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Logatchev. The Logatchev hydrothermal field was discovered at 14 45’N in 1994 and also was known to consist of several separate sites: Logatchev 1 (main and largest site) and 2 (Fig. 3). The Logatchev 1 hydrothermal field at 14 45 N was discovered in 1994 by using deep-towed RIFT system (with measurement of EP) and subsequent TV profiling and sampling (Batuev et al., 1994). However, high CH4 and Mn concentrations in deep seawater in this region were detected earlier (Klinkhammer et al., 1985; Charlou and Donval, 1993). Sulfide-like deposits were found and photographed at 14 54’N near the foot of the eastern wall of the rift valley (Eberhart et al., 1988). The first samples of hydrothermal sulfides not far from Logatchev were dredged from the rift valley walls 20 km from the ridge axis in 1990-1991 by Russian geologists. In the following years, after 1994, the Logatchev hydrothermal field was revisited many times by Russian (Krasnov, et al., 1995; Bogdanov et al. 1997; Gebruk et al., 1997, 2000; Mozgova et al., 1999; Cherkashov et al., 2000; Sudarikov et al., 2000)(eg, MIR diving expeditions in 1995 and 1998), French (MICROSMOKE, 1995; Poroshina et al., 1998), German (Kuhn et al., 2004; Schmidt et al., 2007; eg, see article by Borowski et al., this volume), American (MAR-97, 1997; DIVERSE, 2001), and Chinese (Zhou et al., 2007) expeditions. Prior to the Serpentine cruise the Logatchev 2 field was never visited by a submersible or ROV and was considered inactive.

Krasnov. The Krasnov field is an inactive hydrothermal field at l6 38.4’N, 46 28.5’W that was identified and sampled in 2004 (samples of massive sulfides were …