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Honours Thesis Abstract GEODYNAMIC EVOLUTION OF A PROTEROZOIC CRUSTAL-SCALE SHEAR ZONE: CONSTRAINTS FROM DEFORMATION, METAMORPHISM AND GEOCHEMISTRY Robin Armit Monash University, Vic 2007 Bonwick - AIG Honours Bursary Winner The Paralana Fault Zone is interpreted as a crustal-scale shear zone. Preserved within this shear zone is a record of protracted activity at varying crustal levels since at least the Mesoproterozoic. An early ductile sinistral transpressive regime is related to D3 NW-SE shortening and retrograde metamorphism. The Radium Creek Metamorphics preserved in the hangingwall of the shear zone records rapid burial (~3 km/myr) post ca. 1592 Ma to sillimanite grade (upper amphibolite facies) recording peak metamorphism M1 during D2 NW-SE shortening. Rapid exhumation (~3-4km/myr) of these rocks occurred between ca 1582-1575 Ma, prior to the emplacement of the Mount Neill Massif at shallow crustal levels (~2km). The A-type affinity Mount Neill Massif was emplaced in a within-plate tectonic environment ca 1575 Ma (Elburg et al. 2001) probably along the active crustal-scale shear zone. A change to a brittle dominated regime occurs with the onset of extension during the deposition of the Adelaidean Rift Complex. Basin inversion related to the Delamerian Orogeny (D4) leads to the exhumation of the Mount Painter Inlier along a brittle, sinistral strike-slip Paralana Fault Zone with subsequent late Tertiary uplift.
