Computational Thermodynamics (CT) Server

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Computational Thermodynamics Server

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What does this applet do?

This applet is a pre-alpha release GUI prototype of a user configurable geothermometer. Once completed. theapplet will permit on-the-fly creation of mineral geothermometers by allowing the user to select among internally consistent thermodynamic models for phases, mixing and matching endmembers, until univariant reactions are constructed that permit temperature to be estimated from specified phase compositions and pressure.  Because exchange equilibria are constructed from an internally consistent set of endmember and solid solution thermodynamic properties, any appropriate combination of phase-components may be used to obtain a temperature estimate.  For example, if high-calcium clinopyroxene and chromium-rich spinel are thought to have formed under equilibrium conditions, the user may construct a geothermometer involving Fe2+-Mg exchange equilibria: FeCr2O4 (spn) + CaMgSi2O6 (pyx) = MgCr2O4 (spn) + CaFeSi2O6 (pyx).  Upon inputting compositions of the coexisting spinel and clinopyroxene and a pressure estimate, chemical potentials of endmember components are calculated using the thermodynamic models of Sack and Ghiorso (1991b; 1994c), allowing temperature to vary until the Gibbs free energy of exchange reaction is zeroed.  Our intention is to make this generic geothermometer applet fully functional, providing access to the entire suite of internally consistent solid phase thermodynamic models in the MELTS database (Elkins and Grove, 1990; Ghiorso, 1990; 1997; Ghiorso and Evans, 2002; Ghiorso et al., 1995; Hirschmann and Ghiorso, 1994; Sack and Ghiorso, 1989; 1991a,b; 1994a,b,c; 1998;).  In addition, the newly calibrated Fe-Ti oxide geothermometer/oxybarometer of Ghiorso and Evans will be distributed as part of this applet.  We anticipate that usage will demand a user interface for this applet that allows selection of standardized geothermometer options.  We also anticipate that suitable combinations of exchange equilibria could be constructed that would permit simultaneous estimation of both temperature and pressure, or alternately, a single exchange equilibria could be used for geobarometry given an estimate of temperature.  The alpha-release of this software is anticipated for late-Fall of 2007.

Source code and technical documentation

No documentation or source code materials available until the alpha-release.

References for the geothermometer applet

Thermodynamic properties of phases are calculate from the following published models:

  • Evans BW, Ghiorso MS (1995) Thermodynamics and Petrology of Cummingtonite. Amer Mineral 80, 649-663
  • Evans BW, Ghiorso MS, Kuehner SM (2000) Thermodynamic properties of tremolite: a correction and some comments. American Mineralogist 85 466-472
  • Evans BW, Ghiorso MS, Yang H, Medenbach O (2001) Thermodynamics of the amphiboles: Anthophyllite-ferroanthophyllite and the ortho-clino phase loop. American Mineralogist 86, 640-651
  • Ghiorso MS (1997) Thermodynamic analyses of the effect of magnetic ordering on miscibility gaps in the Fe-Ti cubic and rhombohedral oxide minerals and the Fe-Ti oxide geothermometer. Physics and Chem Minerals 25, 28-38
  • Ghiorso MS, Evans BW (2002) Thermodynamics of the Amphiboles: Ca-Mg-Fe2+ quadrilateral. American Mineralogist 87, 79-98
  • Ghiorso MS, Evans BW, Hirschmann MM, Yang H (1995) Thermodynamics of the Amphiboles: I. (Fe2+,Mg) Cummingtonite Solid Solutions. Amer Mineral 80, 502-519
  • Ghiorso MS, Yang H., Hazen RM (1999) Thermodynamics of cation ordering in Karrooite (MgTi2O5). American Mineralogist 84, 1370-1374
  • Ghiorso, MS (1990) Thermodynamic properties of hematite-ilmenite-geikielite solid solu­tions. Contrib Mineral Petrol 104, 645-667
  • Ghiorso, MS, Sack, RO (1991) Fe-Ti oxide geothermometry: Thermodynamic formulation and the estimation of intensive variables in silicic magmas. Contrib Mineral Petrol 108, 485-510
  • Sack RO, Ghiorso MS (1989) Importance of considerations of mixing properties in estab­lishing an internally consistent database: Thermochemistry of minerals in the system Mg2SiO4-Fe2SiO4-SiO2. Contrib Mineral Petrol 102, 41-68
  • Sack RO, Ghiorso MS (1994) Thermodynamics of multicomponent pyroxenes: I. Formulation of a general model. Contrib Mineral Petrol  116, 277-286
  • Sack RO, Ghiorso MS (1994) Thermodynamics of multicomponent pyroxenes: II. Phase relations in the quadrilateral. Contrib Mineral Petrol  116, 287-300
  • Sack RO, Ghiorso MS (1994) Thermodynamics of multicomponent pyroxenes: III. Calibration of Fe2+(Mg)-1, TiAl(MgSi)-1, TiFe3+(MgSi)-1, AlFe3+(MgSi)-1, NaAl(CaMg)-1, Al2(MgSi)-1 and Ca(Mg)-1 exchange reactions between pyroxenes and silicate melts. Contrib Mineral Petrol 118, 271-296
  • Sack RO, Ghiorso MS (1998) Thermodynamics of feldspathoid solutions. Contrib Mineral Petrology  130, 256-274
  • Sack, RO, Ghiorso, MS (1991) An internally consistent model for the thermodynamic properties of Fe-Mg-titanomagnetite-aluminate spinels. Contrib Mineral Petrol 106, 474-505
  • Sack, RO, Ghiorso, MS (1991) Chromian spinels as petrogenetic indicators: thermody­namics and petrological applications. Am Mineral 76, 827-847

 

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