Anticrack model for pressure solution surfaces.

It is proposed that discrete solution surfaces originate at stress concentrations and propagate through rocks as anticracks. As material is dissolved and removed, the anticrack walls move toward each other; stress and displacement fields are identical with those for the conventional opening crack, but with a change in sign. Observations of entire traces of solution surfaces are consistent with the anticrack concept: 1) the surfaces are bounded in extent; 2) the dissolved thickness varies from the centre to zero at the tips; and 3) the maximum dissolved thickness is proportional to the length of the surfaces. Local dissolution and in-plane propagation are suggested by the large isotropic compressive stress at the anticrack tip. Intersecting arrays of cracks, anticracks, and shear cracks operate to yield a mode of bulk deformation similar to diffusion-accommodated grain boundary sliding in polycrystalline solids.-A.P.