Abstract

Trans-crustal shear zones are principal fluid conduits in the Earth’s crust, but exactly how fluids migrate in deforming rocks of the middle and lower crust is poorly understood. This is mostly due to limitations in our investigative approaches: classical experiments fail to resolve the relevant developments in-situ, and field-based studies are mostly confined to the post-mortem analyses of exhumed rock specimens.

It can be expected that the evolving fluid transport properties of shear zones are dynamically coupled to the deformation and metamorphism affecting mylonites. Different deformational and metamorphic processes contribute to the formation or modification of porosity in shear zones and thus affect fluid migration. The time- and space-dependent evolution of permeable porosity controls where fluids can migrate and interact with rocks. Understanding a dynamically evolving porosity in deforming and reacting rocks is thus important in tectonics, but also in applications such as geothermal energy harvesting, nuclear waste storage, CO2 storage, hydrothermal ore forming processes and hydrocarbon extraction.

X-ray µCT allows us to overcome the limitations of classical approaches and study porosity and fluid migration in deforming rocks in-situ. In this presentation I will summarise some of our studies that use 3- and 4-dimensional µ-tomographic data to characterise previously overlooked, or poorly characterised processes. These processes directly influence the transport properties of, and fluid migration in ductilely deforming rocks.