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Gawler Craton Airborne Survey update

The first data from the world’s largest high-resolution airborne geophysical and terrain imaging program is imminent and will be fundamental in reinterpreting the geological structure of the Gawler Craton.

Largest airborne acquisition in South Australia’s history

Figure 1 Gawler Craton Airborne Survey – acquisition completion status at 10 August 2017.
Figure 1 Gawler Craton Airborne Survey – acquisition completion status at 10 August 2017.

The $10 million PACE Copper Gawler Craton Airborne Survey has already collected 616,004 line kilometres of magnetic, radiometric and terrain data, with 34% of the total survey area completed to date (Fig. 1). The survey, designed to expand opportunities for exploration by the mineral resources sector, will cover 341,000 km2 of central South Australia and collect over 1.87 million line kilometres of new data.

The data is being collected at a line spacing of 200 m and flown at a nominal terrain clearance of 60 m. This will dramatically improve the pre-existing patchwork dataset of smaller surveys by providing a single uniform dataset that will allow for reinterpretation of the geology, structure and prospectivity in the region. Example comparisons of previous and new data are shown in Figures 2 and 3.

The survey has been split into three tranches to manage the data acquisition process and allow for faster delivery of the data to all stakeholders. Acquisition of the six regions flown in Tranche 1 was completed in June and the first data release (Regions 2A, 2B, 3A, 3B, 4A and 4B) is expected to be available through the South Australian Resources Information Gateway (SARIG) in September. As soon as it is available, an announcement of the data release will be made through SARIG, Twitter and LinkedIn.

Figure 2 Comparison of former and new total magnetic intensity data in the Gawler Craton region.

Figure 2 Comparison of previous and new total magnetic intensity data in the Gawler Craton region.

Figure 3 Comparison of former and new ternary radiometric data in the Peake and Denison Ranges region.

Figure 3 Comparison of previous and new ternary radiometric data in the Peake and Denison Ranges region.

Raising the bar on regional data acquisition

The Geological Survey of South Australia (GSSA) has partnered with Geoscience Australia to manage the acquisition process and quality control of data. The specifications for data capture and delivery formats have been reviewed to bring them into line with best practice equipment and technology standards. For example:

  • sample density of magnetic data along the flight lines has doubled from a nominal 7 m to 3.5 m, when compared with the older 400 m spaced lines
  • laser altimeter data is being captured to derive digital elevation models
  • a series of test lines have been established near Whyalla to enable quantitative comparisons of the acquired data for all equipment used during the survey.

The test line data will enable the radiometric data to be back-calibrated, providing optimally levelled radiometric data between all of the aircraft and survey blocks and result in a seamless grid after all of the survey data is combined.

Value adding

The GSSA has partnered with CSIRO to add value to the data through additional products such as magnetic depth-source models, 3D inversions of key anomalies and gridded depth to basement surface. These will be released for each block around 6 months after each data release.

Partners

The Gawler Craton Airborne Survey is a key deliverable of the PACE Copper initiative, a core component of South Australia’s Copper Strategy, and is being conducted by the GSSA in partnership with Geoscience Australia and CSIRO under the respective state–federal national collaboration frameworks.

The GSSA General Manager Geoscience Initiatives (PACE), Chris Wilcox, said:

‘Already the data from the Gawler Craton Airborne Survey is providing a clearer picture of the basement geology in the Gawler Craton. By improving our knowledge of the Gawler Craton, the South Australian Government is facilitating the discovery of the next generation of worldclass mineral deposits.’

Keep up to date via the Gawler Craton Airborne Survey community information webpage.

– Laszlo Katona, Chris Wilcox and Tania Davies

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