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

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.

The AusAEM1 airborne electromagnetic survey extends 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 (Ley-Cooper et al., 2020). To improve targeting and outcomes for mineral, energy and groundwater exploration, we conducted a regional interpretation of this dataset to characterise the subsurface geology of northern Australia. The interpretation includes the depth to chronostratigraphic surfaces, compilation of stratigraphic relationship information, and delineation of structural and electrically conductive features. In addition to help connecting correlative outcropping units separated by up to hundreds of kilometres, the results led to 3D mapping of palaeovalleys and prompted further investigation of electrical conductors and their relationship to structural features and mineralisation. Approximately 200,000 regional depth point 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. Refer to Wong et al., (2020) for more details on the AusAEM1 interpretation.

<div> A key issue for explorers in Australia is the abundant sedimentary and regolith cover obscuring access to underlying potentially prospective rocks. &nbsp;Multilayered chronostratigraphic interpretation of regional broad line-spaced (~20&nbsp;km) airborne electromagnetic (AEM) conductivity sections have led to breakthroughs in Australia’s near-surface geoscience. &nbsp;A dedicated/systematic workflow has been developed to characterise the thickness of cover and the depth to basement rocks, by delineating contact geometries, and by capturing stratigraphic units, their ages and relationships. &nbsp;Results provide a fundamental geological framework, currently covering 27% of the Australian continent, or approximately 2,085,000&nbsp;km2. &nbsp;Delivery as precompetitive data in various non-proprietary formats and on various platforms ensures that these interpretations represent an enduring and meaningful contribution to academia, government and industry.&nbsp;The outputs support resource exploration, hazard mapping, environmental management, and uncertainty attribution.&nbsp;This work encourages exploration investment, can reduce exploration risks and costs, helps expand search area whilst aiding target identification, and allows users to make well-informed decisions. Presented herein are some key findings from interpretations in potentially prospective, yet in some cases, underexplored regions from around Australia.&nbsp;</div> This abstract was submitted & presented to the 8th International Airborne Electromagnetics Workshop (AEM2023) (https://www.aseg.org.au/news/aem-2023)

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.

<div>The Australian wide airborne electromagnetic programme AusAEM stands as the largest survey of its kind aiming to cover the Australian continent at approximately 20 km line-spacing. It is transforming resource exploration, unveiling potential minerals and groundwater.&nbsp;</div><div><br></div><div>The open-access nature of AusAEM data and the modelling codes developed around it encourages collaboration between governments, industry, and academia, fostering a community focused on advancing geoscientific research and exploration.</div><div><br></div><div>Overall, the AusAEM program is an asset that can drive economic growth, support sustainable resource management, and enhance scientific understanding of Australia’s geological landscape.</div><div><br></div>

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.).

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 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.

<div>The dataset contained in this package and release consists of GA’s Layered-Earth-Inversion (GALEI, Brodie, 2016) conductivity-depth estimates from the AEM data, acquired over several areas of Western Australia, converted into SEG-Y format. The SEG-Y data standard was proposed by the Society of Exploration Geophysicists (SEG) standards committee (see Norris & Faichney 2002). Previously, the AEM data has been released as point located line data in conventional ascii format and is accessible through several of the following associated eCat records (<a href="https://pid.geoscience.gov.au/dataset/ga/146345">146345</a>, <a href="https://pid.geoscience.gov.au/dataset/ga/146042">146042</a>, <a href="https://pid.geoscience.gov.au/dataset/ga/144621">144621</a>, <a href="https://pid.geoscience.gov.au/dataset/ga/145265">145265</a> and <a href="https://pid.geoscience.gov.au/dataset/ga/147688">147688</a>). This SEG-Y data release is expected to benefit users who require the AEM modelled sections in SEG-Y format to assist in their interpretations, investigations and discovery of potential mineral, energy, and groundwater resources within Australia.&nbsp;</div>