Effects of low-viscosity post-perovskite on the stability and structure of primordial reservoirs in the lower mantle

We performed numerical experiments of thermochemical convection in 3‐D spherical geometry to investigate the effects of a low viscosity of post‐perovskite (pPv) on the stability and structure of primordial reservoirs of dense material in the lower mantle of the Earth. Our results show that weak pPv...

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Bibliographic Details
Published in:Geophysical research letters 2014-10, Vol.41 (20), p.7089-7097
Main Authors: Li, Yang, Deschamps, Frédéric, Tackley, Paul J.
Format: Article
Language:English
Subjects:
Age
Banks (topography)
Convection
Core-mantle boundary
Earth
Earth mantle
Entrainment
Geochemistry
Geophysics
Heat
Heat flux
Heat transfer
Lower mantle
mantle convection
Mathematical models
Numerical experiments
Perovskite
post-perovskite
Reservoirs
Slabs
Slope
Slopes
Spreading
Stability
Temperature
Temperature effects
Topography
Topography (geology)
Viscosity
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Summary:We performed numerical experiments of thermochemical convection in 3‐D spherical geometry to investigate the effects of a low viscosity of post‐perovskite (pPv) on the stability and structure of primordial reservoirs of dense material in the lower mantle of the Earth. Our results show that weak pPv (1000× viscosity reduction in regions containing pPv) strongly increases the core‐mantle boundary (CMB) heat flux. The volume‐averaged mantle temperature with weak pPv is slightly higher than that with regular pPv, except in the lowermost mantle. This is because weak pPv weakens the base of the cold downwellings, allowing cold slabs to spread more easily and broadly along the CMB. The stability and size of the dense reservoirs is not substantially altered by weak pPv. In the weak pPv case, slabs spreading along the CMB slightly decreases the stability of dense reservoirs, i.e., the amount of dense material entrained upward is slightly larger than in the regular pPv case (i.e., viscosity of pPv identical to that of perovskite). Furthermore, the topography and steepness of these reservoirs slightly increase. However, as in the regular pPv case, the dense reservoirs are maintained over periods of time comparable to the age of the Earth. Key Points With weak pPv, cold slabs spread more easily and broadly along the CMBThis increases the CMB heat flux and the steepness of the primordial reservoirsThe stability of primordial reservoirs is not substantially altered by weak pPv
ISSN:0094-8276
1944-8007
DOI:10.1002/2014GL061362