1. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
2. School of Earth and Space Sciences, Peking University, Beijing 100871, China
3. School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
4. State key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China