<div>Near-surface magnetizations are ubiquitous across many areas of Australia and complicate reliable estimation of depth to deeper magnetizations. We have selected four test areas in which we use equivalent source dipoles to represent and quantify the near-surface magnetizations. We present a synthetic modelling study that demonstrates that field variations from the near-surface magnetizations substantially degrade estimation of depth to a magnetization 500 metres below the modelled sensor elevation and that these problems persist even for anomalies with significantly higher amplitudes. However, preferential attenuation of the fields from near surface magnetizations by upward continuation proved quite effective in improving estimation of depth to those magnetizations.</div> This Abstract was submitted/presented at the 2023 Australasian Exploration Geoscience Conference (AEGC) 13-18 March (https://2023.aegc.com.au/)

<div>This document defines the technical standards set by Geoscience Australia for the acquisition, processing and supply of airborne magnetic, horizontal magnetic gradient and radiometric (gamma-ray spectrometric) data. The technical standards cover the requirements for equipment, calibrations, quality control checks, reporting and data formats for airborne surveys.</div><div><br></div><div><br></div><div><strong>Table of Contents</strong></div><div><br></div><div>Attachment 1A – Data Acquisition and Processing</div><div><br></div><div>1 Aircraft</div><div>2 Flight and Tie Lines</div><div>3 Global Navigation Satellite System (GNSS)</div><div>4 Parallax Correction</div><div>5 Altimeter</div><div>6 Barometer</div><div>7 Digital Elevation Model</div><div>8 Magnetic System Equipment</div><div>9 Magnetic Gradient System Equipment</div><div>10 Magnetic / Gradient Calibration and Quality Tolerances</div><div>11 Magnetic Base Station (Diurnal Monitoring)</div><div>12 Magnetic Data Reduction</div><div>13 Magnetic Gradient Data Reduction</div><div>14 Radiometric System Equipment</div><div>15 Radiometric Calibration and Quality Tolerances</div><div>16 Radiometric Data Reduction</div><div><br></div><div>Attachment 1B – Reporting and Data Supply</div><div><br></div><div>1 General</div><div>2 Calibration Report</div><div>3 Daily Acquisition Report</div><div>4 Weekly Acquisition Report</div><div>5 Operations and Processing Summary Report</div><div>6 Supply Schedule</div><div><br></div><div>Attachment 1C – Data Formats</div><div><br></div><div>1 General</div><div>2 Point-Located Data Files</div><div>3 Definition Files</div><div>4 Description Files</div><div>5 Raw-Edited Magnetic Data File</div><div>6 Reduced Magnetic Data File</div><div>7 Diurnal Magnetic Data File</div><div>8 Raw-Edited Magnetic Gradient Data File</div><div>9 Reduced Magnetic Gradiometry Data File</div><div>10 Raw-Edited Radiometric Data File</div><div>11 Reduced Radiometric Data File</div><div>12 Gridded Data Files</div><div>13 Image Enhanced GeoTIFF Files

<div>This report contains information about the operation of Geoscience Australia’s ten permanent geomagnetic observatories, repeat stations and other relevant information covering the period from 2017 to 2021.</div><div>Information regarding the activities and services of Geoscience Australia’s Geomagnetism program, distribution of geomagnetic data, geomagnetic instrumentation and data processing procedures is also provided.</div><div><br></div>

<div>Geoscience Australia’s Exploring for the Future program 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. This work contributes to building a better understanding of the Australian continent, whilst giving the Australian public the tools they need to help them make informed decisions in their areas of interest.</div><div><br></div><div>As part of the Australia's Resources Framework Project, in the Exploring for the Future Program, Geoscience Australia and CSIRO undertook a magnetic source depth study across four areas, with the objectives of generating cover model constraints from magnetic modelling to expand national coverage, and to improve our subsurface understanding of these areas. During this study, 2005 magnetic estimates of depth to the top of magnetization were generated, with solutions derived using a consistent methodology (targeted magnetic inversion modelling, or TMIM; also known as ‘sweet-spot’ modelling). The methodology for these estimates are detailed in a summary report by Foss et al (2024), and is available for download through Geoscience Australia’s enterprise catalogue (https://pid.geoscience.gov.au/dataset/ga/149239). </div><div><br></div><div>The new points were generated over four areas: 1) the western part of Tasmania that is the southernmost extension of the Darling-Curnamona-Delamerian (DCD) project area; 2) northeastern Queensland; 3) the Officer Basin area of western South Australia and southeastern West Australia; and 4) the Eastern Resources Corridor (ERC), covering eastern South Australia, southwest Queensland, western New South Wales and western Victoria. These depth estimates have been released, together with a summary report detailing the data and methodology used to generate the results, through Geoscience Australia's product catalogue (ecat) at https://pid.geoscience.gov.au/dataset/ga/149239.</div><div><br></div><div>This supplementary data release contains the chronostratigraphic attribution of the new TMIM magnetic depth estimates, which range in depth from at surface to 13,294 m below ground. To ensure that the interpretations took into account the local geological features, the magnetic depth estimates were integrated and interpreted with other geological and geophysical datasets, including borehole stratigraphic logs, potential fields images, surface and solid geology maps, and airborne electromagnetic interpretations (where available). </div><div><br></div><div>Each depth-solution is interpretively ascribed to either a chronostratigraphic boundary with the stratigraphic units above and below the depth estimate, or the stratigraphic unit that the depth estimate occurs within, populated from the Australian Stratigraphic Units Database (ASUD). Stratigraphic attribution adds value and informs users of the depth to certain stratigraphic units in their areas of interest. Each solution is accompanied by confidence estimates. The depth estimate points are formatted for compliance with Geoscience Australia’s (GA) Estimates of Geological and Geophysical Surfaces (EGGS) database, the national repository for standardised depth estimate points. </div><div><br></div><div>Results from these interpretations provided some support to stratigraphic drillhole targeting, as part of the Delamerian Margins NSW National Drilling Initiative campaign, a collaboration between GA’s EFTF program, the MinEx CRC National Drilling Initiative and the Geological Survey of New South Wales. The magnetic depth-estimate solutions produced within this study provide important depth constraints in data-poor areas. These data help to construct a better understanding of the 3D geometry of the Australian continent and aid in cover thickness modelling activities. The availability of the depth-estimate solutions via the EGGS database through Geoscience Australia’s Portal creates enduring value to the public.</div>

Survey Name: East Tasmania Datasets Acquired: Magnetics, Radiometrics and Elevation Geoscience Australia Project Number: P5020 Acquisition Start Date: 20/03/2022 Acquisition End Date: 23/06/2022 Flight line spacing: 200 m Flight line direction: East-West (090-270) Total distance flown: 57,709 line-km's Nominal terrain clearance: 80 m Data Acquisition: Magspec Airborne Surveys Pty Ltd Project Management: Geoscience Australia Quality Control: Geoscience Australia Dataset Ownership: Geoscience Australia and Mineral Resources Tasmania Datum: Geocentric Datum of Australia 2020 (GDA2020) Projection: Map Grid of Australia 55 (MGA55) Included in this release: 1. Point-located Data - ASCII-column (.dat) or NetCDF (.nc) format. • Magnetic diurnal; • Magnetics raw-edited; • Magnetics reduced; • Radiometrics raw-edited; • Radiometrics reduced. 2. Gridded data - ERMapper (.ers) format. • Total magnetic intensity (TMI); • TMI reduced to pole (RTP); • TMI RTP with first vertical derivative (1VD) applied; • Dose rate (with NASVD and standard processing); • Potassium concentration (with NASVD, standard processing); • Thorium concentration (with NASVD, standard processing); • Uranium concentration (with NASVD, standard processing); • Radar-derived digital elevation model (geoidal). 3. Reports. • Calibration report; • Operations and processing summary report. © Commonwealth of Australia (Geoscience Australia) and Mineral Resources Tasmania, Government of Tasmania 2022. With the exception of the Commonwealth Coat of Arms and where otherwise noted, this product is provided under a Creative Commons Attribution 4.0 International Licence (http://creativecommons.org/licenses/by/4.0/legalcode).

Geoscience Australia is the custodian of the most comprehensive publicly available Australian airborne magnetic, gamma-ray, seismic, electromagnetic and gravity data sets. The airborne geophysics data set contains approximately 34 million line kilometres of data, which, at current prices, would cost approximately $197 million to acquire. The gravity data set contains more than 1.57 million reliable onshore stations gathered during more than 1800 surveys. The collection also includes a large number of seismic surveys from Australia's offshore basins. The onshore component of this data set was previously approved for RDSI for 8 TB. This proposal extends the collection to 150TB. The data types and access methods for the Offshore and Onshore data are identical Certain holdings are additionally hosted at the NCI (see downloads)

<div>Geoscience Australia (GA), in collaboration with the New South Wales (NSW) Government’s Geological Survey of NSW, undertook a horizontal magnetic gradient and radiometric survey in the Yathong area of NSW. This survey was fully funded by the NSW Government as part of a project to find deep groundwater for use in times of drought.</div><div><br></div><div>Survey Name: Yathong</div><div>Datasets Acquired: Horizontal Magnetic Gradient, Radiometrics, and Elevation</div><div>Geoscience Australia Project Number: P5023</div><div>Acquisition Start Date: 21/05/2023</div><div>Acquisition End Date: 14/09/2023</div><div>Flight line spacing: 200 m</div><div>Flight line direction: East-West (090-270 degrees)</div><div>Total distance flown: 65,503.75 line-km's</div><div>Nominal terrain clearance: 80 m</div><div>Data Acquisition: Magspec Airborne Surveys Pty Ltd</div><div>Project Management: Geoscience Australia</div><div>Quality Control: Geoscience Australia</div><div>Dataset Ownership: Geological Survey of New South Wales</div><div>Datum: Geocentric Datum of Australia 2020 (GDA2020)</div><div>Projection: Map Grid of Australia Zone 55 (MGA55)</div><div><br></div><div>Included in this release:</div><div><br></div><div>1. Point-located Data - ASCII-column (.dat) and NetCDF (.nc) format.</div><div>• Magnetic diurnal;</div><div>• Magnetic gradient raw-edited;</div><div>• Magnetic gradient reduced;</div><div>• Radiometrics raw-edited;</div><div>• Radiometrics reduced.</div><div><br></div><div>2. Gridded data - ERMapper (.ers) format.</div><div>• Gradient enhanced Total Magnetic Intensity (TMI);</div><div>• Gradient enhanced TMI Reduced to Pole (RTP);</div><div>• Gradient enhanced TMI RTP with First Vertical Derivative (1VD);</div><div>• Dose rate (with NASVD and standard processing);</div><div>• Potassium concentration (with NASVD, standard processing);</div><div>• Thorium concentration (with NASVD, standard processing);</div><div>• Uranium concentration (with NASVD, standard processing);</div><div>• Radar-derived digital elevation model (geoidal).</div><div><br></div><div>3. Reports.</div><div>• Calibration report;</div><div>• Operations and processing summary report.</div>

<p>The Exploring for the Future (EFTF) initiative aims to reduce the technical risk of mineral exploration by providing pre-competitive data and information to support investment and mineral exploration in northern Australia – a key part of ensuring Australia's future economic prosperity. <p>To support the EFTF initiative, the presence of hydrothermal alteration systems associated with iron oxide copper-gold (IOCG) deposits were estimated throughout the Tennant Creek -– Mt Isa Project area of northern Australia. These zones are of economic interest due to their potential to host copper, gold, uranium and rare earth element mineralisation. <p>To predict the presence of IOCG-related alteration, gravity and magnetic intensity data were used to produce 3D models of density and magnetic susceptibility, respectively. The inversion models provide an indication of the volume and distribution of these physical properties within the subsurface and were used to define volumes with relatively high densities and high magnetic susceptibilities as proxies for magnetite-rich alteration and volumes with high density, but low magnetic susceptibility, as proxies for hematite-rich alteration. <p>Contact zones between these two sets of volumes are considered to be the most favourable areas for potential IOCG mineralisation. However, the inversion modelling inevitably will have mapped a number of ‘false positives’, which will require more detailed inversion modelling and/or other data sets to discriminate these from true IOCG-related alteration.

<div>As part of the Australia's Resources Framework Project, in the Exploring for the Future Program, Geoscience Australia and CSIRO have undertaken a magnetic source depth study across four areas. These are: 1) the western part of Tasmania that is the southernmost extension of the Darling-Curnamona-Delamerian (DCD) project area; 2) northeastern Queensland; 3) the Officer Basin area of western South Australia and southeastern West Australia; and 4) the 'Eastern Resources Corridor' (ERC) covering eastern South Australia, southwest Queensland, western New South Wales and western Victoria. This study has produced 2005 magnetic estimates of depth to the top of magnetization. The solutions are derived by a consistent methodology (targeted magnetic inversion modelling, or TMIM; also known as ‘sweet-spot’ modelling). </div><div><br></div><div>The magnetic depth estimates produced as part of this study provide depth constraints in data-poor areas. They help to construct a better understanding of the 3D geometry of the Australian continent, and aid cover thickness modelling activities. </div><div><br></div><div>A supplementary interpretation data release is also available through Geoscience Australia's enterprise catalogue (ecat) at https://pid.geoscience.gov.au/dataset/ga/149499.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program 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. This work contributes to building a better understanding of the Australian continent, whilst giving the Australian public the tools they need to help them make informed decisions in their areas of interest.</div>

<div>In July 2022 an airborne electromagnetic (AEM) survey was flown over and around the proposed site of the National Radioactive Waste Management Facility near the township of Kimba in South Australia.&nbsp;The survey was commissioned by the Australian Radioactive Waste Agency, and was project managed by Geoscience Australia. The survey has Geoscience Australia airborne survey project number P5008.</div><div><br></div><div>The survey was flown by Skytem Australia Pty Ltd using its SkyTEM312Fast AEM system.&nbsp;The survey was conducted on east-west lines at 500 m spacing, with a smaller central focus area of 100 m spaced lines, acquiring a total of 2,545 line kilometres of data. Skytem Australia Pty Ltd also processed the data.</div><div><br></div><div>This data package includes the acquisition and processing report, the final processed AEM data and the results of the 1D laterally constrained inversion of the data to conductivity-depth estimates that was carried out by the contractor.</div>