First Active Hydrothermal Vent Fields Discovered at the Equatorial Southern East Pacific Rise

In August-September 2008, the third leg of the 2008 Chinese DY115-20 expedition on board R/V DayangYihao has successfully discovered, for the first time, active hydrothermal vent fields on the fast-spreading Southern East Pacific Rise (SEPR) near the equator. This expedition follows the work of a 2005 expedition by R/V DayangYihao, during which water column turbidity anomalies were measured in the region.

The newly discovered vent fields are located along a 22-km-long ridge segment of the SEPR at 102.655ºW/2.22ºS, 102.646ºW/2.152ºS, 102.619ºW/2.078ºS and 102.62ºW/2.02ºS, respectively, as well as on an off-axis volano near 102.456ºW/1.369ºS. A significant portion of the activity appears to be concentrated along the edges of a seafloor fissure system. Furthermore, water column turbidity anomalies were observed over off-axis volcanoes near 102.827ºW/2.084ºS and 102.58ºW/2.019ºS. Video footage of the vent fields and water column turbidity, temperature, and methane anomalies were detected by a deep-towed integrated system consisting of video, still camera, CTD, ADCP, and MAPR and METS sensors.

Two active hydrothermal fields at 2.217ºS and 2.023ºS were then extensively photographed and surveyed using the autonomous underwater vehicle ABE of the Woods Hole Oceanographic Institution (WHOI). Thousands of near-bottom color photographs were taken and several types of water column data were recorded during the ABE dives. Four samples of hydrothermal chimneys were successfully obtained by a TV-guided grab in three locations, showing evidence of high-temperature hydrothermal venting. Preliminary analyses of four chimney samples of the new vent fields reveal the average precious metal concentrations of Au (0.29 ppm), Ag (92.2 ppm), Cu (6.2%), Fe (23.2%), Zn (11.8%), Mn (128.8 ppm), Pb (953 ppm), Co (1970 ppm), and Ni (6.7 ppm).

This expedition was funded and sponsored by China Ocean Minerals R & D Association (COMRA) in collaboration with a WHOI team. The research was conducted on board the 105-meter-long R/V DayangYihao. This finding was reported at the fall meeting of the American Geophysical Union in Dec. 2008 in San Francisco (abstract V41B-2081).

Chunhui Tao1, Jian Lin2, Guanghai Wu1, Christopher R. German2, Dana R. Yoerger2, Y. John Chen3, Ning Zhou4, Shiqing Guo4, Xiqiu Han1, Zhigang Zeng5, Hongfa Wang1, Tao Ding1, Shuitu Gao1, Xinyan Qian1, Ruyong Cui6, Jianping Zhou1, Dezhan Ye7, Li Li8, Scientific Party9, Edward T. Baker10, Ko-ichi Nakamura11

1Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, 36 Baochubei Road, Hangzhou, Zhejiang, 310012, China; 86-571-88829003,
2Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
3Institute of Theoretical and Applied Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China
4China Ocean Mineral Resources R&D Association, 1 Fuxingmenwai Avenue, Beijing 100860, China
5Institute of Oceanology, Chinese Academy of Sciences, Qiangdao, China
6Qingdao Institute of Marine Geology, Qingdao 266071, China
7Third Institute of Oceanography, Xiamen 361005, China
8Pioneer High Technology Corp., Beijing 100860, China
9DY115-20 Leg 3 Scientific Party
10Pacific Marine Environmental Laboratory, NOAA, Seattle, WA 98115, USA
11AIST, Tsukuba, Ibaraki 305-8567, Japan