[1] Univ Melbourne, Sch Earth Sci, Melbourne, Vic 3010, Australia
[2] Bundesanstalt Geowissensch & Rohstoffe, D-30655 Hannover, Germany
[3] GaiaPix, ZA-2123 Pinegowrie, South Africa
[4] GAF AG, D-80634 Munich, Germany
[5] Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 0200, Australia