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Type: Thesis
Title: Structural evolution of deformation bands
Author: Lubiniecki, Drew Christopher
Issue Date: 2019
School/Discipline: School of Physical Sciences : Earth Sciences
Abstract: Deformation bands are the most common strain features observed in deformed upper crustal sections of porous sedimentary rocks, like sandstone and carbonate grainstone. A deformation band is a tabular zone of localised strain that forms as a result of compaction due to sediment loading and high deviatoric stress. These bands of strain exhibit considerable variation in structural kinematic styles (compaction band, shear band, dilation band, and hybrids) and formation mechanics (disaggregation band, cataclastic band, phyllosilicate band, and cement/ dissolution band). The variations may enhance or retard subsurface fluid flow and create permeability anisotropy, especially surrounding fault zones. Uranium is mobilised easily by fluids in sedimentary basins, thus this project explores practical uses for sedimentary-hosted mineral exploration, specifically targeting faulting. Fault-induced deformation bands reflect the stress state at the time of formation, creating a foundation for palaeostress reconstructions using deformation bands as indicators of discrete changes to the local and far-field stress. Despite considerable research to siliciclastic-hosted bands, research bias has contributed to a lack of understanding of carbonate-hosted cataclasic bands and dilation bands. This study presents an investigation of the structural styles that govern the formation mechanisms of newly described deformations bands observed at Marion Bay, Stenhouse Bay, Port Vincent, Port Willunga, and Sellicks Beach in the southern Mount Lofty Ranges; the Dead Tree section and Parabarana Hill in the northern Flinders Ranges in South Australia; and the Athabasca Basin in northern Saskatchewan, Canada. Detailed face mapping and structural analysis of 737 deformation bands and 397 fractures observed near the Port Vincent Fault, Marion Bay Fault, Stenhouse Bay Fault, Willunga Fault, and Paralana Fault infers the structural evolution of the Mount Lofty Ranges is remarkably similar to the palaeostress evolution of the northern Flinders Ranges. These results define a five stage evolution sequence for the region: Stage 1) NW–SE extension (early Palaeocene– early Eocene); Stage 2) N–S extension (middle Eocene–middle Miocene); Stage 3) N–S compression (late Miocene); Stage 4) NW – SE compression (Pliocene–middle Pleistocene); Stage 5) E–W compression (late Pleistocene–Present-day). Detailed face mapping, permeameter, and transmitted light microscopy results confirms 286 dilation bands are hosted within the Eyre Formation at the Dead Tree section in the northern Flinders Ranges. Integration of this data with our palaeostress model and Paralana Fault geometry reveals the region underwent transtension during Stages 2 and 4 of our palaeostress model, resulting in the formation of dilation bands observed at the Dead Tree section. I suggest these events enhanced localised effective permeability between the Mount Painter uranium source and Four Mile uranium deposit. Detailed face mapping, permeameter, and transmitted light microscopy results confirms 221 cataclastic bands with differing intensities of cataclasis, pressure solution, disaggregation, and cementation are hosted within the Port Willunga Formation at Sellicks Beach. To standardize the nomenclature, I suggest the fault rock classification scheme of cataclasis intensity for carbonate-hosted deformation bands. In the Athabasca Basin, I mapped 1713 deformation bands in detail within the Manitou Falls Formation. Six stage palaeostress model is inferred for the Manitou Falls Formation: Stage 1) NW–SE extension; Stage 2) E–W extension; Stage 3) NE–SW extension (1.3 Ga); Stage 4) NW–SE transpression; Stage 5) N–S compression; Stage 6) E-W compression. Scanning electron microscopy indicates cataclasis, dissolution, dilation, and fracture control formation mechanics in the Manitou Falls Formation. For the first time ever, I document the occurrence of reactivated cataclastic bands. This study confirms deformation bands are excellent indicators of discrete changes to the local and far- field stress regime, enhance our understanding of the evolution of Earth’s crust, and present a useful tool to understand fault history and fluid flow, especially for sedimentary hosted uranium exploration.
Advisor: King, Rosalind
Holford, Simon
Bunch, Mark
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2019
Keywords: Deformation bands
cataclastic bands
dilation bands
dissolution bands
dilative-cataclastic bands
fault evolution
Athabasca Basin
St Vincent Basin
Mt Lofty Ranges
Flinders Ranges
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