At 21:00 today we did our first ROV dive.
An E-W trending chain of five hydrothermal vent fields (Semenov 1-5) has been located in the area, though only one, Semenov 2, has been inferred to be active (Beltenev, 2009). The main purpose of our first dive was to locate, characterize and sample this active venting.
VICTOR was deployed in the northern part of the 13° 30’N core complex, then following a scarp uphill southwards towards shallowest point of the complex. We recovered basalts and metabasaltic rocks, serpentinized harzburgite and pieces of anhydrite chimney as we proceeded along the track.
On the top of the slope we encountered shells of dead mussels indicating the proximity of hydrothermal activity where they live. Upon following this trail of mussels, we discovered an active, ~4 m high hydrothermal mound covered with white bacterial mats. Several smaller diffuse flows were also observed around the main chimney.
In the main vent temperature measurements of hydrothermal fluids of > 300 °C were recorded. Samples of fluids and vent fauna (mostly shrimps) were recovered. Parts of the chimney itself were also sampled. We also deployed autonomous temperature probes in the main vent and in a diffuse flow nearby, and we will recover them towards the end of the cruise.
Upon surveying the surrounding area another black smoker vent was found, and surely other vents do exist around this area.