Metamorphic petrologists as well as structural geologists bring important direct rock-based observational constraints for geodynamic models. If properly quantified and interpreted, fabrics and microstructures in rocks provide fundamental constraints on lithospheric evolution. However, in the context of the complexity of observations, application of inappropriate quantification approaches may lead to flawed interpretations.
Deformation of rocks at convergent and divergent plate boundaries is accompanied by changing pressure, temperature and fluid conditions resulting in metamorphic reactions and consequent phase transformations. The positive feedback between deformation and metamorphism and vice versa has been a long recognized phenomenon. Both deformation and metamorphism, however, lead to important changes in microstructure of rocks which in turn control their mechanical properties. Thus in the light of progressing metamorphic transformation coeval with deformation, the standard mechanical criteria based on the fixed rock properties such as phase content, chemical composition, phase proportion and distribution, and grain size are constantly changing. This is a challenge for the rheological predictions used in the large-scale geodynamic models as well as for thermodynamic quantification approaches in petrology.
In this session we intend to combine contributions discussing the impact of metamorphism on deformation as well as the impact of deformation on metamorphism. The session will provide a cocktail of experimental, natural, as well as theoretical and modelling studies documenting the "why and how" evolution of any rock microstructure. We also aim to discuss the implications of all current approaches for phase equilibria and diffusion and its impact on geodynamic modelling.