During January to February 2011, the 2nd Leg of the COMRA’s 22 Cruise found three hydrothermal fields on 13-14°S Mid-Atlantic Ridge (MAR). They were named temporarily as Rainbow Bay North, Valentine Valley and Tai Chi, respectively.
Hydrothermal activity along the southern MAR has been investigated and documented by a few cruises. German et al. (2008) reported two high temperature hydrothermal fields at 4°S and 4°48′S. Hasse et al. (2009) found the Lilliput hydrothermal field which extends to 1000m×250m at a depth of 1,500m. However, no hydrothermal vents located south of 13°S along the southern MAR were reported before 2009. In 2009, two active hydrothermal fields were found in COMRA’s 21 Cruise, which was temporarily named as Baily's Beads 2009 and Rainbow Bay South respectively. The Baily's Beads 2009 field is at a depth of about 2,288m and located at 14.41°W 13.28°S. The Rainbow Bay South field is at 14.34°W, 14.06°S on the slope of a volcano, lying on the inside corner between the axial ridge and transform fault, at a depth of about 2,900m (Tao et al, 2011).
The Rainbow Bay North field was found at 14.36°W, 14.03°S at a depth of 1900m, which may extend to 480m×780m. Massive sulfides were collected by a ROV. The Valentine Valley field is located at 14.41°W, 13.25°S and is about 4 km south of the Baily's Beads 2009 field. It is located along the N-S fissures on the central valley. The Tai Chi field is at 14.52°W, 13.59°S and was detected using CTD. Black smoke, shrimps and bivalves were videoed by the deep tow system in this active field.
Furthermore, four hydrothermal anomalies were detected by CTD and they are located at (14.67°W, 13.60°S), (14.56°W, 13.70°S), (14.53°W, 13.75°S) and (14.54°W, 13.87°S) along the southern MAR respectively.
These newly discovered hydrothermal vents and anomalies indicate that the ridge segment of 13-14°S MAR is a promising area for hydrothermal activity.
We thank captains and crews of the COMAR’s 22 cruises on R/V DayangYihao and Dr. S. Petukhov and Dr. I.Egorov from the All-Russia Research Institute of Geology and Mineral Resources of the World Ocean (VNIIOkeangeologia) who contributed to the success of this leg.
Authors:
Chunhui Tao1; Huaiming Li1; Zongze Shao2; Gengsheng Bao1; Xin Su3; John Y Chen4; Xianming Deng1; Zhongyan Qiu1; Kai Zhang1; Jiabiao Li1; COMRA’ 22 Cruise Science Party
1Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, 310012, China
2Third Institute of Oceanography, State Oceanic Administration, Xiamen, 361000, China
3China University of Geosciences (Beijing), Beijing 100083, China;
4Peking University, Beijing, 100871, China
References:
German, C.R., Bennett, S.A., Connelly, D.P. et al. Hydrothermal activity on the southern Mid-Atlantic Ridge: Tectonically- and volcanically-controlled venting at 4–5°S. Earth and Planetary Science Letters, 2008, 273: 332–344.
Haase, K.M., Koschinsky, A., Petersen, S. et al. Diking, young volcanism and diffuse hydrothermal activity on the southern,Mid-Atlantic Ridge: The Lilliput field at 9°33′S. Marine Geology, 2009, 266: 52-64.
Tao, C.H., Li, H.M., Yang Y.M. et al. Two southernmost hydrothermal fields found on the South Mid-Atlantic Ridge. Science China Earth Sciences, in press.
