Airborne Electromagnetics

TEMPEST system operated in Australia by Fugro Airborne Surveys Pty Ltd

TEMPEST system operated in
Australia
© Geoscience Australia

SkyTEM system operated in Australia by Geoforce Pty Ltd

SkyTEM system operated in
Australia by Geoforce Pty Ltd
© Geoscience Australia

VTEM system operated in Australia by Geotech Airborne Pty Ltd

VTEM system operated in
Australia
© Geoscience Australia

Airborne Electromagnetic (AEM) data are one form of the geophysical data acquired by Geoscience Australia. The data are gathered by transmitting an electromagnetic signal from a system attached to a plane or helicopter. The signal induces eddy currents in the ground which are detected by receiver coils towed below and behind the aircraft in a device called a bird. Depending on the system used and the subsurface conditions, AEM techniques 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 sulfide minerals.

Applications of AEM

AEM surveys are more expensive than other airborne geophysical systems and government organisations have acquired AEM data in only relatively small and isolated patches across Australia. AEM surveys also require more complex processing to allow interpretation and, therefore, are usually designed to detect particular subsurface targets which are based on a perceived conductivity contrast, for example:

  • the spatial extent of geological features, such as a clay-rich unit in a sedimentary sequence or a graphitic unit in a metamorphic complex
  • the depth of an unconformity between sedimentary cover and the underlying basement rock
  • the location of groundwater resources, such as fresh or saline aquifers.

AEM acquisition for the Onshore Energy Security Program

Several new AEM surveys are being acquired as part of Geoscience Australia’s Onshore Energy Security Program (OESP). The surveys are designed to reveal new information about regions which are considered prospective for energy resources. Through the innovative approach of acquiring the AEM data at wide line spacings of one to six kilometres, the surveys will cover relatively large areas. Mineral exploration companies will benefit through an improved understanding of the regional geology and having the opportunity to collaborate by paying for more detailed data acquisition over a specific area of interest. More information on AEM acquisition for the OESP is available on the OESP home page.

AEM acquisition for Natural Resource Management

Geoscience Australia has also been involved in the acquisition and processing of AEM surveys for Natural Resource Management (NRM), particularly in relation to salinity or groundwater issues in the Murray-Darling Basin. These surveys, such as the Lower Macquarie survey in central west New South Wales, were acquired and processed by Geoscience Australia as part of large multi-agency projects managed by the then Bureau of Rural Sciences. The surveys have revealed important new information relevant to NRM, such as the distribution of freshwater aquifers in the sediments of the Murray Basin. AEM data is also a key dataset used to asses groundwater aquifers as part of the Broken Hill Managed Aquifer Recharge Project.

Topic contact: minerals@ga.gov.au Last updated: October 4, 2013