Variation in bridgmanite grain size accounts for the mid-mantle viscosity jump.

ABSTRACT: A viscosity jump of one to two orders of magnitude in the lower mantle of Earth at 800-1,200-km depth is inferred from geoid inversions and slab-subducting speeds. This jump is known as the mid-mantle viscosity jump^1,2. The mid-mantle viscosity jump is a key component of lower-mantle dynamics and evolution because it decelerates slab subduction³, accelerates plume ascent⁴ and inhibits chemical mixing⁵. However, because phase transitions of the main lower-mantle minerals do not occur at this depth, the origin of the viscosity jump remains unknown. Here we show that bridgmanite-enriched rocks in the deep lower mantle have a grain size that is more than one order of magnitude larger and a viscosity that is at least one order of magnitude higher than

SUBMITTER: Fei H 

PROVIDER: S-EPMC10447242 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature