Coleman, P. M.2020-10-292020-10-292009http://hdl.handle.net/2440/128699This item is only available electronically.Volcanic rocks attributed to the ca. 1080 Ma Giles Event were extruded within the western Musgrave Block in the late Mesoproterozoic. SHRIMP U-Pb analysis of two samples of zircon cores from rhyolites approximately 2km SSE of Blackstone Range yielded 238U/206Pb crystallisation ages of 1071±8 Ma and 1073± 7 Ma. These rhyolites, forming the base of the Smoke Hill Volcanics at Mount Jane were unconformably emplaced over the Blackstone Range layered intrusions in a series of separate flows. Soon after being extruded the rhyolites were deformed and developed pervasive NE-or SW dipping foliation within a 2km wide shear zone at Mount Jane. Garnet and epidote replacement of plagioclase phenocrysts indicates at least lower amphibolite-facies metamorphism was attained within the near vertical, south-dipping ultramylonite centre of the shear zone. Shear sense indicators within the shear zone almost exclusively give north side down kinematics in outcrop and in thin section. A syn-tectonic micro-granite intrudes the centre of the shear zone with veins that cross-cut the ultramylonitic foliation and hence post-dates shearing. This micro-granite yields a 238U/206Pb vs 207Pb/206Pb isotope ratio zircon age of 1070±5 Ma. Thin, highly luminescent, structureless rims surround the zircons and yield a similar or slightly younger age than the cores. Therefore, the deformation was most likely synchronous, or soon after, the eruption of the rhyolite as part of the Giles Event. A series of mafic and intermediate volcanic rocks attributed to the Hogarth Formation directly overlie the rhyolite, dip steeply towards the south, and have been cut by a series of later stage gabbros and granites.enHonours; Geology; Musgrave Block; Giles Event; Tollu Group; volcanics; deformation; zirconThesis