Propagation and localization of stylolites in limestones

Abstract: Matrix investigations (X-Ray tomography, porosimetry by mercury injection, SEM analysis) around stylolites revealed major zones that represent different states in the propagation of the pressure solution structure. Near the stylolite termination, a significant increase of porosity relative to the far-field host rock porosity and variations in the shape of matrix particles are associated with the lateral propagation of the dissolution zone in the plane of the seam. Close to the sides of the seam, this porosity enhancement zone is found again and may be responsible for vertical development of the stylolite style. Above and below the stylolite seam, the rock matrix is less porous than the reference state nd this region appears to have been a site of precipitation ofdiffused solute. These observations imply that the enhanced porosity state around the stylolite tip is a transient one. This zone becomes a site of deposition as the stylolite tip propagates through it. The mechanism of rock deformation by pressure-solution and deposition involves the dissolution of material at grain boundaries ex