Farra, Veronique

Kiselev, Sergei

Silveira, Graça

Stutzmann, Eleonore

Vinnik, Lev

Weber, Michael

Earth and Planetary Science Letters

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Cape Verde hotspot from the upper crust to the top of the lower mantle

We investigate the crust, upper mantle and mantle transition zone of the Cape Verde hotspot by using seismic P and S receiver functions from several tens of local seismograph stations. We find a strong discontinuity at a depth of similar to 10 km underlain by a similar to 15-km thick layer with a high (similar to 1.9) Vp/Vs velocity ratio. We interpret this discontinuity and the underlying layer as the fossil Moho, inherited from the pre-hotspot era, and the plume-related magmatic underplate. Our uppermost-mantle models are very different from those previously obtained for this region: our S velocity is much lower and there are no indications of low densities. Contrary to previously published arguments for the standard transition zone thickness our data indicate that this thickness under the Cape Verde islands is up to similar to 30 km less than in the ambient mantle. This reduction is a combined effect of a depression of the 410-km discontinuity and an uplift of the 660-km discontinuity. The uplift is in contrast to laboratory data and some seismic data on a negligible dependence of depth of the 660-km discontinuity on temperature in hotspots. A large negative pressure-temperature slope which is suggested by our data implies that the 660-km discontinuity may resist passage of the plume. 

Our data reveal beneath the islands a reduction of S velocity of a few percent between 470-km and 510-km depths. The low velocity layer in the upper transition zone under the Cape Verde archipelago is very similar to that previously found under the Azores and a few other hotspots. In the literature there are reports on a regional 520-km discontinuity, the impedance of which is too large to be explained by the known phase transitions. Our observations suggest that the 520-km discontinuity may present the base of the low-velocity layer in the transition zone. (C) 2011 Elsevier B.V. All rights reserved

Repositório Científico do Instituto Politécnico de Lisboa

ISEL – Instituto Superior de Engenharia de Lisboa    SDP - Serviço de Documentação e Publicações  Title: Cape Verde hotspot from the upper crust to the top of the lower mantle Author(s):  Vinnik, Lev1;  Silveira, Graça2,3;  Kiselev, Sergei1;  Farra, Veronique4;  Weber, Michael5,6; Stutzmann, Eleonore4 Source: Earth and Planetary Science Letters  Volume: 319   Pages: 259-268   DOI: 10.1016/j.epsl.2011.12.017   Published: Feb 15 2012 Document Type: Article Language: English Abstract: We investigate the crust, upper mantle and mantle transition zone of the Cape Verde hotspot by using seismic P and S receiver functions from several tens of local seismograph stations. We find a strong discontinuity at a depth of similar to 10 km underlain by a similar to 15-km thick layer with a high (similar to 1.9) Vp/Vs velocity ratio. We interpret this discontinuity and the underlying layer as the fossil Moho, inherited from the pre-hotspot era, and the plume-related magmatic underplate. Our uppermost-mantle models are very different from those previously obtained for this region: our S velocity is much lower and there are no indications of low densities. Contrary to previously published arguments for the standard transition zone thickness our data indicate that this thickness under the Cape Verde islands is up to similar to 30 km less than in the ambient mantle. This reduction is a combined effect of a depression of the 410-km discontinuity and an uplift of the 660-km discontinuity. The uplift is in contrast to laboratory data and some seismic data on a negligible dependence of depth of the 660-km discontinuity on temperature in hotspots. A large negative pressure-temperature slope which is suggested by our data implies that the 660-km discontinuity may resist passage of the plume.   Our data reveal beneath the islands a reduction of S velocity of a few percent between 470-km and 510-km depths. The low velocity layer in the upper transition zone under the Cape Verde archipelago is very similar to that previously found under the Azores and a few other hotspots. In the literature there are reports on a regional 520-km discontinuity, the impedance of which is too large to be explained by the known phase transitions. Our observations suggest that the 520-km discontinuity may present the base of the low-velocity layer in the transition zone. (C) 2011 Elsevier B.V. All rights reserved. Author Keywords: Hotspot; Plume; Crust; Upper Mantle; Mantle Transition Zone; Receiver Function KeyWords Plus: S Receiver Functions; Transition Zone; Earths Mantle; Waves; Plume ; Discontinuity; Beneath; Depth; Stratification; Tomography  Reprint Address: Vinnik, L (reprint author), Inst Phys Earth, B Grouzinskaya 10, Moscow 123995, Russia. Addresses:  1. Inst Phys Earth, Moscow 123995, Russia  2. Inst Dom Luiz, P-1749016 Lisbon, Portugal  3. Inst Super Engn Lisboa, Area Cient Fis, P-1959007 Lisbon, Portugal  4. CNRS, Inst Phys Globe Paris, UMR 7154, F-75005 Paris, France  5. Deutsch GeoForschungsZentrum, Potsdam, Germany  6. Univ Potsdam, Inst Erd & Umweltwissensch, Potsdam, Germany ISEL – Instituto Superior de Engenharia de Lisboa    SDP - Serviço de Documentação e Publicações  E-mail Address: vinnik@ifz.ru Funding: Funding Agency Grant Number CV-PLUME  PTDC/CTE-GIN/64330/2006  COBO    RFBR  10-05-00879    Pest-OE/CTE/LA0019/2011 - IDL    Publisher: Elsevier Science BV Publisher Address: PO Box 211, 1000 AE Amsterdam, Netherlands ISSN: 0012-821X Citation: Vinnik L, Silveira G, Kiselev S, Farra V, Weber M, Stutzman E. Cape Verde hotspot from the upper crust to the top of the lower mantle. Earth and Planetary Science Letters. 2012; (319): 259-268.  

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Cape Verde hotspot from the upper crust to the top of the lower mantle

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