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| Titel |
Heterogeneous distribution of mineral phases and seismic velocity in the transition zone from convection modelling based on selfconsistent thermodynamics |
| VerfasserIn |
Michel Jacobs, Arie van den Berg |
| 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 |
250035390
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| Zusammenfassung |
| We have modelled convection in the Earth’s mantle using a selfconsistent thermodynamical
model for an olivine-pyroxene composition in the SiO2, MgO system. The thermodynamic
model is based on a lattice vibrational method allowing the calculation of density, thermal
expansion, compressibility, specific heat, phase equilibria and seismic velocities in the
complete P-T regime of the Earth’s mantle.
Our modelling results show a complex structure in the behavior of physical properties, in
particular the seismic shear velocity, in the depth range of the mantle transition zone,
400-660 km. We demonstrate that this behavior is related to the distribution of mineral
phases in the olivine-pyroxene system. Especially near cold downwelling flows,
representing subducting lithopheric plates, the results of our model show strong lateral
variation of mineral phases and associated shear velocity. We show that, typically,
pockets of contrasting mineral phases smaller than 100 km occur in subduction
regions.
In line with current developments in seismic imaging of the mantle transition zone we
have computed reflectivity profiles from the shear velocity distribution obtained from the
convection results. We applied frequency filtering to the raw reflectivity data to investigate the
requirements for resolving the heterogenous structure of the transition zone. Our results show
that heterogeneous structure from contrasting mineral phase regions is resolved for
periods of ten seconds which may be feasible in seismic imaging applications. |
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