Correlation and prediction of thermodynamic properties of nonelectrolytes at infinite dilution in water over very wide temperature and pressure ranges (2000K and 10GPa)

Plyasunov, Andrey V.

doi:10.1016/j.gca.2015.07.012

Cited by 18 publications

(15 citation statements)

References 147 publications

(230 reference statements)

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“…However, caution is required because volumes of the fluid end-members have not been measured, other than for water, at pressures greater than a few tenths of a GPa, so the equations of state for fluid members other than H 2 O are extrapolated beyond the pressures at which they have been tested. However, the form of the corresponding states equation is suggested by Plyasunov (2015) to be valid to water densities around 1000 kg m −3 , i.e. to pressures of 2 GPa on subduction geotherms, and calculated fugacity coefficients are broadly consistent with those presented by Plyasunov (2015).…”

Section: Thermodynamic Modellingsupporting

confidence: 61%

“…However, the form of the corresponding states equation is suggested by Plyasunov (2015) to be valid to water densities around 1000 kg m −3 , i.e. to pressures of 2 GPa on subduction geotherms, and calculated fugacity coefficients are broadly consistent with those presented by Plyasunov (2015). The EOS are therefore considered semi-quantitative or better at the conditions of interest.…”

Section: Thermodynamic Modellingsupporting

confidence: 52%

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Effects of geodynamic setting on the redox state of fluids released by subducted mantle lithosphere

Evans

Reddy

Tomkins

et al. 2017

Lithos

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Magnetite breakdown during subduction of serpentinised ultramafic rocks may produce oxidised fluids that oxidise the deep Earth and/or the subarc mantle, either via direct transport of ferric iron, or via redox reactions between ferric iron and other elements, such as sulfur. However, so far, there is no consensus on the oxidation state of fluids released during subduction of ultramafic rocks, or the factors that control this oxidation state. Subducted samples from a magma-poor rifted margin and a supra-subduction zone geodynamic setting were compared to examine evidence of changes in opaque phase assemblage and ferric iron content as a consequence of subduction, and as a function of geodynamic setting. Thermodynamic calculations in the system Fe-Ni-O-H-S and Fe-Ni-O-S at the pressures and temperatures of interest were used to constrain oxygen activities and fluid compositions. Samples from New Caledonia, which exemplify supra-subduction zone mantle, contain awaruite (FeNi 3

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Section: Thermodynamic Modellingsupporting

confidence: 61%

Section: Thermodynamic Modellingsupporting

confidence: 52%

Effects of geodynamic setting on the redox state of fluids released by subducted mantle lithosphere

Evans

Reddy

Tomkins

et al. 2017

Lithos

View full text Add to dashboard Cite

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“…While the HKF model was developed using the physically sound Born solvation theory for charged species, it was subsequently extended to nonelectrolytes and neutral species as well (Shock et al, 1989). However, it has been demonstrated theoretically and using experimental data that the Born-type model is not really suitable for calculating and predicting thermodynamic properties of neutral species, especially at near-critical and supercritical conditions (Akinfiev and Diamond, 2003;Plyasunov, 2015;Plyasunov and Shock, 2001).…”

Section: Thermodynamics Of the Aqueous K + And Na + Ionsmentioning

confidence: 99%

Internally consistent thermodynamic data for aqueous species in the system Na–K–Al–Si–O–H–Cl

Miron

Wagner

Kulik

et al. 2016

Geochimica et Cosmochimica Acta

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A large amount of critically evaluated experimental data on mineral solubility, covering the entire Na-K-Al-Si-O-H-Cl system over wide ranges in temperature and pressure, was used to simultaneously refine the standard state Gibbs energies of aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers equation of state. The thermodynamic properties of the solubility-controlling minerals were adopted from the internally consistent dataset of Holland and Powell (2002; Thermocalc dataset ds55). The global optimization of Gibbs energies of aqueous species, performed with the GEMSFITS code (Miron et al., 2015), was set up in such a way that the association equilibria for ion pairs and complexes, independently derived from conductance and potentiometric data, are always maintained. This was achieved by introducing reaction constraints into the parameter optimization that adjust Gibbs energies of complexes by their respective Gibbs energy effects of reaction, whenever the Gibbs energies of reactant species (ions) are changed. The optimized thermodynamic dataset is reported with confidence intervals for all parameters evaluated by Monte Carlo trial calculations. The new thermodynamic dataset is shown to reproduce all available fluid-mineral phase equilibria and mineral solubility data with good accuracy and precision over wide ranges in temperature (25 to 800°C), pressure (1 bar to 5 kbar) and composition (salt concentrations up to 5 molal). The global data optimization process adopted in this study can be readily repeated any time when extensions to new chemical elements and species are needed, when new experimental data become available, or when a different aqueous activity model or equation of state should be used. This work serves as a proof of concept that our optimization strategy is feasible and successful in generating a thermodynamic dataset reproducing all fluidmineral and aqueous speciation equilibria in the Na-K-Al-Si-O-H-Cl system within their experimental uncertainties. The new dataset resolves the long-standing discrepancies between thermodynamic data of minerals and those of aqueous ions and complexes, by achieving an astonishing degree of consistency between a large number of fluid-mineral equilibrium data. All of this at the expense of changing the standard state properties of aqueous species, manly the Gibbs energy of formation. Using the same strategy, the core dataset for the system Na-K-Al-Si-O-H-Cl can be extended with additional rock-forming elements such as Ca, Mg, Fe, Mn, Ti, S, C, B. In future, the standard-state properties of minerals and aqueous species should be simultaneously optimized, to create the next-generation of fully internally consistent data for fluid-mineral equilibria. Although we employ the widely used HKF equations for this study, the same computational approach can be readily applied to any other speciation-based equation of state for multicomponent aqueous solutions.

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“…The HKF model (Tanger and Helgeson, 1988) developed for calculating standard chemical potentials of aqueous ions was empirically extended to calculation of the standard state properties of aqueous nonelectrolytes (Shock and others, 1989;Shock and Helgeson, 1990). However, experimental studies for the standard partial molar volume and heat capacity of aqueous nonelectrolyte solutions have convincingly demonstrated that the HKF model fails to correctly predict the standard state properties of nonelectrolytes close to the critical point of water (Plyasunov and Shock, 2001;Schulte and others, 2001;Akinfiev and Diamond, 2003;Plyasunov, 2015). Schulte and others (2001) and Plyasunov and Shock (2001) have revised the HKF parameters of CO2(aq) to better reproduce the recent measurements (Hnědkovský and Wood, 1997) of partial molal heat capacity and partial molal volume of CO2(aq).…”

Section: Carbon Dioxide Solubility In Watermentioning

confidence: 99%

An internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl to 800 °C and 5 kbar

et al. 2017

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This study presents an internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl, obtained by adding species of calcium, magnesium and carbon to the core system Na-K-Al-Si-O-H-Cl (Miron and others, 2016). Critically evaluated experimental data on mineral solubility (Ca and Mg hydroxides, Ca and Mg silicates, anorthite, Ca and Mg carbonates) in water and aqueous electrolyte solutions over wide ranges in temperature and pressure were added to the database of experimental data. The complete experimental dataset was then used to simultaneously refine the standard state Gibbs energies of all aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers (HKF) equation of state. The thermodynamic properties of the solubility-controlling minerals were accepted from the internally consistent dataset of Holland and Powell (1998; updated Thermocalc dataset ds55). The association equilibria of important hydroxide, chloride, carbonate and silicate complexes were critically reviewed, and their standard state properties and HKF parameters were independently derived from conductance, potentiometric and, in a few cases, solubility measurements. In a global optimization of standard Gibbs energies of aqueous species, performed with the GEMSFITS code (Miron and others, 2015), the association equilibria for aqueous complexes were always maintained. The new thermodynamic dataset reproduces all available fluid-mineral phase equilibria and mineral solubility data in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl with good accuracy over wide ranges in temperature (25 to 800°C), pressure (1 bar to 5 kbar) and composition (salt concentrations up to 5 molal). This makes it possible to perform geochemical and reactive transport modeling of processes in natural and engineered georeservoirs over wide ranges of conditions with an unprecedented level of accuracy and reliability and to address processes of fluid flow and fluid-rock interaction in the Earth's crust from a new perspective. Using the same strategy as applied in the present study, the internally consistent thermodynamic dataset can be further extended with additional major and trace elements, and the data refinement process can be repeated when new experimental data or nextgeneration equation of state or activity models for aqueous solutions become available.

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Correlation and prediction of thermodynamic properties of nonelectrolytes at infinite dilution in water over very wide temperature and pressure ranges (2000K and 10GPa)

Cited by 18 publications

References 147 publications

Effects of geodynamic setting on the redox state of fluids released by subducted mantle lithosphere

Effects of geodynamic setting on the redox state of fluids released by subducted mantle lithosphere

Internally consistent thermodynamic data for aqueous species in the system Na–K–Al–Si–O–H–Cl

An internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl to 800 °C and 5 kbar

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