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Internally-consistent thermochemical parameters for the hydrous melt in the system CaAl2Si2O8–NaAlSi3O8–KAlSi3O8–SiO2–H2O

Title data

Kirschen, Marcus ; Pichavant, Michel:
Internally-consistent thermochemical parameters for the hydrous melt in the system CaAl2Si2O8–NaAlSi3O8–KAlSi3O8–SiO2–H2O.
Event: 78. Jahrestagung der Deutschen Mineralogischen Gesellschaft , 24.-29. September 2000 , Heidelberg.
(Conference item: Conference , Poster )

Abstract in another language

The computation of phase equilibrium diagrams of hydrous silicate systems requires a model of the Gibbs free energy of the melt defining the activity of all solution end-members at given composition, pressure, and temperature. Here we present a set of internally consistent thermochemical parameters for the hydrous melt in the five-component system CaAl2Si2O8 - NaAlSi3O8 - KAlSi3O8 - Si4O8 - H2O and its subsystems. Model parameters of the melt were fitted to ca. 850 experimental liquidus and H2O solubility constraints from the literature using mathematical programming techniques and the crystalline and fluid phases as a reference. The Elkins & Grove mixing model [1] and the Haar equation of state [2] were applied for the feldspars and the fluid, respectively. H2O solubility of the feldspars was neglected. Standard state enthalpies and entropies of the solution end-members were bounded to data from [3]; thermal expansion parameters were taken from [4]. Non-ideality of the dry and hydrous melts was approximated with three-parameter Margules excess polynomials for the ten pseudo-binary systems and a Kohler-type extrapolation scheme to the higher order systems [5]. No additional ternary or quaternary excess parameters were required. Using previously unpublished liquidus data near the 5% anorthite composition plane we tested the extrapolation capacity of a solution model fitted to the haplogranite system [6]. A standard state enthalpy and entropy of approximately -290 kJ/mol and 68.4 J/Kmol were obtained for the H2O melt component.

Further data

Item Type: Conference item (Poster)
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Research Institutions > Affiliated Institutes > Fraunhofer Center for High Temperature Materials and Design (HTL)
Result of work at the UBT: No
DDC Subjects: 500 Science > 550 Earth sciences, geology
Date Deposited: 03 Jul 2019 07:16
Last Modified: 03 Jul 2019 07:16
URI: https://eref.uni-bayreuth.de/id/eprint/49549