School of Earth Sciences - Theses

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    The major, trace and precious metal geochemistry of some Permian layered intrusions, Central Queensland
    Reeves, Shane John ( 1990)
    The Bucknalla Complex, previously known as the Westwood Layered Intrusion, is a small, 10 km2, layered, tholeiitic, mafic-ultramafic intrusion located 50 km southwest of Rockhampton that was emplaced into an active continental margin environment in the Permian. The complex comprises clinopyroxenites, olivine clinopyroxenites, wehrlites, troctolites, hornblende gabbros, gabbros, anorthosites, leucogabbros and dolerites. It is a saucer-shaped lopolith (2200 m X 6 km at maximum stratigraphic intersection) which intruded Lower Permian spilitic pillow lavas, cherts and tuffs of the Rookwood Volcanics during the Lower Permian. It has subsequently been tilted vertically and in a northeast direction. It consists of over 15 laterally discontinuous igneous units ranging in thickness from 1-50 m. Plagioclase is a cumulus phase throughout the intrusion while orthopyroxene is absent until the very uppermost levels of the stratigraphy. The chromium composition of magnetite analysed by electron microprobe has been found to mimic whole-rock mg# and is a good measure of the degree of fractionation of the rocks. Electron microprobe analyses of samples from two traverses perpendicular to layering reveal cryptic variation in the primary phases (olivine: Fo69-83; plagioclase: An54-97; clinopyroxene mg#: Cpx67-87) which is not a simple function of stratigraphic height. Background PPGE (Pd & Pt), Au, S and Cu values for the intrusion are high while IPGE (Ir & Ru) are low. A total of 120 analyses has produced the following range of values: Pd, 2-70 ppb; Pt, 3-40 ppb; Au, 1-20 ppb; Ir, 0.01-0.07 ppb; Ru, 0.2-0.6 ppb; S, 150-400 ppm and Cu, 40-600 ppm. Platinum, Pd and Au display good correlations with Cu, particularly at more elevated levels, while Ir and Ru are better correlated with whole rock Ni and Cr. Palladium, Pt, Au, Cu & S are elevated in rocks which have intermediate whole-rock mg# (47-60). These trends suggest that the PGE are, to some extent, controlled by fractionation and that the high melting point PGEs (Ir, Ru) were precipitated with the early crystallising phases, such as olivine and clinopyroxene, whereas Pt, Pd and Au were removed from the magma by sulphides. Mantle normalized metal plots for both the mineralized and unmineralized rocks of the Bucknalla Complex display similar trends. Both plots display the anomalous low Ir content, PPGE enrichment and the clear control of sulphides on the distribution of the PGEs and Au. The ratio Pd/Ir is extremely high (1800-9300) indicating extreme fractionation of the PGEs. These trends may, in part, reflect PGE abundances inherited from the source (i.e. relatively low degrees of partial melting) but were exaggerated by the extraction of the IPGE during the early stages of fractional crystallization and by the precipitation of a PPGE-enriched sulphide component. The Complex is known to host minor Pd-Pt-Au-Cu mineralization, disseminated throughout the intrusion. The mineralization consists of chalcopyrite and bornite and their alteration products digenite and covellite, electrum (Au-Ag alloy), Pd-As, Pd-Sb, Pd-S, michenerite (PdBiTe2) and sperrylite (PtAs2). A common host rock is olivine gabbro and the silicate minerals are generally fresh. The mineralization is considered to be primary magmatic for a number of reasons, foremost of which are (i) the clear association of the PGMs with intercumulus (magmatic-textured) fresh or relict Cu-sulphides and (ii) a continuum in Pd/Pt, Cu/Pd, and Cu/Pt ratios from background to mineralized samples which strongly suggests that the processes responsible for the enhanced PGE content of the Bucknalla Complex were also responsible for mineralization. In as much as the former must have been produced by magmatic processes it is concluded that the higher grade PGE-Cu-S mineralization was also caused by primary magmatic processes. A model is proposed in which mineralization is sporadically generated by influxes of small batches of PGE-rich S-undersaturated magma into a magma chamber in which the resident magma has reached S-saturation due to fractional crystallization processes. Other intrusions in the region, namely; the Eulogie Park Complex, the Fred Creek intrusion and the Boogargan intrusion, are not considered prospective for stratiform PGE mineralization due to their low background PGE tenor, low Pd/S and Pd/Se ratios and high S contents.
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    Leachate chemistry of two modern municipal waste landfills in Melbourne, Victoria
    Strudwick, Darryl Grant ( 1999-11)
    This study investigates the occurrence and chemical composition of leachate at Clayton South and Brooklyn Municipal waste landfills in Melbourne, Victoria. Both are ‘modern’ municipal waste landfills, being engineered and managed consistent with current regulatory requirements. These landfills accept only putrescible and solid inert waste, but not soluble chemical, hazardous, liquid or prescribed industrial waste. (For complete abstract open document) Analyses of an extensive range of chemical parameters reveals a complex mixture of inorganic and organic compounds, similar to those of international authors researching leachate chemistry. Dominant ions in these leachates are NH4+, Na+, HC03- and Cl-. Except for Fe, heavy metals are not present in significant concentrations (mostly
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    Detection of uranium(VI) in groundwater using a field electroanalytical technique
    Dwyer, Athene Tracy ( 1999)
    In this thesis electroanalytical methods are investigated and a new method developed to determine uranium(VI) in groundwater samples. Differential pulse polarography, differential pulse voltammetry and adsorptive stripping voltammetry methods, with appropriate mercury drop electrodes, were optimised using the adsorptive chelate 2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone (chloranilic acid). An alternative adsorptive stripping voltammetry method, with a hanging mercury drop electrode, was optimised using the chelate 8-hydroxyquinoline (oxine). The liquid mercury requirements of these techniques limit their use in the field. Therefore, mercury film electrode methods that are potentially better suited to field conditions are investigated. Chloranilic acid was found to be a suitable chelating agent for uranium determination in combination with a hanging mercury drop electrode, but the reduction of chloranilic acid was a concern. A new mercury film electrode determination method using chloranilic acid was developed but was found to result in the deterioration of the MFE to the extent of rendering the method unsuitable for uranium determination. An adsorptive stripping voltammetry, MFE method with oxine was investigated. The inability to remove the uranyl-oxine reaction products from the MFE created a memory effect that contributed to a lack of accuracy and precision when performing standard addition determinations. This interference was a significant factor in the inability to reliably measure a uranium response using an adsorptive stripping potentiometry method with oxine. The technique of square wave adsorptive stripping voltammetry with oxine in combination with a hanging mercury drop electrode was found to be the most appropriate method for uranium determination. The method was fast, sensitive, precise and accurate when analysing standard solutions. A low detection limit of 2.7 µg/L was achieved. Groundwater and surface water samples were analysed by the AdSV, HMDE method with oxine. The mineral spring water samples from Daylesford, Victoria, were high in ionic content and contained interfering ions. The unacidified samples contained high concentrations of dissolved C02 that needed to be removed prior to sample analysis to prevent pH changes during analysis. Of six unacidified samples uranium was found in only one sample, the Tipperary Spring sample at 4.9 µg/L U(VI). Interference prevented confirmation of this concentration in the acidified Tipperary Spring sample. The construction of a linear standard addition plot with a positive x-intercept was a common outcome for both the unacidified and the acidified spring samples. The uranium concentration was determined in three surface water samples collected from the Ranger Uranium Mine in the Northern Territory. Matrix interference in these surface water samples resulted in non-linearity for two standard addition determinations. A third sample was successfully analysed to give a concentration of 23 µg/L U(VI), which is in good agreement with an independent determination. The unselective nature of oxine was found to result in significant interference when analysing environmental samples by the AdSV, HMDE method with oxine. This method was found to be inappropriate for field analysis of environmental samples. However, in a laboratory environment the AdSV, HMDE method with oxine was the best performing method when determining uranium in standard solutions.
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    Occurrence of nitrate in soil and groundwater in the Corangamite area, Western Victoria
    Bayne, Phillip James M. ( 1996)
    Soil and groundwater samples taken from two areas of different land use in the Corangamite Region, 200 km west of Melbourne, were analysed for nitrate and ammonium, and in some cases chloride. Both sites are located on the Later Newer Volcanics 'stone rises', and groundwater was sampled from nested bores which intersect the shallow unconfined aquifer and deeper semi-confined aquifer at both sites. The Carpendeit site is an area of native Eucalypt forest, and the Purrumbete North site is a pasture for grazing dairy cows. Low concentrations of nitrate (< 1 mgN/L) in groundwater at Carpendeit correspond to low soil nitrate concentrations (< 3 µgN/cm3 ). Higher groundwater nitrate concentrations occurred in the shallow unconfined aquifer at Purrumbete North, (up to 3 mgN/L), but not in the lower semi-confined aquifer, and corresponds to higher nitrate concentrations in soil (1 to 60 µgN/cm3 ). Elevated nitrate concentrations also occurred in groundwater discharge at McVeans Springs, in the range 2.61 to 4.72 mgN/L, and at Ettrick Springs in the range 8.08 to 16.07 mgN/L, greater than the limit of 10 mgN/L for drinking water specified in ANZECC water quality guidelines. Nitrate in soil under the pasture is probably derived primarily from the activity of nitrogen fixing bacteria associated with subterranean clover introduced to the pasture. Soil nitrate distributions suggest intense return of nitrogen in dung and urea occurs at 'camps' locations on the pasture, where cows tend to gather for shelter. Transport of nitrogen to shallow groundwater is stimulated by cracks and channels in the basalt clay soils. Local groundwater flow includes interaction with the many lakes and temporary ponds 'which form in surface depressions at times of high rainfall. The ponds probably serve as an effective nitrate supply in recharge to the shallow aquifer.
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    Late Cainozoic climatic and eustatic record from the Loxton-Parilla Sands, Murray Basin, Southeastern Australia
    Kotsonis, Andrew ( 1995)
    A series of ancient shoreline ridges in the western Murray Basin of southeastern Australia preserve a detailed legacy of Pliocene marine retreat. The 157 subdued NNW trending coastal ridges of the Loxton-Parilla Sands, mapped using conventional techniques and night-time thermal imagery from the NOAA and the ERS-l satellites, extend in a parallel series from 400 km inland to the present coastline, and provide a virtual contour plan of the Pliocene landscape. Coastal ridges of the Loxton-Parilla Sands range in age from 6:6 Ma in the east, to 3.5 Ma towards the west, where they are tectonically deformed by the uplift of the Pinnaroo Block. The deposition of the Loxton-Parilla Sands at 6.6 Ma is correlated with high global sea levels, with the distribution of the sands suggesting deposition at a topographic level comparable to an ice-free earth (i.e. complete deglaciation of the polar regions). Coastal ridges consist of beach-barrier and near-shore sediments deposited in conditions of fluctuating sea levels. The absence of aeolian sediments within the ridges implies a significantly weaker wind-wave regime and/or permanent vegetation cover existed throughout the Pliocene. Eustatic oscillations recognized within the shoreline sequence correlate well with glacio-eustatic changes modulated by the axial precession of the earth with a periodicity near 20, 000 years. Following retreat of the sea, the Loxton-Parilla Sands were subject to deep weathering, with the resultant profile termed the Karoonda Regolith. Following cessation of coastal deposition the Karoonda Regolith developed diachronously, with the oldest pedogenic exposures in the east to the youngest towards the west. Ferric and silicic weathering profiles developed in late Miocene to Plio-Pleistocene times. Pedogenic silcretes formed by downward movement of acidic soil waters with saturation and deposition at the soilwater-groundwater interface under alternating wet and dry conditions. High water tables probably ensured accumulation of silica in the near surface environment. By the Mid Pliocene (3.5 Ma) weathering changed from predominantly silica to iron mobilization with development of ferricrete profiles. Late Pleistocene (0.7-0.4 Ma) ferricrete development ceased when arid climates developed as represented by calcareous soils across the basin. Addition of calcareous parna on the Karoonda Regolith buffered soil water pHs, and switched off ferricrete development. Extensive opaline silica dissolution under alkaline conditions resulted in the development of karstic-type solution pipes that were infilled with pisoliths and clasts of sandstone. Lowered groundwater tables probably contributed to the removal of silica from the near-surface permitting transfer to deep aquifers within the Loxton-Parilla Sands. The change from ferricrete to calcrete formation marks the onset of arid climates in Australia. Correlatives can be drawn between this continental record of sea level changes with those of the deep sea oxygen isotope curves which reflect Milankovitch-type changes in the ice budget of the world.