Paleocene on-spreading-axis hotspot volcanism along the Ninetyeast Ridge: An interaction between the Kerguelen hotspot and the Wharton spreading center

Investigations of three plausible tectonic settings of the Kerguelen hotspo t relative to the Wharton spreading center evoke the on-spreading-axis hots pot volcanism of Paleocene (60-54 Ma) age along the Ninetyeast Ridge. The h ypothesis is consistent with magnetic lineations and abandoned spreading ce nters of the eastern Indian Ocean and seismic structure and radiometric dat es of the Ninetyeast Ridge. Furthermore it is supported by the occurrence o f oceanic andesites at Deep Sea Drilling Project (DSDP) Site 214, isotopica lly heterogeneous basalts at Ocean Drilling Program (ODP) Site 757 of appro ximately the same age (59-58Ma) at both sites. Intermix basalts:generated b y plume-mid-ocean ridge (MOR) interaction,exist between 11 degrees and 17 d egrees S along the Ninetyeast Ridge. A comparison of age profile along the Ninetyeast Ridge between ODP Sites 758 (82 Ma) and 756 (43 Ma) with similar ly aged oceanic crust in the Central Indian Basin and Wharton Basin reveals the existence of extra oceanic crust spanning 11 degrees latitude beneath the Ninetyeast Ridge. The extra crust is attributed to the transfer of lith ospheric blocks from the Antarctic plate to the Indian plate through a seri es of southward ridge jumps at about 65, 54 and 42 Ma. Emplacement of volca nic rocks on the extra crust resulted from rapid northward motion (absolute ) of the Indian plate. The Ninetyeast Ridge was originated when the spreadi ng centers of the Wharton Ridge were absolutely moving northward with respe ct to a relatively stationary Kerguelen hotspot with multiple southward rid ge jumps. In the process, the spreading center coincided with the Kerguelen : hotspot and took place on-spreading-axis volcanism along the Ninetyeast R idge.