1. Osaka Metropolitan University, Department of Geosciences, Osaka 558-8585, Japan
2. Kyoto University, Department of Geology and Mineralogy, Kyoto 606-8502, Japan
3. Kyushu University, Department of Earth and Planetary Sciences, Fukuoka 819-0395, Japan
4. University of Graz, Institute for Earth Sciences, 8010 Graz, Austria