Faults and joints are present in most aquitard units and were formed either during tectonic deformation events or as a consequence of decompaction. In aquitards rich in clay minerals, fractures self-seal efficiently and do not constitute preferential fluid pathways, except in transient stages of deformation. In clay-poor aquitards, the self-sealing capacity may be reduced, and fractures may have permeability well above that of the undeformed rock. Knowledge of the fracture geometry and of the underlying deformation mechanisms are pre-requisites for the understanding of the connectivity of fractures on larger scales and therefore for their relevance as fluid pathways.
We study water-conducting structures in drillcores and use mapping of analogous features on the surface to better understand the larger-scale geometry. We consider structures that were fluid pathways in the past (characterised by mineralisations or wallrock alterations) as well as those that conduct water today.
