Research ArticleGEOLOGY

A nearly water-saturated mantle transition zone inferred from mineral viscosity

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Science Advances  07 Jun 2017:
Vol. 3, no. 6, e1603024
DOI: 10.1126/sciadv.1603024
  • Fig. 1 TEM images of ringwoodite and bridgmanite before and after annealing.

    (A) Inverted bright-field image of ringwoodite before annealing (ρi = 11.0/μm2). (B) Inverted bright-field image of ringwoodite after annealing for 12 hours at 2000 K (ρf = 0.87/μm2). (C) Dark-field image of bridgmanite before annealing (ρi = 8.43/μm2). (D) Dark-field image of bridgmanite after annealing for 24 hours at 1600 K (ρf = 4.32/μm2). Rw., ringwoodite; Brg., bridgmanite.

  • Fig. 2 Results of dislocation recovery experiments on ringwoodite and bridgmanite.

    (A) Dislocation mobility in ringwoodite as a function of water content at different temperatures. (B) Dislocation mobility in bridgmanite as a function of temperature. (C) Comparison of dislocation mobilities in ringwoodite and bridgmanite at different temperatures for different water contents.

  • Fig. 3 Reciprocal dislocation mobility (1/k) for major minerals in the upper mantle, MTZ, and lower mantle shown in relation to relative viscosity (thick pink line).

    The relative viscosity (η) is estimated from postglacial rebound data and gravity data (1214). The dislocation mobility data for ringwoodite and bridgmanite are from this study, and that for olivine is from Wang (31); the dislocation mobility in wadsleyite is assumed to be the same as that for ringwoodite. The activation volume for all minerals is assumed to be 2.6 cm3/mol (31).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/6/e1603024/DC1

    fig. S1. Cross section through the multianvil cell assemblies used for high-pressure experiments.

    fig. S2. FT-IR spectra for ringwoodite and bridgmanite before and after dislocation recovery annealing experiments.

    fig. S3. Ringwoodite and bridgmanite synthesized from olivine and orthopyroxene and deformed in the same high P-T run at 23.3 GPa, 2000 K.

    table S1. Experimental conditions, initial and final dislocation densities, and dislocation annihilation rates for ringwoodite.

    table S2. Experimental conditions, initial and final dislocation densities, and dislocation annihilation rates for bridgmanite.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Cross section through the multianvil cell assemblies used for high pressure experiments.
    • fig. S2. FT-IR spectra for ringwoodite and bridgmanite before and after dislocation recovery annealing experiments.
    • fig. S3. Ringwoodite and bridgmanite synthesized from olivine and orthopyroxene and deformed in the same high P-T run at 23.3 GPa, 2000 K.
    • table S1. Experimental conditions, initial and final dislocation densities, and dislocation annihilation rates for ringwoodite.
    • table S2. Experimental conditions, initial and final dislocation densities, and dislocation annihilation rates for bridgmanite.

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