Mech-Chem evolution during eclogitization of mafic rocks

The geodynamic evolution of the earth is highly governed by the deformation behaviour of rocks at plate boundaries. In convergent settings, dry mafic rocks are subducted to great depths where they experience high pressures and temperatures. These increased pressure and temperature conditions cause a mineral transformation which subsequently results in the change of the mechanical behaviour of the rock. A frequent, and therefore important rock in such continental and oceanic subduction zones is eclogite. So far the rate of eclogitization (i.e. metamorphism of a dry mafic rock into an eclogite) and to which extent the process of eclogitization influences the mechanical evolution of a dry mafic rock is poorly understood. However, it is well known that metamorphism/eclogitization is promoted by the presence of fluids as well as rock deformation. In the course of eclogitiztaion, chemical and mechanical processes interact in a complex way. In the research project on Mech-chem evolution during the eclogitization of mafic rocks, we plan to investigate this complex interplay between mechanical and chemical processes. We will perform laboratory experiments in order to mimic the process of eclogitization under well constraint conditions. Varying deformation and fluid conditions will be applied in order to investigate their influence on the rate of eclogitization, the evolution of a porosity and fluid pathways as well as potential changes of the mechanical behaviour. Parameters will be quantified in the best possible way based on our investigations. Detailed high resolution analytical techniques will be applied to characterize experimentally derived microstructures. In a second step, those structures will be compared to naturally eclogitized rocks in order to identify diagnostic structures. This will allow us to extrapolate well constrained experimental rates to natural complex systems. This study aims for a better understanding of micro- to meso-scale processes operating in the roots of orogens. Quantification of the rate of eclogitization and its related changes in mechanical rock behaviour are crucial input parameters for future geodynamic models and therefore, potentially improve our understanding of the evolution of orogens.