1. CSIRO Mineral Resources Flagship, Bentley, Perth, WA 6102, Australia.
2. Corresponding author.
3. Aarhus Geophysics, C. F. Møllers Allé 4 DK-8000 Aarhus C, Denmark.
4. University of Potsdam Institute of Earth and Environmental Science, Karl-Liebknecht-Str. 24–25, 14476 Potsdam-Golm, Germany.
5. Geological Survey of Denmark and Greenland (GEUS), Lyseng Allé 1, 8270 Højbjer, Denmark.
6. RMIT University School of Applied Sciences, GPO Box 2476, Melbourne, Vic. 3001, Australia.
7. TechnoImaging, 4001 S 700 E, Salt Lake City, UT 84107, USA.