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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B2, 2109, doi:10.1029/2000JB000047, 2003

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

V. M. Tiwari

National Geophysical Research Institute, Hyderabad, India


M. Diament

Institut de Physique du Globe de Paris, Paris, France


S. C. Singh

Institut de Physique du Globe de Paris, Paris, France


Abstract

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.

Published 20 February 2003.

Index Terms: 1219 Geodesy and Gravity: Local gravity anomalies and crustal structure; 1234 Geodesy and Gravity: Regional and global gravity anomalies and Earth structure; 1236 Geodesy and Gravity: Rheology of the lithosphere and mantle (8160).

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Citation: Tiwari, V. M., M. Diament, and S. C. Singh (2003), Analysis of satellite gravity and bathymetry data over Ninety-East Ridge: Variation in the compensation mechanism and implication for emplacement process, J. Geophys. Res., 108(B2), 2109, doi:10.1029/2000JB000047.