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.).

This animation shows how Airborne Electromagnetic Surveys Work. It is part of a series of Field Activity Technique Engagement Animations. The target audience are the communities that are impacted by our data acquisition activities. There is no sound or voice over. The 2D animations include a simplified view of what AEM equipment looks like, what the equipment measures and how the survey works.

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.

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.

This animation shows how Airborne Electromagnetic Surveys Work, when conducted by a rotary wing (helicopter) aircraft. It is part of a series of Field Activity Technique Engagement Animations. The target audience are the communities that are impacted by our data acquisition activities. There is no sound or voice over. The 2D animation includes a simplified view of what AEM equipment looks like, what the equipment measures and how the survey works.

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

<div>In Australia, wide-spread sedimentary basin and regolith cover presents a key challenge to explorers, environmental managers and decision-makers, as it obscures underlying rocks of interest. To address this, a national coverage of airborne electromagnetics (AEM) with a 20&nbsp;km line-spacing is being acquired. This survey is acquired as part of the Exploring for the Future program and in collaboration with state and territory geological surveys. This survey presents an opportunity for regional geological interpretations on the modelled AEM data, helping constrain the characteristics of the near-surface geology beneath the abundant cover, to a depth of up to ~500&nbsp;m.</div><div> The AEM conductivity sections were used to delineate key chronostratigraphic boundaries, e.g. the bases of geological eras, and provide a first-pass interpretation of the subsurface geology. The interpretation was conducted with a high level of data integration with boreholes, potential fields geophysics, seismic, surface geology maps and solid geology maps. This approach led to the construction of well-informed geological interpretations and provided a platform for ongoing quality assurance and quality control of the interpretations and supporting datasets. These interpretations are delivered across various platforms in multidimensional non-proprietary open formats, and have been formatted for direct upload to Geoscience Australia’s (GA) Estimates of Geological and Geophysical Surfaces (EGGS) database, the national repository of multidisciplinary subsurface depth estimates.</div><div> These interpretations have resulted in significant advancements in our understanding of Australia’s near-surface geoscience, by revealing valuable information about the thickness and composition of the extensive cover, as well as the composition, structure and distribution of underlying rocks. Current interpretation coverage is ~110,000 line kilometres of AEM conductivity sections, or an area &gt;2,000,000&nbsp;km2, similar to the area of Greenland or Saudi Arabia. This ongoing work has led to the production of almost 600,000 depth estimate points, each attributed with interpretation-specific metadata. Three-dimensional line work and over 300,000 points are currently available for visualisation, integration and download through the GA Portal, or for download through GA’s eCat electronic catalogue. </div><div> These interpretations demonstrate the benefits of acquiring broadly-spaced AEM surveys. Interpretations derived from these surveys are important in supporting regional environmental management, resource exploration, hazard mapping, and stratigraphic unit certainty quantification. Delivered as precompetitive data, these interpretations provide users in academia, government and industry with a multidisciplinary tool for a wide range of investigations, and as a basis for further geoscientific studies.</div> Abstract submitted and presented at 2023 Australian Earth Science Convention (AESC), Perth WA (https://2023.aegc.com.au/)

<div><strong>Yathong, Forbes, Dubbo, and Coonabarabran Airborne Electromagnetic Survey Blocks.</strong></div><div><br></div><div>Geoscience Australia (GA), in collaboration with the Geological Survey of New South Wales (GNSW), conducted an airborne electromagnetic (AEM) survey from April to June 2023. The survey spanned from the north-eastern end of the Yathong-Ivanhoe Trough and extended across the Forbes, Dubbo, and Coonabarabran regions of New South Wales.&nbsp;A total of 15, 090-line kilometres of new AEM and magnetic geophysical data were acquired. This survey was entirely funded by&nbsp;GSNSW and GA managed acquisition, quality control, processing, modelling, and inversion of the AEM data.</div><div><br></div><div>The survey was flown by Xcalibur Aviation (Australia) Pty Ltd using a 6.25 Hz HELITEM® AEM system. The survey blocks were flown at 2500-metre nominal line spacings, with variations down to 100 metres in the Coonabarabran block. It was flown following East-West line directions. Xcalibur also processed the acquired data. This data package includes the acquisition and processing report, the final processed AEM data, and the results of the contractor's conductivity-depth estimates. The data package also contains the results and derived products from a 1D inversion by Geoscience Australia with its own inversion software.</div><div><br></div><div>The survey will be incorporated and become part of the national AusAEM airborne electromagnetic acquisition program, which aims to provide geophysical information to support investigations of the regional geology and groundwater.</div><div><br></div><div><strong>The data release package contains:</strong></div><div><br></div><div>1. A data release package <strong>summary PDF document</strong></div><div>2. The <strong>survey logistics and processing report</strong> and HELITEM® system specification files</div><div>3. <strong>Final processed point located line data</strong> in ASEG-GDF2 format for the five areas</div><div> -final processed dB/dt electromagnetic, magnetic and elevation data</div><div> -final processed B field electromagnetic, magnetic and elevation data</div><div><strong> <em>Conductivity estimates generated by Xcalibur’s inversion&nbsp;</em></strong></div><div> -point located conductivity-depth line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (PDF) multiplot conductivity stacks and section profiles for each flight line</div><div> -graphical (PNG) conductivity sections for each line</div><div> -grids generated from the Xcalibur’s inversion in ER Mapper® format (layer conductivities slices, DTM, X & Z component for each of the 25 channels, time constants, TMI)</div><div>4.<strong> ESRI shape and KML</strong> (Google Earth) files for the flight lines and boundary</div><div>5<strong>. Conductivity estimates generated by Geoscience Australia's inversion&nbsp;</strong></div><div> -point located line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (pdf) multiplot conductivity sections for each line</div><div> -georeferenced (PNG) conductivity sections (suitable for pseudo-3D display in a 2D GIS)</div><div> -GoCAD™ S-Grid 3D objects (suitable for various 3D packages)</div><div> -Curtain image conductivity sections in log & liner colour stretch (suitable 3D display in GA’s EarthSci)</div><div><br></div><div><strong>Directory structure</strong></div><div>├── <strong>01_Report</strong></div><div>├── <strong>02_XCalibur_delivered</strong></div><div>│&nbsp;&nbsp; ├── * survey_block_Name</div><div>│ ├── cdi</div><div>│ │ ├── sections</div><div>│ │ └── stacks</div><div>│ ├── grids</div><div>│ │ ├── cnd</div><div>│ │ ├── dtm</div><div>│ │ ├── emxbf</div><div>│ │ ├── emxdb</div><div>│ │ ├── emxff</div><div>│ │ ├── emxzbf</div><div>│ │ ├── emzdb</div><div>│ │ ├── time_constant</div><div>│ │ └── tmi</div><div>│ ├── located_data</div><div>│ ├── maps</div><div>│ └── waveform</div><div>│&nbsp;&nbsp; </div><div>├── <strong>03_Shape&kml</strong></div><div>└── <strong>04_GA_Layer_Earth_inversion</strong></div><div> ├── * survey_block_Name</div><div> ├── GA_georef_sections</div><div> │ ├── linear-stretch</div><div> │ └── log-stretch</div><div> ├── GA_Inverted_conductivity_models</div><div> ├── GA_multiplots</div><div> └── GA_sgrids</div><div> </div>

<div>A national compilation of airborne electromagnetic (AEM) conductivity–depth models from AusAEM (Ley-Cooper et al. 2020) survey line data and other surveys (see reference list in the attachments) has been used to train a conductivity model prediction for the 0-4 m and 30 m depth intervals. Over 460,000 training points/measurements were used in a 5 K-Fold training and validation split. A further 28,626 points/measurements were used to assess the out of sample performance (OOS; i.e. points not used in the model validation). Modelling of the conductivity values (i.e. measurements along the AEM survey lines) was performed using the gradient boosted (GB) tree algorithm. The GB model is a machine learning (ML) ensemble technique used for both regression and classification tasks (https://scikit-learn.org/stable/modules/generated/sklearn.ensemble.GradientBoostingRegressor.html). Samples along the flight-line were thinned to approximately one sample per 300 m. This avoided the situation where we could have more than one sample per pixel (i.e. features or covariates used in the model prediction have a cell or pixel size of 80 m) that could otherwise lead to over fitting. In addition, out of sample set used label clusters or groups to minimise overfitting. Here we use the median of the models as the conductivity prediction and the upper and lower percentiles (95th and 5th respectively) to measure the model uncertainty. Grids show conductivity (S/m) in log 10 units. The methodology used to generate these conductivity grids are overall similar to that described by Wilford, et al. 2022.</div><div>&nbsp;</div><div>Reported out-of-sample r-squares for the 0-4 m and 3 m depths are 0.76 and 0.74, respectively. The ML approach allows estimation of conductivity into areas where we do not have airborne electromagnetic survey coverage. Hence these model have a national extent. Where we do not have AEM survey coverage the model is finding relationships with the covariates and making informed estimates of conductivity in those areas. Where those relationships are not well understood (i.e. where we see a departure in the feature space characteristics from what the model can ‘see’) the model prediction is likely to be less certain. Differences in the features and their corresponding values ‘seen’ and used in the model versus the full feature space covering the entire continent are captured in the covariate shift map. High values in the shift model can indicate higher potential uncertainty or unreliability of the model prediction. Users therefore need to be mindful when interpreting this dataset, of the uncertainties shown by the 5th-95th percentiles, and high values in the covariate shift map.</div><div>&nbsp;</div><div>Datasets in this data package include:</div><div>&nbsp;</div><div>1. 0_4m_conductivity_prediction_median.tif</div><div>2. 0_4m_conductivity_lower_percentile_5th.tif</div><div>3. 0_4m_conductivity_upper_percentile_95th.tif</div><div>4. 30m_conductivity_prediction_median.tif</div><div>5.30m_conductivity_lower_percentile_5th.tif</div><div>6. 30m_conductivity_upper_percentile_95th.tif</div><div>7. National_conductivity_model_shift.tif</div><div>8. Full list of referenced AEM survey datasets used to train the model (word document)</div><div>9. Map showing the distribution of training and out-of-sample sites</div><div><br></div><div>All the Geotiffs (1-6) are in log (10) electrical conductivity siemens per metre (S/m).</div><div>&nbsp;</div><div>This work is part of Geoscience Australia’s Exploring for the Future program which provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div><br></div><div><strong>Reference:</strong></div><div><br></div><div>Ley-Cooper, A. Y., Brodie, R.C., and Richardson, M. 2020. AusAEM: Australia’s airborne electromagnetic continental-scale acquisition program, Exploration Geophysics, 51:1, 193-202, DOI: 10.1080/08123985.2019.1694393</div><div><br></div><div>Wilford, J., LeyCooper, Y., Basak, S., Czarnota, K. 2022. High resolution conductivity mapping using regional AEM survey and machine learning. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/146380</div>

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)