Distinguishing eclogite from peridotite: EBSD-based calculations of seismic velocities

James R. Worthington, Bradley R. Hacker, George Zandt

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Seismic velocities were calculated for 11 eclogites from the Western Gneiss Region, Norway, based on electron-backscatter diffraction (EBSD). The P-wave velocities are 8.0-8.5 kms-1 and the S-wave velocities are 4.5-4.8 kms-1; VP/VS1 (the ratio of P-wave to fast S-wave velocities) is 1.74-1.81. All the eclogites are relatively isotropic, with the higher anisotropies (3- 4 per cent) in micaceous samples. Peridotite is comparatively more anisotropic (4-14 per cent more for P waves and up to 10 per cent more for S waves), and can have anomalously low VP/VS1, which may be useful means of distinguishing it from eclogite. Micaceous eclogite may be modelled using hexagonal anisotropy with a slow unique axis, whereas peridotite is most robustly modelled using orthorhombic anisotropy.

Original languageEnglish (US)
Pages (from-to)489-505
Number of pages17
JournalGeophysical Journal International
Volume193
Issue number1
DOIs
StatePublished - May 3 2013

Keywords

  • Acoustic properties
  • Body waves
  • Composition of the mantle
  • Dynamics of lithosphere and mantle
  • Seismic anisotropy
  • Surface waves and free oscillations

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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