Abstract: Seafloor sulfide is an important undersea resource after the polymetallic nodules and the cobalt rich manganese crusts. China has made great achievements since starting sulfide investigation in 2005, but the most important problem how to deal with 3D structure of sulfide has been questioning us. On land, the electromagnetic methods have always been important for that. With the first independently developed TEM device, China has gained the first data for seafloor sulfide at South Atlantic Ridge(13.2°S,14.4°W) in June 2011 during cruise DY22 segment 5. The preliminary results correspond well with the actual hydrothermal vent area, and the detection depth reached 50~100 m below seabed, which verifies the reliability of the equipment.

Key words: electromagnetic methods, mid-ocean rdige hydrothermal activity, seafloor polymetallic sulfides, sulfide exploration, ocean expedition