1. a Department of Earth Sciences , The University of Hong Kong , Hong Kong SAR , P. R. China
2. b State Key Laboratory of Organic Geochemistry , Guangzhou Institute of Geochemistry , Guangzhou , P. R. China
3. c Department of Civil and Structural Engineering , The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong SAR , P. R. China