Geoscience Australia flew three regional airborne electromagnetic (AEM) surveys as part of the Australian Government's 5-year Onshore Energy Security Program in 2007-08 (Paterson, WA), 2009 (Pine Creek, NT) and 2010 (Frome, SA). The aims of the surveys were to reduce risk and stimulate exploration investment for uranium by providing reliable pre-competitive data. When the data and interpretations of the surveys were released, there was a measurable upswing in industry investment in and around the survey areas and a number of new discoveries were made using the new data. Geoscience Australia is committed to the Australian Academy of Science's Searching the Deep Earth (UNCOVER) initiative, which has been adopted by Geoscience Australia as part of its long-term strategic planning. To assist this initiative, we are assessing the potential of AEM to characterise areas that are prospective for a range of commodities including gold, copper, lead, zinc, nickel, platinum group elements and rare earth elements, as well as uranium. The assessment will also extend to the potential for mapping geology under cover to explorable depths (< 400 m), mapping cover thickness around the flanks of major outcrop areas and providing new information on groundwater resources. Potential new areas for regional AEM surveying could include (in no particular order of priority): the Westmoreland region; the Georgetown Inlier; the Mt Isa region; the Broken Hill region, the Peake and Denison Ranges; the Eyre Peninsula (Gawler Craton); the Ngalia-Amadeus region; the Musgrave Province; the Windimurra Igneous Complex; the Capricorn-Ashburton area; the Lachlan-Thomson orogens; the Stawell and Ballarat areas; the southeast Yilgarn region (Yilgarn Craton flanks); and, the Tanami area.

Geoscience Australia is releasing into the public domain software for the inversion of airborne electromagnetic (AEM) data to a 1D conductivity depth structure. The software includes two different algorithms for 1D inversion of AEM data. The first is a gradient based deterministic inversion code for multi-layer (smooth model) and few-layered (blocky-model) inversions. The second is a reversible-jump Markov chain Monte Carlo stochastic inversion algorithm suitable for assessing model uncertainty. A forward modelling program and some other ancillary programs are also included. The code is capable of inverting data from all of the commercial time-domain systems available in Australia today, including dual moment systems. The software is accessible in three forms. As C++ source code, as binary executables for 64 bit Windows® PCs, and as a service on the Virtual Geophysics Laboratory (VGL). The code is fully parallelized for execution on a high performance cluster computer system or on a multi-core shared memory workstation via either the MPI or the OpenMP programming models.

The 2016 Lawn Hill VTEM™Plus airborne electromagnetic (AEM) survey was funded under the Queensland Government’s Future Resources (Mount Isa Geophysics) Initiative and managed by Geoscience Australia on behalf of the Geological Survey of Queensland. The survey covers an area of 3215 km2 which aims to attract explorers into ‘greenfield’ terranes and contribute to the discovery of the next generation of major mineral and energy deposits under shallow sedimentary cover. The survey is an extension to the 2016 East Isa VTEM™Plus Survey (eCAT:104700)

The 2016 Southern Thomson Orogen VTEM™Plus AEM Survey was conducted by Geoscience Australia as part of a collaborative investigation between the Commonwealth of Australia (Geoscience Australia) and its partners the State of New South Wales (Department of Trade and Investment, Geological Survey of New South Wales) and the State of Queensland (Department of Natural Resources and Mines, Geological Survey of Queensland). The Project aims to better understand the geological character and mineral potential of the southern Thomson Orogen region, focusing on the border between New South Wales and Queensland, by acquiring and interpreting multi-disciplinary geophysical, geochemical and geological data. The primary intended impact of this work is to provide the mineral exploration industry with pre-competitive data and knowledge that reduces risk and encourages mineral exploration in the region. Geoscience Australia contracted Geotech Airborne Pty Ltd to acquire VTEM™Plus AEM data over part of the Southern Thomson Orogen in Queensland and New South Wales in May and June 2016.The data were also processed by Geotech Airborne Ltd using its FullWaveForm® processing techniques. The survey area consists of 2415 line km of time-domain AEM geophysical data acquired in five survey blocks. The majority of traverse lines were spaced at 5000 m in an east-west direction, further details about each blocks flight line specifications can be found in Table 1. The original data supplied by Geotech Airborne Pty Ltd has been modified to contain the final data fields of principal interest, enabling a manageable data file size. This data is available from Geoscience Australia's website free of charge. The comprehensive dataset is available from Geoscience Australia by emailing mineralgeophysics@ga.gov.au. The data release package includes: - Point-located electromagnetic dB/dt and derived B-field data with associated position, altimeter, orientation, magnetic gradiometer, and derived ground elevation data. These data are in ASCII column format with associated README and ASEG-GDF2 header files. The dataset consists of a separate download file for the: - Survey Lines - Repeat lines - Waveform files for every flight containing the 192 kHz sampling of the transmitter current and receiver waveforms. - Point-located conductivity estimates derived using the EM Flow® conductivity depth imaging (CDI) algorithm with associated position, altimeter, orientation, magnetic gradiometer, and derived ground elevation data. Data include the conductivity estimate for each 5 m interval and selected depth slices. - Gridded data, at 1 km cell size in, for the conductivity depth slices derived from the EM Flow® CDI data, magnetics and elevation data in ER Mapper® binary raster grid format with associated header files. - Graphical multiplots, in PDF format, for each flight line showing EM Flow® CDI sections and profiles of Z-component dB/dt data, magnetics, powerline monitor, height and orientation data. - Contractor supplied Operations Report. - ESRI shapefiles and KML files of flight lines. - Metadata and License files.

Precompetitive AEM data and associated scientific analysis assists exploration under cover by reducing risk, stimulating investment and promoting exploration for commodities. In recent years, Geoscience Australia has flown three regional Airborne Electromagnetic (AEM) surveys covering three percent of Australia. Data and associated interpretations from regional surveys in the Paterson, Pine Creek and Lake Frome regions have led to tenement take up, stimulated exploration for a number of commodities and have given rise to many Eureka moments. This presentation will outline significant results from the use of Geoscience Australia AEM data and interpretations, results that have been announced by industry via the Australian Stock Exchange and other publications.

The GEOPHYS_SURV database describes geophysical surveys (air, land, and marine), the datasets derived from those surveys, and the methods used for delivery of those datasets. The database includes metadata for all surveys conducted or managed by Geoscience Australia and its predecessor agencies, as well as data and surveys from State and Territory geological survey agencies.

Nuclear Magnetic Resonance data may be used to estimate physical properties such as water content, NMR relaxation time, and porosity of formations penetrated by boreholes. These data were acquired as part of the Exploring for the Future (EFTF) program at field sites within the East Kimberley and Southern Stuart Corridor field areas.

<p>Seawater intrusion (SWI) has become a serious threat to many groundwater resources in the last decades, especially in the areas of overexploitation due to population increase, or agriculture use. Significant attention was therefore brought to this complex groundwater problem in order to improve management of these affected aquifers. <p>Due to the high conductivity of seawater, SWI is a good target for many geophysical electromagnetic methods, such as airborne electromagnetic (AEM) or direct current resistivity methods. Airborne collected data are able to map extensive areas, and thus map the extent of SWI on a large scale along the coastlines. <p>However, zooming into a smaller scale, a discrepancy is often found between geophysical estimates and groundwater borehole data, due to different resolution, data sensitivity and also quality of geophysical and groundwater data. Numerous synthetic studies have shown the benefit of approaching the problem by evaluating both types of data in somewhat jointly manner. Research in combining the field geophysical and groundwater data for SWI cases is however very limited. <p>In this contribution we look at the AEM survey in Keep river, NT. It is a dense line survey with spacing of 100m, collected by SKyTEM 312 system for Geoscience Australia. Due to the character of AEM methods, the estimation of 3D (or 2D) subsurface conductivity is mathematically an ill-posed problem, giving multiple “equally good” models (here soil bulk conductivity) with the same data misfit. <p>The borehole data from this area together with geological mapping provide limited (1D) but valuable information about the seawater intrusion location and extent. We applied this “a priori” information coming from direct groundwater data to invert the selected lines of AEM data to obtain estimates that fit well the geophysical data but are also plausible with regard to geology and groundwater chemistry data.

ASEG 2016 Conference abstract. AMT and BBMT data have been applied by Geoscience Australia to determine the nature and thickness of cover, plus the basement architecture in regions around Australia. The depth of cover assessment produced by MT agrees with depth of cover assessments made by other geophysical techniques and will be tested by an ongoing program of stratigraphic drilling.

For the first time, the 3 D model reveals upper-mantle enhanced conductivity anomalies beneath Archaean cratonic regions and Phanerozoic terranes imaged by the AWAGS dataset. These anomalies are consistent with the results of two recent magnetotelluric surveys, one along a profile in the Yilgarn-Officer Basin-Musgrave Block, another in the Gawler Craton region. Across much of central Australia a resistivity gradient in the middle lithosphere is observed. This region corresponds well with a recognised seismic velocity gradient across the middle-lithosphere boundary. Resistivity differences are also observed for the first time beneath Archaean cratons in Western Australia. The Pilbara Craton is represented as an enhanced conductivity anomaly at middle lithosphere depth, corresponding well with the lower-velocity anomaly evident in surface wave tomography models. The Yilgarn Craton is imaged as a resistive body, exceeding 104 ohm m, continuing to greater depths.