Deformation of high-pressure metamorphic rocks: mutual constraints from 2D cm-scale thermo-mechanical models and petrological observations

International audienceHow rocks deform at depth during lithospheric convergence and what are the magnitude of stress levels theyexperience during burial/exhumation processes constitute fundamental questions for refining our vision ofshort-term (i.e. seismicity) and long-term tectonic processes in the Earth’s lithosphere.We here present a set of 2D numerical experiments of eclogitic rock deformation performed at cm-scale. The deformedmedium is composed of two mineral phases: omphacite and garnet. We carried out a series of experimentsfor different background strain-rates and for a range of realistic pressure and temperature conditions. Results showthat fracturing of the entire eclogite rock can occur under HP-LT conditions for strain-rates even smaller thanthose generally expected for seismic events.We also explore the ranges of parameters where garnet and omphaciteare deforming with a different deformation style (i.e. frictional vs. viscous) and discuss our modelling results atthe light of naturally deformed eclogitic samples. Finally, we show that in cases of fracturing, the first event offrictional strain localisation constitutes a precursor for ductile strain localisation and results from the conversionof the mechanical energy into heat (i.e. shear-heating)