Page 3 - Tondietall2015

Italian Journal of Geosciences Accepted manuscript

circulation paths through porous carbonates is therefore inferred at depth due to orientation, density
and connectivity of the fault zones. Moreover, this study indicates the key role played by the pore
network characteristics (pore dimensions above all) of undeformed host rocks on determining
extremely different permeability values of the faulted porous carbonate grainstones. Accordingly,
the results presented in this study may be helpful in applications such as geofluids management for
improving the forecasting of carbonate reservoir quality and understanding the extent of reservoir
compartmentalization.

KEY WORDS: permeability, sub-seismic resolution faults, compactive shear banding, Favignana
Island, Majella Mountain.

INTRODUCTION
Deformation of porous carbonate grainstones takes generally place by compactive shear
banding, which initially produces single compactive shear bands that may evolve, during
incremental strain, into zones of multiple compactive shear bands and, eventually, fault zones with
discrete slip surfaces (TONDI et alii, 2006). Fault zones that form thanks to this processes are
generally characterized by few-centimeters wide fault core, made up of cataclastic material,
surrounded by 10s of centimeter wide damage zone that includes single compactive shear bands
(CSB) and zones of compactive shear bands (ZB). Within the fault damage zones, shear-enhanced
compaction took place, as well as extensive precipitation of calcite cements.
Previous field and laboratory studies documented the mutual relationship between porosity and
deformation processes the carbonate grainstones experienced (TONDI et alii, 2006; TONDI, 2007;
CILONA et alii, 2012; RUSTICHELLI et alii, 2012; WONG & BAUD 2012). Compaction shear banding
generally acts in grainstones with porosity >10-15%, resulting in a dramatic porosity reduction
(down to < 1%) from host rock to fault core. However, whilst some examples have been provided