Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity

Details Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003pepi..136...41s&link_type=abstract

Physics of the Earth and Planetary Interiors, Volume 136, Issue 1-2, p. 41-66.

Physics

32

Scientific paper

The single-crystal elastic moduli of spinel-structured γ-(Mg0.91Fe0.09)2SiO4 (ringwoodite) were measured to 16GPa at room temperature, and to 923K at ambient pressure by Brillouin spectroscopy. A third-order finite-strain equation of state yields pressure derivatives of 4.1 (2) and 1.3 (1) for the adiabatic bulk modulus (KS) and shear modulus (μ), respectively. The pressure derivatives of aggregate elastic moduli for all three polymorphs (α, β, and γ) of (Mg,Fe)2SiO4 in the Mg-rich end are equal within the mutual experimental uncertainties, with (∂KS/∂P)T=4.1-4.3 and (∂μ/∂P)T=1.3-1.4. A linear decrease of the elastic moduli and sound velocities with temperature adequately describes the data. The temperature derivatives of KS and μ are -0.021 and -0.016GPa/K, respectively. An extrapolation of our data to transition zone pressures and temperatures indicates that the shear and compressional impedance contrasts associated with β-(Mg,Fe)2SiO4-->γ-(Mg,Fe)2SiO4 transition are sufficient to produce a visible discontinuity at 520km depth even with only a moderate (30-50%) amount of olivine. Moreover, the partitioning of Fe between β-(Mg,Fe)2SiO4 and γ-(Mg,Fe)2SiO4 and majoritic garnet will produce a relatively sharp seismic discontinuity (in the order of 10-15km) even when the latent heat of reaction is taken into account. The visibility of the discontinuity in regional and global studies could be inhibited by large topography that would accompany any local variations in temperature or Fe content. The high VP contrasts observed in some localities are difficult to explain by the /β-->γ transition and are suggestive of a chemical boundary. This is consistent with chemical heterogeneity in the transition zone, probably related to subduction. One of the possible explanations for high velocity contrasts near 520km is a ``buried Moho''-a boundary between garnetite (former oceanic crust) and γ-(Mg,Fe)2SiO4-enriched (former peridotite) layers.

Affiliated with

Also associated with

No associations

Rating

Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Single-crystal elasticity of ringwoodite to high pressures and high temperatures: implications for 520 km seismic discontinuity will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1325472