Geoscience Australia (GA) has implemented an Onshore Energy Security Program (OESP) to identify Australia's onshore energy resources. The objectives of the OESP are to provide essential pre-competitive geoscientific data to lower exploration risk and stimulate investment in exploration for Australia's uranium, thorium, geothermal and onshore petroleum resources. The program is funded under a new Energy Security Initiative announced by the Australian Government in August 2006. As a key component of the OESP GA will be conducting geophysical surveys across Australia for the next four years collecting the following data: deep seismic reflection, magnetotelluric, airborne magnetic, radiometric, electromagnetic and ground based gravity. The demand for resources, and increased funding by the Commonwealth, States and NT, have been the driving factors in the recent improvement in the regional geophysical coverage of Australia.

Airborne Electromagnetic data are being acquired by Geoscience Australia (GA) under the Australian Government's Onshore Energy Security Program (OESP) in areas considered to have potential for uranium or thorium mineralisation. The surveys have been managed and interpreted by GA's Airborne Electromagnetic Acquisition and Interpretation project. In contrast to deposit scale investigations, conducted by industry, these surveys are designed to reveal new geological information at a regional scale. The Pine Creek airborne electromagnetic survey show in Figure 1 is comprised of three survey areas; Woolner Granite, Rum Jungle and Kombolgie. TEMPESTTM data were acquired for the Woolner Granite and Rum Jungle surveys and VTEMTM data were acquired for the Kombolgie survey. The Kombolgie survey, in the Pine Creek Orogen of the Northern Territory, covered sections of the Alligator River, Cobourg Peninsula, Junction Bay, Katherine, Milingimbi and Mount Evelyn, 1:250 000 map sheets (Costelloe et al., 2009). A total of 8 800 line km of VTEMTM data were acquired in 2008, covering an area of 32 000 km2. In 2009 the processed response data and EM FlowTM commercial version 3.30 (Macnae et al., 1998, Stolz and Macnae 1998) conductivity estimates to 600 m depth, produced by the survey contractor Geotech Airborne, were made available to the public in the GA Phase-1 data release. In this article we discuss an enhanced set of conductivity estimates, which are now available from the GA website free of charge. These new conductivity estimates, reveal new geological information to depths approaching 2 km in the more resistive portion of the survey area. They were generated by GA using the most recent version (5.23-13) of EM FlowTM.

This report summarises the result of a study into seawater intrusion into coastal aquifers in the Northern territory coastal plain using AEM data, down hole geophysics, and bore hole geology carried out by Geoscience Australia on behalf of the National Water Commission and in partnership with NRETAS. The study showed that ground-validated AEM is able to map areas of saline aquifers in the area and differentiate them from bedrock conductors.

The Gilmore Project is a pilot study designed to test holistic systems approaches to mapping mineral systems and dryland salinity in areas of complex regolith cover. The project is coordinated by the Australian Geological Survey Organisation, and involves over 50 scientists from 14 research organisations. Research partners include: Cooperative Research Centres for Advanced Mineral Exploration Technologies (CRC AMET), Landscape Evolution and Mineral Exploration (CRC LEME), the CRC for Sensor Signal and Information Processing, and the Australian Geodynamics Cooperative Research Centre (AGCRC) Land & Water Sciences Division of Bureau of Rural Sciences (BRS) NSW Department of Land & Water Conservation and the NSW Department of Mineral Resources. Various universities including the Australian National University, University of Canberra, Macquarie University, Monash University, University of Melbourne, and Curtin University of Technology, and Australian National Seismic Imaging Resource (ANSIR). The project area lies on the eastern margin of the Murray-Darling Basin in central-west NSW. The project area was chosen for its overlapping mineral exploration (Au-Cu) and salinity management issues, and the availability of high-resolution geophysical datasets and drillhole materials and datasets made available by the minerals exploration industry. The project has research agreements with the minerals exploration industry, and is collaborating with rural land-management groups, and the Grains Research and Development Corporation. The study area (100 x 150 km), straddles the Gilmore Fault Zone, a major NNW-trending crustal structure that separates the Wagga-Omeo and the Junee-Narromine Volcanic Belts in the Lachlan Fold Belt. The project area includes tributaries of the Lachlan and the Murrumbidgee Rivers, considered to be two of the systems most at risk from rising salinities. This project area was chosen to compare and contrast salt stores and delivery systems in floodplain (in the Lachlan catchment) and incised undulating hill landscapes (Murrumbidgee catchment). The study area is characteristic of other undulating hill landscapes on the basin margins, areas within the main and tributary river valleys, and the footslopes and floodplains of the Murray-Darling Basin itself. Studies of the bedrock geology in the study area reveal a complex architecture. The Gilmore Fault Zone consist of a series of subparallel, west-dipping thrust faults, that juxtapose, from west to east, Cambro-Ordovician meta-sediments and granites of the Wagga Metamorphics, and further to the east, a series of fault-bounded packages comprising volcanics and intrusions, and siliciclastic meta-sediments. Two airborne electromagnetic (AEM) surveys were flown in smaller areas within the two catchments. Large-scale hydrothermal alteration and structural overprinting, particularly in the volcanics, has added to the complexity within the bedrock architecture.

In 2008-2009 Geoscience Australia, contracted Fugro Airborne Surveys and Geotech Airborne, to respectively acquire TEMPEST and VTEM airborne electromagnetic (AEM) data with broad line spacings covering more than 71 000 km² in the Pine Creek region, Northern Territory. The Pine Creek survey (Figure 1) is the second regional AEM survey funded by the Onshore Energy Security Program (OESP) at Geoscience Australia. Geoscience Australia funded the flying of 19 500 line km, subscriber companies funded 10 400 line km. The 5 000 m line spacing provide regional information with 1 666 m, 555 m and closer line spacing providing detail for mineral systems analysis and deposit scale mapping. One of the main survey objectives was to reduce exploration risk and encourage exploration in the region by mapping, under cover, in areas where gravity and magnetics are quiet. Geological targets included detecting: conductive unites within the Pine Creek Orogen (PCO) sequence; Kombolgie Sandstone / PCO unconformity; Tolmer Group/ Finniss River Group unconformity. Geoscience Australia undertook conductivity logging (Figure 2) in the Pine Creek region. Conductivity logs were processed and as input into forward models, ground truth AEM results and for geological interpretations. To facilitate interpretation, subsurface electrical conductivity predictions using a layered earth inversion (sample by sample) algorithm developed by Geoscience Australia (GA-LEI) were derived from the AEM survey data. Conductivity characterisation of large regional units using the AEM data show: the Rum Jungle Complex is a consistently resistive area with an average conductivity value of less than 2 m/S; the Mt Partridge Group has a conductivity value up to 100 m/S; the Kombolgie Sandstone has a conductivity range of less than 2 m/S in more areas. Detecting conductivity contrasts in areas with known uranium prospectivity aids in a mineral systems analysis and geological interpretation of uranium deposits.

This record reports on an AGSO/PIRSA/CRC LEME/Dominion Mining AEM Interpretation Workshop. The workshop focused on AEM data acquired over the Challenger Prospect in South Australia.

Presentation to minerals industry representatives at the Geological Survey of Western Australia, 4 May 2010.

Presentation to minerals industry representatives at the Geological Survey of Western Australia, 4 May 2010.

During 2007 and 2008 and under the Australian Government's Onshore Energy Security Initiative, Geoscience Australia acquired airborne electromagnetic (AEM) data over the Paterson Province of Western Australia. The main purpose of the survey was to provide additional geophysical/geological context for unconformity and palaeochannel style uranium mineral systems and thereby promote related exploration. The survey data will also provide information on depth to basement, which is of general interest to explorers, and will be used as an input into a ground water evaluation of the region.

This GIS data package contains airborne electromagnetic (AEM) datasets and interpreted data products for the Barr Creek-Gunbower survey area, as part of the River Murray Corridor (RMC) Salinity Mapping and Interpretation Project. The RMC project was undertaken between 2006 and 2010 to provide information on a range of salinity and land management issues along a 450 kilometre reach of the Murray River from the South Australian border to Gunbower, northwest of Echuca in Victoria. The Barr Creek-Gunbower survey area is a large NW-SW trending area along the Murray River between Swan Hill and Gunbower. This metadata briefly describes the contents of the data package. The user guide included in the package contains more detailed information about the individual datasets and available technical reports. The main components in the package are: AEM data and images derived from a holistic inversion of the RMC RESOLVE AEM survey; a composite digital elevation model (DEM); a range of interpreted data products designed to map key elements of the hydrogeological system and salinity hazards using the AEM dataset; and a series of ESRI ArcGIS map documents. The AEM data component consists of grids and images of modelled conductivity data derived from a holistic inversion of the RMC RESOLVE AEM survey. They include: layer conductivity grids below ground surface; depth slice grids representing the average conductivity of various regular depth intervals below ground surface; floodplain slice grids representing the average conductivity of various depth intervals relative to the elevation above or below a smooth surface that approximates the River Murray floodplain; watertable slice grids representing the average conductivity of various intervals relative to the elevation above or below the regional watertable; and AEM cross sections of conductivity versus depth along each of the flight lines. The holistic inversion AEM data are derived from the 'River Murray Corridor RESOLVE AEM Survey, VIC & NSW, 2007 Final Data (P1141)', available as Geoscience Australia product number 67212 (GeoCat #67212). The DEM data component consists of a 10 metre horizontal resolution composite DEM for the River Murray Corridor AEM survey area derived from airborne light detection and ranging (LiDAR) surveys, AEM surveys and the shuttle radar topography mission (SRTM) survey. The interpreted data component is organised into product themes to address salinity and land management questions and to map key elements of the hydrogeological system and salinity hazards using the AEM dataset. An ArcGIS map document is included for each product theme. The products include: conductive soils; flush zones; groundwater conductivity; near surface conductive zones; near surface resistive zones; Parilla Sands; Quaternary alluvium; recharge; salt store; Shepparton Formation; stratigraphic extents and reliability; surface salt; and vegetation health. The RMC project was funded through the National Action Plan for Salinity and Water Quality with additional funding from the Lower Murray Catchment Management Authority (CMA), Mallee CMA, Goulburn-Murray Water and the Murray-Darling Basin Authority. The project was administered by the Australian Government Department of Agriculture, Fisheries and Forestry through the Bureau of Rural Sciences, now known as the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES). Geoscience Australia (GA) were contracted to provide geophysical services to manage the AEM system selection and data acquisition, and to process and calibrate the AEM data. The AEM survey was flown by Fugro Airborne Geophysical Services in 2007 using the helicopter-borne RESOLVE frequency domain system. The Cooperative Research Centre for Landscape Environments and Mineral Exploration was sub-contracted through GA to manage the interpretation and reporting component of the RMC project.