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Convection modeling of the postperovskite transition and constraints on the thermal
conditions near the core mantle boundary
Arie van den Berg, Utrecht University
David Yuen, University of Minnesota
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Outline
• Seismic observations of irregular D” old and new
• Interpretation related to Pv/PPv transition
> estimate thermal conditions near CMB
• Modelling results of slab interaction with Pv/PPv
feasibility of heat flow estimates and thermal conductivity
• Conclusions
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Cleary and Haddon, 1972
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Van den Berg, Cloetingh and Doornbos, 1978
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Hirose, 2007
Pv/PPv Slope 11 MPa/K,CMB intercept ~3550 K
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Boehler, Annu. Rev. Earth Planet. Sci. 1996
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Van den Berg, Rainey and Yuen, 2005
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Mantel profiles based on a modified Hofmeister (1999) model
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model of subducting slab interacting with the PV/PPv zone of D”
• Extended Boussinesq – ppv phase boundary• T,P dep.visc. dv_T=1000, dv_P=100• Layered piecewise uniform thermal conductivity • 2D domain 3000X3000km
- element resolution down to 5 km near CMB• Crustal (100) marker chain
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Crustal markers
Spinel/Pv
Pv
PPv
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K_cmb=5 W/(mK)
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K_cmb=5 W/(mK)
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K_cmb=5 W/(mK)
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K_cmb=15 W/(mK)
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K_cmb=15 W/(mK)
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K_cmb=15 W/(mK)
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Single tracer T-depth paths
Crustal markers in bottom PV(high k case)
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Some conclusions
- Precursors to PKP from small scale scatterers near CMB can be
related to heterogeneity in the Pv/PPv region due to complex
phase distribution and/or crustal remnants
- PPv linked to D” allows temperature estimates near CMB from
seismic mapping of PPv > Pv in the thermal boundary layer
- Heatflow estimates based on simple linear T profiles are feasible
but require better constraints of k_cmb