Geoscience Australia in partnership with State and Territory Geological Surveys has applied the magnetotelluric (MT) technique to image Australia’s resistivity structure over the last decade. As part of the Mount Isa Geophysics Initiative program, MT data were collected at 138 sites along a 690 km transect in the South-Eastern Mount Isa. Geoscience Australia undertook data analysis and data inversion to create the most plausible resistivity model. 2D and 3D data modelling were undertaken using well-verified algorithms. The 2D and 3D resistivity models derived from the MT data show some consistent features that are likely to be the real subsurface geology. The near-surface conductive layer resolved by the MT models represents the Carpentaria and Eromanga sedimentary basins reasonably well, in terms of resistivity and thickness. The MT models reveal a predominant crustal-scale conductor, which is interpreted to be part of the Carpentaria Conductivity Anomaly. A number of localised zones of enhanced conductivity are also detected within the crust. These conductors correspond to known major faults identified by seismic and geological data. One of the faults, i.e. the Cork Fault, marks the tectonic boundary between the Mount Isa terrane and the Thomson Orogen. The geometries of these conductive bodies suggest that the enhanced conductivity may be caused by deformation or mineralisation associated with faulting. Some of these faults linking into the middle and lower crust are considered as the primary factors in the partitioning of mineralisation in the region. Results from the magnetotelluric data provide new insights into the understanding of the complex crustal structure where little geological history is known.

Magnetotelluric (MT) measures the natural variations of the Earth' magnetic and electrical (telluric) fields. The Audio-Magnetotelluric method (AMT) samples signal frequencies in the range of 20k Hz down to ~1Hz and provides data pertaining to the upper few kilometres of the Earth' crust. Broadband MT (BBMT) measures frequencies ranging from ~400 Hz down to periods of ~5000 s, providing measures of the conductivity of the crust. AMT and BBMT data were acquired at 138 stations with an interval of 2.5-5.0 km along a 690 km transect extending from Four Ways to Longreach in the South-eastern Mount Isa region. Full-waveform time series data were acquired and processed into frequency-domain transfer functions. Remote reference was applied to eliminate uncorrelated noise. After quality assurance, processed data were exported to industry-standard EDI files containing site info, impedance tensor, apparent resistivity, phase and vertical transfer function.

The Paleo-Mesoproterozoic Isa Superbasin is located in northwestern Queensland and is part of the geologically complex and resource rich Mount Isa Province. Over the last five years, the Northern Lawn Hill Platform (NLHP) in the northern part of the Isa Superbasin has become a focus for frontier conventional and unconventional hydrocarbon exploration. Thick and extensive organic-rich shale units in the River and Lawn supersequences are of particular interest for unconventional shale gas exploration following a gas discovery in 2014 from the Lawn Shale at Egilabia-2 DW1. Potential shale gas resources in these stratigraphic intervals include 22.1 Tcf of prospective gas and 0.15 Tcf of contingent (2C) gas resources (Armour Energy, 2014 and 2015). Other conventional and unconventional plays may also occur in overlying stratigraphic units within the Isa Superbasin. However despite the increased interest in the region’s petroleum prospectivity, the data coverage across the Isa Superbasin is sparse and aspects of the regional geological framework remain ambiguous. This report presents an update to seismic and well interpretation in the Isa Superbasin originally undertaken in the late 1990’s as part of the North Australian Basins Resource Evaluation (NABRE) Project in the NLHP, the area with the greatest concentration of data and petroleum exploration activity. The NABRE Project focussed on developing an integrated structural and stratigraphic framework for the NLHP in the context of understanding and predicting sediment-hosted mineral deposits. However, the project did not produce depth-converted structure or isopach maps, which are required for assessing and mapping conventional and unconventional petroleum plays. Assessments of the area’s resource potential would also benefit by incorporating some key recently acquired data sets and published research with the original NABRE work. The original NABRE work has therefore been updated to include interpretations from new seismic and well data, and to generate depth-converted structure and isopach maps for eight key stratigraphic horizons of interest for petroleum exploration in the NLHP. Major sub-surface structures are also formally defined and named based on the depth-structure maps. The review of the Isa Superbasin geological framework presented here underpins work on two major federal government initiatives, the Exploring For The Future Program and Geological and Bioregional Assessment Program. Recommendations are included in this report on further value adding work that could supplement these programs to better inform prospectivity assessment.

<div>The Canobie Airborne Gravity Gradiometer (AGG) survey of Northern Queensland was flown between 24 November and 3 December 2021. </div><div>Contracted to Xcalibur Multiphysics, Geoscience Australia undertook the project management, contract management and quality control on behalf of the Geological Survey of Queensland. </div><div>The located data, gridded data and quality control reports are contained within this record. </div><div><br></div><div>Survey area was centered on latitude 19° 31’ 04” S and longitude 140° 44’ 14” E to the north of Cloncurry. A total of 8 production flights were flown for a combined total of 4,712.4 </div><div>line kilometers of data and acquired on 1000 m line spacing at 80 m nominal terrain clearance</div><div>Quality control was performed by airborne gravity consultant Dr Mark Dransfield on behalf of Geoscience Australia, with his report included here.</div><div><br></div><div>The survey was designed to supplement the regional legacy ground gravity data and improve the definition of gravimetric anomalies in a region deemed highly prospective for base metals exploration. </div><div>In addition, the AGG survey will provide better understanding of the cover sequence thickness (estimated to be less than 100 m) and characteristics of the underlying basement geology. </div><div><br></div><div>The data was released by the Geological Survey of Queensland on March 29 and can be found at https://geoscience.data.qld.gov.au/dataset/gg100099/resource/geo-spa460972-gg100099. </div><div><br></div><div>Survey Name: Canobie airborne gravity gradiometery survey,2021</div><div>Datasets Acquired: Gravity gradiometry, digital terrain model</div><div>Geoscience Australia Project Number: P5021</div><div>Acquisition Start Date: 24/11/2021</div><div>Acquisition End Date: 03/12/2021</div><div>Flight line spacing: 1000 m</div><div>Flight line direction: East-West (090-270)</div><div>Total distance flown: 4,712 line-km</div><div>Nominal terrain clearance: 80 m</div><div>Blocks: 1</div><div>Data Acquisition: Xcalibur Multiphysics</div><div>Project Management: Geoscience Australia</div><div>Quality Control: Mark Dransfield on behalf of Geoscience Australia</div><div>Dataset Ownership: Geological Survey of Qld and Geoscience Australia</div><div><br></div><div>Included in this release:</div><div>1. Point-located Data</div><div>ASCII-column data with accompanying description and definition files.</div><div>• Gravity gradiometry data including the various corrections</div><div>• Gravity gradiometry data noise estimates</div><div>• Vertical gravity estimate including various reduction and levelled corrections</div><div>• Digital terrain model</div><div><br></div><div>2. Grids</div><div>Gridded data in ERMapper (.ers) format (GDA2020):</div><div>• Gravity gradiometry</div><div>• Free-air corrected vertical gravity</div><div>• Terrain and bouguer corrected vertical gravity</div><div>• Digital terrain model</div><div><br></div><div>3. Reports</div><div>• Contractors Logistics Report</div><div>• Quality Control Report (Mark Dransfield)</div><div><br></div><div>4. Location</div><div>• ARCGIS shape file</div><div><br></div><div><br></div><div>© Geological Survey of Queensland and Commonwealth of Australia (Geoscience Australia) 2021. With the exception of the Commonwealth Coat of Arms and where otherwise noted, this product is provided under a Creative Commons Attribution 4.0</div>

Geoscience Australia (GA) and the Geological Survey of Queensland (GSQ) conducted the Cloncurry Magnetotelluric (MT) survey. MT data (0.001 s to 1000 s in period) at 476 sites with a grid spacing of 2km were acquired over an approximate 40km x 60km area in the Cloncurry region from July to November 2016. The survey area covers the eastern margin of the Mount Isa Block situated to the west of the Eromanga Basin. The MT data can image the thickness of cover, the basement architecture and the crustal architecture in this area that has high resource exploration potential. Data QA/QC were performed during the data acquisition stage of the survey. This release includes processed MT data and a data acquisiton report written by the contractor. Details on the data processing, data analysis, and modelling/inversion of the data will be released as a comprehensive report at a later date.

Zircon and xenotime U–Pb SHRIMP geochronology was conducted on samples from the South Nicholson Basin, and western Mount Isa Orogen. These samples were collected from outcrop and core from the Northern Territory and Queensland. The age data indicate the South Nicholson Basin was deposited after ca 1483 Ma but deposition most likely had ceased by ca 1266 Ma; the latter age likely represents post-diagenetic fluid flow in the area, based on U–Pb xenotime data. Geochronology presented here provides the first direct age data confirming the South Nicholson Group is broadly contemporaneous with the Roper Group of the McArthur Basin, which has identified facies with high hydrocarbon prospectivity. In addition, geochronology on the Paleoproterozoic McNamara Group provides new age constraints that have implications for the regional stratigraphy. The data obtained in this geochronological study allow for a comprehensive revision of the existing stratigraphic framework, new correlations and enhances commodity prospectivity in central northern Australia.

This Record presents new Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronological results for samples collected from the Mary Kathleen Domain, which forms the western part of the Eastern Fold Belt in the Mount Isa Inlier. Eight samples, comprising three granites, one quartz diorite, two metarhyolites, one feldspathic quartzite, and one of matrix material from a breccia, have been analysed as part of ongoing investigations by GSQ in collaboration with researchers from James Cook University. The results enable a better understanding of the evolution of the domain, the associated magmatism, and any related mineralisation. <b>Bibliographic Reference:</b> Kositcin, N., Bultitude, R.J., and Purdy, D.J. Summary of Results. Joint GSQ–GA Geochronology Project: Mary Kathleen Domain, Mount Isa Inlier, 2018–2019. <i>Queensland Geological Record</i><b> 2019/02</b>.

The Exploring for the Future program Virtual Roadshow was held on 7 July and 14-17 July 2020. The Minerals session of the roadshow was held on 14 July 2020 and consisted of the following presentations: Introduction - Richard Blewett Preamble - Karol Kzarnota Surface & Basins or Cover - Marie-Aude Bonnardot Crust - Kathryn Waltenberg Mantle - Marcus Haynes Zinc on the edge: New insights into sediment-hosted base metals mineral system - David Huston Scale reduction targeting for Iron-Oxide-Copper-Gold in Tennant Creek and Mt Isa - Anthony Schofield and Andrew Clark Economic Fairways and Wrap-up - Karol Czarnota

From June 23rd to November 4th 2016 Geotech Ltd. carried out a helicopter-borne geophysical survey over part of East Isa in Queensland (figure 1). Operations were based at Cloncurry, Queensland. The traverse lines were flown in an east to west (N 90° E azimuth) direction with 2km and 2.5km traverse line spacings, with three Tie lines flown perpendicular to the traverse lines. During the survey the helicopter was maintained at a mean altitude of 76 metres above the ground with an average survey speed of 90 km/hour. This allowed for an actual average EM Transmitter-receiver loop terrain clearance of 38 metres and a magnetic sensor clearance of 68 metres. The principal geophysical sensors included a versatile time domain electromagnetic (VTEMTMPlus) full receiver-waveform system, and a caesium magnetometer. Ancillary equipment included a GPS navigation system, laser and radar altimeters, and inclinometer. A total of 15697 line-kilometres of geophysical data were acquired during the survey. The electromagnetic system is a Geotech Time Domain EM (VTEMplus) with full receiver-waveform streamed data recording at 192 kHz. The "full waveform VTEM system" uses the streamed half-cycle recording of transmitter current and receiver voltage waveforms to obtain a complete system response calibration throughout the entire survey flight. The VTEM transmitter loop and Z-component receiver coils are in a concentric-coplanar configuration and their axes are nominally vertical. An X-component receiver coil is also installed in the centre of the transmitter loop, with its axis nominally horizontal and in the flight line direction. The receiver coils measure the dB/dt response, and a B-Field response is calculated during the data processing. In-field data quality assurance and preliminary processing were carried out on a daily basis during the acquisition phase. Preliminary and final data processing, including generation of final digital data products were undertaken from the office of Geotech Ltd. in Aurora, Ontario. A set of Conductivity Depth Images (CDI) were generated using EM Flow version 3.3, developed by Encom Technologies Pty Ltd. A total of forty-five (45) dB/dt Z component channels, starting from channel 4 (21 µsec) to channel 48 (10667 µsec), were used for the CDI calculation. An averaged waveform at the receiver was used for the calculation since it was consistent for the majority of the flights with minor deviation from the average. Digital data includes all electromagnetic and magnetic data, conductivity imaging products, mulitplots plus ancillary data including the waveform.

Exploring for the Future (EFTF) is a four-year $100.5 million initiative by the Australian Government conducted by Geoscience Australia in partnership with state and Northern Territory government agencies, CSIRO and universities to provide new geoscientific datasets for frontier regions. As part of this program, Geoscience Australia acquired two new seismic surveys that collectively extend across the South Nicholson Basin (L120 South Nicholson seismic line) and into the Beetaloo Sub-basin of the McArthur Basin (L212 Barkly seismic line). Interpretation of the seismic has resulted in the discovery of new basins that both contain a significant section of presumed Proterozoic strata. Integration of the seismic results with petroleum and mineral systems geochemistry, structural analyses, geochronology, rock properties and a petroleum systems model has expanded the knowledge of the region for energy and mineral resources exploration. These datasets are available through Geoscience Australia’s newly developed Data Discovery Portal, an online platform delivering digital geoscientific information, including seismic locations and cross-section images, and field site and well-based sample data. Specifically for the EFTF Energy project, a petroleum systems framework with supporting organic geochemical data has been built to access source rock, crude oil and natural gas datasets via interactive maps, graphs and analytical tools that enable the user to gain a better and faster understanding of a basin’s petroleum prospectivity. <b>Citation:</b> Henson Paul, Robinson David, Carr Lidena, Edwards Dianne S., MacFarlane Susannah K., Jarrett Amber J. M., Bailey Adam H. E. (2020) Exploring for the Future—a new oil and gas frontier in northern Australia. <i>The APPEA Journal</i><b> 60</b>, 703-711. https://doi.org/10.1071/AJ19080