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Boosting mineral exploration

New Gawler Craton Airborne Survey products.

SARIG is the go to gateway to access the data and new range of analytic and depth estimation products being released from the Gawler Craton Airborne Survey (Fig. 1).

Figure 1 SARIG screenshot highlighting survey regions with data released (regions 2A–B, 3A–B, 4A–B) and links to data and reports.
Figure 2 Example of data from Region 2A depth models report.
Figure 2 Example of data from Region 2A depth models report. Map of basement elevation modelled from total magnetic intensity, using an intensive, high-focus depth estimation methodology, which can be reasonably justified as providing superior solutions through selection of only the most appropriate data, intensive computation of those small data packets, and direct comparison of fields forward computed from the proposed solutions with the input data (which is unavailable in most other methodologies).
Figure 3 Gawler Craton Airborne Survey community information webpage.
Figure 3 Gawler Craton Airborne Survey community information webpage. Blue regions indicate survey blocks in progress; flight plans for the week are updated to indicate the main region being surveyed in each active block. Clicking the airplane icon provides call-sign information for the aircraft on each block. Clicking the blocks provides access to data downloads as well as contractor information, start and completion dates for each region in progress.

In progress since January 2017, there are 16 survey regions in total, of which six are complete with data released (regions 2A–B, 3A–B, 4A–B), including one set of enhanced images and modelled products (region 2A; Fig. 2). A further six regions are in final stages of quality control of deliverables (regions 1A–B, 8A–B, 9A, 10). The final four regions are in the acquisition phase (regions 5, 6, 7 and 9B) and due for completion in December 2018.

It is expected that the survey data will reveal new features in the magnetic field and provide confidence that subtle variations in the field are due to geological signal and not the amalgamation of inhomogeneous data (pre-existing patchwork of historical surveys).

The intrinsic value of geophysical survey products is not the data itself, but the new insights it can provide into the underlying geology, facilitating the improved discovery of new resources. To achieve those discoveries all companies and groups must first process the raw data to generate enhancement images and depth estimates, before applying exploration concepts, which are their competitive advantage. By supplying high-quality enhancements and depth solutions, all explorers from the smallest to largest can work from high-quality products. Any company preferring their own enhancements or depth solutions has access to the primary data to do that work themselves if they prefer.

The survey data and products redefine the depth of information provided by government for modern regional airborne magnetics and radiometrics – setting new benchmarks for precompetitive geoscience delivery in Australia.

Report covers image

The Gawler Craton Airborne Survey Community Information webpage (Fig. 3) continues to provide weekly updates of aircraft flight plans and, like SARIG, provides direct links to data package downloads and reports. (Clicking on a survey region displays survey information and a link that opens a new window with data downloads.)

Download Region 2A data package and enhanced geophysical imagery and magnetic source depth models reports

Background

The Gawler Craton Airborne Survey provides a world-class magnetic field coverage of the highly prospective Gawler Craton with uniform, high-quality data collected at 200 m line spacing and 60 m terrain clearance. The final aggregated length of the entire survey is approximately 1,650,000 line kilometres, over an area totalling 294,000 km2.

The survey is being undertaken by the South Australian Government in partnership with Geoscience Australia while the analytic enhancement images and magnetic source depth estimates are being produced in partnership with CSIRO.

Several strategies were identified in planning the survey and have been rigorously followed through to delivery of the final products. Key components of these strategies are:

  • the development and enforcement of new quality control methodologies to ensure the highest quality of the primary data
  • enhancement of the measured magnetic field data to better reveal characteristics such as structural trends and dislocations which will be key to geological interpretation
  • application of an intensive and highly focused magnetic source depth study
  • integration with existing ground-based gravity measurements that provide an independent imaging of the geology (the combination of gravity and magnetic imaging provides a more ‘stereoscopic’ image of the subsurface than can be derived by either methodology independently).

– Laszlo Katona and Clive Foss, August 2018

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