1. School of Resources and Safety Engineering, Central South Univ., Changsha 410083, China.
2. Professor, School of Resources and Safety Engineering, Central South Univ., Changsha 410083, China.
3. School of Resources and Safety Engineering, Central South Univ., Changsha 410083, China (corresponding author).
4. Dept. of Earth and Space Sciences, Southern Univ. of Science and Technology, Shenzhen 518000, China.