Unconformity-type uranium deposits are high-grade and constitute over a third of the world's uranium resources. The Cariewerloo Basin, South Australia, is a region of high prospectivity for unconformity-related uranium as it contains many similarities to an Athabasca-style unconformity deposit. These include features such as Mesoproterozoic red-bed sediments, Paleoproterozoic reduced crystalline basement enriched in uranium (~15-20 ppm) and reactivated basement faults. An airborne electromagnetic (AEM) survey was flown in 2010 using the Fugro TEMPEST system to delineate the unconformity surface at the base of the Pandurra Formation. However highly-conductive regolith attenuated the signal in the northern and eastern regions, requiring application of deeper geophysical methods. In 2012 a magnetotelluric (MT) survey was conducted along a 110 km transect of the north-south trending AEM line. MT data were collected at 29 stations and successfully imaged the depth to basement, and additionally providing evidence for deeper fluid pathways. The AEM data were integrated into the regularisation mesh as a-priori information generating an AEM constrained resistivity model and also correcting for static shift. The AEM constrained resistivity model best resolved resistive structures, allowing strong contrast with conductive zones.

Geoscience Australia (GA) is a leading promoter of airborne electromagnetic (AEM) surveying for regional mapping of cover thickness, under-cover basement geology and sedimentary basin architecture. Geoscience Australia flew three regional AEM surveys during the 2006-2011 Onshore Energy Security Program (OESP): Paterson (Western Australia, 2007-08); Pine Creek-Kombolgie (Northern Territory, 2009); and Frome (South Australia, 2010). Results from these surveys have produced a new understanding of the architecture of critical mineral system elements and mineral prospectivity (for a wide range of commodities) of these regions in the regolith, sedimentary basins and buried basement terrains. The OESP AEM survey data were processed using the National Computational Infrastructure (NCI) at the Australian National University to produce GIS-ready interpretation products and GOCADTM objects. The AEM data link scattered stratigraphic boreholes and seismic lines and allow the extrapolation of these 1D and 2D objects into 3D, often to explorable depths (~ 500 m). These data sets can then be combined with solid geology interpretations to allow researchers in government, industry and academia to build more reliable 3D models of basement geology, unconformities, the depth of weathering, structures, sedimentary facies changes and basin architecture across a wide area. The AEM data can also be used to describe the depth of weathering on unconformity surfaces that affects the geophysical signatures of underlying rocks. A number of 3D models developed at GA interpret the under-cover geology of cratons and mobile zones, the unconformity surfaces between these and the overlying sedimentary basins, and the architecture of those basins. These models are constructed primarily from AEM data using stratigraphic borehole control and show how AEM data can be used to map the cross-over area between surface geological mapping, stratigraphic drilling and seismic reflection mapping. These models can be used by minerals explorers to more confidently explore in areas of shallow to moderate sedimentary basin cover by providing more accurate cover thickness and depth to target information. The impacts of the three OESP AEM surveys are now beginning to be recognised. The success of the Paterson AEM Survey has led to the Geological Survey of Western Australia announcing a series of OESP-style regional AEM surveys for the future, the first of which (the Capricorn Orogen AEM Survey) completed acquisition in January 2014. Several new discoveries have been attributed to the OESP AEM data sets including deposits at Yeneena (copper) and Beadell (copper-lead-zinc) in the Paterson region, Thunderball (uranium) in the Pine Creek region and Farina (copper) in the Frome region. New tenements for uranium, copper and gold have also been announced on the results of these surveys. Regional AEM is now being applied in a joint State and Commonwealth Government initiative between GA, the Geological Survey of Queensland and the Geological Survey of New South Wales to assess the geology and prospectivity of the Southern Thomson Orogen around Hungerford and Eulo. These data will be used to map the depth of the unconformity between the Thomson Orogen rocks and overlying sedimentary basins, interpret the nature of covered basement rocks and provide more reliable cover thickness and depth to target information for explorers in this frontier 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 Southern Thomson Orogen VTEM-plus® Airborne Electromagnetic Survey was conducted by Geoscience Australia as part of a collaborative project with its partners the Geological Survey of New South Wales and the Geological Survey of Queensland. The Survey contributes to the Australian Academy of Science's UNCOVER Initiative and Geoscience Australia's response to this as part of the National Mineral Exploration Strategy. Geoscience Australia contracted Geotech Airborne Ltd to acquire VTEM-plus® airborne electromagnetic (AEM) data over part of the Southern Thomson Orogen in Queensland and New South Wales in April and May 2014. The data were also processed by Geotech Airborne Ltd using its FullWaveForm® processing techniques. The survey is designed to assess the under-cover geology and prospectivity of the Southern Thomson Orogen around Hungerford and Eulo and straddles the New South Wales-Queensland border. The survey comprises two parts: 1. A regular regional survey on 5000 m spaced East-West lines totalling 3352 line km and covering an area of 16 261 km2. 2. Two regional traverses adjacent various roads totalling 915 line km. The Southern Thomson Orogen is a priority area for mineral systems research. Much of the area lies underneath cover of sedimentary basins and is a poorly-understood element of Australia's geology. The Orogen contains Cambro-Ordovician rocks that have potential for Iron Oxide Copper-Gold (IOCG) resources, porphyry copper-gold and Volcanic-Hosted Massive Sulphide (VHMS) deposits. Survey data will add to knowledge of cover thickness and character and will inform future geological mapping in the region. The Southern Thomson Orogen VTEM-plus® AEM Survey data release includes the final contractor supplied (Phase 1) datasets AEM survey. The data will be available from Geoscience Australia's web site free of charge: http://www.ga.gov.au/about/what-we-do/projects/minerals/current/continental-geophysics/airborne-electromagnetics The data release package includes: 1. 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: a. Main survey block Part 1 (flight lines 1000-1171) b. Main survey block Part 2 (flight lines 1180-1360) c. Traverse lines (flight lines 3000-3006 and 4000-4007) d. Repeat lines e. High altitude lines. 2. Waveform files for every flight containing the 192 kHz sampling of the transmitter current and receiver waveforms. 3. 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. These data are in ASCII column format with associated README and ASEG-GDF2 header files. All regular survey, traverses and repeat lines are included in a single download file. 4. 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. 5. 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. 6. Operations Report. 7. ESRI shapefiles and KML files of flight lines. 8. Metadata and License files.

<p>This package contains Airborne Electromagnetic (AEM) data from the “SkyTEM helicopter EM Ord-Keep rivers region” survey which was flown over the Ord-Keep Rivers Region, Western Australia/Northern Territory, Australia during May - June 2017. High resolution magnetics were also acquired during the flights. As shown in Figure 1, the area is located in the 1:250000 map sheets of SD52-14 (Cambridge Gulf), SD52-11 (Port Keats) and SD 52-15 (Auvergne) near the town of Kununurra. 8100 line km of TEM and magnetic data were acquired. The projected grid coordinates have been supplied in GDA94 MGA Zone 52. <p>The aim of the survey is to provide geophysical information to support investigations of the regional groundwater system and identify regional groundwater sources. It will provide data to allow for the modelling of the following at a reconnaissance scale: <p>a) trends in regolith thickness and variability <p>b) variations in bedrock conductivity <p>c) conductivity of key bedrock (lithology related) conductive units under cover <p>d) the groundwater resource potential of the region <p>e) palaeovalley systems known to exist in the region. <p>This report lists the SkyTEM system information and specifications relevant for this survey, and describes the processing carried out on the data. <p>Geoscience Australia commissioned the survey 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 (https://www.ga.gov.au/eftf).

<p>This package contains airborne electromagnetic (AEM) data from the "SkyTEM helicopter EM Howard East region" survey which was flown over Howard East region, Northern Territory during July - August 2017. The area is comprised of 2073.6 line kilometres in total. <p>The aim of the survey is to provide at a reconnaissance scale: <p>a) trends in regolith thickness and variability <p>b) variations in bedrock conductivity <p>c) conductivity of key bedrock (lithology related) conductive units under cover <p>d) the groundwater resource potential of the region <p>This report lists the SkyTEM system information and specifications relevant for this survey, and describes the processing carried out on the data. <p>Geoscience Australia commissioned the survey 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 (https://www.ga.gov.au/eftf).

Ross C Brodie James Reid Monte Carlo Inversion of SkyTEM AEM data from Lake Thetis, Western Australia A SkyTEM airborne electromagnetic dataset was inverted using a 1D reversible jump Markov chain Monte Carlo algorithm. The inversion of each dual-moment sounding generates an ensemble of 300,000 models that fit the data. The algorithm automatically varies the number of layers in the large range of models that are tested. Analysis of the statistical properties of the ensemble yields a wealth of information on the probable conductivity distribution plus the mean, mode, median and most likely summary models. Robust information on the non-uniqueness and uncertainty of the results is also afforded by the ensemble. These are conveyed on conductivity map and section products. Estimates of the probable depths to interfaces are a further outcome. These depth estimates show great potential as an aid for mapping geological surfaces. The resulting conductivity maps and sections are coherent and appear to be geologically realistic on face value. However it is demonstrated with 3D modelling that a plausible hydrogeological interpretation on the sections is likely to be an artefact of 1D inversion of a 3D geological scenario. Key words: Electromagnetic, airborne, inversion, Monte Carlo, uncertainty, 3D.

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.

As part of the Exploring For the Future program 2022 showcase, Geoscience Australia (GA) in collaboration with the Australian Institute of Geoscientists held an Airborne Electromagnetics (AEM) workshop in Perth on 11th August 2022. The workshop comprised the following: - An introduction to GA's 20 km spaced continent-wide AusAEM program, by Karol Czarnota - How the Western Australia government has successfully used 20 km spaced AEM data, by Klaus Gessner - An introduction to AEM, surveying, and quality control given by Yusen Ley-Cooper - An introduction to inverse theory presented by Anandaroop Ray - Hands-on AEM modeling and inversion using HiQGA.jl by Anandaroop Ray - Integrating geophysics and geology in subsurface interpretation, by Sebastian Wong - Avoiding the 10 most common pitfalls in AEM interpretation according to Neil Symington YouTube video from the workshop, as well as data and code to follow along with the videos can be found on GA's GitHub at <a href=https://github.com/GeoscienceAustralia/HiQGA.jl/tree/workshop><u>this link.</u></a>

This package contains airborne electromagnetic (AEM) data from the "SkyTEM helicopter EM Southern Stuart region" survey which was flown over an area between Alice Springs and Tennant Creek, Northern Territory during July - August 2017. The area is comprised of 9666 line km in total. The aim of the survey is to provide at a reconnaissance scale: a) trends in regolith thickness and variability b) variations in bedrock conductivity c) conductivity of key bedrock (lithology related) conductive units under cover d) the groundwater resource potential of the region e) palaeovalley systems known to exist in the region. This report lists the SkyTEM system information and specifications relevant for this survey, and describes the processing carried out on the data. Geoscience Australia commissioned the survey 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 (https://www.ga.gov.au/eftf).