Hydrothermal plume along the northern Central Indian Ridge, 8°S - 17°S: Magmatic and tectonic control on hydrothermal activity at slow-spreading ridge

Abstract

CTD/MAPR profiles collected on 118 vertical casts on the slow-spreading Central Indian Ridge (8°S&#8211 17°S) reveal that hydrothermal plumes were most commonly associated with the asymmetric ridge sections where ultramafic massifs formed along one ridge flank near ridge-transform intersections or nontransform offsets (NTOs). The combined plume incidence for axial and valley wall casts, ph=0.30, is consistent with the existing global trend. This agreement confirms that thelong-term magmatic budget of the CIR is the primary control on the spatial frequency of hydrothermal venting at this slow spreading ridge. Because plume frequency was higher along asymmetrical than symmetrical ridge sections, permeability likely controls where venting is expressed. The occurrence of hydrothermal plumes at six locations on the axial flanks indicates that such cooling can also produce vent sites far off axis, perhaps fed by fluids channeled along detachment faults.ed along one ridge flank near ridge-transform intersections or nontransform offsets (NTOs). The combined plume incidence for axial and valley wall casts, ph=0.30, is consistent with the existing global trend. This agreement confirms that thelong-term magmatic budget of the CIR is the primary control on the spatial frequency of hydrothermal venting at this slow spreading ridge. Because plume frequency was higher along asymmetrical than symmetrical ridge sections, permeability likely controls where venting is expressed. The occurrence of hydrothermal plumes at six locations on the axial flanks indicates that such cooling can also produce vent sites far off axis, perhaps fed by fluids channeled along detachment faults.