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

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

doi:10.1093/gji/ggt004

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

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

Research output: Contribution to journal › Article › peer-review

48 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; V_P/V_S1 (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 V_P/V_S1, 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 language	English (US)
Pages (from-to)	489-505
Number of pages	17
Journal	Geophysical Journal International
Volume	193
Issue number	1
DOIs	https://doi.org/10.1093/gji/ggt004
State	Published - Apr 1 2013
Externally published	Yes

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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10.1093/gji/ggt004

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title = "Distinguishing eclogite from peridotite: EBSD-based calculations of seismic velocities",

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.",

keywords = "Acoustic properties, Body waves, Composition of the mantle, Dynamics of lithosphere and mantle, Seismic anisotropy, Surface waves and free oscillations",

author = "Worthington, {James R.} and Hacker, {Bradley R.} and George Zandt",

year = "2013",

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doi = "10.1093/gji/ggt004",

language = "English (US)",

volume = "193",

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journal = "Geophysical Journal International",

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T2 - EBSD-based calculations of seismic velocities

AU - Worthington, James R.

AU - Hacker, Bradley R.

AU - Zandt, George

PY - 2013/4/1

Y1 - 2013/4/1

N2 - 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.

AB - 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.

KW - Acoustic properties

KW - Body waves

KW - Composition of the mantle

KW - Dynamics of lithosphere and mantle

KW - Seismic anisotropy

KW - Surface waves and free oscillations

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JO - Geophysical Journal International

JF - Geophysical Journal International

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

Abstract

Keywords

ASJC Scopus subject areas

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