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Eclogite in the upper mantle? chemical heterogeneities and seismology PowerPoint Presentation
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Eclogite in the upper mantle? chemical heterogeneities and seismology

Eclogite in the upper mantle? chemical heterogeneities and seismology

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Eclogite in the upper mantle? chemical heterogeneities and seismology

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  1. Eclogite in the upper mantle? chemical heterogeneities and seismology Sebastian Rost DEEP 23. Februar 2005

  2. The recycling Factory

  3. Geodynamics • depth and temperature dependent • viscosity • - 2 moving/subducing plates • - 1 stationary continent • - tracers = geochemical heterogeneity • passive tracers • periodic side boundaries • greyscale = viscosity Davies (2002)

  4. Convection Movie Supplemental material movie 1 • 2 oceanic plates – 1 continental plate • subduction under stationary continent • migration of subduction zones • buckling under higher viscosity in lower mantle • dark – high viscosity light – low viscosity • stiff runny Davies (2002)

  5. Passive stirring Insert supplemental material 2 • tracers throughout the model - orange • subducted tracers – black • ULVZ material (20 km) – purple • 4 time segments: 4, 3, 2 Ga ago – present • 97 % of tracers processed Davies (2002)

  6. Heavy tracers Supplemental material 3 • tracer are slightly heavy • 2 time segments: early – late • accumulation of tracers at the bottom • plumes high in incompatible elements Davies (2002)

  7. Snapshots Davies (2002)

  8. Seismological Snapshots Model by Grand (2002)

  9. Array Seismology: Vespagram Incidence Angle Phase-weighted stack Time

  10. Stacking Stacks • sliding time window (~1s) • select highest amplitude in each • time slice • timing – amplitude - slowness time Condensing information into one trace

  11. Stacking Stacks ~ 500 events stacked

  12. Stacking Stacks

  13. Stacking Stacks

  14. Stacking Stacks

  15. PP raypaths Information about Reflection point

  16. Single vespagram – Phase weighted stack

  17. Raw seismogram – Beam trace

  18. Scattered PP energy

  19. 1-D Earth models

  20. 1-D model IASP

  21. 1-D model LAMELLAE

  22. Further modelling Axisymmetric acoustic code – Thomas and Igel (2000) • Multidomain setup • Staggered grid • Acoustic – P-waves only • Center – cartesian Thomas et al. (2000)

  23. Conclusions • PP data shows evidence for scatterers in the upper 200 km of mantle. • High-frequency data – scatterer size ~10 - 20 km (?). • Lumps of recycled crust at this depth? • Why just there ? What happens below 200 km ? • Array seismology give slowness information. • Better modeling possible. • Modeling possible by using slowness, timing and amplitude info. • 1D Lamellae point in the right direction. • Acoustic wavepropagation will give further clues. • Statistical description of seismic properties.