TY  - JOUR
A1  - Mulyukova, Elvira
A1  - Steinberger, Bernhard
A1  - Dabrowski, Marcin
A1  - Sobolev, Stephan Vladimir
T1  - Survival of LLSVPs for billions of years in a vigorously convecting mantle: Replenishment and destruction of chemical anomaly
JF  - Journal of geophysical research : Solid earth
N2  - We study segregation of the subducted oceanic crust (OC) at the core-mantle boundary and its ability to accumulate and form large thermochemical piles (such as the seismically observed Large Low Shear Velocity Provinces (LLSVPs)). Our high-resolution numerical simulations of thermochemical mantle convection suggest that the longevity of LLSVPs for up to three billion years, and possibly longer, can be ensured by a balance in the rate of segregation of high-density OC material to the core-mantle boundary (CMB) and the rate of its entrainment away from the CMB by mantle upwellings. For a range of parameters tested in this study, a large-scale compositional anomaly forms at the CMB, similar in shape and size to the LLSVPs. Neutrally buoyant thermochemical piles formed by mechanical stirringwhere thermally induced negative density anomaly is balanced by the presence of a fraction of dense anomalous materialbest resemble the geometry of LLSVPs. Such neutrally buoyant piles tend to emerge and survive for at least 3Gyr in simulations with quite different parameters. We conclude that for a plausible range of values of density anomaly of OC material in the lower mantleit is likely that it segregates to the CMB, gets mechanically mixed with the ambient material, and forms neutrally buoyant large-scale compositional anomalies similar in shape to the LLSVPs.
KW  - LLSVPs
KW  - thermochemical modeling
KW  - segregating oceanic crust
KW  - mantle convection
Y1  - 2015
U6  - https://doi.org/10.1002/2014JB011688
SN  - 2169-9313
SN  - 2169-9356
VL  - 120
IS  - 5
SP  - 3824
EP  - 3847
PB  - American Geophysical Union
CY  - Washington
ER  -