Analysis of satellite gravity and bathymetry data over Ninety-East Ridge: Variation in the compensation mechanism and implication for emplacement process

V.M. Tiwari (1) , M Diament (2) , S. C. Singh (2)

1 National Geophysical Research Institute [Hyderabad]
2 IPGP - Institut de Physique du Globe de Paris

We investigate the mode of compensation, emplacement history and deep density structure of the Ninety-East Ridge (Indian Ocean) using spectral analyses and forward modeling of satellite gravity and bathymetry data. We find that the northern (0–10°N) and the southern (20–30°S) parts of the ridge are flexurally compensated with an effective elastic thickness >15 km, whereas the central part (0–20°S) is locally compensated. Furthermore, we find that for a part of central block (10–20°S, over Osborn Knoll) the compensation depth is unreasonably very high (30–40 km). Therefore we favor a model with subsurface loading and interpret this to be due to underplating of mafic material at the base of the crust, a hypothesis that is supported by seismic results and direct modeling of gravity data along some profiles. These results suggest that the northern and southern parts of Ninety-East Ridge were emplaced off to a ridge axis compared to the central one, which might have been emplaced on or near a spreading center. Locally compensated large topography, thick underplated crust in the central part (near Osborn Knoll), might result from an interaction of a hot spot with the extinct Wharton spreading ridge.

Domaines: Géophysique [physics.geo-ph]

V.M. Tiwari, M Diament, S. C. Singh. Analysis of satellite gravity and bathymetry data over Ninety-East Ridge: Variation in the compensation mechanism and implication for emplacement process. Journal of Geophysical Research : Solid Earth, 2003, 108 (B2), ⟨10.1029/2000JB000047⟩. ⟨insu-01356385⟩