The use of airborne electromagnetics (AEM) for hydrogeological investigations often requires high resolution data. Optimisation of AEM data therefore requires careful consideration of AEM system suitability, calibration, validation and inversion methods. In the Broken Hill managed Aquifer Recharge (BHMAR) project, the helicopter-borne SkyTEM transient EM system was selected after forward modeling of system responses and assessment of test line data over potential targets. The survey involved acquisition of 31,834 line km of data over an area of 7,500 km2 of the River Darling Floodplain, and was acquired by two systems over a 9-week period.. Initial Fast Approximate Inversions (FAI) provided within 48 hours of acquisition were used to target 100 sonic and rotary mud holes for calibration and validation. A number of different (Laterally and Spatially Constrained) inversions of the AEM data were carried out, with refinements made as additional information on vertical and lateral constraints became available. Finally, a Wave Number Domain Approximate Inversion procedure with a 1D multi-layer model and constraints in 3D, was used to produce a 3D conductivity model. This inversion procedure only takes days to run, enabling the rapid trialing to select the most appropriate vertical and horizontal constraints. Comparison of borehole induction logs with adjacent AEM fiduciary points confirms high confidence levels in the final inversion. Using this approach has produced quantitative estimates of the 3D conductivity structure that provide a reliable platform for identifying new groundwater resources and a range of MAR options, and developing new geological and hydrogeological conceptual models. Integration of the AEM data with borehole lithology, textural, mineralogical, groundwater and pore fluid hydrochemical and borehole NMR data has enabled maps of hydrostratigraphy, hydraulic conductivity, groundwater salinity, salt store and neotectonics to be produced.

Broken Hill Managed Aquifer recharge Projects 3D models and Fly-through

The 'River Murray Corridor (RMC) Salinity Mapping Project', provides important new information in relation to salinity hazard and management along in a 20 km-wide swath along a 450 km reach of the River Murray. The project area contains iconic wetlands, national and state forest parks, irrigation and dryland farming assets and the Murray River, significant areas of which are at risk from increasing salinisation of the River, the floodplain, and underlying groundwater resources. The project utilised a hydrogeological systems approach to integrate and analyse data obtained from a large regional airborne electromagnetic (AEM) survey (24,000 line km @ 150m line-spacing in a 20 km-wide swath along the Murray River), field mapping, and lithological and hydrogeochemical data obtained from drilling. New holistic inversions of the AEM data have been used to map key elements of the hydrogeological system and salinity extent in the shallow sub-surface (top 20-50 m). The Murray River is known to display great complexity in surface-groundwater interactions along its course. Electrical geophysical methods (such as AEM) are able to map surface-groundwater interaction due to the contrast between (electrically resistive) fresh water in the river, and (electrically conductive) brackish to saline groundwater in adjacent sediments. The location of significant river flush zones is influenced both by underlying geology and the location of locks, weirs and irrigation districts. The study has also identified significant areas of high salinity hazard in the floodplain and river, and quantified the salt store and salt load across the floodplain. The study has also identified sub-surface factors (including saline groundwater, shrinking flush zones, declining water tables) linked to vegetation health declines.

The Pine Creek AEM survey was flown over the Pine Creek Orogen in the Northern Territory during 2008 and 2009 as part of the Australian Government's Onshore Energy Security Program at Geoscience Australia (GA). The survey covers an area of 74,000 km2 from Darwin to Katherine in the Northern Territory which hosts several world class deposits, including the Ranger Uranium Mine, Nabarlek, Mt Todd, Moline and Cosmo Howley. Aimed at regional mapping, uranium exploration, reducing exploration risk and promoting exploration activity, the program worked closely with industry partners to infill wide regional line spacing (5km) with deposit scale line spacing (less than 1km). The survey results are relevant in exploration for a variety of commodities and resources, including uranium, copper, lead, zinc, gold, nickel and groundwater. Geoscience Australia's interpretation products include sample-by-sample layered earth inversion products comprising located data, geo-located conductivity depth sections, depth slice grids, elevation slice grids, inversion report and an interpretation report. All data and products are available from GA as well as the Northern Territory Geological Survey Geophysical Image Web Server.

The use of airborne electromagnetics (AEM) for hydrogeological investigations often requires high resolution data. Optimisation of AEM data therefore requires careful consideration of AEM system suitability, calibration, validation and inversion methods. In the Broken Hill managed Aquifer Recharge (BHMAR) project, the helicopter-borne SkyTEM transient EM system was selected after forward modelling of system responses and assessment of test line data over potential targets. The survey involved acquisition of 31,834 line km of data over an area of 7,500 km2 of the River Darling Floodplain. Initial FAI inversions provided within 48 hours of acquisition were used to target 100 sonic and rotary mud holes for calibration and validation. A number of different (Laterally and Spatially Constrained) inversions of the AEM data were carried out, with refinements made as additional information on vertical and lateral constraints became available. Finally, a Wave Number Domain Approximate Inversion procedure with a 1D multi-layer model and constraints in 3D (including boreholes), was used to produce a 3D conductivity model. This inversion procedure only takes days to run, enabling rapid trialling to select the most appropriate vertical and horizontal constraints. Using this approach has produced reliable, quantitative estimates of the 3D conductivity structure, and enabled identification of a diverse range of MAR options and groundwater resources. The hydrogeological complexity revealed by AEM mapping greatly improves the parameterisation of groundwater models, and provides a framework for understanding complex hydrogeological and hydrogeochemical processes that are critical to assessment of a range of MAR, surface water and groundwater extraction options.

The Paterson AEM survey was flown over the Paterson Orogen, the eastern Pilbara Craton and the on-lapping Officer and Canning Basins in NW Western Australia between September 2007 and October 2008 as part of the Commonwealth Government's Onshore Energy Security Program. The survey was designed to provide pre-competitive data for enhancing uranium and other mineral exploration. Flight lines were at a variety of spacings from 6, 2 and 1 km to 200 m targeting known deposits and other covered highly prospective rocks for a total area of 45,330 km2. The survey data has afforded new insights into the Paleozoic paleotopography of the region which is blanketed by regolith including Phanerozoic sediments including Permian glaciogene, Mesozoic and Cenozoic sediments. These insights have major implications for mineral prospectivity.

The Frome airborne electromagnetic (AEM) survey is the largest of three regional AEM surveys flown under the 5-year Onshore Energy Security Program (OESP) by Geoscience Australia (GA). The aim of the survey is to reduce risk and stimulate exploration investment for uranium by providing reliable pre-competitive data. The Frome AEM survey was flown between 22 May and 2 November 2010, is approximately 95 450 km2 in area and collected 32 317 line km of new data at an average flying height of 100 m. The Frome AEM survey covers the Marree (pt), Callabonna (pt), Copley (pt), Frome (pt), Parachilna (pt), Curnamona, Olary and Chowilla (pt) 1:250 000 standard map sheets in South Australia and was flown largely at 2.5 km line spacing, with the northern portion flown at 5 km line spacing. GA partnered with, the Department of Primary Industries and Resources South Australia and an industry consortium. The survey results indicate a depth of investigation (DOI - depth of reliable signal penetration) of up to 400 m in areas of thin cover and resistive basement (e.g., Adelaidean rocks in the Olary Ranges). In Cenozoic - Mesozoic sediments in the Frome Embayment and the Murray Basin the DOI is up to 100-150 m. A range of under-cover features are revealed, including (but not limited to): extensions to known palaeovalley networks in the Frome Embayment; the under-cover extent of the Benagerie Ridge; regional faults in the Frome Embayment and Murray Basin; folded and faulted Neoproterozoic rocks in the Adelaide Fold Belt; Cenozoic - Mesozoic stratigraphy in the Frome Embayment; neotectonic offsets in the Lake Eyre Basin; conductive Neoproterozoic rocks associated with copper-gold mineralisation; and, coal-bearing structures in the Leigh Creek area, as well as groundwater features.

Under the Community Stream Sampling and Salinity Mapping Project, the Australian Government through the Department of Agriculture, Fisheries and Forestry and the Department of Environment and Heritage, acting through Bureau of Rural Sciences, funded an airborne electromagnetic (AEM) survey to provide information in relation to land use questions in selected areas along the River Murray Corridor (RMC). The proposed study areas and major land use issues were identified by the RMC Reference Group at its inception meeting on 26th July, 2006. This report has been prepared to facilitate recommendations on the Lindsay-Wallpolla study area. The work was developed in consultation with the RMC Technical Working Group (TWG) to provide a basis for the RMC Reference Group and other stake holders to understand the value and application of AEM data to the study area. This understanding, combined with the Reference Group's assessment of the final results and taking in account policy and land management issues, will enable the Reference Group to make recommendations to the Australian Government.

More recently the O'Farrell government has called for expressions of interest to explore for uranium across NSW. Fugro Airborne Services Pty Ltd also called for expressions of interest in flying a large TEMPEST AEM survey in NSW covering the NSW Curnamona Province and portions of the Murray-Darling Basin and Lake Eyre Basin, abutting the SA border, to complement the Frome AEM Survey. The following is a brief summary of some of the main points discussed and presented during 3 presentations at the NSWGS on 19 September 2012, and in follow-up discussions on 20 September 2012. Approximately 40 people attended the three presentations. A discussion after the talks centred around using AEM in NSW for regional mapping including for uranium, porphyry copper-gold systems and massive sulphide systems. PowerPoint presentations were left with NSWGS. Three abstracts describing these presentations are included at the end of this document.

No abstract available