Dynamically evolving fluid transport properties in mylonitic shear zones

Deforming rocks in mylonitic shear zones are first-order fluid conduits in the crust, where fluids are hosted by grain boundaries, cracks and pores, all of which evolve during deformation and synkinematic reactions. This evolution, which entails coupled chemical, hydraulic and mechanical processes on multiple scales, controls where fluids will migrate and interact with rocks. However, we have no systematic and comprehensive knowledge of how these processes, and feedbacks between them, combine to form the dynamic transport properties of natural mylonitic shear zones. This shortcoming severely affects our multi-scale assessments of fluid-rock interaction at plate boundaries and at other societal interfaces with the geosphere.
In this presentation, I will provide a brief overview of mechanisms that produce (and destroy) porosity in mid-crustal mylonites. I will use high-resolution µCT and SEM data from natural shear zones and operando experiments to derive a conceptual model for how porosity and permeability evolve as a function of shear strain. This model highlights critical but measurable parameters that enable its integration into forward simulations of fluid migration in deforming crustal rocks.