基金Foundation item： the National Basic Research Program of China under contract No. 2012CB417305 China Ocean Mineral Resources Research ＆ Development Association Project under contract No. DY125-11 Endowment Fund of International Seabed Authority （the International Cooperative Study on Hydrothermal System at Ultraslow Spreading SWIR）.
基金Acknowledgement This study was supported by grants from the Key Project of Chinese Ministry of Education （no.： 104004） and the National Natural Science Foundation of China （no.：40839907）. We are grateful to Wang Yan＇geng, the chief geologist at the Guizhou Geology and Minerals Bureau （Guizhou, China）, for his guidance in the field. We would like to thank Professor Du Andao for her help with the analysis at the National Research Center for Geoanalysis, Beijing, and also Professor Yong Lai and Mr Xiaohua Deng at the Peking University for their communication and assistance in the manuscript writing. The manuscript was greatly improved following thorough and careful review by Professor Chen Daizhao at Insitute of Geology and Geophysics, Chinese Academy of Sciences.