The influences of composition-sand temperature-dependent rheology in thermal-chemical convection on entrainment of the D"-layer

B. Schott, D. A. Yuen, A. Braun

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The entrainment dynamics in the D″-layer are influenced by multitudinous factors, such as thermal and compositional buoyancy, and temperature- and composition-dependent viscosity. Here, we are focusing on the effect of compositionally dependent viscosity on the mixing dynamics of the D″-layer, arising from the less viscous but denser D″-material. The marker method, with one million markers, is used for portraying the fine scale features of the compositional components, D″-layer and lower-mantle. The D″-layer has a higher density but a lower viscosity than the ambient lower-mantle, as suggested by melting point systematics. Results from a two-dimensional finite-difference numerical model including the extended Boussinesq approximation with dissipation number Di = 0.3, show that a D″-layer, less viscous than the ambient mantle by 1.5 orders of magnitude, cannot efficiently mix with the lower-mantle, even though the buoyancy parameter is as low as Rp = 0.6. However, very small-scale schlieren structures of D″-layer material are entrained into the lower-mantle. These small-scale lower-mantle heterogeneities have been imaged with one-dimensional wavelets in order to delineate quantitatively the multiscale features. They may offer an explanation for small-scale seismic heterogeneity inferred by seismic scattering in the lower-mantle.

Original languageEnglish (US)
Pages (from-to)43-65
Number of pages23
JournalPhysics of the Earth and Planetary Interiors
Volume129
Issue number1-2
DOIs
StatePublished - Jan 1 2002

Keywords

  • D"-layer
  • Entrainment
  • Seismic scattering
  • Thermochemical convection

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