School of Earth Sciences - Theses

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    Investigations into diamond drilling and rock drillability: microscale and fullscale impregnated bits
    Siribumrungsukha, Boonsom ( 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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    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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    The platinum-group element geochemistry and petrogenesis of the Heazlewood River mafic-ultramafic complex, Tasmania
    Peck, David C. ( 1990)
    The Heazlewood River mafic-ultramafic complex (HRC) comprises well-layered olivine- and orthopyroxene-rich cumulates, gabbronorite dykes, tonalites and low-Ti tholeiitic basalt and boninite lavas. The complex was emplaced as part of a large, low-angle thrust sheet during the middle Cambrian and subsequently deformed during the Devonian, so that the original stratigraphical relationships are obscured. The cumulate succession incorporates two distinct blocks, viz. the western HRC, comprising primitive adcumulates, and the eastern HRC, consisting of more evolved orthocumulates and mesocumulates. These two cumulate blocks are interpreted to represent stratigraphically equivalent parts of a single magma chamber. In this scenario, the western HRC represents an axial part of the intrusion where high heat flows, due to repeated injections of primitive magma, promoted the development of a compositionally zoned magma chamber. In contrast, the eastern HRC is believed to constitute a marginal facies of the intrusion, where sidewall cooling caused rapid crystallisation of successive magma additions and inhibited adcumulate growth and the formation of a compositionally stratified liquid column. Results from a detailed study of the mineral compositions and whole-rock geochemistry of the HRC suggest that all of the cumulates and most of the dykes and tonalites were derived from boninitic parental magmas. This hypothesis is substantiated by empirical models which were calculated using both major and trace element approaches. The models also show that the low-Ti basalts (second-stage melts) and boninites (third-stage melts) were probably derived from component-induced progressive partial melting of a MORB-depleted spinel lherzolite source. Partial melting of the refractory mantle source was initiated and sustained by the continued influx of slab-derived Si02-, LREE-, Zr-enriched hydrous fluids. The proposed petrogenetic model for the HRC is most consistent with an island arc setting for the complex, with melting occurring in MORB-depleted forearc lithosphere overlying a subduction zone. The HRC is not an ophiolite sensu stricto, despite the fact that it is more similar to the upper portions of the so-called 'island-arc ophiolites' (eg. Troodos) than to any other type of ultramafic intrusion. It is best perceived as a high-level boninitic magma chamber which developed immediately beneath a platform of genetically-related submarine lavas. The composition of the boninitic parental magmas was the principal control on the PGE geochemistry of the cumulate sequences. Despite representing PGE-enriched, S-undersaturated second-stage melts similar to the parental (U-type) magmas for the ultramafic portions of the Bushveld complex, the boninites were unable to form a Merensky-reef type PGE deposit because they did not come into contact with S-saturated (A-type) magmas. In the absence of cumulus sulphides, the PPGE (Pt, Pd, Rh) were partitioned into the residual liquids, whereas the IPGE (Os, Ir, Ru) were strongly fractionated into early-formed olivine-chromite cumulates. These features are highlighted by the extremely low IPGE tenor of the boninites, and the relatively high IPGE tenor of the dunites in comparison to the more evolved cumulates. Three types of chromitites are recognised in the HRC. Type I and type II chromitites occur as magmatic schlieren which probably formed during replenishment events. Type III chromitites occur as layers, pods and irregular patches developed in an unusual xenolith-bearing plagioclase peridotite. It is interpreted to have formed due to mixing between ascending xenolith-bearing, hydrous intercumulus liquids and resident ultramafic magma along the floor of the magma chamber. Chromitite occurrences in the HRC are enriched in PGE by up to two orders of magnitude relative to their ultramafic host rocks, and most strongly-enriched in Ru and/or Pt and Rh. Their PGE tenor reflects the early crystallisation of laurite, followed by Pt and Rh sulpharsenides, in response to increasing S and As activities which developed primarily due to magma mixing. The low Os and Ir abundances in the chromitites is believed to reflect their formation from Os- and Ir-depleted boninitic magmas. The HRC and the Adamsfield complex were the world's major suppliers of Os-Ir-Ru alloys during the early part of this century. The alloys occur in alluvial deposits that are spatially associated with primitive olivine-rich cumulate sequences. The latter are commonly suspected to represent the source for the alloys, but recent exploration programs have yet to define a bedrock occurrence of Os-Ir-Ru alloys in Tasmania. The results from the present study provide important constraints on the genesis of these alloys. Silicate inclusions found in the alloys suggest that they formed at mantle temperatures and pressures and were transported to crustal magma chambers by boninitic magmas. The alloys may have crystallised during ascent, or alternatively, represent residual mantle phases which became incorporated into the boninites during partial melting. Most of the observations pertaining to the Os and Ir geochemistry of the HRC suggest that the alloys probably occur in thin magmatic concentrations that were deposited along the base of the intrusion from the most primitive of the boninitic magmas involved in the generation of the cumulate sequences. Future exploration should focus on delineating the cumulate products of these primitive magmas and specifically, in defining the horizons which demarcate fresh influxes of these liquids.
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    Studies in Victorian Tertiary foraminifera neogene planktonic faunas
    Mallett, Clifford William ( 1977)
    Planktonic foraminiferal faunas are described for the interval late Early Miocene to the Pleistocene, in the Tertiary basins along the southern margin of Victoria, including the Otway Basin, the Port Phillip Embayment, and the Gippsland Basin. Ninety-two foraminiferal taxa are identified. The faunas are dominated in the Early Miocene by globigerinid and globigerinoidid species, by unkeeled globorotalids in the Middle Miocene, and by keeled globorotalids for most of the Late Miocene. Unkeeled globorotalids are again important in the Early Pliocene, but keeled species again reappear in the Late Pliocene and the Early Pleistocene. One Pleistocene, two Pliocene, two Late Miocene, and two Middle Miocene planktonic foraminiferal zones are recognised on the first appearance of the following species: Orbulina suturalis, Globorotalia mayeri, Globorotalia acostaensis, Globorotalia conomiozea, Globorotalia puncticulata, Globorotalia viola, Globorotalia truncatulinoides. Subzones are identified by the extinction of Globorotalia peripheroronda, and by the appearance of Globigerina nepenthes and Globorotalia plesiotumida. Foraminiferal datum levels are used to correlate the Victorian sections with the Italian stratotype sections, the New Zealand late Tertiary, and the N-zonation of Blow, and hence into the palaeomagnetic and radiometric time scales. In the Tertiary basins, the maximum extent of marine deposition occurred in the Early Miocene, and despite subsequent sea level falls, continuous marine deposition is found through the Middle Miocene and most of the Late Miocene in the Otway Basin and the Port Phillip Embayment. Shallowing within the Middle Miocene is reflected by breaks in the Gippsland Basin sections, and lithological changes in other basins. A major sea withdrawal occurred near the top of the Miocene. Small scattered Pliocene deposits indicate short high sea level phases at the base of the Pliocene, in the middle of the Pliocene, and about the Pliocene - Pleistocene boundary.
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    Altitudinal distribution of vegetation in the headwaters of the Wongungarra River, Victoria
    WATSON, FRED ( 1993)
    Changes in vegetation composition with respect to altitude were investigated in the sclerophyllous forests of the Australian mountain region. Vegetation was surveyed at 148 sites along two transects which were located to maximise variation in altitude and minimise the influence of environmental factors not directly related to altitude. The measurement, simulation, and estimation of environmental variables revealed that this aim was met except at the end-points of the transects where secondary influences are present.
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    Mineralogy, geochemistry and origin of the Kalgoorlie gold deposits, Western Australia
    Golding, Lee Yvonne ( 1978)
    Rich gold-telluride lodes (steeply dipping and flatly dipping) and minor gold-quartz stockwork mineralization characterize the Kalgoorlie gold-field. The origin of these gold deposits, the relationship between deposits and then nature of the host rocks are the major problems considered in this thesis. Extensive diamond drilling at the essentially unmineralized southern end of the field provided excellent material for stratigraphic studies and for country rock analysis whilst ore samples were obtained from both mines and drill core.
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    Australian lineament tectonics: with an emphasis on northwestern Australia
    Elliott, Catherine I. ( 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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    Recent glacier and climate change in the New Zealand Alps
    Ruddell, Andrew Reginald ( 1995-07)
    The sensitivity of glaciers in the Southern Alps of New Zealand is evaluated to identify the nature of recent climate change. Past glaciological observations are compiled and to these are added 4 summer field seasons on the Tasman (including Hochstetter), Dart, Fox and Franz Josef Glaciers. The field data are an important aspect in the calibration and verification of glacier modelling. The detailed studies of these glaciers provides the basis for assessing the glacier and climatic changes over the whole glacierized region. (For complete abstract open document)
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    The Permian glacial sediments of central Victoria and the Murray Basin: their sedimentology and geochemistry
    O'Brien, Philip Edward ( 1986)
    This study investigates the sedimentology and geochemistry of Permian glacial sediments cropping out in the Bacchus Marsh and Derrinal areas in central Victoria and in the subsurface beneath the Cainozoic Murray Basin in Victoria, New South Wales and South Australia. Facies analysis of the Bacchus Marsh Formation, based on a critical review of literature on glacial sedimentary processes and environments, identifies the following major facies groups: 1. Subglacial tillites deposited beneath wet-based ice. Some of these tillites exhibit structures indicative of a number of subglacial processes such as frictional lodgement of large clasts, subglacial bed deformation, subglacial meltwater flow and subglacial size sorting of clasts. Other subglacial tillites are essentially structureless. 2. Bedded diamictites to sandstones deposited predominantly by ice-rafting of debris into standing water. 3. Fluvial outwash sandstone and conglomerate facies that are finer-grained than typical proglacial outwash facies. 4. Deltas and subaqueous outwash fans vary from sandy sediments deposited by proglacial and subglacial streams to coarse, poorly sorted complexes deposited as debris aprons close to the ice front. Abundant underflow deposits suggest that less than normal marine salinities prevailed in these water bodies, even if they were arms of the sea. 5. Supraglacial tillites consisting of sandy diamictites to pebble conglomerates. Facies in the thickest sequence in the Bacchus Marsh area suggests that the area was covered by a major ice mass at least 8 times. Minor glacial advances took place during predominantly ice-free periods. The Derrinal Formation consists of a basal unit of predominantly subglacial tillite deposited in shallow glacially excavated valleys overlain by a complex of subglacial and supraglacial facies deposited by about 8 minor advances of a small ice tongue. Facies relationships in this part of the sequence are confused by intense deformation of the sediment pile during the melting of buried ice and dewatering of saturated diamictons. A major ice advance then overwhelmed the area depositing thick subglacial tillite. The Urana Formation, beneath the Murray Basin, is dominated by marine ice-rafted diamictite and mudstone. Rhythmically bedded siltstone and claystone, sediment gravity-flow deposits, traction-current deposits, and, possibly, subglacial tillites are also present. Facies assemblages in some drill holes indicate areas that were never covered by grounded glacial ice. Sedimentological and palaeontological evidence suggests that the Urana Formation was deposited towards the end of the glaciation. Ice motion indicators and ice sheet limits inferred from the facies assemblages in the Urana Formation are used to estimate the thickness of the ice over central Victoria during glacial maxima. These estimates support the conclusion drawn from the facies analysis that the ice was a large ice sheet. Comparisons of ice movement directions for central Victoria and formerly adjacent parts of Gondwana suggest that a large ice sheet was centred in North Victorialand. Major and some trace elements analyses of the clay component of marine and non-marine diamictites were used to test a number of methods of distinguishing marine from nonmarine glacial diamictites. None of the methods were clearly successful because sediment detrital mineralogy dominates the geochemical composition though V/Cr ratios may be useful in some circumstances.
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    The nature of the Kapai slate formation and its role in the genesis of gold mineralisation at the Victory gold mine, Kambalda, Western Australia
    Cotnoir, Alain ( 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.