Orogenic gold deposits provide a significant source of the world’s gold, but their depth of formation is contentious. One hypothesis is that orogenic gold deposits formed along crustal faults over a wide range of depths spanning sub-greenschist to granulite facies. Other authors suggest that the source is restricted to a smaller range of crustal depths (~20-30 km) and temperatures (~550⁰C) that correspond to the transition from greenschist to amphibolite metamorphic facies. Rapid burial of C and S-rich oceanic sediments and amphibolite-grade metamorphism leads to the production of large amounts of fluid in a short amount of time. In order to help discriminate between these competing hypotheses, we compiled thirty years of magnetotelluric (MT) and geomagnetic depth sounding (GDS) data across western Victoria and south-eastern South Australia. This region contains one of the world’s foremost and largest orogenic gold regions that has produced 2% of historic worldwide gold production. Three-dimensional inversion of the MT and GDS data shows a remarkable correlation between orogenic gold deposits with >1 t production and a <20 ohm.m low-resistivity region at crustal depths >20 km. Such depths are at the pressures and temperatures of greenschist to amphibolite-grade metamorphism that releases HS- ligands for Au from C and pyrite (FeS2) rich sediment interbedded with mafic oceanic rocks. Carbon is then precipitated through retrograde hydration reactions with CO2 precipitating as conductive flake graphite. Thus, our model indicates that orogenic gold in western Victoria is most likely sourced from C and FeS2 rich oceanic sediments at amphibolite-grade facies. Citation: Heinson, G., Duan, J., Kirkby, A. et al. Lower crustal resistivity signature of an orogenic gold system. Sci Rep 11, 15807 (2021). https://doi.org/10.1038/s41598-021-94531-8

This set of explanatory notes provided the process of creating the 2019 National Gravity Grids released September 2020. This information provides a step by step guide to the processing sequence undertaken. The Notes provide: 1) the data sources for the grids, such as Geoscience Australia's National Airborne Geophysics Database (NAGD), the Australian National Gravity Database (ANGD), and Sandwell and Smith (v28p1) satellite gravity data. 2) Equations used to reduce gravity, gridding calculations, and observation surface for the "B" series grids, 3) Step by step processing sequence. There is also a section with a simple aid to interpreting the grids. The grids are available either as a complete set of grids, or individually, from the associated link. Links: https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/133023

Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. These line dataset from the GA302 Capel and Faust Basins MSS survey were acquired in 2006 for Geoscience Australia. This survey acquired a range of pre-competitive geological and geophysical data that included seismic reflection, gravity, magnetic and swath bathymetry measurements, as well as seafloor dredge samples.

<p>The Barkly 2D Seismic Survey was acquired during September to November 2019 and commenced near the town of Camooweal on the border of Queensland and Northern Territory. This project is a collaboration between Geoscience Australia (GA) and the Northern Territory Geological Survey (NTGS), and was funded by the Australian Government's Exploring for the Future program and the Northern Territory Geological Survey under Northern Resourcing the Territory initiative. <p>The Barkly seismic survey extends the 2017 South Nicholson seismic survey and links with the existing Beetaloo Sub-basin seismic data. The total length of acquisition was 812.6 km spread over five lines 19GA-B1 (434.6 km), 19GA-B2 (45.9 km), 19GA-B3 (66.9 km), 19GA-B4 (225.8 km) and 19GA-B5 (39.4 km). The Barkly seismic project provides better coverage and quality of fundamental geophysical data over the region from the southern McArthur Basin to northern Mt Isa western succession. The Barkly seismic data will assist in improving the understanding of basins and basement structures and also the energy, mineral and groundwater resource potential in Northern Australia. The new reflection seismic data and derivative information will reduce the risk for exploration companies in this underexplored area by providing information for industry to confidently invest in exploration activities. <b>Raw data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 132890</b>

The discovery of strategically located salt structures, which meet the requirements for geological storage of hydrogen, is crucial to meeting Australia’s ambitions to become a major hydrogen producer, user and exporter. The use of the AusAEM airborne electromagnetic (AEM) survey’s conductivity sections, integrated with multidisciplinary geoscientific datasets, provides an excellent tool for investigating the near-surface effects of salt-related structures, and contributes to assessment of their potential for underground geological hydrogen storage. Currently known salt in the Canning Basin includes the Mallowa and Minjoo salt units. The Mallowa Salt is 600-800 m thick over an area of 150 × 200 km, where it lies within the depth range prospective for hydrogen storage (500-1800 m below surface), whereas the underlying Minjoo Salt is generally less than 100 m thick within its much smaller prospective depth zone. The modelled AEM sections penetrate to ~500 m from the surface, however, the salt rarely reaches this level. We therefore investigate the shallow stratigraphy of the AEM sections for evidence of the presence of underlying salt or for the influence of salt movement evident by disruption of near-surface electrically conductive horizons. These horizons occur in several stratigraphic units, mainly of Carboniferous to Cretaceous age. Only a few examples of localised folding/faulting have been noted in the shallow conductive stratigraphy that have potentially formed above isolated salt domes. Distinct zones of disruption within the shallow conductive stratigraphy generally occur along the margins of the present-day salt depocentre, resulting from dissolution and movement of salt during several stages. This study demonstrates the potential AEM has to assist in mapping salt-related structures, with implications for geological storage of hydrogen. In addition, this study produces a regional near-surface multilayered chronostratigraphic interpretation, which contributes to constructing a 3D national geological architecture, in support of environmental management, hazard mapping and resource exploration. <b>Citation: </b>Connors K. A., Wong S. C. T., Vilhena J. F. M., Rees S. W. & Feitz A. J., 2022. Canning Basin AusAEM interpretation: multilayered chronostratigraphic mapping and investigating hydrogen storage potential. In: Czarnota, K (ed.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, https://dx.doi.org/10.26186/146376

Gravity data measures small changes in gravity due to changes in the density of rocks beneath the Earth's surface. The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. These line dataset from the GA310 South West Margin 2D MSS survey were acquired for Geoscience Australia in 2008/2009 as part of the Australian Government's Offshore Energy Security Program. This survey acquired a range of pre-competitive geological and geophysical data that included seismic reflection, gravity, magnetic and swath bathymetry measurements, as well as seafloor dredge samples. A total of 26,000 line-kilometres of magnetic and gravity data were acquired during this survey.

Geoscience Australia commissioned reprocessing of selected legacy onshore 2D reflection seismic data in the Kidson Sub-basin of the Canning Basin, Cobb Embayment in the SE Canning Basin, NW Canning Basin, and Southern Carnarvon, Western Australia. This reprocessing is a collaboration between the Geoscience Australia Exploring for the Future (EFTF) program and The Government of Western Australia, Department of Mines, Industry Regulation and Safety, Exploration Incentive Scheme (EIS). Reprocessing was carried out by Ion (Cairo) between January 2018 and September 2018. The Canning project comprised 30 lines from 5 vintages of data totalling 1412 km. The Carnarvon project comprised 36 lines from 6 vintages of data totalling 1440 km. This reprocessing is intended to produce an improved quality seismic dataset that will increase confidence in the mapping of the structure and stratigraphy of the onshore sedimentary basins of Western Australia. The new seismic reprocessed data is being made available as pre-competitive information to assist industry to better target areas likely to contain the next major oil, gas and mineral deposits. <b>Processed data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 144258</b>

Geoscience Australia commissioned reprocessing of selected legacy 2D seismic data in the East Kimberley, onshore Bonaparte Basin as part of the Exploring for the Future (EFTF) program. Reprocessing of these data occurred between September 2017 and May 2018. Exploring for the Future (<a href="https://www.ga.gov.au/eftf/">https://www.ga.gov.au/eftf</a>) was a $100.5 million four-year (2016-20), Australian Government-funded program to provide a holistic picture of the potential mineral, energy and groundwater resources in northern Australia. The program has delivered new geoscience data, knowledge and decision support tools to support increased industry investment and sustainable economic development across the north. Groundwater is a critical resource that accounts for most water used across northern Australia. The groundwater component of the EFTF program focused on addressing groundwater resource knowledge gaps, to support future opportunities for economic development via irrigated agriculture, extractive industries and increased security of community water supplies. Through collaboration with State and Territory partners, the program undertook targeted regional investigations of groundwater systems and assessments of groundwater potential more broadly across the region. The program's activities, implemented by Geoscience Australia, involved application of innovative geoscience tools to collect, integrate and analyse a range of data. It includes geological and hydrogeological data, airborne and ground-based geophysical and hydrogeochemical surveys, remote sensing data as well as stratigraphic drilling. The new data and better understanding of groundwater systems also helps inform decision making about groundwater use to protect environmental and cultural assets. These outcomes strengthen investor confidence in resources and agricultural projects by de-risking groundwater in northern Australia. The package contains reprocessed data from ten surveys acquired between 1980 and 1997. In total 53 lines were reprocessed covering a fold area of approximately 618.9 line kilometres, with the objective to produce a modern industry standard 2D land seismic reflection dataset where possible from a selection of multiple legacy 2D data. The purpose of the reprocessing was twofold: 1) To image the near surface structural and stratigraphic configuration for linking to AEM data that is available in the Bonaparte Basin; and 2) To image the structure and stratigraphic architecture of the Paleozoic Bonaparte Basin. The dataset exhibits significant improvements in stack response in most of the reprocessed lines when final and legacy stacks were compared, especially in the shallow section. Optimum results were obtained from the noise attenuation workflows. A minimum processing flow was applied to BWA80, BWA81, and line BNT87-404 lines to avoid any signal leakage throughout the processing. Final data were delivered as minimum phase (care should be taken not to interpret zero crossings as geological boundaries), and final velocities produced a good match with the well checkshot velocities. The processing report from Down Under Geophysics is available for download with this release. Raw and processed data are available on request from <a href="mailto:clientservices@ga.gov.au&body=Ref: eCat 135578">clientservices@ga.gov.au</a> - Quote eCat# 135578. Processed stack SEG-Y files and ancillary data are available for download from this web page.

<p>Eight hundred and seventy two km of gravity and deep crustal reflection data were collected for the Kidson Sub-Basin 2D seismic survey along a single transect: 18GA-KB1 during June to August 2018. <p>The purpose of the survey was to image basin and basement structures of the Kidson Sub-Basin of the onshore Canning Basin, and extending across the Paterson Orogen and on to the eastern margin of the Pilbara Craton. <p>The new data will help geological interpretations to determine the stratigraphy, lateral extent and stratigraphic relationships of the basin and adjoining terranes, and an assessment of the region for its oil and gas and mineral potential. <p>The project is a collaboration between Geoscience Australia (GA) and the Geological Survey of Western Australia (GSWA) and was funded by the Australian Government's Exploring for the Future program and the Western Australian Government's Exploration Incentive Scheme (EIS). <p>Raw data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 128284

<p>The accompanying data package, was released on 30 April 2020 by the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA). <p>The package contains processed data from the “MinEx CRC Cobar Airborne Electromagnetic Survey” that was flown over the Cobar–Lake Cargelligo area of Central West New South Wales . The regional survey was flown at 2.5 and 5 km nominal line spacings and entails approximately 5,900 line kilometres of new geophysical data. The survey was flown in 2019 by New Resolution Geophysics Pty. Ltd. (NRG) using the XCITE® airborne electromagnetic system. NRG also processed the data. <p>The survey also included a further 800 line kilometres of infill flying that was funded by private exploration companies, in certain blocks within the survey area. The data from these infill blocks are not part of this data release due to confidentiality agreements but will be released to the public after a 12 month moratorium. <p>GSNSW commissioned the survey as part of the MinEx Cooperative Research Centre’s (MinEx CRC), the world’s largest mineral exploration collaboration. It brings together industry, government, research organisations and universities to further our understanding of geology, mineral deposits and groundwater resources in areas where rocks aren’t exposed at Earth’s surface. GSNSW is a major participant in the NDI program, committing $16 million to the program over 10 years. In NSW, the program focuses on five areas in the state’s central and far west, where metallic minerals potentially exist under a layer of younger barren geology. These areas are North Cobar, South Cobar, Broken Hill (Mundi), Forbes and Dubbo. <p>GA managed the survey data acquisition and processing contract and the quality control of the survey on behalf of GSNSW. GA also contributed by generating one of the two inversion products included in the data package. <p>The data release package comntains <p>1. A data release package summary PDF document. <p>2. The survey logistics and processing report and XCITE® system specification files <p>3. ESRI shape files for the flight lines and boundary <p>4. KML (Google Earth) files of the flight lines <p>5. Final processed point located line data in ASEG-GDF2 format -final processed dB/dt electromagnetic, magnetic and elevation data -final processed BField electromagnetic, magnetic and elevation data <p>6. Conductivity estimates generated by NRG’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 -graphical (JPEG) conductivity sections for each line -georeferenced (PNG) conductivity sections (suitable for pseudo-3D display in a 2D GIS) -GoCAD™ S-Grid 3D objects (suitable for various 3D packages) -Curtain image conductivity sections (suitable 3D display in GA’s EarthSci) -Grids generated from the NRG inversion in ER Mapper® format (layer conductivities, depth slices, elevation slices) -Images generated from the grids above (layer conductivities, depth slices, elevation slices) <p>7. Conductivity estimates generated by Geoscience Australia's inversion -point located line data output from the inversion in ASEG-GDF2 format -graphical (JPEG) conductivity sections for each line -georeferenced (PNG) conductivity sections (suitable for pseudo-3D display in a 2D GIS) -GoCAD™ S-Grid 3D objects (suitable for various 3D packages) -Curtain image conductivity sections (suitable 3D display in GA’s EarthSci) -Grids generated from Geoscience Australia's inversion in ER Mapper® format (layer conductivities, depth slices, elevation slices) -Images generated from the grids above (layer conductivities, depth slices, elevation slices) <p>Directory structure <p>├── report <p>│   ├── line_data <p>│   ├── shapefiles <p>│   ├── kml <p>│   ├── contractor_inversion <p>│   │   ├── line_data <p>│   │   ├── multiplots <p>│   │   ├── sections <p>│   │   ├── georeferenced_sections <p>│   │   ├── gocad_sgrids <p>│   │   ├── earthsci <p>│   │   │   └── MinExCRC_Cobar_AEM_Contractor_Regional <p>│   │   ├── images <p>│   │   │   ├── layers <p>│   │   │   ├── depth_slice <p>│   │   │   └── elevation_slice <p>│   │   └── grids <p>│   │   ├── layers <p>│   │   ├── depth_slice <p>│   │   └── elevation_slice <p>│   └── ga_inversion <p>│   ├── line_data <p>│   ├── sections <p>│   ├── georeferenced_sections <p>│   ├── gocad_sgrids <p>│   ├── earthsci <p>│   │   └── MinExCRC_Cobar_AEM_GA-Inversion_Regional <p>│   ├── images <p>│   │   ├── layers <p>│   │   ├── depth_slice <p>│   │   └── elevation_slice <p>│   └── grids <p>│   ├── layers <p>│   ├── depth_slice <p>│   └── elevation_slice