Reaction-induced volume change triggers brittle failure at eclogite facies conditions

Metamorphic reactions can lead to important changes in rock strength and density. Eclogitization constitutes one of the most emblematic transformations continental subduction zones, where conversion lower crustal rocks into eclogite facies correlates with occurrence seismogenic events. The relationship between eclogitization seismicity has been highlighted several studies, but processes that trigger brittle failure remain highly debated. Indeed, whether change density (from ∼2850 kg.m−3 ∼3300 kg.m−3) or rheology embrittlement is still enigmatic. Here we show eclogitization-induced volume occurring out equilibrium can, by itself, generate sufficient shear stress fail at high-pressure conditions. Intermediate-depth earthquakes zones could therefore be explained changes, even without considering rheological modifications induced mineral reactions. Our results also indicate interplay negative frictional plastic yielding enhance propagation process a runaway mechanism as long reaction not limited lack reactants.