3:30 PM - 4:30 PM
[S14-P-04] Slow recycling of cold slab remnants in vigorous mantle convection
Two dimensional numerical models of mantle convection in a cylindrical shell are employed to investigate the impact of very high viscosities in mid-mantle and lower-mantle depths as proposed by Mitrovica and Forte (2004) and Steinberger and Calderwood (2006). Models are considered with and without mineral phase transitions. Our viscosity profiles are depth dependent with deep mantle viscosities increasing to values of 300 times the viscosity of the upper mantle, and then decreasing dramatically on approaching the core-mantle boundary. The decrease of viscosity near the CMB mobilizes the overall flow despite very high mid-mantle viscosities. However, cold detached slabs sinking below continental collisions become captured by the high viscosity interior and circulate for times exceeding 200 Myr. This may account for the cold patches detected by seismic tomography below India and Mongolia.