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  • The Olympic Copper-Gold Province of the eastern Gawler Craton of South Australia, in hosting the Olympic Dam, Prominent Hill, Carrapateena and Moonta-Wallaroo deposits, has the greatest known iron-oxide, copper, gold and uranium (IOCGU) metal endowment of any geological province on Earth. The historic Moonta-Wallaroo copper-gold mining fi eld is within the Moonta sub-domain and is hosted by the ~1750 Ma Wallaroo Group that preserves some evidence of evaporitic sedimentation, similar to other major iron oxide-copper-gold (IOCG) provinces in Australia and North America. Observations in the Moonta-Wallaroo district indicate that mineralisation was broadly associated with intense metasomatic alteration, intrusion of granites and gabbros of the Hiltaba Suite, moderate grade metamorphism and intensely partitioned deformation. The driving force of this extensive ~1600 to 1500 Ma hydrothermal, magmatic and tectonic event was a major thermal pulse, the cause of which remains under debate. The vein-style mineralisation in the Moonta-Wallaroo district developed in ground prepared by ductile shearing. Widespread sub-economic copper mineralisation in the region is associated with intense regional magnetite-bearing skarn-like alteration of the Cloncurry type, with oxidation and hematite replacement of early magnetite. Targeting of structurally-controlled demagnetised zones and the oxidised margins of magnetic anomalies has been applied successfully in the northern Olympic Copper-Gold Province (e.g. Prominent Hill) and is also applicable to the Moonta-Wallaroo region. The recently discovered copper-gold mineralisation at the Hillside copper-gold deposit demonstrates the continued prospectivity of this southern portion of the Olympic Copper-Gold Province.

  • <p>The pmd*CRC Y2 project operated for a little over three years, and in this time has more than met its goal and deliverables. This final report brings together a vast wealth of new knowledge, information and data, and is accompanied by a comprehensive DVD with all the source and derivative data, various presentations, papers, animations and posters etc. <p>At the start of the project the Y2 team was inexperienced in building 3D maps, and the early attempts were relatively crude and clumsy. Now, after more than three years of learning and testing, the project team has achieved an excellent result and methodology for building rigorous 3D maps. The main achievement of the Y2 project has been the building of comprehensive 3D maps of Kalgoorlie-Kambalda and the Norseman-Wiluna region. The maps were built on a foundation of 2D solid geology maps from government agencies, universities and industry. These data were integrated with various geophysical data sets (seismic reflection, refraction, broadband recording, receiver function, gravity and magnetic data, plus various derivatives such as 'worms'), geochemical data sets (e.g., from P624), and geochronological data sets (from AMIRA P624 and earlier projects as well as published data). <p>The result of this integration is a more-holistic understanding of the EYC from a five questions approach. This understanding is outlined both in the maps and associated data sets, as well as this final report. The Y2 project has had its principal impact on answering the architecture question (Q2). The project has contributed to the geodynamics (Q1), drivers and pathways (Q3), fluids and their sources/reservoirs (Q4), and metal transport and deposition (Q5) questions. <p>The report is structured around the six key deliverables. Chapter 1 sets the geological scene and defines the tectono-stratigraphic nomenclature used throughout. Chapter 2 describes the work flow process devised to build the 3D maps. Chapter 3 discusses the seismic reflection and wide-angle reflection data and interpretations. Chapter 4 incorporates the mapping of the lithosphere and its velocity structure by using broadband seismic recording (tomography) and receiver function data (velocity profiles). Chapter 5 concerns the mapping of the chalcophile elements. Chapter 6 assesses the utility of 3D as opposed to 2D methodology, and discusses the structural history. Chapter 7 is a brief outline of the prospectivity analysis conducted by the pmd*CRC A1 project using Y2 project data. Chapter 8 is a synthesis chapter arranged by the five questions. Many of the new ideas and understanding built on the data and observations of the earlier chapters are developed. Chapter 9 has the project conclusions. Chapter 10 presents the scope of the next phase of the CRC as recommendations for future work. Extensive appendices (available only in the pdf file [DVD]) follow each chapter, including all pertinent publications and deliverables. <p>Acknowledgements as well as an outline of all data sources and intellectual property, and references complete the report. <p>Many authors contributed; Blewett and Hitchman edited the volume.

  • The Tanami region has become one of Australia?s premier Proterozoic gold provinces, having already produced 122 t of gold, and still has high exploration potential. This region contains more than 60 gold occurrences including three established gold fields (Dead Bullock Soak, The Granites and Tanami) as well as several significant gold prospects (Groundrush, Titania, Crusade, coyote and Kookaburra). The Callie deposit (>5 Moz total resource) located in the Dead Bullock Soak goldfield is currently the largest mine in this region. Fluid inclusion studies indicate that the ore fluids in the Dead Bullock Soak and The Granites goldfields were low to moderate salinity (4 ? 10 wt.% NaCl eq), moderate to high temperature (260 ? 460 ?C) and gas rich. In contrast, ore fluids in the Tanami goldfield were low temperature (120 ? 220 ?C) with only minor CO2. O and H isotopic data are consistent with either a metamorphic or magmatic origin for the ore fluids with some mixing with meteoric fluids evident in the Tanami district. The fluid inclusion data also indicate that the deposits have formed over a range of physico-chemical conditions and depths. Groundrush appears to have formed at the greates depths and has the most reduced (CH4-rich) fluids. The Granites goldfield and the Callie deposit formed at shallower depths. The Granites fluids were CO2-rich but also had variable N2 and CH4. The Callie fluids show only small variations in temperature and salinity and are more oxidised with only CO2 and N2 being detected. The Tanami deposits appear to have formed at the shallowest levels and are dominated by low-salinity aqueous fluids, although some CO2-bearing fluids have also been detected. Considerable uncertainty surrounds the age of gold mineralisation. The spatial relationship between many of the gold deposits and granitoids has led to proposed genetic links between granite intrusion and mineralisation. These granites have since been dated at between 1825 and 1795 Ma. Preliminary 40Ar/39Ar results from sericite from the Carbine pit in the Tanami goldfield yields a total gas age of 1810 Ma, i.e. similar to the age of the granites. However, 40Ar/39Ar analysis of biotite in mineralised veins from Dead Bullock Soak indicate an age of 1720 ? 1700 Ma. This suggests that mineralisation at Callie may be related to fluid migration driven by the Late Strangways Orogeny that was responsible for widespread deformation and metamorphism in the Arunta Province to the south-east. Results of this study indicate that gold deposits of the Tanami region are surprisingly diverse, with some being basalt and dolerite hosted, some in banded iron formations and some being sediment hosted. Moreover, fluid inclusion data shows that the deposits formed over a range of depths and 40Ar/39Ar dating may indicate the occurrence of more than one mineralising event. Consideration of this diversity from a mineral systems perspective, highlights the likelihood that undiscovered gold deposits in the Tanami region will have a range of characteristics and may occur in a number of different lithologies.

  • An interpretation of the Paterson area has been carried out to understand the distribution of Proterozoic bedrock beneath thin (<300 m) Phanerozoic cover. Numerous granitic intrusions have been identified to the north of Telfer, which intrude a pre-deformed Neoproterozoic sequence, suggesting that this shallowly covered area is prospective for granite-related Au-Cu mineralisation. Neoproterozoic sedimentary rocks in the south of the area previously interpreted to be part of the Tarcunyah Group might instead be part of the Yeneena Basin. The absence of Neoproterozoic granites in this part of the area means that these rocks have a low potential for Au-Cu mineralisation, but have a relatively high potential for base metal and unconformity-style uranium mineralisation. Depth to Proterozoic basement modelling has also been carried out for the area, effectively mapping the depth of the surface represented by the solid geology interpretation. This has shown that much of the area has only a relatively thin cover (typically less than 300 m), making it accessible for exploration. In contrast, the Phanerozoic Waukarlycarly Embayment in the northwest of the area contains a relatively thick succession (with maximum depths exceeding 3000 m) within a NNW-trending, steep-sided graben that is 30-40 km wide.

  • This project was set up to demonstrate how geochemistry is able add-value to exploration. The project has produced improved total system ore genesis models, a comprehensive up-to-date database and associated software tools for hydrothermal geochemistry modelling.

  • Western Victoria is host to several world class sediment-hosted gold deposits (e.g. Stawell, Ballarat, Bendigo) that have been studied on an individual basis, generally without reference to a well-constrained regional structural and stratigraphic framework. The configuration and availability of fluid conduits (shear zones or other structural settings and appropriate host lithologies) over time is clearly an important factor in the formation of these mineral deposits but the distribution and profiles of fluid pathways with increasing crustal depth are often imprecisely known. It is also probable that the mineralising fluids were not locally sourced, but travelled long distances from their point of origin, making it imperative that all potential fluid conduits be mapped in 3D so that any sub-surface linkages or networks of fluid pathways be identified. These pathways then need to be incorporated into the 3D regional framework so that the key conduits and structures can be further investigated to establish their precise role in either controlling or sustaining fluid flow over geological time scales appropriate for the formation of a major ore-body. The Stawell Zone in western Victoria is ideally placed for such a case study because it contains sequences that relate to the mineralisation types found in Tasmania and those identified in central Victoria and NSW.

  • Detailed analysis and modeling of regional gravity and magnetic datasets from the Stuart Shelf around the Olympic Dam iron oxide-copper-gold (IOCG) deposit, constrained by geological observations from deep drillcores, show that the eastern Gawler Craton at 1.61-1.59 Ga consisted of an Archean core with two volumes of supracrustal successions stepping out eastward from it. This pattern is consistent with that displayed on the Eyre Peninsula. Detailed models of potential-field data show no evidence for the presence of widespread mafic rocks or extensional basin systems developed immediately prior to, or during, IOCG mineralization. The high intrusive level, and geometry of Hiltaba Suite plutons emplaced immediately prior to IOCG mineralization is difficult to explain in terms of a genetic association with mantle plumes, continental extension, or rifting. Instead, the tectonic setting inferred from the basement architecture during mineralization is one of low-strain compression, based on geometric considerations. A case can be made for mild extension in a localized accommodation zone during emplacement of the Hiltaba Suite and Gawler Range Volcanics, in an overall orogenic setting with northwest-southeast directed tectonic transport in present coordinates. An IOCG minerals system produced during low-strain compression is consistent with maximum rates and volumes of fluid flow in the upper crust, and access of these fluids to a variety of basement rock types to buffer metal-scavenging fluids. This fluid-driving mechanism does not require, or implicate, a genetic role for regional mafic magmatism and volcanism synchronous with IOCG mineralization. The approach used in this study is generally applicable to exploration for IOCG systems, and other mineral systems in covered terranes that have distinctive geophysical signatures resulting from redox fluid-wallrock geochemical reactions.

  • Abstracts and proceedings from the Kalgoorlie 2007 conference (24-27 September 2007).

  • The Tanami region has become one of Australia?s premier Proterozoic gold provinces, having already produced 4.85 Moz (150 t) of gold, and still has high exploration potential. This region contains more than 60 gold occurrences including three established gold fields (Dead Bullock Soak, The Granites and Tanami) as well as several significant gold prospects (Groundrush, Titania, Crusade, Coyote and Kookaburra). The Callie deposit (>4.5 Moz total resource) located in the Dead Bullock Soak goldfield is currently the largest mine in this region. The fluid inclusion data suggests that the deposits have formed over a range of physico-chemical conditions and depths. Groundrush appears to have formed at the greatest depths and has the most reduced (CH4-rich) fluids. The Granites goldfield and the Coyote and Callie deposits formed at shallower depths. The Coyote deposit contained both CO2-rich and CH4-rich fluid inclusions. Fluids at The Granites were CO2-rich but also had variable N2 and CH4. Fluids at Callie are relatively more oxidised with only CO2 and N2 being detected. The Tanami deposits appear to have formed at the shallowest levels and are dominated by low-salinity aqueous fluid inclusions, although some CO2-bearing fluid inclusions have also been detected. Thus, it appears that the ore-bearing fluids in the Tanami region attained temperatures between 120 and 430 ?C and contained variable quantities of CO2 ? other gases which may have formed as a result of fluid/rock interaction. Homogenisation data indicate that the Groundrush and Coyote deposits had the highest temperature fluids (260 ? 430 ?C), while the ore fluids in the Dead Bullock Soak and The Granites goldfields were moderate to high temperature (220 ? 326 ?C). In contrast, the Tanami goldfield, is dominated by low temperature (120 ? 220 ?C) aqueous inclusions. O and H isotopic data are consistent with either a metamorphic or magmatic origin for the ore fluids with some mixing with meteoric fluids evident in the Tanami district. In an effort to evaluate the regional extent of this gold-only mineral system we have carried out re-gional sampling of outcropping quartz veins and extended our fluid inclusion and Ar/Ar studies into the north Arunta region. More than 100 quartz vein clusters located in regions with differing metamorphic grade, were selected for sampling on twelve 1:250K mapsheets. The following types of veining have been observed: ? Epithermal veins with a range of textures including chalcedonic, colloform and comb quartz. ? Mesothermal veins striking mainly E-W. These veins are highly prospective as they are of a similar age to those in the gold deposits and have fluid chemistries similar to the ore-bearing fluids. ? Quartz veins with saccharoidal textures that contain two fluids: a higher temperature (230 ? 330 ?C), gas-rich fluid and a lower temperature (120 ? 230 ?C), saline, aqueous fluid. Acknowledgements This work forms part of the North Australia Project, a collaborative project between Geoscience Australia and the Northern Territory Geological Survey. TPM, GLF, and DLH publish with permission from the CEO of Geoscience Australia.