Deformation mechanisms and hydraulic properties of normal and strike-slip fault zones in porous carbonates outcropping in central and southern Italy

Deformation of porous carbonate grainstones takes generally place by compactive shear banding, which initially produces single bands that may evolve during incremental strain into zones of multiple bands and, eventually, fault zones with discrete slip surfaces (Tondi et al., 2006). The processes associated to increased deformation are recorded by the aforementioned structural elements (Tondi, 2007; Tondi et al., 2012; Cilona et al., 2012). In fact, each of the structural elements is characterized by a different texture, porosity, and dimensional attributes (i.e. length, thickness, displacement). Fault zones are characterized by a inner fault core made up of cataclastic material surrounded by thick damage zone including single bands and zones of bands. Within this latter structural domain, shear-enhanced compaction took place, and wide zones of precipitated calcite cement. In this work, we present the results of in situ permeability measurements carried out using a portable field permeameter (TinyPerm II Portable Air Permeameter, Balsamo et al. 2010) along normal and strike-slip fault zones crosscutting high-porosity carbonate grainstones of Cretaceous (Majella Mountain, Abruzzo), and Lower Pleistocene (Favignana Island, Sicily) ages. We studied nine Sub-Seismic Resolution Faults (SSRF), whose displacements are comprised between 10 and 200 cm. With the general objective of improving the knowledge on the control exerted by SSRF on the bulk permeability of porous carbonate reservoir/aquifers, this work is aimed at establishing meaningful relationships between deformation processes (taking place within fault damage zones and fault cores) and the measured permeability values.