Ninetyeast ridge: Magmatism and geodynamics

Abstract

The study of magmatism and tectonic structure of the East Indian or Ninetyeast Ridge (NER) reveals the geochemical similarity of mantle sources for the NER and Kerguelen Plateau melts. Magmas related to the Kerguelen plume were derived from an enriched mantle source, whereas the NER tholeiitic basalts originated from a source contaminated by a depleted material. While, depleted basalt varieties were not found within the NER basalts. It was shown that magmatic rocks forming the NER were generated by high degrees (30%) of partial melting within the ancient Wharton spreading ridge due to the activity of the Kerguelen plume, which was located at this time in the vicinity of the ridge. The most significant impact of the plume on the NER structures was recorded at 70–50 Ma ago.