When rocks deform in the interior of the Earth and along plate boundaries, they release part of the internal energy of the planet. These deformations may be either brittle, for example during earthquakes, or ductile, for example in shear zones or during slow earthquakes. The search for precursors to brittle deformations and for the parameters that control the transition towards ductile processes in the presence of reactive fluids represents key challenges to be investigated in this project. A major difficulty in understanding many geodynamic processes is that they occur at depths where data and samples cannot be accessed directly. However, in specially designed laboratory experiments, it is now possible to reproduce the conditions and thus geodynamic processes occurring between 0 and 10 km depths. A triaxial rock deformation rig, the only one of its kind worldwide because it is see-through at such thermodynamic conditions, has been developed at the Univ. of Oslo, in collaboration with the European Synchrotron Radiation Facility (ESRF). Samples under pressure and temperature will be imaged in-situ using synchrotron X-ray tomography directly inside the rig at a spatial resolution down to 0.6 micrometer under a photon energy of 60 keV. This device is installed on the beamline ID19 at the ESRF, the only beamline in Europe where the necessary energy and spatial resolution can be reached. With this new apparatus, a major advance is expected in rock physics, and more generally in material sciences, with several international academic research groups engaged. We will use the 3D data acquired at different spatial resolution at the ESRF to search for aseismic precursors to rupture and simulate mechano-chemical processes where fluid flow and chemical reactions are coupled to deformation. These studies will be fundamental to search for the evolution of fluid transport properties in the Earth's crust and applications in the domain of geo-engineering will be also developed.
Project leader: Francois Renard
Institution: Institutt for geofag