Microstructural and fabric heterogeneities in fault rocks associated with a fundamental fault

Abstract

The Redbank Deformed Zone of Central Australia displays heterogeneous deformation on all scales. Microstructural and fabric observations indicate that the heterogeneities arise not only from inhomogeneous deformation during individual tectonic events, but also as a result of fault reactivation. Superimposed fabrics from different deformation events can either cause the intensification of an earlier l.-s. tectonite fabric or locally produce linear-type fabrics. Fault reactivation is preferentially localized in those regions where the superimposed fabrics are parallel or sub-parallel to the original fabric. Early foliations that are unfavourably oriented in relation to later superimposed fabrics, may be left as relatively less deformed pods or lenses in the centre of the fault zone. Quartz c -axis fabrics show systematic variations with the type of fault rock, forming both symmetrical and asymmetrical girdles with respect to the foliation. Zones of high strain, where grain refinement has been greatest, display characteristic asymmetrical fabrics. Those areas in which grain refinement has been less intense and retrogression least noticeable, generally exhibit symmetrical fabrics.