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TS1.7 | Brittle failure, creep, and metamorphism in the brittle-ductile regime
EDI
Brittle failure, creep, and metamorphism in the brittle-ductile regime
Convener: Sascha Zertani | Co-conveners: Giovanni Toffol, Anna Rogowitz, Friedrich Hawemann
Classical models of crustal rheology assume a shallow brittle crust, where seismic and aseismic brittle faults are the primary deformation features, and a ductile lower crust, in which deformation by crystal plasticity dominates. These two deformation regimes are connected by the so-called brittle-ductile transition, a several kilometer-wide zone governed by the onset of crystal plasticity of quartz and feldspar. However, geophysical, geological, and experimental evidence have challenged this simplified rheological model of the lithosphere.
A large number of factors including the composition, fabric, and fluid content significantly impact rock strength and thus deformation behavior. Consequently, the relationship between deformation style and depth (or rather P-T conditions) is not as clear-cut as predicted by classical models. Moreover, brittle failure and creep may both occur simultaneously, or cyclically, and are thus dependent on each other. Additionally, changes in deformation style are intimately linked to metamorphic reactions. Consequently, the interaction of brittle and ductile deformation, and metamorphism define bulk crustal rheology.
Several processes have been identified to contribute to the dynamic switch between fracture and creep, which include, fluid influx, metamorphic reactions and phase mixing, grain size reduction, thermal runway, transient stress rise, variations in strain rate, and strain incompatibilities. We invite contributions based on natural, experimental, and numerical examples to discuss how, why, and when the crust breaks or creeps and how rheological transitions are influenced by metamorphic reactions.