Compatibility diagrams involve the projection of composition space for a rock into two dimensions, with the bulk composition being shown in relation to the compositions of phases in stable equilibria at the (P, T) of interest.
THERMOCALC produces output to allow the user to plot compatibility triangles directly. This is best explored through Simon Schorn’s tutorial, part 2 of a series that links compatibility diagrams with P-T projections and pseudosections:
To follow this tutorial, you should download your own copy of THERMOCALC 3.50 (tc350beta or tc350; Dec 2020 or later) from the THERMOCALC download page, and a copy of DRAWPD version 1.16 or above from the DRAWPD download page.
Alternatively, you can find an example scriptfile here: