Salt-cored domal structures in the subsurface represent common reservoir
settings. Understanding the generations and properties of the fracture network
above such structures is therefore important. This outcrop-based study
investigates fractures in the deformed carbonate layers exposed above a salt
dome at Jebel Madar, Oman. Methods used to study the fractures and their
infillings include fracture analysis, petrography and stable isotope geochemistry.
Regionally occurring NNE/NE-SSW/SW and NW-SE trending fractures constitute
important fracture sets across Jebel Madar. In addition, it was observed that the
doming process led to the development of local fractures that overprint the
regional trends. A study of the textures and composition of the fracture infilling
material indicates that a dominantly advective mode of fluid transport occurred in
the NNE/NE-SSW/SW trending veins, which developed due to repeated
fracturing and re-cementation. These veins are associated with phases of doming
and related pulses of high volumes of fluids during times when the maximum
horizontal stress was oriented NE-SW. In contrast, a more diffusive mode of fluid
transport is thought to have occurred in the NW-SE trending fractures, which
developed during times when no doming was occurring. Although the diapir
seems to be the main drive for fluid circulation and the precipitation of most
diagenetic products occurred during periods of doming, vein infilling also
occurred, to a lesser extent, during periods when doming was absent. The
frequent occurrence of normal faults, extensional opening fractures and
implosion breccia suggests that the layers above the diapir were highly extended
during the salt emplacement. In addition, some of the extension was found to be
accommodated by the development of shear movement (down-dip slip) on
original mode I fractures. Their similar appearance on seismic sections to classic
normal faults could lead to a misinterpretation of their fluid flow properties.