Geoscience Australia contracted an airborne electromagnetic (AEM) survey over the Frome Embayment, South Australia, under the Australian Government's Onshore Energy Security Program. The Frome AEM survey was acquired using the Fugro Airborne Surveys (FAS) TEMPEST fixed wing time-domain electromagnetic (TEM) AEM system. The acquisition and processing of data were carried out by FAS under contract to Geoscience Australia. The Frome AEM survey consists of 32 300 line km, covering a total area of 95 000 km2 and was flown between 19 May and 2 November 2010. The survey was designed to deliver reliable, pre-competitive AEM data and scientific analysis of the energy resource potential of the Frome region of South Australia, including the flanks of the Northern Flinders Ranges, the Frome Embayment, the Olary Ranges and the northwestern Murray Basin. The survey data may also be used as an input to groundwater studies in the region. This presentation was given at a Frome AEM Workshop in Adelaide - November 2011.

Identification of groundwater-dependent (terrestrial) vegetation, and assessment of the relative importance of different water sources to vegetation dynamics commonly involves detailed ecophysiological studies over a number of seasons or years. However, even when groundwater dependence can be quantified, results are often difficult to upscale beyond the plot scale. Consequently, quicker, more regional mapping approaches have been developed. These new approaches utilise advances in computation geoscience, and remote sensing and airborne geophysical technologies. The Darling River Floodplain, western New South Wales, Australia, was selected as the case study area. This semi-arid landscape is subject to long periods of drought followed by extensive flooding. Despite the episodic availability of surface water resources, two native Eucalyptus species, E. camaldulensis (River Red Gum) and E. largiflorens (Black Box) continue to survive in these conditions. Both species have recognised adaptations, include the ability to utilise groundwater resources at depth. A remote sensing methodology was developed to identify those communities potentially dependent on groundwater resources during the recent millennium drought in Australia.

Airborne electromagnetic data (AEM) are used in many and diverse applications such as mineral and energy exploration, groundwater investigations, natural hazard assessment, agriculture, city planning and defence. Unfortunately, many users do not have access to a simple workflow for assessing the quality of the data that they are using. This poster outlines the main quality assurance and quality control (QA-QC) procedures used by Geoscience Australia for our 2008-11 AEM surveys. Minor processing errors can dramatically reduce the quality of the data to the point that interpreters will be unable to use the data, or worse still, will be misled by features or characteristics produced during acquisition and processing. These scenarios not only impact the application at the time of interpretation, but can seriously impact the reputation and perceptions of the AEM industry. Every effort should be made to ensure that maximum fidelity is preserved in the data during acquisition and processing so that the best possible data are available for interpretation. Geoscience Australia is embarking on a project to upgrade the National Airborne Geophysical Database to better manage the data from major AEM surveys. This will better preserve the data and associated documentation to allow users to access and take advantage of the data well into the future. The quality of historical data included in this endeavour will unfortunately be variable and dependent on the QA-QC standards of the time. Geoscience Australia currently holds over 150 000 line kilometres of AEM data funded by the Commonwealth Government, State Governments and industry. Much of this data is available online for download, but is not available via the Geophysical Archive Data Delivery System (GADDS). Geoscience Australia is planning the expansion of GADDS to accommodate AEM data into the future. It is hoped the procedures outlined on the poster will be widely accepted by users, in particular new users, as a set of minimum requirements to help ensure that AEM data will be of a consistent quality and to a higher standard acknowledging it as the valuable resource it is. Key words: Airborne electromagnetic data; National Airborne Geophysical Database; AEM; QA-QC.

Airborne Electromagnetic data are being acquired by Geoscience Australia in areas considered to have potential for uranium or thorium mineralisation under the Australian Government's Onshore Energy Security Program (OESP). The surveys have been managed and interpreted by Geoscience Australia's Airborne Electromagnetic Acquisition and Interpretation project. In contrast to industry style deposit scale investigations, these surveys are designed to reveal new geological information at regional scale. The Pine Creek airborne electromagnetic survey comprised of three survey areas Woolner Granite, Rum Jungle and Kombolgie. Tempest data were acquired for Woolner Granite and Rum Jungle survey areas and are included in this report. Woolner Granite and Rum Jungle survey areas cover a total of 21 100 line km and an area of 43 200 km2. Phase-1 data, that is, contractor quality-controlled and quality-assessed data for Woolner Granite, Rum Jungle and Kombolgie, were released during 2009. Phase-2 data, that is Geoscience Australia layered earth inversion (GA-LEI) data and derived products for Woolner Granite and Rum Jungle, are included in this data release. The data and products described in this report are contained on the accompanying DVD. The Kombolgie survey data were acquired with VTEM. The VTEM Kombolgie inversion data and report will be included in a separate data release. The main products from the AEM surveys are conductivity depth slices and sections, conductance grids and an AEM Depth of Investigation grid. The data is provided in formats which can be viewed on most computers systems. They include, JPEG (.jpg) with associated world files for easy use in geographic information system (GIS) packages, ER Mapper grids (.ers), ESRI shape files (.shp) of the flight path, and point-located ASCII data with relevant metadata for derived products.

Data from a VTEM airborne electromagnetic survey over resistive terrain is examined. Forward modelling and analysis of high-altitude lines shows that the amplitudes of random noise, bucking error, processing corrections and geological signals can be large compared to the geological signal in the resistive terrain. The negative impacts of the low geological signal to noise ratio on conductivity estimates generated by layered-earth inversion and conductivity transformations are demonstrated. The reader is alerted to the degree of uncertainty and non-uniqueness that is inherent in conductivity estimates generated from similar datasets.

Geoscience Australia (GA) has recently released regional AEM data in two survey areas of the Pine Creek region. The Woolner Granite-Rum Jungle survey in the western part of the region was flown using TEMPESTTM and the Kombolgie survey in the eastern part was flown using VTEMTM. These data assist mapping shallow subsurface geological features for mineral explorations including uranium. Conductivity estimates derived for the Woolner-Rum Jungle surveys using GA's Layered Earth Inversion (GA-LEI) algorithm reveal several unconformities and conductors in sedimentary sequences interpreted mostly within the top 300-400 m of the crust, including: 1. The Depot Creek unconformity over the Paleoproteroic Pine Creek Orogen and Archean. A 3D model derived from these data shows the geometry and lateral extent of part of the Depot Creek unconformity with a clarity previously not available; 2. Strong conductors of carbonaceous and pyritic materials in the South Alligator River Group and Mt Partridge Group, 3. Moderate to week conductors revealed in the sedimentary sequences of the Birrindudu, Daly and Bonaparte Basins, and 4. Faults and folds. EM FlowTM (Version 5.23-13) sections from the Kombolgie survey not only map the Kombolgie unconformity over the Pine Creek Orogen and Archean and other conductors in the Katherine River Group, but also map conductors in pre-Kombolgie basement to a depth up to 2 km. Penetration to this depth represents a major breakthrough in AEM survey capability, achieved in part due to the extremely resistive rocks in the area. Geological cross-section interpretations based on conductivity images also incorporate available drill hole data to help improve section reliability. The implications of these AEM data for uranium and gold mineral systems in the Pine Creek region are discussed in the companion paper by Jaireth et al. (this volume).

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>The Southern Thomson Orogen VTEMplus® 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 VTEMplus® 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. <p>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: <p>1. A regular regional survey on 5000 m spaced east-west flight lines totalling 3352 line km and covering an area of 16 261 km2. <p>2. Two regional traverses adjacent to roads totalling 915 line km. <p>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. <p>Previously Released Data (Phase 1) <p>In August 2014 the processed data from the Southern Thomson Orogen VTEMplus® AEM Survey were released in the Phase 1 data release package that is available free of charge from Geoscience Australia's web site (see https://pid.geoscience.gov.au/dataset/ga/81852). The Phase 1 package includes the final processed electromagnetic data, waveform files, multiplots, conductivity estimates from the EM Flow® conductivity depth imaging algorithm, and an operations and processing report, all produced by the contractor Geotech Airborne Ltd. <p>Current Release (Phase 2) <p>This Phase 2 data release package contains results from the electromagnetic inversion of the data in the Phase 1 release. The inversion results were generated using two different types of algorithm, a deterministic regularized gradient based algorithm, which we call GALEISBS (Roach, 2010), and a reversible-jump Markov chain Monte Carlo algorithm, which we call GArjMcMC (Brodie and Sambridge, 2012; Brodie and Reid, 2013). Both algorithms assume a layered earth or 1D conductivity structure. Each airborne electromagnetic sounding is inverted independently and the results are then stitched into combined sections. <p>The deterministic GALEISBS inversion products are available for download in four logical parts based on the type of derived product. These are zipped into the following four files: <p>1. galeisbs_point_located_data.zip <p>2. galeisbs_sections.zip <p>3. galeisbs_georeferenced_sections.zip <p>4. galeisbs_gocad_sgrids.zip <p>The stochastic GArjMcMC inversion products are available for download in five logical parts based on the type of derived product. These are zipped into the following five files; <p>1. rjmcmc_point_located_data.zip <p>2. rjmcmc_sections.zip <p>3. rjmcmc_georeferenced_sections.zip <p>4. rjmcmc_gocad_sgrids.zip <p>5. rjmcmc_probability_map_plots.zip

The continuing world demand for potash (potassium salts) is driving a new exploration boom in the Australian minerals industry for this valuable resource, listed by Geoscience Australia (GA) as a strategic commodity (Mernagh 2013). The Food and Agriculture Organization of the United Nations (FAO) predicts a rising demand for fertilizers, with potash demand increasing at 3.7% per annum (FAO 2012), and Rabobank predicts that demand will exceed supply by up to 100% by 2020 (Rabobank 2012). This demand is driving the application of airborne electromagnetics (AEM) to map salinity as a proxy for potential potash resources in salt lakes. This short paper describes a few of the applications and is written in response to an industry request to GA for information on how AEM might be used to explore for potash.

Borehole induction conductivity data, commonly referred to as conductivity logs, were acquired from 20 boreholes in the Frome region of South Australia, during July-August 2010, in support of the Frome airborne electromagnetic (AEM) survey managed by Geoscience Australia (GA). The conductivity logs were used to assist in generating reference models for geophysical inversions of the AEM data, and to provide an independent dataset for assessing the inversion results. The Frome AEM survey was acquired using the Fugro Airborne Surveys (FAS) TEMPEST fixed wing time-domain electromagnetic (TEM) AEM system. The acquisition and processing of data were carried out by FAS under contract to GA. The geophysical investigations were designed to deliver reliable, pre-competitive AEM data and scientific analysis of the energy resource potential of the Frome region of South Australia, including the flanks of the Northern Flinders Ranges, the Frome Embayment, the Olary Ranges and the northwestern Murray Basin. The Frome AEM survey covers a total area of 95,000 km2 and was flown between 22 May and 2 November 2010.