Metamorphic Petrology GIBBS from Frank Spear. The Gibbs method is a procedure that computes changes in a set of dependent thermodynamic variables given the changes in a set of independent thermodynamic variables. The thermodynamic variables are the derivatives of T (temperature), P (pressure), X (composition) and, if desired, M (the number of moles of a phase in an assemblage). For Macintosh. TWQ Web page. Rob Berman's thermobarometry program, data base, and activity calculations. For DOS. Software for calculating the volume and fugacity of CO2 at specified P and T using the Mäder and Berman (1991) equation of state. Cambridge Earth Sciences Software or THERMOCALC Web page. Tim Holland's and Roger Powell's THERMOCALC program and data base, activity calculations and more. Versions for Macintosh and DOS. Includes a variety of activity models. Dave Waters at Oxford is building a useful Tutorial on Mineral Thermobarometry based on this software. BAYES homepage Bayes is an internally consistent thermodynamic dataset and an interactive program to generate petrological phase diagrams. Internally consistent data set for rock-froming minerals from Matthias Gottschalk at GFZ Potsdam. Based on iterative evaluation of 1/T - lnKred plots. THERIAC-DOMINO and related programs. Web page from Christian de Capitani. Calculation of equilibrium assemblages, thermodynamic properties, and various types of phase diagram.Uses the TWQ data base. Fortran source. WEBINVEQ Terry Gordon's experimental Web system for performing thermobarometry calculations over the Web. Currently uses the TWQ 1.02 data base. PERPLEX Web page. Jamie Connolly's Fortran programs for calculating and displaying petrologic phase equilibria. Source and binaries for many platforms. EQMIN. A Microsoft® Excel© spread sheet to perform thermodynamic calculations. J.D. Martin. Computers and Geosciences, v. 22, , Available by ftp. GPT An Excel Spreadsheet for thermobarometric calculations in metapelitic rocks. 905K in sea.hqx (Mac) format. J.Reche & F.J. Martinez. Described in Computers & Geosciences Vol.22, No. 7, pp Garnet-Cordierite-Spinel-Sillimanite/Kyanite-Quartz thermobarometry from Geoff Nichols. Software and Data for Thermodynamics and Phase Equilibrium Calculations in Geology Equilibrium assemblage calculations: a comparison

Petrogenetic grids AFM-diagrams Geothermo- barometry Peudosections Equilibrium assemblage diagrams Theriak-Domino x X Thermocalc XXXX Perple–X XXXX Gibbs XXXX TWQ XX Equilibrium assemblage calculations: a comparison

Equilibrium assemblage calculations: non-linear equations Example: K 2 O, FeO, MgO, Al 2 O 3, SiO 2, H 2 O 6 components Chl:clinochlore Mg-amesite Fe-amesite daphnite Grpyrope almandine Biophlogopite annite eastonite siderophyllite Qtz H2OH2O Musmuscovite Mg-celadonite Fe-celadonite Assume:stable assemblage 15 species (unknown amounts) 9 independent reactions Bulk composition: SiO AlO MgO FeO KO HO P T

Equilibrium assemblage calculations: non-linear equations Example: K 2 O, FeO, MgO, Al 2 O 3, SiO 2, H 2 O 6 components Chl:clinochlore Mg-amesite Fe-amesite daphnite Grpyrope almandine Biophlogopite annite eastonite siderophyllite Qtz H2OH2O Musmuscovite Mg-celadonite Fe-celadonite Assume:stable assemblage 15 species (unknown amounts) 9 independent reactions At equilibrium: all reactions ∆G=0 9 equations 6 mass balance equations Search P,T for n(Gr)=0 Search P,T for n(Chl)=0 P T Bulk composition: SiO AlO MgO FeO KO HO

Equilibrium assemblage calculations: G-minimization X GfGf B A1A1 C A2A2 Find minimum G f assemblage Bulk composition D E

Equilibrium assemblage calculations: G-minimization X GfGf B A1A1 C A2A2 Find minimum G f assemblage Bulk composition XAXA D E

Petrogenetic grids AFM-diagrams Geothermo- barometry Peudosections Equilibrium assemblage diagrams Theriak-Domino x X Thermocalc XXXX Perple–X XXXX Gibbs XXXX TWQ XX Equilibrium assemblage calculations: a comparison

Thermocalc ? Perple_x 2m Domino 3m SI(68.0)AL(24.976)MG(4.761)FE(10.529)K(7.638)H(100)O(?) Equilibrium assemblage calculations: a comparison san

+cord Fig 5a ky

FSP GARNET PHNG BIO STAU q H2O + H 2 O, q, pl + pg + chl + st + Kfsp FSP GARNET PHNG BIO STAU q + chl Fig. 4. T–MH2O pseudosections for (a) the Permian bulk composition and (b) the Eo- Alpine bulk composition. On both diagrams the MH2O axis is labelled in mol.% H2O in the bulk rock; the thick solid line marks the water saturation line and the thick dashed line is the solidus. Mode contours for staurolite (abbreviated with st) are shown in the st-bearing fields. (a) The diagram for the Permian prograde path at 6.5 kbar. This diagram is a section along the thick line shown in Fig. 3(a) at 6.5 kbar. However, note that maximum water mode used here is not sufficient to saturate the entire diagram with water. Thus, there are minor differences to Fig. 3(a) at very high and very low temperatures. The thick shaded arrow marks the prograde path suggested for the Permian evolution of the Plattengneiss.

9m 15s Fig. 6a T(°C) Grt Sil Liq Qtz Grt Spr Liq Qtz Grt Spr Opx Liq Qtz Grt Opx Crd Liq Qtz Grt Opx Sil Liq Qtz Opx Crd Liq Qtz without Feldspar

12m 50s T(°C) Grt Sil Liq Qtz Grt Spr Liq Qtz Grt Spr Opx Liq Qtz Grt Opx Sil Liq Qtz Fsp Grt Sil Liq Qtz Fsp Grt Opx Sil Liq Qtz Fsp Grt Spr Opx Liq Qtz Fsp Spr Opx Liq Qtz Fsp Opx Crd Liq Qtz Fsp Grt Opx Crd Liq Qtz +mt -Fsp Fig. 6a with Feldspar

ThermocalcPerple_XTheriak-Domino source of possible errors: a) data b) diagram construction database solution models human errors database solution models programming errors database solution models programming errors time neededseveral hours few minutes +computing time few minutes +computing time quality of diagramsgood qualityvarying qualitygood quality for beginners: (using a standard database) learning how to usehopelessreasonably easy probability of success010% advanced users choice of databasenoseveral choicesfew choices choice of solution modelscut-and-pastepredefinedcut-and-paste define new solution modelsdifficultmoderately easyeasy probability of success?30% Equilibrium assemblage calculations: a comparison

ThermocalcPerple_XTheriak-Domino source of possible errors: a) data b) diagram construction database solution models human errors database solution models programming errors database solution models programming errors time neededseveral hours few minutes +computing time few minutes +computing time quality of diagramsgood qualityvarying qualitygood quality for beginners: (using a standard database) learning how to usehopelessreasonably easyeasy probability of success010% advanced users choice of databasenoseveral choicesfew choices choice of solution modelscut-and-pastepredefinedcut-and-paste define new solution modelsdifficultmoderately easyeasy probability of success?30% Equilibrium assemblage calculations: a comparison

ThermocalcPerple_XTheriak-Domino source of possible errors: a) data b) diagram construction database solution models human errors database solution models programming errors database solution models programming errors time neededseveral hours few minutes +computing time few minutes +computing time quality of diagramsgood qualityvarying qualitygood quality for beginners: (using a standard database) learning how to usehopelessreasonably easyeasy probability of success010% advanced users choice of databasenoseveral choicesfew choices choice of solution modelscut-and-pastepredefinedcut-and-paste define new solution modelsdifficultmoderately easyeasy probability of success30% Equilibrium assemblage calculations: a comparison

Dave Hirsch, Western Washington University and Julie Baldwin, University of Montana Perple_X Disadvantages Perplex's ease of use can also be a pedagogical drawback, in that students are apt to run the program without a deep consideration of their actions and choices. Perplex's methods of computation (calculation on a grid, division of solutions into discrete pseudocompounds) typically introduces small artifacts (akin to pixelization in an image) and may fail to identify features that are in close proximity to each other, leading to portions of diagrams that sometimes violate the Phase Rule. In the addition, the process of excluding phases and choosing solution models can be confusing for students and mistakes in this step can produce meaningless diagrams. Finally, Perplex is unable at this time to incorporate the 'equipartition constraint' used in some activity models by THERMOCALC. The critic Equilibrium assemblage calculations: a comparison

Dave Hirsch, Western Washington University and Julie Baldwin, University of Montana Perple_X Disadvantages Perplex's ease of use can also be a pedagogical drawback, in that students are apt to run the program without a deep consideration of their actions and choices. Perplex's methods of computation (calculation on a grid, division of solutions into discrete pseudocompounds) typically introduces small artifacts (akin to pixelization in an image) and may fail to identify features that are in close proximity to each other, leading to portions of diagrams that sometimes violate the Phase Rule. In the addition, the process of excluding phases and choosing solution models can be confusing for students and mistakes in this step can produce meaningless diagrams. Finally, Perplex is unable at this time to incorporate the 'equipartition constraint' used in some activity models by THERMOCALC. The critic Equilibrium assemblage calculations: a comparison Perplex's ease of use can also be a pedagogical drawback, in that students are apt to run the program without a deep consideration of their actions and choices.

Dave Hirsch, Western Washington University and Julie Baldwin, University of Montana Perple_X Disadvantages Perplex's ease of use can also be a pedagogical drawback, in that students are apt to run the program without a deep consideration of their actions and choices. Perplex's methods of computation (calculation on a grid, division of solutions into discrete pseudocompounds) typically introduces small artifacts (akin to pixelization in an image) and may fail to identify features that are in close proximity to each other, leading to portions of diagrams that sometimes violate the Phase Rule. In the addition, the process of excluding phases and choosing solution models can be confusing for students and mistakes in this step can produce meaningless diagrams. Finally, Perplex is unable at this time to incorporate the 'equipartition constraint' used in some activity models by THERMOCALC. The critic Equilibrium assemblage calculations: a comparison In the addition, the process of excluding phases and choosing solution models can be confusing for students and mistakes in this step can produce meaningless diagrams.

Perplex's ease of use can also be a pedagogical drawback, in that students are apt to run the program without a deep consideration of their actions and choices. In the addition, the process of excluding phases and choosing solution models can be confusing for students and mistakes in this step can produce meaningless diagrams. Is ease of use a drawback? Is selection of phases and solution models a capital sin?