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  • This map shows the boundary of the exploration lease 1348 at Kodu in Papua New Guinea as well as the location of the Kododa Trail.

  • An overview of mineral exploration within Australia for the year 2000.

  • The Gawler Craton has been defined as that region of South Australia where Archaean to Mesoproterozoic crystalline basement has undergone no substantial deformation (except minor brittle faulting) since 1450 Ma (Figure 1; Thomson, 1975; Parker, 1993; Daly et al, 1998). The eastern and southeastern boundaries conventionally are defined by the Torrens Hinge Zone (THZ), although Gawler Craton basement that was deformed during the Delamerian Orogeny is known to the east of the THZ (eg Barossa Complex, Peake and Denison Inliers). The southern boundary corresponds to the inboard edge of the continental shelf. The Gawler Craton and the East Antarctic Craton are rifted segments of the Mawson Continent (Fanning et al, 1995). Western, northwestern and northern boundaries of the Gawler Craton are defined by the faulted margins of thick Neoproterozoic and younger basins. As a consequence of the extensive surficial and sedimentary basin cover, the level of understanding of the craton's geology and prospectivity are limited in comparison with most other Australian Archaean and Proterozoic cratons. Application of high-resolution regional aeromagnetic surveying during the mid-1990s (South Australian Exploration Initiative - SAEI), for the first time allowed an integrated interpretation and synthesis of the geology of the craton (Fairclough and Daly, 1995a; Fairclough and Daly, 1995b; Schwarz, 1996). A revised interpretation of the tectonic evolution of the Gawler Craton incorporating SHRIMP U-Pb geochronology, was presented by Daly et al (1998). Three principal orogenies have been proposed: The Sleafordian Orogeny (peak metamorphism at ~2420-2440 Ma), the Kimban Orogeny (KD1-KD2-KD3: 1845-1700 Ma), and the Kararan Orogeny (~1650 Ma and 1565-1540 Ma). It has been suggested that the Kararan Orogeny in the western and northern Gawler Craton represents the continental collision of the 'eastern proto-Yilgarn' and the Mawson Continent (Daly et al, 1998). The geodynamic significance of the Sleafordian and Kimban Orogenies is unclear. Subdivision of the Gawler Craton into tectonic domains has evolved as further information has become available (Figure 1; eg Parker, 1993; Flint and Parker, 1982; Drexel et al, 1993; Teasdale, 1997). In general the definition and nature of the domain boundaries are not well understood - addressing this problem is a key objective of the Gawler Craton Project. The resultant framework will be important for assessing prospectivity because the ore-forming systems are products of crustal-scale processes that may vary between tectonic domains. The contents of this GA Record were written in 2000, and were presented on the Gawler Project website prior to the publication of this GA Record.

  • Ore deposits are the focus of large-scale energy and mass flux systems. Regions of special endowment, such as Australia's premier gold and nickel province in the Archaean Yilgarn Craton, preserve large-scale signatures in the crust and mantle that reflect the processes of their formation. Integration of geology with datasets such as broad-band tomographic images of the lithosphere, receiver function velocity profiles of the crust, seismic reflection deduced crustal architectures, together with geochemical and geochronological datasets, provide insights to the processes of ore formation at the largest scales. Consideration at the largest scales ensures quick and effective area selection.

  • Two day Y4 team targeting exercise at Gold Fields St Ives mine site (September 2007)

  • Most current classification schemes for uranium deposits emphasise differences in host rock type, resulting in a plethora of apparently separate deposit styles. While this scheme has been useful in categorising uranium resource data, it has limitations when assessing greenfields regions for undiscovered or unrecognised styles of uranium deposits. We propose an alternative scheme that describes a continuum of possible deposit styles. It is based on the fundamental properties of uranium and its physico-chemical behaviour during earth processes. Three end-member fluid types are typically responsible for the transport and deposition of U6+ and U4+: magmatic-hydrothermal, "metamorphic" (including fluids reacted extensively with meta-morphic rocks), and hydrosphere-derived. The end-member fluids are principal components in three uranium mineralising systems: magmatic-, meta-morphic-, and sedimentary basin-related. Each system contains a range of deposit styles, reflecting the continuum in properties between end-member fluid types as well as differing geological settings. Magmatic-related uranium systems encom-pass a range of deposit styles from "orthomagmatic" to hybrid styles dominated by magmatic-hydro-thermal fluids but with contributions of hydro-sphere-derived or metamorphic fluids. Uranium-rich iron oxide Cu-Au deposits form by the action of hydrosphere-derived fluids either mixing with hybrid magmatic-metamorphic fluids or overprinting the oxides and sulfides. "Metasomatic" deposits probably derive from a range of magmatic-hydrothermal to metamorphic fluids. Sedimentary basin-related uranium systems contain a suite of deposit styles that share several fundamental characteristics and processes. One end-member fluid is oxidised water from the hydrosphere. Reaction with basin and/or basement rocks with leachable uranium may result in U-rich groundwaters, formation waters and connate brines. End-member metamorphic (including diagenetic) fluids may mix with these waters. Uranium is deposited via fluid-rock or fluid-fluid reactions predominantly involving reduction or evaporation. We support the growing recognition that "sandstone-hosted", "unconformity-related" and "Westmoreland" type deposits are members of a continuum of styles within basin-related systems. Hybrid deposit styles are a predicted consequence of the proposed scheme.

  • The extended abstract describes the geophysical characteristics of the granite dominated geophysical map units of the Yilgarn Craton and the relationship between their deformation and gold mineralisation. Aeromagnetic data are not able to distinguish the five main granite geochemical groups. Gamma-ray spectromatric data provide some distinctin of the geochemical groups but their use is restricted to limited areas of outcrop. Faults host much gold but the majority of these structures are barren and spatial associations have been difficult to establish. Shear zones are irregularly distributed across the craton. Abundant intersecting shear zones, that transect both granite and greenstone, define a 200 km wide, north-trending corridor, with distinctive rhomboid to sigmoidal internal geometry. Greenstones in the corridor are extensively disrupded and strongly aligned with adjacent shear zones. This corridor correlates with the the region of highest gold endowment for the Yilgarn Craton and large deposits are spatially associated with bends and intersections of the shear zones. By contrast, shear zones are sparse in the Yalgoo Dome area in the north west of the Yilgarn Craton. The crustal architecture of this area is dominated by large ovoid bodies of granite. Adjacent greesntones are not regionally alligned, nor particularly disrupted internally, and gold endowment is low. These aparent contrasting structural styles and corresponding differences in gold endowment can be similarly applied to the Superior Province of Canada (Abatibi Belt, abundant intersecting shear zones, strongly aligned greenstone, and high gold endowment) and Australia's Pilbara Craton (few shear zones, oviod granite geometry dominant with little regional alignment of greenstone and low gold endowment).

  • The supergiant Pb-Zn-Ag Broken Hill orebody and numerous other minor mineral deposits occur within the limited outcrop of the Proterozoic Curnamona Province of Australia. The vast majority of this Province is concealed by up to 200 m of transported regolith, hampering conventional exploration strategies. Approximately 300 groundwater samples were collected over the southern Curnamona Province to test whether this medium could be helpful in the search for hidden mineral deposits. Sulphur, Sr and Pb isotope composition of the groundwaters were determined and S excess (SXS ), i.e., the amount of S that can be ascribed neither to evaporation nor to mixing,was calculated. Many samples were recognised to have undergone an addition of 34S-depleted S, which can be attributed to oxidation of sulfdes with a Broken Hill type d34S signature (average 0 permil V-CDT). Furthermore, Sr isotopes identify the broad types of bedrock that the groundwater has been interacting with, from the less radiogenic Adelaidean rocks (and minerals)in the west (groundwater 87Sr/86Sr ratio as low as 0.708) to the highly radiogenic Willyama Supergroup in the east (87Sr/86Sr ratio up to 0.737). The groundwaters have 207Pb/204Pb and 206Pb/204Pb ratios comparable to, or intermediate between,various mineralisation types recognised in the area (Broken Hill, Rupee, Thackaringa, etc., types). The few samples taken in the vicinity of known mineralisation yield positive indicators (positive SXS ,low d34S, 87Sr/86Sr signature of bedrock type and Pb isotope fingerprinting of mineralisation type). This study also highlights several new locations under sedimentary cover where these indicators suggest interaction with mineralisation.

  • Geoscience Australia conducted the Yilgarn-Officer-Musgrave 2D Seismic Survey. The survey involves the acquisition of seismic reflection over the Yilgarn Craton, Officer Basin and Musgrave Province of Western Australia. The survey consisted of one line, totalling 484.2 kms. The project is a collaborative project between Geoscience Australia and the Geological Survey of Western Australia and is part of the ongoing cooperation under the National Geoscience Agreement (NGA). Funding of this project is through the Western Australian Government's Royalties for Regions Exploration Incentive Scheme and Geoscience Australia's Onshore Energy Security Program. The primary objective of the project is to image the western Officer Basin, one of the Australia's underexplored sedimentary basins. In addition this survey will gather new data to improve the understanding of the Yilgarn Craton and its boundary with the Musgrave Province. Raw data for this survey are available on request from clientservices@ga.gov.au

  • This CD contains PDF files of selected presentations for the Minerals Division's Open Day Seminar in Perth, November 2004.