Uplift at lithospheric swells-II: is the Cape Verde mid-plate swell supported by a lithosphere of varying mechanical strength?.

Wilson, D. J., Peirce, C., Watts, A. B. and Grevemeyer, Ingo (2013) Uplift at lithospheric swells-II: is the Cape Verde mid-plate swell supported by a lithosphere of varying mechanical strength?. Open Access Geophysical Journal International, 193 (2). pp. 798-819. DOI 10.1093/gji/ggt034.

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Abstract

The Cape Verde mid-plate swell is the largest amplitude oceanic mid-plate swell on Earth at similar to 1800 km in diameter, with a crest similar to 2.2 km high, and long-wavelength positive geoid, gravity and heat flow anomalies of 8 m, 30 mGal and 10 15 mW m(-2), respectively. These characteristics and its location on the slow moving-to-stationary African Plate, which concentrates the volcanism and associated geophysical anomalies within a relatively small areal extent, makes it an ideal location to test various proposed mechanisms for swell support.

Wide-angle seismic refraction data have been acquired along a similar to 474 km profile extending north-south from the swell crest. In this paper, the 2-D velocity-depth crustal model derived from forward modelling of phase traveltime picks is tested using two independent inversion approaches. The final crustal velocity-depth model derived from the combined modelling, shows no evidence for widespread thickened crust or for lower crustal velocities exceeding 7.3 km s(-1) that are indicative of undercrustal magmatic material.

Using the final velocity-depth model to constrain the crust for 3-D 'whole plate' lithospheric flexure modelling of island loading alone, we show that the lithosphere of the Cape Verde region appears stronger than expected for its age. Regional-scale modelling suggests that the majority of the swell height is supported by dynamic upwelling within the asthenosphere coupled with, but to a lesser degree, the effect of a region of low density in the deeper lithosphere, originating most likely from conductive reheating of the overlying plate due to its slow-to-stationary motion. When this regional upward-acting buoyancy force is considered in the context of the shorter wavelength flexure associated with island loading, modelling suggests that the apparent high plate strength is a consequence of, in effect, a regional unbending of a lithosphere that has a long-term strength typical for its age

Document Type: Article
Additional Information: This article has been published in Geophysical Journal International ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Intraplate processes; Oceanic hotspots and intraplate volcanism; Lithospheric flexure; Crustal structure; ISOSTATIC GEOID ANOMALIES; SOUTH-PACIFIC SUPERSWELL; POLARITY TIME-SCALE; HEAT-FLOW; CRUSTAL STRUCTURE; HOTSPOT SWELLS; OCEAN-FLOOR; DEPTH ANOMALIES; CANARY-ISLANDS; NORTH-ATLANTIC
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
Publisher: Wiley
Projects: CHARISMA, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 30 May 2013 12:57
Last Modified: 22 Jan 2019 09:56
URI: https://oceanrep.geomar.de/id/eprint/21341

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