Examination of copper, nickel, lead and zinc (base metals) exploration expenditure and discovery in Australia over the period 1976-2005 reveals some significant trends. Australia's base metal resource inventory grew substantially as a consequence of successful exploration over the period, both through addition of resources at known deposits and new discoveries, notably a small number of very large deposits that underpin the resource base. In 2005, Australia had the world's largest economic demonstrated resources (EDR) of nickel, lead and zinc, and the second largest EDR of copper. Growth in nickel resources has been especially strong owing to discovery of large laterite resources in the late 1990s. Resource life, in average terms based on current EDR and production, is approximately 30 years for lead and zinc, 40 years for nickel sulphide (120 years for all nickel EDR) and 50 years for copper. Despite this success, major increases in production over the period (copper, nickel and zinc output increasing 3-4 fold, lead output doubling) and a fall in discovery rates during much of the 1990s means that resource life for lead and zinc is lower and nickel sulphide comparable now to that in 1976; only the resource life of copper has grown substantially over the period. Current published ore reserves are sufficient for at least 15 years operations at current production levels, but only a small number of the largest deposits currently being mined are likely to still be in production in 20 years. However, several mines have substantial inferred resources that may allow production beyond current mine reserves and there is a substantial number of undeveloped deposits that may provide the foundation for extended or new mining operations. The discovery record is strongly cyclical with resource growth for all the base metals punctuated by the discovery of giant (world-class) deposits each decade: these underpin current and future production. Recent higher metal prices and renewed interest in base metals, especially nickel, has reversed a 10 year decline in base metal exploration attended by reduced rates of discovery and resulted in record expenditure, new nickel, copper and zinc discoveries, and increased resources at a number of existing deposits, notably the Olympic Dam copper-uranium-gold deposit. With the exception of the Prominent Hill copper-gold and West Musgrave nickel-copper deposits, most of the recent discoveries, especially zinc (-lead) deposits, are of small tonnage (some of high grade). Nevertheless, these new discoveries have helped stimulate further exploration and also highlight the potential for further discoveries in little-explored provinces, especially those under regolith and shallow sedimentary cover.

Australia's east coast north of Bass Strait has been very sparsely explored for petroleum. Exploration permits have been intermittently held over the offshore Sydney Basin, including an active permit at the time of writing, and some permits were held in north Queensland waters in the 1960s and 1970s, but much of the geology of this eastern continental margin is virtually unknown. This report provides a preliminary assessment of the petroleum potential of Australia's east coast, from the border between New South Wales and Victoria in the south, to the southern boundary of the Great Barrier Reef Marine Park (GBRMP) offshore southeast Queensland in the north. Petroleum exploration is prohibited within the GBRMP, and no assessment of this area is included in the report. Palaeozoic basement rocks covered by a veneer of Cainozoic sediments underlie a large part of the study area (Figure 1). At least four sedimentary basins also underlie the continental shelf and probably the continental slope in the case of the Sydney and Maryborough Basins. These two basins are also the best known; but the Clarence-Moreton and Nambour Basins are also known to have offshore extensions on the shelf. It is also possible but not certain that the Ipswich and Lorne Basins could have offshore components, and there is some evidence of a pre-Clarence-Moreton Basin sedimentary sequence offshore of the Coffs Harbour area. In addition to these basins, several graben and half-graben associated with Tasman Sea rifting may occur within basement dominated shelf and slope areas - two of these features are known from very limited data.

Geoscience Australia Marine Survey 267 was undertaken aboard the Parmelia K, a 28 m pearling boat out of Broome. The survey departed Darwin on 3 March 2004 and terminated in Broome on 18 March 2004. The length of the survey was curtailed by unfavourable weather conditions associated with tropical cyclones Evan and Fay. The aim of the survey was to test and validate a range of techniques used in the detection/identification of natural hydrocarbon seepage. The Yampi Shelf in the northern North West Shelf was selected for the test bed as it is a known region of intense and widespread hydrocarbon seepage. One of the most significant findings of the survey was the direct observation of natural hydrocarbon seepage in the Timor Sea region of the North West Shelf, which has previously only been interpreted through remote sensing or automated water sampling techniques (sniffer). Seepage plumes were observed rising from pockmark fields or hard-grounds on the vessel's echosounder and the side-scan sonar. Gas bubbles with oily films were observed at the surface. Active seepage sites were detected in close associated with hydrocarbon related diagenetic zones (HRDZs) interpreted in 3D seismic coverage of the region. A towed fluorometer detected variations in the hydrocarbon concentration of the sea surface over the study areas. Seepage appeared to be most active in association with low-tide, and more suppressed during high tide. Multi-beam swath bathymetry of the study areas revealed channels between 2 and 20 m deep on the Yampi Shelf headland and in the vicinity of the major HRDZs. Tidal current directions measured by an acoustic doppler current profiler (ADCP) in the Yampi Shelf headland channels suggests that tidal shears over this headland may be giving a response on Synthetic Aperture Radar (SAR). Sediment samples were collected with a Smith-Macintyre Grab, a dredge and a gravity core, although coring was largely unsuccessful due to carbonate hard-grounds over the seepage sites. Grab and dredge samples suggest that the active seeps are zones of preferential macro-biotic distribution. Significant down-time was introduced through poorly functioning equipment and a lack of experience on behalf of the staff. This was primarily due to the fact that some of the equipment was leased from Seismic Asia Pacific Ltd. Therefore it is recommended for future surveys that an operator be supplied with leased equipment, or that the equipment is purchased by Geoscience Australia and staff are appropriately trained before the survey. It is also highly recommended that the survey have seismic acquisition capability, as the seismic data proved to be the best proxy for seepage site location.

This report contains the preliminary results of Geoscience Australia survey 266 to central Torres Strait. The survey was undertaken to investigate the seabed geomorphology and sedimentary processes in the vicinity of Turnagain Island and to infer the possible effects (if any) on the distribution, abundance and survival of seagrasses. The Turnagain Island region was chosen because it is a known site of recent widespread seagrass dieback. The present survey is the first of two by Geoscience Australia to be carried out in 2004 and is part of a larger field-based program managed by the Reef CRC aimed at identifying and quantifying the principal physical and biological processes operating in Torres Strait. The impetus for the program is the threat of widespread seagrass dieback and its effects on local dugong and turtle populations and the implications for indigenous islander communities.

During 2003 Geoscience Australia operated geomagnetic observatories at Kakadu and Alice Springs in the Northern Territory, Charters Towers in Queensland, Learmonth and Gnangara in Western Australia, Canberra in the Australian Capital Territory, Macquarie Island, Tasmania, in the sub-Antarctic, and Casey and Mawson in the Australian Antarctic Territory. This report describes instrumentation and activities, and presents monthly and annual mean magnetic values, plots of hourly mean magnetic values and K indices at the magnetic observatories and repeat stations operated by Geoscience Australia during calendar year 2003.

The disappearance of iron formations from the geological record ~1.8 billion years (Gyr) ago was the consequence of rising oxygen levels in the atmosphere starting 2.45-2.32 Gyr ago. It marks the end of a 2.5-Gyr period dominated by anoxic and iron-rich deep oceans. However, despite rising oxygen levels and a concomitant increase in marine sulphate concentration, related to enhanced sulphide oxidation during continental weathering, the chemistry of the oceans in the following mid-Proterozoic interval (1.8-0.8 Gyr ago) probably did not yet resemble our oxygen-rich modern oceans. Recent data indicate that marine oxygen and sulphate concentrations may have remained well below current levels during this period, with one model indicating that anoxic and sulphidic marine basins were widespread, and perhaps even globally distributed4. Here we present hydrocarbon biomarkers (molecular fossils) from a 1.64-Gyr-old basin in northern Australia, revealing the ecological structure of mid-Proterozoic marine communities. The biomarkers signify a marine basin with anoxic, sulphidic, sulphate-poor and permanently stratified deep waters, hostile to eukaryotic algae. Phototrophic purple sulphur bacteria (Chromatiaceae) were detected in the geological record based on the new carotenoid biomarker okenane, and they seem to have co-existed with communities of green sulphur bacteria (Chlorobiaceae). Collectively, the biomarkers support mounting evidence for a long-lasting Proterozoic world in which oxygen levels remained well below modern levels.

Product no longer exists, please refer to GeoCat #30413 for the data

Product no longer exists, please refer to GeoCat #30413 for the data

Product no longer exists, please refer to GeoCat #30413 for the data

Product no longer exists, please refer to GeoCat #30413 for the data