School of Earth Sciences - Theses
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ItemMetamorphism of granulite facies metapelites( 2004)This thesis involves a study of metamorphism and partial melting in granulite facies metapelites from three regions, the Larsemann Hills and the Rauer Group of east Antarctica, and Fishery Bay in southern Eyre Peninsula of South Australia. Along with the metamorphic study, $^40Ar/^39Ar$ thermochronological dating was also undertaken for the first two areas to constrain the timing of tectonothermal events and syn- to post-tectonic cooling history. (From Abstract)
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ItemThe Mine Creek region, Eyre Peninsula, South Australia: a structural analysis of the Kalinjala Shear Zone( 2000)Mine Creek, located in the Eastern Eyre Peninsula, South Australia, exposes a natural cross section through the Kalinjala Shear Zone where it juxtaposes a sequence of granulite facies metasediments to the west from upper amphibolite granite gneisses to the east. The lithologies include biotite-garnet schists, forsteritic marbles, biotite-hornblende amphibolite, banded iron formation and quartz +feldspar +biotite +hornblende ± garnet megacrystic granite gneisses. These rocks preserve evidence of at least two deformation events. D1 formed a layer- parallel S1 foliation defined by peak garnet +biotite +quartz +feldspar assemblages, with no recognised folding. Associated with this deformation was the initiation of the NE-SW oriented, dextral transpressive, Kalinjala Shear Zone, which is up to 3km wide and 300km long. The shear zone is characterised by high-grade assemblages, steeply plunging stretching lineations (L1) and dextral kinematic indicators. The formation of S^C, fabrics, C' shear bands and local ultramylonitic zones indicates intense shearing and high-strain. D2 developed isoclinal F2 folds and a localised NE-SW orientated S2 axial planar cleavage, that was not pervasive. Progressive deformation and retrogression and subsequent tectonic reworking has created a highly recrystallised and structurally complex environment. A strain analysis of the augen gniess was undertaken using both finite strain methods and by qualitative examination of gneissic fabric intensity. Although finite strain estimation met with limited success, results demonstrate a significant component of flattening was responsible for producing strongly oblate strain markers. Analysis of shear zone fabric development reveals strain insensitive composite fabrics that do not accurately reflect the total amount of strain accommodated by the rock. Instead their oblique orientation, relative to the shear zone boundaries reflects non-coaxial strain and may be used as an important kinematic indicator. Deformation fabric analysis resolves the intensely strained nature of the lithologies of Mine Creek, these are dominated by S^C orthogneiss and layered mylonite fabrics. Low-strain fabric features in the granite gneisses are not preserved.