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.

Alan Yusen Ley-Cooper Ross C. Brodie Inversion of SPECTREM AEM data for conductivity and system geometry We evaluate the use of airborne electromagnetic data from the SPECTREM2000 system flown for ore body detection, regolith mapping and assessment of aquifers. Since the position and orientation of the receiver bird are not measured, the primary field at the bird cannot be known and removed precisely. In order to successfully invert the AEM data, and produce conductivity-depth models, we first reinstate the removed primary field estimate and convert the data from ppm units to Teslas. We then simultaneously inverted the X and Z component data, to solve for a 1D layered conductivity model and receiver position. The SPECTREM system has flown many line kilometres in other parts of the world but substantially less in Australia. Through further processing and inversions we have resolved conductivity-depth structures very similar to those previously obtained from other well-established AEM systems flown under Australian conditions. We also present a section of AEM data with logged drilling core data as a means of assessment of our inversion models against an independent data set. Key words: Airborne EM, inversion, geometry, SPECTREM, electrical conductivity.

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.

As part of the Australian Government's Onshore Energy Security Program (2006-2011) Geoscience Australia in collaboration with Geological Survey of Western Australia acquired magnetotelluric (MT) data along the deep crustal seismic reflection transect across the Yilgarn Craton, Officer Basin and Musgrave Province in Central Western Australia. The aim of the MT survey is to map the electrical resistivity distribution and improve scientific understanding of the crustal and upper mantle structure in this region. This information is complementary to that obtained from deep crustal seismic reflection, seismic refraction, potential field and geological data, which together provide new knowledge of the crustal architecture and geodynamics of the region. It is important for helping to determine the potential for both mineral and energy resources. Data are supplied as EDI files with support information.

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.

Geoscience Australia first sought feedback on a metadata standard for magnetotelluric (MT) time-series data in 2018 with the publication of a Preview article (Kirkby, 2019) outlining suggestions for metadata fields that should be collected when running an MT survey. This was the first step in standardising the MT formats used by the Australian MT community to ensure a cohesive community approach moving forward. Intrepid Geophysics was subsequently contracted by Geoscience Australia to investigate the current community sentiment around a metadata standard and report on the community’s requirements for a standardised data format. Intrepid Geophysics was chosen as an independent party that had no significant stake in the magnetotellurics discussion. This report is the third made to Geoscience Australia in a series investigating the needs of the Australian magnetotelluric community, with a focus on the definition of the metadata that should be collected along with the raw data of an MT survey. The findings were collated from interviews conducted in the preliminary stage of the project as well as an online questionnaire that was sent to those who had agreed to be contacted. Feedback was constructive, centring on standardisation of parameter naming schemes, adding parameters that were missing and could add value, and misclassification of parameters. Future work should focus on a more widespread community engagement program that involves system manufacturers as well as building the metadata structure around the chosen data format.

The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) aims to collect long period magnetotelluric (MT) sites on a 0.5 degree (~55 km) grid across the Australian continent. Data and models produced from this program will help to inform our understanding of Australia’s lithospheric architecture and tectonic processes. The New South Wales component of AusLAMP is a collaborative project between Geoscience Australia and the Geological Survey of New South Wales. This new dataset will add to the coverage of the Victorian and South Australian AusLAMP programs, which are both complete. This presentation is prepared for the Mines and Wines Conference, 2019, and details the progress of the AusLAMP NSW program. These include data, models and preliminary interpretations that are coming out of the program. Presentation for Discovery in the Tasmanides (Mines and Wines), Wagga Wagga, NSW, 25-28 September 2019 (https://smedg.org.au/events/)