Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010geoji.182..531w&link_type=abstract
Geophysical Journal International, Volume 182, Issue 2, pp. 531-550.
Astronomy and Astrophysics
Astronomy
Controlled Source Seismology, Intraplate Processes, Oceanic Hotspots And Intraplate Volcanism, Lithospheric Flexure, Crustal Structure
Scientific paper
Wide-angle seismic data have been used to determine the velocity and density structure of the crust and uppermost mantle beneath the Cape Verdes mid-plate swell. Seismic modelling reveals a `standard' oceanic crust, ~8 km in thickness, with no direct evidence for low-density bodies at the base of the crust. Gravity anomaly modelling within the constraints and resolution provided by the seismic model, does not preclude, however, a layer of crustal underplate up to 3 km thick beneath the swell crest. The modelling shows that while the seismically constrained crustal structure accounts for the short-wavelength free-air gravity anomaly, it fails to fully explain the long-wavelength anomaly. The main discrepancy is over the swell crest where the gravity anomaly, after correcting for crustal structure, is higher by about 30 mGal than it is over its flanks. The higher gravity can be explained if the top 100 km of the mantle beneath the swell crest is less dense than its surroundings by 30 kg m-3. The lack of evidence for low densities and velocities in the uppermost mantle, and high densities and velocities in the lower crust, suggests that neither a depleted swell root or crustal underplate are the origin of the observed shallower-than-predicted bathymetry and that, instead, the swell is most likely supported by dynamic uplift associated with an anomalously low density asthenospheric mantle.
Grevemeyer Ingo
Krabbenhoeft A.
Peirce Christine
Watts A. B.
Wilson Dalziel J.
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