School of Earth Sciences - Theses
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ItemInvestigations into diamond drilling and rock drillability: microscale and fullscale impregnated bits( 1980)Drill bits having cutting edges formed of a matrix of sintered metal powder impregnated with diamond bort (the so called "impregnated" diamond bits) have the potential to greatly increase the economy of diamond drilling, due to low production costs and long bit life resulting from reconditioning of the cutting edges. However, little detailed research into the performance of impregnated bits has been conducted, and the capacity to predict their field behaviour is limited. As a contribution to the knowledge of impregnated bit performance, this project has studied basic relationships between thrust, rotational speed and the penetration of diamond bits into rock, with particular attention paid to the development of techniques suitable for laboratory testing using miniature impregnated bits. A conventional bench drill and a radial arm drill were modified and instrumented to enable operating conditions to be controlled and drilling parameters to be measured and monitored, for microscale and fullscale drilling using impregnated drill bits. Bit performance and drilling characteristics were studied for four rock types, and rock drillability studies were carried out on seven rock types. Statistical relationships between penetration rate, specific energy, torque and drilling distance that were determined enable projection of drilling data from a standard "sharp" condition. A wear measuring device was developed to assess matrix wear of the impregnated microbits. Reconditioning was done by drilling medium-strength, abrasive Stawell sandstone. Initial penetration rate increases linearly with increases in thrust and/or rotational speed, but only within a limited range, depending on rock type and the other operating parameters. Matrix contact with the rock surface, "clogging" of the diamonds, time-dependency, and strength of diamonds and the diamond-matrix bond play important roles in these phenomena. Comparison of rock drillability between that of microscale and fullscale bits shows a straight-line relationship indicating the possibility to predict drilling performance in the field. Uniaxial compressive strength, tensile strength, and Sklerograf hardness can be used as a preliminary, but not reliable guide, to predict drillability. Petrographic characteristics and the relative scale of diamond size to grain size of minerals affect rock drillability.
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ItemThe major, trace and precious metal geochemistry of some Permian layered intrusions, Central Queensland( 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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ItemThe nature of the Kapai slate formation and its role in the genesis of gold mineralisation at the Victory gold mine, Kambalda, Western Australia( 1989)Oxide banded iron-formation-hosted gold deposits account for 12.8% of the gold production from greenstone belts in the Yilgarn Block of Western Australia, but rarely occur in the Kambalda-Kalgoorlie area. Western Mining Corporation initial observations indicated that gold mineralisation at the Victory Mine, Kambalda, Western Australia, although part of a much larger mineralised system, was in some way spatially related to an unusual magnetite - rich variant of the Kapai Slate Formation, but little was known on the nature of the Kapai Slate and its role in the genesis of gold mineralisation at the Victory Gold Mine. The Victory Gold Mine consists of an Archaean vein-associated system hosted in a complexly deformed, subvertical segment of the Кapai Slate Formation, intruded by quartz albite dykes. The veins cut all rock types, and wall-rock alteration is restricted to the siliceous magnetite argillite. The Kapai Slate Formation is a persistent, thin (≤ 10 m) regional marker horizon representing a major hiatus between two volcanic events; the Devon Consols Basalt Formation and the overlying Paringa Basalt Formation. These rocks form part of the mafic-ultramafic sequence of the Kalgoorlie Group which is overlain by felsic volcanic and sedimentary rocks of the Black Flag Group. Five sulphide and oxide bearing lithofacies are recognised within the Kapai Slate Formation; i) siliceous magnetite argillite, ii) siliceous pyrrhotite argillite, iii) carbonaceous pyrite argillite, iv) magnetite chert and v) sulphide chert. The argillites are typically thin-bedded (< 10 cm) and contain more than 15 wt% iron of sedimentary origin. The Victory Deposit is hosted by siliceous magnetite argillite but there is no correlation of lithofacies distribution with structural features. Oxygen isotopic composition of the Kapai Slate Formation lies between 9 o/oo to 12 o/oo indicating a strong depletion compared to Precambrian chert ( ≤ 20 o/oo) and recent marine chert (≤ 36 o/oo). These data together with other geologic data indicate that the magnetite facies is not the result of gold-related hydrothermal alteration but may be the result of both seafloor alteration and metamorphism. The Kapai Slate Formation is compositionally and mineralogically different from other Archaean Banded Iron Formations. The Kapai Slate has high Al, Ti, Na, V, Cr, Zr and Ga, low Ti/Zr ratios, and contains zircons derived from a pyroclastic air-fall tuff (Claoue-Long et al., 1988). The nature of the Kapai Slate lithofacies is interpreted to represent a primary facies variation formed in a deep water sedimentary basin during a hiatus in volcanic activity. It may initially have been composed of both air-fall and water-borne detritus derived from a felsic volcanic source as well as chemical precipitates (sulphide and oxide). This material was totally pseudomorphed and/or replaced by silica, sodium and iron minerals during prolonged exposure on the sea floor. The only elements unaffected by the replacement process were immobile elements such as Al, Ti, Zr, Cr and V. Potassium, Mg and Ca were mobile to a certain extent during the replacement process and the chalcophile elements Cu, Co, Zn, etc. were added to the argillite as chemical precipitants along with S. At the Victory Gold Mine three types of vein sets are recognised: i) ribbon veins, ii) subvertical veins and iii) flat lying quartz veins. However, only the flat lying quartz veins are related to gold mineralisation. The mineralised veins which formed during one episode of open/space filling cut all rock types. Pyritic alteration envelopes of the vein walls are restricted to the siliceous magnetite argillite. Magnetite layers are seen to be deformed by earlier deformations and cut by all vein sets. The development of the pyritic alteration envelopes began with the infiltration of hydrothermal fluid into open fractures resulting in the sulphide replacement of magnetite. Sulphide replacement of magnetite led to the mimicking of the primary layering of the siliceous magnetite argillite. Sulphidation of the vein walls ceased before filling of the veins. After the development of pyritic alteration envelopes, mineral coatings of actinolite and albite formed along the vein walls and later bulk quartz deposition filled the vein openings. The paragenetic sequence consists essentially of a concomittent deposition of pyrite, chalcopyrite, sphalerite, galena, tellurobismuthite and gold. Gold, chalcopyrite, sphalerite, galena, molybdenum and tellurobismuthite were subsequently remobilised into fractures and along grain boundaries of pyrite during a postfilling episode of deformation. The Kapai Slate Formation and the distribution of lithofacies had no influence on the localisation of gold mineralisation at the Victory Gold Mine on a regional scale. However the competent and the more iron-rich nature of the siliceous magnetite argillite probably acted as an efficient chemical and structural trap for the hydrothermally donated S and Au.
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ItemOccurrence of nitrate in soil and groundwater in the Corangamite area, Western Victoria( 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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ItemStructural geology of the area between Bacchus Marsh and Blackwood( 1968)Scope of study: This thesis is concerned primarily with the structural geology of the Ordovician basement rocks along the Lerderderg River Gorge and its two main tributaries. Deformation of the Ordovician rocks constituted the fundamental interest that led to the detailed study of structural elements at various scales. Fabric diagrams were widely used in structural of macroscopic structures. Micro-fabric analysis was not applicable because of low grade regional metamorphism and the fine texture of the rocks. A computer programme used in the preparation of the various fabric diagrams greatly increased the efficiency and accuracy of the study of the structural geometry and symmetry of the deformed Ordovician rocks. A brief description is given of the Permian glacial deposits, the Cainozoic alluvial deposits, the Older and Newer Basalts, the quartz veins, and the different types of dykes.
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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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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.