Research ArticleGEOLOGY

Experimental evidence supports mantle partial melting in the asthenosphere

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Science Advances  20 May 2016:
Vol. 2, no. 5, e1600246
DOI: 10.1126/sciadv.1600246
  • Fig. 1 Scanning electron microscope backscattered electron images showing melt distribution in samples.

    (A) Pure SC olivine. (B) 0.1% MORB. (C) 0.5% MORB. (D) 1% MORB. (E) 2% MORB. (F) 4% MORB. Black lines on the images are cracks developed during quenching and decompression. Note that the thickness of melt films at the grain boundaries increases with increasing melt fraction (ϕ) from 0.5 to 4.0% (C to F).

  • Fig. 2 P-wave (50 MHz) and S-wave (30 MHz) velocities as a function of increasing temperature, from 1273 to 1623 K (left part of the graph), and as a function of time at a constant temperature of 1623 K (right side of the graph), for the six compositions investigated in this study.
  • Fig. 3 Dependence of seismic properties on melt fraction.

    (A and B) Dependence of (A) VP and VS and (B) 100/Q on melt fraction. Open symbols are the experimental data and curves are the associated fits. In addition to our experimental results and their fits (thick curves), modeled velocities (thin curves) that include the anelastic effects expected for the seismic waves at high temperatures are reported in (A), using α values (from 0.2 to 0.4 shown in the graph) covering the entire range that was previously observed (30). In (B), the solid green triangles represent additional data from torsional experiments (17).

  • Fig. 4 P-wave (50 MHz) and S-wave (30 MHz) echoes recorded at 2.4 to 2.5 GPa for the six studied compositions.

    Black and red curves are signals at temperatures of 1573 and 1623 K, respectively. For SC olivine and 0.1% MORB, black and red curves completely overlap. Both P- and S-wave echoes (~100-ns time interval) were normalized with respect to the maximum amplitude of the echo from the buffer rod (BR) under the same pressure-temperature conditions.

  • Fig. 5 Empirical profiles, calculated for various melt fractions, compared to seismic profiles.

    (A) VP/VS ratio as a function of melt compared to global earth models (3941, 68) and regional seismic profiles (42, 43), for an anelasticity attenuation factor α = 0.26. (B) Reported seismic profiles of attenuation compared with empirical profiles calculated for melt fractions ranging from 0 to 0.5%, based on our experimental results and for an anelasticity attenuation factor α = 0.26. Global seismic models (3537, 3941) and regional seismic profiles (69, 70). The nonlinear evolution of 100/QS as a function of ϕ is due to the logarithmic fitting used (Fig. 3B).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/5/e1600246/DC1

    fig. S1. Schematic drawing of the cell assembly used in the multianvil experiments.

    fig. S2. Reduction of S- and P-wave velocities as a function of melt fraction.

    fig. S3. Seismic profiles of VP, VS, and 100/QS compared with empirical profiles, calculated for various melt fractions, based on the experimental results from this study and for an anelasticity attenuation factor α = 0.26 (30).

    fig. S4. Ultrasonic signal recorded at 30 MHz.

    table S1. Experimental conditions and the results.

    Reference (71)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Schematic drawing of the cell assembly used in the multianvil experiments.
    • fig. S2. Reduction of S- and P-wave velocities as a function of melt fraction.
    • fig. S3. Seismic profiles of VP, VS, and 100/QS compared with empirical profiles,
      calculated for various melt fractions, based on the experimental results from this
      study and for an anelasticity attenuation factor α = 0.26 (30).
    • fig. S4. Ultrasonic signal recorded at 30 MHz.
    • table S1. Experimental conditions and the results.
    • Reference (71)

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