PHASE EQUILIBRIUM MODELLING: APPROACHES AND PITFALLS

Table of Contents

Download the pdf of all presentations in a single zip file (220 Mo) or use the links below to download a pdf of each lecture individually.

Introduction (Dave Pattison)

PART 1 – THERMODYNAMIC DATABASES AND PHASE EQUILIBRIUM MODELLING SOFTWARE PACKAGES

Talk 1 – Overview of thermodynamic databases (Pierre Lanari)

In this lecture, Pierre opened the workshop by providing an overview of the thermodynamic datasets and solution models that are currently in use, before assessing the pros and cons of the various fitting procedures used to produce these data. He highlighted the need to check these datasets against experimental data and discussed the limits of uncertainty and reliability. Finally, he outlined what comes next in the development of thermodynamic databases.

Talk 2 – THERMOCALC & AvPT (Dave Waters)

Dave discussed the phase equilibrium software package THERMOCALC, an algebraic non-linear equation solver developed by Roger Powell and co-workers. He explained how thermodynamic databases and solution models are integrated into the program and what combinations of these are available for use. He then covered the different types of calculations THERMOCALC can conduct, as well as any add-on programs. To conclude, he summarised the strengths and weaknesses of the software for different types of thermodynamic calculation.

Open Q&A for talks 1 & 2

Pierre and Dave answered some additional questions during the open Q&A session of day 1.

Talk 3 – Perple_X (Mark Caddick)

Mark presented the phase equilibrium software package Perple_X, a Gibbs free energy minimizer developed by Jamie Connolly. This talk broadly covered the same topics as the THERMOCALC talk, focussing on the capabilities of Perple_X.

Talk 4 – Theriak-Domino (Doug Tinkham)

Doug provided an overview of the phase equilibrium software package Theriak-Domino, a Gibbs free energy minimizer developed by Christian De Capitani. Once again, this talk broadly covered the same topics as the THERMOCALC and Perple_X sessions but focus on Theriak-Domino.

Open Q&A for talks 3 & 4

Mark and Doug answered some additional questions during the open Q&A session of day 2.

PART 2 – FACTORS INFLUENCING THE INTERPRETATION OF PHASE EQUILIBRIUM MODELLING

Talk 5 – Uncertainties & “best practices” in phase equilibrium modelling and thermobarometry (Dave Waters)

Dave kicked off the second part of the workshop by discussing the philosophy of classical geothermobarometry vs. phase diagram-based pressure-temperature estimation. He discussed the main sources of uncertainty associated with phase equilibrium modelling (datasets, solution models, bulk compositions, chemical systems, and departures from equilibrium), with each being examined in more detail in subsequent sessions. His talk concluded with some recommended “best practices” to achieve optimal results from phase equilibrium modelling.

Talk 6 – Reactive bulk composition & Bingo-Antidote (Pierre Lanari)

Pierre discussed the concept of reactive bulk composition and showed examples where it must be considered. He explained the concept of iterative thermodynamic modelling and demonstrated its application using the Bingo-Antidote software. His talk concluded by discussing the implications that different treatments of reactive bulk compositions have for thermobarometry and petrochronology.

Open Q&A for talks 5 & 6

Dave and Pierre answered some additional questions during the open Q&A session of day 3.

Talk 7 – Equilibrium & kinetics in metamorphism (Dave Pattison)

Dave discussed how the assumption that metamorphic recrystallization never departs significantly from equilibrium may not extend to all of a rock’s prograde history, owing to kinetic impediments to reaction (e.g., nucleation, dissolution/growth, transport). Examples of petrologically-significant departures from equilibrium from contact and regional metamorphic settings were provided. The talk concluded with a discussion of how consideration of kinetics improves petrological interpretation.

Talk 8 – Assessment of databases & solution models against the natural record (Jacob Forshaw)

Jacob discussed how well current thermodynamic predictions reproduce natural observations (mineral assemblages, mineral compositions). Several examples were provided that draw on compilations of natural data from metapelitic and metabasic bulk compositions spanning a range of metamorphic grade. The talk concluded with a discussion of how the natural rock record can best be incorporated in the development of future thermodynamic models.

Open Q&A for talks 7 & 8

Dave and Jacob answered some additional questions during the open Q&A session of day 4.

PART 3 – TOPICS OF INTEREST SUBMITTED BY PARTICIPANTS