Controls on the origin and distribution of magnetite and hematite in the Mutooroo Ironstones, South Australia

This item is only available electronically.The Mutooroo ironstones were discovered by Minotaur who elected to drill four holes across the Muster Dam transect. Interpretation of these holes provided the opportunity to determine the controls and distribution of Fe oxides (magnetite and hematite) within the Mutooroo ironstones. Various investigatory techniques were carried out on the drill core acquired from the Muster Dam transect. Initial logging was conducted on the core to attempt to constrain its sedimentary, structural, mineralogical and genetic features. Magnetic susceptibility data was also collated from wire line surveys down hole allowing further mapping of underground structures between holes. Comparative Davis Tube Recovery (DTR) and X-ray Florescence (XRF) data was conducted on four-metre composites taken from intervals down each hole. The XRF analysis taken on the pre-DTR concentrate was used to calculate the weight.% (wt.%) of the total iron concentrate, while the XRF analysis taken post DTR concentrate was used to calculate the wt.% of magnetite present in the whole rock. Finally petrographic observations were made on a series of samples taken directly from the core. These samples where then analysed for textural characteristics within representative sections of the core. The stratigraphy, sedimentology and geochemistry of the Mutooroo ironstones represent a record of the climactic conditions during the Sturtian glaciation (750-700Ma) and are an example of a glaciomarine sequence. The Mutooroo ironstones consist mainly of Fe-oxide rich siltstone and diamictite units. The iron in these rocks is present in the matrix of the diamictites, or as Fe oxide (magnetite, hematite) dominated horizons of the interbedded siltstones. The rocks display a mineral assemblage representative of greenschist (biotite grade) metamorphism. Various mircotextures of the magnetite and hematite indicate that they also metamorphically derived. Geochemical analysis indicates that the Mutooroo ironstones are a result of a mixing of predominantly Fe-rich chemical precipitants and cyclic influxes of Si-Al-Ti detrital rich material. The sedimentary processes responsible for the deposition of each unit were vastly different. The diamictite was a result of a high energy, faster acting process whereby the mixing of the sediments and the discharge of glacial till caused the formation of a matrix dominated diamictite. The interbedded silts were formed during periods of protection from extensive ice shelves. During these periods chemical precipitants rich in Fe oxide were able to build up in large concentrations. The interbedded silts exhibit preserved evidence of soft sediment deformation, which infers deposition on an elevated slope. The active MacDonald fault north west of the depocentre was the likely cause for the elevated topography. Large amounts of hematite are present throughout the Mutooroo ironstone. Petrographic analysis indicates that the hematite is a syn or post deformational characteristic. The hematite presents an opportunity to improve project returns, but this will depend on further studies to determine this process is feasible and can be done economicallyThesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 201