1. Ph.D. Candidate, Department of Geology and Mineral Resources Engineering, Norwegian Univ. of Science and Technology (NTNU), Trondheim 7491, NO (Corresponding author), e-mail: joyidol1013@hotmail.com; yu.chen@ntnu.no
2. Professor, Department of Geology and Mineral Resources Engineering, Norwegian Univ. of Science and Technology (NTNU), Trondheim 7491, NO.