AusAEM

AusAEM was a very wide spaced airborne electromagnetic (AEM) survey of a large region of northern Australia, using a line spacing of 20 km. It represents the largest AEM survey of its kind ever undertaken. The AEM technique enables mapping of the subsurface electrical conductivity of rocks, sediments and waters, to depths of up to several hundred metres, depending on factors such as the AEM system used and the electrical conductivity of the sub-surface.

Map of stage 1 and 2 of the AusAEM survey. AusAEM 1 (in red) AusAEM 2 (in purple). Data for these areas has been released. The remaining acquisition (in green) is pending.

AEM is a non-invasive testing technique that can detect variations in the conductivity of the ground to a depth of several hundred metres. The conductivity response in the ground is commonly caused by the presence of electrically conductive materials such as salt or saline water, graphite, clays and sulphide minerals.

AusAEM data and derived products are used to map the thickness and character of sedimentary and regolith cover in regions flanking crystalline basement outcrop. Previous surveys by Geoscience Australia using wide line spacing (e.g. 6 km) have shown the utility of the method in mapping cover thickness and its character. The survey results are also used by the groundwater community to assess the potential for groundwater resources in Australia's arid zones to support remote communities in the survey areas.

The AusAEM surveys are divided into two blocks denoted AusAEM1 and AusAEM2, based approximately on 1:1 million map sheets.

The data have been assessed for best practice l quality assurance and quality control checks and are deemed by Geoscience Australia's geophysicists as fit-for-purpose and use by the geophysical community.

AusAEM 2 Survey (data now available)

Geoscience Australia has conducted a series of airborne electromagnetic (AEM) surveys across the Northern Territory and Western Australia between 2019 and 2020.

The AusAEM2 airborne electromagnetic survey was originally to take place between May 2019 and March 2020 in northern Western Australia and south-west Northern Territory. Survey acquisition reached 72 percent in October (Part A) prior to the aircraft demobilizing for North America to undertake works for the United States Geological Survey.

The aircraft’s planned return in January 2020 to complete Part B was delayed due to COVID-19 restrictions. The remaining area is planned to be flown as part of the EFTF extension during the next 2-4 years.

All data collected so far has been released and is available at: http://pid.geoscience.gov.au/dataset/ga/140156

Map of AusAEM1 showing airborne electromagnetic completed flight lines in the Northern Territory and Queensland. Where practical, flight lines have been deviated to cross boreholes where downhole well and wireline data will provide ground calibration options as part of the inversion and interpretation processes.

AusAEM1 Survey NT-QLD (completed)

A total of 60,000 line kilometres were acquired between the 2017 and 2018 field season. The AusAEM survey also includes over 2,200 line kilometres of infill flying at tighter line spacing, funded by private exploration companies, in certain infill blocks within the survey area.

The AEM data was integrated with other datasets collected as part of the EFTF program (surface geochemistry, groundwater hydrochemistry, seismic, magnetotelluric, potential field, solid geology, isotopic mapping) to assist with stratigraphic drilling to characterise the under-cover geology.

This survey was led by Geoscience Australia in collaboration with the Northern Territory Geological survey and the Geological Survey of Queensland as part of the Exploring for the Future (EFTF) program.

Outputs

Complete AusAEM1 survey coverage across the Northern Territory and Queensland, showing the integrated map of conductivity depth sections generated through 1D inversion of the entire dataset.

All data acquired during 2017 and 2018 field season is available to download: AusAEM data and Em Flow® conductivity estimates

The data release package contains the final deliverables produced by the contractor CGG including:

  • The survey logistics and processing report
  • Final processed electromagnetic, magnetic and elevation point located line data
  • Final processed electromagnetic, magnetic and elevation grids
  • Conductivity estimates generated by the EM Flow® conductivity depth imaging algorithm
  • Graphical multiplots of line data and EM Flow® conductivity sections
  • Graphical stacked EM Flow® conductivity sections

Representative conductivity-depth section of a segment of TEMPEST® data from the western-most flight line of the AusAEM1 survey (above). When combined with national compilations of geochemical, borehole, geological and other geophysical datasets (for example, magnetics radiometrics and gravity), the regional AEM/resistivity mapping now being undertaken provides unprecedented insight into the resource potential across northern Australia.

Geoscience Australia has also released its own inversion products and are available via the following link: http://pid.geoscience.gov.au/dataset/ga/132709

Video: Airborne electromagnetic data mapping mineral and groundwater resources.

Collaborations

Geoscience Australia is partnered with State and Territory government geoscience agencies to deliver the AusAEM program. Industry have subscribed to areas of infill in both t survey areas, as this approach was successfully used in a previous exploration initiative of the Commonwealth Government — the Onshore Energy Security Program (OESP). Industry benefits include low acquisition and zero mobilisation costs.

The infill line data are confidential for a period of twelve (12) months from the date the final survey data is provided to the subscriber. The moratorium period has expired for AusAEM1 and expires June 2022 for AusAEM2. All available located and inversion data, including released infill, can be obtained through GA’s electronic catalogue, with links provided above.

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