Composition of the upper mantle: Geophysical tests of two petrological models

Jay D. Bass, Don L. Anderson

Research output: Contribution to journalArticle

Abstract

The elastic properties of candidate mantle phases are used to test the viability of olivine‐rich (pyrolitic) and CaO + Al2O3‐rich (eclogitic) assemblages for the mantle. High temperature adiabats for each phase of interest are constructed and compared to mantle seismic properties. Both pyrolitic and eclogitic assemblages satisfy the seismic properties between ∼ 200 and 400 km. Between 400 and 670 km depth an eclogitic assemblage yields a superior match to velocities and velocity gradients. The 400 km seismic discontinuity may represent a chemical boundary between pyrolite and picritic eclogite (“piclogite”) or phase transformations in the olivine + orthopyroxene components of a piclogitic assemblage containing about 16% olivine. High velocity gradients in the transition zone may be explained by the transformation of Ca‐rich cpx to majorite garnet. Seismic properties at the top of the lower mantle are consistent with pyrolite, piclogite or perovskite, implying that the 670 km discontinuity may be a chemical boundary.

Original languageEnglish (US)
Pages (from-to)229-232
Number of pages4
JournalGeophysical Research Letters
Volume11
Issue number3
DOIs
StatePublished - Mar 1984
Externally publishedYes

Fingerprint

seismic property
pyrolite
upper mantle
Earth mantle
eclogite
mantle
olivine
discontinuity
majorite
elastic property
perovskite
lower mantle
orthopyroxene
transition zone
gradients
garnet
viability
garnets
phase transformations
elastic properties

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

Composition of the upper mantle : Geophysical tests of two petrological models. / Bass, Jay D.; Anderson, Don L.

In: Geophysical Research Letters, Vol. 11, No. 3, 03.1984, p. 229-232.

Research output: Contribution to journalArticle

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