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TS1.1 | The brittle-ductile trans(pos)ition: natural, numerical, and experimental examples of failing rocks
EDI
The brittle-ductile trans(pos)ition: natural, numerical, and experimental examples of failing rocks
Convener: Sascha Zertani | Co-conveners: Giovanni Toffol, Natalia NevskayaECSECS, Friedrich Hawemann
In classical fault zone models, the transition between brittle and ductile deformation in the continental crust is governed by the onset of crystal plasticity of quartz and feldspar, typically at depths of 10-15 km. However, geophysical, geological, and experimental evidence exists, that also rocks at greater depths experience brittle (seismic) failure. This can occur both in strong rocks of the middle and lower crust and in relatively weak rocks deforming in the ductile regime, with rupture taking place as a stand-alone process or intimately associated with ductile flow. In the extreme case, brittle failure is evidenced by the presence of pseudotachylytes (i.e. coseismic quenched frictional melt), but also by micro-scale fracturing of mineral grains, cyclic switches between fracture and flow in mylonites, or it results from volume changes induced by mineral reactions.
Several processes have been identified to contribute to this dynamic switch, which include for example, fluid influx, metamorphic reactions and phase mixing, grain size reduction, thermal runaway, transient stress rise, variations in strain rate, and strain incompatibilities. We therefore invite contributions from natural, experimental, and numerical examples to discuss these processes – and how, why, and when the crust breaks (or not).