Seismological Seismological observations Earth’s observations Earth’s deep interior, deep interior, and their geodynamical and their geodynamical and mineral physical and mineral physical interpretation interpretation Arwen Deuss, Jennifer Andrews Arwen Deuss, Jennifer Andrews University of Cambridge, UK University of Cambridge, UK John Woodhouse John Woodhouse University of Oxford, UK University of Oxford, UK
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Seismological observations Earth’s deep interior, and their geodynamical and mineral physical interpretation Arwen Deuss, Jennifer Andrews University of.
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Seismological observations Seismological observations Earth’s deep interior, Earth’s deep interior,
and their geodynamical and and their geodynamical and mineral physical interpretationmineral physical interpretation
Arwen Deuss, Jennifer AndrewsArwen Deuss, Jennifer AndrewsUniversity of Cambridge, UKUniversity of Cambridge, UK
John WoodhouseJohn WoodhouseUniversity of Oxford, UKUniversity of Oxford, UK
Global tomographyGlobal tomography
Velocity heterogeneity inthe Earth:
* thermal in origin?* also chemical/compositional heterogeneity?* lithosphere/asthenosphere boundary?* what happens in the transition zone?* where do slabs go?Ritsema, van Heijst & Woodhouse (1999)
Mantle discontinuitiesMantle discontinuities
mineral physics
Seismology
seismology
(Deuss & Woodhouse, GRL, 2002)
Two different data types …Two different data types …
* reflected waves* both continents and oceans
* converted waves* only beneath stations
Transition zone PrecursorsTransition zone Precursors
ConclusionsConclusions* to explain the seismic observations of transition zone * to explain the seismic observations of transition zone
discontinuities, we need phase transitions in garnet in discontinuities, we need phase transitions in garnet in addition to the olivine phase transitions (consistent with a addition to the olivine phase transitions (consistent with a pyrolite mantle model )pyrolite mantle model )
* lateral variations in minor elements are also required, * lateral variations in minor elements are also required, which will influence slab penetration and upwelling of which will influence slab penetration and upwelling of mantle plumes differently from region to regionmantle plumes differently from region to region
* significant amount of seismic scatterers in upper and * significant amount of seismic scatterers in upper and lower mantle, without a mineral physical explanation in lower mantle, without a mineral physical explanation in the lower mantlethe lower mantle
* focus research towards discoveries in mineral physics, i.e. * focus research towards discoveries in mineral physics, i.e. discontinuities in attenuation, free silica lower mantle, discontinuities in attenuation, free silica lower mantle, mechanical mixture vs. equilibrium mechanical mixture vs. equilibrium