Metamorphic Petrology GIBBS from Frank Spear. The Gibbs method is a procedure that computes changes in a set of dependent thermodynamic variables given

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, 639-650, 1996. 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. 775-784.

Garnet-Cordierite-Spinel-Sillimanite/Kyanite-Quartz thermobarometry from Geoff Nichols.

Software and Data for Thermodynamics and Phase Equilibrium Calculations in Geology

http://people.ucalgary.ca/~gordon/thermo_links.html

Equilibrium assemblage calculations: a comparison

Petrogenetic grids

AFM-diagramsGeothermo-barometry

PeudosectionsEquilibrium assemblage

diagrams

Theriak-Domino x XThermocalc X X X X

Perple–X X X X XGibbs X X X XTWQ X X



Equilibrium assemblage calculations: non-linear equations

Example: K2O, FeO, MgO, Al2O3, SiO2, H2O

6 components

Chl: clinochloreMg-amesiteFe-amesitedaphnite

Gr pyropealmandine

Bio phlogopiteanniteeastonitesiderophyllite

Qtz

H2O

Mus muscoviteMg-celadoniteFe-celadonite

Assume: stable assemblage15 species (unknown amounts)

9 independent reactions

Bulk composition:

SiO2 1.00283AlO0.5 0.40486MgO 0.04787FeO 0.07641KO0.5 0.07898HO0.5 0.86590

P

T

Equilibrium assemblage calculations: non-linear equations

Example: K2O, FeO, MgO, Al2O3, SiO2, H2O

6 components

Chl: clinochloreMg-amesiteFe-amesitedaphnite

Gr pyropealmandine

Bio phlogopiteanniteeastonitesiderophyllite

Qtz

H2O

Mus muscoviteMg-celadoniteFe-celadonite

Assume: stable assemblage15 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:

SiO2 1.00283AlO0.5 0.40486MgO 0.04787FeO 0.07641KO0.5 0.07898HO0.5 0.86590

Equilibrium assemblage calculations: G-minimization

X0.0 1.0

Gf

B

A1

C A2

Find minimum Gf assemblage

Bulk composition

D

E

Equilibrium assemblage calculations: G-minimization

X0.0 1.0

Gf

B

A1

C A2

Find minimum Gf assemblage

Bulk composition

XA

D

E

Petrogenetic grids

AFM-diagramsGeothermo-barometry

PeudosectionsEquilibrium assemblage

diagrams

Theriak-Domino x XThermocalc X X X X

Perple–X X X X XGibbs X X X XTWQ X X


Thermocalc

?

Perple_x

2m

Domino

3m

http://www.perplex.ethz.ch/perplex_thermocalc_comparison.html

SI(68.0)AL(24.976)MG(4.761)FE(10.529)K(7.638)H(100)O(?)


san san

+cord

Fig 5aky

FSP GARNET PHNG BIO STAU q H2O

+ H2O, q, pl

+ pg

+ c

hl+ s

t

+ Kfsp

FS

P G

AR

NE

T P

HN

G B

IO S

TA

U q + c

hl

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 L

iq Qtz

Grt Spr Opx Liq Qtz

Grt Opx Crd Liq Qtz

Grt Opx Sil Liq Qtz

Opx CrdLiq Qtz

without Feldspar

12m 50s

T(°C)

Grt Sil Liq Qtz

Grt Spr L

iq Qtz

Grt Spr Opx Liq QtzGrt Opx SilLiq Qtz

Fsp GrtSil LiqQtz

FspGrtOpx SilLiq Qtz

Fsp

Grt Spr O

px Liq Qtz

FspSpr Opx Liq Qtz

Fsp OpxCrd Liq Qtz

Fsp Grt

Opx Crd Liq Qtz

+mt

-Fsp

Fig. 6a

with Feldspar

Thermocalc Perple_X Theriak-Domino

source ofpossible errors: a) datab) diagram construction

databasesolution modelshuman errors

databasesolution modelsprogramming errors


time needed several hoursfew minutes+computing time

few minutes+computing time

quality of diagrams good quality varying quality good quality

for beginners:(using a standard database)

learning how to use hopeless reasonably easy reasonably easy

probability of success 0 10% 10%

advanced users

choice of database no several choices few choices

choice of solution models cut-and-paste predefined cut-and-paste

define new solution models difficult moderately easy easy

probability of success ? 30% 30%











learning how to use hopeless reasonably easy easy


advanced users




probability of success ? 30% 30%











learning how to use hopeless reasonably easy easy


advanced users




probability of success 30% 30% 30%


Dave Hirsch, Western Washington University and Julie Baldwin, University of Montana

http://serc.carleton.edu/research_education/equilibria/advancedmodeling.html

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





The critic


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.





The critic


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?

Documents

Metamorphic Petrology GIBBS from Frank Spear. The Gibbs method is a procedure that computes changes in a set of dependent thermodynamic variables given