Spatial variations of effective elastic thickness over the Ninetyeast Ridge and implications for its structure and tectonic evolution

Kumar, Ratheesh RT and Windley, BF (2013) Spatial variations of effective elastic thickness over the Ninetyeast Ridge and implications for its structure and tectonic evolution. In: TECTONOPHYSICS, 608 . pp. 847-856.

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Abstract

We present new data on the strength of oceanic lithosphere along the Ninetyeast Ridge (NER) from two independent methods: spectral analysis (Bouguer coherence) using the fan wavelet transform technique, and spatial analysis (flexure inversion) with the convolution method. The two methods provide effective elastic thickness (T-e) patterns that broadly complement each other, and correlate well with known surface structures and regional-scale features. Furthermore, our study presents a new high resolution database on the Moho configuration, which obeys flexural isostasy, and exhibit regional correlations with the T-e variations. A continuous ridge structure with a much lower T-e value than that of normal oceanic lithosphere provides strong support for the hotspot theory. The derived T-e values vary over the northern (higher T-e similar to 10-20 km), central (anomalously low T-e similar to 0-5 km), and southern (low T-e similar to 5 km) segments of the NER. The lack of correlation of the T-e value with the progressive aging of the lithosphere implies differences in thermo-mechanical setting of the crust and underlying mantle in different parts of the NER, again indicating diversity in their evolution. The anomalously low T-e and deeper Moho (similar to 22 km) estimates of the central NER (between 0.5 degrees N and 17 degrees S) are attributed to the interaction of a hotspot with the Wharton spreading ridge that caused significant thermal rejuvenation and hence weakening of the lithosphere. The higher mechanical strength values in the northern NER (north of 0.5 degrees N) may support the idea of off-ridge emplacement and a relatively large plate motion at the time of volcanism. The low T-e and deeper Moho (similar to 22 km) estimates in the southern part (south of 17 degrees S) suggest that the lithosphere was weak and therefore younger at the time of volcanism, and this supports the idea that the southern NER was emplaced on the edge of the Indian plate. (C) 2013 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	TECTONOPHYSICS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copyright for this article belongs to the ELSEVIER SCIENCE BV, NETHERLANDS
Keywords:	Ninetyeast Ridge; Effective elastic thickness; Isostasy; Hotspot; Spreading ridge
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	17 Feb 2014 11:02
Last Modified:	17 Feb 2014 11:02
URI:	http://eprints.iisc.ac.in/id/eprint/48389

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