Fluid impact and spatial and temporal evolution of normal faulting in limestones. A case study in the Burdur-Isparta region (SW Turkey)
Geodynamics and Geofluids Research Group, Afdeling Geologie, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium,
Geodynamics and Geofluids Research Group, Afdeling Geologie, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium, e-mail: philippe.muchez@geo.kuleuven.be
Department of Geology, Vrije Universiteit Brussel, B-1050 Brussel, Belgium
Geodynamics and Geofluids Research Group, Afdeling Geologie, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium,
Abstract
ABSTRACT. The development of normal faults in carbonates in upper-crustal conditions (< 1-3 km) is a very complex process, because of the interaction of mechanical and chemical processes. This paper investigates the effect of the architecture of normal faults on fluid flow at different depths. This study has been performed on a well-exposed normal fault complex, i.e. the Sarikaya fault complex, in the Burdur area, situated ~120 km north of Antalya (SW Turkey). The particular outcrop allowed studying fault zone architecture and fault-related precipitates at different structural levels over a vertical distance of ~250m.
The earliest stage of normal fault zone development occurs with the upward propagation of a neoformed fault. Seismic deformation is responsible for the development of a low permeable stylobreccia at depth. During fault movement, permeability is greatly enhanced at the fault plane contact. This permeability enhancement causes a fluid-pressure differential responsible for co-seismic, focused fluid flow parallel with the fault plane. Calcites on the fault plane and in veins in the damage zone precipitated from rock buffered fluids (13C = -0.1 to +2.5‰ V-PDB, 18O = -4.0 to -0.7‰). During repetitive increments of seismic slip, permeability is renewed at the fault plane contact and fluids are expelled. These increments of seismic slip lead to fault propagation. This fault propagation is accompanied by the formation of a fault precursor breccia ahead of the fault tip by intense localized fragmentation and brecciation of the adjacent shatter zone. This leads to a cohesive breccia where confining pressure is still high and an incohesive breccia near the surface. The cohesive damage zone acts as a combined conduit-barrier system and a more dispersed, co-seismic fluid flow is present near the fault plane contact. The near-surface, incohesive damage zone is characterised by a high permeability, which leads to a highly dispersed fluid flow. Meteoric water can easily infiltrate which leads to static fluid interaction with the normal fault.
Later propagation of a fault plane through its fault-precursor breccia belt results in the deformation concentrated along the fault plane and the evolution of the fault-precursor into a fine gouge or attrition breccia. Once a slip plane reaches the free surface by propagating through its own (in)cohesive breccia belt, co-seismic deformation is restricted to a relatively narrow zone of attrition. In the case of the cohesive damage zone, fluid flow is enhanced adjacent to the slip plane. The fault related fluid is in equilibrium.