This project is dedicated to quantifying the feedbacks between reaction thermodynamics and mechanical properties of rocks. New cutting-edge numerical models will be developed, constrained by state-of-the-art laboratory experiments. As a post-doctoraI researcher, I will be in charge of the experimental part of the project.

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The aim of this post-doctoral project is to integrate the feedbacks between deformation and nucleation of reaction products in numerical models at sample scale. To do so, we use the energy produced by the deformation of a rock (strain energy ~ mechanical work) to preferentially locate the nuclei at each time step. Nuclei have different mechanical properties than the matrix and therefore promote or impede strain localization and embrittlement. [work in progress]

In a recent study (Baïsset et al., 2023) we have shown that deformation twins in plagioclase from an eclogitic finger affecting continental granulites (Holsnøy, Scandinavian Caledonides of Norway) form in a stress field compatible with the orientation of the strain at the time of metamorphism and shear zone formation in the massif. Therefore, are finger shaped structures preferentially oriented at the scale of the whole island ? How do they form and propagate in the previously layered granulites under stress ? Is there a relationship between eclogitic shear zones and eclogitic fingers ? ... [work in progress]

As eclogites are known to be weaker than their granulitic protolith, how do eclogite shear zone widen over time instead of infinitely localizing the deformation ? Through detailed petrological analysis and thermodynamical modeling we highlight the transient effects and features of the eclogitisation reaction. In a second time, we numerically model and quantify these effects. [associated publications : Bras et al., 2021]

Deformation twins in plagioclase is found here (in natural and experimentally deformed samples) to act as intracrystalline nucleation sites for melting and reaction and to be responsible for grain-size reduction. We study the interplay between brittle microcracking and plastic deformation twinning and their effect on intracrystalline melting and/or reaction, which has the potential to lower the effective grain size of plagioclase-rich rocks and thus impacts their reactivity and deformation behaviour. [associated publications: Incel et al., 2022; Baïsset et al., 2023]

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The mechanical behavior of plagioclase feldspar is of major importance for the understanding of lower continental crust rheological behavior, as it constitutes the major part of its mineralogical structure. In particular in convergence zones, where it suffers pressure, temperature and water content changes, as well as strain rate increase. My research aims at providing more constraints on the rheological behavior and effective strength of the plagioclase-bearing lower crust in convergence zones, through petrological observations on natural samples, and deformation experiments. [PhD thesis]

The Griggs-type apparatus at the Ecole Normale Supérieure de Paris is equipped with acoustic monitoring. This allows (1) to monitor grain cracking and micro-seismicity during deformation experiments (passive monitoring), and (2) to find P-wave velocity in the samples during their deformation and transformation, thus following "in-live" reaction kinetics (active monitoring). The aim of the following years is to improve this equipment and apply the technique on new transformations

[associated publications : Moarefvand et al., 2021; Gasc et al., 2022; Moarefvand et al., 2024; Sawa et al., (under review)]