School of Earth Sciences - Theses
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ItemAustralian lineament tectonics: with an emphasis on northwestern Australia( 1994-08)Australia is transected by a network of systematic continental-scale lineaments that are considered to be zones of concentrated, aligned tectonic activity which have apparent continuity over vast distances. The influence of lineaments on the rock record can be identified in many types of data-sets, and existing data reveals previously undescribed basement influences. Several continental-scale lineaments can be traced offshore with apparent continuity for hundreds to thousands of kilometres, two of which are seen to cross the Tasman Sea in offshore eastern Australia. Geological and chronological evidence demonstrates that many of the lineaments have been zones of reactivation since at least the Early Proterozoic (- 1880 Ma) and that they appear to cross major terrane boundaries. Alternative models for their origin are a) a pre-existing lineament network maintained in an ancient basement underlying the entire continent; b) lateral propagation of crustal-scale structures; c) alignment of genetically unrelated lineaments giving the appearance of continuity. Australian deep-seismic profiles show that continental-scale lineaments are zones of crustal-scale structure which in some cases transect the crust-mantle boundary. Lineaments demonstrate many faulting styles, e.g. listric extensional (G3), planar moderate-angle thrusts (G2 l), and sub-vertical thrusts (G 17). In some cases the structural style varies laterally along the length of the lineament. (For complete abstract open document)
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ItemGeochemistry and mineralisation of primary and secondary platinum-group elements in the ultramafic "Alaskan-type" Owendale complex and laterites in the Fifield Region, New South Wales, Australia( 1995)The Owendale Complex belongs to a family of ultramafic-mafic intrusions that is characterised by a zonal, nonstratiform arrangement of the principal ultramafic units. The ultramafic rocks of the Owendale Complex are virtually identical to many of the Alaskan-type intrusions, however the associated gabbroic rocks (wehrlites) are K-rich and Si-undersaturated, in contrast to the tholeiitic gabbroic rocks of the Alaskan examples. The intrusion history of the Owendale Complex is thought to have involved emplacement of a gabbroic intrusion that was invaded by an ultrabasic magma, possibly while the former was still only partly solidified. Emplacement of both magmas probably occurred during Late Devonian tectonism and deformation synchronous with emplacement and crystallisation is necessary to explain the present non-stratiform arrangement of the rock units. The most obvious linkage factor between the two proposed parent magmas (gabbroic and ultrabasic) of the Owendale suites is their mutual affinity with tholeiitic basalt magmas and the similarities of their products with intrusions of alkalic basalt derivation. This suggests the possibility that the Owendale Complex rocks and those of other tholeiitic intrusions of the regions are comagmatic products of an ancestral magma that may have also produced the widespread assemblage of complexes. Viewed from this perspective, the ultramafic rocks of Owendale Complex would thus represent a very minor product of a period of regional magmatic activity. Most alloys, erlichmanite, cooperite and some grains with exclusion texture of Pt-Os-Ir-Pd-Rh are considered to represent a primary high-temperature paragenesis. Concentration of PGE in pegmatoidal units of dunite-wehrlite is explained by the accumulation of platinum-rich alloys that segregated directly from the melt at an early stage in the evolution of the complex. The high-temperature PGM segregate directly from a silicate melt and were not generated by exsolution from spinels or magmatic sulphides. These suggest that fS2 was generally low (subordinate sulphide formation) and, after some influence at the beginning, has given way to rising fO2 (chromite, olivine and Pt-Fe-Cu-Ni alloys formation). After lithification, the ultramafic rocks become subject to "reducing" conditions, i.e., conditions of lower O2 and S2 activities. Ni-Fe alloys, native Fe and Bi formed in cracks which filled the serpentine matrixes. The former PGM (erlichmanite, cooperite and Pt-Fe alloys) were exposed to the reducing conditions via cracks were desulphurated to form porous cooperite with Pt-Fe alloys and multiphase textural Os-Ir-Ni, Pt-Ir aggregates. It is plausible that the veinlets and aggregates of unnamed Rh-Sb-S, (Pt, Ir)2(Fc, Cu)3(S, Sb, AS)3 in the dunites may also have been formed by reduction of Ni-rich sulphides and erlichmanite, Pt-Fe alloys or cooperite. Late PGM are dominated by sperrylite-geversite solid solution resulting from the reaction of early PGM with a fluid phase. A hydrothermal origin is also indicated for native Fe, native Bi and awaruite (NiFe) and the base-metal sulphides (pentlandite, chalcopyrite, sphalerite, arsenopyrite, pyrite, pyrrhotite, and some Ni-Co-Fe sulfide). The cause of the reducing conditions may have been related to H2 production accompanying hydrous alteration of the dunites and clinopyroxenites. The laterites overlying the ultramafic complexes in the Fifield region are exceptionally well-developed and well-preserved weathering profiles. Field, textural and geochemical data all support a chemical weathering origin for the profiles and compatible with meteoric and ground water origins. Meteoric water with intermediate Eh and pH and negligible dissolved species sinks into the laterite where these parameters are modified. The Eh rises and pH decreases to the conditions typical of lateritic soils and the concentration of dissolved species increases. In this state the water is able to take PGE and Au into solution from a finely disseminated form in the bedrock as a part of the process of lateritisation. When the soil solution transports the PGE and Au towards a transitional interface must exist between the ferruginous and saprolite zones with lower Eh, neutral pH and lower concentration of dissolved salts. At this transitional region, deposition of the PGE and Au occurred. The presence of magnetic Pt-Fe-Cu-Ni alloys suggests that hydrothermal solutions play a later role in the Fifield region, and the alloys have grown in situ in a lateritic soil by a process involving laterite water solution in the high Eh, low pH conditions prevalent in such soil, followed by deposition when the conditions become less extreme. Some examples of the Pt-Fe alloys from such an environment become frequently strongly magnetic with larger size. It is assumed that the temperature of the hydrothermal solution is in the range of 300° - 500° C (Bowles, 1990). PGE mineralisation in the primary rocks and laterite in this region has demonstrated a good example of multi-stage process mineralisation including primary high temperature magmatic formation; low temperature postmagmatic hydrothermal alteration and residual lateritic enrichment.
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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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ItemThe geology of the Pyramid and Tonghi Creek areas, East Gippsland( 1984)A study of the geology of the Club Terrace region is being undertaken with two major aims: 1) to provide a clearer picture of the structural geology and geological history of the region and, using this, 2) to investigate Ag, Cu, Pb, and Zn mineralization present in the region with emphasis on producing a model for ore genesis.
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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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ItemMobility of base metals through regolith, Broken Hill, N.S.W.( 1993)Regolith profiles over and around zones of Pb-Zn mineralisation were investigated at Maybell and Stirling Vale, located in the Broken Hill region, N.S.W. Metasediments and metavolcanics of the Proterozoic Willyama Supergroup crop out in the study areas, with quartz-gahnite horizons hosting mineralisation. Desert loam soils in the study areas have a transported origin. Locally transported sheetwash deposits overlie a relict aeolian deposit which sits on relatively fresh Proterozoic bedrock. Mineralogy of the regolith profile is consistent with depth and landscape position. Quartz-gahnite horizons form topographic highs in both areas, containing up to 13.5% Zn. Gossanous material is associated with the quartz-gahnite rocks. No base metal containing secondary minerals were present in this weathered material but there were high proportions of iron oxides containing substantial amounts of base metals. Surrounding soils were anomalous in Zn, Cu and their pathfinders Cd and As, which outlines a mobilisation of base metals. Similar anomalies were expressed in stream sediments. Calcrete in the area, contained no anomalous levels of Zn, due to the low solubility of Zn at high pH. The majority of base metals in soils were associated with amorphous iron oxides and silicates (presumably gahnites). These metal bonding sites indicate, dispersion haloes in the regolith are due to a combination of physical and chemical dispersion. In this example of transported regolith profiles in an arid terrain, Zn and Cu are both physically and hydromorphically dispersed from weathering quartz-gahnite horizons.
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ItemThe geology, petrology and geochemistry of the Otway formation volcanogenic sediments( 1983)The geology, petrology and geochemistry of the Early Cretaceous Otway Formation have been investigated in detail and used to determ ine the nature of the source rocks and to develop a model for the diagenetic and low-grade metamorphic readjustments. The fluviatile Otway Formation was deposited in continental rift grabens that stretched some 1000 km along the southern coast of Australia during the Early Cretaceous. The main areas of deposition in the Otway, Gippsland and Bass Basins contain an estimated 100,000 cubic kilometres of detritus. The major part of this detritus was derived from pyroclastic material which has been shown by the fission track dating studies to have been derived from contemporaneous volcanism. The pile of volcanogenic material comprising the Otway Formation is at least 3 to 4 km thick in the main basins. The sediments are entirely non-marine and were deposited by large scale multichannel streams cut in extensive floodplains. The streams deposited thick multistorey channel sandstones in sheet-like bodies and a diverse spectrum of overbank mudstones and fine-grained sandstones. The complex channel sandstones fine upwards but have numerous erosional breaks indicating repeated flood cycles. Whereas the channel deposits have internal features consistent with braided stream channels the overall system has a large proportion of floodplain which was been considered in the past to have been a feature of meandering channels. The oversupply of volcanogenic detritus is considered to have been responsible for the development of the multiple channel depositional system in a climate of high seasonal rainfall. Whole rock chemical analyses of all lithologies in the sedimentary suite, recalculated i.nto a set of normative minerals, have proved useful in the distinction and description of sedimentary rocks in general. P20S was found to be useful for the identification of Early Cretaceous soil forming processes. The study of the chemical composition of detrital minerals has demonstrated the usefulness of this approach in the identification of the nature of the source magmas of volcanogenic sediments. For the Otway Formation, analyses of clinopyroxenes, amphiboles, feldspars and sphene in particular, have shown that high potassium dacitic to shoshonitic volcanism dominated during Early Cretaceous rifting. The new data on the geology and mineralogical and chemical features of the Otway Formation have application to the study of diagenesis and low-grade metamorphism in volcanogenic sediments in general. (From Abstract)
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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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ItemLate Cainozoic climatic and eustatic record from the Loxton-Parilla Sands, Murray Basin, Southeastern Australia( 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.
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ItemNo Preview AvailableThe geology and petrology of the Lower Devonian Buchan Group, Victoria( 1981)This study is devoted to a detailed examination of the stratigraphy and petrology of the late Lower Devonian (Emisan) Buchan Group, an essentially carbonate sequence. The Buchan Group begins with the lenticular Spring Creek member of the Buchan Caves Limestone. This consists of terrigenous clastic sediments derived from erosion of the underlying Snowy River Rhyodacites. Lithologies range from conglomerates and breccias with rhyodacite pebbles, through arkosic sandstones to quartz sandstones and shales. Pyroclastics, previously identified in this unit, are absent. The Spring Creek member changed from non-marine to marine as the main transgression became established and was followed by a change to carbonate deposition.