Paleocene on-spreading-axis hotspot volcanism along the Ninetyeast Ridge: An interaction between the Kerguelen hotspot and the Wharton spreading center |
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Authors: | K S Krishna D Gopala Rao L V Subba Raju A K Chaubey V S Shcherbakov A I Pilipenko I V Radhakrishna Murthy |
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Institution: | (1) National Institute of Oceanography, 403 004 Dona Paula, Goa, India;(2) Yuzhmorgeologia, Galendzhik, Russia;(3) Department of Geophysics, Andhra University, 530 003 Visakhapatnam, India |
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Abstract: | Investigations of three plausible tectonic settings of the Kerguelen hotspot relative to the Wharton spreading center evoke
the on-spreading-axis hotspot volcanism of Paleocene (60-54 Ma) age along the Ninetyeast Ridge. The hypothesis is consistent
with magnetic lineations and abandoned spreading centers of the eastern Indian Ocean and seismic structure and radiometric
dates of the Ninetyeast Ridge. Furthermore, it is supported by the occurrence of oceanic andesites at Deep Sea Drilling Project
(DSDP) Site 214, isotopically heterogeneous basalts at Ocean Drilling Program (ODP) Site 757 of approximately the same age
(59-58 Ma) at both sites. Intermix basalts generated by plume-mid-ocean ridge (MOR) interaction, exist between 11° and 17°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 similarly aged oceanic crust in the Central Indian Basin and Wharton Basin reveals the existence of extra oceanic
crust spanning 11° latitude beneath the Ninetyeast Ridge. The extra crust is attributed to the transfer of lithospheric blocks
from the Antarctic plate to the Indian plate through a series of southward ridge jumps at about 65, 54 and 42 Ma. Emplacement
of volcanic rocks on the extra crust resulted from rapid northward motion (absolute) of the Indian plate. The Ninetyeast Ridge
was originated when the spreading centers of the Wharton Ridge were absolutely moving northward with respect to a relatively
stationary Kerguelen hotspot with multiple southward ridge jumps. In the process, the spreading center coincided with the
Kerguelen hotspot and took place on-spreading-axis volcanism along the Ninetyeast Ridge. |
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Keywords: | Ninetyeast Ridge Kerguelen hotspot Wharton Ridge on-axis volcanism ridge jumps crustal transfer extra oceanic crust |
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