School of Earth Sciences - Theses
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ItemLate Paleozoic glaciations of Eastern Australia( 1959)In a re-analysis of the Late Paleozoic glaciations of Eastern Australia, close review of elements of paleogeography results in many new interpretations. New data appear from field studies of the details (including till fabric analyses in the Heathcote District of Victoria) of glacial stratigraphy in drift sequences of Victoria and South Australia. Analysis of sedimentary volumes in Tasmania and analysis of sedimentation during the Upper Carboniferous and Permian of New South Wales and Queensland adds more new information. Field reviews of sequences in the Finke District of the Northern Territory, Tasmania, New South Wales, and Queensland aid in understanding the effects of glaciations in those regions. All data known to the writer from extensive field examinations and review of published data may be incorporated into a unified history of the glacial times. Many lacunae exist, but analogy with studies of Pleistocene glacial drifts helps to bridge some gaps. Principally during the Middle and Upper parts of the Upper Carboniferous and in the Early Permian, highland centers in the northwest of Tasmania (the Macquarie Mountains) and in northeast New South Wales (the Clarencetown Mountains, a volcanic range) became loci for glacial formation and spread. From the former, glaciers spread east, north, and northwest. Upon advancing northwest, the Mt. Lofty-Kangaroo Island Ranges were encountered. These were breached with the establishment of glacial corridors, and a glacial lobe subsequently pushed about 600 miles further north-north-west. In that region, this glacial [?] [?] [?] joined a sheet from Western Australia. Also, in pushing north from the Macquarie Mountains, the glaciers apparently advanced 900+ miles to the Springsure District of Queensland. From the Clarencetown Mountains, piedmont glaciers radiated east (to the sea near Mt. George, Booral, and Limeburner’s Creek), south, and west to fill subsiding basins with glacial deposits and some volcanic effusions. Additionally, some glaciers spread east from the epi-Kanimblan mountains of New South Wales. Thick drift sequences left by these spreading glaciers have been preserved in favourable sites. Fluvial and lacustrine deposits in the drifts demonstrate the presence of interstadial and interglacial conditions, but the entire interval may be considered a single glacial epoch much resembling the Pleistocene, although that of the Late Paleozoic probably was much longer. After wastage of the glaciers, cold weather (at least during winters) persisted, for many phenomena found in the Permian sediments seem best related to climates which were cold at least part of the year. Notable among these are the erratics so widely distributed through the marine Permian sediments of eastern Australia. Such erratics seem best explained as phenomena resulting from the transport by winter ice floes of material eroded from glacial drift left on the land by earlier glaciations.
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ItemGeology of the Dookie District (Part I) & Trace element distributions within some major stratiform orebodies (Part II)( 1973)Part I: The Cambrian rocks outcropping in the Dookie district consist of a series of altered igneous rocks (diabases), a variety of pyroclastic rocks and cherts. The igneous rocks are thought to have been originally tholeiitic, having undergone low grade burial metamorphism, hydrothermal alteration and possibly contact metamorphism. Field evidence indicates that at least one of the igneous bodies is intrusive, probably a sill. The relation between these rocks and Cambrian rocks elsewhere in Victoria is discussed. The lithology and structure of an area of folded Ordovician and Silurian — L. Devonian sediments outcropping to the south of the main Cambrian massif is reviewed. Part II: Trace elements Tl, Ag and Au abundances in whole rock samples from a number of important stratiform basemetal orebodies have been determined by neutron activation analysis. Suites of samples were taken from the HYC Zn-Pb-Ag deposit at McArthur River, N.T., the Cu-Pb-Zn deposit of Rosebery, Tasmania and a Karoko type orebody from Shakanai, Japan. While the distribution of Au and Ag in the three deposits were found to closely follow those of Cu and Pb respectively, a higher Ag/Au ratio is apparent in the HYC deposit. In the other deposits, probably formed at temperatures greater than 200°, high concentrations of Au are explainable in terms of high temperature transport via chloride or thiocomplexing, while in the HYC deposit, formed below 150°, hydrothermal transport of comparable amounts of Au is considered unlikely. In response to lower temperature, strongly reducing conditions and restricted circulation, Tl concentrations in the HYC deposit are markedly greater than those in the remaining deposits. At McArthur River, significant enrichments in Tl occur up to, 250 metres stratigraphically above the main ore shales, and the geochemical significance and practical value of such metal haloes about stratiform orebodies are discussed.
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ItemThe geology and hydrogeology of the Corangamite region( 1971)Tectonic activity after the early Cretaceous resulted in a complete change in the depositional environment in the sedimentary basin - the Otway Basin - located to the south of the Western Highlands of Victoria and to the west of Melbourne. ThiS Basin became subject to increasing marine influences and the sediments deposited include thick sequences of Miocene marls: the Gellibrand Marl. The water in the marls and in the underlying sands of the Dilwyn Formation is saline near Lake Corangamite but elsewhere water of good quality is found in the sand aquifers, indicating that tectonic activity has caused the local isolation of the lower formation from the effects of flushing by fresher groundwater. Continued tectonic activity and associated volcanic activity during the Miocene and Lower Pliocene resulted firstly in the regression of the sea then the development of the internal drainage characteristic of the Corangamite Region. The sea probably retreated to the southeast as indicated by the unusual parallel physiographic features which have influenced the flows of 'earlier' Newer Volcanic lavas in the Curdie River area and the subsequent development of this river's drainage system. These features are probably related to remanent coast strandlines. The quality of the groundwater found in the 'earlier' lavas is generally poor but the basalts and tuffs of the 'later' Newer Volcanic age often contain water of low salinity, particularly in the intake areas which are located in the ‘stony rises' or near the volcanic cones. The intake area water of the Mt. Warrion basalts is a low salinity calcium-magnesium-bicarbonate water, having an unusually high nitrate content. As the salinity of the water increases away from the intake area the chemical nature of the water approaches that of a dilute sea water. This has been interpreted as being the result of a release of 'oceanic' connate salts by weathering of the calcareous material found in the tuffs and scoria beds of the volcanic cones. The material has been derived from the underlying marl sequence and has been incorporated into the igneous rocks during eruption. The high nitrate concentration has been attributed to the effects of pollution, since there is some evidence that the nitrate values have increased over the last sixty years, but there is also probably an increased rate of fixation in the intake area due to the effects of cultivation. The high bicarbonate values are probably due to a high rate of absorption of carbon dioxide from the atmosphere in the intake areas. The hydraulic characteristic of the basalts ensures the rapid distribution at the high nitrate and bicarbonate waters of the intake area over large areas, hence the effects of pollution are more readily noticeable. The groundwater regime plays an important role in the transfer of dissolved salts in the mainly saline water domain of the Corangamite Region. The study of the water and salt content of some of the lakes of the area indicates that a balance exists that results in the maintenance of a specific lake salinity within narrow limits, and in which the groundwater regime is often involved. By considering the salt balance and water balance of a system as one parameter, referred to as the Hydro Salinity Factor, a simple mathematical model can be postulated to determine some of the unknown factors involved in the maintenance of an equilibrium salinity in a lake. The drilling programme and groundwater investigation outlined an important water resource located in the Warrion area. Already 40 bores have been drilled in this area and they produce 6.6 x 105m3 /year (800 acre feet/year). There is an annual underflow of about 1.5 x 107 m3 (12,000 acre feet). This quantity is well within the 'safe yield' of the area and further development should be encouraged, but because of the presence of the large number of saline lakes in the area, saline water intrusion into the basalts would rapidly occur if the groundwater levels are lowered beneath the lake levels.
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ItemGeology of the Wood's Point dyke swarm( 1974)The wood’s Point dyke swarm, Victoria, consists of a set of abundant subparallel narrow dykes with occasional elliptical expansions (“bulges”) intruded into strongly folded Lower Palaeozoic sediments. The swarm represents a hisly differentiated calc-alkaline rock series derived by fractional crystallization of a single parent magma, possibly of periodotitic composition. The rock types present include both high and low Cr-Ni periodotites, pyroxenite, hornblendite, hornblende diorite and monzonite, biotite leucodiorite, and minor residual granophyre. Apart from this hornblende-bearing rock series, a few hornblende-free basaltic dykes of related chemical composition but intruded later, are petrographically and mineralogically distinct, displaying tholeiitic tendencies. The latter dykes appear to be genetically related to volcanics underlying the Upper Devonian Acheron and Cerberean cauldron subsidences. Fractional crystallization, flowage differentiation, crystal accumulation and chilling were important factors in the development of the members of the dyke swarm, whilst assimilation in situ was not. The dykes are zonod, ultramafic types having more basic interiors (“cores”) whereas basic to intermediate composition bulges have more basic margins (“rims”). Magmalic copper-nickel sulphides rich in precious metals (Pt, Pd, Au) occur in dyke bulges of all compositions, especially close to margins where they accumulated by gravitational settling or were trapped by chilling. The sulphides have high Cu/Ni (and Co/Ni) ratios indicative of a highly evolved magma and, along with Au, Pd and Ir are fractionated between dykes of different silicate compositions. The base metal contents of silicates and sulphides vary sympathetically. The dykes have undergone pervasive hydrothermal alteration during which sulphides were largely recrystallised and Au was leached from some copper-nickel sulphides. A zonal arrangement of increasing intensity of alteration inwards was observed in one ultramefic dyke bulge. Later the dykes were deformed and the basic to intermediate composition dykes were fractured and veined, and major gold deposits formed. The veins have associated wall rock alteration which may be mineralogically subdivided into inner and out zones. Dyke bulges, ultramafic rocks, copper nickel sulphides and Au mineralization are all concentrated along two main lineations paralleling the fold axes of the sedimentary trough. The eastern and more important trend (at the centre of the trough) marks the eastern limit of the dyke swarm except at its northern end. These lineations may represent deep-seated fractures which controlled the later upward migration of Au-bearing hydrothermal solutions from depth. The source of the Au could have been various rock types present at depth, including copper-nickel sulphides and Lower Palaeozoic sediments.