1. Department of Geosciences, Geotechnology, and Materials Engineering for Resources; Graduate School of Engineering and Resource Science; Akita University; Akita; Japan
2. Mineral Resources Development Unit; Council for Geoscience; Pretoria; South Africa
3. Center for Geo-Environmental Science; Akita University; Akita; Japan
4. International Center for Research and Education on Mineral and Energy Resources; Akita University; Akita; Japan
5. Department of Earth Sciences; Okayama University; Okayama; Japan