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

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

Cleary and Haddon, 1972

Van den Berg, Cloetingh and Doornbos, 1978

Hirose, 2007 Pv/PPv Slope 11 MPa/K, CMB intercept ~3550 K

Boehler, Annu. Rev. Earth Planet. Sci. 1996

Van den Berg, Rainey and Yuen, 2005

Mantel profiles based on a modified Hofmeister (1999) model

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

Crustal markers Spinel/Pv Pv PPv

K_cmb=5 W/(mK)

K_cmb=15 W/(mK)

Single tracer T-depth paths Crustal markers in bottom PV (high k case)

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