The difficulty for subducted oceanic crust to accumulate at the Earth's core-mantle boundary

Mingming Li, Allen K. McNamara

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Seismic tomography has revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath the central Pacific and Africa. The LLSVPs are further shown to be compositionally different from their surroundings. Among several hypotheses put forth in recent years to explain the cause of the LLSVPs, one postulates that they are thermochemical piles caused by accumulation of subducted oceanic crust at the core-mantle boundary (CMB). Mineral physics experiments indicate that oceanic crust becomes denser than the surrounding mantle at lower mantle pressures. In addition, seismic observations provide evidence of subducted slabs arriving at the CMB. However, a major question pertains to whether subducted oceanic crust can survive viscous stirring associated with mantle plumes and accumulate into piles with the same spatial scale as LLSVPs. We perform a set of high-resolution convection calculations to examine this hypothesis by investigating the interaction of thin oceanic crust (6 km) with mantle plumes. Our results show that as subducted oceanic crust is swept toward upwelling plume regions, the majority of it is viscously stirred into the surrounding mantle. Only a small amount of oceanic crust may accumulate at the base of plumes, but it is consistently entrained away into the plume at a rate equal to or greater than it is accumulated. We find that it is difficult for subducted oceanic crust to accumulate into large thermochemical piles at the CMB. Key Points High resolution 2D calculations are performed.The major part of subducted oceanic crust is entrained up by upwelling plumes.It is difficult for the subducted oceanic crust to accumulate at the CMB.

Original languageEnglish (US)
Pages (from-to)1807-1816
Number of pages10
JournalJournal of Geophysical Research: Solid Earth
Volume118
Issue number4
DOIs
StatePublished - 2013

Fingerprint

Earth core
core-mantle boundary
oceanic crust
crusts
Earth (planet)
Piles
plumes
Earth mantle
piles
plume
shear
pile
upwelling water
mantle plume
mantle
Tomography
Minerals
Physics
upwelling
seismic tomography

Keywords

  • LLSVPs
  • mantle convection
  • subducted oceanic crust
  • thermochemical piles

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

The difficulty for subducted oceanic crust to accumulate at the Earth's core-mantle boundary. / Li, Mingming; McNamara, Allen K.

In: Journal of Geophysical Research: Solid Earth, Vol. 118, No. 4, 2013, p. 1807-1816.

Research output: Contribution to journalArticle

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