- 1HUN-REN Institute of Earth Physics and Space Science, Sopron, Hungary (kristof.porkolab@gmail.com)
- 2Institute of Geosciences & Mainz Institute of Multiscale Modeling, Johannes Gutenberg University Mainz, Mainz, Germany
- 3Institute of Earth Sciences, University of Lausanne, Switzerland
The expected depth of dehydration reactions in subducted slabs shows correlation with the hypocenters of intermediate-depth earthquakes, suggesting that dehydration embrittlement may be a key mechanism of earthquake nucleation. However, it is still unclear how dehydration embrittlement occurs during mineral reactions. This uncertainty is mainly rooted in the complex interactions between reaction progress, evolution of effective stresses, and deformation, which are challenging to quantify. Here we present 2D hydro-mechanical-chemical numerical models of antigorite dehydration (antigorite --> enstatite + forsterite + H2O) to quantify these interactions. We investigate how deformation may lead to dehydration and whether the reaction causes significant stress perturbations, potentially leading to earthquakes. Results show that dehydration may be triggered by fast deformation. Initially, deformation induces fluid overpressure (fluid pressure > total pressure) zones. Fluid overpressure is then relaxed by the onset and progress of the dehydration reaction, decreasing the chance of fracturing. This behavior is explained by the negative total volume change during the reaction, meaning that the solid and fluid reaction products occupy a smaller volume than the original reactant antigorite. The reaction zone is the least likely to fracture due to reaction-induced weakening and the locally larger increase of total pressure compared to fluid pressure. However, the weakening of the reaction zone also generates rheological contrasts with respect to the intact domain. As the reaction progresses, rheological contrasts induce the development of fluid overpressure zones along the sides of the reaction zone, which may lead to brittle deformation. Furthermore, reaction-induced weakening may also lead to strain localization/runaway processes, potentially causing brittle failure.
Acknowledgements
The reported investigation was financially supported by the National Research, Development and Innovation Office, Hungary (PD143377).
How to cite: Porkoláb, K., Moulas, E., and M. Schmalholz, S.: Modelling antigorite dehydration: links between reaction progress, deformation and stress field evolution , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3065, https://doi.org/10.5194/egusphere-egu25-3065, 2025.
