School of Physical Sciences
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This collection contains Honours, Masters and Ph.D by coursework theses from University of Adelaide postgraduate students within the School of Physical Sciences. The material has been approved as making a significant contribution to knowledge.
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Item Open Access 1. The geology and petrography of an Archaean inlier, south of Normanville. 2. The origin of the 'Houghton' granulite.(1972) Davies, M. B.; School of Earth and Environmental Sciences, Geology & Geophysics1. Detailed mapping established definite rock units within the Archaean inlier south of Normanville. The distribution of the rock types is suggestive of a major antiformal structure. Only metamorphic layering is recognised in the area. The first Archaean orogeny produced this layering and reached upper amphibolite grade of metamorphism as defined by the minerals sillimanite, garnet, diopside and scapolite. The temperature and pressure conditions were ~750C and 2-3 Kbars. This was established using mineral assemblages and the presence of considerable partial melting, pegmatitic masses and migmatites. This same orogeny was also responsible for the development of a strong schistosity, which was always parallel to the metamorphic layering. A Proterozoic orogeny produced a strong crenulation of the schists. This crenulation is parallel to the fold axis of a major antiform which plunges 35deg to 138deg. The deformation reached biotite grade of metamorphism as shown by the minerals biotite, sericite and epidote, which, commonly replace the higher grade minerals. An antiform overturned to the west was the major structure. Its under limb was sheared away, so that the inlier represents the eastern limb only. The western outcrops of the inlier represent the shear zone. 2. Geochemical analyses of the Houghton granulite suggest a sedimentary origin. This, coupled with its conformability with the surrounding rocks, and its association with a zircon rich meta-quartzite, support this conclusion.Item Open Access The 1300AD dacite pumice eruption, Rinjani Volcano, East Sunda Arc: petrology, petrogenesis and plumbing(2009) Meegan, N. K.; School of Physical SciencesPhysical controls on fractional crystallisation in subduction settings around the globe are the focus of much discussion within academia. It is frequently observed that the typical magma to be erupted in arc settings is andesite from the differentiation of partially melted peridotite mantle wedge. It is less common in these settings to see more felsic end member magmas such as dacite or rhyolite being erupted in cataclysmic events. Discussion has arisen into what physical process or processes can drive a volcano, or set of volcanoes, within an arc to produce dacite or rhyolite magmas where fractional crystallisation is known to be the process of initial crystallisation. Research into these processes can be applied to Mount Rinjani (Lombok) within the Sunda Arc system, where the normally composite andesite volcano produced a cataclysmic eruption of dacite magma known as the Rinjani Pumice at 1300AD. Data is presented here in order to investigate processes within the sub-volcanic magma plumbing at Rinjani, primarily using volatiles from melt inclusions, coupled with petrology, pressure, temperature and water saturation estimates. It is theorised that ascent-driven crystallisation from a parent basalt drove fractional crystallisation to andesite composition beneath Rinjani volcano. Water undersaturated conditions induced ascent of the andesite magma to a shallow reservoir at ~3 kbar at temperatures ~1015 °C, with water saturation ~3.7 weight percent. Melt inclusion data from these same crystals reveals the interstitial liquid in the andesite magma to be of evolved dacite composition (~66 wt % SiO2) compared to the andesite (~50-54 wt % SiO2). Critical crystallinity is the physical process believed to have acted upon fractional crystallisation where the percentage of crystals forming exceeded the ability of the magma chamber to convect within this reservoir and therefore physical separation of the evolved dacite liquid from the andesite magma occurred. The buoyant dacitic liquid ascends to another shallow reservoir directly beneath Rinjani volcano and reaches its saturation pressure at 1.8 kbar at a temperature of ~900 °C, with water saturation increased to ~5 wt %. Sub-plinian cataclysmic eruption of the 1300AD Rinjani Pumice occurred due to pressure increase involved in saturation of the dacite, and syn-eruptive degassing aids in excavating the western flank of the Rinjani stratocone leaving a caldera. Subsequent volcanism occurs where the magma ascent path migrates west producing more cataclysmic eruptions increasing the volume of the edifice. Today, resurgent volcanism can be seen in the central eastern part of Segara Anak lake at Gunung Baru within the Rinjani caldera to produce basalt and andesite lavas. The application of physical mechanisms acting upon fractional crystallisation proposed here may be applied to other arc settings around the globe, where fractional crystallisation is found to be the primary driving force of felsic end member cataclysmic eruptions at what is typically an andesitic arc.Item Open Access 2D lithospheric imaging of the Delamerian and Lachlan Orogens, southwestern Victoria, Australia from Broadband Magnetotellurics(2016) Merrett, H. D.; School of Physical SciencesA geophysical study utilising the method of magnetotellurics (MT) was carried out across southwestern Victoria, Australia, imaging the electrical resistivity structure of the lithosphere beneath the Delamerian and Lachlan Orogens. Broadband MT (0.001-1000 Hz) data were collected along a 160 km west-southwest to east-northeast transect adjacent to crustal seismic profiling. Phase tensor analyses from MT responses reveal a distinct change in electrical resistivity structure and continuation further southwards of the Glenelg and Grampians-Stavely geological zones defined by the Yarramyljup Fault, marking the western limit of exploration interest for the Stavely Copper Porphyries. The Stawell and Bendigo Zones also show change across the Moyston and Avoca faults, respectively. Results of 2D modelling reveal a more conductive lower crust (10-30 Ωm) and upper mantle beneath the Lachlan Orogen compared to the Delamerian Orogen. This significant resistivity gradient coincides with the Mortlake discontinuity and location of the Moyston fault. Broad-scale fluid alteration zones were observed through joint analysis with seismic profiling, leaving behind a signature of low-reflectivity, correlating to higher conductivities of the altered host rocks. Isotopic analysis of xenoliths from western Victoria reveal the lithospheric mantle has undergone discrete episodes of modal metasomatism. This may relate to near-surface Devonian granite intrusions constrained to the Lachlan Orogen where we attribute the mid to lower crustal conductivity anomaly (below the Stawell Zone) as fossil metasomatised ascent paths of these granitic melts. This conductivity enhancement may have served to overprint an already conductive lithosphere, enriched in hydrogen from subduction related processes during the Cambrian. A predominately reflective upper crust exhibits high resistivity owing to turbidite and metasedimentary rock sequences of the Lachlan Orogen, representative of low porosity and permeability. Conductive sediments of the Otway Basin have also been imaged down to 3 km depth southwest of Hamilton.Item Open Access A 3-D gravity and aeromagnetic interpretation of the Black Hill-Cambrai region(1989) Kennedy, R. J.; School of Physical SciencesThe western edge of the Murray Basin overlies Kanmantoo sediments and contains anomalously high and low Bouger Gravity values. From available geological information, the anomalies are due to acidic intrusions, basic intrusions, and thickening of Tertiary sediments. A steeply flanked regional anomaly exists within the area. The anomaly is positive, 50 kilometres wide and has an amplitude of 25 mgals. This feature was modelled as a lopolith 5 kilometres thick with a feeder system extending to 30 km. Previous work in the Black Hill-Cambrai area had been mainly qualitative in nature. Considerable time was needed in order to tie three previous surveys together and form a reliable database. This database was incorporated in the thesis, and further work was done to increase the coverage of the anomaly. Gravity and magnetics results reveal the possibility of three basic intrusions that may be related at depth by a system of dykes. Two of the bodies, which are known as Cambrai and Black Hill, were studied in close detail. The regional gravity gradient needed to be removed and has been done so through the application of polynomial fitting with geological constraints. Attempts were made to define the shape and depth extent of the structures by means of 3-D modelling. It was revealed that the anomalies were possibly due to plumes of basic material with inward dipping walls and also a circular feeder system. Dykes occur around the basic bodies, possibly associated with the feeder system, indicating an extensional regime existed at the time of the intrusions.Item Open Access The 3D electrical structure of the Australian lithosphere(2013) May, A. J.; School of Physical SciencesThe broad-scale electrical resistivity structure of the Australian continent is poorly known due to the lack of continent-wide observations. These observations are used to constrain lithospheric conduction and petrophysical conditions. In this study, models of electrical resistivity are developed using various constraints, and these are tested against known observations. Three approaches have been employed. Firstly, using the AWAGS array of 58 magnetotelluric sites across Australia spaced approximately 500 km apart, I analyse geomagnetic depth sounding induction vector data, which are then compared with the broad-scale tectonic components of Australia. Secondly, I have developed an upper crustal and surrounding ocean model of electrical conductance using ocean depth information (ETOPO1) and depth to Proterozoic basement (SEEBASE) with a spatial resolution of approximately 17 km. Thirdly, estimates of seismic shear wave velocity of the lithosphere from 50 to 200 km depth from the AuSREM data, at a spatial resolution of approximately 50 km, were converted to electrical resistivity using an empirical relationship. The induction vectors were then compared with three dimensional modelling developed through two approaches. To good approximation I have been able to demonstrate, that the observed AWAGS induction vector data are explained to first order by the conduction of the oceans and sedimentary basins. Second-order effects of resistivity variations in the deeper lithosphere are significant, but induction vectors are less sensitive to these. Finally, I demonstrate from a 3D inversion of the observed AWAGS data that there are additional crustal conductors that cannot be explained from sediment thickness alone, but require additional conduction mechanisms in the crust over significant depths.Item Open Access A sedimentological approach to the geology of the Corunna area, S.A.(1972) Lemon, N. M.; School of Physical SciencesThe type area of the Corunna Group of sediments of Carpentarian age, outcropping in the northeast of Eyre Peninsula, South Australia, was mapped, divided into members and the sedimentary history determined. It was decided that suitable subdivisions were; the lower conglomerate member, the lower green sandstone member, the red conglomerate member, the white conglomerate member and the upper green sandstone member. A major unconformity was found between the red and white conglomerate members. The sediments were deposited in a trough which opened to the sea to the north. Tectonic activity dictated the type of sediment, whether marine or terrestrial, deposited. Most of the sediment supply was from the east for the red conglomerate member, and from the southwest for the white conglomerate member. The sediments were then faulted, folded and intruded by dykes during the Wartakan phase of tectonic and igneous activity.Item Open Access Age and basin evolution of the Cuddapah Supergroup, India.(2010) Macintosh, J. N.; School of Physical SciencesU-Pb zircon geochronology indicates deposition of the Cuddapah Supergroup, Cuddapah Basin, India occurred for at least 986 million years. Deposition started after 2502±17 Ma with the deposition of the Gulcheru Formation and ended after 913±11 Ma with the deposition of the Cumbum Formation. Maximum depositional ages have been found for individual formations within the Cuddapah Supergroup; the Pulivendla Formation has a maximum deposition of 1899±19 Ma and the Bairenkonda Formation has a maximum depositional age of 1660±22 Ma. Thermal events during the Palaeoproterozoic present a possible cause of basin formation. At this early stage of the Cuddapah Basin’s evolution the provenance of sediments was the Dharwar Craton, which currently underlies the basin and borders it on the north, south and west sides. The uplift of the Eastern Ghats on the eastern margin affected the evolution of the Cuddapah Basin, changing the shape and the sediments of the basin. Uplift and deformation events in the Eastern Ghats folded the eastern side of the Cuddapah Basin and are responsible for its present crescent shape. The formation of the Eastern Ghats caused increased subsidence to the east, creating an asymmetry in the depth of the basin. The provenance of the sediments of the Cuddapah Supergroup changed to the Eastern Ghats for the deposition of the youngest stratigraphic group, the Nallamalai Group.Item Open Access The age and origin of the western Ethiopian Shield(2013) Blades, Morgan; School of Earth and Environmental SciencesWestern Ethiopia is made up of a range of supra-crustal and plutonic rocks. The Precambrian exposures of the Western Ethiopian Shield are positioned within the juvenile Neoproterozoic crust of the Arabian Nubian Shield and the older, predominately gneissic Mozambique Belt (Woldemichael et al. 2010). The age and origin of the Western Ethiopian Shield are still largely unidentified. The aim of this paper is to constrain the age and origin of the sedimentary and igneous rocks within the Western Ethiopian Shield. This will be done using isotopic techniques. The detrital zircons have been analysed for U-Pb age (yielding maximum depositional ages and age provenance information) and Hf isotopes (to investigate the nature of zircons). Geochemical analysis on the Thermal Ionisation Mass Spectrometer (TIMS), Inductively Coupled Plasma Mass Spectromentry (ICP-MS) and microprobe has also been undertaken. One of the focuses is the examination of the volcanic and volcaniclastic successions, as well as, the geochemical nature of the ultra-mafic bodies in the Shield. The geochemistry of metavolcanic and meta-volcaniclastic data suggest that the origin of the volcanics formed in an arc-like setting. Relatively low niobium; however, suggest that the mantle source may have been more enriched than that seen in modern volcanic arcs. Detrital zircons, obtained from a meta-sandstone, yielded provenance age peaks at ~2499 Ma, ~1855 Ma and between 1100-800 Ma and a maximum depositional age of 838 ± 13 Ma. Hf Isotopes from the same zircons demonstrated that both the oldest and youngest populations have broadly juvenile Hf isotopic values however; ~1820 Ma age shows significantly evolved Hf isotopic values. A minimum age constraint on the deformation was provided by the U-Pb age of 572 .6 ± 7.6 Ma and yielded whole epsilon Nd values of 3.74 and epsilon Hf values of 6.79-7.98, demonstrating a juvenile origin. A significant aspect of the Arabian-Nubian Shield is the interpretation of the N-S oriented regional shear zones. Concentrically zoned mafic/ultramafic bodies, previously identified as remnants of the oceanic crust, are suggested to be Alaskan-type intrusions. Though chemically different to typical Alaskan-type intrusions these display a subduction affinity and have close associations to shear-zone hosted intrusions elsewhere in the Arabian Nubian Shield. Thus, they have been interpreted as being formed in similar supra subduction intrusive settings.Item Open Access The age and sediments source of the Amadeus Basin Cryogenian-Ediacaran stratigraphy(2018) Al-Ghafri, M.; School of Physical SciencesThe Amadeus Basin is a big intracratonic elongate basin that is mainly exposed in the Northern Territory. Sedimentation in the basin began in the Neoproterozoic and ended in the Late Devonian/Early Carboniferous. The Amadeus Basin stratigraphy, age and source of sediments are not well constrained. This study attempts to better constrain the age and sediment sources for the Johnnys Creek formation, Areyonga Formation, Pioneer Sandstone, Pertatataka Formation and Arumbera Sandstone. U-Pb detrital zircon analyses were conducted using the Laser Ablation Inductively Coupled Plasma Mass Spectrometry technique (LA-ICP-MS) along with Hf isotopic analysis. The U-Pb data constrained the depositional age of the Pertatataka Formation and Areyonga Formation with a maximum depositional age (derived from the youngest zircon grain) of 651 ±19 Ma and 683 ±20 Ma respectively. The main source of sediments for the Arumbera Sandstone, Pertatataka Formation and Areyonga Formation is the Musgrave Province, while it is the Arunta region for the Pioneer Sandstone. This interpretation is based on peaks of zircon ages plotted as a probability density function. The epsilon Hf data yielded positive and negative values across the ages of all formation. This is indicative of a mix of juvenile and recycled crust host magmas.Item Open Access Age, provenance and metamorphic conditions of the Mercara Shear Zone, Coorg Block, India(2016) Mansfield, W. H.; School of Physical SciencesHigh pressure granulite metamorphism has never been recorded during the Mesoarchaean. The Mercara shear zone in the Coorg Block, south west India plays host to kyanite-sillimanite-garnet-bearing felsic granulites that equilibrated at 11-13 kbar and 860 °C and 7.5-9 Kbar at 850-860 °C. LA-ICP-MS of U-Pb zircon and in-situ monazite geochronology reveal that the assemblages were first metamorphosed at ca. 3071 Ma, then again at ca. 676 ± _47 Ma. Pressure-temperature-time studies from the shear zone had not previously described conditions of this nature before, revealing how timing the suturing of the Coorg block will require extensive sampling methods. The conditions described however provide an insight into the thickened crust and low apparent thermal gradients existing during the stagnant-lid to first tectonism transitionary period, a period that usually only records high apparent thermal gradients and weakened crust. The ancient assemblage preserves regimes typical of contractional orogenic events, implying crustal thicknesses 35-40 km deep. Crustal thickening of this nature provides evidence for modern style tectonics operating during the Mesoarchaean.Item Open Access Age, tectonic geography and provenance of the Renner Group, Tomkinson Province, Northern Territory(2020) de Groot, A. M.; School of Physical SciencesThe informally termed greater McArthur Basin is a Paleoproterozoic to Mesoproterozoic multiphase basin system that records a billion years of Earth’s history within the Northern Territory. Sedimentary successions that make up the basin preserve evidence for events that surround the basin during its formation. In this study we present LA-ICP-MS detrital zircon U–Pb, Lu–Hf and REE data that provide new constraints on the Renner Group and reveal provenance variations that exemplify the evolution of the basin. Using the youngest, near-concordant, zircon grains, the maximum depositional age for each formation is determined. The maximum depositional age for the Gleeson Formation has been constrained to later than 1600 ± 42 Ma. Grains from the Sweetwater Member, Grayling Member and Powell Formation provide maximum depositional ages of 1624 ± 37 Ma, 1554 ± 77 Ma and 1714 ± 50 Ma, respectively. As well as using U-Pb in zircon, we also look at U-Pb in detrital rutile. These data yielded ages of 1731 ± 39 Ma (Sweetwater Member), 1811 ± 45 Ma (Grayling Member) and 1703 ± 32 Ma (Powell Formation determined by the youngest, near concordant grain). Age variations within the stratigraphy propose a subtle change from older, Paleoproterozoic sources to additional input from younger sources. Formations in the Renner Group record age peaks that are consistent with rocks of the Aileron Province, Mount Isa Inlier and the Gawler Craton. By comparing U-Pb and Lu-Hf data, the Renner Group correlates with the Roper Group (McArthur Basin), South Nicholson Group (South Nicholson Basin) and the Tijunna Group (Birrindudu Basin). In particular, the Powell Formation of the Renner Group is equivalent to the Bessie Creek Sandstone of the Roper Group, and shares similarities with the Wondoan Hill Formation of the Tijunna Group. On the other hand, the Grayling Member, Sweetwater Member and Gleeson Formation are equivalent to the older formations of the Lower Roper Group such as the Arnold Sandstone and Crawford Sandstone. I suggest that the variation in provenance records the exhumation and exposure of these regions as a result of intracratonic rifting and magmatism from 1.5 – 1.4 Ga. The increase in 1860–1650 Ma detritus suggests uplift of the Arunta region.Item Open Access Albitization and REE-U-enrichment in IOCG systems: insights from Moonta-Wallaroo, Yorke Peninsula, South Australia(2013) Kontonikas-Charos, A.; School of Physical SciencesIron Oxide Copper Gold (IOCG) deposits are the products of crustal-scale metasomatic alteration, generally considered to be associated with the emplacement of large felsic intrusions. These systems are typified by zoned, broad alteration haloes comprising the products of an early, barren albitization event, and late, ore-hosting potassic/calcic (skarn) alteration associated with mineralization. Yttrium and rare earth elements (REY), and also uranium, are prominent components of most IOCG systems. The REY-signatures of feldspars and accessory apatite, Fe-(Ti)-oxides and other minerals are geochemical tracers of alteration stages within a magmatic-hydrothermal system. This study sets out to identify links between magmatism and initiation of hydrothermal activity, and to test the hypothesis that albitization is a pre-requisite stage for REE-U enrichment in magmatically-derived IOCG systems. The compositions and trace element concentrations in key minerals have been analysed using scanning electron microscopy, electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry in a varied range of magmatic to metasedimentary lithologies from the Moonta-Wallaroo region, an area in which broad regional-scale alkali alteration is recognised. Results confirm a strong link between albitization and REE-U-enrichment. The process of albitization is seen to consume, redistribute and lock-in REY, LILE and HFSE via complex fluid-rock reactions dependent on the pre-existing mineral assemblages and fluid characteristics, providing a holistic model for IOCG-driven alkali metasomatism. The trace element signatures recorded by K-feldspar reflect a transition from magmatic to hydrothermal stages within an evolving IOCG system. Although further constraints on these signatures are required, they could prove invaluable in mineral exploration as they suggest a quantifiable distinction between alteration associated with mineralization, and regional background. This hypothesis requires testing elsewhere in the Olympic Province and in analogous terranes.Item Open Access The alteration history of Late Proterozoic Wooltana Volcanics, Mount Painter Province, S.A.(1992) Smith, P. B.; School of Physical SciencesThe Wooltana Volcanics experienced a pervasive low grade hydrothermal alteration prior to the Delamerian. The timing of this event is poorly constrained. However the available evidence is consistent with the metasomatism occurring during the active stretching thought to have caused the uplift related refrigeration responsible for the formation of the Merinjina Tillite. This study confirms the proposals of previous workers that the Wooltana Volcanics, Beda Volcanics and Gairdner Dyke Swarm are temporal equivalents, although this study has shown the Gairdner Dyke Swann to be a systematically fractionated end member. The Wooltana Volcanics are very like the Parana low-Ti CFB of Brazil and also the dolerites from the Atlas Mountains of Morocco. Both are associated with magmatic events immediately preceding the first openings of the Atlantic Ocean. The occurrence of the Port Pirie Volcanics within Burra Group sediments suggests a reoccurrence of mantle decompression due to lithospheric stretching further to the south.Item Open Access Amphibolite and metasediments of the northwest Weekeroo Inlier, Olary Province(1985) Taylor, G. J.; School of Physical SciencesThe northwest Weekeroo Inlier, Olary, consists of Lower Proterozoic, Willyama Supergroup metasediments and amphibolites. Upper Proterozoic cover metasediments of the Adelaide Supergroup overly these basement rocks. The basement rocks of the area are dominated by structures of the third Olarian event. Macrosocopic anticlines and synclines are open to tight, easterly plunging with a southerly dipping axial surface. The third generation penetrative schistosity cross-cuts a former schistosity (S1 or S2) which is parallel or oblique to layering. Abundant crenulations and kinkbands are likely to belong to the first Delamerian folding event which reactivated many basement structures of the Weekeroo Inlier. A stratigraphic sequence is recognized whereby pelites ('Mica Schists') overly psammo-pelites and quartz-albite rocks ('Bedded Schists'). A very broadly conformable sequence of massive, brecciated and layered amphibolite is "stratigraphically positioned" at the top of the Bedded Schists. From consideration of abundant sedimentary structures, together with facies changes and overall stratigraphic relations, likely depositional models include a very shallow marine shelf, a broad shallow inland lake-alluvial fan toe complex, and a river dominated, regressive deltaic-sabkha situation. Olarian metamorphic conditions ranged from those characteristic of the upper greenschist facies to those typical of the mid-amphibolite facies. These were followed by strongly retrogressive metamorphism (lower greenschist facies grade) associated with the cover deformation events during the Delamerian Orogeny. The Olarian metamorphism is manifested by paragenetic relations between actinolite, hornblende, epidote, albite, opaques and sphene in amphibolites and between fibrolite, chloritoid, almandine, biotite, muscovite, sericite, quartz, minor staurolite and minor chlorite in pelites. Closely associated with the amphibolite bodies of the Weekeroo Inlier are albitites and calc-albitites. Previously, a metasomatic origin was proposed for these albite rich rocks. An evaporitic sediment with a possible tuffaceous component is now considered more likely. The Weekeroo amphibolites are chemically similar to ferro-tholeiites of ocean floor/mid oceanic ridge transitional to continental origin.Item Open Access Analyses of late stage, Mesoproterozoic, syn and post tectonic, magmatic events in the Moonta Sub-domain: Implications for Cu-Au mineralisation in the "Copper Triangle" of South Australia(1994) Wurst, A. T.; School of Earth and Environmental Sciences, Geology & GeophysicsThe Moonta-Wallaroo area has been of economic, historical and scientific importance in South Australia's history for over 130 years. The nature of mineralisation in the area has long been a point of conjecture. This study looks at the nature of ore deposition and specifically its relationship to granitoids and pegmatites in the Moonta Subdomain. Using various analytical techniques the study has shown that granitoids in the region have distinctly different petrological, textural, structural, geochemical and isotopic characteristics. Two main granitoids were·recognised as the Tickera Granite and the Arthurton Granite. Geochemical studies suggest that magmatism in the Moonta Subdomain was a continuous process in the Mesoproterozoic. The older Tickera Granite, displays syn-collisional, more I-type characteristics and syn-collisional S-type characteristics (represented by a monzonite and a tonalite respectively). The younger Arthurton Granite shows A-type, anorogenic characteristics. A temporal shift from syn-collisional to anorogenic granites suggests a tectonic control on magma generation and emplacement during this period. Trace element characteristics of the Arthurton Granite are homogeneous over a wide spatial range, is suggesting that it may be part of an extensive batholith. Geochemistry of pegmatites implies that they were late stage fractionation products, related to these granite intrusions. A study of the Tickera Granite (Point Riley-Nth Beach) revealed a dominant structural fabric which suggested the granite was intruded into a tectonic regime in which shearing was prominent. Sediments intruded by the granite suggested deposition in a shallow intracratonic rift setting, followed by polyphase deformation during orogenic activity and subsequent shearing possibly related to the enigmatic Wartakan Event. Isotopic studies highlighted differences in the petrogenetic source regions of the Tickera Granite and the Arthurton Granite. The Tickera Granite (represented by monzonite) displayed more mantle like characteristics while the Arthurton Granite (represented by granite from Arthurton and adamellite from Moonta) displayed more crustal features, highlighting its A-type nature. Studies also showed that a pegmatite from the Wheal Hughes was most like the later of these two granites. Tourmaline studies of Wheal Hughes samples implicated derivation from a metapelite and calcsilicate precursor, a common feature of most tourmaline studied in the area. This may indicate remobilisation of boron rich fluids and metals from these sediments The close association of tourmaline with the ore in the Moonta Mines region implied a common source region. A tectonic setting and model for ore deposition is proposed on the basis of the study findings. The model proposed the remobilisation of metals which were initially deposited in a ensialic rift type environment (common to other Palaeoproterozoic metalliferous terrains) by the intrusion of the Tickera Granite, during regional shearing. And further concentration of metals by subsequent intrusions of the Arthurton Granite batholith.Item Open Access An analysis of the sedimentary hosts to mineralisation at the Cattlegrid Orebody, Mt. Gunson.(1981) Busbridge, M. J.; School of Physical SciencesThe Cattlegrid Orebody is located at the disconformable contact between the Willouran Pandurra Formation and the overlying Marinoan Whyalla Sandstone. Mineralisation is located on a palaeo high of Pandurra quartzite known as the Pernatty Culmination. The Pandurra Formation at the Cattlegrid Mine is a moderately to moderately well-sorted, cross-bedded quartz arenite. Grainsize analysis and cross-bedding data indicates it to be of fluviatile origin, while packing and compaction of the grains suggests a considerable thickness of quartzite has been removed by erosion. The bimodal Whyalla Sandstone is a texturallyinverted subfelsarenite, with well-rounded and spherical quartz grains in a poorly- to moderately-sorted fabric. Ripple marks, truncation of sandy and clay laminations, and a grain-size analysis suggests the Whyalla Sandstone to be a beach deposit. Syndepositional faulting, thickness of the beach deposit and the textural inversion suggest the sandstone to have been reworked by successlve transgressions and regressions. It is in the fractured and brecciated upper Pandurra Formation that the bulk of the mineralisation (chalcocite, bornite, chalcopyrite) is found in fractures and vughs. Basal Whyalla Sandstone is also richly mineralised. Throughout the Cattlegrid Mine, one, occasionally two, predominant lenticular clay bands show evidence of acting as a glide plane. Squeezing of the clay into fractures of the overlying quartzite, striations, and sharp transitions from the Upper Cattlegrid Breccia to the underlying mosaic breccia and displacement of sand wedges, all suggest sliding. The topmost Cattlegrid Breccia is thought to be a bajada breccia underlain by the mosaic breccia, considered to be due to a normal weathering cycle and mild tectonic activity. Gelifluction or periglacial mass movement processes are considered to be the mechanism responsible for the formation of tepee-like anticlines and sand wedges. Cryostatic pressures resulting from the melting of the active and talik layers and lateral movement over the permanently-frozen ground and/or clay band is considered to result in the water-escape anticlinal structures. Tensional fractures resulting from this movement initiated ice wedges. Fluid inclusion data suggest a calcium-rich, highly saline, dense brine precipitated copper-sulphide mineralisation. Waters of a surface origin e.g., connate, meteoric, are therefore ruled out due to the high Ca content and paucity of Na and K salts. YPMA has suggested that these dense brines created instability in the brecciated quartzite due to excessive pore pressures. This instability has caused slumping along a decollement surface and formation of the anticlinal structures and sand wedges. Similar structures are observed in Upper Mississippi Valley Pb-Zn districts. The mixing of this dense copper-bearing brine with less saline connate waters of the Whyalla Sandstone has caused precipitation of copper sulphides at the disconformable contact.Item Open Access Anisotropic forward modelling of fluid injection and phase angles exceeding 90o in magnetotellurics(2012) Macfarlane, J. E.; School of Earth and Environmental SciencesElectrical anisotropy, defined as the directional dependence of electrical conductivity within a medium, causes changes in the electromagnetic signal measured by magnetotellurics (MT) and as such is an important property to consider when interpreting MT data. This study concentrates on replicating the MT response measured at two distinctively different geological settings using a series of 2 dimensional anisotropic forward models. Results presented in this study show that 2-dimensional anisotropic forward modelling is able to account for subtle differences in subsurface anisotropic resistivity structures. Specifically, 2-dimensional anisotropic forward modelling is able to reproduce the measured difference in MT response between pre- and post fluid injection conditions at the Paralana Geothermal System using an anisotropic fluid volume. A second application in constraining the source of the anomalous phase angles exceeding 90o observed in MT measurements of the Capricorn Orogen, shows that 2-dimensional anisotropic MT models are not able to produce phase angles exceeding 90o in the MT data which has its electric field orientated perpendicular to the geoelectric strike. These findings provide a case supporting the use of 2-dimensional anisotropic forward modelling as a means of modelling changes caused by the flow of a fluid through the crust. In addition, they also highlight issues associated with its application to complicated structures perpendicular to the strike of the profile.Item Open Access Anthropogenic mineral systems: material flow, geochemistry, and mineralogy of the Prominent Hill tailings deposit(2023) Cooke, H. M.; School of Physical SciencesHumans shift the same magnitude of rock around the planet as does nature via geological processes. This, in no uncertain terms, is because we mine. Our exponential extraction of metals to grow modern society is most voluminously archived in mine waste deposits like waste rock dumps and tailings, to which we add 100 billion tonnes of material yearly. As dominant agents of the geosphere we must challenge ourselves on this enormous disposal of mineralogical natural capital. The Prominent Hill tailings storage facility (TSF) is an anthropogenic-geologic waste deposit created at the final stage of material flow of Prominent Hill’s mining processes. Tailings sediment provenance and geochronology, and the TSFs stratigraphy, critical mineral resource potential (e.g., copper (Cu) and rare earth elements (REEs)), can be quantified by engaging with material flow processes. This undertaking ultimately maps an anthropogenic mineral systems approach to characterising TSF resources. Microanalytical characterisation of Cu and REEs in sampled Prominent Hill tailings reveals mineralogical fingerprints that become the geometallurgical basis for mineral reprocessing pathways. The TSF contains 112 million tonnes of tailings which average 0.14% Cu and 0.3% REE. Cu(-Fe) particles are highly enriched in Mo, Ag and Au, and are extensively oxidised to Cu-sulphate, and Fe(-Cu, -S, -Cl) mineral assemblages. Meanwhile, the TSFs REE inventory is dispersed between several types of fluorcarbonates and phosphates with unique light REE (LREE) and heavy REE (HREE) signatures. Monazite contains the highest LREE contents, though magnet REEs (e.g. Pr, Nd, Dy) are concentrated in fluorcarbonates. Apatite is potentially a significant reserve of HREEs. By blueprinting the unique anthropogenic mineral systems of our TSFs, this thesis helps future explorations of tailings deposits as responsible sources of critical raw materials and frames an opportunity to redesign our billion-tonne footprints in the Anthropocene rock record.Item Open Access Apatite thermochronology of the Bole-Nangodi Shear Zone (northern Ghana): insights into the thermal history of equatorial Atlantic rifting(2016) Fernie, N. S.; School of Physical SciencesThe Bole-Nangodi (BN) shear zone is located in northern Ghana and is thought to represent the continental extension of an equatorial Atlantic transform fault. This study applies low temperature thermochronology to constrain the thermal history of the BN shear zone with relation to Gondwana break-up during the Mesozoic. Apatite fission track (AFT) data obtained from the Ghanese Paleo-proterozoic basement along the primary NE-SW structural trend of the BN shear zone suggests a complex two phase cooling history. (1) Heating of the crust in the late Triassic – early Jurassic, related with the emplacement of the Central Atlantic Magmatic Province (CAMP); (2) Cooling associated with rift shoulder exhumation during early Cretaceous rifting of Africa from Brazil. Cooling ages obtained across the structural architecture furthermore constrain differential exposure of the thermal history, preserving older (CAMP) signatures to the south and younger (rifting) signatures to the north of the BN shear zone respectively. This indicates that the BN shear zone has been reactivated during the Cretaceous as a result of the build-up of strain being generated by the Central and South Atlantic rift margins. The results obtained in this work indicate the extent to which CAMP-related heat flow that has affected the upper crust within the West African Craton can at least be constrained to northern Ghana. Furthermore, Cretaceous intra-continental strike-slip faulting of the West African continental crust was likely induced along Paleo-proterozoic shear zones acting as zones of weakened crust where deformation and rifting were localised and may have ultimately controlled the orientation of fracture zones within the Equatorial Atlantic.Item Open Access The application of ground based and airborne radiometric methods to aid geological mapping in the Olary Province, South Australia(1999) Shearer, A.; School of Physical SciencesThe Late Palaeoproterozoic Olary Domain, in the east of South Australia, has been extensively surveyed using airborne geophysical methods, including 256 channel radiometries. This detailed data set over outcropping areas is potentially a valuable aid to geological mapping. Ground-based radiometric data was obtained along profiles through the eastern Weekeroo Inlier and Ninnerie Hill areas in order to relate radioelement concentrations to lithological units. The Weekeroo Inlier traverse sampled all stratigraphic units present in the Olary Domain. The Ninnerie Hill traverse sampled Early Mesoproterozoic granitoids, migmatites and host metasediments. Two acquisition styles were attempted when collecting the ground-based data, with continuous recording to provide results that better replicate the airborne data than discrete sampling. The discrete sampling method was found to be heavily influenced by single point anomalies and not representative of the lithological average. Relative peaks and troughs on all three channels and total count data correspond well between the ground and airborne data. Correlation between the airborne data and the ground-based data was best for the K channel. For the Th channel the ground-based data was similar to the airborne data in wavelength and amplitude but was bulk shifted below the airborne data. The U channel data from the ground-based data detected the same anomalies as the airborne data but was an order of magnitude higher. The differences between the airborne and ground-based data could be due to errors in the calibration process that was performed for part of this project or due to the time difference in acquisition of the ground based and airborne data. Comparison of ground-based data with the geology of the survey areas revealed that radiometric data can provide useful lithological discrimination. Within the survey area some differences between metasediments, intrusive lithologies, and alteration types are determinable. The radiometric data can successfully differentiate between potasic and sodic granites. The low levels in all three measured radioelement channels can reflect occurrences of amphibolites. The data discriminates between pelites and psammites in that the pelites contain significantly higher levels of K, the difference between levels of Th and U are less extreme but are still discernable. As well as providing a mapping tool on the lithology scale, the interpretation of radiometric data can resolve sub-lithology scale variations.