| Context: The problem of fluid access and interaction, in `normally' impermeable deep crustal and upper mantle rocks undergoing deformation near the brittle/ductile transition. Also directly applicable to geoengineering in saltrocks, strategic fluid- storage and hydrocarbon seals. Aims: Determination of the effect of added brine on dilata dilatancy development (microcrack growth) microcrack healing and the evolution of permeablity plus electrical conductivity in plastically deforming rocksalt. Interpretation of the results in terms of changes in microcrack/pore geometry and connectivity, making use of microphysical models based on percolation theory. Determination of the effect of fluid assisted dynamic recrystallisation of rocksalt on electrical conductivity and thereby to estimate the thickness and diffusivity of the intergranular fluid films involved in the recrystallisation process. Assessment of the implications for the permeability and electrical conductivity characteristics of crustal and upper mantle rocks undergoing plastic deformation in the presence of a chemically active fluid phase. Methods: Use of new dynamic measurement techniques to measure the fluid transport properties (permeability and electrical conductivity) of the rock material, whilst deformation is in progress at elevated pressures within a rock deformation apparatus. The method of electrochemical impedance Spectroscopy (EIS) will be applied and developed alongside existing fluid permeametry techniques. |
