Discovery of post-perovskitephase transition and implications for the nature of the D" layer of the mantle

Kei Hirose, Katsuyuki Kawamura

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

MgSiO 3 is a principal mineral in the upper part of the lower mantle, but its stability and possible phase transition at greater depths have long been uncertain. Recently, a new high-pressure MgSiO 3 polymorph called "post-perovskite" was discovered above 125 GPa and 2500 K on the basis of X-ray diffraction measurements in a laser-heated diamond anvil cell (LH-DAC). Crystal structure of post-perovskite was first determined to be orthorhombic (space group: Cmcm) by molecular dynamics (MD) calculations. The first-principles theoretical calculations also confirmed the stability of this new phase. These results suggest that MgSiO 3 -rich post-perovskite is a predominant mineral below 2500-2700 km depth near the base of the mantle. The D" layer has long been the most enigmatic region in Earth's interior. The post-perovskite phase can account for the large seismic anomalies observed in the D" region, such as D" discontinuity, polarization anisotropy, and anticorrelation between S-wave and bulk sound velocities. The long-term enigma may be explained with this newly discovered crystal.

Original languageEnglish
Pages (from-to)37-46
Number of pages10
JournalSpecial Paper of the Geological Society of America
Volume421
DOIs
Publication statusPublished - Jan 1 2007

Keywords

  • Core-mantle boundary
  • D layer
  • Perovskite
  • Phase transition
  • Post-perovskite

ASJC Scopus subject areas

  • Geology

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