Deformation mechanisms in fine grained quartzo-feldspathic mylonites : an electron microscopy study

Abstract

Previous work on the deformation mechanisms in quartzo-feldspathic rocks from the upperand middle-crust has predominantly concentrated on single phase quartz bands within these rocks. This has served well as a first approach, but several shortcomings have become evident concerning the highest strained and most fined grained parts of shear zones. It will be shown in this thesis, that under some circumstances the single phase approach is appropriate, but in many cases it is inadequate and can lead to erroneous interpretations of lithospheric rheologies. This thesis concentrates on the investigation of the intra- and intercrystalline deformation mechanisms in fine grained quartzo-feldspathic rocks from the Redbank Deformed Zone, a major transcrustal shear zone in Central Australia. In this research, advanced transmission electron microscopical (TEM) techniques, together with field work, light microscopy (LM) and scanning electron microscopy (SEM) have been used to study the microstructures and microtextures of these rocks. Concepts developed within the metals and materials sciences have been utilised to quantify and understand the deformation of the quartzo-feldspathic rocks.