Article révisé par les pairs
Résumé : Data and observation from Ocean Drilling Program Leg 121 and plate-tectonic reconstructions indicate that the Ninetyeast Ridge was derived from the interaction of a deep-seated Dupal hotspot and a nearby spreading-ridge axis. The 5000-km-long ridge, from lat 34°S to lat 10°N, was drilled at three sites. Each site has distinctive characteristics. Most of the cored lavas have a tholeiitic basalt composition. Incompatible-element abundances and ratios show systematic trends, consistent with an origin for the Ninetyeast Ridge lavas by mixing between a depleted component - Indian Ocean mid-ocean ridge basalt - and an enriched component - oceanic-island basalt similar to that observed in the youngest alkalic basalts from the Kerguelen archipelago. Preliminary shore-based trace element abundance and isotopic data are compatible with this hypothesis, although Pb isotopes indicate the involvement of another component. -from Authors