MagMin_PT: An Excel-based mineral classification and geothermobarometry program for magmatic rocks

Abstract

Igneous rock forming minerals carry valuable information from the deep earth that is not directly accessible to the surface. Each phase represents physico-chemical conditions under which various magmatic processes occur at a wide range of depths from upper mantle to shallow crustal levels. These processes are cryptically inscribed in the whole-rock and mineral chemistry (e.g. major elements, trace elements, isotopic ratios) and the mineral textures (equilibrium vs. disequilibrium features), and intensive variables (e.g. pressure, P; temperature, T) as well. Therefore, special attention should be given to igneous minerals to better understand processes operated in their journey from source through magma chamber and conduit system to the earth surface. MagMin_PT is an Excel© based user-friendly program, designed to calculate mineral formulae and end-members, and to estimate pressure and temperature (e.g. geothermobarometry) from electron microprobe (EPMA) data, from magmatic rocks. The program operates the most common igneous rock-forming minerals (e.g. olivine, pyroxene, amphibole, biotite, feldspar, magnetite, ilmenite, apatite and zircon), resulting in various classification diagrams and P-T plots. Whole-rock or glass composition needs to be entered together with EPMA data into the program to check equilibration status in most P-T calculation models. Fe2+ and Fe3+ estimation is routinely performed in MagMin_PT based on the stoichiometric constrains, and machine learning method to some extent for different iron-bearing minerals. MagMin_PT is also able to carry out further calculations including fugacity, magmatic water content and saturation-temperature which are useful for igneous petrology studies. Graphical and numerical output produced by the program can be easily copied to further process in another media.