1. Economic Geology Research Centre, College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia
2. Colorado School of Mines, Department of Geology and Geological Engineering, 1516 Illinois St., Golden, Colorado 80401
3. Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa
4. Vital Metals Ltd., Suite 1, 91 Hay Street, Subiaco, Western Australia 6008, Australia
5. Argon Geochronology Laboratory, Department of Earth and Environmental Sciences, University of Michigan, 2534 C.C. Little Building, 1100 N. University Ave., Ann Arbor, Michigan 48109-1005