the back. The patient's presentation was compatible with the diagnosis of melting graft wound syndrome, and we successfully treated the patient with debridement and supportive treatment.

  6. Undersaturated Volatile Contents in MORB, Evidence for Re-Melting Episodes

    Science.gov (United States)

    Saal, A. E.; Hauri, E.; Langmuir, C. H.; Perfit, M.

    2001-12-01

    We present here the first report of undersaturated volatile contents for one of the most primitive suites from the EPR, the picritic lavas from the Siqueiros intra-transform spreading centers. We studied olivine-hosted (Fo 90-91) primary melt inclusions and their host glasses from lavas erupted at approximately 3900 meters below sea level. The study of melt inclusions and deep erupted glasses allows us to determine the primary volatile contents of the Siqueiros lavas, avoiding the effect of degassing occurring during eruption. The melt inclusions and glasses have refractory major and trace element compositions, with the most depleted compositions having strong enrichment in Sr content compared to elements of similar compatibility. The primitive-mantle-normalized trace element patterns of these depleted inclusions resemble those of plagioclase-rich cumulates occurring in the lower oceanic crust and in massif peridotites. The Siqueiros glasses and olivine-hosted melt inclusions are undersaturated in H2O-CO2, Cl and F, and range from barely saturated to undersaturated in S contents. The undersaturation in volatile contents of these glasses and melt inclusions is consistent with the low vesicularity of the Siqueiros picritic lavas (Siqueiros melt inclusions and glasses can be explained by low extent of melting (1-5 %) of residual peridotite, left after the extraction of MORBs, and Associated veins of plagioclase-rich cumulates generated during MORB differentiation and interaction with the residual mantle. Our results have important implications for our interpretation of MORB geochemistry. For example, melting of young (<10,000 years) depleted peridotite left after the extraction of MORB with associated plagioclase-rich cumulate can give an alternative explanation to the extreme 226Ra excess found in MORBs.

  7. Quaternary ammonium borohydride adsorption in mesoporous silicate MCM-48

    Energy Technology Data Exchange (ETDEWEB)

    Wolverton, Michael J [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika A [Los Alamos National Laboratory

    2010-01-01

    Inorganic borohydrides have a high gravimetric hydrogen density but release H2 only under energetically unfavorable conditions. Surface chemistry may help in lowering thermodynamic barriers, but inclusion of inorganic borohydrides in porous silica materials has proved hitherto difficult or impossible. We show that borohydrides with a large organic cation are readily adsorbed inside mesoporous silicates, particularly after surface treatment. Thermal analysis reveals that the decomposition thermodynamics of tetraalkylammonium borohydrides are substantially affected by inclusion in MCM-48. Inelastic neutron scattering (INS) data show that the compounds adsorb on the silica surface. Evidence of pore loading is supplemented by DSC/TGA, XRD, FTIR, and BET isotherm measurements. Mass spectrometry shows significant hydrogen release at lower temperature from adsorbed borohydrides in comparison with the bulk borohydrides. INS data measured for partially decomposed samples indicates that the decomposition of the cation and anion is likely simultaneous. Additionally, these data confirm the formation of Si-H bonds on the silica surface upon decomposition of adsorbed tetramethylammonium borohydride.

  8. Limits to Inclusion

    Science.gov (United States)

    Hansen, Janne Hedegaard

    2012-01-01

    In this article, I will argue that a theoretical identification of the limit to inclusion is needed in the conceptual identification of inclusion. On the one hand, inclusion is formulated as a vision that is, in principle, limitless. On the other hand, there seems to be an agreement that inclusion has a limit in the pedagogical practice. However,…

  9. Making Earth's earliest continental crust - an analogue from voluminous Neogene silicic volcanism in NE-Iceland

    Science.gov (United States)

    Berg, Sylvia E.; Troll, Valentin R.; Burchardt, Steffi; Riishuus, Morten S.; Deegan, Frances M.; Harris, Chris; Whitehouse, Martin J.; Gústafsson, Ludvik E.

    2014-05-01

    Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocks in Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standing controversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach 25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual ≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of the voluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained (c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces. Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement of silicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbrite eruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacite lava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated from zircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g. typically δ18O = 0 ‰, Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of an off-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson & Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basaltic crust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Such rapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generating continental crust in a subduction-free early Earth (e.g. ≥ 3 Ga, Kamber et

  10. Social imaginaries and inclusion

    DEFF Research Database (Denmark)

    Hansen, Janne Hedegaard

    2016-01-01

    The main goal of this entry is to introduce inclusion as a sociological concept consistent with which exclusion is an internal part of inclusion. When exclusion is the basis of inclusion, the establishment of communities will always involve both inclusion and exclusion processes. Similarly......, the development of inclusive schools and inclusive learning environments will involve both inclusion and exclusion processes. With this starting point, international educational research knowledge about inclusive schools and inclusive learning environments in general will be related to the fundamental dilemma...... that inclusion on the one hand may be seen to be about human rights, solidarity, and democracy, and on the other hand, it is about ensuring the cohesion of neoliberal society by means of every person’s obligation to realize one’s potential through learning, development, and education regardless of one’s needs...

  11. Polymer-organoclay nanocomposites by melt processing

    Science.gov (United States)

    Cui, Lili

    2009-12-01

    Polymer-layered silicate nanocomposites based on a variety of polymer matrices and several organoclays were prepared by melt processing. A detailed characterization of the thermal degradation of several commercial and experimental organoclays often used to form polymer nanocomposites was reported. The surfactant type, loading, and purification level of organoclay significantly affect their thermal stability; however, broadly speaking, the results suggest that these differences in thermal stability do not appear to have much effect on the morphology and properties of the nanocomposites formed from them. It seems that the thermal stability of organoclays is not the key factor in organoclay exfoliation in melt processed polymer nanocomposites, since the exfoliation/dispersion process may have been completed on a time scale before the degradation of surfactant progresses to a detrimental level. Polymer nanocomposites have been made from a variety of polymers; however, few matrices have demonstrated the ability to readily exfoliate the organoclay as well as nylon 6, especially for highly hydrophobic materials like polyolefins. Hence, a significant part of this research work was devoted to explore various routes to improve polyolefin-organoclay interactions, and thus, organoclay exfoliation in these systems. Amine grafted polypropylenes and a conventionally used maleic anhydride grafted polypropylene were used as compatibilizers for polypropylene based nanocomposites to improve the organoclay exfoliation. A series of ethylene vinyl acetate copolymers, the polarity of which can be adjusted by varying their vinyl acetate contents, based nanocomposites were prepared as the model system to address the relationship between the polarity of the polymers and their preferences over various organoclay structures. Attempts were made to explore the effect of degree of neutralization of acid groups in ionomers on the morphology and properties of nanocomposites, and it seems that the

  12. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption e...

  13. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    Silicate based bioceramics are promising candidates as biomaterials for tissue engineering. The combustion synthesis method provides control on the morphology and particle size of the synthesized material. This paper discusses the combustion synthesis of akermanite (Ca2MgSi2O7 and Sr2MgSi2O7), which has been ...

  14. High-pressure phases in shock-induced melt veins of the Umbarger l6 chondrite: Constraints of shock pressure

    Science.gov (United States)

    Xie, Zhidong; Sharp, Thomas G.

    2004-12-01

    We report a previously undocumented set of high-pressure minerals in shock-induced melt veins of the Umbarger L6 chondrite. High-pressure minerals were identified with TEM using selected-area electron diffraction, and energy-dispersive X-ray spectroscopy. Ringwoodite (Fa30), akimotoite (En11Fs89), and augite (En42Wo33Fs25) were found in the silicate matrix of the melt vein, representing the crystallization from a silicate melt during the shock pulse. Ringwoodite (Fa27) and hollandite-structured plagioclase were also found as polycrystalline aggregates in the melt vein, representing solid-state transformation or melting with subsequent crystallization of entrained host-rock fragments in the vein. In addition, Fe2SiO4-spinel (Fa66-Fa99) and stishovite crystallized from a FeO-SiO2-rich zone in the melt vein, which formed by shock melting of FeO-SiO2-rich material that had been altered and metasomatized prior to shock. Based on the pressure stabilities of the high-pressure minerals, ringwoodite, akimotoite, and Ca-clinopyroxene, the melt vein crystallized at approximately 18 GPa. The Fe2SiO4-spinel + stishovite assemblage in the FeO-SiO2-rich melts is consistent with crystallization of the melt-vein matrix at the pressure up to 18 GPa. The crystallization pressure of ?18 GPa is much lower than the 45-90 GPa pressure one would conclude from the S6 shock effects in melt veins (St?ffler et al. 1991) and somewhat less than the 25-30 GPa inferred from S5 shock effects (Schmitt 2000) found in the bulk rock.

  15. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    The silicon contents in the roots of the miniature rose treated with polymer sodium silicate were significantly greater than that in plants treated with monomer sodium silicate. In conclusion, the suppressive effects of sodium silicate in the polymer form were confirmed against powdery mildew and root rot diseases of the ...

  16. The role of water in silicate oligomerization reaction

    NARCIS (Netherlands)

    Trinh, T.T.; Jansen, A.P.J.; Santen, R.A.; Meijer, E.J.

    2009-01-01

    The silicate oligomerization reaction is key to sol-gel chemistry and zeolite synthesis. Numerous experimental and theoretical studies have been devoted to investigating the physical chemistry of silicate oligomers in the prenucleation stage of siliceous zeolite formation. Most of the previous

  17. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Mohsen

    2015-10-21

    Oct 21, 2015 ... Sodium silicate was dissolved in water in either a monomer form or polymer form; the effects of both forms of sodium silicate aqueous solution on rose powdery mildew and root rot diseases of miniature rose were examined. Both forms of sodium silicate aqueous solution were applied to the roots of the.

  18. Electronic environments of ferrous iron in rhyolitic and basaltic glasses at high pressure: Silicate Glasses at High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Solomatova, Natalia V. [Division of Geological and Planetary Sciences, Caltech, Pasadena California USA; Jackson, Jennifer M. [Division of Geological and Planetary Sciences, Caltech, Pasadena California USA; Sturhahn, Wolfgang [Division of Geological and Planetary Sciences, Caltech, Pasadena California USA; Rossman, George R. [Division of Geological and Planetary Sciences, Caltech, Pasadena California USA; Roskosz, Mathieu [IMPMC-Muséum National d' Histoire Naturelle-CNRS, Paris France

    2017-08-01

    The physical properties of silicate melts within Earth's mantle affect the chemical and thermal evolution of its interior. Chemistry and coordination environments affect such properties. We have measured the hyperfine parameters of iron-bearing rhyolitic and basaltic glasses up to ~120 GPa and ~100 GPa, respectively, in a neon pressure medium using time domain synchrotron Mössbauer spectroscopy. The spectra for rhyolitic and basaltic glasses are well explained by three high-spin Fe2+-like sites with distinct quadrupole splittings. Absence of detectable ferric iron was confirmed with optical absorption spectroscopy. The sites with relatively high and intermediate quadrupole splittings are likely a result of fivefold and sixfold coordination environments of ferrous iron that transition to higher coordination with increasing pressure. The ferrous site with a relatively low quadrupole splitting and isomer shift at low pressures may be related to a fourfold or a second fivefold ferrous iron site, which transitions to higher coordination in basaltic glass, but likely remains in low coordination in rhyolitic glass. These results indicate that iron experiences changes in its coordination environment with increasing pressure without undergoing a high-spin to low-spin transition. We compare our results to the hyperfine parameters of silicate glasses of different compositions. With the assumption that coordination environments in silicate glasses may serve as a good indicator for those in a melt, this study suggests that ferrous iron in chemically complex silicate melts likely exists in a high-spin state throughout most of Earth's mantle.

  19. Optical analysis of samarium doped sodium bismuth silicate glass.

    Science.gov (United States)

    Thomas, V; Sofin, R G S; Allen, M; Thomas, H; Biju, P R; Jose, G; Unnikrishnan, N V

    2017-01-15

    Samarium doped sodium bismuth silicate glass was synthesized using the melt quenching method. Detailed optical spectroscopic studies of the glassy material were carried out in the UV-Vis-NIR spectral range. Using the optical absorption spectra Judd-Ofelt (JO) parameters are derived. The calculated values of the JO parameters are utilized in evaluating the various radiative parameters such as electric dipole line strengths (Sed), radiative transition probabilities (Arad), radiative lifetimes (τrad), fluorescence branching ratios (β) and the integrated absorption cross- sections (σa) for stimulated emission from various excited states of Sm3+‡ ion. The principal fluorescence transitions are identified by recording the fluorescence spectrum. Our analysis revealed that the novel glassy system has the optimum values for the key parameters viz. spectroscopic quality factor, optical gain, stimulated emission cross section and quantum efficiency, which are required for a high performance optical amplifier. Calculated chromaticity co-ordinates (0.61, 0.38) also confirm its application potential in display devices. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Melting the Divide

    Science.gov (United States)

    Gibson, S. M.

    2014-12-01

    Presenting Quaternary Environmental Change to students who fall into Widening Participation criteria at the University of Cambridge, gives a unique opportunity to present academic debate in an approachable and entertaining way. Literally by discussing the melting of our ice caps, melts the divide Cambridge has between its reputation and the reality for the brightest, underprivileged, students. There is a balance between presenting cutting edge research with the need to come across as accessible (and importantly valuable to "learning"). Climate change over the Quaternary lends itself well to this aim. By lecturing groups of potential students through the entire Quaternary in an hour, stopping to discuss how our ancestors interacted with past Interglacials and what are the mechanisms driving change (in generalized terms), you are able to introduce cutting edge research (such as the latest NEEM ice core) to the students. This shows the evolution and importance of higher education and academic research. The lecture leads well onto group discussions (termed "supervisions" in Cambridge), to explore their opinions on the concern for present Anthropogenic Climate Change in relation to Past Climate Change after being presented with images that our ancestors "made it". Here discussion thrives off students saying obvious things (or sarcastic comments!) which quickly can lead into a deep technical discussion on their terms. Such discussions give the students a zest for higher education, simply throwing Ruddiman's (2003) "The Anthroprocene Started Several Thousand Years Ago" at them, questions in a second their concept of Anthropogenic Climate Change. Supervisions lend themselves well to bright, articulate, students and by offering these experiences to students of Widening Participation criteria we quickly melt the divide between the reputation of Cambridge ( and higher education as a whole) and the day to day practice. Higher education is not for the privileged, but a free and

  1. Sulfide in the core and the Nd isotopic composition of the silicate Earth

    Science.gov (United States)

    McCoy-West, A.; Millet, M. A.; Nowell, G. M.; Wohlers, A.; Wood, B. J.; Burton, K. W.

    2016-12-01

    The chemical composition of the Earth is traditionally explained in terms of evolution from a solar-like composition, similar to that found in primitive chondritic meteorites. It now appears, however, that the silicate Earth is not chondritic, but depleted in incompatible elements and a resovable 20 ppm excess is observed in 142Nd relative to chondirtes [1, 2]. This anomaly requires a process that occurred within 30 Myr of solar system formation and has been variably ascribed to: a complementary enriched reservoir in the deep Earth [1]; loss to space through collisional erosion [3]; or the inhertence of nucleosynthetic anomalies [4]. Sulfide in the core may provide a reservoir capable of balancing the composition of the silicate Earth. Recent experimental work suggests that the core contains a significant proportion of sulfide, added during the final stages of accretion and new data suggests that at high pressures sulfide can incorporate a substantial amount of refractory lithophile and heat-producing elements [5]. The drawback of the short-lived 146Sm-142Nd radiogenic isotope system is that it is not possible to distinguish between fractionations of Sm/Nd that occurs during silicate melting or segregation of a sulfide-melt. Neodymium stable isotopes have the potential to provide just such a tracer of sulfide segregation, because there is a significant contrast in bonding environment between sulfide and silicate, where heavy isotopes should be preferentially incorporated into high force-constant bonds involving REE3+ (i.e. the silicate mantle). Preliminary data indicate that mantle rocks do indeed possess heavier 146Nd/144Nd values than chondritic meteorites by 0.3 ‰, consistent with the removal of light Nd into sulfide in the core, driving the residual mantle to heavier values. Overall, our isotope and elemental data indicate that the rare earths and other incompatible elements are substantially incorporated into sulfide. While Nd stable isotope data for

  2. Melting Layer Survey.

    Science.gov (United States)

    1983-08-12

    AFGL Melting Layer study was begun in 1979. Original plans called for a flight program and extensive radar studies. Budget problems and a change in the...etrstlr’nrL, ., (ot-i \\v! A ;uo. 1’.. ,ind (;u(,. V. . t1 97:10 1 inal 1, pov1 to NSIl 1-ide: Grint No. (1A-2!525. ( 5 Ne’% )ork, ppu 410-415. (1...1958) The hail problem , Nubila 1:11-96. (3) 98. Ludlam, R. H. (1980) Clouds and Storms, The Pennsylvania State University Press, University Park

  3. Mantle-derived fluids in diamond micro-inclusions

    Science.gov (United States)

    Navon, O.; Hutcheon, I. D.; Rossman, G. R.; Wasserburg, G. J.

    1988-01-01

    Microinclusions in diamonds from Zaire and Botswana differ in composition from the more common large inclusions of the peridotitic or eclogitic assemblages. These sub-micrometer inclusions resemble potassic magmas in their composition, but are enriched in H2O, CO2(3-), and K2O and depleted in MgO. This composition represents a volatile-rich fluid or melt from the upper mantle, which was trapped in the diamonds as they grew.

  4. Roadmap for Inclusive Innovation

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — The Roadmap for Inclusive Innovation data set shares the status of action items under the Roadmap for Inclusive Innovation. Each action or project has been assigned...

  5. Teachers becoming inclusive practitioners

    African Journals Online (AJOL)

    , construct their identities in the light of inclusive education, and how they negotiate the tensions and contradictions emerging from the processof becoming inclusive practitioners. Central to this discussion is the understanding that teachers' ...

  6. Accumulation of melt and volatiles at the base of the lithosphere: Implications for the origin of the EMORB geochemical reservoir and seismic G-discontinuity

    Science.gov (United States)

    Hirth, G.; Parmentier, E.; Saal, A. E.

    2010-12-01

    Motivated by the location of the Gutenberg (G) Discontinuity and the requirement for a relatively isolated and young source for Enriched, Mid-Ocean Ridge Basalt (E-MORB), we suggest that melt and associated volatile components (CO2 and H2O) accumulate at the base of oceanic plates. Our model is based on analysis of (rapid) migration of very buoyant, low viscosity carbonate melt to the base of the plate. Melts are produced by mantle upwelling that results in decompression melting at the carbonated mantle solidus at depths up to ~300 km. These melts scavenge water and CO2 from the mantle, leading to the accumulation of volatiles at the base of the plate that promotes the stability of carbonated-silicate melt at sub-adiabatic temperatures. We hypothesize that the dehydration boundary created by ridge melting marks the limit of the melt accumulation zone. The G-discontinuity is represented by the velocity decrease associated with the top of the melt accumulation zone where the melt fraction is ~0.5-1% Hirschmann (2009) provides a foundation for exploring the role of melt accumulation on this problem. He calculates the degree of melting (F) as a function of P and T for various assumptions of mantle volatile composition. For standard MORB-source volatile concentrations, the melt fraction at the base of the plate is rather modest - and changes with age in a manner that makes it difficult to explain the G discontinuity. However, over the average age of an oceanic plate, our analysis of the kinetics of melt migration indicates a significant amount of the low degree melt can accumulate - amplifying the velocity contrast at the base of the plate. The “enriched” melt may then be recycled via subduction and subsequent upwelling to provide the source of E-MORB. Several factors may enhance this recycling process. First, some fraction of the volatile-rich melt may freeze at the base of the plate. Second, melt mobility will be significantly decreased by the transition from

  7. Foresighting for Inclusive Development

    DEFF Research Database (Denmark)

    Dahl Andersen, Allan; Andersen, Per Dannemand

    We propose that foresight can contribute to inclusive development by making innovation policy processes more inclusive, which in turn makes innovation systems more inclusive. Processes of developing future-oriented innovation policies are often unsuccessful and rarely inclusive. We conceptualize ...... and processes in two foresight cases in two emerging economies - Brazil and South Korea. Although the research is exploratory and the results tentative, the empirical studies support our main propositions....

  8. Early metal-silicate differentiation during planetesimal formation revealed by acapulcoite and lodranite meteorites

    Science.gov (United States)

    Dhaliwal, Jasmeet K.; Day, James M. D.; Corder, Christopher A.; Tait, Kim T.; Marti, Kurt; Assayag, Nelly; Cartigny, Pierre; Rumble, Doug; Taylor, Lawrence A.

    2017-11-01

    In order to establish the role and expression of silicate-metal fractionation in early planetesimal bodies, we have conducted a highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance and 187Re-187Os study of acapulcoite-lodranite meteorites. These data are reported with new petrography, mineral chemistry, bulk-rock major and trace element geochemistry, and oxygen isotopes for Acapulco, Allan Hills (ALHA) 81187, Meteorite Hills (MET) 01195, Northwest Africa (NWA) 2871, NWA 4833, NWA 4875, NWA 7474 and two examples of transitional acapulcoite-lodranites, Elephant Moraine (EET) 84302 and Graves Nunataks (GRA) 95209. These data support previous studies that indicate that these meteorites are linked to the same parent body and exhibit limited degrees (2 × CI chondrite) HSE abundances in transitional acapulcoite-lodranite meteorites (EET 84302, GRA 95209). All of the meteorites have chondritic Re/Os with measured 187Os/188Os ratios of 0.1271 ± 0.0040 (2 St. Dev.). These geochemical characteristics imply that the precursor material of the acapulcoites and lodranites was broadly chondritic in composition, and were then heated and subject to melting of metal and sulfide in the Fe-Ni-S system. This resulted in metallic melt removal and accumulation to form lodranites and transitional acapulcoite-lodranites. There is considerable variation in the absolute abundances of the HSE, both among samples and between aliquots of the same sample, consistent with both inhomogeneous distribution of HSE-rich metal, and of heterogeneous melting and incomplete mixing of silicate material within the acapulcoite-lodranite parent body. Oxygen isotope data for acapulcoite-lodranites are also consistent with inhomogeneous melting and mixing of accreted components from different nebular sources, and do not form a well-defined mass-dependent fractionation line. Modeling of HSE inter-element fractionation suggests a continuum of melting in the Fe-Ni-S system and partitioning between

  9. Melting temperature of archaeometallurgical slag

    Directory of Open Access Journals (Sweden)

    Jozef Petrík

    2013-12-01

    Full Text Available The aim of submitted work is to search the softening and melting temperature of archeometallurgy bloomery and blast furnace slag using high – temperature microscope. The high values of melting temperature of bloomery slag is a result of secondary oxidation of wüstite in the chamber of a microscope. The melting temperature increases with an increase in SiO2 and decreases with increasing basicity of the slag.

  10. Thermodynamics of freezing and melting

    OpenAIRE

    Pedersen, Ulf Rørbæk; Costigliola, Lorenzo; Bailey, Nicholas; Schrøder, Thomas; Dyre, Jeppe C.

    2016-01-01

    Although the freezing of liquids and melting of crystals are fundamental for many areas of the sciences, even simple properties like the temperature?pressure relation along the melting line cannot be predicted today. Here we present a theory in which properties of the coexisting crystal and liquid phases at a single thermodynamic state point provide the basis for calculating the pressure, density and entropy of fusion as functions of temperature along the melting line, as well as the variatio...

  11. MAFIC INCLUSIONS AND MINGLING STRUCTURES IN APLITES OF THE OSHURKOV MASSIF (WESTERN TRANSBAIKALIA

    Directory of Open Access Journals (Sweden)

    M. O. Rampilov

    2017-01-01

    Full Text Available Our study of aplite dykes cross‐cutting the Oshurkov basite massif revealed drop‐shaped inclusions of the monzonite composition. These are crystallized drops of basite melts, which show traces of the interaction with the host acidic melt. The Ar‐Ar method was applied to determine the age of the aplites (114.9 Ma for biotite and the monzonite inclusions (123.3 Ma for amphibole.

  12. Hard X-ray irradiation of cosmic silicate analogs: structural evolution and astrophysical implications

    Science.gov (United States)

    Gavilan, L.; Jäger, C.; Simionovici, A.; Lemaire, J. L.; Sabri, T.; Foy, E.; Yagoubi, S.; Henning, T.; Salomon, D.; Martinez-Criado, G.

    2016-03-01

    Context. Protoplanetary disks, interstellar clouds, and active galactic nuclei contain X-ray-dominated regions. X-rays interact with the dust and gas present in such environments. While a few laboratory X-ray irradiation experiments have been performed on ices, X-ray irradiation experiments on bare cosmic dust analogs have been scarce up to now. Aims: Our goal is to study the effects of hard X-rays on cosmic dust analogs via in situ X-ray diffraction. By using a hard X-ray synchrotron nanobeam, we seek to simulate cumulative X-ray exposure on dust grains during their lifetime in these astrophysical environments and provide an upper limit on the effect of hard X-rays on dust grain structure. Methods: We prepared enstatite (MgSiO3) nanograins, which are analogs to cosmic silicates, via the melting-quenching technique. These amorphous grains were then annealed to obtain polycrystalline grains. These were characterized via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) before irradiation. Powder samples were prepared in X-ray transparent substrates and were irradiated with hard X-rays nanobeams (29.4 keV) provided by beamline ID16B of the European Synchrotron Radiation Facility (Grenoble). X-ray diffraction images were recorded in transmission mode, and the ensuing diffractograms were analyzed as a function of the total X-ray exposure time. Results: We detected the amorphization of polycrystalline silicates embedded in an organic matrix after an accumulated X-ray exposure of 6.4 × 1027 eV cm-2. Pure crystalline silicate grains (without resin) do not exhibit amorphization. None of the amorphous silicate samples (pure and embedded in resin) underwent crystallization. We analyze the evolution of the polycrystalline sample embedded in an organic matrix as a function of X-ray exposure. Conclusions: Loss of diffraction peak intensity, peak broadening, and the disappearance of discrete spots and arcs reveal the amorphization

  13. Siliceous spicules enhance fracture-resistance and stiffness of pre-colonial Amazonian ceramics

    Science.gov (United States)

    Natalio, Filipe; Corrales, Tomas P.; Wanka, Stephanie; Zaslansky, Paul; Kappl, Michael; Lima, Helena Pinto; Butt, Hans-Jürgen; Tremel, Wolfgang

    2015-08-01

    Pottery was a traditional art and technology form in pre-colonial Amazonian civilizations, widely used for cultural expression objects, utensils and as cooking vessels. Abundance and workability of clay made it an excellent choice. However, inferior mechanical properties constrained their functionality and durability. The inclusion of reinforcement particles is a possible route to improve its resistance to mechanical and thermal damage. The Amazonian civilizations incorporated freshwater tree sponge spicules (cauixí) into the clay presumably to prevent shrinkage and crack propagation during drying, firing and cooking. Here we show that isolated siliceous spicules are almost defect-free glass fibres with exceptional mechanical stability. After firing, the spicule Young’s modulus increases (from 28 ± 5 GPa to 46 ± 8 GPa) inferring a toughness increment. Laboratory-fabricated ceramic models containing different inclusions (sand, glass-fibres, sponge spicules) show that mutually-oriented siliceous spicule inclusions prevent shrinkage and crack propagation leading to high stiffness clays (E = 836 ± 3 MPa). Pre-colonial amazonian potters were the first civilization known to employ biological materials to generate composite materials with enhanced fracture resistance and high stiffness in the history of mankind.

  14. Experimental Evaluation of Sodium Silicate-Based Nanosilica against Chloride Effects in Offshore Concrete

    Directory of Open Access Journals (Sweden)

    Kyoung-Min Kim

    2014-01-01

    Full Text Available This study investigates the effect of a new pore filling material, named sodium silicate-based nanosilica (SS, on resisting the diffusion of the chloride ions. The proposed SS is chosen, mainly due to its smaller particle size, compared to the conventional ethyl silicate-based nanosilica. Each particle of SS is chemically treated to have the negative (− charge on its surface. Four types of mixes with different amounts of partial replacement with fly ash and slag are prepared. Effect of water to binder ratios (0.35, 0.40, and 0.45 is also examined. Test results showed that the inclusion of SS was significantly beneficial for protecting the concrete from chloride attack. At a given strength, the SS inclusion in concrete was up to three times more effective than the control concrete without SS. It is believed that these excellent results are attributed to the small particle size and the chemical surface treatment of SS. In this study, experiments of compressive strength, hydration heat, accelerated neutralization, and sulfate erosion tests were also conducted to find the general effect of SS inclusion on the fundamental properties and durability of concrete.

  15. Footstep towards Inclusive Education

    Science.gov (United States)

    Abbas, Faiza; Zafar, Aneeka; Naz, Tayyaba

    2016-01-01

    Inclusive education is a rising trend in the world. The first step towards inclusive education is providing the awareness to the general education teachers. This study focused to investigate the general education teachers of primary and secondary level awareness about the special education and inclusive education. This study is descriptive method…

  16. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansens, Wiebren S.; Otten, Sabine; van der Zee, Karen; Jans, Lise

    2014-01-01

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  17. Inclusion: Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, W.S.|info:eu-repo/dai/nl/390929395; Otten, S.; Van der Zee, K.I.; Jans, L.

    2014-01-01

    n the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  18. Inclusion : Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, Wiebren S.; Otten, Sabine; van der Zee, Karen I.; Jans, Lise

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  19. Inclusion : Conceptualization and measurement

    NARCIS (Netherlands)

    Jansen, Wiebren S.; Otten, Sabine; van der Zee, Karen I.; Jans, Lise

    2014-01-01

    In the present research, we introduced a conceptual framework of inclusion and subsequently used this as a starting point to develop and validate a scale to measure perceptions of inclusion. Departing from existing work on inclusion and complementing this with theoretical insights from optimal

  20. Inclusion in Middle Tennessee

    Science.gov (United States)

    Hayes, Brandalyn; Ashley, Mandi; Salter, Derrick

    2013-01-01

    The overall purpose of this study was to provide school districts within Tennessee with more research about how weekly hours of inclusion impact student achievement. Specifically, researchers examined which models of inclusion were in use in two school districts in Tennessee, administrators' and teachers' perceptions of inclusion, and whether or…

  1. Transformation of Oxide Inclusions in Type 304 Stainless Steels during Heat Treatment

    Science.gov (United States)

    Ren, Ying; Zhang, Lifeng; Pistorius, P. Chris

    2017-10-01

    Heat treatment of Type 304 stainless steel in the range of 1273 K (1000 °C) to 1473 K (1200 °C) can transform manganese silicate inclusions to manganese chromite (spinel) inclusions. During heat treatment, Cr reacts with manganese silicate to form spinel. The transformation rate of inclusions depends strongly on both temperature [in the range of 1273 K to 1473 K (1000 °C to 1200 °C)] and inclusion size. A kinetic model, developed using FactSage macros, showed that these effects agree quantitatively with diffusion-controlled transformation. A simplified analytical model, which can be used for rapid calculations, predicts similar transformation kinetics, in agreement with the experimental observations.

  2. Lattice stability and high pressure melting mechanism of dense hydrogen up to 1.5 TPa

    CERN Document Server

    Geng, Hua Y; Wu, Q

    2016-01-01

    Lattice stability and metastability, as well as melting, are important features of the physics and chemistry of dense hydrogen. Using ab initio molecular dynamics (AIMD), the classical superheating limit and melting line of metallic hydrogen are investigated up to 1.5 TPa. The computations show that the classical superheating degree is about 100 K, and the classical melting curve becomes flat at a level of 350 K when beyond 500 GPa. This information allows us to estimate the well depth and the potential barriers that must be overcome when the crystal melts. Inclusion of nuclear quantum effects (NQE) using path integral molecular dynamics (PIMD) predicts that both superheating limit and melting temperature are lowered to below room temperature, but the latter never reach absolute zero. Detailed analysis indicates that the melting is thermally activated, rather than driven by pure zero-point motion (ZPM). This argument was further supported by extensive PIMD simulations, demonstrating the stability of Fddd stru...

  3. Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Wurth, R. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany); Pascual, M.J., E-mail: mpascual@icv.csic.es [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Mather, G.C.; Pablos-Martin, A.; Munoz, F.; Duran, A. [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex 9 (France); Ruessel, C. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)

    2012-06-15

    A base glass of composition 3.5 Li{sub 2}O Bullet-Operator 0.15 Na{sub 2}O Bullet-Operator 0.2 K{sub 2}O Bullet-Operator 1.15 MgO Bullet-Operator 0.8 BaO Bullet-Operator 1.5 ZnO Bullet-Operator 20 Al{sub 2}O{sub 3} Bullet-Operator 67.2 SiO{sub 2} Bullet-Operator 2.6 TiO{sub 2} Bullet-Operator 1.7 ZrO{sub 2} Bullet-Operator 1.2 As{sub 2}O{sub 3} (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi{sub 2}O{sub 6} with nanoscaled crystals forms at 750 Degree-Sign C. Quantitative Rietveld refinement of samples annealed at 750 Degree-Sign C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, {beta}-eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. The Avrami parameter (n {approx} 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 {+-} 20 kJ mol{sup -1}. - Highlights: Black-Right-Pointing-Pointer Nanoscaled high-quartz crystals from a multicomponent lithium alumino-silicate glass. Black-Right-Pointing-Pointer Combined X-ray and neutron diffraction structural refinement. Black-Right-Pointing-Pointer {beta}-Eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. Black-Right-Pointing-Pointer 3-Dimensional bulk crystallisation mechanism with an increasing number of nuclei. Black-Right-Pointing-Pointer Usage and validation of an alternative approach to calculate the Avrami parameter.

  4. Silicate release from glass for pharmaceutical preparations.

    Science.gov (United States)

    Bohrer, Denise; Bortoluzzi, Fabiana; Nascimento, Paulo Cícero; Carvalho, Leandro Machado; Ramirez, Adrian Gustavo

    2008-05-01

    Glass is made of polymeric silica and other minor components, which are necessary for turning the silica into a material more easily moldable and resistant to temperature changes. Glass containers for pharmaceutical usage are classified according to their resistance to a chemical attack, a test carried out in the presence of water and heat. The test is designed to show the released alkalinity, a variable dependent on the amount of sodium oxide, one of the minor components added to the glass mass. In this work, the release of silica from glass by action of constituents from pharmaceutical formulations was investigated. The study included products used in large volumes and usually stored in glass containers. Solutions of amino acids, electrolytes, glucose, oligoelements and others such as heparin and sodium bicarbonate were individually stored in glass containers and heated at 121 degrees C for 30min, as in the water attack test. The test was also carried out only with water, where the pH varied from 2 to 12. The released silicate was measured either by photometry or atomic absorption spectrometry, depending on the nature of the sample. The results showed that silicate is released during the heating cycle even if the contact is with pure water only. The pH exerts a considerable influence on the release, being that the higher the pH, the higher the silica dissolved. An elevated pH, however, is not the only factor responsible for silica dissolution. While in the solutions of NaCl, KCl, Mg Cl2 and ZnSO4 and in most of the amino acids, the concentration of silicate was as high as in pure water (0.1-1.0mg Si/L). In the solutions of sodium acetate, bicarbonate and gluconate, its concentration was much higher, over 30mg Si/L. These results were confirmed by the analysis of commercial products, where in solutions of amino acids the level of silicate ranged from 0.14 to 0.19mg Si/L. On the other hand, calcium gluconate, sodium bicarbonate and potassium phosphate presented

  5. Redox dependent behaviour of molybdenum during magmatic processes in the terrestrial and lunar mantle: Implications for the Mo/W of the bulk silicate Moon

    Science.gov (United States)

    Leitzke, F. P.; Fonseca, R. O. C.; Sprung, P.; Mallmann, G.; Lagos, M.; Michely, L. T.; Münker, C.

    2017-09-01

    We present results of high-temperature olivine-melt, pyroxene-melt and plagioclase-melt partitioning experiments aimed at investigating the redox transition of Mo in silicate systems. Data for a series of other minor and trace elements (Sc, Ba, Sr, Cr, REE, Y, HFSE, U, Th and W) were also acquired to constrain the incorporation of Mo in silicate minerals. All experiments were carried out in vertical tube furnaces at 1 bar and temperatures ranging from ca. 1220 to 1300 °C. Oxygen fugacity was controlled via CO-CO2 gas mixtures and varied systematically from 5.5 log units below to 1.9 log units above the fayalite-magnetite-quartz (FMQ) redox buffer thereby covering the range in oxygen fugacities of terrestrial and lunar basalt genesis. Molybdenum is shown to be volatile at oxygen fugacities above FMQ and that its compatibility in pyroxene and olivine increases three orders of magnitude towards the more reducing conditions covered in this study. The partitioning results show that Mo is dominantly tetravalent at redox conditions below FMQ-4 and dominantly hexavalent at redox conditions above FMQ. Given the differences in oxidation states of the terrestrial (oxidized) and lunar (reduced) mantles, molybdenum will behave significantly differently during basalt genesis in the Earth (i.e. highly incompatible; average DMoperidotite/melt ∼ 0.008) and Moon (i.e. moderately incompatible/compatible; average DMoperidotite/melt ∼ 0.6). Thus, it is expected that Mo will strongly fractionate from W during partial melting in the lunar mantle, given that W is broadly incompatible at FMQ-5. Moreover, the depletion of Mo and the Mo/W range in lunar samples can be reproduced by simply assuming a primitive Earth-like Mo/W for the bulk silicate Moon. Such a lunar composition is in striking agreement with the Moon being derived from the primitive terrestrial mantle after core formation on Earth.

  6. Gas-driven filter pressing: insights into melt segregation from crystal mushes

    Science.gov (United States)

    Pistone, Mattia; Arzilli, Fabio; Cordonnier, Benoit; Dobson, Katherine; Reusser, Eric; Ulmer, Peter; Marone, Federica; Whittington, Alan; Mancini, Lucia; Fife, Julie; Blundy, Jonathan

    2015-04-01

    Gas-driven filter pressing relieves the gas pressure developed through second boiling by expelling melt from a crystal mush. It is thought to play a major role in magma fractionation at shallow depths (filter pressing can occur. We performed in-situ high-temperature high-speed synchrotron X-ray tomography (500-800 °C, 3 μm/pixel, 8 seconds per full 3D dataset) to collect real time information on the behaviour of hydrous haplogranitic (2.1 wt.% H2O) and dacitic (4.2 wt.% H2O) crystal mushes with a wide range of crystal contents (34-80 vol.%). The data constrain how the crystal content affects the efficiency of gas-driven filter pressing of silicic melt out of the crystal mush framework, and show that gas-driven filter pressing operates below the maximum packing fraction of the suspended phases (bubbles + crystals) of ~74 vol.%. Above this value, the crystal mush is fated to fracture. These results provide essential constrain on the physical conditions under which gas-driven filter pressing can efficiently operate and force silicic melt out of the crystal framework. This also implies that, for effective gas-driven filter pressing, the crystal mush must inflate slowly relative to build-up of pressure and expulsion of melt. These observations suggest a possible explanation for the production of eruptible crystal-poor rhyolites in the Earth's crust.

  7. Fractional ultrabasic-basic evolution of upper-mantle magmatism: Evidence from xenoliths in kimberlites, inclusions in diamonds and experiments

    Science.gov (United States)

    Litvin, Yuriy; Kuzyura, Anastasia

    2017-04-01

    ultrabasic-basic magmatic evolution and petrogenesis may be controlled by the following melting relations: from Ol, Opx, L field to cotectic curve Ol, Opx, Cpx, L, peritectic point Ol, Opx, Cpx, Grt, L (loss of Opx), cotectic curve Ol, (Cpx+Jd), Grt, L, peritectic point Ol, (Cpx→Omph), Grt, L (loss of Ol), divariant field Omph,Grt,L, cotectic curve Ky, Omph, Grt, L, eutectic point Ky,Coe,Omph, Grt,L, subsolidus assemblage Ky,Coe,Omph, Grt. The fractional ultrabasic-basic evolution of the upper-mantle silicate-carbonate-carbon melts-solutions, which are responsible for genesis of diamond-and-inclusions associations and diamond-bearing peridotites and eclogites, follows the similar physico-chemical mechanisms (Litvin et al., 2016). This is illustrated by fractional syngenesis diagram for diamonds and associated minerals which construction is based on evidence from high pressure experiments. References Gasparik T., Litvin Yu.A (1997). Stability of Na2Mg2Si2O7 and melting relations on the forsterite - jadeite join at pressures up to 22 GPa. Eur, J. Mineral. 9(2), 311-326. Litvin Yu.A. (1991). Physico-Chemical Study of Melting of Materials from the Deep Earth. Moscow: Nauka. 312 p. Litvin Yu.A., Spivak A.V., Kuzyura A.V. (2016). Fundamentals of the mantle-carbonatite concept of diamond genesis, Geochemistry Internat. 34(10), 839-857.

  8. UNCONSTRAINED MELTING AND SOLIDIFICATION INSIDE ...

    African Journals Online (AJOL)

    2015-09-01

    Sep 1, 2015 ... capsule), cylinder (shell and tube heat exchanger) and rectangular enclosure. Khodadadi and. Zhang [21] studied the effect of buoyancy-driven convection on constrained melting of PCM in a spherical container numerically. They showed the rate of melting at the top region of sphere is faster than at the ...

  9. Silicate Based Glass Formulations for Immobilization of U.S. Defense Wastes Using Cold Crucible Induction Melters

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Gary L.; Kim, Dong-Sang; Schweiger, Michael J.; Marra, James C.; Lang, Jesse B.; Crum, Jarrod V.; Crawford, Charles L.; Vienna, John D.

    2014-05-22

    The cold crucible induction melter (CCIM) is an alternative technology to the currently deployed liquid-fed, ceramic-lined, Joule-heated melter for immobilizing of U.S. tank waste generated from defense related reprocessing. In order to accurately evaluate the potential benefits of deploying a CCIM, glasses must be developed specifically for that melting technology. Related glass formulation efforts have been conducted since the 1990s including a recent study that is first documented in this report. The purpose of this report is to summarize the silicate base glass formulation efforts for CCIM testing of U.S. tank wastes. Summaries of phosphate based glass formulation and phosphate and silicate based CCIM demonstration tests are reported separately (Day and Ray 2013 and Marra 2013, respectively). Combined these three reports summarize the current state of knowledge related to waste form development and process testing of CCIM technology for U.S. tank wastes.

  10. Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

    Science.gov (United States)

    Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

    2015-12-01

    Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

  11. Estimating shock pressures based on high-pressure minerals in shock-induced melt veins of L chondrites

    Science.gov (United States)

    Xie, Zhidong; Sharp, Thomas G.; de Carli, Paul S.

    Here we report the transmission electron microscopy (TEM) observations of the mineral assemblages and textures in shock-induced melt veins from seven L chondrites of shock stages ranging from S3 to S6. The mineral assemblages combined with phase equilibrium data are used to constrain the crystallization pressures, which can be used to constrain shock pressure in some cases. Thick melt veins in the Tenham L6 chondrite contain majorite and magnesiowüstite in the center, and ringwoodite, akimotoite, vitrified silicate-perovskite, and majorite in the edge of the vein, indicating crystallization pressure of ˜25 GPa. However, very thin melt veins (5-30 μm wide) in Tenham contain glass, olivine, clinopyroxene, and ringwoodite, suggesting crystallization during transient low-pressure excursions as the shock pressure equilibrated to a continuum level. Melt veins of Umbarger include ringwoodite, akimotoite, and clinopyroxene in the vein matrix, and Fe2SiO4-spinel and stishovite in SiO2-FeO-rich melt, indicating a crystallization pressure of ˜18 GPa. The silicate melt veins in Roy contain majorite plus ringwoodite, indicating pressure of ˜20 GPa. Melt veins of Ramsdorf and Nakhon Pathon contain olivine and clinoenstatite, indicating pressure of less than 15 GPa. Melt veins of Kunashak and La Lande include albite and olivine, indicating crystallization at less than 2.5 GPa. Based upon the assemblages observed, crystallization of shock veins can occur before, during, or after pressure release. When the assemblage consists of high-pressure minerals and that assemblage is constant across a larger melt vein or pocket, the crystallization pressure represents the equilibrium shock pressure.

  12. Foresighting for Inclusive Development

    DEFF Research Database (Denmark)

    Andersen, Allan Dahl; Andersen, Per Dannemand

    2017-01-01

    We propose that foresight can contribute to inclusive development by making innovation systems more inclusive. Processes of developing future oriented innovation policies are often unsuccessful and rarely inclusive. We conceptualize such processes as foresighting. We focus on how the ex-ante design...... of policymaking processes affects the actual process with a focus on inclusion, and we discuss how it affects policy effectiveness and innovation system transformation. Our argument is that processes of policymaking must be inclusive to affect and transform innovation systems because a set of distributed actors......, rather than ministries and innovation agencies, is the gatekeepers of change. From this perspective, inclusion is a precondition rather than an obstacle for transformation. Based on the notion of innovation system foresight, we develop an analytical framework that we use to study design and processes...

  13. Inclusive research: new challenges

    OpenAIRE

    Nind, Melanie

    2015-01-01

    This presentation will engage participants in a critical examination of inclusive research. First, I will define inclusive research and identify the social contextual elements that have shaped it as an overarching concept in the move towards the democratisation of research. Next, I will explore quality and ethics in inclusive research, building on research conducted in the field of learning disability and using examples from a range of applied social research contexts. Finally I will invite u...

  14. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2004-12-01

    Full Text Available The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca2+ ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of calcium ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca2+ ions on silicate level in the fluid and the fluid properties.

  15. Determination of chlorine in silicate rocks

    Science.gov (United States)

    Peck, L.C.

    1959-01-01

    In a rapid accurate method for the determination of chlorine in silicate rocks, the rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate. The sinter cake is leached with water, the resulting solution is filtered, and the filtrate is acidified with nitric acid. Chlorine is determined by titrating this solution with mercuric nitrate solution using sodium nitroprusside as the indicator. The titration is made in the dark with a beam of light shining through the solution. The end point of the titration is found by visually comparing the intensity of this beam of light with that of a similar beam of light in a reference solution.

  16. Microbial dissolution of silicate materials. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Schwartzman, D. [Howard Univ., Washington, DC (United States). Dept. of Biology

    1996-03-26

    The objective of this research was to better understand the role of selected thermophilic bacteria in the colonization and dissolution of silicate minerals, with potential applications to the HDR Project. The demonstration of enhanced dissolution from microbial effects is critically dependent on providing a mineral bait within a media deficient in the critical nutrient found in the mineral (e.g., Fe). Reproducible experimental conditions in batch experiments require agitation to expose mineral powders, as well as nearly similar initial conditions for both inoculated cultures and controls. It is difficult, but not impossible to ensure reproducible conditions with microbes favoring filamentous growth habits.

  17. Confronting New Demands : Inclusive Growth, Inclusive Trade ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    The research agenda will cover four themes: linkages between trade and inclusive growth; negotiation issues with poorly understood implications, such as labour standards and intellectual property; liberalization of trade in services, and the emerging regional trade policy architecture. The idea is to promote a better ...

  18. Monazite and xenotime solubility in granitic melts and the origin of the lanthanide tetrad effect

    Science.gov (United States)

    Duc-Tin, Quach; Keppler, Hans

    2015-01-01

    monazite and xenotime fractionation. The solubility of monazite and xenotime in silicate melt probably shows the tetrad effect, because of the very unusual coordination of the rare earth elements in these phosphate minerals, which is different from the coordination of the melt and therefore causes different crystal field interactions with the partially filled f orbitals of the rare earths. The tetrad effect in granites cannot be used as an indicator of fluid/rock or fluid/melt interaction, since it can be experimentally reproduced in the absence of any fluids.

  19. Lithospheric magma dynamics beneath the El Hierro Volcano, Canary Islands: insights from fluid inclusions

    Science.gov (United States)

    Oglialoro, E.; Frezzotti, M. L.; Ferrando, S.; Tiraboschi, C.; Principe, C.; Groppelli, G.; Villa, I. M.

    2017-10-01

    At active volcanoes, petrological studies have been proven to be a reliable approach in defining the depth conditions of magma transport and storage in both the mantle and the crust. Based on fluid inclusion and mineral geothermobarometry in mantle xenoliths, we propose a model for the magma plumbing system of the Island of El Hierro (Canary Islands). The peridotites studied here were entrained in a lava flow exposed in the El Yulan Valley. These lavas are part of the rift volcanism that occurred on El Hierro at approximately 40-30 ka. The peridotites are spinel lherzolites, harzburgites, and dunites which equilibrated in the shallow mantle at pressures between 1.5 and 2 GPa and at temperatures between 800 and 950 °C (low-temperature peridotites; LT), as well as at higher equilibration temperatures of 900 to 1100 °C (high-temperature peridotites; HT). Microthermometry and Raman analyses of fluid inclusions reveal trapping of two distinct fluid phases: early type I metasomatic CO2-N2 fluids ( X N2 = 0.01-0.18; fluid density (d) = 1.19 g/cm3), coexisting with silicate-carbonate melts in LT peridotites, and late type II pure CO2 fluids in both LT (d = 1.11-1.00 and 0.75-0.65 g/cm3) and HT ( d = 1.04-1.11 and 0.75-0.65 g/cm3) peridotites. While type I fluids represent metasomatic phases in the deep oceanic lithosphere (at depths of 60-65 km) before the onset of magmatic activity, type II CO2 fluids testify to two fluid trapping episodes during the ascent of xenoliths in their host mafic magmas. Identification of magma accumulation zones through interpretation of type II CO2 fluid inclusions and mineral geothermobarometry indicate the presence of a vertically stacked system of interconnected small magma reservoirs in the shallow lithospheric mantle between a depth of 22 and 36 km (or 0.67 to 1 GPa). This magma accumulation region fed a short-lived magma storage region located in the lower oceanic crust at a depth of 10-12 km (or 0.26-0.34 GPa). Following our model

  20. Thermodynamics of freezing and melting

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Costigliola, Lorenzo; Bailey, Nicholas

    2016-01-01

    Although the freezing of liquids and melting of crystals are fundamental for many areas of the sciences, even simple properties like the temperature–pressure relation along the melting line cannot be predicted today. Here we present a theory in which properties of the coexisting crystal and liquid...... phases at a single thermodynamic state point provide the basis for calculating the pressure, density and entropy of fusion as functions of temperature along the melting line, as well as the variation along this line of the reduced crystalline vibrational mean-square displacement (the Lindemann ratio...

  1. Asteroid Differentiation: Melting and Large-Scale Structure

    Science.gov (United States)

    Scheinberg, A.; Fu, R. R.; Elkins-Tanton, L. T.; Weiss, B. P.

    The diversity of mineralogies and textures in the asteroidal meteorite collection promises a similarly diverse array of parent bodies and relatives as we continue exploring the asteroid belt. The presence of metamorphosed and igneous meteorites demonstrates that even some small bodies were heated significantly, permitting a variety of complexly interacting processes and heterogeneities within an individual planetesimal. In particular, chondritic meteorites could even originate from the same parent body as some highly differentiated meteorites. The histories and present-day features of the asteroids depend on their initial composition and the timing and duration of the accretion process. We first discuss the energy sources driving thermal modification of planetesimals and summarize the processes involved in differentiation as hydrous, metal, and silicate melting occurs. Then we outline the aftermath of differentiation as the body cools, and close with a discussion of magnetic, geophysical, and meteoritic evidence for differentiation in planetesimals.

  2. Scope of Silicic Magmatism Associated With the Snake River Plain-Yellowstone (SRPY) "Hotspot" Track

    Science.gov (United States)

    Leeman, W. P.

    2007-12-01

    Eruptive volumes of silicic volcanic rocks provide indirect albeit minimal indications of the scale of magmatism associated with the SRPY hotspot track. Coherent eruptive centers at Yellowstone produced ca. 6000 km3 of high silica rhyolite over &~2 m.y. whereas the Bruneau-Jarbidge center in the central SRP produced as much as 10,000 km3 between 12.7 and 8 Ma. Total magma volumes could be significantly larger. About half erupted as 'supervolcano class` ignimbrites (i.e., exceeding 103 km3). Implicitly, such volumes must be on-tap at least periodically during the lifetime of an eruptive center but heterogeneities in mineral populations imply that magma may be derived from a plexus of isolated pockets in the crust (`crustal sponge`) rather than a well-mixed chamber. Magmatism was strongly bimodal - 'A-type' high silica rhyolite and basalt - intermediate composition lavas are rare. Moreover, each center produced rhyolite for 2-3 m.y. prior to the onset of basaltic volcanism which dominated subsequent activity. Nearly all SRPY rhyolites carry anhydrous mineral assemblages and mineral thermometry indicates high magmatic temperatures (typically >850-900°C). Radiogenic isotopes (Sr-Nd-Pb), trace element patterns, and low 18O in many SRPY rhyolites implicate a crustal source, although Nd isotopic data preclude large contributions from Archean crust. Silicic volcanism initiated in N-central Nevada ca. 16 Ma and migrated to Yellowstone by 2 Ma. However, the pattern of silicic eruptions was not simply progressive in space and time. Between 11.5-10 Ma major silicic eruptions occurred over a swath of more than 400 km - signifying availability of diverse rhyolite magmas beneath much of the SRP. Assuming that crustal melting was driven by basaltic intrusions, such magmas must have been generated beneath much of the province prior to 10 Ma - in part, well in advance of the postulated position of the Yellowstone hotspot at that time. The quantity of basalt needed to power SRPY

  3. Thermochemistry of dense hydrous magnesium silicates

    Science.gov (United States)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  4. What is "Inclusion"?

    Science.gov (United States)

    Neary, Tom; Halvorsen, Ann

    This paper presents principles for inclusion of students with disabilities in regular education classrooms, organized around the following aspects: inclusion versus mainstreaming, service delivery, planning and curriculum development, best practices, and training. Among the principles discussed are: students are members of age-appropriate general…

  5. Assessment of inclusive education

    DEFF Research Database (Denmark)

    Miller, Tanja

    2014-01-01

    the quality of the learning environment in regard to inclusion – this model draws heavily on the logic and mindset of ECERS (Early child environment program). This article will relate the rationale of the assessment model called “Dialoger om Kvalitet” (dialogues on quality) to LSP’s definition of inclusion...

  6. Financial Inclusion in Malaysia

    OpenAIRE

    World Bank Group

    2017-01-01

    Malaysia has achieved one of the highest levels of financial inclusion among Southeast Asia countries, due in part to policies taking advantage of mobile phones and banking agents to expand access. The report looks at specific actions, programs, and strategies that have contributed to enhance financial inclusion in the country and highlights key learnings to benefit low- and middle-income ...

  7. Understanding Inclusion in Cyprus

    Science.gov (United States)

    Mamas, Christoforos

    2013-01-01

    This paper provides a framework for understanding inclusion in Cyprus. The evidence base is the result of a six-month qualitative research study in five Cypriot mainstream primary schools. Despite the rhetoric in favour of inclusion, it seems that the Cypriot educational system is still highly segregating in its philosophy and does not fully…

  8. Size of Non-Metallic Inclusions in High-Grade Medium Carbon Steel

    Directory of Open Access Journals (Sweden)

    Lipiński T.

    2014-12-01

    Full Text Available Non-metallic inclusions found in steel can affect its performance characteristics. Their impact depends not only on their quality, but also, among others, on their size and distribution in the steel volume. The literature mainly describes the results of tests on hard steels, particularly bearing steels. The amount of non-metallic inclusions found in steel with a medium carbon content melted under industrial conditions is rarely presented in the literature. The tested steel was melted in an electric arc furnace and then desulfurized and argonrefined. Seven typical industrial melts were analyzed, in which ca. 75% secondary raw materials were used. The amount of non-metallic inclusions was determined by optical and extraction methods. The test results are presented using stereometric indices. Inclusions are characterized by measuring ranges. The chemical composition of steel and contents of inclusions in every melts are presented. The results are shown in graphical form. The presented analysis of the tests results on the amount and size of non-metallic inclusions can be used to assess them operational strength and durability of steel melted and refined in the desulfurization and argon refining processes.

  9. Carbon Mineralization Using Phosphate and Silicate Ions

    Science.gov (United States)

    Gokturk, H.

    2013-12-01

    Carbon dioxide (CO2) reduction from combustion of fossil fuels has become an urgent concern for the society due to marked increase in weather related natural disasters and other negative consequences of global warming. CO2 is a highly stable molecule which does not readily interact with other neutral molecules. However it is more responsive to ions due to charge versus quadrupole interaction [1-2]. Ions can be created by dissolving a salt in water and then aerosolizing the solution. This approach gives CO2 molecules a chance to interact with the hydrated salt ions over the large surface area of the aerosol. Ion containing aerosols exist in nature, an example being sea spray particles generated by breaking waves. Such particles contain singly and doubly charged salt ions including Na+, Cl-, Mg++ and SO4--. Depending on the proximity of CO2 to the ion, interaction energy can be significantly higher than the thermal energy of the aerosol. For example, an interaction energy of 0.6 eV is obtained with the sulfate (SO4--) ion when CO2 is the nearest neighbor [2]. In this research interaction between CO2 and ions which carry higher charges are investigated. The molecules selected for the study are triply charged phosphate (PO4---) ions and quadruply charged silicate (SiO4----) ions. Examples of salts which contain such molecules are potassium phosphate (K3PO4) and sodium orthosilicate (Na4SiO4). The research has been carried out with first principle quantum mechanical calculations using the Density Functional Theory method with B3LYP functional and Pople type basis sets augmented with polarization and diffuse functions. Atomic models consist of the selected ions surrounded by water and CO2 molecules. Similar to the results obtained with singly and doubly charged ions [1-2], phosphate and silicate ions attract CO2 molecules. Energy of interaction between the ion and CO2 is 1.6 eV for the phosphate ion and 3.3 eV for the silicate ion. Hence one can expect that the selected

  10. METAL MELTS – NANOSTRUCTURED SYSTEMS

    Directory of Open Access Journals (Sweden)

    V. Yu. Stetsenko

    2014-01-01

    Full Text Available On the basis of thermodynamic analysis it is shown that metal melts are the nanostructured systems which consist of phases and atoms nanocrystals. Nanocrystalsmake 97% ofthemeltvolume.

  11. Analysis of H2O in silicate glass using attenuated total reflectance (ATR) micro-FTIR spectroscopy

    Science.gov (United States)

    Lowenstern, Jacob B.; Pitcher, Bradley W.

    2013-01-01

    We present a calibration for attenuated total reflectance (ATR) micro-FTIR for analysis of H2O in hydrous glass. A Ge ATR accessory was used to measure evanescent wave absorption by H2O within hydrous rhyolite and other standards. Absorbance at 3450 cm−1 (representing total H2O or H2Ot) and 1630 cm−1 (molecular H2O or H2Om) showed high correlation with measured H2O in the glasses as determined by transmission FTIR spectroscopy and manometry. For rhyolite, wt%H2O=245(±9)×A3450-0.22(±0.03) and wt%H2Om=235(±11)×A1630-0.20(±0.03) where A3450 and A1630 represent the ATR absorption at the relevant infrared wavelengths. The calibration permits determination of volatiles in singly polished glass samples with spot size down to ~5 μm (for H2O-rich samples) and detection limits of ~0.1 wt% H2O. Basaltic, basaltic andesite and dacitic glasses of known H2O concentrations fall along a density-adjusted calibration, indicating that ATR is relatively insensitive to glass composition, at least for calc-alkaline glasses. The following equation allows quantification of H2O in silicate glasses that range in composition from basalt to rhyolite: wt%H2O=(ω×A3450/ρ)+b where ω = 550 ± 21, b = −0.19 ± 0.03, ρ = density, in g/cm3, and A3450 is the ATR absorbance at 3450 cm−1. The ATR micro-FTIR technique is less sensitive than transmission FTIR, but requires only a singly polished sample for quantitative results, thus minimizing time for sample preparation. Compared with specular reflectance, it is more sensitive and better suited for imaging of H2O variations in heterogeneous samples such as melt inclusions. One drawback is that the technique can damage fragile samples and we therefore recommend mounting of unknowns in epoxy prior to polishing. Our calibration should hold for any Ge ATR crystals with the same incident angle (31°). Use of a different crystal type or geometry would require measurement of several H2O-bearing standards to provide a crystal

  12. A model of sulphur solubility for hydrous mafic melts: application to the determination of magmatic fluid compositions of Italian volcanoes

    OpenAIRE

    Pichavant, M.; Scaillet, B.

    2005-01-01

    We present an empirical model of sulphur solubility that allows us to calculate f S2 if P, T, fO2 and the melt composition, including H2O and S, are known. The model is calibrated against three main experimental data bases consisting in both dry and hydrous silicate melts. Its prime goal is to calculate the f S2 of hydrous basalts that currently lack experimental constraints of their sulphur solubility behaviour. Application of the model to Stromboli, Vesuvius, Vulcano and...

  13. Scaleable Clean Aluminum Melting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Han, Q.; Das, S.K. (Secat, Inc.)

    2008-02-15

    The project entitled 'Scaleable Clean Aluminum Melting Systems' was a Cooperative Research and Development Agreements (CRADAs) between Oak Ridge National Laboratory (ORNL) and Secat Inc. The three-year project was initially funded for the first year and was then canceled due to funding cuts at the DOE headquarters. The limited funds allowed the research team to visit industrial sites and investigate the status of using immersion heaters for aluminum melting applications. Primary concepts were proposed on the design of furnaces using immersion heaters for melting. The proposed project can continue if the funding agency resumes the funds to this research. The objective of this project was to develop and demonstrate integrated, retrofitable technologies for clean melting systems for aluminum in both the Metal Casting and integrated aluminum processing industries. The scope focused on immersion heating coupled with metal circulation systems that provide significant opportunity for energy savings as well as reduction of melt loss in the form of dross. The project aimed at the development and integration of technologies that would enable significant reduction in the energy consumption and environmental impacts of melting aluminum through substitution of immersion heating for the conventional radiant burner methods used in reverberatory furnaces. Specifically, the program would couple heater improvements with furnace modeling that would enable cost-effective retrofits to a range of existing furnace sizes, reducing the economic barrier to application.

  14. Ladle Metallurgy Kinetics: Inclusion-Inclusion Reactions

    Science.gov (United States)

    Pistorius, P. Chris

    An example is presented to illustrate the joint effect of local reaction equilibria and mass transfer limitations, for reactions during ladle refining of steel. The example relies on some of the kinetic principles that David Robertson has employed to quantify many metallurgical processes. In calcium treatment of alumina inclusions in aluminum-killed steels, solid CaS forms as an intermediate reaction product. During subsequent reaction, CaS disappears and calcium aluminate forms; at the same time, aluminum and sulfur dissolve in the steel. Kinetic analysis shows that the rate of this reaction is not limited by mass transfer of dissolved aluminum and sulfur away from the reacting inclusions. The reaction rate is likely limited by transport of dissolved calcium. This example also illustrates the use of FactSage macros for kinetic modeling.

  15. Petrology and Geochemistry of Calc-Silicate Schists and Calc ...

    African Journals Online (AJOL)

    Chemically the calc-silicate schists are characterized by relatively high CaO, MgO, Cr, Ni, Sr, La, Ce and Nd contents compared with the mica schist regionally associated with the marble as well as the Post-Archean Australian Shale (PAAS). Relative to the ultramafic schist the calc-silicate schists are characterized by higher ...

  16. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer (generic). 721.9513 Section 721.9513 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical...

  17. [Adsorption characteristic and form distribution of silicate in lakes sediments].

    Science.gov (United States)

    Lü, Chang-Wei; Cui, Meng; Gao, Ji-Mei; Zhang, Xi-Yan; Wan, Li-Li; He, Jiang; Meng, Ting-Ting; Bai, Fan; Yang, Xu

    2012-01-01

    Taking surface sediments from the Wuliangsuhai Lake and Daihai Lake as adsorbent, the isothermal adsorption experiments of silicate on sediments were carried out and the adsorption behavior was explained by Langmuir, Freundlich and Temkin crossover-type equations, then the form distribution characters of silicate were studied after adsorption in this work. The results showed that the adsorption behavior of silicate on the two lakes sediments can be linear fitting in the lower concentration dose (Temkin crossover-type equations can be used to explain the adsorption behavior of silicate on the two lakes sediments, and the native adsorption silicate (NAS) and equilibrium silicate concentration (ESC(0)) calculated by the three equations could be used to explain the sink and source effects of the sediments from the two lakes; the silicate form distribution in the sediments after adsorption indicated that silicate adsorbed on particles were mainly added on the form of IEF-Si, CF-Si, IMOF-Si and OSF-Si, and the IMOF-Si and OSF-Si had important potential bioavailability.

  18. Fire Resistance of Wood Impregnated with Soluble Alkaline Silicates

    OpenAIRE

    Andrea Marisa Pereyra; Carlos Alberto Giudice

    2007-01-01

    The aim of this paper is to determine the fire performance of wood panels (Araucaria angustifolia) impregnated with soluble alkaline silicates. Commercial silicates based on sodium and potassium with 2.5/1.0 and 3.0/1.0 silica/alkali molar ratios were selected; solutions and glasses ...

  19. Melting phase relations in the systems Mg2SiO4-H2O and MgSiO3-H2O and the formation of hydrous melts in the upper mantle

    Science.gov (United States)

    Novella, Davide; Dolejš, David; Myhill, Robert; Pamato, Martha G.; Manthilake, Geeth; Frost, Daniel J.

    2017-05-01

    High-pressure and high-temperature melting experiments were conducted in the systems Mg2SiO4-H2O and MgSiO3-H2O at 6 and 13 GPa and between 1150 and 1900 °C in order to investigate the effect of H2O on melting relations of forsterite and enstatite. The liquidus curves in both binary systems were constrained and the experimental results were interpreted using a thermodynamic model based on the homogeneous melt speciation equilibrium, H2O + O2- = 2OH-, where water in the melt is present as both molecular H2O and OH- groups bonded to silicate polyhedra. The liquidus depression as a function of melt H2O concentration is predicted using a cryoscopic equation with the experimental data being reproduced by adjusting the water speciation equilibrium constant. Application of this model reveals that in hydrous MgSiO3 melts at 6 and 13 GPa and in hydrous Mg2SiO4 melts at 6 GPa, water mainly dissociates into OH- groups in the melt structure. A temperature dependent equilibrium constant is necessary to reproduce the data, however, implying that molecular H2O becomes more important in the melt with decreasing temperature. The data for hydrous forsterite melting at 13 GPa are inconclusive due to uncertainties in the anhydrous melting temperature at these conditions. When applied to results on natural peridotite melt systems at similar conditions, the same model infers the presence mainly of molecular H2O, implying a significant difference in physicochemical behaviour between simple and complex hydrous melt systems. As pressures increase along a typical adiabat towards the base of the upper mantle, both simple and complex melting results imply that a hydrous melt fraction would decrease, given a fixed mantle H2O content. Consequently, the effect of pressure on the depression of melting due to H2O could not cause an increase in the proportion, and hence seismic visibility, of melts towards the base of the upper mantle.

  20. Natural Weathering Rates of Silicate Minerals

    Science.gov (United States)

    White, A. F.

    2003-12-01

    Silicates constitute more than 90% of the rocks exposed at Earth's land surface (Garrels and Mackenzie, 1971). Most primary minerals comprising these rocks are thermodynamically unstable at surface pressure/temperature conditions and are therefore susceptible to chemical weathering. Such weathering has long been of interest in the natural sciences. Hartt (1853) correctly attributed chemical weathering to "the efficacy of water containing carbonic acid in promoting the decomposition of igneous rocks." Antecedent to the recent interest in the role of vegetation on chemical weathering, Belt (1874) observed that the most intense weathering of rocks in tropical Nicaragua was confined to forested regions. He attributed this effect to "the percolation through rocks of rain water charged with a little acid from decomposing vegetation." Chamberlin (1899) proposed that the enhanced rates of chemical weathering associated with major mountain building episodes in Earth's history resulted in a drawdown of atmospheric CO2 that led to periods of global cooling. Many of the major characteristics of chemical weathering had been described when Merrill (1906) published the groundbreaking volume Rocks, Rock Weathering, and Soils.The major advances since that time, particularly during the last several decades, have centered on understanding the fundamental chemical, hydrologic, and biologic processes that control weathering and in establishing quantitative weathering rates. This research has been driven by the importance of chemical weathering to a number environmentally and economically important issues. Undoubtedly, the most significant aspect of chemical weathering is the breakdown of rocks to form soils, a process that makes life possible on the surface of the Earth. The availability of many soil macronutrients such as magnesium, calcium, potassium, and PO4 is directly related to the rate at which primary minerals weather. Often such nutrient balances are upset by anthropogenic

  1. Deformability of Oxide Inclusions in Tire Cord Steels

    Science.gov (United States)

    Zhang, Lifeng; Guo, Changbo; Yang, Wen; Ren, Ying; Ling, Haitao

    2017-12-01

    The deformation of oxide inclusions in tire cord steels during hot rolling was analyzed, and the factors influencing their deformability at high and low temperatures were evaluated and discussed. The aspect ratio of oxide inclusions decreased with the increasing reduction ratio of the steel during hot rolling owing to the fracture of the inclusions. The aspect ratio obtained after the first hot-rolling process was used to characterize the high-temperature deformability of the inclusions. The deformation first increased and then decreased with the increasing (MgO + Al2O3)/(SiO2 + MnO) ratio of the inclusions. It also increased with the decreasing melting temperatures of the inclusions. Young's modulus was used to evaluate the low-temperature deformability of the inclusions. An empirical formula was fitted to calculate the Young's moduli of the oxides using the mean atomic volume. The moduli values of the inclusions causing wire fracture were significantly greater than the average. To reduce fracture in tire cord steel wires during cold drawing, it is proposed that inclusions be controlled to those with high SiO2 content and extremely low Al2O3 content. This proposal is based on the hypothesis that the deformabilities of oxides during cold drawing are inversely proportional to their Young's moduli. The future study thus proposed includes an experimental confirmation for the abovementioned predictions.

  2. ESR and spectral studies of Er{sup 3+} ions in soda-lime silicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Kaewwiset, W., E-mail: opticslaser@yahoo.com [Department of Physics, Faculty of Science, King Mongkut' s University of Technology, Thonburi, Bangkok 10140 (Thailand); Thamaphat, K. [Department of Physics, Faculty of Science, King Mongkut' s University of Technology, Thonburi, Bangkok 10140 (Thailand); Kaewkhao, J. [Center of Excellence in Glass Technology and Materials Science (CEGM), Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom 73000 (Thailand); Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400 (Thailand); Limsuwan, P. [Department of Physics, Faculty of Science, King Mongkut' s University of Technology, Thonburi, Bangkok 10140 (Thailand); Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400 (Thailand)

    2013-01-15

    Electron spin resonance (ESR), optical absorption spectra and photoluminescence spectra of Er{sup 3+} ions in soda-lime silicate glasses doped with different concentrations of Er{sub 2}O{sub 3} have been studied. The glasses of the composition (in mol%) (65-x)SiO{sub 2}:25Na{sub 2}O:10CaO:xEr{sub 2}O{sub 3} (where x=0.02, 0.05, 0.1, 0.3, 0.5, 1, 2, 3, 4 and 5) were prepared by the melt quenching method. ESR measurements were carried out at room temperature down to 1.62 K. Absorption spectra were investigated in the UV-VIS-NIR region from 300 to 1800 nm. Photoluminescence spectra were observed in the spectral range 500-800 nm under 514.5 nm argon-ion laser line excitation.

  3. Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, E.

    1985-11-01

    The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by /sup 29/Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of /sup 29/Si spectra. A high-temperature (to 1300/sup 0/C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T/sub 1/ and T/sub 2/) measurements as a function of composition and temperature for /sup 23/Na and /sup 29/Si.

  4. An Overview of the Origin of A-type Silicic Magmatism Along the Snake River Plain-Yellowstone Hotspot Track

    Science.gov (United States)

    Christiansen, E. H.; Bindeman, I. N.; Leishman, J. R.

    2015-12-01

    Disparate models have been proposed for the origin of A-type rhyolites--a volumetrically minor part of modern terrestrial magmatism. But understanding the origin of A-type granites and rhyolites has significance for understanding the formation of the Earth's first silicic crust and for planetary magmatism--small volumes of such granitic materials have been found in lunar rocks, martian and asteroidal meteorites, and have been speculated to have formed on Venus. On other planets, vertical tectonics and plume-like mantle convection dominate, not the recycling of wet, oxidized plates of lithosphere as on Earth. Thus, understanding the origins of A-type silicic magma is important on multiple levels. Voluminous A-type rhyolite were produced on the Snake River Plain-Yellowstone hotspot track and provide the opportunity to better understand these important silicic magmas. Detailed petrologic studies suggest that most Snake River Plain rhyolites ultimately formed by partially melting of previously emplaced basaltic intrusions rather than by fractional crystallization of basalt or melting of Archean crust. This hypothesis is favored because of the bimodal association of rhyolite and basalt without linking intermediate compositions. In addition, incompatible element ratios (e.g., La/Nb, Pb/Ce), a lack of old zircon antecrysts, low-U inherited zircon, high ɛNd and ɛHf values, high eruption temperatures (1050°C to 850°C), low fO2 (near QFM), and H2O (as low as 1.5%), link the rhyolites to a plume-derived basaltic parent through partial melting with lesser incorporation of the Archean to Mesozoic crust that underlies the plain. Moreover, the contrast with wetter, lower temperature rhyolites that must have formed by direct crustal melting (e.g., Arbon Valley Tuff) strengthens this interpretation. Many of the rhyolites also have low δ18O values that must be produced in two stages: first by partial melting of already hydrothermally altered basalt, and subsequently in single

  5. The structural role of manganese ions in soil active silicate-phosphate glasses.

    Science.gov (United States)

    Szumera, Magdalena

    2014-08-14

    Silicate-phosphate glasses of SiO2P2O5K2OMgOCaO system containing manganese ions were synthesized by the melt-quenching technique and were investigated to obtain information about the influence of Mn-cations on the glass structure and their chemical activity. Structural properties were studied using X-ray method, FTIR and Raman spectroscopies. The chemical activity of analyzed glasses in the 2 wt.% citric acid solution was measured by chemical analysis (ICP-AES, EDS) and SEM observations. It has been found that increasing amount of MnO2 in the structure of investigated glasses causes their gradual depolymerization. This process is more apparent in the case of the silico-oxygen subnetwork than phospho-oxygen one. This is related to increasing amounts of SiO4 tetrahedra containing two nonbridging oxygen atoms in silico-oxygen subnetwork. It has been also found that the presence of "weaker" chemical bonds of SiOMn type in comparison to SiOCa and SiOMg bonds is responsible for the increase in solubility of the analyzed silicate-phosphate glasses in conditions simulating natural soil environment. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Fe2O3 Modified Physical, Structural and Optical Properties of Bismuth Silicate Glasses

    Directory of Open Access Journals (Sweden)

    Rajesh Parmar

    2013-01-01

    Full Text Available Iron-containing bismuth silicate glasses with compositions 60SiO2·(100−xBi2O3·xFe2O3 have been prepared by conventional melt-quenching technique. The amorphous nature of the glass samples has been ascertained by the X-ray diffraction. The density (d has been measured using Archimedes principle, molar volume (Vm has also been estimated, and both are observed to decrease with the increase in iron content. The glass transition temperature (Tg of these iron bismuth silicate glasses has been determined using differential scanning calorimetry (DSC technique, and it increases with the increase in Fe2O3 content. The IR spectra of these glasses consist mainly of [BiO6], [BiO3], and [SiO4] structural units. The optical properties are measured using UV-VIS spectroscopy. The optical bandgap energy (Eop is observed to decrease with the increase in Fe2O3 content, whereas reverse trend is observed for refractive index.

  7. Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

    Science.gov (United States)

    Elsheimer, H.N.; Fries, T.L.

    1990-01-01

    A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of tricotylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 ??g l-1 of tin in the MIBK solution or 0.2-0.3 ??g g-61 in the rock. The concentration range is linear between 2.5 and 500 ??g l-1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 ??g l-1 level and < 7% at the 10-30 ??g l-1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 ??g g-1 or less.

  8. Assessment of inclusive education

    DEFF Research Database (Denmark)

    Miller, Tanja

    2014-01-01

    The focus of this paper is on the way teachers, in teams can work with assessing the inclusive practice in their own classes. In 2012 a joint effort between CEPRA, teachers and school administrators from the municipality of Hjørring developed a dialog based model for continually assessing...... the quality of the learning environment in regard to inclusion – this model draws heavily on the logic and mindset of ECERS (Early child environment program). This article will relate the rationale of the assessment model called “Dialoger om Kvalitet” (dialogues on quality) to LSP’s definition of inclusion...

  9. Inclusion in Elementary Schools

    Directory of Open Access Journals (Sweden)

    Susan Allan Galis

    1995-10-01

    Full Text Available This study of reform policy focused on inclusive education in the 1990s in the state of Georgia, United States of America. Program modifications including, individualizing instructional methods, adapting the instructional environment, and lowering maximum class size emerged as significant issues. We found that policies related to these areas were compounded by the less experienced educators not readily accepting change strategies for serving students. Apparently younger educators are engrossed in surviving daily routine and have difficulty coping with the complex demands of change. Regular education teachers have difficulty with the idea of inclusion. Legal aspects dealing inclusion need clarification, especially for regular education teachers.

  10. Methods for Melting Temperature Calculation

    Science.gov (United States)

    Hong, Qi-Jun

    Melting temperature calculation has important applications in the theoretical study of phase diagrams and computational materials screenings. In this thesis, we present two new methods, i.e., the improved Widom's particle insertion method and the small-cell coexistence method, which we developed in order to capture melting temperatures both accurately and quickly. We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments. We propose the small-cell coexistence method based on the statistical analysis of small-size coexistence MD simulations. It eliminates the risk of a metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated melting points. The method converges to the exact result in the limit of a large system size. An accuracy within 100 K in melting temperature is usually achieved when the simulation contains more than 100 atoms. DFT examples of Tantalum, high-pressure Sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which

  11. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10(12) mol Si per year, which makes them...... the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d......Si-limited conditions in a chemokinetic response and, if gradients of this resource are present, increased directionality of cell movement promotes chemotaxis. The ability to exploit local and short-lived dSi hotspots using a specific search behaviour likely contributes to micro-scale patch dynamics in biofilm...

  12. Thermal Ablation Modeling for Silicate Materials

    Science.gov (United States)

    Chen, Yih-Kanq

    2016-01-01

    A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  13. Lithium alumino-silicate ion source development

    Science.gov (United States)

    Roy, Prabir Kumar; Seidl, Peter A.; Kwan, Joe W.; Greenway, Wayne G.; Waldron, William L.; Wu, James K.; Mazaheri, Kavous

    2009-11-01

    We report experimental progress on Li+ source development in preparation for warm dense matter heating experiments. To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, we are pursuing the use of a low (E spodumene and β-eucryptite, each of area 0.31 cm2, have been fabricated for ion emission measurements. These surface ionization sources are heated to 1200 to 1300 C where they preferentially emit singly ionized alkali ions. Tight process controls were necessary in preparing and sintering the alumino-silicate to the porous tungsten substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. Current density limit of the two kinds have been measured, and ion species identification of possible contaminants has been verified with a Wien (E x B) filter.

  14. Homogenisation of sulphide inclusions within diamonds: A new approach to diamond inclusion geochemistry

    Science.gov (United States)

    McDonald, Iain; Hughes, Hannah S. R.; Butler, Ian B.; Harris, Jeffrey W.; Muir, Duncan

    2017-11-01

    widening the scope for multiple methods for quantitative analysis, even on 'flakes' of single BMS inclusions. Finally we show that the trace elements present in peridotite (P-type) and eclogitic (E-type) BMS are distinct, with P-type diamonds having systematically higher total platinum-group element (particularly Os, Ir, Ru) and Te and As concentrations. These distinctions suggest that the PGE and semi-metal budgets of mantle-derived partial melts will be significantly dependent upon the type(s) and proportions of sulphides present in the mantle source.

  15. Petrochemistry of late miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia

    Science.gov (United States)

    Morgan, VI G.B.; London, D.; Luedke, R.G.

    1998-01-01

    Late Miocene peraluminous volcanic rocks of the Morococala field, Bolivia, define a layered stratigraphy of basal andalusite-, biotite-(?? Muscovite)-bearing rhyolite tuffs (AR), overlain by cordierite-, biotite-bearing rhyolite tuffs (CR), and capped by biotite-beanng quartz latite tuffs, lavas, and late domal flows (QL). Mineral and whole-rock compositions become more evolved from top to bottom, with differentiation reflected by decreasing Ca, Ba, Mg, Fe, and rare earth elements (REE) versus increasing F, Na/K, and aluminosity from QL to AR. Mineral, whole-rock, and glass inclusion compositions are consistent with derivation of all three rock types from a single stratified magma reservoir, but age and spatial relations between the three units make this unlikely. Genesis of the QL involved biotite-dehydration melting of an aluminous source at T > 750??C and P ??? 4-6 kbar. If not co-magmatic with QL, the other units were generated primarily by muscovite-dehydration melting at T = 730-750??C and P ??? 3??5-4??5 kbar for CR, and T ??? 750??C for AR with pre-emptive residence at low pressure (1??5-3??0 kbar). Low hematite contents (XHem ??? 0??06) of ilmenite grains in AR, CR, and early grains (as inclusions in plagioclase and sanidine cores) in QL indicate reduced conditions imposed by a graphite-bearing source. Compositional variability among texturally later oxides (ilmenite with XHem = 0??06-0??50, primary magnetite), however, apparently records progressive increases in pre-eruptive f(O2) in QL. Plagioclase-melt equilibria and electron microprobe analysis difference for quartz-hosted glass inclusions suggest pre-emptive melt H2O contents ??? 5-7 wt % for the AR, ???4-6 wt % for the CR, and ???3-5 wt % for the QL.

  16. Evidence on Inclusion

    DEFF Research Database (Denmark)

    Dyssegaard, Camilla Brørup; Larsen, Michael Søgaard

    The purpose of this publication is to examine existing research on inclusion to identify strategies of inclusion that have generated positive effects. To do so it is necessary to understand the effect of the applied strategies. One approach, which is being discussed, is to use evidence to determine...... which methods have proven more effective than others. The desire to gain insight into research on inclusion forms the basis of the current systematic review. The task was to determine which strategies primary research has found to be most effective for inclusion purposes. We have solved this task...... by addressing the existing research with the following question: What is the effect of including children with special needs in mainstream teaching in basic school, and which of the applied educational methods have proved to have a positive effect?...

  17. Can we build inclusion?

    DEFF Research Database (Denmark)

    Kirkeby, Inge Mette; Grangaard, Sidse

    2016-01-01

    of some children with special needs. Hence the title – can we build inclusion? In the literature of Universal Design, accommodation and design features seldom reflect the less visible disabilities. The paper is based on a research project initiated to investigate how more or less space influences daily......Inclusion of children with special needs in kindergartens and preschools may be approached from different angles. This paper raises the question of whether the physical framework of kindergartens makes any difference for daily life at the kindergarten at all, and whether it can support inclusion...... on the answers in the interviews, we found support for answering the question in the title in the affirmative; we can build inclusion! This is because the teachers' experience indicated that, if there was sufficient space per child, there were fewer conflicts and the children managed to stay in the same activity...

  18. Inclusive Education in Israel

    National Research Council Canada - National Science Library

    O. V. Mayzel

    2013-01-01

    To get acquainted with the practice of inclusive education in mainstream schools, with professionals who work with special children, to visit the specialist centers to share experiences - all of this...

  19. Slab melting as a barrier to deep carbon subduction.

    Science.gov (United States)

    Thomson, Andrew R; Walter, Michael J; Kohn, Simon C; Brooker, Richard A

    2016-01-07

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir.

  20. Melting in temperature sensitive suspensions

    Science.gov (United States)

    Alsayed, Ahmed M.

    We describe two experimental studies about melting in colloidal systems. In particular we studied melting of 1-dimensional lamellar phases and 3-dimensional colloidal crystals. In the first set of experiments we prepared suspensions composed of rodlike fd virus and the thermosensitive polymer, poly(N-isopropylacrylamide). The phase diagram of this systems is temperature and concentration dependent. Using video microscopy, we directly observed melting of lamellar phases and single lamellae into nematic phase. We found that lamellar phases swell with increasing temperature before melting into the nematic phase. The highly swollen lamellae can be superheated as a result of topological nucleation barriers that slow the formation of the nematic phase. In another set of experiments we prepared colloidal crystals from thermally responsive microgel spheres. The crystals are equilibrium close-packed three-dimensional structures. Upon increasing the temperature slightly above room temperature, particle volume fraction decreased from 0.74 to less than 0.5. Using video microscopy, we observed premelting at grain boundaries and dislocations within bulk colloidal crystals. Premelting is the localized loss of crystalline order at surfaces and defects at sample volume fractions above the bulk melting transition. Particle tracking revealed increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. In total these observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and in atomic scale crystals.

  1. RISKS OF INCLUSIVE EDUCATION

    Directory of Open Access Journals (Sweden)

    M. R. Husnutdinova

    2017-01-01

    Full Text Available Introduction. Inclusion is a new and unfamiliar phenomenon for most of the Russians which is treated as ensuring equal access to education for all students taking into account a variety of their special educational needs and individual capabilities. Inclusive educational model began to take root in Russia without a broad public debate and today’s parents and teachers were not ready to the cardinal changes caused by transition to the new model of education. In this regard, the studying of directly educational process by consequences of inclusive training and education is urgent now.The aims of the research are the following: to identify the major risks that characterize the current stage of the implementation process of inclusion in the Russian educational organizations; to consider the main causes that lead to their occurrence; to present a comparative analysis of the views of respondents in comprehensive, inclusive and correctional schools. Methodology and research methods. The Sector Monitoring Studies of Moscow State University of Psychology & Education in 2010 and 2014 implemented a sociological study on the process of introduction of inclusion in the Russian schools. 200 teachers and 244 parents were interviewed in 2010; in 2014, in addition, 178 teachers and 386 parents were interviewed; 47 senior students including those with disabilities were interviewed too.Results. According to the results, the main concerns of the parents of students of comprehensive, inclusive and correctional schools are reduced to a few basic risks: lack of individual approach while teaching children with different educational needs, increased emotional pressure on the child, and child’s perception of the complexity of disability as an equal. These risks arise primarily because of the acute shortage of especially prepared-governmental teachers and socio-cultural, psychological unpreparedness of most contemporary children with disabilities to the perception of

  2. The Origin of the Compositional Diversity of Mercury's Surface Constrained From Experimental Melting of Enstatite Chondrites

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

    2015-01-01

    Mercury is known as an endmember planet as it is the most reduced terrestrial planet with the highest core/mantle ratio. MESSENGER spacecraft has shown that its surface is FeO-poor (2-4 wt%) and Srich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. Moreover, high resolution images revealed large volcanic plains and abundant pyroclastic deposits, suggesting important melting stages of the Mercurian mantle. This interpretation was confirmed by the high crustal thickness (up to 100 km) derived from Mercury's gravity field. This is also corroborated by a recent experimental result that showed that Mercurian partial melts are expected to be highly buoyant within the Mercurian mantle and could have risen from depths as high as the core-mantle boundary. In addition MESSENGER spacecraft provided relatively precise data on major elemental compositions of Mercury's surface. These results revealed important chemical and mineralogical heterogeneities that suggested several stages of differentiation and re-melting processes. However, the extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Therefore, in this study, we investigated the processes that lead to the various compositions of Mercury's surface. Melting experiments with bulk Mercury-analogue compositions were performed and compared to the compositions measured by MESSENGER.

  3. A IAB-Complex Iron Meteorite Containing Low-Ca Clinopyroxene: Northwest Africa 468 and its Relationship to Iodranites and Formation by Impact Melting

    Science.gov (United States)

    Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

    2002-01-01

    Northwest Africa 468 (NWA 468) is a new ungrouped, silicate-rich member of the IAB complex of nonmagmatic iron meteorites. The silicates contain relatively coarse (approximately 300 micron-size) grains of low-Ca clinopyroxene with polysynthetic twinning and inclined extinction. Low-Ca clinopyroxene is indicative of quenching from high temperatures (either from protoenstatite in a few seconds or high-temperature clinoenstatite in a few hours). It seems likely that NWA 468 formed by impact melting followed by rapid cooling to less than or equal to 660 C. After the loss of a metal-sulfide melt from the silicates, sulfide was reintroduced, either from impact-mobilized FeS or as an S2 vapor that combined with metallic Fe to produce FeS. The O-isotopic composition (delta O-17 = -1.39 %) indicates that the precursor material of NWA 468 was a metal-rich (e.g., CR) carbonaceous chondrite. Lodranites are similar in bulk chemical and O-isotopic composition to the silicates in NWA 468; the MAC 88177 lodranite (which also contains low-Ca clinopyroxene) is close in bulk chemical composition. Both NWA 468 and MAC 88177 have relatively low abundances of REE (rare earth elements) and plagiophile elements. Siderophiles in the metal-rich areas of NWA 468 are similar to those in the MAC 88177 whole rock; both samples contain low Ir and relatively high Fe, Cu and Se. Most unweathered lodranites contain approximately 20 - 38 wt. % metallic Fe-Ni. These rocks may have formed in an analogous manner to NWA 468 (i.e., by impact melting of metal-rich carbonaceous-chondrite precursors) but with less separation of metal-rich melts from silicates.

  4. Eruption style at Kīlauea Volcano in Hawai‘i linked to primary melt composition

    Science.gov (United States)

    Sides. I.R.,; Edmonds, M.; Maclennan, J.; Swanson, Don; Houghton, Bruce F.

    2014-01-01

    Explosive eruptions at basaltic volcanoes have been linked to gas segregation from magmas at shallow depths in the crust. The composition of primary melts formed at greater depths was thought to have little influence on eruptive style. Ocean island basaltic volcanoes are the product of melting of a geochemically heterogeneous mantle plume and are expected to give rise to heterogeneous primary melts. This range in primary melt composition, particularly with respect to the volatile components, will profoundly influence magma buoyancy, storage and eruption style. Here we analyse the geochemistry of a suite of melt inclusions from 25 historical eruptions at the ocean island volcano of Kīlauea, Hawai‘i, over the past 600 years. We find that more explosive styles of eruption at Kīlauea Volcano are associated statistically with more geochemically enriched primary melts that have higher volatile concentrations. These enriched melts ascend faster and retain their primary nature, undergoing little interaction with the magma reservoir at the volcano’s summit. We conclude that the eruption style and magma-supply rate at Kīlauea are fundamentally linked to the geochemistry of the primary melts formed deep below the volcano. Magmas might therefore be predisposed towards explosivity right at the point of formation in their mantle source region.

  5. Fire Resistance of Wood Impregnated with Soluble Alkaline Silicates

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Giudice

    2007-01-01

    Full Text Available The aim of this paper is to determine the fire performance of wood panels (Araucaria angustifolia impregnated with soluble alkaline silicates. Commercial silicates based on sodium and potassium with 2.5/1.0 and 3.0/1.0 silica/alkali molar ratios were selected; solutions and glasses were previously characterized. Experimental panels were tested in a limiting oxygen chamber and in a two-foot tunnel. Results displayed a high fire-retardant efficiency using some soluble silicates.

  6. Electrical conduction and glass relaxation in alkali- silicate glasses

    Science.gov (United States)

    Angel, Paul William

    Electrical response measurements from 1 Hz to 1 MHz between 50o and 540oC were made on potassium, sodium and lithium-silicate glasses with low alkali oxide contents. Conductivity and electrical relaxation responses for both annealed and air quenched glasses of the same composition were compared. Quenching was found to lower the dc conductivity, σdc, and activation energy as well as increase the pre-exponential term when compared to the corresponding annealed glass of the same composition. All of the glasses exhibited Arrhenius behavior in the log σdc against 1/T plots. A sharp decrease in σdc was observed for glasses containing alkali concentrations of 7 mol% or less. The σdc activation energy exhibited similar behavior when plotted as a function of alkali composition and was explained in terms of a mixture of the weak and strong electrolyte models. The depression angle for fits to the complex impedance data were also measured as a function of thermal history, alkali concentration and alkali species. These results were interpreted in terms of changes in the distribution of relaxation times. Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450o to 800oC, held isothermally for 20 min, and then quenched in either air or silicon oil. The complex impedance of both an annealed and the quenched samples were then measured as a function of temperature from 120o to 250oC. The σdc was found to be remain unaffected by heat treatments below 450oC, to increase rapidly over an approximate 200oC range of temperatures that was dependent on cooling rate and to be constant for heat treatments above this range. This behavior is interpreted in terms of the mean structural relaxation time as a function of temperature and cooling rate near the glass transition temperature and glass transformation ranges. A more detailed definition for the transition and transformation temperatures and ranges was also provided.

  7. Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites

    DEFF Research Database (Denmark)

    Baker, J.; Bizzarro, Martin; Wittig, N.

    2005-01-01

    Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages...... for these meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides (Al and Fe) injected from a nearby...

  8. Chemical stratification in the silicate earth

    Science.gov (United States)

    Herzberg, C. T.

    1983-01-01

    A primary stratigraphic model is presented for the distribution of depleted, enriched, and primordial isotopic mantle components that have been formed by the transport of magmas at the begining of geological history. Depleted midoceanic ridge basalt source regions were established in the uppermost part of the upper mantle, while the primordial mantle was located at the middle and deepest regions of an upper mantle which was processed by anhydrous melting and crystallization. The lower mantle became heterogeneous, with enrichments at the top and depletions elsewhere. It is suggested that the present day isotopic structure of the mantle has inherited elements of this primary stratification.

  9. Genesis of diamond inclusions: An integrated cathodoluminescence (CL) and Electron backscatter diffraction (EBSD) study on eclogitic and peridotitic inclusions and their diamond host.

    Science.gov (United States)

    van den Heuvel, Quint; Matveev, Sergei; Drury, Martyn; Gress, Michael; Chinn, Ingrid; Davies, Gareth

    2017-04-01

    Diamond inclusions are potentially fundamental to understanding the formation conditions of diamond and the volatile cycles in the deep mantle. In order to fully understand the implications of the compositional information recorded by inclusions it is vital to know whether the inclusions are proto-, syn-, or epigenetic and the extent to which they have equilibrated with diamond forming fluids. In previous studies, the widespread assumption was made that the majority of diamond inclusions are syngenetic, based upon observation of cubo-octahedral morphology imposed on the inclusions. Recent work has reported the crystallographic relationship between inclusions and the host diamond to be highly complex and the lack of crystallographic relationships between inclusions and diamonds has led some to question the significance of imposed cubo-octahedral morphology. This study presents an integrated EBSD and CL study of 9 diamonds containing 20 pyropes, 2 diopsides, 1 forsterite and 1 rutile from the Jwaneng and Letlhakane kimberlite clusters, Botswana. A new method was developed to analyze the crystallographic orientation of the host diamond and the inclusions with EBSD. Diamonds plates were sequentially polished to expose inclusions at different levels in the diamond. CL imaging at different depths was performed in order to produce a 3D view of diamond growth zones around the inclusions. Standard diamond polishing techniques proved too aggressive for silicate inclusions as they were damaged to such a degree that EBSD measurements on the inclusions were impossible. The inclusions were milled with a Ga+ focused ion beam (FIB) at a 12° angle to clean the surface for EBSD measurements. Of the 24 inclusions, 9 have an imposed cubo-octahedral morphology. Of these inclusions, 6 have faces orientated parallel to diamond growth zones and/or appear to have nucleated on a diamond growth surface, implying syngenesis. In contrast, other diamonds record resorption events such that

  10. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

  11. The effect of viscosity on the kinetics of redox reactions in highly viscous silicate liquids.

    Science.gov (United States)

    Kido, Ladislav; Müller, Matthias; Rüssel, Christian

    2012-06-14

    The kinetics of the temperature dependent redox reaction between chromium and manganese (Cr(6+) + 3Mn(2+)⇌Cr(3+) + 3Mn(3+)) in highly viscous silicate melts were studied by UV-vis-NIR spectroscopy at temperatures in the range from 25 to 800 °C. At high temperatures, the reaction is in equilibrium. During cooling, it is continuously shifted to the right. During cooling from Tg+50 K to Tg (Tg = glass transition temperature), a further decrease in the Cr(6+) concentration was obtained which, however, was less pronounced if larger cooling rates were applied. In this temperature range, the kinetics plays an important part. Finally, at a certain temperatures below Tg, the equilibrium was frozen. The temperature, the equilibrium is frozen in decreases with decreasing cooling rate. It also decreases with the glass transition temperature of the respective composition. The activation energies increase with the activation energies of the viscosity of the respective melt. The redox reaction is controlled by the viscosity, i.e., the rearrangement of the glass network and not by diffusion. The reason is a drastic change in the coordination spheres during the reaction which leads to a high inner reorganization energy according to Marcus' Theory.

  12. Inclusive Physical Education

    DEFF Research Database (Denmark)

    Østergaard, Charlotte; Rostbøll, Solveig Fogh

    2015-01-01

    EN317 - Inclusive Physical Education - with a focus on active and successful participation Charlotte Østergaard, Solveig Fogh Rostbøll, Department of School and Learning, Metropolitan University College (DK) chao@phmetropol.dk The Danish School Reform 2014 intends to raise the amount and intensity...... and is often a bad experience for students who do not have the required skills or the necessary competitive mentality. The purpose of the study is to generate increased knowledge of how to work with inclusive education in PE in schools. The aims of the study are to identify groups of “outsiders” and to find...... on the 6th and 7th grade and specifically on girls. The data consists of observations in 8 classes from 4 schools and focus group combined with in-depth interviews with 18 selected girls before and after a 7 weeks intervention in Inclusive PE. The study investigates whether the lack of motivation...

  13. Delimiting Inclusive Design

    DEFF Research Database (Denmark)

    Herriott, Richard

    2014-01-01

    technology (AT). There are a few papers (e.g. REF) which hint at the role that could be played by ID in the realm of public transport (PT) where accessibility is mandated by law. Taking these three disciplines as the three key areas of industrial design in its broadest sense, this paper provides a synthesis...... of work done in three previous papers. The first paper considered cases of ID and AT as reported in two major, relevant conference series. The second paper consisted of an analysis of nine cases of design for public transport (REF). The third paper consisted of an analysis of nine cases of design......This paper was written as an answer to the question raised by my PhD dissertation on accessibility through user-centred and Inclusive Design (ID) methods: can Inclusive Design be delimited? The literature on Inclusive Design deals almost entrirely with consumer product design and assistive...

  14. Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the mesosiderite parent body

    Science.gov (United States)

    Haba, Makiko K.; Yamaguchi, Akira; Kagi, Hiroyuki; Nagao, Keisuke; Hidaka, Hiroshi

    2017-10-01

    Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2

  15. Study of Meteoritic Inclusion

    DEFF Research Database (Denmark)

    Olsen, Mia Bjørg Stolberg

    ionization mass spectrometry (SIMS). Moreover, we have shown that combining careful petrological investigations with high-precision isotope measurements of multiple systems on single meteoritic inclusions can potentially provide unique insights into the formation history of the solar system's earliest solids...... and the observation of a reduced initial abundance of 26Al in the accretion regions of chondrules and asteroidal bodies impacts our understanding of the accretion timescales of protoplanets in a significant way. Combining high-precision isotope measurements of multiple systems on individual meteoritic inclusions...

  16. Creative activity and inclusion

    Directory of Open Access Journals (Sweden)

    Shemanov A.Yu.

    2013-09-01

    Full Text Available The aim of the article was to analyze the inclusion potential of art creative activity, namely of theatre performance, in people with disabilities. The article provides examples of disagreements in understanding the significance of these art activities for exercising the rights of people with disabilities to contribute to culture and art and some problems arising here. The conclusion is made that theatre art performed by people with disabilities is gradually changing its function: from being a means of self-affirmation to the determination of its specific place in overall theatre process. These changes confirm the inclusion potential of theatre art activity.

  17. Conversion of rice hull ash into soluble sodium silicate

    Directory of Open Access Journals (Sweden)

    Edson Luiz Foletto

    2006-09-01

    Full Text Available Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2. About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

  18. Study of thermal effects of silicate-containing hydroxyapatites

    Science.gov (United States)

    Golovanova, O. A.; Zaits, A. V.; Berdinskaya, N. V.; Mylnikova, T. S.

    2016-02-01

    The possibility of modifications of hydroxyapatite silicate ions, from the extracellular fluid prototype solution under near-physiological conditions has been studied. Formation of silicon-structured hydroxyapatite with different extent of substitution of phosphate groups in the silicate group has been established through chemical and X-ray diffraction analyses, FTIR spectroscopy and optical microscopy. The results obtained are in agreement and suggest the possibility of substitution of phosphate groups for silicate groups in the hydroxyapatite structure when introducing different sources of silica, tetraethoxysilane and sodium silicate, in the reaction mixture. Growth in the amount of silicon in Si-HA results in the increase in the thermal stability of the samples. The greatest mass loss occurs at temperatures in the range of 25-400 0C that is caused by the removal of the crystallization and adsorption water and volatile impurities. It is shown that the modified apatites are of imperfect structure and crystallize in a nanocrystalline state.

  19. Silicate Urolithiasis during Long-Term Treatment with Zonisamide

    Directory of Open Access Journals (Sweden)

    Satoru Taguchi

    2013-01-01

    Full Text Available Silicate urinary calculi are rare in humans, with an incidence of 0.2% of all urinary calculi. Most cases were related to excess ingestion of silicate, typically by taking magnesium trisilicate as an antacid for peptic ulcers over a long period of time; however, there also existed unrelated cases, whose mechanism of development remains unclear. On the other hand, zonisamide, a newer antiepileptic drug, is one of the important causing agents of iatrogenic urinary stones in patients with epilepsy. The supposed mechanism is that zonisamide induces urine alkalinization and then promotes crystallization of urine components such as calcium phosphate by inhibition of carbonate dehydratase in renal tubular epithelial cells. Here, we report a case of silicate urolithiasis during long-term treatment with zonisamide without magnesium trisilicate intake and discuss the etiology of the disease by examining the silicate concentration in his urine.

  20. Tris (catecholato) silicates of nickel: Synthesis, characterization and ...

    Indian Academy of Sciences (India)

    catecholato)silicates of nickel: Synthesis, characterization and first observation of inter-ion ligand transfer. J Vijeyakumar Kingston G S M Sundaram M N Sudheendra Rao. Volume 112 Issue 3 June 2000 pp 402-402 ...

  1. Conversion of rice hull ash into soluble sodium silicate

    OpenAIRE

    Edson Luiz Foletto; Ederson Gratieri; Leonardo Hadlich de Oliveira; Sérgio Luiz Jahn

    2006-01-01

    Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA) and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reacti...

  2. Comparison of silicon nanoparticles and silicate treatments in fenugreek.

    Science.gov (United States)

    Nazaralian, Sanam; Majd, Ahmad; Irian, Saeed; Najafi, Farzaneh; Ghahremaninejad, Farrokh; Landberg, Tommy; Greger, Maria

    2017-06-01

    Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO2 particles, phytoliths, similar to SiO2-nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-lyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L.) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  3. Effects of silicate application on soil fertility and wheat yield

    Directory of Open Access Journals (Sweden)

    Marcos Vinícius Mansano Sarto

    2015-12-01

    Full Text Available An improvement in soil chemical properties and crop development with silicate application has been confirmed in several plant species. The effects of silicate application on soil chemical properties and wheat growth were investigated in the present study. The experiment was carried out in 8-L plastic pots in a greenhouse. Treatments were arranged in a randomized block design in a 3 × 5 factorial: three soils [Rhodic Acrudox (Ox1, Rhodic Hapludox (Ox2 and Arenic Hapludult (Ult] and five silicate rates (0, 1, 2, 4 and 6 Mg ha–1 of calcium/magnesium silicate, with four replications. The plant length, number of spikes per pot, shoot dry matter and grain yield, were measured after 115 days of wheat (Triticum aestivum L. growth. Changes in the soil chemical properties (pH, H+ + Al3+, Al3+, P, K, Ca, Mg, Si, Cu, Zn, Fe and Mn were analyzed after wheat harvest. Application of calcium/magnesium silicate reduces the potential acidity (H+ + Al3+ and Al3+ phytotoxic; and increases the soil pH, available Ca, Mg and Si, cation exchange capacity (CEC and soil base saturation. Silicate application did not affect the available P, exchangeable K and availability of micronutrients (Cu, Zn, Fe and Mn in the three soils. The application of calcium/magnesium silicate in an acid clayey Rhodic Hapludox improves the development and yield of wheat; however, the silicate application in soil with pH higher to 5.3 and high Si availability does not affect the agronomic characteristics and grain yield of wheat. 

  4. History of Nebular Processing Traced by Silicate Stardust in IDPS

    Science.gov (United States)

    Messenger, Scott R.; Keller, L. P.; Nakamura-Messenger, K.

    2010-01-01

    Chondritic porous interplanetary dust particles (CP-IDPs) may be the best preserved remnants of primordial solar system materials, in part because they were not affected by parent body hydrothermal alteration. Their primitive characteristics include fine grained, unequilibrated, anhydrous mineralogy, enrichment in volatile elements, and abundant molecular cloud material and silicate stardust. However, while the majority of CP-IDP materials likely derived from the Solar System, their formation processes and provenance are poorly constrained. Stardust abundances provide a relative measure of the extent of processing that the Solar System starting materials has undergone in primitive materials. For example, among primitive meteorites silicate stardust abundances vary by over two orders of magnitude (less than 10-200 ppm). This range of abundances is ascribed to varying extents of aqueous processing in the meteorite parent bodies. The higher average silicate stardust abundances among CP-IDPs (greater than 375 ppm) are thus attributable to the lack of aqueous processing of these materials. Yet, silicate stardust abundances in IDPs also vary considerably. While the silicate stardust abundance in IDPs having anomalous N isotopic compositions was reported to be 375 ppm, the abundance in IDPs lacking N anomalies is less than 10 ppm. Furthermore, these values are significantly eclipsed among some IDPs with abundances ranging from 2,000 ppm to 10,000 ppm. Given that CP-IDPs have not been significantly affected by parent body processes, the difference in silicate stardust abundances among these IDPs must reflect varying extents of nebular processing. Here we present recent results of a systematic coordinated mineralogical/isotopic study of large cluster IDPs aimed at (1) characterizing the mineralogy of presolar silicates and (2) delineating the mineralogical and petrographic characteristics of IDPs with differing silicate stardust abundances. One of the goals of this study is

  5. Melting, vaporization, and energy partitioning for impacts on asteroidal and planetary objects

    Science.gov (United States)

    Smither, Catherine L.; Ahrens, Thomas J.

    1992-01-01

    A three-dimensional smoothed particle hydrodynamics code was used to model normal and oblique impacts of silicate projectiles on asteroidal and planetary bodies. The energy of the system, initially in the kinetic energy of the impactor, is partitioned after impact into internal and kinetic energy of the impactor and the target body. These simulations show that, unlike the case of impacts onto a half-space, a significant amount of energy remains in the kinetic energy of the impacting body, as parts of it travel past the main planet and escape the system. This effect is greater for more oblique impacts, and for impacts onto the small planets. Melting and vaporization of both bodies were also examined. The amount of the target body melted was much greater in the case of smaller targets than for an impact of a similar scale on a larger body.

  6. Mechanical and thermal properties of melt processed PLA/organoclay nanocomposites

    Science.gov (United States)

    Ibrahim, Norazura; Jollands, Margaret; Parthasarathy, Rajarathinam

    2017-04-01

    Polylactic acid (PLA) and organically modified layered silicates (organoclay) with concentrations of 2-10 wt% were prepared by melt intercalation technique. The effects of organoclay on the mechanical and thermal properties of PLA were studied. Tensile properties were evaluated using an Instron Universal Tester. Modulated differential scanning calorimetry (MDSC) and Thermogravimetric analyses (TGA) were performed to study the thermal behaviour of the prepared composites. The nanocomposites exhibited superior improvement of practical materials properties such as Young’s modulus and thermal stability, as compared to the neat PLA. The Young’s modulus drastically increased, whereas tensile strength and elongation at break decreased. The maximum degradation temperature of the hybrid increased linearly with an increasing amount of organoclay. However, MDSC has determined that the glass transition, cold crystallisation, and melting point temperatures were not significantly influenced by the presence of organoclay.

  7. Linguistic Diversity and Social Inclusion

    Science.gov (United States)

    Piller, Ingrid; Takahashi, Kimie

    2011-01-01

    This introduction provides the framework for the special issue by describing the social inclusion agenda of neoliberal market democracies. While the social inclusion agenda has been widely adopted, social inclusion policies are often blind to the ways in which language proficiency and language ideologies mediate social inclusion in linguistically…

  8. Silicates in orthopedics and bone tissue engineering materials.

    Science.gov (United States)

    Zhou, Xianfeng; Zhang, Nianli; Mankoci, Steven; Sahai, Nita

    2017-07-01

    Following the success of silicate-based glasses as bioactive materials, silicates are believed to play important roles in promoting bone formation and have therefore been considered to provide a hydroxyapatite (HAP) surface layer capable of binding to bone as well as potentially being a pro-osteoinductive factor. Natural silicate minerals and silicate-substituted HAPs are also being actively investigated as orthopaedic bone and dental biomaterials for application in tissue engineering. However, the mechanisms for the proposed roles of silicate in these materials have not been fully understood and are controversial. Here, we review the potential roles of silicate for bone tissue engineering applications and recent breakthroughs in identifying the cellular-level molecular mechanisms for the osteoinductivity of silica. The goal of this article is to inspire new ideas for the rational design of third-generation cell-and gene-affecting biomaterials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2090-2102, 2017. © 2017 Wiley Periodicals, Inc.

  9. Designing Inclusive Spaces

    DEFF Research Database (Denmark)

    Colfelt, Solvej

    2012-01-01

    CWUAAT -6.TH CAMBRIDGE WORKSHOP – 2012 Designing inclusive systems for real-world applications Abstracht: Denmark has planned huge investments in development in healthcare systems. Nearly 50 billion danish krones has been set aside on the stately budget for this purpose to be spent over the next 10...

  10. Multilingualism and social inclusion

    NARCIS (Netherlands)

    Marácz, L.; Adamo, S.

    2017-01-01

    This is a thematic issue on the relation between multilingualism and social inclusion. Due to globalization, Europeanization, supranational and transnational regulations linguistic diversity and multilingualism are on the rise. Migration and old and new forms of mobility play an important role in

  11. Nanotubular Toughening Inclusions

    Science.gov (United States)

    Park, Cheol (Inventor); Working, Dennis C. (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

    2017-01-01

    Conventional toughening agents are typically rubbery materials or small molecular weight molecules, which mostly sacrifice the intrinsic properties of a matrix such as modulus, strength, and thermal stability as side effects. On the other hand, high modulus inclusions tend to reinforce elastic modulus very efficiently, but not the strength very well. For example, mechanical reinforcement with inorganic inclusions often degrades the composite toughness, encountering a frequent catastrophic brittle failure triggered by minute chips and cracks. Thus, toughening generally conflicts with mechanical reinforcement. Carbon nanotubes have been used as efficient reinforcing agents in various applications due to their combination of extraordinary mechanical, electrical, and thermal properties. Moreover, nanotubes can elongate more than 20% without yielding or breaking, and absorb significant amounts of energy during deformation, which enables them to also be an efficient toughening agent, as well as excellent reinforcing inclusion. Accordingly, an improved toughening method is provided by incorporating nanotubular inclusions into a host matrix, such as thermoset and thermoplastic polymers or ceramics without detrimental effects on the intrinsic physical properties of the matrix.

  12. Anthropology and inclusive development

    NARCIS (Netherlands)

    Bakker, L.; Nooteboom, G.

    Although the term inclusive development is still rare in anthropological texts, it is a key element of anthropology’s relation to development. Concerns of in/exclusion, unequal power relations and (lack of) voice are central here. Anthropology’s encounter with development primarily focuses on a

  13. Peer Tutoring for Inclusion

    Science.gov (United States)

    Temple, Viviene A.; Lynnes, Michelle D.

    2008-01-01

    Peer tutoring is a pedagogical technique that has promise to improve outcomes for students with a disability within existing resource constraints. Published empirically-based papers on peer-tutoring were descriptively analysed. Synthesis of these studies revealed that peer tutoring is effective in inclusive physical education contexts. Evidence…

  14. Inclusion Requires Fracturing

    Science.gov (United States)

    Anila, Swarupa

    2017-01-01

    Inclusion strategies and approaches in interpretive planning processes for exhibitions are often resisted because they challenge precedents in museum practice. Maintaining traditional models may seem more comfortable for many museum professionals than to do the work of closely examining, fracturing, and transforming the practices that prioritize…

  15. Relationships in Inclusive Classrooms

    Science.gov (United States)

    Santos, Graça Duarte; Sardinha, Susana; Reis, Silvia

    2016-01-01

    Climate in the classroom is one of the determining factors in the development of practices in Inclusive Education. Many factors contribute to the climate in the classroom. However, there are predominance on affective-relational factors, with impact on action, norms and values, social interactions and learning processes. In this paper, the authors…

  16. Optimization of inclusive fitness.

    Science.gov (United States)

    Grafen, Alan

    2006-02-07

    The first fully explicit argument is given that broadly supports a widespread belief among whole-organism biologists that natural selection tends to lead to organisms acting as if maximizing their inclusive fitness. The use of optimization programs permits a clear statement of what this belief should be understood to mean, in contradistinction to the common mathematical presumption that it should be formalized as some kind of Lyapunov or even potential function. The argument reveals new details and uncovers latent assumptions. A very general genetic architecture is allowed, and there is arbitrary uncertainty. However, frequency dependence of fitnesses is not permitted. The logic of inclusive fitness immediately draws together various kinds of intra-genomic conflict, and the concept of 'p-family' is introduced. Inclusive fitness is thus incorporated into the formal Darwinism project, which aims to link the mathematics of motion (difference and differential equations) used to describe gene frequency trajectories with the mathematics of optimization used to describe purpose and design. Important questions remain to be answered in the fundamental theory of inclusive fitness.

  17. Mathematics Teaching and Inclusion

    DEFF Research Database (Denmark)

    This volume contains the proceedings of the 3rd Nordic Research Conference on Special Needs Education in Mathematics, which took place in Rebild organised by Aalborg University in November 23-25, 2005. The theme of the conference was Mathematics Education and Inclusion. The conference theme...

  18. Basal terraces on melting ice shelves

    National Research Council Canada - National Science Library

    Dutrieux, Pierre; Stewart, Craig; Jenkins, Adrian; Nicholls, Keith W; Corr, Hugh F. J; Rignot, Eric; Steffen, Konrad

    2014-01-01

    Ocean waters melt the margins of Antarctic and Greenland glaciers, and individual glaciers' responses and the integrity of their ice shelves are expected to depend on the spatial distribution of melt...

  19. On the Mg/Fe Ratio in Silicate Minerals in the Circumstellar Environments I. The Mg/Fe Ratio in Silicate Mineral Constituents of the Kaba Meteorite

    Science.gov (United States)

    Futó, P.

    2017-11-01

    The moderately high ratio of Mg in the silicates of the solar environment indicates that Mg-rich silicates are likely to be frequent in the interstellar medium and the circumstellar environments in case of chondritic-like composition.

  20. Effect of layered silicate content on the morphology and thermal properties of Poly(vinyl alcohol) films; Efeito do teor de silicato em camadas na morfologia e propriedades termicas de filmes de poli(alcool vinilico)

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jessica R.M.B. da; Santos, Barbara F.F. dos; Leite, Itamara F., E-mail: jraquell@homail.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Centro de Tecnologia. Departamento de Engenharia de Materiais

    2015-07-01

    This study aims to evaluate the effect of layered silicate content on the morphology and thermal properties of PVA films. The PVA/layered silicate (AN) films were prepared by intercalation solution, using 1 to 2% of bentonite with respect to the PVA total weight. Then the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). Results of the FTIR revealed interaction between the functional groups of the PVA and the layered silicate. The XRD analysis showed that nanocomposites with intercalated and partially exfoliated morphology were obtained. The results of TG showed that the nanocomposite PVA/2%AN showed higher thermal stability compared to PVA/1%AN. The DSC results showed that the addition of AN to the PVA did not affect crystallization rate, as well as promoted a reduction in glass transition temperature and melting of the PVA. (author)

  1. Durability of Silicate Glasses: An Historical Approach

    Energy Technology Data Exchange (ETDEWEB)

    Farges, Francois; /Museum Natl. Hist. Natur. /Stanford U., Geo. Environ. Sci.; Etcheverry, Marie-Pierre; /Marne la Vallee U.; Haddi, Amine; /Marne la Valle U.; Trocellier,; /Saclay; Curti, Enzo; /PSI, Villigen; Brown, Gordon E., Jr.; /SLAC, SSRL

    2007-01-02

    We present a short review of current theories of glass weathering, including glass dissolution, and hydrolysis of nuclear waste glasses, and leaching of historical glasses from an XAFS perspective. The results of various laboratory leaching experiments at different timescales (30 days to 12 years) are compared with results for historical glasses that were weathered by atmospheric gases and soil waters over 500 to 3000 years. Good agreement is found between laboratory experiments and slowly leached historical glasses, with a strong enrichment of metals at the water/gel interface. Depending on the nature of the transition elements originally dissolved in the melt, increasing elemental distributions are expected to increase with time for a given glass durability context.

  2. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Cruz

    2013-01-01

    Full Text Available The control of Asian Soybean Rust (ASR, caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS and soil amendment with calcium silicate (CS on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection process of P. pachyrhizi was investigated by scanning electron microscopy. The uredia on leaves of plants sprayed with PS were smaller and more compact than those observed on the leaves of plants grown in soil amended with CS or in soil non-amended with CS (control treatment. On leaves of plants from the control treatment, uredia produced many urediniospores at 9 days after inoculation, and the ASR severity was 15, 8 and 9%, respectively, for plants from control, PS and CS treatments. In conclusion, the spray of PS contributed to reduce the number of uredia per cm² of leaf area and both PS spray and CS resulted in lower ASR symptoms.

  3. Experimental determination of CO2 content at graphite saturation along a natural basalt-peridotite melt join: Implications for the fate of carbon in terrestrial magma oceans

    Science.gov (United States)

    Duncan, Megan S.; Dasgupta, Rajdeep; Tsuno, Kyusei

    2017-05-01

    Knowledge of the carbon carrying capacity of peridotite melt at reducing conditions is critical to constrain the mantle budget and planet-scale distribution of carbon set at early stage of differentiation. Yet, neither measurements of CO2 content in reduced peridotite melt nor a reliable model to extrapolate the known solubility of CO2 in basaltic (mafic) melt to solubility in peridotitic (ultramafic) melt exist. There are several reasons for this gap; one reason is due to the unknown relative contributions of individual network modifying cations, such as Ca2+ versus Mg2+, on carbonate dissolution particularly at reducing conditions. Here we conducted high pressure, temperature experiments to estimate the CO2 contents in silicate melts at graphite saturation over a compositional range from natural basalts toward peridotite at a fixed pressure (P) of 1.0 GPa, temperature (T) of 1600 °C, and oxygen fugacity (log ⁡ fO2 ∼ IW + 1.6). We also conducted experiments to determine the relative effects of variable Ca and Mg contents in mafic compositions on the dissolution of carbonate. Carbon in quenched glasses was measured and characterized using Fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy and was found to be dissolved as carbonate (CO32-). The FTIR spectra showed CO32- doublets that shifted systematically with the MgO and CaO content of silicate melts. Using our data and previous work we constructed a new composition-based model to determine the CO2 content of ultramafic (peridotitic) melt representative of an early Earth, magma ocean composition at graphite saturation. Our data and model suggest that the dissolved CO2 content of reduced, peridotite melt is significantly higher than that of basaltic melt at shallow magma ocean conditions; however, the difference in C content between the basaltic and peridotitic melts may diminish with depth as the more depolymerized peridotite melt is more compressible. Using our model of CO2 content at

  4. Viscoelastic properties of polymer based layered-silicate nanocomposites

    Science.gov (United States)

    Ren, Jiaxiang

    Polymer based layered-silicate nanocomposites offer the potential for dramatically improved mechanical, thermal, and barrier properties while keeping the material density low. Understanding the linear and non-linear viscoelastic response for such materials is crucial because of the ability of such measurements to elucidate the mesoscale dispersion of layered-silicates and changes in such dispersion to applied flows as would be encountered in processing of these materials. A series of intercalated polystyrene (and derivatives of polystyrene) layered-silicate nanocomposites are studied to demonstrate the influence of mesoscale dispersion and organic---inorganic interactions on the linear and non-linear viscoelastic properties. A layered-silicate network structure is exhibited for the nanocomposites with strong polymer-silicate interaction such as montmorillonite (2C18M) and fluorohectorite (C18F) and the percolation threshold is ˜ 6 wt % for the 2C18M based hybrids. However, the nanocomposites based on hectorite (2C18H) with weak polymer-silicate interaction exhibit liquid-like terminal zone behavior. Furthermore, the enhanced terminal zone elastic modulus and viscosity of high brominated polystyrene and high molecular weight polystyrene based 2C18M nanocomposites suggest an improved delamination and dispersion of layered-silicates in the polymer matrix. The non-linear viscoelastic properties, specifically, the non-linear stress relaxation behavior and the applicability of time---strain separability, the effect of increasing strain amplitude on the oscillatory shear flow properties, and the shear rate dependence of the steady shear flow properties are examined. The silicate sheets (or collections of sheets) exhibit the ability to be oriented by the applied flow. Experimentally, the empirical Cox - Merz rule is demonstrated to be inapplicable for the hybrids. Furthermore, the K-BKZ constitutive model is used to model the steady shear properties. While being able to

  5. Petrological Geodynamics of Mantle Melting I. AlphaMELTS + Multiphase Flow: Dynamic Equilibrium Melting, Method and Results

    Directory of Open Access Journals (Sweden)

    Massimiliano Tirone

    2017-10-01

    Full Text Available The complex process of melting in the Earth's interior is studied by combining a multiphase numerical flow model with the program AlphaMELTS which provides a petrological description based on thermodynamic principles. The objective is to address the fundamental question of the effect of the mantle and melt dynamics on the composition and abundance of the melt and the residual solid. The conceptual idea is based on a 1-D description of the melting process that develops along an ideal vertical column where local chemical equilibrium is assumed to apply at some level in space and time. By coupling together the transport model and the chemical thermodynamic model, the evolution of the melting process can be described in terms of melt distribution, temperature, pressure and solid and melt velocities but also variation of melt and residual solid composition and mineralogical abundance at any depth over time. In this first installment of a series of three contributions, a two-phase flow model (melt and solid assemblage is developed under the assumption of complete local equilibrium between melt and a peridotitic mantle (dynamic equilibrium melting, DEM. The solid mantle is also assumed to be completely dry. The present study addresses some but not all the potential factors affecting the melting process. The influence of permeability and viscosity of the solid matrix are considered in some detail. The essential features of the dynamic model and how it is interfaced with AlphaMELTS are clearly outlined. A detailed and explicit description of the numerical procedure should make this type of numerical models less obscure. The general observation that can be made from the outcome of several simulations carried out for this work is that the melt composition varies with depth, however the melt abundance not necessarily always increases moving upwards. When a quasi-steady state condition is achieved, that is when melt abundance does not varies significantly

  6. Host rock solid-state transformation in a shock-induced melt vein of Tenham L6 chondrite

    Science.gov (United States)

    Xie, Zhidong; Sharp, Thomas G.

    2007-02-01

    The host-rock fragments entrained in a 580-μm-wide melt vein of the Tenham L6 chondrite were investigated using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) to better understand the solid-state transformation mechanisms and the shock conditions. The melt vein consists of a matrix of silicate plus metal-sulfide that crystallized from immiscible melts, and sub-rounded host-rock fragments that have been entrained in the melt and transformed to polycrystalline high-pressure silicates by solid-state transformation mechanisms. These high-pressure phases include ringwoodite, low-Ca majorite, clinoenstatite, hollandite-structured plagioclase and Ca-rich majorite. The Ca-rich majorite occurs as a symplectitic intergrowth with a Ca-poor amorphous silicate phase in a 200 μm-diameter chondrule in the vein. This intergrowth seems to be the result of a disproportionate breakdown of a Ca-rich clinopyroxene precursor into Ca-rich majorite and (FeMg)SiO 3 perovskite, which subsequently vitrified upon pressure release. The TEM observations suggest that most solid-state transformations in the Tenham are reconstructive. The transformation of olivine to polycrystalline ringwoodite appears to involve incoherent intracrystalline nucleation and interface-controlled growth. Lamellae in partially transformed olivine are not continuous coherent lamellae, but rather lamellae of polycrystalline ringwoodite, which is inconsistent with a coherent lamellar transformation mechanism. Growth rate calculations based on published kinetic data suggest that the time required to grow 1 μm ringwoodite crystal is ˜ 100 ms at 1600 K, suggesting that the minimum shock pulse of approximately 100 ms.

  7. Filament stretching rheometry of polymer melts

    DEFF Research Database (Denmark)

    Hassager, Ole; Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz

    2005-01-01

    The Filament Stretching Rheometry (FSR) method developed by Sridhar, McKinley and coworkers for polymer solutions has been extended to be used also for polymer melts. The design of a melt-FSR will be described and differences to conventional melt elongational rheometers will be pointed out. Results...

  8. Gas-driven filter pressing in magmas: insights into in-situ melt segregation from crystal mushes

    Science.gov (United States)

    Pistone, M.; Arzilli, F.; Dobson, K. J.; Cordonnier, B.; Reusser, E.; Ulmer, P.; Marone, F.; Whittington, A. G.; Mancini, L.; Fife, J.; Blundy, J. D.

    2015-12-01

    Gas-driven filter pressing is the process of melt expulsion from a volatile-saturated crystal mush, induced by the buildup and subsequent release of gas pressure. Filter pressing is inferred to play a major role in magma fractionation at shallow depths (filter pressing to segregate melt. Hydrous haplogranite (2.1 wt% water in the melt) and dacite (4.2 wt% water in the melt) crystal mushes, with a wide range of crystallinities (34-80 vol% crystals), were investigated using in-situ, high temperature (500-800 °C) synchrotron X-ray tomographic microscopy with high spatial (3 micron/pixel) and temporal resolution (~8 s per 3D data set). The experimental results show that gas-driven filter pressing operates only below the maximum packing of bubbles and crystals (~74 vol%). Above this threshold, the mush tends to fracture and gas escapes via fractures. Therefore, the efficiency of gas-driven filter pressing is promoted close to the percolation threshold and in situations where a mush inflates slowly relative to build-up of pressure and expulsion of melt. Such observations offer a likely explanation for the production of eruptible, crystal-poor magmas within Earth's crust. Figure = Synchrotron X-ray tomographic microscopy 3D renderings of representative haplogranite (A-D) and dacite (E-H) samples, with different crystal (Φ) and bubble fractions (β) at representative temperatures and experimental times (t, in minutes). Black objects are bubbles and fractures; dark gray field is silicic glass/melt; light gray objects are corundum crystals in haplogranite sample, and quartz in dacite sample. White and black arrows indicate representative fractures and directions of melt expulsion during vesiculation, respectively. In H, white contours highlight quartz cluster boundaries and melt channels where melt is driven by gas bubbles. During experiments, gas exsolution mainly consists of (1) bubble nucleation and growth (white circles) and (2) crystal clustering and/or compaction

  9. The Formation and Chronology of the PAT 91501 Impact-Melt L-Chondrite with Vesicle-Metal-Sulfide Assemblages

    Science.gov (United States)

    Benedix, G. K.; Ketcham, R. A.; Wilson, L.; McCoy, T. J.; Bogard, D. D.; Garrison, D. H.; Herzog, G. F.; Xue, S.; Klein, J.; Middleton, R.

    2007-01-01

    The L chondrite Patuxent Range (PAT) 41 91501 is an 8.5-kg unshocked, homogeneous, igneous-textured impact melt that cooled slowly compared to other meteoritic impact melts in a crater floor melt sheet or sub-crater dike. We conducted mineralogical and tomographic studies of previously unstudied mm- to cm-sized metal-sulfide-vesicle assemblages and chronologic studies of the silicate host. Metal-sulfide clasts constitute about 1 vol.%, comprise zoned taenite, troilite and pentlandite, and exhibit a consistent orientation between metal and sulfide and of metal-sulfide contacts. Vesicles make up approximately 2 vol.% and exhibit a similar orientation of long axes. Ar-39-Ar-40 measurements date the time of impact at 4.461 +/- 0.008 Gyr B.P. Cosmogenic noble gases and Be-10 and Al-2l activities suggest a pre-atmospheric radius of 40-60 cm and a cosmic ray exposure age of 25-29 Myr, similar to ages of a cluster of L chondrites. PAT 91501 dates the oldest known impact on the L chondrite parent body. The dominant vesicle-forming gas was S2 (approximately 15-20 ppm), which formed in equilibrium with impact-melted sulfides. The meteorite formed in an impact melt dike beneath a crater, as did other impact melted L chondrites, such as Chico. Cooling and solidification occurred over approximately 2 hours. During this time, approximately 90% of metal and sulfide segregated from the local melt. Remaining metal and sulfide grains oriented themselves in the local gravitational field, a feature nearly unique among meteorites. Many of these metal sulfide grains adhered to vesicles to form aggregates that may have been close to neutrally buoyant. These aggregates would have been carried upward with the residual melt, inhibiting further buoyancy-driven segregation. Although similar processes operated individually in other chondritic impact melts, their interaction produced the unique assemblage observed in PAT 91501.

  10. Grain boundary melting in ice

    OpenAIRE

    Thomson, E. S.; Hansen-Goos, Hendrik; Wilen, L. A.; Wettlaufer, J. S.

    2012-01-01

    We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentr...

  11. Hadron melting and QCD thermodynamics

    OpenAIRE

    Jakovac, A.

    2013-01-01

    We study in this paper mechanisms of hadron melting based on the spectral representation of hadronic quantum channels, and examine the hadron width dependence of the pressure. The findings are applied to a statistical hadron model of QCD thermodynamics, where hadron masses are distributed by the Hagedorn model and a uniform mechanism for producing hadron widths is assumed. According to this model the hadron - quark gluon plasma transition occurs at $T\\approx 200$-250 MeV, the numerically obse...

  12. Inclusive differentiated instruction

    Directory of Open Access Journals (Sweden)

    Jerković Ljiljana S.

    2017-01-01

    Full Text Available Inclusive differentiated instruction is a new model of didactic instruction, theoretically described and established in this paper for the first time, after being experimentally verified through teaching of the mother tongue (instruction in reading and literature. Inclusive individually planned instruction is based on a phenomenological and constructivist didactic instructional paradigm. This type of teaching is essentially developmental and person-oriented. The key stages of inclusive differentiated instruction of literature are: 1 recognition of individual students' potential and educational needs regarding reading and work on literary texts; 2 planning and preparation of inclusive individually planned instruction in reading and literature; 3 actual class teaching of lessons thus prepared; and 4 evaluation of the student achievement following inclusive differentiated instruction in reading and literature. A highly important element of the planning and preparation of inclusive differentiated instruction is the creation of student profiles and inclusive individualized syllabi. Individualized syllabi specify the following: 1. a brief student profile; 2. the student position on the continuum of the learning outcomes of instruction in the Serbian language; 3. reverse-engineered macro-plan stages of instruction in the Serbian language (3.1. identifying expected outcomes and fundamental qualities of learners' work, 3.2. defining acceptable proofs of their realisation, 3.3. planning learning and teaching experiences, and 3.4. providing material and technical requisites for teaching; 4 the contents and procedure of individualized lessons targeting the student; 5 a plan of syllabus implementation monitoring and evaluation. The continuum of the learning outcomes of inclusive differentiated instruction in literature exists at three main levels, A, B and C. The three levels are: A reading techniques and learning about the main literary theory concepts; B

  13. COMPARISON OF SOL-GEL SILICATE COATINGS ON Ti SUBSTRATE

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    DIANA HORKAVCOVÁ

    2012-12-01

    Full Text Available The objective of the submitted work was to prepare and to characterize two types of silicate coatings prepared by the sol-gel method using the dip-coating technique on a titanium substrate. Efforts have been made to use mechanical properties of bio-inert titanium and bioactive properties of a silicate layer enriched with an admixture of compounds identified below. The first group consisted of silicate coatings containing silver, brushite and monetite. The other group of silicate coatings contained calcium nitrate and triethyl phosphate. Mechanically and chemically treated titanium substrates were dipped into sols and dried and fired. Silicate coatings from the first group were also chemically treated in 10 mol.l-1 solution of sodium hydroxide. All coatings were measured to determine their adhesive and bioactive properties and furthermore the antibacterial properties were tested in the case of first group. Surfaces of the coated substrates were investigated after the firing and after the individual tests with optical and electron microscopy and X-ray microdiffraction. A tape test demonstrated excellent adhesive property of all coatings to the substrate, classified with degree 5. A static in vitro test demonstrated bioactivity of nearly all the coatings. The basic silicate coating from the first group and one type of coating from the second group were identified as inert. Antibacterial properties of silicate coatings containing silver showed to be different when tested against Escherichia coli bacteria. A complete inhibition of the growth of bacteria under our experimental conditions was observed for the coating containing silver and monetite and a partial inhibition of the growth of bacteria for coatings containing silver and silver in combination with brushite.

  14. Structural Stability and Mobility of Carbonate Minerals and Melts in the Earth's Mantle

    Science.gov (United States)

    Liu, J.; Caracas, R.; Fan, D.; Zhang, D.; Mao, W. L.

    2015-12-01

    Knowledge of potential carbon carriers such as the mantle carbonate minerals and melts is critical for our understanding of the deep-carbon cycle and related geological processes within the planet. Although rhombohedral carbonates (e.g., calcite, magnesite, and siderite) have been proposed as a major carbon carrier in the Earth's crust and upper mantle, several distinct scenarios have been proposed for these carbonates at deep-mantle conditions including chemical dissociation and various structural transitions. Recently, carbonate melts have been reported to be highly mobile at high pressure and temperature (P-T) conditions, which may have significant impact on magmatic processes in Earth's upper mantle. However, the high P-T behaviors of carbonate minerals and melts are still not well understood, in terms of their structural stability and mobility in the Earth's lower mantle. Combining in-situ synchrotron X-ray diffraction (XRD), transmission X-ray microscopy (TXM), and Raman spectroscopy experiments in a laser-heated diamond anvil cell with complementary theoretical calculations, we investigate the phase stability of carbonates, the equation of state (EoS) of carbonatic glasses, as well as the distribution of carbonate melts in a silicate matrix up to lower-mantle conditions.

  15. INTEGRATION-INCLUSION

    OpenAIRE

    KERAMITCHIEVSKA-BILJANOVSKA Vesna; MITREVSKA Roberta; SABOLICH Nada

    2015-01-01

    By defining the terms, we would like to show that mentally disabled children cannot follow the regular educational process, in the same way children without learning disabilities can.The process of rehabilitation and education of disabled persons with different kind of disabilities, enables independent social integration and good quality of living in our country in the last 50 years; throw there is no need of changes in the inclusive education.

  16. Multilingualism and Social Inclusion

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    László Marácz

    2017-12-01

    Full Text Available This is a thematic issue on the relation between multilingualism and social inclusion. Due to globalization, Europeanization, supranational and transnational regulations linguistic diversity and multilingualism are on the rise. Migration and old and new forms of mobility play an important role in these processes. As a consequence, English as the only global language is spreading around the world, including Europe and the European Union. Social and linguistic inclusion was accounted for in the pre-globalization age by the nation-state ideology implementing the ‘one nation-one people-one language’ doctrine into practice. This lead to forced linguistic assimilation and the elimination of cultural and linguistic heritage. Now, in the present age of globalization, linguistic diversity at the national state level has been recognized and multilingual states have been developing where all types of languages can be used in governance and daily life protected by a legal framework. This does not mean that there is full equality of languages. This carries over to the fair and just social inclusion of the speakers of these weaker, dominated languages as well. There is always a power question related to multilingualism. The ten case studies in this thematic issue elaborate on the relation between multilingualism and social inclusion. The articles in this issue refer to this topic in connection with different spaces, including the city, the island, and the globe; in connection with different groups, like Roma in the former Soviet-Union and ethnic Albanians in Macedonia; in connection with migration and mobility of Nordic pensioners to the south of Europe, and language education in Scotland; and finally in connection with bilingual education in Austria and Estonia as examples of successful practices including multilingualism under one and the same school roof.

  17. Core crystallization and silicate-metal mixing in the parent body of the IVA iron and stony-iron meteorites

    Science.gov (United States)

    Scott, Edward R. D.; Haack, Henning; McCoy, Timothy J.

    1996-05-01

    We have analyzed metallic and silicate phases in the IVA iron meteorites and two related stony irons, Steinbach and São João Nepomuceno. Analyses of bulk metal phases in the two stony irons using INAA show that they plot as close to the chemical trends within group IVA as most IVA irons, indicating a common source. Our fractional crystallization models for the IVA chemical trends suggest that the irons crystallized from a metallic melt that initially contained 2.5 ± 1 wt% S. After S concentrations in the liquid reached 6 wt%, liquid trapping during crystallization increased the apparent distribution coefficient for S, as in group IIIAB. Compositions of the metal fractions in Steinbach and São João Nepomuceno match the calculated solid compositions after 50 ± 10% and 80 ± 10%, respectively, of the metallic melt had crystallized. We confidently conclude that the IVA irons and metal in the two stony irons were derived from the core of a single asteroid that fractionally crystallized. The wide range of metallographic cooling rates of IVA irons cannot result from crystallization in isolated pools in one or more bodies, as some authors have argued. Large depletions of Ga, Ge, and other moderately volatile elements in group IVA are unlikely to result from planetary processes; they may have been inherited from chondritic precursor material. The two IVA stony irons contain up to 60 vol% of a unique, coarse-grained mixture of tridymite, orthobronzite, and clinobronzite. Silicate-metal textures resemble those in rounded-olivine pallasites; both may result from the depression of cumulate silicates into underlying molten S-rich metal. Two IVA irons contain rare plate-like, silica crystals up to 10 mm long, but these occurrences seem unrelated to the stony-iron silicates. Because of the difficulty in forming the stony irons in an isolated, slowly cooling asteroid, we infer that they may have formed during the breakup and reassembly event invoked by Haack et al. (1995) to

  18. Petrogenesis of Miller Range 07273, a new type of anomalous melt breccia: Implications for impact effects on the H chondrite asteroid

    Science.gov (United States)

    Ruzicka, Alex M.; Hutson, Melinda; Friedrich, Jon M.; Rivers, Mark L.; Weisberg, Michael K.; Ebel, Denton S.; Ziegler, Karen; Rumble, Douglas; Dolan, Alyssa A.

    2017-09-01

    Miller Range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine-grained (shapes for coarse metal grains, unusual internal textures and compositions for coarse metal, a matrix composed chiefly of clinoenstatite and omphacitic pigeonite, and troilite veining most common in coarse olivine and orthopyroxene. These features can be explained by a model involving impact into a porous target that produced brief but intense heating at high pressure, a sudden pressure drop, and a slower drop in temperature. Olivine and orthopyroxene in chondrule clasts were the least melted and the most deformed, whereas matrix and troilite melted completely and crystallized to nearly strain-free minerals. Coarse metal was largely but incompletely liquefied, and matrix silicates formed by the breakdown during melting of albitic feldspar and some olivine to form pyroxene at high pressure (>3 GPa, possibly to 15-19 GPa) and temperature (>1350 °C, possibly to ≥2000 °C). The higher pressures and temperatures would have involved back-reaction of high-pressure polymorphs to pyroxene and olivine upon cooling. Silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration.

  19. Optimization of Melt Treatment for Austenitic Steel Grain Refinement

    Science.gov (United States)

    Lekakh, Simon N.; Ge, Jun; Richards, Von; O'Malley, Ron; TerBush, Jessica R.

    2017-02-01

    Refinement of the as-cast grain structure of austenitic steels requires the presence of active solid nuclei during solidification. These nuclei can be formed in situ in the liquid alloy by promoting reactions between transition metals (Ti, Zr, Nb, and Hf) and metalloid elements (C, S, O, and N) dissolved in the melt. Using thermodynamic simulations, experiments were designed to evaluate the effectiveness of a predicted sequence of reactions targeted to form precipitates that could act as active nuclei for grain refinement in austenitic steel castings. Melt additions performed to promote the sequential precipitation of titanium nitride (TiN) onto previously formed spinel (Al2MgO4) inclusions in the melt resulted in a significant refinement of the as-cast grain structure in heavy section Cr-Ni-Mo stainless steel castings. A refined as-cast structure consisting of an inner fine-equiaxed grain structure and outer columnar dendrite zone structure of limited length was achieved in experimental castings. The sequential of precipitation of TiN onto Al2MgO4 was confirmed using automated SEM/EDX and TEM analyses.

  20. Evolution of the volcanic plumbing systemof Alicudi (Aeolian Islands - Italy: evidence from fluid and melt inclusionsin quartz xenoliths

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    A. Peccerillo

    2004-06-01

    Full Text Available Quartz-rich xenoliths in lavas (basalts to andesites; 90-30 ka from Alicudi contain abundant melt and fluid inclusions. Two generations of CO2-rich fluid inclusions are present in quartz-rich xenolith grains: early (Type I inclusions related to partial melting of the host xenoliths, and late Type II inclusions related to the fluid trapping during xenolith ascent. Homogenisation temperatures of fluid inclusions correspond to two density intervals: 0.93-0.68 g/cm3 (Type I and 0.47-0.26 g/cm3 (Type II. Early Type I fluid inclusions indicate trapping pressures around 6 kbar, which are representative for the levels of partial melting of crustal rocks and xenolith formation. Late Type II fluid inclusions show lower trapping pressures, between 1.7 kbar and 0.2 kbar, indicative for shallow magma rest and accumulation during ascent to the surface. Data suggest the presence of two magma reservoirs: the first is located at lower crustal depths (about 24 km, site of fractional crystallization, mixing with source derived magma, and various degrees of crustal assimilation. The second magma reservoir is located at shallow crustal depths (about 6 km, the site where magma rested for a short time before erupting.

  1. The ash chemistry in fluidized bed gasification of biomass fuels. Part 1: predicting the chemistry of melting ashes and ash-bed material interaction

    Energy Technology Data Exchange (ETDEWEB)

    Zevenhoven-Onderwater, M.; Backman, R.; Skrifvars, B.-J.; Hupa, M. [Aabo Akademi University, Turku (Finland). Dept. of Chemical Engineering, Combustion Chemistry Research Group

    2001-08-10

    This paper describes the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600-900{degree}C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620{degree}C with each of the seven biomass fuels fired. In silica-rich cases melt can be expected at temperatures above 770{degree}C. The amount of melt is rather high. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620{degree}C. At temperatures above 800{degree}C, a silicate melt can form as well. The amount of melt was high showing a significant contribution of the bed material. 39 refs., 15 figs., 2 tabs.

  2. Iron in Silicate Glasses: Systematic Analysis of Pre-Edge And Xanes Features

    Energy Technology Data Exchange (ETDEWEB)

    Farges, F.; Rossano, S.; Wilke, M.; Lefrere, Y.; Brown, G.E., Jr.; /SLAC, SSRL

    2006-10-27

    A large number (67) of silicate glasses containing variable amounts of iron oxide were studied by high-resolution XANES spectroscopy at the Fe K-edge to determine an accurate method to derive redox information from pre-edge features. The glass compositions studied mimic geological magmas, ranging from basaltic to rhyolitic, dry and hydrous, with variable quench rates. The studied glasses also include more chemically simple calco-sodic silicate glass compositions. The Fe contents range from 30 wt.% to less than 2000 ppm. For most of the series of composition studied, the pre-edge information varies linearly with redox, even under high-resolution conditions. The average coordination of Fe(II) is often similar to its Fe(III) counterpart except in highly polymerized glasses because of the strong influence exerted by the tetrahedral framework on iron's sites. Natural volcanic glasses (from various volcanoes around the world) show similar variations. The average coordination of Fe(II) is often comprised between 4.5 and 5. Fe(III) shows larger variations in coordination (4 to 6, depending on composition). Bond valence models are proposed to predict the average coordination of Fe based on composition. Molecular dynamics simulations (Born-Mayer-Huggins) potentials were carried out on some compositions to estimate the magnitude of disorder effects (both static and thermal) in the XAFS analysis. XANES calculations based on the MD simulations and FEFF 8.2 show large variations in the local structures around Fe. Also, 5-coordinated Fe(III) is found to be an important moiety in ferrisilicate glasses. For Fe(II), discrepancies between glass and melt are larger and are related to its greater structural relaxation at T{sub g}. Also, a strong destructive interference between network formers and modifiers explain the relatively weak intensity of the next-nearest neighbors contributions in the experimental spectra.

  3. Effect of melting technology on the properties of G17CrMo5-5 steel for cast turbines

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    P. Mańkowski

    2010-10-01

    Full Text Available Two technologies of the G17CrMo 5-5 cast steel melting were compared, i.e. the so far used oxygen-recovery melting technology (electricarc furnace + ladle furnace – EAF + LF and a new recovery melting technology (electric induction furnace + ladle furnace - EIF + LF.The effect of the melting technology on the properties of cast steel for turbine parts was determined. The cast steel was evaluated in term of its metallurgical purity and mechanical properties. During melting of G17CrMo 5-5 steel in induction furnace, lower total content of oxygen in casting was reached, but nitrogen content was higher than it was in the cast steel from arc furnace. Metal refining in LF improved the steel desulphurising degree and contributed to modification of the non-metallic inclusions.

  4. Detached Melt and Vapor Growth of InI in SUBSA Furnace

    Science.gov (United States)

    Ostrogorsky, A. G.; Riabov, V.; Volz, M. P.; van den Berg, L.; Croll, A.

    2017-01-01

    Indium iodide (InI) is a promising wide energy band gap nuclear detector material. It is ideal for space experiments because it is non-toxic and has a relatively low melting point of only 351 degrees Centigrade. However, it has been established that melt-grown crystals contain a large amount of second phase inclusions/precipitates. The typical size of