Abstract for initial submission, pending acceptance by convention technical program committee.

The paper discusses the results from the GA-302 2D seismic survey and GA-2436 (RV Tangaroa) marine reconnaissance survey over the Capel and Faust basins, northern Tasman Sea. The integration of seismic, potential field and bathymetric data sets in 3D space at an early stage in the project workflow has assisted in the visualisation of the basin architecture, the interpolation of data between the seismic lines, and the iterative refinement of interpretations. The data sets confirm the presence of multiple depocentres, as previously interpreted from satellite gravity data, with a maximum sediment thickness of 5-7 km. Preliminary interpretation of the seismic data has identified two predominantly Cretaceous syn-rift and two Upper Cretaceous to Neogene sag megasequences overlying a heterogeneous pre-rift basement. The comparison of seismic facies and tectonostratigraphic history with offshore New Zealand and eastern Australian basins suggests the presence of possible Jurassic to Upper Cretaceous coaly and lacustrine source rocks in the pre- and syn-rift, and fluvio-deltaic to shallow marine reservoir rocks in the syn-rift to early post-rift successions. Preliminary 1D basin modelling suggests that the deeper depocentres of the Capel and Faust basins are within the oil and gas windows. Large potential stratigraphic and structural traps are also present.

Tholeiitic intrusion-hosted nickel sulphide deposits are highly sort exploration targets due to their potential size and co-products platinum-group elements and copper. The Norilsk-Talnakh (Russia), Voisey's Bay (Canada) and Jinchuan (China) deposits are world class examples. Although Australia holds the largest economic resources of nickel in the world, its nickel resources are mainly sourced from komatiitic-hosted and lateritic deposits. Known resources of tholeiitic intrusion-hosted nickel sulphides are relatively small, with Nebo-Babel and Nova-Bollinger in Western Australia the most significant examples. Given the abundance of tholeiitic igneous rocks in Australia, this important deposit type seems to be under-represented when compared to other continents with similar geology. To support the discovery of world class nickel sulphide deposits in Australia, Geoscience Australia has recently undertaken a continental-scale GIS-based prospectivity analysis for tholeiitic intrusion-hosted deposits across Australia. This analysis exploits a suite of new relevant digital datasets recently released by Geoscience Australia. For example, the analysis utilises the Australian Mafic-Ultramafic Magmatic Events GIS Dataset which places mafic and ultramafic rocks across Australia into 74 coeval magmatic events based on geochronological data. Whole rock geochemistry of mafic and ultramafic rocks has been used to differentiate between magma series and discriminate between different magmatic events and units within those events. Other new datasets include crustal domain boundaries derived from both deep crustal seismic data and neodymium depleted mantle model age data as well as a coverage of the minimum thickness of mafic rocks in the crust derived from the Australian Seismogenic Reference Earth Model. This continental-scale GIS-based nickel sulphide prospectivity analysis uses a mineral systems approach to map the four essential components of ore-forming mineral systems; (1) sources of ore constituents, (2) crustal and mantle lithospheric architecture, (3) energy sources or drivers of the ore-forming system, and (4) gradients in ore depositional physico-chemical parameters. These four components are combined into a prospectivity map using weights-of-evidence GIS-based techniques, with the most prospective areas across the continent occurring where all components are present. The mineral systems approach allows for the identification of a much larger footprint than the deposit itself, and can be applied to greenfield and/or undercover areas. The results highlight areas that contain known tholeiitic intrusion-hosted nickel sulphide deposits, such as the Musgrave and Pilbara Provinces, as well as regions that do not contain any known deposits, such as the southern margin of the Arunta Province in the Northern Territory, the Mount Isa Province in Queensland and the Paterson Province in Western Australia.

At Whites Deposit, Rum Jungle, chalcopyrite-uraninite ore has been intersected in a cross-cut at a depth of 100 ft., and sampling shows a grade of 1.5 per cent. U3O8 and 4.6 per cent. Cu. over a distance along the cross-cut of 34ft; material containing an average of 0.94 per cent. U3O8 and 2.97 per cent. Cu extends over 60 ft. Uranium mineralization is known to occur over a length of 200 ft, but the average width and grade over this distance is unknown. The ore replaces flatly pitching drag-folded beds and the width of ore along the strike is expected to vary considerably. At Dysons Prospect, about 30,000 tons of autunite-bearing ore, perhaps containing 0.25 per cent. U3O8, has been indicated by drilling. Browns Prospect is similar in many ways to Whites, but no payable ore has yet been intersected. In the district as a whole leaching of copper and uranium has been extensive and favourable areas are, in many cases, covered by soil. Structural conditions are such that non-outcropping ore is likely to be found. To-date, 3,300 ft. of drilling and approximately 700 ft. of underground prospecting have been carried out in the area and the results obtained are considered highly encouraging. Extensive drilling and underground development are warranted.

Abstract for initial submission; see Geocat 71429 for conference paper version

Uranium-rich igneous rocks are recognised as an important source of metals in uranium mineral systems. Magmatic-related uranium mineralisation may be orthomagmatic in origin, forming via favourable igneous processes, or may result from the exsolution of uranium-rich fluids from particular magmas. Additionally, it is recognised that igneous rocks also may contribute directly to basin-related uranium mineral systems as a metal source. Thus, mapping of the distribution of uranium in igneous rocks has the potential to highlight prospective regions for uranium mineralisation at a macro-scale. Geoscience Australia has produced a series of three digital maps showing the uranium content of igneous rocks across Australia, drawing together geochemical and geological datasets from disparate open file sources. Map 1 shows the uranium concentration in whole rock geochemical analyses plotted as point data on a background of igneous rock type, which itself is derived from Geoscience Australia's 1:1 000 000 national surface geology map. Map 2 integrates these datasets, and shows the average uranium content of all intersecting geochemical data point for outcropping individual igneous rock units. In Map 3, a similar approach is employed in mapping the average uranium content of igneous rocks occurring under cover, using interpreted solid geology coverages. Combined, these maps provide a comprehensive picture of the province-scale trends in igneous uranium content across the continent. Using an applied knowledge of processes leading to uranium concentration in magmatic systems, igneous rocks exhibiting a favourable combination of factors are able to be identified for further analysis of prospectivity for uranium mineral systems.

Uranium deposits are generally classified into types based on host rock, orebody morphology or structural setting. Widely used schemes contain 14 or more deposit types and numerous sub-types. However, groups of deposit types were formed by similar geological and geochemical processes and likely represent 'variations on a theme'. An alternative scheme is presented that recognises the continuum of possible uranium deposit styles between three families of mineral systems: magmatic-related, 'metamorphic'-related, and basin-related. Formation of uranium deposits in each family involves fluids of three end-member type: magmatic-hydrothermal, 'metamorphic' (including diagenetic waters and fluids reacted with metamorphic rocks at elevated temperatures), and surface-derived fluids such as meteoric waters, seawater, lakewater and groundwater. By better understanding the fundamental geological and geochemical processes involved in ore formation in each family of uranium mineral systems, the most important geological 'symptoms' can be recognised and mapped. This mineral systems approach has been applied to magmatic-related uranium systems in Australia. The predictions of potential suggest that the under-representation of magmatic-related uranium resources relative to other parts of the world with similar geology may be due not to low endowment but to lack of discovery.

The areas included in the geophysical survey, namely the Laloki, Moresby-King and Dubuna leases, are among those held by Mandated Alluvials N.L., and lie in the Astrolabe Mineral Field. The positions of the leases held by the Company are shown in Plate G73-1. Laloki, the main producer of copper, is situated 20 miles by road from Port Moresby, near the junction of Sapphire Creek with the Laloki River. The Bureau was requested by Mandated Alluvials to carry out a geophysical survey in the vicinity of the known deposits and in adjacent areas. Both Laloki and Moresby-King mines has been in production up to the time when the war in New Guinea caused a suspension of operations. During the war the mine workings and much of the plant were completely destroyed. When consideration was given to the best method of reopening the mines it was decided that, if a large enough tonnage or ore could be proved sufficiently close to the surface, it would be most profitable to continue open-cut mining, and possibly install a flotation concentrator to avoid the troubles that had always accompanied smelting. The aim of the geophysical survey was, therefore, to locate a body of ore large enough to justify the adoption of these mining and treatment methods.

Sediments of the Brock's Creek Group and of the Phillips Creek Formation, and volcanics of the Edith River Formation were prospected with carborne radiometric equipment. A comparatively high background count was recorded in the Edith River Volcanics, but no significant radiometric anomaly was found. A geological party prospected ten shear zones south east of the Edith Siding, including a cupriferous one, and a strongly fractured belt near the granite contact. No radiometric anomaly was found. Future prospecting should be directed towards major faults within the sediments.

The airborne scintillometer survey made in the latter half of 1952 revealed a number of anomalies in the Brodribb area. Detailed geological and geophysical work was carried out on this prospect during 1952 (Frankovich 1953) and some costeans were excavated by bulldozer. In 1953 diamond drilling and further geological and geophysical work was undertaken. During 1953, six diamond drill holes, with a total footage of 1583 feet, were drilled in the Brodribb area and were arranged to make an exhaustive test for the occurrence of a primary uranium deposit of importance in the area.