基金We are very grateful to the Guangzhou Ocean Geological Survey and the CHOICE-C National Key Basic Research and Development Scheme for providing research samples. We also thank the Chinese Academy of Sciences, and the State Bureau of Foreign Exports In- ternational Innovation Team Partner Project for their support. Finally, we sincerely thank the two anonymous reviewers for their detailed and construc- tive suggestions that have helped improve our manuscript. We also thank the National Natural Science Foundation of China （Grant Nos. 41303067, 41103043 ＆ 41273022）, the Chinese Academy of Sciences Knowledge Inno- vation Project （Grant No. KGZD-EW-301）, the PetroChina-Chinese Acad- emy of Sciences Science and Technology Cooperation Project （Grant No. 2015A-4813）.