Academic literature on the topic 'Cloncurry'

An unknown sedimentary sequence was first recorded during a Geoscience Australia/ Geological Survey of Queensland/ pmd*CRC deep seismic reflection survey in the Mount Isa Inlier and adjacent undercover terrains, during 2006/07. The sequence occurs unconformably underneath the Carpentaria Basin succession in the Julia Creek area, east of Cloncurry in north Queensland, and is named the Millungera Basin. A section through the basin is recorded along seismic line 07GA–IG1, recorded between north of Cloncurry to east of Croydon. In this section three internal sequences are noted—with two strongly reflective units separated by a poorly reflective unit. As well as deep crustal seismic reflection profiles, magnetotelluric profiles were collected along the same traverse. These data show a moderately conductive Millungera Basin underlying the strongly conductive Carpentaria Basin. Zones of limited reflectors beneath the basin in the seismic sections have been interpreted as granites, raising the possibility of raised geothermal gradients. The Millungera Basin may comprise a potential geothermal target. The Millungera Basin sequence is interpreted to overlie granites. Adjacent Proterozoic granites of the Williams Batholith are known to be high heat producing granites, containing high levels of potassium thorium and uranium. The hydrocarbon potential of the basin is similarly uncertain. Strong reflectors in the seismic sections may be coal beds. Although the depth of the basin in the seismic section is insufficient to have reached the oil window, interpretation of gravity profiles by Geoscience Australia suggest the basin deepens to the south, possibly reaching 4,000 m. If fertile beds have reached the oil window, the structurally more complex eastern side of the basin may contain petroleum traps. The age of the rocks in the Millungera Basin is not known. Constraints from the seismic suggest between the early Mesoproterozoic and the Middle Jurassic. Investigations into the nature of the basin are continuing. A more detailed magnetotellurc survey is being undertaken to better define the shape of the basin. In order to reliably describe the basins components, a deep drilling program is required.

The research described in this thesis has led to an understanding of the geochemical conditions controlling the formation, paragenesis and distribution of oxide zoner copper species in the Eastern Fold Belt of the Mt. Isa Inlier. This area is also known as the Cloncurry Complex. The regional geology and genesis of the copper deposits is reviewed and the deposits of particular interest to the study are described. Oxidation of pyrite and chalcopyrite by oxygen-bearing groundwater and the sources and mechanisms by which anions are carried by groundwater to reaction sites to form secondary copper species are discussed. Physical and chemical conditions control the development of particular species. Equilibrium phase diagrams have been constructed to represent stability fields. An explanation for the relative abundance and spatial distribution of the basic copper phosphates is provided. Stability field data supported by observations made on deposits in the Cloncurry district and elsewhere provides a basis for assessing the paragenesis and distribution of secondary copper species in this and similar environments. This is discussed and illustrated using the Great Australia mine as a model
Master of Science (Hons)

Several deposits in the Mt Isa - Cloncurry region have been studied, including those held by Australian Resources near Selwyn (Plume, Slate Ridge, Mobs Lease and Straight Eight),in particular, with respect to cobalt and gold mineralisation. Cobalt is associated with pyrite, pyrrhotite and arsenic sulfosalts. Other cobalt deposits in the Eastern Fold Belt of the Mt Isa Block were studied; these include the Queen Sally, Lorena and the Great Australia mine. Varying styles of Co-bearing mineralisation were encountered. In the Queen Sally mine a curious vanadium - substituted heterogenite has been found. This is only the world's second reported occurrence of this mineral of the halotrichite group. At the Great Australia, primary Co mineralisation has been shown to be confined to one generation of cobaltian pyrite. Several generations of pyrite are noted for this and other deposits.
Master of Science (Hons)

The Mount Dore and Merlin deposit, discovered in 2008 by Chinova Resources (previously Ivanhoe Australia), is the world's highest grade Mo-Re deposit. The deposit is located in the Cloncurry District of the Mount Isa Inlier, Australia; a region renowned for its IOCG type mineralization. In the same year the Lanham's Shaft prospect, another Mo-rich occurrence was found 50 km to the north of the Merlin deposit. These discoveries have created a new exploration paradigm, and this thesis represents the first in-depth study of this new mineralization type. This work integrates detail core logging, petrography, geochronology, and trace element and isotope geochemistry. The Mount Dore and Merlin deposit is hosted by the Proterozoic Kuridala Formation metasedimentary package, which is composed of interbedded phyllites and carbonaceous slates above calc-silicate rocks, and silicified siltstones at the footwall. The Mount Dore granite is thrust above the metasedimentary rocks and overlies the bulk of the mineralization. The mineralization consists of a Cu-polymetallic stage (chalcopyrite ± sphalerite ±± galena) (Mount Dore) mainly hosted by the carbonaceous slates in angular clast-supported carbonate breccias, and Mo-Re mineralization (Merlin) that locally cuts the Cu-polymetallic mineralization, mainly along or near rheologic boundaries between the carbonaceous slates and the calc-silicate rocks. The bulk of the Mo-Re appears as infill of matrix-supported breccias with rounded clasts. The hydrothermal alteration is highly complex, consisting of three main stages, from oldest to youngest: Na-(Ca), Cu-polymetallic, and Mo-Re. These stages were dated using UPb in titanite and Re-Os in molybdenite at the Mount Dore and Merlin deposit and at the Lanham's Shaft prospect. The Na-(Ca) alteration (1557 ± 18 Ma) is similar to a regional Na-(Ca) alteration event with formation of albite + amphibole ± quartz ± titanite ± apatite ± carbonates. The alteration fluids are interpreted to be bittern brine(s) and the widespread regional Na-(Ca) alteration is thought of having been responsible for the release of potassium, iron, barium, and possibly copper and carbonate from the regional metasedimentary rocks. The Cu-polymetallic mineralization is accompanied by K-feldspar + tourmaline + carbonates ± quartz. This alteration stage is also interpreted to have formed by a bittern brine fluid that reacted with the metasedimentary host rocks. This reaction resulted in a strong decrease in the ƒO2 of the fluid, due to the minor graphite contained in the carbonaceous slates that host the Cu-polymetallic mineralization. The ƒO₂ drop is proposed as the main chemical mechanism responsible for the sulfide precipitation, and the sulfur was sourced from both the bittern brine and the metasedimentary host rocks. Zinc, and at least part of the Pb and Ag, was possibly sourced from the carbonaceous slates. The third hydrothermal stage can be subdivided into three events, with the first and main event being responsible for the bulk of the Mo-Re mineralization and the last two events being remobilizations of the first event. The main Mo-Re event occurred at ~1535 Ma and formed the strongly mineralized breccias that were accompanied by K-feldspar ± chlorite alteration. Fluid derived from a Williams-Naraku type felsic intrusive is proposed as the source of the mineralization with ore mineral precipitation triggered by a strong to moderate ƒO₂ drop during fluid reaction with the metasedimentary host rocks. Again, the sulfur is thought to be derived from both the mineralizing fluid and the host rocks. The second, relatively minor, Mo-Re event occurred at ~1521 Ma and formed veins and disseminations that extend from the Mo-Re breccias into the calc-silicate rocks for several metres. This event is inferred to have developed from the previously formed Mo-Re mineralization by remobilization, due to the emplacement of the Mount Dore granite (~1517 Ma), with formation of K-feldspar + chlorite ± apatite ± rutile ±± monazite. A ƒO₂ drop was again the ore precipitation mechanism, but the ƒO₂ decrease was not as strong in this mineralization, due to the relatively oxidized nature of the calc-silicate host rocks compared to the proximity (partly hosting) of the bulk of the Mo-Re mineralization to the carbonaceous slates. The sulfur was sourced from the previously formed molybdenite and therefore both mineralization styles have similar δ³⁴S signatures. A very minor Mo-Re event occurred at ~1500 Ma and consists of millimetric Mo-Re veins in carbonate ± chlorite veins. This event was likely formed in response to the thrust of the Mount Dore granite over the metasedimentary host rocks, which is possibly responsible for the formation of the molybdenite stylolitic veins, which are a common feature in the deposit. The Lanham's Shaft prospect displays a similar hydrothermal alteration evolution, except that significant remobilization of the Mo-rich mineralization did not occur at this location. However, the absolute timing of the Na-(Ca) alteration (~1575 Ma) and Mo-rich mineralization (~1560 Ma) is earlier than at the Mount Dore and Merlin deposit. These older ages indicate the existence of hydrothermal activity with mineralizing capability during a time period that has previously been regarded as unprospective for ore deposit formation. The mineralization at the prospect is less abundant in grade and tonnage than the deposit, consisting of mineralized veins. The bulk of the Cu-rich and Mo-rich veins are a few metres from the carbonaceous slates, hosted in calc-silicate rocks. The distance of the mineralization to the graphitic rocks resulted in a weaker ƒO₂ drop in both stages. The mineralizing fluids are interpreted as also felsic igneous sourced and mixing of sulfur between the fluids and the metasedimentary rocks also occurred. The Merlin and Mount Dore and Lanham's Shaft mineralization have clear spatial and temporal affinities with IOCG mineralization in the Cloncurry District. Broad genetic relationships between these mineralization styles are also likely, so a denomination for this this new mineralization style is proposed as Mo-rich IOCG type deposits. The key criteria and ingredients for such deposits are: 1. Mo-rich felsic igneous source(s) and; 2. Suitable tectonic trap(s) contained within, or at close proximity to, reduced host rocks (e.g. carbonaceous or graphitic metasedimentary rocks).

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The Cloncurry District, Queensland, is a classic Iron Oxide Copper Gold (IOCG) terrain. However, the geochemical characteristics of the numerous mafic intrusives (dominantly dolerite dykes), which are often spatially and temporally associated with mineralisation, have never been studied in detail. Specifically, the newly described dolerite-associated Great Australia-Taipan-Mongoose-Magpie (GATPMM) deposits are thought to represent a distinct Cu-Co-carbonate-rich, Au-poor style of IOCG mineralisation that has not been documented elsewhere in the district. Trace element geochemistry provides evidence that these dykes formed from lower crust fractionation and magmatic ascent throughout intracontinental extension. There are significant REE links to previously studied granites of the Naraku and Williams Batholith within the district, indicating a similar melt source for both igneous lithologies. Geochronological studies of hydrothermal titanite (1515± Ma) and apatite (1177±37 Ma and 1179±41 Ma) from the Mongoose prospect provide constraints on the age of initial intrusion and alteration and provide evidence for thermal-tectonic activity within the Eastern Succession ca. 1100-1200 Ma, possibly related to the Albany-Fraser and/or Musgravian Orogenies. Geochemical relationships between mineralised dolerite samples from the CuDECO Rocklands deposit and local barren dolerite samples are also analysed and display geochemical similarity. This is consistent with the interpretation that dolerite geochemistry alone is not an indicator of prospectivity and is not linked to the distribution of mineralisation.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016

The E1 Group of iron oxide-copper-gold (IOCG) deposits is located in the metal-rich Cloncurry District of northwest Queensland. The E1 Group contains a total resource of 47 Mt averaging 0.72% Cu and 0.21 g/t Au, and has not been previously investigated in detail. This study aims to understand the genesis of the E1 Group by characterising its geology, alteration paragenesis, ore chemistry, structural controls, and mineralising fluid properties. These features are investigated using drill core logging, petrography, whole-rock geochemistry, microprobe analysis, LA-ICP-MS U-Pb dating, 3-D implicit geological modeling, fluid inclusion studies, and SHRIMP and IRMS oxygen and sulfur stable isotope analyses. The E1 Group comprises three distinct orebodies: E1 North, E1 East and E1 South. The orebodies are hosted mainly in marble and carbonaceous metasiltstone of the Corella Formation (1750–1720 Ma). The metasedimentary rocks are intercalated with mineralised clastic metavolcanic rocks and barren meta-andesite of the Mount Fort Constantine Volcanics (~1750 Ma). These rocks were intruded by Ernest Henry Diorite, cut across by a discordant, polymictic, breccia, and then intruded by dolerite. Drill core logging, petrography and Mineral Liberation Analysis were used to study the E1 Group alteration textures and styles. They show that E1 Group mineralisation is typified mainly by fine- to medium-grained (<500 μm) stratabound and shear zonehosted replacement bodies. The ores are typically layer-controlled; some ores are also in veins. The discordant breccia is barren, and pre-dates mineralisation. The alteration paragenesis was constrained with drill core logging, petrography, and Energy-Dispersive and Wavelength-Dispersive analyses. The E1 Group paragenetic sequence is characterised by three major stages. Stage 1 is dominated by albite (- hematite), with lesser quartz, actinolite, scapolite, and titanite. The second stage is broken into three sub-stages. Stage 2a is dominated by magnetite, fluorophlogopite and fluorannite, fluorapatite, K (-Ba)-feldspar and lesser quartz and pyrite. Stage 2b is a minor phase of albite (-hematite)-rutile-ilmenite alteration. Stage 2c is composed of ankeritic carbonate, magnetite, pyrite, and minor chalcopyrite. Stage 3 is the main mineralising event, and is dominated by carbonate (-Fe-Mn), chalcopyrite, barite, fluorite, pyrite, chlorite, sericite; trace amounts of monazite, bastnäsite, uraninite and coffinite are also present. Whole-rock geochemical analysis indicates that the ores are highly enriched in Fe, Ba, F, P, and locally Mn, and are less enriched in U, LREE, Co, Mo, As, Sn, Ag while depleted in Si, Na and K. Delineation of the deposit zonation patterns shows a transition from the E1 North orebody into a barren magnetite-apatite ± pyrite zone to the southwest. Barium and fluorine are elevated over 200 m from mineralisation. The relatively new technique of three-dimensional implicit geological and geochemical modeling was used to study the structural history and controls of the E1 Group. The deposit is hosted within a series of northwest-plunging folds that formed during regional D2 deformation event and peak metamorphism. The E1 North and E1 South orebodies are hosted in the hinges of the E1 North Antiform and E1 South Synform, respectively, while E1 East occurs in the limb of the E1 East Antiform. The E1 North Antiform is cut by the northeast-southwest-trending brittle-ductile E1 North Shear Zone that dips ~70° northwest. The shear zone is an R-shear of a dextral Riedel structure caused by transpressional movement on the regional Mount Margaret Fault during local D3 / regional D4. Implicit geochemical modeling suggests that the spatial distributions of Cu, Au, Fe, U, Co, Mo, and La are controlled by the fold hinges and E1 North Shear Zone, and the highest-grade orebody occurs at their intersection. Drill core and petrographic observations indicate that ore formation took place around local D3 / regional D4. A later local D4 / regional D5 event caused brittle reactivation of the E1 North Shear Zone and formed northeast-southwest-trending reverse-oblique faults at E1 South that offset mineralisation. Fluid inclusion analyses were conducted on Stage 2a quartz and Stage 3 barite to determine the composition of the mineralising fluids. Stage 2a quartz hosts a primary fluid inclusion assemblage, 1A, that is characterised by halite-rich, aqueous liquid-solidvapour fluid inclusions with >50 wt% NaCl(eq); the assemblage was heterogeneously trapped. Stage 3 barite hosts two major fluid inclusion assemblages (2A and 2B). Assemblage 2A comprises primary, moderate to low salinity (<15 wt% NaCl(eq)) aqueous liquid-vapour, inclusions that homogenise between 160° and 190°C. Assemblage 2B is composed of secondary, moderately saline (<9 wt% NaCl; <18 wt% CaCl₂), liquidvapour inclusions. In order to constrain fluid and metal sources and precipitation mechanisms, the δ¹⁸O(VMSOW) values of Stage 2a quartz-magnetite pairs, along with the δ³⁴S(CDT) values of and Stage 3 barite-chalcopyrite pairs, were studied; Stage 2 pyrite was also measured. For fine-grained ores, the in-situ Sensitive High Resolution Ion Microprobe method was used, while conventional ex-situ Isotope Ratio Mass Spectrometry was used for vein samples. Stage 2 quartz δ¹⁸O values at E1 North have a narrow range of +12.7 to +14.8‰. In contrast, magnetite δ¹⁸O values are characterised by a wider range from 0 to +8‰. Calculated isotopic equilibrium temperatures from quartz and magnetite range from 350° to 540°C, and the calculated δ¹⁸O range of the fluid at these temperatures is +8.4 to +10.9‰. Stage 3 chalcopyrite δ³⁴S values are distinct between E1 North (–5.8 to +2.7‰), E1 South (+1.7 to +17.3‰), and E1 East (+12.5 to +16.9‰). Stage 3 barite δ³⁴S values vary from +6.7 to +21.2‰ in E1 North, +19.1 to +29.5‰ in E1 South, and +5.6‰ to +26.5‰ in E1 East. Vein-hosted barite δ³⁴S values are 5 to 10‰ lower than those in fine-grained samples. Stage 2 pyrite is typically 1 to 2‰ higher than Stage 3 chalcopyrite. Calculated equilibrium temperatures for Stage 3 barite and chalcopyrite in fine-grained samples range from 230° to 340°C; vein-hosted samples did not reach equilibrium. Estimated trapping pressures of barite 2A fluid inclusions, based on these temperatures, range from 2.2 to 3.3 (±0.5) kbar. This corresponds to a depth range of 8– 12 km. The estimated values of δ³⁴S(Σ)ₛ range from +4.9 ± 5.3‰ at E1 North, to +15.9 ± 3.6‰ at E1 South. The δ¹⁸O(fluid) and δ³⁴S(Σ)ₛ values at E1 North, coupled with the high salinity of 1A fluid inclusions, are consistent with those from a magmatic-hydrothermal fluid. The F-UREE enrichment of the paragenesis suggests that the magma was an evolved, alkaline, granite. It is speculated that this granite was related to the (1550–1490 Ma) Williams- Naraku Batholith; it may have supplied some of the Cu and Au. The shifts in the values δ³⁴S(mineral) and δ³⁴S(Σ)ₛ at E1 South can be explained by mixing of the magmatic fluid with a shallower fluid that had equilibrated with the Corella Formation host rocks. Covariance of the δ³⁴S of barite and chalcopyrite between E1 North and South suggests that both fluids supplied SO²⁻₄. Ore precipitation was likely caused by salinity decrease as a result of fluid-fluid mixing. Dilation in the E1 North Shear Zone and fold hinges during local D3 / regional D4 provided the main conduits for mixing of the mineralising fluids.

The Saxby and Mt. Angelay Igneous Complexes represent the volatile rich, post ~1530 Ma granitoids of the Williams Batholith, and have been considered to be a possible source of magmatic-hydrothermal fluids that produced IOCG deposits in Cloncurry district. The evolution of these igneous complexes is studied in this thesis with the ultimate aim to understand the chemistry of magmatic fluids and their involvement in ore genesis. These igneous complexes contain a variety of intrusions including mafic, intermediate and felsic members and their fluid evolution was examined by several bulk and micro-analytical techniques. The distribution of rock units and their contact relations were obtained from field observations and regional and detailed mapping. The Saxby (SIC) and Mt. Angelay (MAIC) Igneous Complexes are dominated by metaluminous, potassic, magnetite bearing intrusive rocks, which intruded into the calc-silicate rocks of the Mary Kathleen Group and psammo-pelitic rocks of the Soldiers Cap Group between 1530 and 1500 Ma. The major rock types in the SIC include granites and a large number of mafic intrusions, with limited pulses of intermediate magmas, typically observed at the magma mixing/mingling locations. The MAIC apparently represents a more evolved pluton, which has limited mafic intrusions with more intermediate rock types and abundant felsic rocks. Other major rock types and structures include magmatic-hydrothermal transition veins and ‘brain rocks’ of Mt. Angelay, mixed/mingled rocks and explosive breccias of the SIC, and late igneous phases of pegmatites and aplites. Intense sodic/ sodic-calcic alteration is abundant in both complexes, complicating geochemical interpretation. Petrographic and geochemical studies were used as tools to distinguish various rock types and magmatic crystallization processes from sub-solidus hydrothermal processes. The major and trace element studies together with rare earth element (REE) patterns and field observations suggest different magma sources for the mafic and felsic rocks. The REE patterns, depletion in Eu, Sr, P and Ti, and Y-undepleted nature of K-rich, abundant felsic intrusions suggest a crustal source which is more likely depleted in garnet, titanite, apatite, pyroxenes and/or amphiboles and enriched in plagioclases. In mafic and intermediate intrusions, the decrease in CaO, Nb, Sr, Sc, V and TiO2 with increasing SiO2, together with negative Eu anomalies, suggested that fractional crystallisation of plagioclase and amphibole were prominent processes involved in the formation of the more silicic phases from mafic magmas. REE patterns also suggest that this mafic source region was enriched in pyroxenes, amphiboles, apatite and titanite and depleted in garnet. The volatile evolution of the SIC and MAIC intrusions was particularly estimated from halogen (F/Cl) abundances and ratios of hydrous minerals including biotite, hornblende and apatite, and from calculated halogen activities of magmatic fluid in equilibrium with biotite. The F and Cl concentrations of ferromagnesian minerals highly depend on Fe and Mg contents; however, they show variable rates of compatibility with fractionation that may have influenced the halogen concentration of the final magmatic-hydrothermal fluid. The halogen contents of both whole rocks and minerals show high F and Cl contents in mafic rocks and gradual loss in Cl with crystallization. The majority of F analyses in the whole rocks are below detection, but the minerals show major increase in F contents from mafic to intermediate rocks. The halogen variability in intrusions depends on a number of factors including bulk rock chemistry, wall rock alteration and Fe-Mg avoidance. Fluid inclusions were used as a tool to understand the magmatic-hydrothermal evolution of the SIC and MAIC and the intrusions contain a variety of primary and secondary fluid inclusions. The primary magmatic fluids of the SIC and MAIC include a common, abundant CO2 rich fluid phase, which may have been sourced from mafic magma. High salinity, primary, multisolid inclusions of Mt. Angelay brain rocks represent magmatichydrothermal fluids; in which their magmatic origin is also confirmed by PIXE halogen ratios. The multisolid inclusions show very high salinities (38-60wt% NaCl equivalent) and high homogenization temperatures ranging from 450-600°C and more. Secondary inclusions of L+V+S (16-46wt% NaCl equivalent) and L+V (1-30wt% NaCl equivalent) are present in all the SIC and MAIC rocks including granites, brain rocks and breccias, and they homogenize in between 140-300°C and 100-250°C respectively. The field and analytical studies suggest that the Saxby breccia pipes and Mt. Angelay brain rocks represent the release of magmatic fluids at the final stages of magma evolution (Chapter 2 & 6). It is suggested that the process of magma mingling and the variable CO2 input from mafic intrusions have played major role in the formation of breccias and brain rocks. The fluid inclusion P-T estimations from these magmatic hydrothermal locations together with geochemical and mineral chemical observations also provide clues to the overall volatile evolution of the mafic and felsic magma, and their possible role in IOCG genesis. The metal and element budget of some Cloncurry ore deposits and SIC and MAIC intrusions are compared as the fluid inclusions provide a direct correlation. The primary fluid inclusions assemblage in Mt. Angelay brain rocks (CO2 inclusions + multisolid inclusions) is similar to that found in the most obviously granite-related IOCG deposits (especially Ernest Henry), and is verified in detail by PIXE and LA-ICP-MS analysis. The element concentrations, ratios and Fe, Cu, Mn and Zn contents of multisolid inclusions from these two settings show similarities, which suggest a magmatic involvement in the IOCG ore genesis of Cloncurry. However, fluid mixing is also suggested as a major process for the formation of ore deposits. Although many previous studies supposed that granites were crucial in the magmatic-to- IOCG connection, the data collected during this study suggest that mafic intrusions played major roles in the evolution of Saxby and Mt. Angelay Igneous Complexes and in the formation of some of the Cloncurry ore deposits.

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The Ernest Henry Iron-oxide Copper Gold (IOCG) deposit is by far the largest in the Eastern Succession of the Mount Isa Inlier. In the current genetic model, the release of CO2 from fluids sourced from enriched mantle was critical to brecciation and mineralisation. However, a weakly mineralised and brecciated shear zone within the orebody named the ‘Inter-lens’ separates the orebody into two distinct lenses. The Inter-lens was not well reported early in the life of the mine and has not been taken into account in the current ore deposit models. Establishing the relative timing of the Inter-lens structure provides strong geological constraints for the formation of the orebody. In this study, optical petrographic investigations, Scanning Electron Microscopy (SEM) and Mineral Liberation Analysis (MLA) were used to investigate the protolith. Key mineral relationships and textures were assessed to reveal the paragenesis of the Inter-lens. Structural observations in oriented drill core complemented underground mapping of exposures of the Inter-lens to reveal the deformational history of the Inter-lens with respect to the Ernest Henry orebody. The protolith was revealed to be Mount Fort Constantine Metavolcanics that have undergone intense deformation with a metasomatic evolution broadly consistent with the main orebody. Mineralisation stages overprinted tectonic fabrics via veining, replacement and infill, providing direct evidence that the Inter-lens is a pre-mineralisation structure. Preservation of the Inter-lens during brecciation and mineralisation of the Ernest Henry deposit requires that the currently accepted ‘explosive’ breccia model must be revised.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016

Major geophysical lineaments are commonly associated with active to ancient faults at a variety of scales. They may correlate with the edges of rifts, depositional basins, orogenic belts or plate boundaries, and they commonly represent corridors along which deformation, mineralisation, magmatism and intra-crustal heat flow is concentrated. In many instances, they encompass a number of these features. The Cloncurry Lineament, a major feature in wavelet processed magnetic and gravity potential field (worm) data over the Mount Isa Inlier Eastern Succession, displays several such characteristics. It is over 200 km long and inferred to extend to at least 30 km depth. It delineates a contact between two major Paleoproterozoic sedimentary sequences, implying that it originated as a normal fault during rifting and basin formation. Magnetic forward modelling results suggest it corresponds to the eastern margin of a 5-10 km wide deformation zone within the calc-silicate Doherty Formation; the Cloncurry Fault Zone. The Cloncurry Fault Zone encompasses a continuum of deformation from ~1.6 to1.5 Ga. While D₁-D₂ deformation is regionally dominant, D₃ is more significant in the fault zone itself as evidenced by much lower temperatures during mylonitisation (500- 350°C) and the superimposition of mylonitic fabrics on Maramungee aged (~1550 Ma) granites. Mapping and structural fabric analysis of the Cloncurry Fault Zone show that D₃ involved WSW shortening, sub-perpendicular to a pre-existing basin-bounding fault. D₃ created an anastomosing shear zone system displaying variable slip vectors with synchronous variably NNW or SSE plunging folds. Penetrative fabrics are attributed to strain partitioning in the D₃ event, rather than a more complex history of overprinting. During D₄-D₅ a sinistral Riedel strike-slip fault system formed, coincident with massive Na-Ca brecciation. Intrusive magmatism and IOCG, Cu, and Au mineralisation also occurred during the D₃-D₅ history of the Cloncurry Fault Zone, highlighting its importance as a magmatic and hydrothermal pathway. Sodic-calcic (Na-Ca) metasomatism, associated with Cu-Au mineralisation in the Mount Isa Eastern Succession, is widely recognised but heterogeneously distributed, and difficult to map regionally. Hence, a method to map Na-Ca alteration remotely was developed. ASTER Band ratios were ineffective for mapping amphiboles and carbonates as a proxy for sodic-calcic alteration due to numerous mineral species having similar absorption features in ASTER band 8. Therefore, the low Kradiometric and highly magnetic properties of Na-Ca alteration were integrated with ASTER band 8 to form a Sodic-Calcic Alteration Index. The Index highlights albiteactinolite- magnetite assemblages that are coincident copper with Cu-Au mineralisation in the Eastern Succession, and the Index is useful for regional exploration in the Mount Isa Inlier. Weights-of-evidence analysis identifies the Cloncurry Lineament as an important crustal-scale control on Au, Au-Cu, Cu-Au, and Cu mineralisation, and autocorrelation is used to identify local structural controls within the broad regional control. This integrated approach, using worms and weights-of-evidence and autocorrelation, may prove a useful exploration tool for mineralised terrains under Phanerozoic cover. Mineralisation along the Cloncurry Lineament appears to be facilitated by two main factors. Firstly, it is associated with long, deep-crustal structure lying above dynamic lower crust/mantle, which has concentrated magmatism and metasomatism. Secondly, the associated structures have been repeatedly reactivated; increasing the chances that dilation may coincide in space and time with upflow of mineralising fluids to form a mineral deposit. These two factors appear to be consistent in several of the world's major mineralised lineaments.