Faulting processes at high fluid pressures

Abstract

The internal structures of the Wattle Gully Fault provide insights about the mechanics and dynamics of fault systems exhibiting fault valve behavior in high fluid pressure regimes. The Wattle Gully Fault forms part of a network of faults that focused upward migration of fluids generated by metamorphism and devolatilisation at deeper crustal levels. The fault has a length of around 800 m and a maximum displacement of 50 m and was oriented at 60° to 80° to the maximum principal stress during faulting. The structure was therefore severely misoriented for frictional reactivation. This factor, together with the widespread development of steeply dipping fault fill quartz veins and associated subhorizontal extension veins within the fault zone, indicates that faulting occurred at low shear stresses and in a near-lithostatic fluid pressure regime. The geometries, distribution and internal structures of veins in the Wattle Gully Fault zone are related to variations in shear stress, fluid pressure, and near-field principal stress orientations during faulting. -from Author Show more