Quick-Guide to THERIAK-DOMINO

Metamorphic petrology
Tutorial
A few simple steps to generate metamorphic phase equilibria diagrams
Author

Tobias Stephan

Published

November 29, 2025

This blog post gives a brief and most simple walk-through for THERIAK-DOMINO to generate some phase equilibria diagrams (pseudosections) modeled from the composition of metamorphic rocks.

A: Calculate phases / isopleths

  1. We need to define the chemical composition within a preferred chemical system relevant for the metamorphic reactions. In the therin.txt file, you need to add these compositions following the following structure to the end of the file:
500     4000 
0 SI(111.8429)AL(31.9729)FE(7.7807)MG(6.1284)MN(0.0846)CA(2.8175)NA(11.4878)K(6.3272)TI(0.6887)H(80)O(?) * HT-9 MnNCKFMASHT

Here, the first line gives the expected temperature (in °C) and pressure (kbar) for the modeling, and the second line specifies the concentrations of the elements relevant for our metamorphism.

To generate this line from your geochemical data, you may use my Bulk to therin app

  • Go to Bulk_to_therin and upload your major element composition (wt. %).

  • Select your desired chemical system and other optional parameters.

  • Copy the result under THERIN (mol) and paste it at the end of your therin.txt file.

  1. Next run start.bat file in the Working subfolder of your Theriak-Domino directory. Then type
domino

  1. data base definition: Select database for the modelling (e.g. tcds55_p07.txt)

  2. definition of X-axis: Define X-axis and its range (TC for Temperature (in ° Celsius), and then two numbers indicating the minimum and maximum temperature):

TC 300 800
  1. definition of X-axis: Define Y-axis and its range (P for pressure followed by the minimum maximum pressure in kbar):
P 1000 7000

  1. definition of calculation type: Type . for equilibrium phase diagram (eq) or jump to part B for mineral composition isopleth

  2. labeling of reactions, precision and smoothness: type 1 for assemblages

CALCULATION STARTS

B: (Optional): Calculate phases AND isopleths

  1. For eq and isopleths of phase compositions (e.g. garnet), follow steps up to 3. and type: script

  2. New JOB filename: domjob.bat

  3. script name for eq diagram: script_001_eq

  4. Follow steps described in A3 - A7

  5. Almandine file name script_002_alm

  6. Follow steps described in B4 - B8. Define the calculation type. The input must follow this structure: phase key nr min max step.

  • phase must be a mineral phase from the database (GT07W2 for garnet data in the database tcds55_p07.txt)

  • nr is 1

  • key is an end-member of that mineral phase (e.g. alm for almandine, gr for grossular, py pyrope, spss spessartine) as defined in the database file for that phase

  • min, max and step specify the range and the step-size for which isopleths the compositions should be calculated for (0 1 0.02` means from 0 to 100% in 2% steps.)

GT07W2 alm 1 0 1 0.02

  1. To label the reactions, type: 1

  2. Repeat steps 3-7 for additional garnet phases.

For example:

GT07W2 alm 1 0.5 0.8 0.01 
GT07W2 py 1 0.01 0.05 0.01 
GT07W2 gr 1 0.2 0.5 0.01 
GT07W2 spss 1 0.05 0.3 0.01
  1. Final database definition

end

  1. To start the scripts type and run domjob

C: Export mineral reactions as table and plot

Next, we have to clean up the labels of the reactions lines and then plot a phase diagram. Therefore, we run the two routines GUZZLER and EXPLOT (GUZZLER: cleans the labels, while EXPLOT, creates the plot and saves it in the plot.ps file).

In the command shell type and run the following functions in this sequence:

  1. guzzler
    • Enter input name. Usually you can just hit ENTER here, unless your specified a script. In that case you may check all the different *.plt file in your working directory and repeat all this steps for each file.
    • Specify the extent of the X-axis (temperature): min and max values (can be the ones specified earlier in domino, followed by a width value, e.g. 15)
    • Specify the extent of the Y-axis (pressure) min and max values (can be the ones specified earlier in domino, followed by a height value, e.g. 15)
    • Specify the size of the labels: 0.2
    • Specify if you want to label the plot: 3 (means YES)
  2. explot
    • Enter output name: Same as above, but now for all *.cln files in your working directory.

Now make a copy of the generated .ps or .svg file and repeat the same procedure, but this time we create a plot without labels (so you have a look-up file and a clean plot for further editing).

  1. Type and execute guzzler: Specify if you want to label the plot: 0 (means No)

  2. Type and execute explot

Finally generated the phase diagrams as a postscript file (*.ps) and *.svg, which you can further edit with vector graphics software, such as the free inkscape program.

D: Quickly search the reaction table for mineral phases

If you open the postscript file, you will see a complicated equilibrium phase diagram with some reactions numbered instead of labeled (because there is not enough room for labels.) To see a list of reactions and numbers, open the file table (created by GUZZLER) in the Working folder.

To quickly find the reaction belonging to a number, you may use my GUZZLER Filter app:

  1. Go to https://tobiste.shinyapps.io/Bulk_to_therin/

  2. Open the GUZZLER Filter tab

  3. Upload your reaction table (table)

  4. Type in the mineral of interest to see in which reaction lines the mineral is involved.

Additional ressources