MAGEMin, a new and efficient Gibbs free energy minimizer: application to igneous systems

Modelling stable mineral assemblage is crucial to calculate mineral stability relations in the Earth’s lithosphere e.g., to estimate thermobarometric conditions of exposed rocks and to quantify the fraction and composition of magma during partial melting. Accurate prediction models of stable phase are also fundamental to model trace element partitioning and to extract essential physical properties such as, fluid/melt/rock densities, heat capacity and seismic velocities. This thus forms a crucial step in linking geophysical observations with petrological constraints.

Here, we present a new Mineral Assemblage Gibbs free Energy Minimizer (MAGEMin). The package has been developed with the objective to provide a minimization routine that is easily callable and fulfilling several objectives. Firstly, the package aims to consistently compute for single point calculations at given pressure, temperature and bulk-rock composition with no needed a priori knowledge of the system. Secondly, the package has been developed for stability, performance and scalability in complex chemical systems. Finally, the code is fully parallel and we directly translate THERMOCALC formulation of solution models which yields easier and faster updates, less prone to implementation mistakes.

As a proof of concept we apply our new approach to the thermodynamic dataset for igneous systems of Holland et al. (2018). The database works in the NCKFMASHTOCr chemical system and has been updated to account for the new plagioclase model Holland et al. (2021).