What is MC_fit?

• It is a Perple_X [Connolly2009] computer program based on the algorithm of Khan et al. [Khan2021] for inverting natural and experimental phase equilibria for thermobarometric conditions (Slides 19-22) and/or unknown thermodynamic parameters (Slides 23-25, [Pitsch2025]).

• It works by finding the best match between observations and a thermodynamic model of the observations predicted by free energy minimization as a function of any unknown parameters (aka, the inversion parameters).

• It can propagate both analytical and thermodynamic parameter uncertainties to estimate the uncertainty of the inversion parameters.

• It does not require complete compositional information; it can invert for unmeasured properties such as ferric-ferrous ratio and volatile content.

• It can incorporate, but does not require, knowledge of the bulk composition of the system and/or information on phase proportions.