Effects of orientation on the diffusive properties of fluid-filled grain boundaries during pressure solution

Abstract

An unresolved issue in the study of pressure solution in rock materials is the dependence of grain boundary structure and diffusive properties on the mutual orientation of neighbouring grain lattices. We report electrical measurements yielding the diffusivity of differently oriented halite–glass and halite–halite contacts loaded in the presence of brine. The halite–glass contact experiments show pressure solution of the halite and an effect of halite lattice orientation on grain boundary transport. Post-mortem observations show an orientation-dependent grain boundary texture controlled by the periodic bond chains in the halite structure. It is inferred that this texture determines the internal grain boundary structure and properties during pressure solution. In the halite–halite experiments neck-growth occurred, its rate depending on twist-misorientation. The results imply that deformation by pressure solution may lead to lattice-preferred orientation development, and that polymineralic rocks may deform faster at lower stresses than monomineralic rocks.