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Kirschen, Marcus ; De Capitani, Christian ; Pichavant, Michel:
Determination of non-ideal solution parameters of hydrous melts from phase equilibria in the system Ab-Or-Qtz-H2O.
1999
Veranstaltung: European Union of Geosciences (EUG10) Meeting
, 28. März - 1. April 1999
, Strasbourg.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Paper
)
Abstract
The computation of equilibrium phase diagrams of hydrous silicate systems requires a model of the Gibbs free energy of the melt defining the activity of the solution end-members at given composition, pressure, temperature. There is limited experimental indication showing that Henry's law is obeyed for volatile components like H2O and CO2. Extension to more complex systems was made assuming ideal mixing of the melt species normalized to 8 oxygens (Burnham & Nekvasil 1986). Recent developments include water speciation (e.g. Stolper 1989), higher order excess polynomials (e.g. Blencoe 1992) and non-ideal solution parameters between melt species including water (Ghiorso 1995). Systematic data have been obtained on the effect of water on solid-liquid equilibria and the effect of composition, pressure and temperature on water solubility in the system Ab-Or-Qtz-H2O (e.g. Holtz et al. 1995). Therefore it seems appropriate to use this system (1) to test existing solution models and (2) to develop thermodynamic modelling of hydrous melts.
Non-ideal solution parameters for the silicate liquid were derived simultaneously from liquidus and solubility data using mathematical programming techniques (e.g. Murtagh & Saunders 1987). For this purpose a Fortran program was written that converts experimental liquidus (and solvus) data to linear constraints of the optimization problem using bracketing relations drG <> 0. The use of a highly symbolic input code of experimental results improves significantly the transparency of the optimization problem. The linear problem is changed to a linearly constrained optimization when constraints from solubility and/or activity measurements are available. Margules-type polynomials were used to fit the excess free energy of the hydrous melt as a first approach. Predictions of existing solution models will be compared with results from this study.
Weitere Angaben
| Publikationsform: | Veranstaltungsbeitrag (Paper) |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Ingenieurwissenschaften Forschungseinrichtungen > Institute in Verbindung mit der Universität > Fraunhofer-Zentrum für Hochtemperatur-Leichtbau (HTL) Fakultäten Forschungseinrichtungen Forschungseinrichtungen > Institute in Verbindung mit der Universität |
| Titel an der UBT entstanden: | Nein |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 530 Physik 500 Naturwissenschaften und Mathematik > 540 Chemie 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie |
| Eingestellt am: | 03 Jul 2019 07:36 |
| Letzte Änderung: | 03 Jul 2019 07:36 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/49792 |