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| Titel |
The deep lithospheric structure of the Namibian volcanic margin |
| VerfasserIn |
Manuel Fernandez, Juan Carlos Afonso, Giorgio Ranalli |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038990
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| Zusammenfassung |
| A model of the thermal, compositional, density, and seismological structure of the
lithospheric and sublithospheric mantle along a 500-km transect across the Namibian
volcanic passive margin is presented. This margin juxtaposes old oceanic lithosphere and a
Precambrian continental domain. The model combines within an internally consistent
framework data from petrology, mineral physics, and geophysical observables. The calculated
mantle temperature and density distributions down to a depth of 400 km are consistent with
available xenolith-derived data, and fit simultaneously the observed free-air anomaly, geoid
height, surface heat flow, and elevation. The model also explains the anomalously thick
oceanic crust and the depletion of the lithospheric mantle in the ocean-continent
transition and in the Proterozoic continental domain. Seismic velocities predicted by
the present model are in good agreement with values obtained from wide angle
reflection/refraction and tomography experiments. The thermal lithospheric thickness
is ~100 km in the oceanic domain, increasing gradually to ~125 km across the
ocean-continent transition and then more sharply to ~175 km in the continental
domain. The density distribution in the mantle differs significantly from current purely
thermal approaches where density is assumed to be only temperature-dependent.
Non-negligible compositional density differences are encountered between the oceanic,
transitional, and continental domains. Results show that non-thermal effects such as
composition and phase changes cannot be neglected in models of the upper mantle. |
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