Hydrothermal plumes over the Carlsberg Ridge, Indian Ocean
Date
2012Author
Ray, D.
KameshRaju, K.A.
Baker, E.T.
Rao, A.S.
Mudholkar, A.V.
Lupton, J.E.
SuryaPrakash, L.
Gawas, R.B.
VijayaKumar, T.
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Water column surveys and sampling in 2007 and 2009 was conducted to search for hydrothermal plumes over a segment of the Carlsberg Ridge. An evidence for two separate vent fields, one near 3 degrees 42′N, 63 degrees 40′E and another near 3 degrees 41.5′N, 63 degrees 50′E, on a segment that is apparently sparsely magmatic is reported. Both sites appear to be located on off-axis highs at the top of the southern axial valley wall, at depths of approx 3600 m or shallower (approx 1000 m above the valley floor). At the 63 degrees 40′E site, plume sampling found local maxima in light scattering, temperature anomaly, oxidation-reduction potential (ORP), dissolved Mn, and 3He. No water samples are available from the 63 degrees 50′E site, but it showed robust light-scattering and ORP anomalies at multiple depths, implying multiple sources. ORP anomalies are very short-lived, so the strong signals at both sites suggest that fluid sources lie within a few kilometers or less from the plume sampling locations. Although ultramafic rocks have been recovered near these sites, the light-scattering and dissolved Mn anomalies imply that the plumes do not arise from a system driven solely by exothermic serpentinization (e.g., Lost City). Instead, the source fluids may be a product of both ultramafic and basaltic/gabbroic fluid-rock interaction, similar to the Rainbow and Logatchev fields on the Mid-Atlantic Ridge.
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