Building on newly acquired airborne electromagnetic and seismic reflection data during the Exploring for the Future (EFTF) program, Geoscience Australia (GA) generated a cover model across the Northern Territory and Queensland, in the Tennant Creek – Mount Isa (TISA) area (Figure 1; between 13.5 and 24.5⁰ S of latitude and 131.5 and 145⁰ E of longitude) (Bonnardot et al., 2020). The cover model provides depth estimates to chronostratigraphic layers, including: Base Cenozoic, Base Mesozoic, Base Paleozoic and Base Neoproterozoic. The depth estimates are based on the interpretation, compilation and integration of borehole, solid geology, reflection seismic, and airborne electromagnetic data, as well as depth to magnetic source estimates. These depth estimates in metres below the surface (relative to the Australian Height Datum) are consistently stored as points in the Estimates of Geophysical and Geological Surfaces (EGGS) database (Matthews et al., 2020). The data points compiled in this data package were extracted from the EGGS database. Preferred depth estimates were selected to ensure regional data consistency and aid the gridding. Two sets of cover depth surfaces (Bonnardot et al., 2020) were generated using different approaches to map megasequence boundaries associated with the Era unconformities: 1) Standard interpolation using a minimum-curvature gridding algorithm that provides minimum misfit where data points exist, and 2) Machine learning approach (Uncover-ML, Wilford et al., 2020) that allows to learn about relationships between datasets and therefore can provide better depth estimates in areas of sparse data points distribution and assess uncertainties. This data package includes the depth estimates data points compiled and used for gridding each surface, for the Base Cenozoic, Base Mesozoic, Base Paleozoic and Base Neoproterozoic (Figure 1). To provide indicative trends between the depth data points, regional interpolated depth surface grids are also provided for the Base Cenozoic, Base Mesozoic, Base Paleozoic and Base Neoproterozoic. The grids were generated with a standard interpolation algorithm, i.e. minimum-curvature interpolation method. Refined gridding method will be necessary to take into account uncertainties between the various datasets and variable distances between the points. These surfaces provide a framework to assess the depth and possible spatial extent of resources, including basin-hosted mineral resources, basement-hosted mineral resources, hydrocarbons and groundwater, as well as an input to economic models of the viability of potential resource development.

For the AusAEM Year 1 survey an inertial measurement unit (IMU) was installed for the first time on the TEMPEST receiver bird to measure its orientation and to augment GPS derived positioning of the receiver. This has given us the opportunity to develop better quality control and calibration procedures, which would otherwise not be possible. Theoretical modelling of the primary field on high altitude zero-lines, using the full position/orientation information, revealed discrepancies between observed and modelled data. It alerted us to time-lag parallaxes between EM and bird position/orientation data, some spurious IMU data on many pre-flight zero-lines, and a coordinate system sign convention inconsistency. The modelling also revealed systematic differences that we could attribute to the calibration of the receiver pitch and EM data scaling. We developed an inversion algorithm to solve for a receiver pitch offset and an EM scaling calibration parameter, for each zero-line, which minimised the systematic discrepancies. It eventuated that the calibration parameters fell into five distinct populations explicable by significant equipment changes. This gave us the confidence to use the medians of these populations as parameters to calibrate the data. The work shows the value of the new receiver bird orientation data and the importance of accurate IMU calibration after any modification. It shows the practical utility of quantitative modelling in the quality control workflow. It also demonstrates how modelling and inversion procedure can be used to successfully diagnose calibration issues in fixed-wing AEM data. Presented at the 2019 Australasian Exploration Geoscience Conference

Geoscience Australia, in collaboration with state governments, will be carrying out airborne electromagnetic (AEM) surveys in western South Australia, southern NT and eastern WA during 2022. This scientific research is being carried out to obtain data that will enhance understanding of geology and natural resources of the region. This information will support future resource management decision-making. This survey has been expanded into Western Australia with funding from the Geological Survey of Western Australia, combined with valuable in-kind support from the South Australian and Northern Territory geological surveys. <p>

AusAEM-WA, Murchison Airborne Electromagnetic Survey Blocks: SkyTEM® airborne electromagnetic data and GALEI inversion conductivity estimates The accompanying data package, titled “AusAEM–WA, Murchison Airborne Electromagnetic Survey Blocks: SkyTEM® airborne electromagnetic data and GALEI inversion conductivity estimates”, was released on March 2022 by Geoscience Australia (GA) in collaboration with the Geological Survey of Western Australia. The data represents the first second of the AusAEM2020 (WA) survey flown with a with a rotary aircraft contracted to Geoscience Australia, using the SkyTEM® airborne electromagnetic system. The survey was flown at a 20-kilometre nominal line spacing over the most over the Murchison area and across to the west coast of Western Australia. The area encompasses over 17,600 line kilometres of newly acquired airborne electromagnetic geophysical data. This package contains (~17,600 kms) of the total of survey data which have been quality-controlled, processed, modelled and inverted both by the contractor and by GA. The survey was divided in four blocks, flown east-west. All four block’s projected grid coordinates have been supplied in GDA2020 MGA Zone 50 datum, and contain the geodetic latitude and longitude coordinate fields. Geoscience Australia and Western Australia (Department of Mines, Industry Regulation and Safety) commissioned the AusAEM 2020 survey as part of the national airborne electromagnetic acquisition program, to complete 20km line separation AEM coverage over WA. The program is designed to deliver freely available pre-competitive geophysical data to assist in the investigation and discovery of potential mineral, energy and groundwater resources within Australia. Funding for the survey came from the Western Australian government’s Exploration Incentive Scheme and additional support from the State’s COVID-19 recovery plan. Geoscience Australia managed the survey data acquisition, processing, contracts, quality control of the survey and generated the inversion products included in the data package. The data release package contains 1. A data release package summary PDF document. 2. The survey logistics and processing report. 3. KML and Shapefiles for the regional flight lines. 4. Final processed point located line data in ASEG-GDF2 format. 5. Conductivity estimates generated by SkyTEM’s Workbench. 6. Conductivity estimates and products (suitable for various 3D packages) generated by Geoscience Australia's Layered Earth Inversion algorithm.

<p>Geoscience Australia commissioned the AusAEM Year 1 NT/QLD survey as part of the Exploring for the Future (EFTF) program, flown over parts of the Northern Territory and Queensland. The EFTF program is led by Geoscience Australia (GA), in collaboration with the Geological Surveys of the Northern Territory, Queensland, South Australia and Western Australia. The program was designed to investigate the potential mineral, energy and groundwater resources in northern Australia and South Australia. <p>The survey was flown during the 2017-2018 field season, using the TEMPEST® airborne electromagnetic (AEM) system operated by CGG Aviation (Australia) Pty. Ltd under contract to Geoscience Australia. AusAEM Year 1 was acquired with a 20-kilometre line separation and collected over 60,000 line kilometres of data in total. The AusAEM Year 1 NT/QLD survey also includes over 1,500 line kilometres of infill flying, which, was funded by private exploration companies in certain infill blocks within the survey area. The data from these infill blocks are now part of Geoscience Australia release to the public domain, for use in the minerals, energy and groundwater sectors. <p> Previously Released data (Phase 1) <p>In December 2018, we released a package, which contains data from the AusAEM Year 1 NT/QLD Airborne Electromagnetic Survey Phase 1. <p>This data package, with eCat ID 124092 titled “AusAEM Year 1 NT/QLD Airborne Electromagnetic Survey, TEMPEST® airborne electromagnetic data and Em Flow® conductivity estimates”. The package contains a) survey logistics and processing report, b) final processed electromagnetic, magnetic and elevation point located line data, c) processed electromagnetic, magnetic and elevation grids, d) point located conductivity estimates from EM Flow®, e) multi-plots of line data and conductivity sections, all produced by the contractor CGG Aviation (Australia) Pty. These products are downloadable from Geoscience Australia’s website: (See http://www.ga.gov.au/metadata-gateway/metadata/record/gcat_124092). <p>The data provides new insights into vast areas in Northern Australia that have not been extensively explored previously. <p>Current Release (Phase 2) <p>This Phase 2 data release package contains results from inverting the electromagnetic data in the Phase 1 release. The inversion results were generated using Geoscience Australia's sample-by-sample layered-earth (1D) inversion, a deterministic regularized gradient-based algorithm, which we call GALEISBS (Brodie, 2016). <p>For the inversion of TEMPEST AEM data we have conventionally inverted the total (primary plus secondary) measured X-and Z-component data simultaneously to produce a single smooth layered conductivity model. To achieve convergence and derive an acceptable model and acceptable data misfits, we have found that it is necessary to solve for three geometry parameters; (1) Transmitter (Tx) –Receiver (Rx) horizontal in-line and 2) vertical separations and 3) the receiver pitch. This is the case even with the new Rx bird IMU measurements and calibrated data (Ley-Cooper et.al, 2019.). <p>We have extended the GALEISBS functionality to allow inversion of the vector sum of the X- and Z-component data. The rationale of modifying the algorithm is to eliminate the need to solve for Rx pitch, since the vector sum of the X- and Z-component data are insensitive to the Rx pitch. In doing this, we are gaining some robustness by not having to solve for one of the geometry parameters; however, the trade-off is that we are in essence losing the information implicit in the vector component data. <p>The inversions we deliver here we derived from a recently implemented XZ–vector-sum inversion, described in Ley-Cooper et.al, 2019. <p>The GALEISBS inversion products are available for download in parts based on the type of derived product. These are zipped into the following three files: <p>1. galeisbs_vector_sum_point_located_data_ascii.zip <p>2. galeisbs_vector_sum_point_located_data_geosoft.zip <p>3. galeisbs_vector_sum_sctions.zip <p>4. galeisbs_vector_sum_gocad_sgrids.zip

Airborne electromagnetic data generated by the AusAEM Survey are shown to map mineral deposit host rocks and regional geological features within the AusAEM Survey area. We have developed new functionality in Geoscience Australia’s sample-by-sample layered earth inversion algorithm, allowing inversion of the magnitude of the combined vector sum of the X- and Z-components of TEMPEST AEM data. This functionality improves the clarity of inverted interpretation products by reducing the degree of along-line incoherency inherent to stitched 1D inversions. The new inversion approach improves the interpretability of sub-horizontal conductors, allowing better mapping of geological features under cover. Examples of geological mapping by the AusAEM survey highlight the utility of wide line spacing, regional AEM surveying to improve geological, mineral systems and groundwater resource understanding in the regions flanking outcropping mineral deposit host rocks in northern Australia. Presented at the 2019 Australasian Exploration Geoscience Conference

The Exploring for the Future (EFTF) program is unmatched for the scale of geoscience data acquisition across northern Australia, covering 37 648 individual land parcels and 2.9 million km2. The scale of works has raised many new challenges for Geoscience Australia (GA) through the diverse range of field activities, and the numerous stakeholders from different social and cultural backgrounds, across multiple jurisdictions. Success of the program depended on the development and maintenance of a social licence to operate. This was broadly achieved for fieldwork activities through early engagement with stakeholders, including free, prior and informed consent. Here, we present two case studies of stakeholder engagement for facilitation of data collection: one focuses on broadscale, low-impact field activities associated with the AusAEM survey; and the other on Indigenous-focused engagement related to the Barkly Seismic Survey. Because of the complexity of project planning and managing such a large number of stakeholders, GA’s project governance team was expanded; it now includes a dedicated Land and Marine Access team and a commitment to adopt world-leading engagement practices. One practice is to consider impacts and benefits for all stakeholders—not just landholders—of field activities and data acquisition programs. This includes a plan for how the data are delivered back to the communities and stakeholders, and how information exchanges can be built into projects. The aim is for stakeholders to hold GA in the highest regard and understand the benefits to the Australian people, and ultimately their own communities, from the geoscientific data that GA produces. <b>Citation:</b> Mouthaan, R., Buchanan, S. and Sweeney, M, 2020. Land access and Indigenous engagement for Australian geoscience. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

The AusAEM1 survey is the world’s largest airborne electromagnetic survey flown to date, extending across an area exceeding 1.1 million km2 over Queensland and the Northern Territory. Approximately 60 000 line kilometres of data were acquired at a nominal line spacing of 20 km. Using this dataset, we interpreted the depth to chronostratigraphic surfaces, assembled stratigraphic relationship information, and delineated structural and electrically conductive features. Our results improved understanding of upper-crustal geology, led to 3D mapping of palaeovalleys, prompted further investigation of electrical conductors and their relationship to structural features and mineralisation, and helped us continuously connect correlative outcropping units separated by up to hundreds of kilometres. Our interpretation is designed to improve targeting and outcomes for mineral, energy and groundwater exploration, and contributes to our understanding of the chronostratigraphic, structural and upper-crustal evolution of northern Australia. More than 150 000 regional depth measurements, each attributed with detailed geological information, are an important step towards a national geological framework, and offer a regional context for more detailed, smaller-scale AEM surveys. <b>Citation:</b> Wong, S.C.T., Roach, I.C., Nicoll, M.G., English, P.M., Bonnardot, M.-A., Brodie, R.C., Rollet, N. and Ley-Cooper, A.Y., 2020. Interpretation of the AusAEM1: insights from the world’s largest airborne electromagnetic survey. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

The AusAEM Year 1 NT/QLD Airborne Electromagnetic Survey covers the Newcastle Waters and Alice Springs 1:1 Million map sheets in the Northern Territory, plus the Normanton and Cloncurry 1:1 Million map sheets in Queensland. The survey was flown at 20 kilometre line spacing and entails approximately 60,000 line kilometres of data in total. The data were acquired in 2017 and 2018 by CGG Aviation (Australia) Pty. Ltd. (CGG), under contract to Geoscience Australia, using the TEMPEST® airborne electromagnetic system. The data were also processed by CGG. This Tranche 1 data release package only contains approximately the first one third (19,500 line kilometres) of the survey data that were acquired between August 4 and October 7, 2017. The AusAEM Year 1 NT/QLD survey also included over 1,500 line kilometres of infill flying, that was funded by private exploration companies, in certain infill blocks within the survey area. These infill blocks and data are not part of this data release due to confidentiality agreements. The survey was commissioned by Geoscience Australia as part of the Exploring for the Future (EFTF) program. The EFTF program is led by Geoscience Australia (GA), in collaboration with the Geological Surveys of the Northern Territory, Queensland, South Australia and Western Australia, and is investigating the potential mineral, energy and groundwater resources in northern Australia and South Australia. The EFTF is a four-year $100.5 million investment by the Australian Government in driving the next generation of resource discoveries in northern Australia, boosting economic development across this region. This Data Release Package (Tranche 1, Phase 1) contains the final survey deliverables produced by the contractor CGG, including: (a) the operations and processing report, (b) final processed electromagnetic, magnetic and elevation point located line data, (c) final processed electromagnetic, magnetic and elevation grids, (d) conductivity estimates generated by the EM Flow® conductivity depth imaging algorithm, (e) graphical multiplots of line data and EM Flow® conductivity sections, (f) graphical stacked EM Flow® conductivity sections, (h) ESRI shapefiles containing the flight line locations. Future data release packages will contain data flown after October 7 2017 (Tranche 2, etc.) and further derived products (Phase 2, etc.).

Exploring for the Future AusAEM Eastern Resources Corridor: 2021 Airborne Electromagnetic Survey: TEMPEST® airborne electromagnetic data and GALEI inversion conductivity estimates The accompanying data package, was released on 15 September August 2021 by Geoscience Australia (GA). The package contains AEM data from the AusAEM_20 East Resources Corridor survey, which was acquired across an area spanning from Bedourie in Queensland to Cape Jervis in South Australia, and from Tibooburra in New South Wales to Warrnambool in Victoria. The coverage is more than 600,000 square kilometres of south-eastern Australia. The regional survey was flown at a 20-kilometre nominal line spacing and entailed approximately 31,500 flight-line kilometres f geophysical data. The survey was flown in three phases, by Xcalibur Aviation (Australia) Pty. Ltd. (Xcalibur), formally CGG Aviation (Australia) Pty. Ltd. (CGG), under contract to Geoscience Australia, using the TEMPEST® airborne electromagnetic system. Xcalibur Aviation also processed the data. Geoscience Australia commissioned the Exploring for the Future AusAEM Eastern Resources Corridor survey as part of the Exploring for the Future (EFTF) program. The Exploring for the Future AusAEM program has been expanded with funding from the Geological Surveys of Western Australia and Queensland. Geoscience Australia acknowledges the valuable in-kind support from all Australian state and territory geological surveys in driving the new national AusAEM dataset. The program is designed to investigate the potential mineral, energy and groundwater resources of Australia driving the next generation of resource discoveries. GA managed the survey data acquisition, processing, contract, the quality control of the survey and generating two of the three inversion products included in the data package. The data release package comntains 1. A data release package summary PDF document. 2. The survey logistics and processing report and TEMPEST® system specification files 3. ESRI shape files for flight lines 4. Final processed point located line data in ASEG-GDF2 format 5. Conductivity estimates generated by Xcalibur, EMFlow conductivty-depth transform -point located line data output from the inversion in ASEG-GDF2 format -graphical (PDF) multiplot conductivity sections and profiles for each flight line -Grids generated from CGG's inversion conductivty-depth transform in ER Mapper® format (layer conductivities) 6. Conductivity estimates generated by Geoscience Australia's inversion -point located line data output from the inversion in ASEG-GDF2 format -graphical (PDF) multiplot conductivity sections and profiles for each flight line -GoCAD™ S-Grid 3D objects (suitable for various 3D packages)