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The dissolution rates of natural glasses as a function of their composition at pH 4 and 10.6, and temperatures from 25 to 74 degrees C. Geochimica Et Cosmochimica Acta
, 2004
"... AbstractFarfromequilibrium dissolution rates of a suite of volcanic glasses that range from basaltic to rhyolitic in composition were measured in mixed flow reactors at pH 4 and 10.6, and temperatures from 25 to 74°C. Experiments performed on glasses of similar composition suggest that dissoluti ..."
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AbstractFarfromequilibrium dissolution rates of a suite of volcanic glasses that range from basaltic to rhyolitic in composition were measured in mixed flow reactors at pH 4 and 10.6, and temperatures from 25 to 74°C. Experiments performed on glasses of similar composition suggest that dissolution rates are more closely proportional to geometric surface areas than their BET surface areas. Measured geometric surface area normalized dissolution rates (r ϩ,geo ) at 25°C were found to vary exponentially with the silica content of the glasses. For pH 4 solutions this relation is given by: and at pH 10.6 Ϯ 0.2 this relation is given by: These equations can be used to estimate lifetimes and metal release fluxes of natural glasses at farfromequilibrium conditions. The lifetime at pH 4 and 25°C of a 1 mm basaltic glass sphere is calculated to be 500 yr, whereas that of a 1 mm rhyolitic glass sphere is 4500 yr. Estimated nutrient release rates from natural glasses decrease exponentially with increasing silica content.
AN EQUATION OF STATE FOR SILICATE MELTS. IV. CALIBRATION OF A MULTICOMPONENT MIXING MODEL TO 40 GPa
"... ABSTRACT. Mixing relations for the “highpressure ” parameters of the equation of state of Ghiorso (2004a) are developed and compositional coefficients are optimized to permit calculation of melt density in portions of the system SiO2TiO2Al2O3FeOMgOCaONa2OK2O to pressures in excess of 40 GPa ..."
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ABSTRACT. Mixing relations for the “highpressure ” parameters of the equation of state of Ghiorso (2004a) are developed and compositional coefficients are optimized to permit calculation of melt density in portions of the system SiO2TiO2Al2O3FeOMgOCaONa2OK2O to pressures in excess of 40 GPa and temperatures up to 2500°C. Four data sets are analyzed and fitted to yield an internally consistent model: (1) density estimates made from measurements of the sinking/floating of reference mineral markers in silicate liquids at known temperatures and pressures, (2) density estimates obtained from shock compression studies on molten liquids, (3) liquid densities inferred from the temperature and pressure dependence of the slopes of mineral fusion curves, and (4) estimates of densities of molten silicate liquids obtained by molecular dynamics simulations. Calibration compositions include chemically complex liquids (komatiite, peridotite and MORB bulk compostions) as well as simple liquids with minerallike stoichiometry. The model recovers density with an average error of 2 percent. The model is limited by not including the effects of volatiles or oxidized iron at elevated pressure.
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"... ran ar a, * a b a possible cooperative behavior. The equation of state and variation of internal energy with T and V are used in Part II (Ghiorso ponent silicates relevant to geochemical and geodynamical tively unpolymerized melts such as Mg2SiO4 and MgSiO3 have been studied in some detail in order ..."
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ran ar a, * a b a possible cooperative behavior. The equation of state and variation of internal energy with T and V are used in Part II (Ghiorso ponent silicates relevant to geochemical and geodynamical tively unpolymerized melts such as Mg2SiO4 and MgSiO3 have been studied in some detail in order to construct of equations of state and transport property relations (e.g.,
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"... die an ns b Ave dies, orm 1 Dynamics computations where performed utilizing the variation is often addressed by formulating a model with parameters that characterize the internal structural state of the material, and the equilibrium configuration is determined for specified T and P by computation o ..."
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die an ns b Ave dies, orm 1 Dynamics computations where performed utilizing the variation is often addressed by formulating a model with parameters that characterize the internal structural state of the material, and the equilibrium configuration is determined for specified T and P by computation of homoge