Fluid flow through patterned shear zones

Numerical models demonstrate that fluid flow is affected by the formation of shear zones as predicted by a simple model based on the principle of effective stress but only under specific conditions of fluid flow and rate of material deformation. Under crustal conditions, patterned shear zones form during a simple shearing deformation history. Fluid flow is focussed into and along these shear zones for a hydrostatic pore pressure gradient, but is upwards and unperturbed by the shear zones for a lithostatic pore pressure gradient. Under certain conditions of fluid flow rate and deformation rate, the presence of a fluid appears to have a stabilising effect, and the material continues to deform homogeneously. Predictions based on the simplified principles of effective stress do not sufficiently describe the possible complex inter-relationships. It is therefore crucial to our understanding of fluid flow and deformation that we examine the full coupling by integrating field observations, laboratory experiments, theory and numerical codes. -Author