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  • 1
    Electronic Resource
    Electronic Resource
    Quests for low-degree mantle melts (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 286-286 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] BAKER ET AL. REPLY - Falloon et al assert that the melts generated in our near-solidus two-stage diamond-aggregate experiments1 represent disequilibrium liquids. Although space limitations prevent us from describing our current experimental work, we address each of their points below. (1) At ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381286a0
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  • 2
    Electronic Resource
    Electronic Resource
    Compositions of near-solidus peridotite melts from experiments and thermodynamic calculations (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 308-311 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The peridotite composition used in our experiments (Table 1) approximates 'primitive' upper mantle6 and was made from cleaned mineral separates (olivine (ol), orthopyroxene (opx), cpx and spinel (sp); all ^13 um in size). Design of the single-stage and two-stage ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375308a0
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  • 3
    Electronic Resource
    Electronic Resource
    A regular solution model for met-aluminous silicate liquids: Applications to geothermometry, immiscibility, and the source regions of basic magmas (1980)
    Springer
    Contributions to mineralogy and petrology 71 (1980), S. 323-342 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Adopting a set of multioxide components and using published compositional data on olivineand plagioclase-liquid equilibria we have developed a 17 component regular solution model for met-aluminous silicate liquids. The partial molar excess free energies predicted from this model can be used together with phenocryst compositions as an effective geothermometer, with an approximate error of 20 °C (30 °C for olivine, 12 °C for plagioclase). The regular solution formulation is also successful in predicting liquid immiscibility at (1) high mole fractions of silica commonly observed in phase diagrams, and at (2) lower temperatures in lunar basalts and intermediate lavas. The model yields activities of silica which are consistent with those obtained from solid-liquid silica buffers in rocks which contain olivine and enstatite or quartz. From predicted activities of KAlSi3O8 in liquids coexisting with plagioclase a value is obtained for the limiting Henry's law activity coefficient of KAlSi3O8 in the solid. This coefficient agrees well with that inferred from plagioclase-sanidine equilibrium phenocryst assemblages in rhyolites. The activities of silica obtained from this model are used to place constraints on the pressure-temperature regions where various types of basic magmas are generated. In conjunction with plagioclase geothermometry an application is given where the pressure, temperature, and water content of an olivine andesite is predicted from the activity of silica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374706
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures (1995)
    Springer
    Contributions to mineralogy and petrology 119 (1995), S. 197-212 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A revised regular solution-type thermodynamic model for twelve-component silicate liquids in the system SiO2–TiO2–Al2O3–Fe2O3–Cr2O3–FeO–MgO– CaO–Na2O–K2O–P2O5–H2O is calibrated. The model is referenced to previously published standard state thermodynamic properties and is derived from a set of internally consistent thermodynamic models for solid solutions of the igneous rock forming minerals, including: (Mg, Fe2+, Ca)-olivines, (Na, Mg, Fe2+, Ca)M2 (Mg, Fe2+, Ti, Fe3+, Al)M1 (Fe3+, Al, Si)2 TETO6- pyroxenes, (Na,Ca,K)-feldspars, (Mg, Fe2+) (Fe3+, Al, Cr)2O4-(Mg, Fe2+)2 TiO4 spinels and (Fe2+, Mg, Mn2+)TiO3-Fe2O3 rhombohedral oxides. The calibration utilizes over 2,500 experimentally determined compositions of silicate liquids coexisting at known temperatures, pressures and oxygen fugacities with apatite ±feldspar ±leucite ±olivine ±pyroxene ±quartz ±rhombohedral oxides ±spinel ±whitlockite ±water. The model is applicable to natural magmatic compositions (both hydrous and anhydrous), ranging from potash ankaratrites to rhyolites, over the temperature (T) range 900°–1700° C and pressures (P) up to 4 GPa. The model is implemented as a software package (MELTS) which may be used to simulate igneous processes such as (1) equilibrium or fractional crystallization, (2) isothermal, isenthalpic or isochoric assimilation, and (3) degassing of volatiles. Phase equilibria are predicted using the MELTS package by specifying bulk composition of the system and either (1) T and P, (2) enthalpy (H) and P, (3) entropy (S) and P, or (4) T and volume (V). Phase relations in systems open to oxygen are determined by directly specifying the f o2 or the T-P-f o2 (or equivalently H-P-f o2, S-P-f o2, T-V-f o2) evolution path. Calculations are performed by constrained minimization of the appropriate thermodynamic potential. Compositions and proportions of solids and liquids in the equilibrium assemblage are computed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050036
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  • 5
    Electronic Resource
    Electronic Resource
    Inverted high-temperature quartz (1979)
    Springer
    Contributions to mineralogy and petrology 68 (1979), S. 307-323 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Fifty-two samples of inverted high-temperature quartz from volcanic rocks were investigated by Guinier-Jago powder diffractometry and differential scanning calorimetry (DSC). Quartz megacrysts from Clear Lake and Cinder Cone, California show a variability of ≃2.5 ° K in their α-β transition temperature (T α-β). Quartz phenocrysts and quartz from crystalline rocks give a range of 0.5 ° K in T α-β. Neutron activation analysis of single crystals demonstrates that Al is the principal impurity (17–380 ppm). Its concentration is inversely correlated with T α-β. A very small variation was found in the a and c lattice parameters among the specimens of volcanic quartz studied. This variation does not correlate with Al content or transition temperature. Mean values at 22 ° C (a=4.1934±0.0004 Å, c=5.4046±0.0006 Å) are similar to those of quartz grown at low temperatures. Enthalpy of the α-β transition (ΔH α-β), obtained over 9.0 ° from DSC runs, is dependent upon sample grain size and for a crushed powder with zero hysteresis (T α-β on heating=T α-β on cooling) is 92.0 ±1.4 cal/mol. In contrast, a single piece of quartz requires ΔH α-β be 107.7±1.4 cal/mol and has a T α-β hysteresis of 1.1 ° K. Regression of published data provides equations for the variation of the molar volume (cc/mol) of quartz with v. These equations imply a ΔV α-β of 0.205±0.031 cc/- mol. Expressions are also provided for the temperature dependence of the thermal coefficient of expansion, α, the compressibility, β, and (∂/gb/∂T)p (which is identically -(∂α/∂P) T ). DSC heat capacity measurements over the range 400 to 900 ° K were fitted to extended Maier-Kelley type expressions to give: $$\begin{gathered} C_P = 10.31 + 9.116 \times 10^{ - 3} T - \frac{{1.812 \times 10^5 }}{{T^2 }} \hfill \\ - {\text{5}}{\text{.630}} \times 10^{ - 2} {\text{ }}\frac{T}{{(T - 848)}} - 0.3553\frac{T}{{(T - 848)^2 }} \hfill \\ - 0.9011\frac{T}{{\left( {T - 848} \right)^3 }} \hfill \\ (400{\text{ to 842}}^ \circ {\text{K), and}} \hfill \\ C_P = - 318.8 + 0.2532T \hfill \\ {\text{ + }}\frac{{8.687 \times 10^7 }}{{T^2 }} + 0.1603\frac{T}{{\left( {T - 848} \right)^4 }} \hfill \\ \end{gathered} $$ (851 to 900 ° K), which together with the values of ΔH α−β measured over the range 842–851° K give 7875.3 cal/mol for H900-H400. The behavior of α, β, and C p as a function of T emphasizes that structural changes which occur at the α−β transition do so over a broad temperature interval.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371553
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  • 6
    Electronic Resource
    Electronic Resource
    Ferric-ferrous equilibria in natural silicate liquids at 1 bar (1981)
    Springer
    Contributions to mineralogy and petrology 75 (1981), S. 369-376 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Ferric and ferrous iron concentrations have been measured in 57 silicate liquids equilibrated at temperatures (1,200°–1,330°C) above the liquidus and at oxygen fugacities close to those defined by quartz-fayalite-magnetite. The experimental results reported here span virtually the entire known compositional range of lavas. An empirical equation relating the mole fraction of Fe2O3 and FeO to oxygen fugacity, absolute temperature and liquid composition at 1 bar has been formulated, based on the present experimental results and published data. Extrapolating the proposed empirical relationship over several hundred degrees, for instance below the solidus of the 1965 Makaopuhi tholeiitic lava lake, yields calculated oxygen fugacities which are a little lower than those measured directly in drill holes; at 1,100°C this discrepancy is 0.4 log unit. However, the agreement between the oxygen fugacities calculated from our empirical equation and those indicated by the composition of Fe-Ti oxides in andesites and siliceous obsidians is much closer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374720
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamic analysis of the effect of magnetic ordering on miscibility gaps in the Fe−Ti cubic and rhombohedral oxide minerals and the Fe−Ti oxide geothermometer (1997)
    Springer
    Physics and chemistry of minerals 25 (1997), S. 28-38 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Thermodynamic models which incorporate the effects of long-range magnetic order are developed for mineral endmembers and their solid solutions. The temperature dependence of the magnetic entropy of solution is obtained from a statistical mechanical description of spin configurations. The non-configurational magnetic Gibbs Free energy is modeled as a Taylor expansion of low order and even degree. Taylor coefficients are calibrated from determinations of magnetic transition temperatures and from heat capacity measurements. The technique is used to derived model equations for the thermodynamic properties of magnetite (Fe3O4), hematite (Fe2O3) and the solid solution series magnetite-ulvöspinel (Fe2TiO4) and hematite-ilmenite (FeTiO3). These models are utilized to calculate phase diagrams, and the effect of the interplay between “magnetic” and “chemical” ordering is explored. A petrologic application showing the influence of magnetic ordering on temperatures derived from the Fe−Ti oxide geothermometer demonstrates that the effect is significant (a correction on the order of 100 °C) at derived temperatures below the Néel point for the cubic phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050083
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  • 8
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    Redox systematics of a magma ocean with variable pressure-temperature gradients and composition (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-07-09
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Presentation of the Dana Medal of the Mineralogical Society of America for 2015 to Marc Hirschmann (2015)
    Mineralogical Society of America
    Details
    Publication Date: 2015-05-13
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 10
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    Thermodynamics, self-diffusion, and structure of liquid NaAlSi3O8 to 30 GPa by classical molecular dynamics simulations (2016)
    Mineralogical Society of America
    Details
    Publication Date: 2016-09-02
    Description: Understanding the thermodynamics of liquid silicates at high pressure and temperature is essential for many petrologic problems, and sodium aluminosilicates are an important component of most magmatic systems. We provide a high-pressure equation of state (EOS) for liquid NaAlSi 3 O 8 based upon molecular dynamics (MD) simulations. The resulting thermodynamic properties have changes in pressure and temperature correlative to trends in diffusion and atomic structure, giving insight to the connections between macroscopic and microscopic properties. Internal pressure shows a maximum in attractive interatomic forces at low pressure, giving way to the dominance of repulsive forces at higher pressure. Self-diffusion coefficients ( D ) typically order D Na 〉 D Al 〉 D O 〉 D Si . At the lowest temperature, self-diffusivity (anomalously) increases as pressure increases up to ~5–6 GPa for Al, Si, and O. Diffusion data outside this "anomalous" region are fit by a modified Arrhenius expression, from which activation energies are calculated: 85 kJ/mol (Na) to 140 kJ/mol (Si). The amount of AlO 4 and SiO 4 polyhedra (tetrahedra) decreases upon compression and is approximately inversely correlated to the abundance of five- and sixfold structures. Average coordination numbers for Al-O, O-O, and Na-O polyhedra increase sharply at low pressure but start to stabilize at higher pressure, corresponding to changes in interatomic repulsion forces as measured by the internal pressure. High-pressure repulsion also correlates with a close-packed O-O structure where ~12 O atoms surround a central O. Self-diffusivity stabilizes at higher pressures as well. Relationships between the internal pressure, self-diffusion, and structural properties illustrate the link between thermodynamic, transport, and structural properties of liquid NaAlSi 3 O 8 at high pressure and temperature, shedding light on how microscopic structural changes influence macroscopic properties in molten aluminosilicates.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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