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| Titel |
Architecture of the Cape Verde hotspot: implications for properties of the transition zone |
| VerfasserIn |
L. Vinnik, G. Silveira, S. Kiselev, V. Farra, M. Weber, E. Stutzman |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065693
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| Zusammenfassung |
| We investigated 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. Contrary to previously published arguments for the standard transition zone thickness (the separation in depths between the 660-km and 410-km discontinuities) our data indicate that this thickness under the Cape Verde islands is up 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. Horizontal dimensions of the uplift are in a range of several hundreds kilometers. The uplift is in a 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 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 Capo 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. |
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