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Evidence for high temperature in the upper mantle beneath Cape Verde archipelago from Rayleigh-wave phase-velocity measurements

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doi: 10.1016/j.tecto.2019.228225
Authors:Carvalho, Joana; Bonadio, Raffaele; Silveira, Graça; Lebedev, Sergei; Mata, Joao; Arroucau, Pierre; Meier, Thomas; Celli, Nicolas L.
Author Affiliations:Primary:
Universidade de Lisboa, Instituto Dom Luiz, Lisbon, Portugal
Other:
Dublin Institute for Advanced Studies, School of Cosmic Physics, Dublin, Ireland
EDF/DI/TEGG, Seismic Hazard Group, Aix-en-Provence, France
Christian-Albrechts University Kiel, Institute of Geosciences, Kiel, Germany
Volume Title:Tectonophysics
Source:Tectonophysics, Vol.770. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0040-1951
Publication Date:2019
Note:In English. 73 refs.; illus., incl. geol. sketch maps
Summary:Cape Verde is an intraplate archipelago located in the Atlantic Ocean about 560 km west of Senegal, on an ∼ 130 Ma old oceanic lithosphere. The upper-mantle structure beneath the islands was poorly known, until recently, in large part due to the lack of broadband seismic stations. In this study we used data from two temporary deployments across the archipelago, measuring the phase velocities of Rayleigh-waves fundamental-modes in a broad period range (8-250 s), by cross-correlating teleseismic earthquake data between pairs of stations. We derived a robust average, phase-velocity curve for the Cape Verde region, and inverted it for a shear-wave velocity profile. Our results show significantly low velocities of ∼ 4.2 km/s in the asthenosphere, indicating the presence of anomalously high temperatures and, eventually, partial melting. The temperature anomaly is probably responsible for the thermal rejuvenation of the lithosphere to an effective age as young as about 30 Ma, which we infer from the comparison of seismic velocities beneath Cape Verde archipelago and those representative of different ages in the Central Atlantic. The anomalously high temperature in the asthenosphere, together with previously published evidence on low seismic velocities in the lower mantle and relatively He-unradiogenic isotopic ratios, suggests a hot plume, rooted deep in the lower mantle, as the origin of the Cape Verde hotspot.
Subjects:Asthenosphere; Body waves; Crosscorrelation; Elastic waves; Geophysical methods; Guided waves; High temperature; Hot spots; Lithosphere; Mantle; Mantle plumes; Phase velocity; Plate tectonics; Rayleigh waves; S-waves; Seismic methods; Seismic networks; Seismic waves; Statistical analysis; Surface waves; Temperature; Thermal anomalies; Upper mantle; Africa; Atlantic Ocean Islands; Cape Verde Islands
Coordinates:N140000 N180000 W0210000 W0270000
Record ID:867961-6
Copyright Information:GeoRef, Copyright 2020 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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