Experimental and theoretical study of stability of dense hydrous magnesium silicates in the deep upper mantle

Tetsuya Komabayashi, Soichi Omori, Shigenori Maruyama

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Fluid-undersaturated experiments were conducted to determine the phase relations in the simplified peridotite system MgO-SiO2- H2O (MSH) at 11.0-14.5 GPa and 800-1400 °C. Stability relations of dense hydrous magnesium silicates (DHMSs) under fluid-undersaturated conditions were experimentally examined. From the fluid-absent experimental results, we retrieved thermodynamic data for clinohumite, phase A, phase E, and hydrous wadsleyite, consistent with the published data set for dry mantle minerals. With this new data set, we have calculated phase equilibria in the MSH system including dehydration reactions. The dehydration reactions calculated with lower water activities of 0.68-0.60 match the fluid-present experiments of this study above 11.0 GPa and 1000 °C, indicating that considerable amounts of silicate component were dissolved into the fluid phase. The calculated phase equilibria illustrate the stability of the post-antigorite phase A-bearing assemblages. In the cold subducting slab peridotite, phase A + enstatite assemblage survives into the transition zone, whereas phase A + forsterite + enstatite assemblage forms hydrous wadsleyite at a much shallower depth of about 360-km. The slab is subducted with no dehydration reactions occurring when entering the transition zone. The phase equilibria also show the high temperature stability of phase E. Phase E is stable up to 1200 °C at 13.5 GPa, a plausible condition in the mantle of relatively low temperature, i.e., beneath subduction zones. Phase E is a possible water reservoir in the mantle as well as wadsleyite and ringwoodite.

Original languageEnglish
Pages (from-to)191-209
Number of pages19
JournalPhysics of the Earth and Planetary Interiors
Volume153
Issue number4
DOIs
Publication statusPublished - Dec 15 2005
Externally publishedYes

Fingerprint

theoretical study
magnesium
upper mantle
silicates
wadsleyite
Earth mantle
experimental study
silicate
phase equilibrium
fluid
dehydration
fluids
enstatite
peridotite
mantle
transition zone
slab
slabs
clinohumite
ringwoodite

Keywords

  • High pressure
  • Hydrous phase
  • Subduction
  • Thermodynamic data
  • Water transportation

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science
  • Physics and Astronomy (miscellaneous)
  • Astronomy and Astrophysics

Cite this

Experimental and theoretical study of stability of dense hydrous magnesium silicates in the deep upper mantle. / Komabayashi, Tetsuya; Omori, Soichi; Maruyama, Shigenori.

In: Physics of the Earth and Planetary Interiors, Vol. 153, No. 4, 15.12.2005, p. 191-209.

Research output: Contribution to journalArticle

Komabayashi, Tetsuya ; Omori, Soichi ; Maruyama, Shigenori. / Experimental and theoretical study of stability of dense hydrous magnesium silicates in the deep upper mantle. In: Physics of the Earth and Planetary Interiors. 2005 ; Vol. 153, No. 4. pp. 191-209.
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