![]() Referencesĭe Capitani & Petrakakis (2010) Am Mineral 95 1006-1016. In Perple_X, precise comparison with THERMOCALC is limited since the software digitises the Gibbs energy surfaces rather than solving the equilibrium equations exactly. Any differences are liable to vary with the chemical system and phases present. Although for recent families of HP x-eos – those of Green et al (2016) and Holland et al (2018) – there has been an effort to achieve near- equivalence between THERMOCALC and Perple_X, there is in general no guarantee that the dataset or HPx-eos are implemented correctly outside THERMOCALC. In effect, therefore, THERMOCALC’s implementation defines the correct version of these models – overriding any typos in the papers where they are published!īoth the Holland & Powell dataset and the HP x-eos have been implemented in a variety of other software, in particular Perple_X (Connolly, 2005) and Theriak/Domino (de Capitani & Petrakakis, 2010). THERMOCALC is the primary tool for calibrating the HP x-eos, including the underlying Holland & Powell dataset. THERMOCALC as the definitive HP x-eos implementation Developing co-functionality with the ENKI environment (via Jupyter workbooks).Making some uncertainty-estimation tools available to users.Expanding the options for applying multiple-reaction thermobarometry, and making this more user-friendly.Facilitating open-system calculations, a step towards developing integrated simulations of open-system Earth processes.csv output that can be read by external applications such as Excel, in order to facilitate manipulation and plotting of output. give access to the more of the calculated thermodynamic properties of phases and assemblages.Recent and imminent changes to the user’s experience are aimed at: ![]() THERMOCALC is evolving rapidly at present. Over the next twenty years the solution models, now for both solid solutions and fluids, expanded drastically in complexity, becoming today’s HP x-eos. Powell, Holland & Worley (1998) used THERMOCALC to calculate phase diagrams at fixed bulk composition, modelling the thermodynamics of solid solutions as if they underwent ideal mixing-on-sites. ![]() For this purpose, the analysed compositions of minerals in a presumed equilibrium were converted into activities via simple activity-composition relations.Ĭompatibility triangles for metapelites calculated with THERMOCALC This made it a powerful tool for optimal thermobarometry (Powell & Holland, 1988, 1994), a multiple-reaction approach to thermobarometry that formally accounts for correlated uncertainties in the input. At first the program was primarily intended to calculate equilibrium among pure end-members, or impure end-members at fixed activity. Details of its operation were first published in Powell & Holland (1988). Roger Powell began to write THERMOCALC (unrelated to the commercial software, Thermo-Calc) in the early 1970s, initially as part of his PhD research, and later through his collaboration with Tim Holland on what was to become the Holland & Powell dataset. The user then hopes to gain insight into the rock’s history by comparing the predictions with petrographic observations and perhaps analysis of phase compositions. The aim is to predict what mineral and fluids would coexist in the rock if the rock were subjected to a range of pressures and temperatures. The most common use of THERMOCALC is to calculate stable phase diagrams at constrained bulk composition, using a bulk composition derived from a rock sample.
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