FRACTURES, FAULTS, AND EVOLUTION OF FLUID PATHWAYS IN CARBONATES OF THE ALBANIDES FOLD-THRUST BELT

The process of fracture and fault formation in carbonates of the Albanides fold and thrust belt has been systematically documented through the hierarchical development of structural elements. A field based methodology has been applied to elucidate the impact of fractures and faults on fluid migration within a generally complex system. Multiple modes of structures including folds, thrusts and strike-slip faults have been investigated from outcrop to geologic map scale. We have identified two pre-folding pressure solution/vein assemblages: an overburden assemblage and a remote tectonic stress assemblage. The remote tectonic stress assemblage structures include NW-SE trending pressure solution seams, and NE-SW trending veins, trending parallel and perpendicular to the tectonic grain, respectively. Sheared layer parallel pressure solution surfaces of the overburden assemblage define mechanical layers. Shearing of mechanical layers associated with folding results in formation of a series of splay fractures, or folding assemblage fractures, at different orientations within individual mechanical layers. Pre-folding fracture assemblages and splay fracture systems interact to form fragmentation zones within mechanical layers, and are the sites of incipient fault localization. Further deformation is accommodated by rotation and translation of fragmented rock, forming breccia and facilitating fault offset across multiple mechanical layers. Cemented fault zones and bitumen accumulation along fractures and faults attest to the localization of fluid flow along fault zones. By systematic identification of fractures and faults evolution, and their fluid and bitumen contents, we identify NE-SW trending strike-slip faults and the associated structures as dominant fluid pathways.