PAPER – ITM part 2

by | 15 Aug 2021 | Publications

We have published in collaboration with Erik Duesterhoeft from the CAU University Kiel a paper in the Journal of Metamorphic Geology describing a new hybrid modelling strategy for thermobarometry applicable to metamorphic rocks. This contribution describes a mutually consistent strategy based on quantitative compositional mapping and the software solution Bingo-Antidote integrated in XMapTools.

Mineral assemblage and mineral modes simulated in Model [2a] at 650°C and 0.8 GPa for (a) the bulk rock composition and (b– d) three selected simulations (#6358, #7134 and #8678) corresponding to a garnet-rich, plagioclase-rich and muscovite-rich domains. The quality- factor Qtotal1 for each simulation is 100% because for well-equilibrated samples (and perfect thermodynamic data), ITM based on the bulk rock composition or any LBC will converge to the ‘optimal’ P–T conditions re- flecting equilibration condition

We show in this study that the interpretation of modelled mineral assemblages can be ambiguous in the presence of mineral relics that are predicted to be stable far away from their formation conditions. The phase(s) in disequilibrium can in theory be assessed from maps of quality factors for each mineral or statistically by combining LBC obtained from domains with variable mineral mode.

Quantitative compositional maps of garnet showing end-member atomic fractions for (a, c, e, g) the porphyroblast in Area 3 and (b, d, f, h) a smaller grain located in Area 2. The colour scale used for each end-member is the same for the two maps

Bingo-Antidote is integrated in the mapping software XMapTools via the add-on XThermoTools.

Find out more

Lanari, P. & Hermann, J. (2020). Iterative thermodynamic modelling—Part 2: tracing equilibrium relationships between minerals in metamorphic rocks. Journal of Metamorphic Geology, 39, 651-674. Download pdf | Visit the journal webpage

Duesterhoeft, E. & Lanari, P. (2020). Iterative thermodynamic modelling—Part 1: A theoretical scoring technique and a computer program (BINGO-ANTIDOTE). Journal of Metamorphic Geology, 38, 527-551. Download pdf | Visit the journal webpage

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