Effect of metallic melt on the viscosity of peridotite

Justin Hustoft, Ted Scott, David L. Kohlstedt

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11 Scopus citations

Abstract

To examine the dependence of viscosity of a partially molten peridotite on the wetting nature of the melt phase, we combine previously published measurements of diffusion creep on samples of olivine + MORB with new results from our creep experiments on samples of olivine + Fe-S and samples of olivine + Au. For these three partially molten systems, the melt-solid dihedral angle varies from θ = 38° for olivine + MORB to θ = 90° for olivine + Fe-S to θ = 150° for olivine + Au. In each case, the viscosity, η, decreases with increasing melt fraction, φ{symbol}, according to the relation η ∝ exp(- αφ{symbol}). Our results reveal a substantial change in the value of the material-dependent parameter α, from α = 21 for MORB in an olivine aggregate (with θ < 60°) to α = 4 ± 1 for the two metallic melts in polycrystalline olivine (both with θ > 60°). For a melt fraction of 0.05, this difference in α corresponds to more than a factor of two higher viscosity for samples composed of olivine + a metallic melt relative to the viscosity of samples of olivine + MORB. This difference in viscosity can be attributed to two factors: (i) The enhancement of grain-scale stress due to the presence of melt is smaller for the metallic melt than for the basaltic melt because the melt-solid contact area decreases with increasing θ, and (ii) the flux of olivine through the metallic melt is small due to the low solubility of olivine in the non-silicate melts.

Original languageEnglish (US)
Pages (from-to)355-360
Number of pages6
JournalEarth and Planetary Science Letters
Volume260
Issue number1-2
DOIs
StatePublished - Aug 15 2007

Bibliographical note

Funding Information:
We thank Mark Zimmerman for assistance with experiments and discussions. This study was supported by NSF grant OCE-0327143 (basalt melt) and NASA PG&G grant NNG04G173G (metallic melts).

Keywords

  • creep
  • metallic melt
  • olivine
  • viscosity

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