Effects of pressure and temperature on the silicon diffusivity of pyrope-rich garnet

Akira Shimojuku, Tomoaki Kubo, Takumi Kato, Takashi Yoshino, Masayuki Nishi, Tomoki Nakamura, Ryuji Okazaki, Yuki Kakazu

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

We have determined the pressure and temperature dependencies of Si volume diffusion rates in a single crystal of Pyp75Alm15Gr10 garnet at 6-25GPa and 1400-1800°C by the 29Si tracer diffusion method. High-pressure experiments were conducted using the Kawai-type multi-anvil high-pressure apparatus. Diffusion profiles were obtained using secondary ion mass spectrometry in the depth-profiling mode. The Si diffusion coefficient in garnet (Dgt) is expressed by the Arrhenius equation: Dgt=D0 exp(-(E*+PV*)/RT), with log10D0=-7.1±1.7m2/s, E*=345±56kJ/mol, and V*=4.7±0.5cm3/mol. Si diffusion seems to be the slowest in the major constituent elements in a pyrope-rich garnet and control rates of plastic deformation. The comparison between Si diffusion rates in garnet and wadsleyite/ringwoodite suggests that garnet has similar or slightly lower strength (at most ~2times) compared with wadsleyite, and has similar or slightly higher strength (at most ~3times) compared with ringwoodite at temperatures ranging from 900 to 1300°C. Thus, strength contrast between subducted oceanic crust and underlying peridotite layer may be small at the mantle transition zone conditions. This result suggests that the separation of subducted oceanic crust from an underlying peridotite layer may not occur.

Original languageEnglish
Pages (from-to)28-38
Number of pages11
JournalPhysics of the Earth and Planetary Interiors
Volume226
DOIs
Publication statusPublished - Jan 2014

Fingerprint

pyrope
garnets
diffusivity
silicon
garnet
wadsleyite
ringwoodite
peridotite
temperature
crusts
oceanic crust
anvils
high strength
secondary ion mass spectrometry
plastic deformation
tracers
Earth mantle
transition zone
diffusion coefficient
effect

Keywords

  • Diffusion
  • Garnet
  • Mantle
  • Rheology
  • Subducted oceanic crust

ASJC Scopus subject areas

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

Cite this

Effects of pressure and temperature on the silicon diffusivity of pyrope-rich garnet. / Shimojuku, Akira; Kubo, Tomoaki; Kato, Takumi; Yoshino, Takashi; Nishi, Masayuki; Nakamura, Tomoki; Okazaki, Ryuji; Kakazu, Yuki.

In: Physics of the Earth and Planetary Interiors, Vol. 226, 01.2014, p. 28-38.

Research output: Contribution to journalArticle

Shimojuku, Akira ; Kubo, Tomoaki ; Kato, Takumi ; Yoshino, Takashi ; Nishi, Masayuki ; Nakamura, Tomoki ; Okazaki, Ryuji ; Kakazu, Yuki. / Effects of pressure and temperature on the silicon diffusivity of pyrope-rich garnet. In: Physics of the Earth and Planetary Interiors. 2014 ; Vol. 226. pp. 28-38.
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N2 - We have determined the pressure and temperature dependencies of Si volume diffusion rates in a single crystal of Pyp75Alm15Gr10 garnet at 6-25GPa and 1400-1800°C by the 29Si tracer diffusion method. High-pressure experiments were conducted using the Kawai-type multi-anvil high-pressure apparatus. Diffusion profiles were obtained using secondary ion mass spectrometry in the depth-profiling mode. The Si diffusion coefficient in garnet (Dgt) is expressed by the Arrhenius equation: Dgt=D0 exp(-(E*+PV*)/RT), with log10D0=-7.1±1.7m2/s, E*=345±56kJ/mol, and V*=4.7±0.5cm3/mol. Si diffusion seems to be the slowest in the major constituent elements in a pyrope-rich garnet and control rates of plastic deformation. The comparison between Si diffusion rates in garnet and wadsleyite/ringwoodite suggests that garnet has similar or slightly lower strength (at most ~2times) compared with wadsleyite, and has similar or slightly higher strength (at most ~3times) compared with ringwoodite at temperatures ranging from 900 to 1300°C. Thus, strength contrast between subducted oceanic crust and underlying peridotite layer may be small at the mantle transition zone conditions. This result suggests that the separation of subducted oceanic crust from an underlying peridotite layer may not occur.

AB - We have determined the pressure and temperature dependencies of Si volume diffusion rates in a single crystal of Pyp75Alm15Gr10 garnet at 6-25GPa and 1400-1800°C by the 29Si tracer diffusion method. High-pressure experiments were conducted using the Kawai-type multi-anvil high-pressure apparatus. Diffusion profiles were obtained using secondary ion mass spectrometry in the depth-profiling mode. The Si diffusion coefficient in garnet (Dgt) is expressed by the Arrhenius equation: Dgt=D0 exp(-(E*+PV*)/RT), with log10D0=-7.1±1.7m2/s, E*=345±56kJ/mol, and V*=4.7±0.5cm3/mol. Si diffusion seems to be the slowest in the major constituent elements in a pyrope-rich garnet and control rates of plastic deformation. The comparison between Si diffusion rates in garnet and wadsleyite/ringwoodite suggests that garnet has similar or slightly lower strength (at most ~2times) compared with wadsleyite, and has similar or slightly higher strength (at most ~3times) compared with ringwoodite at temperatures ranging from 900 to 1300°C. Thus, strength contrast between subducted oceanic crust and underlying peridotite layer may be small at the mantle transition zone conditions. This result suggests that the separation of subducted oceanic crust from an underlying peridotite layer may not occur.

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