1. School of Earth Science and Mineral Resources; China University of Geosciences; Beijing 100083 China
2. CARMA, Institute of Geology; Chinese Academy of Geological Sciences; Beijing 100037 China
3. Department of Geology, Shideler Hall; Miami University; Oxford OH 45056 USA
4. PetroChina Southwest Oil & Gasfield Company Engineering Technology Research Department; Chengdu 618300 China