1. Dept. of Geological Sciences, Pusan National University, Busan, 609-735, South Korea
2. Dept. of Earth Sciences, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada
3. Dept. of Energy and Resources Engineering, Chonnam National University, Gwangju 500-757, South Korea
4. Mineral Resources Research Division, Korea Institute of Geosciences and Mineral Resources (KIGAM), Daejeon 305-350, South Korea