Discovery of active and inactive hydrothermal vents along the northern Central Indian Ridge

Abstract

Plume distribution in the northern Central Indian Ridge between 8°S and 12°S revealed that hydrothermal plumes were most commonly associated with the asymmetrical ridge sections where ultramafic massifs formed along one ridge flank near ridge-transform intersections or non-transform offsets, although long-term magmatic budget of the CIR is still the primary control on the spatial frequency of hydrothermal venting at this slow spreading ridge. During the seafloor observation targeted to several plume locations in the northern segment of CIR between 8°S and 12°S, we identified new active and inactive vent fields at three locations. Inactive chimney clusters were found at the topographic depression parallel to the spreading axis, associated with the formation of ocean core complex (OCC), in western flank of segment 1. Although only inactive chimneys were observed, multi-proxy plume signals indicate possible presence of active venting in segment1. Another two hydrothermal fields were found on typical abyssal hill of symmetrical section in segment 2 at different depths of ~2500 m and ~2900 m, respectively. Although most chimneys are inactive in the segment 2, active venting of shimmering fluid was observed in few chimney structures. Despite of the distance up to 9 km from the spreading axis, the vent fields were formed on the basaltic basement. An active vent field with abundant benthic organisms was found at the sum