Enhanced convection and fast plumes in the lower mantle induced by the spin transition in ferropericlase.

Journal Article · Thu May 28 04:00:00 EDT 2009 · Geophys. Res. Lett.

DOI:https://doi.org/10.1029/2009GL037706· OSTI ID:960364

Bower, D J; Gurnis, M; Jackson, J M; Sturhahn, W

Using a numerical model we explore the consequences of the intrinsic density change ({Delta}{rho}/{rho} {approx} 2-4%) caused by the Fe{sup 2+} spin transition in ferropericlase on the style and vigor of mantle convection. The effective Clapeyron slope of the transition from high to low spin is strongly positive in pressure-temperature space and broadens with high temperature. This introduces a net spin-state driving density difference for both upwellings and downwellings. In 2-D cylindrical geometry spin-buoyancy dominantly enhances the positive thermal buoyancy of plumes. Although the additional buoyancy does not fundamentally alter large-scale dynamics, the Nusselt number increases by 5-10%, and vertical velocities by 10-40% in the lower mantle. Advective heat transport is more effective and temperatures in the core-mantle boundary region are reduced by up to 12%. Our findings are relevant to the stability of lowermost mantle structures.

• Research Organization: Argonne National Laboratory (ANL)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 960364
• Report Number(s): ANL/XSD/JA-64165
• Journal Information: Geophys. Res. Lett., Journal Name: Geophys. Res. Lett. Journal Issue: May 28, 2009 Vol. 36; ISSN GPRLAJ; ISSN 0094-8276
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

58 GEOSCIENCES
ADVECTION
CONVECTION
EARTH CORE
EARTH MANTLE
INTERFACES
IRON COMPOUNDS
MINERALS
NUSSELT NUMBER
PLUMES
SPIN
STABILITY