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 Deciphering the origin of high carbon shales: the Amungee organofacies conundrum, Velkerri Formation, Greater McArthur Basin(2023) Edwards, L. E.; School of Physical SciencesThe Mesoproterozoic (1.4 Ga) Velkerri Formation of the McArthur Basin contains a number of intervals rich in organic matter (with TOC values locally >10wt%). These have been used as supporting evidence for a transient middle Mesoproterozoic global oxygenation event. New geochemical data collected from Urapunga-4 were compiled with previously published data to; a) illuminate the origin of these organofacies and to particularly understand why the shale preserved such large fluctuations in TOC over short stratigraphic distances, and to b) address the competing hypotheses. The relationship between TOC and δ13C(org) shows that the TOC peaks in all three high organic shales (A, B, and C shales) in the Amungee Member are interpreted to be caused by primary production. However, the A shale was also interpreted to possibly be due to sediment input outpacing the increased carbon production. The B shale was interpreted to be a result of a small organic bloom that was immediately followed by an increased sediment supply that was likely from a storm event. In addition, organic geochemical data and detrital U-Pb zircon and novel laser Rb-Sr dating from newly accessible core samples in the Beetaloo Sub-basin, combined with detailed sedimentology, were used, along with previously published data from Urapunga-4, to verify whether this new core (ELT002) intersects the Velkerri Formation. The depositional age of the new core and the difference in sedimentology and geochemistry between Urapunga-4 well indicate that this new core likely intersects the Kyalla Formation rather than the Velkerri Formation.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 Mineral textures in the Auckland Volcanic Field: Insights into ascent processes.(2023) Coker, J. L.; School of Physical SciencesThe Auckland Volcanic Field, a prominent monogenetic basaltic field, is characterized by rapid magma ascent from source to surface, yielding a landscape of diverse volcanic morphologies. Despite being extensively studied, the fundamental processes governing this field remain largely enigmatic. This study aims to shed light on these mysteries by scrutinizing mineralogical textures and chemistry at a scale representative of the entire volcanic field. To achieve this, we employed advanced techniques, including Scanning Electron Microscope (SEM) image analysis, Electron Microprobe chemical analysis, equilibrium testing, and thermobarometry. Through these methods, we scrutinized various minerals and identified compelling evidence suggesting fluctuations in magma ascent rates. Notably, we observed variable normal zoning rates in olivine, oscillatory zoning in clinopyroxenes, and the presence of lamellae exsolution, surrounded by unexsolved crystallization of Fe-Ti oxides. These mineralogical features offer crucial insights into the dynamic processes taking place during the ascent of magma beneath the Auckland Volcanic Field. The implications of these findings extend beyond geological curiosity. Understanding the changes in magma ascent rates carries significant implications for the forecasting and early detection of moving magma beneath Auckland. If magmas can be identified during slower ascent stages, this knowledge could serve as an essential precursor to the potentially hazardous rapid ascent phase. This insight is not only valuable for understanding the volcanic field's monogenetic nature but also for enhancing the safety and preparedness of the Auckland region in the face of volcanic activity. In conclusion, our research unveils critical mineralogical evidence of variable ascent rates within the Auckland Volcanic Field, enriching our understanding of this complex geological system. Furthermore, the potential implications for volcanic hazard mitigation underscore the practical significance of this study, as it has the potential to improve volcanic forecasting systems and protect the well-being of the Auckland community.Item Open Access Inferring regolith history via in situ Rb-Sr dating, mineral mapping, and elemental analysis at the Avon River Critical Zone Observatory, Western Australia(2022) Schultz, M.; School of Physical SciencesThe critical zone is the interface between atmo-, bio-, hydro-, and lithospheres which supports all terrestrial life. Within this complex system, regolith forms as weathered bedrock products coalesce on the surface, providing anchorage and accessibility to essential nutrients and water for plants and associated microbiota. Productivity within the regolith therefore has significant implications for all heterotrophic lifeforms. Global establishment of Critical Zone Observatories concentrate efforts on understanding this system and the long-term response to anthropogenic influences. This study contributes to this cause, defining baseline geochemical and mineralogical compositions at bulk- and micro-scales for regolith within the Avon River Critical Zone Observatory. This study also addresses novel in situ Rb-Sr dating as a method to separate abiotic and biotic pedogenic mechanisms. Sodium peroxide fusion and ICP-OES is compared against acid digestion and ICP-MS methods to determine a viable immobile index element. Subsequent ‘normalised’ elemental concentration profiles are produced which account for volume changes and relative loss or gain of elements through vertical section. Elemental profiles reflect gradual, or near complete depletions of all elements, excluding Al, Si and Fe-Al metal-oxide species, that relate to a matured rudimentary mineral assemblage of kaolinite, quartz, and Fe-Al-oxide species. Subsequent Rb-Sr dating of clays (i.e., chlorite, illite), micas and feldspars indicate that biotite within the monzogranitic bedrock is of Neoarchean age (2673.4 ± 56.1 Ma (n = 21)) whilst bordering chlorite and feldspars reflect a younger ‘apparent’ age of 2400.5 ± 60.2 Ma (n = 60). Interestingly, Rb-Sr dating of illite also reflect this younger ‘apparent’ age within error across all lower regolith horizons, suggesting inheritance of (87Sr/86Sr)o ratios during authigenic weathering of feldspar and clay precursors. This concludes that pedogenesis in the lower regolith horizons was of abiogenic origin but absence of illite in the upper horizons does not entirely discount biotic involvement.Item Open Access Unconformity-style rare earth element mineralisation along the Watts Rise-Castella Trend, Tanami Region, Western Australia.(2022) Rowland, J. R.; School of Physical SciencesUnprecedented demand for rare earth elements (REEs), driven by the development of new ‘green energy’ technologies, is driving significant exploration activity globally. Traditionally, REE production has been controlled by unique igneous rocks (e.g., peralkaline volcanics and plutonics) considered relatively minor in the geological record; however, to address demand, new mineralisation styles are being explored. Newly recognised unconformity-style hydrothermal REE (+ Au) mineralisation along the Watts Rise-Castella Trend by PVW Resources Ltd in the Tanami Region of north-western Australia comprises HREE-dominant mineralisation along a regional unconformity, hosted within hematised conglomeratic units of the Paleoproterozoic Pargee Sandstone. Detailed ore mineralogy, petrography, and mineral chemistry (via LA-ICP-MS) of samples from two currently-identified prospects within the exploration area provide insights into REE distribution. Geochronological ages via LA-ICP-MS U-Pb dating for both xenotime and zircon in the Pargee Sandstone constrain both the timing of ore mineralisation and the maximum depositional age of the host rock. Two main REE-bearing minerals are identified: xenotime [(Y,HREE)PO4] and florencite (LREEAl3(PO4)2(OH)6). Xenotime is the major host of HREEs, and occurs in different textural phases. In-situ U-Pb dating of xenotime yielded an age range of mineralisation between ca. 1.65 to 1.60 Ga; this timeframe is absent in local magmatic or orogenic events and is comparable to the timing of other REE occurrences in the region, suggesting a regional scale hydrothermal event in northern Australia. Detrital zircon U-Pb geochronology for the Pargee Sandstone produced a wide range of ages primarily between ca. 2.6 to 1.8 Ga, and a maximum depositional age between 1811 ± 5 Ma and 1832 ± 8 Ma. There is significant potential for discovery of further orebodies of this style, especially in the vicinity of regional unconformities, and given the current surge in exploration for REEs, this investigation will assist in the development of exploration models for equivalent terranes.Item Open Access The geochronology, palaeoenvironments and palaeontology of Robertson Cave inner chamber, Naracoorte.(2022) Robertson, B.; School of Physical SciencesRobertson Cave inner chamber within the Naracoorte Cave Complex (NCC) preserves a 4m sedimentary infill record that is relatively unexplored in terms of geochronology and paleoenvironmental history. The inner chamber of this cave also preserves undated megafauna remains and fossil evidence for long-term overwintering activities of the Southern Bent-Wing bat, a critically endangered species with only two known maternity caves in Australia. This thesis aims to provide a detailed geochronology (single-grain OSL dating) and geochemistry (XRF, XRD) study of the inner chamber to better contextualise the palaeontological, palaeoenvironmental and palaeoconservation significance of the Robertson Cave sedimentary sequence. The suitability of OSL dating in this deep cave setting is demonstrated by examining a modern surface sample and two samples from complex sediment horizons affected by syn-depositional mixing (i.e. entrainment and re-transportation of pre-existing sediments within the closed cave environment). These suitability tests confirm that the OSL signal is fully reset prior to entering the cave, providing a modern age of 0ka, and that it is advisable to employ statistical models (minimum age models) that target the most recently reset grain populations when dating deep cave sediments affected by syn-depositional mixing. Twelve single-grain OSL samples from the Inner Chamber excavation provide stratigraphically consistent ages spanning 74.6-10ka, demonstrating that the infill sequence covers a much longer time period than indicated by radiocarbon dating. The entire sequence was deposited between MIS (marine isotope stage) 4 or late MIS5 to early MIS1, with high sedimentation rates evident in late MIS3 (40.5-32.3ka), the MIS2 glacial (26.5-11.8ka) and early MIS1 (11.5-9.8ka), and disconformities coinciding with major climatic transitions at the MIS4/3, MIS3/2 and MIS2-1 boundaries. Two OSL ages from the lowermost unit constrain the timing of in situ megafauna fossils to 74.6-60.1ka, meaning Robertson Cave inner chamber is one of only three well-dated NCC caves preserving late MIS5 to MIS4 megafauna remains. XRF and XRD analyses indicate the presence of multiple guano-rich layers with elevated sulphate, phosphate, organics, and trace metal concentrations. These results imply complex diagenetic processes and reinforce the fossil bat record by confirming an intermittent geochemical signature of bat overwintering activities at Robertson Cave extending back to the last interglacial complex. The findings of this study have broader implications for understanding how sediment accumulation dynamics of NCC roof window cavities can be closely tied to changing climate conditions associated with glacial-interglacial cycles. The results also reinforce the palaeontological and palaeoconservation significance of Robertson Cave, particularly the long-term resilience of its critically endangered Southern Bent-Wing bat populations and their ability to adapt to widely varying climate regimes prior to European colonisation.Item Open Access Kangaroo Island climate variation over the past 7000 years reconstructed using lake sediment(2022) Kamleh, C.; School of Physical SciencesIn the face of devasting bushfires, droughts and floods in recent years in Australia, geologically recent Australian climate reconstructions provide useful context in understanding the long-term patterns of such events before instrumental records existed. There is a lack of such climate reconstructions in southern Australia. Kangaroo Island’s (KI) recent devastation by bushfires, as well as the presence of semi-permanent lakes on the island, make it a location suited for climate reconstructions using lake sediment to complement the understanding of bushfire occurrence. Existing research has focussed on Lashmars Lagoon in the east of KI, and this thesis adds to Lashmars Lagoon research, while also adding research from Little Grassdale Lagoon in the west of KI. Multiple techniques are used: 210Pb dating, radiocarbon dating, age-depth modelling, X-ray fluorescence (XRF), and mass-spectrometry. It is found that over the past 7000 years, Kangaroo Island entered a drier period after ~3000 years BP. This dry period coincides with the onset of more intense bushfires on Kangaroo Island, as recognised by existing research, suggesting a climatic control on bushfire patterns. The last 2000 years on Kangaroo Island are characterised by more variable climatic conditions, and there are fluctuations between wet and dry climates, within the larger context of a dry period.Item Open Access What is Nundorite? A petrological and geochemical study of an unusual rock of the Mount Arrowsmith Volcanics(2022) Johns-Mead, L. Y.; School of Physical SciencesNundorite is an enigmatic rock, known only from its type locality within the Mount Arrowsmith Volcanics (MAV), Western NSW. Alkaline igneous systems such as the MAV are an important source of critical mineral resources. Nundorite is compositionally unique, being peralkaline and enriched in rare metals (Zr, Nb and REEs), but with low silica and high alumina. Despite these features, there has been limited research on nundorite. This thesis represents the most extensive study of nundorite to date. A combination of field observations, petrography, bulk-rock and mineral geochemistry are used to describe samples and develop an understanding of nundorite’s genesis and evolution. Although nundorite only occurs as a single low outcrop, there is a progression of alteration and deformation over a span of ~250 m across the outcrop. Bulk geochemical composition does not change across this traverse, so this variation is attributed to localised shearing and associated metamorphism. Nundorite’s mineral assemblage is established as aegirine porphyroblasts in a predominantly sodic zeolite-orthoclase matrix with minor albite and nepheline. The primary zeolite changes from natrolite to analcime with proximity to a shear zone. Nundorite hosts a suite of unusual accessory minerals, including zircon, monazite, schizolite, cerite group minerals, fergusonite, fersmite, galgenbergite, epidote-allanite, as well as unidentified Zr and REE minerals. Similar complex arrays of accessory minerals have been described from other peralkaline volcanic systems that host critical minerals. Modelling nundorite to felsic alkaline igneous rocks shows that its unique geochemical composition could be achieved through metasomatism of a highly fractionated member of the MAV. Fractionation caused initial enrichment in alkalis and REEs, this was then concentrated by the removal of silica by an alkaline fluid. There are several avenues for further research on nundorite, including comprehensive mineral identification, further constraining alteration conditions, and evaluating the economic potential of the rock.Item Open Access Architecture and thermochronology of the base Adelaidean unconformity at Arkaroola.(2022) Imbrogno, D. N.; School of Physical SciencesThe Arkaroola unconformity represents a gap of almost 750 Ma, yet as well as being demonstrably erosive, the basement Mount Neill Granite is strongly foliated in a style similar to that reported from extensional core complexes. The architecture and strain along this lithological boundary varies in geometry and intensity, with past research providing limited constraints on the structural relationship between the basement and overlying basin rocks. This thesis maps this strain seen in the basement, investigates the relative timing of the shear strain with respect to macroscopic fold development, examines microstructural record, and dates cooling after strain. Samples were collected over a sequence of the unconformity with an increase of shear strain in the basement approaching this boundary, and into the overlying Paralana Quartzite. Normal shearing kinematic indicators at multiple boundary locations suggest basement foliation pre-dates large scale folding during the Delamerian Orogeny. Orientation of c-axes in quartz grains in the protomylonitic basement proximal to the boundary show evidence for non-coaxial strain, with the quartzite directly above producing a girdle representing pure shear, plane strain deformation. This thesis examines previous thoughts on coeval intrusion and deformation of the Mount Neill Granite, with new evidence for basement foliation developing shortly before deposition and rifting sequences of the Adelaidean Superbasin. Presence of prism [c] slip and dynamic recrystallisation in quartz grains indicates temperatures reached at least 500 °C. In-situ Rb–Sr muscovite ages from this study correlate to cooling after the Delamerian Orogeny, the intrusion of the British Empire Granite, hydrothermal deformation, and localised pegmatite intrusions. This study presents a tectonostratigraphic timeline for the evolution of the boundary, with evidence for a mid-crustal extensional shear zone in early formation of the Adelaide Rift Complex. Future work on additional boundary locations is needed to better understand regional architecture resulting from early basin formation.Item Open Access Chromium and radiogenic strontium isotopes in the Earth’s upper mantle and oceanic crust: Insights from the Semail Ophiolite, Oman(2022) Faulkner, C. E.; School of Physical SciencesThe Semail Ophiolite in Oman records a transect through the oceanic lithosphere, including the crust and upper mantle, which obducted onto the Arabian Peninsula during the Late Cretaceous. This thesis explores the formation and alteration history of the Semail Ophiolite using coupled chromium (Cr) and strontium (Sr) isotope geochemistry. As standard seafloor drilling cannot reach typical upper-mantle depths, the results provide unique insights into the geochemical processes that form oceanic lithosphere. The measured redox-sensitive Cr isotopes (expressed as δ53Cr‰, relative to NIST 979) help determine (i) the Cr isotope fractionation effects related to oceanic lithosphere formation; and (ii) the secondary fluid alteration effects. The Cr isotope data supports heterogenous δ53Cr composition of the upper-mantle and oceanic crust, indicating that partial melting of the upper-mantle and fractional crystallisation may impart detectable Cr isotope fractionation effects (up to ~0.5 per mil, ‰). However, samples collected through a profile of the ophiolite show various degrees of alteration related to a complex tectonic history. Mineralogy (XRD and SEM-EDS) shows evidence for serpentinisation of upper-mantle and lower crustal rocks, which may cause Cr isotope fractionation. Radiogenic Sr isotope ratios (87Sr/86Sr) paired with loss on ignition (LOI) data reflect the source and extent of fluid alteration processes, including serpentinisation. Fluids have raised the LOI and 87Sr/86Sr values of most ophiolite samples. Some rocks have higher 87Sr/86Sr signatures than Cenomanian seawater from when the ophiolite was forming, indicating post-obduction alteration by non-marine fluids (crustal/meteoric waters). The findings suggest that δ53Cr varies throughout the upper-mantle and oceanic crust. Thus, Cr isotopes can be modified by high-temperature processes such as partial melting and fractional crystallisation, as well as via low-temperature alteration involving serpentinisation. Further studies on Cr isotopes at other locations and ophiolite sections are needed to corroborate these findings and to better constrain δ53Cr variability in the Earth’s upper-mantle and oceanic crust.Item Open Access Copper movement in active volcanic systems(2022) Dalton, C. L.; School of Physical SciencesMovement of copper within volcanic systems is poorly understood. Arenal provides an unique insight into metal movement in young magmas. Due to its young age (<100 years) (210Pb/226Ra)0 is a useful indicator of fluid degassing or accumulation within a system. This work compares Cu isotopic analyses over Arenal’s last 30 years of continual eruptions against prior analyses (210Pb/226Ra)0. Copper was found to be enriched (83.10 ppm – 130.20ppm) within this eruption period. δ65Cu had a range of 0.650 to -0.90726 with the initial positive δ65Cu being linked with a (210Pb/226Ra)0 above 1 and initially high Ba/Th ratios. As δ65Cu decreased, (210Pb/226Ra)0 effectively stayed around 1, an indicator that these lighter copper isotopes were not fluid controlled. Multiple elements (Co, Cr, Th and Si) were compared to copper isotope evolution which showed decoupling of copper from systems that would otherwise fractionate it (fractional crystallisation, assimilation). Thus, magmatic volatiles may fractionate copper within this system. This being true means that copper is being moved by magmatic volatiles within these active volcanics. These fresh fluids are preferentially taking the heavier δ65Cu and erupting it. This follows a Rayleigh fractionation curve but assumes that the parental magma much be enriched in Cu (250ppm). A potential model showing Arenal’s eruptions was constructed showing this. Cu isotope analysis furthers our understanding of economic metal movement and can be applied to ore-forming environments.Item Open Access Paragenesis of the Dazzler Heavy Rare Earth (HREE) and Uranium Deposit, Browns Range, Western Australia(2022) Cillins, B. N.; School of Physical SciencesUnconformity-related rare earth (REE) mineralisation occurs at Browns Range, Western Australia, where hydrothermal basinal brines mobilise REE from the Archean Browns Range Metamorphics (BRM) to interact with phosphorus-bearing meteoric fluids permeating from the unconformably overlying Paleoproterozoic Birrindudu Group. Significant contributions to the understanding of these systems have been made with a principal focus on the Wolverine heavy rare earth (HREE) deposit, which is situated completely within the BRM, with no real known proximity to the overlying sandstones that play a major role in ore formation. The Dazzler HREE deposit, discovered in 2018, is situated on the unconformity across three lithologies, the BRM, an argillaceous metasediment at the base of the Birrindudu Group’s Gardiner Sandstone, and within fractures immediately overlying. Investigation into the paragenesis of the Dazzler deposit opens the opportunity to revisit the unconformity-related REE model. This study investigates the major element geochemical composition of the host lithologies using major element geochemical and hyperspectral drill core analysis to determine alteration assemblages, petrographical analysis with SEM-EDS, and U-Pb dating of xenotime with LA-ICPMS. Major element geochemistry constrains host BRM to an arkose (sublitharenite) and the argillaceous metasediment to a wacke (shale). HREE mineralisation predominantly occurs as clay-replacement of the argillaceous metasediment host with perching into the fractures of the overlying GSS and a mineral assemblage of xenotime ± florencite ± rutile ± torbernite. Minor breccia hosted REE mineralisation within the BRM is enriched in light rare earths (LREE) with a florencite ± xenotime ± rutile assemblage. Florencite abundance in the underlying breccias provide further insight into LREE – HREE fractionation. Torbernite is localised in fractures within the clay-replacement xenotime, appears texturally later than REE and may be precipitating using local Fe as a reductant. K-feldspar – muscovite alteration is evident within the BRM, consistent with that of Wolverine. Additional intermediate argillic – phyllic alteration of the already mica-rich argillaceous metasediment occurs syn-REE deposition. Age ranges of xenotime of 1679 – 1633 Ma are presented and were generally discordant, with a concordant age of 1641 ± 10.4 Ma (MSWD = 12). These coincide with the main- breccia hosted REE mineralising event seen at Wolverine. Exploration targets were provided, with a focus to the south of Dazzler and Rogue prospects recommended.Item Open Access Carrapateena’s silver lining: geochronology and the distribution of Ag in sulphide minerals(2022) Clegg. E. J. G.; School of Physical SciencesThe Carrapateena Iron Oxide Copper Gold (IOCG) deposit is located within the Olympic Copper-Gold (Cu-Au) Province on the eastern margin of the Gawler Craton, South Australia. IOCG deposits are well known for their Cu-Au endowment but also commonly contain economic by-product elements which can include silver (Ag). At Carrapateena, all economic Cu, Au and Ag mineralisation is hosted in the near-vertical Carrapateena Breccia Complex (CBC) where economic Cu is present primarily as chalcopyrite (CuFeS2) and bornite (Cu5FeS4). These minerals are also known to contain accessory Au and Ag but the relationship of these trace metals to the Cu-sulphides has not been constrained. Understanding the timing and distribution of Ag enrichment provides insight into deposit formation, metal mobility and may improve Ag recovery. Samples were chosen from petrography and μXRF analysis of core from drill holes DD12CAR108 and DD12CAR114. Scanning Electron Microscopy (SEM) and Laser Ablated Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were used to observe and analyse geochronological minerals, Cu-sulphides and trace elements associated with the major sulphides. Pyrite (FeS2) formed during relatively early hydrothermal events in the CBC with Cu-rich fluids subsequently entering the system resulting in chalcopyrite replacing pyrite. Paragenetic relationships indicate that bornite subsequently replaced chalcopyrite, which was followed by selective replacement of bornite by covellite (CuS). This study identifies covellite to be a significant host of Ag in the system, both at the current mining depth and in the deepest parts of the CBC sampled to date. Ag enrichment within covellite in the deepest drilled parts of the CBC may be the result of relatively low-temperature metal mobility, and provides evidence for a protracted evolution in the CBC with metal mobility potentially continuing until relatively recent times.Item Open Access Tracing of uranium isotopes and man-made radionuclides in contaminated soils at the nuclear testing site at Maralinga, SA.(2022) Charlwood, J.; School of Physical SciencesVarious nuclear fission and explosion trials were held at Maralinga, South Australia, by the United Kingdom from 1956 to 1963. Seven large trials each using atomic bombs of varying designs were detonated over this period. In addition to the seven large-scale trials, numerous minor trials were also performed within this period, and these are reported to have caused the greatest environmental impact to the area via dispersal of plutonium and uranium and related radionuclides. Fissile material used in the atomic weapons tested at Maralinga generally comprised 235U. Residual contamination is still present today in local soils. Although at greatly reduced levels it still poses a potential risk to humans through ingestion of airborne ‘hot’ particles which have a bulk composition of plutonium and uranium oxide. Enrichment of 235U in soils may therefore infer distribution of residual radionuclide contamination associated with historical atomic weapons testing. This research seeks to use the 235U/238U isotopic ratio obtained from Maralinga soil as well as control samples from various natural sources to generate a method that can constrain the limits of man-made nuclear contamination across Maralinga sites. Gamma spectroscopy was used to identify both natural and man-made radionuclides in samples. Analysis of bulk soils collected from across Maralinga test sites did not find a 235U enrichment within a 0.14% error margin (relative to the abundance of 238U) obtained through analytical uncertainty of uranium isotope measurements. The 235U/238U ratios of Maralinga soils and uncontaminated soils all presented a quasi-natural isotope ratio near the proposed value of natural uranium standard CRM 145 of 0.00725. However, gamma spectroscopy data shows that the Maralinga soils still contain an excess of various man-made radionuclides indicative of nuclear fission waste products such as 241Am, 137Cs and 152Eu. Neither induction-coupled plasma mass spectrometry or gamma spectroscopy analytical approaches used in this study were suitable for the detection of 239Pu. Overall, we conclude that 235U present from nuclear testing may be present at concentrations but do not significantly influence or vary from the ‘natural’ or background 235U/238U isotope composition. The uranium isotope ratio does not appear to be a beneficial marker of residual radionuclide distribution in the Maralinga area based on the limited number of samples assessed. Gamma spectroscopy assessment of collected soils infers radionuclide distribution is not homogeneous across the Maralinga area, Further assessment using a grid sampling approach would provide better resolution of radionuclide distribution across the Maralinga area.Item Open Access Paragenesis of hydrothermal palladium in the Vulcan Iron Oxide Copper Gold Prospect.(2022) Browne, J.; School of Physical SciencesThe transportation and concentration of Pd and other platinum group elements (PGE) in crustal environments is unequivocally attributed to mafic-ultramafic magmatic processes. The identification of elevated Pd within some porphyry mineral systems combined with Pd thermodynamic modelling has, however, demonstrated Pd can also be efficiently concentrated and transported in hydrothermal fluids. The identification of Pd-elevated intervals up to ~5500ppb across the Vulcan iron-oxide copper gold (IOCG) prospect in the eastern Gawler Craton, South Australia, presents an unprecedented opportunity to investigate the mineralogy and transport of hydrothermal Pd. This study uses geochemical, petrographic, and in-situ micro-chemical methods to identify, quantify, and paragenetically assess the distribution of Pd-bearing minerals within Pd-rich hematite breccia at Vulcan. Furthermore, this study attempts to characterise the physiochemical nature of Pd-mobilising fluids in IOCG systems for the first time. Pd-enrichment occurs within apatite-rich hematite breccias containing varying amounts of siderite, dolomite, quartz, chlorite, pyrite, and chalcopyrite. Mineralogical hosts for Pd at Vulcan include some Ni-rich pyrite and a variety of Te-Se-Sb-As alloys identified as merenskyite (PdTe2), mertieite (Pd16Sb5As), and kalungaite (PdAsSe). Compositional mapping and trace element quantification of 22 pyrite grains demonstrate a peak Pd enrichment of 125 ppm occurring within Ni-rich (up to ~1 wt%) pyrite. Textural and trace element analysis of pyrite demonstrates compositional zoning in Pd, Ni, and Se within some Pd-rich (> 1 ppm) cores, suggesting primary pyrite as the initial host for Pd at Vulcan. Comparison of Pd-Pt whole rock composition and Pd paragenesis suggests an early introduction of Pd into the Vulcan system by a highly oxidised acidic fluid. Strong compositional distinction in pyrite Ni-Co concentration and apatite Cl content suggests subsequent hydrothermal activity by hotter and more saline fluid. This geochemical, petrographic, and in-situ micro chemical study presents the first investigation into the Pd-bearing mineralogy and hydrothermal fluid mobility of Pd within global IOCG mineral systems. Furthermore, this study demonstrates Pd can be significantly concentrated in IOCG systems, suggesting an unrecognised potential exists for hydrothermal Pd in the eastern Gawler Craton.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 Zircon and rutile provenance of the heavy mineral sands at the Copi North Deposit, Murray Basin, NSW(2022) Chalmers, S. C.; School of Physical SciencesThe Murray Basin hosts one of the world’s largest strandplain systems with large resources of heavy mineral sands (HMS). Associated with the Loxton-Parilla Sands formation, Murray Basin HMS are a key contributor to Australia’s titanium and zirconium production. Critical to discovery of new HMS deposits is determining the provenance of the HMS. Within the northern Murray Basin, a large resource of >1.2 billion tonnes of HMS at the Copi North deposit are delineated. However, provenance studies of the Copi North HMS (both shallower and deeper deposits) are currently lacking. In this study, the provenance of Copi North’s lower HMS deposit wasdetermined using zircon and rutile U-Pb geochronology and geochemistry. Of all zircon U-Pb ages (concordance ≤5%), over 84% fall into the age range of 0 – 1250 Ma with remaining zircon ages recorded as high as ca. 2630 Ma. Approximately 47% of zircons are derived from the Tasmanides to the northeast (0 – 480 Ma). Roughly 48% are considered to be derived from the Adelaide Superbasin (>500 Ma) and roughly 5% from the Delamerian Orogen (514 – 490 Ma), both of which provide an easterly transported source of HMS. Over 98% of rutile U-Pb ages (concordance ≤5%) are between 475 –550 Ma correlating to the provenances of the Adelaide Superbasin and Koonenberry Belt. Mineral Liberation Analysis (MLA) shows subtle differences between the two deposits highlighting minerals seen in the deeper deposit that are absent in the shallower deposit (e.g., sanidine, celestine and cordierite) as well as those that are absent in the lower deposit but observed in the shallower deposit (e.g., kyanite and scheelite). These results show a subtle difference in mineral makeup and provenance between the two HMS deposits at Copi North. Further investigation into the geochronology of rutile grains from the Adelaide Superbasin and Koonenberry Belt would corroborate these findings.Item Open Access The petrology, genesis and alteration of aluminosilicate bearing schists and gneisses at Springfield, near Williamstown, South Australia(1975) Ringenbergs, W. H.; School of Physical SciencesThe high grade aluminosilicate bearing schists and gneisses are believed to be due to prograde regional metamorphism to T 600-700oC, P 4-6kb under falling potassium activity. This leads to dealkalisation of K-feldspars and immediately precedes or accompanies the F2 deformation. Shearing also seems an important genetic control. The dominant rock types are subdivided: 1. Aldgate Sandstone Equivalent 2. High Grade (sillimanite) zone Sillimanite Quartz Gneiss Kyanite Quartz Gneiss Muscovite Quartz Gneiss Kyanite Muscovite Kaolinite Shear rocks Schists (coarse) Tremolite marker horizon 3. Kyanite Andalusite zone Sandstones, Marbles, Schists, and Calc-silicate rocks The retrogression of the aluminosilicates took place in two distinct steps. Preceding the F3 deformation and associated with initial stages of thrusting, muscovitisation occurred, producing green muscovites (referred to by Alderman as Damourite) and sericite pods in the high grade schists. Introduction of potassium and water was involved. Following the F3 deformation kaolinisation of sillimanite and K-feldspar occurs. This is a low temperature hydrothermal alteration. X-Ray diffraction studies demonstrate the equivalence of the green muscovite and sericite and show the alteration of sillimanite to kaolinite.Item Open Access Dating and characterising a newly discovered sedimentary basin in the east Tennant region(2021) Rasch, S.; School of Physical SciencesAn unknown sedimentary sequence was discovered in the newly defined Brunette Downs Rift Corridor. The sequence is interpreted to lie within a half graben structure, beneath the Helen Springs Volcanics (297m) and extend to basement (724m). This study analyses these sediments to establish when they were deposited, under what conditions, and from what source. The unknown sedimentary rocks were defined as Units A through F, with a notable unconformity splitting units A and B. Maximum depositional ages were established above and below the unconformity using U–Pb detrital zircon dating. These yielded ages of 902 ± 34 Ma and 1649 ± 37 Ma respectively, based on the youngest concordant grain. In-situ laser ablation inductively coupled plasma reaction cell mass spectrometry (LA-ICP-MS/MS) Rb–Sr dating established a minimum depositional age of 1547 ± 13 Ma for shales in the sequence below the unconformity. Initial 87Sr/86Sr values and rare earth element compositions of these shales suggest that this age dates diagenetic phases that grew in equilibrium with Mesoproterozoic sea water. Therefore, this age may effectively date deposition of this sedimentary package. NDIBK10 sediments were compared to a database of surrounding sedimentary and igneous provinces. The age distribution of detrital zircon grains show that the unknown sediments are most similar to the lower McArthur Group (Glyde Package), or Bullita Group (Favenc Package). The shale Rb–Sr age of 1547 ± 13 Ma suggests that the Favenc Package is the most likely of these possibilities. The sandstones are likely sourced from the Aileron Province, possibly due to uplift related to the Chewings Event. La/Sm ratios from shales indicate that the source was primarily felsic, comparable to average upper continental crust (AUCC). Th/U ratios and Ce anomalies indicate that ocean waters were oxic/sub-oxic becoming more oxic during deposition.Item Open Access The fractionation of copper isotopes in granitic and mafic intrusions: mafic enclaves in the Mannum granite, a case study(2021) Pring, O. T.; School of Physical SciencesThe transfer of material between mantle-sourced magma and evolved magmatic rocks may provide a mechanism for the transportation of metals such as copper, Cu, to the crust. The Mannum granite provides a case study as the A-type granite is synchronously accompanied by mafic enclaves, providing a mafic-felsic interface with differing degrees of mixing/mingling. This mafic-felsic interface shows different mechanisms of transportation such as transport of xenocrysts, compositional rimming (rapakivi feldspars) and change in overall bulk chemistry. Samples of both the granite and mafic enclaves were taken, with a focus on Cu isotope analysis which characterises Cu behaviour between the mafic enclaves and granite and shows whether any copper has been assimilated from a highly fractionated source. This study used petrography, whole rock and mineral major and trace element chemistry and whole rock Cu isotope analysis. Processes such as fractional crystallisation and magma mixing/mingling provide mechanisms for the transfer of material between the granite and the intruding mafic enclaves. There is evidence of the transfer of material in the hybridised zones, particularly the formation of rapakivi feldspars and xenocrysts from both phases. Rare earth element signatures show mineral growth has occurred prior and post injection of mafic magma into the Mannum granite and that magmatic transfer is most applicable to lithophile elements. Cu isotope results show that δ65Cu values generally increase with decreasing copper concentrations and range from -0.12 to 2.34‰. The range of δ65Cu values is in line with those reported in mantle derived rocks and follow Rayleigh fractionation curves. Cu isotope analyses further our understanding of Cu isotope behaviour and can be applied to ore-forming environments. Other stable transition metal isotopes could be paired with Cu isotopes, such as Zn and Fe, to further examine the role of any redox reactions.