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| Titel |
Probing the upper mantle transition zone under Africa with P520s conversions: Implications for temperature and composition. |
| VerfasserIn |
J. Julià, A. A. Nyblade |
| 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 |
250061164
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| Zusammenfassung |
| We have investigated the nature of the 520 km discontinuity under Africa
by migrating P-wave receiver functions at twenty-four permanent broadband
stations in the continent. Worldwide investigations with S520S underside
reflections have revealed that this discontinuity is intermittent and that
it may split into two separate discontinuities, ~60 km apart, in some
regions. Several explanations have been proposed to explain both the
intermittency and splitting of the 520-km discontinuity, ranging from local
temperature variations in the upper mantle to compositional variations due
to changes in minor phases containing Fe and Ca and/or other trace elements
such as water. Our results reveal that the 520 km discontinuity is
intermittent under Africa and that - when observed - it does not split.
Moreover, local estimates of transition zone temperature inferred from
transition zone thicknesses reveal that intermittency of the 520 km
discontinuity does not correlate with temperature. The lack of splitting is
consistent with low Ca concentrations in the African transition zone due to
a general absence of subduction zones around the continent. The
intermittency is harder to explain, but the lack of correlation with
lateral temperature variations suggests it is mainly driven by lateral
variations in trace element contents. |
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