Abstract
Knowledge of grain growth rate of ε-iron can put constraint on estimation of the grain size in the inner core. We determined grain growth rate of ε-iron at ∼55 GPa and 1200–1500 K by means of in-situ X-ray diffraction observation to be Gn−G0n=kt, where G (m) is the grain size at time t (s), G0 (m) is the initial grain size, n is growth exponent (fixed to 2) and k is the growth constant expressed as k=k0exp(−H⁎/RT) with log k0(mn/s)=−5.8(±2.4) and activation enthalpy H⁎=221(±61) kJ/mol, and R is the gas constant and T is the absolute temperature. Extrapolation of the grain growth law of ε-iron to the inner core conditions suggests that the grain size in the inner core is in a range from several hundred meters to several kilometers, which is intermediate among the previous estimations, and hence the dominant deformation mechanism is considered to be Harper–Dorn creep rather than diffusion creep as pointed out by the previous work. This indicates the relatively uniform viscosity in the entire inner core.
| Original language | English |
|---|---|
| Pages (from-to) | 238-243 |
| Number of pages | 6 |
| Journal | Earth and Planetary Science Letters |
| Volume | 459 |
| DOIs | |
| Publication status | Published - Feb 1 2017 |
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Keywords
- grain growth
- inner core
- ε-iron
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science
Cite this
Grain growth of ε-iron : Implications to grain size and its evolution in the Earth's inner core. / Yamazaki, Daisuke; Tsujino, Noriyoshi; Yoneda, Akira; Ito, Eiji; Yoshino, Takashi; Tange, Yoshinori; Higo, Yuji.
In: Earth and Planetary Science Letters, Vol. 459, 01.02.2017, p. 238-243.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Grain growth of ε-iron
T2 - Implications to grain size and its evolution in the Earth's inner core
AU - Yamazaki, Daisuke
AU - Tsujino, Noriyoshi
AU - Yoneda, Akira
AU - Ito, Eiji
AU - Yoshino, Takashi
AU - Tange, Yoshinori
AU - Higo, Yuji
PY - 2017/2/1
Y1 - 2017/2/1
N2 - Knowledge of grain growth rate of ε-iron can put constraint on estimation of the grain size in the inner core. We determined grain growth rate of ε-iron at ∼55 GPa and 1200–1500 K by means of in-situ X-ray diffraction observation to be Gn−G0n=kt, where G (m) is the grain size at time t (s), G0 (m) is the initial grain size, n is growth exponent (fixed to 2) and k is the growth constant expressed as k=k0exp(−H⁎/RT) with log k0(mn/s)=−5.8(±2.4) and activation enthalpy H⁎=221(±61) kJ/mol, and R is the gas constant and T is the absolute temperature. Extrapolation of the grain growth law of ε-iron to the inner core conditions suggests that the grain size in the inner core is in a range from several hundred meters to several kilometers, which is intermediate among the previous estimations, and hence the dominant deformation mechanism is considered to be Harper–Dorn creep rather than diffusion creep as pointed out by the previous work. This indicates the relatively uniform viscosity in the entire inner core.
AB - Knowledge of grain growth rate of ε-iron can put constraint on estimation of the grain size in the inner core. We determined grain growth rate of ε-iron at ∼55 GPa and 1200–1500 K by means of in-situ X-ray diffraction observation to be Gn−G0n=kt, where G (m) is the grain size at time t (s), G0 (m) is the initial grain size, n is growth exponent (fixed to 2) and k is the growth constant expressed as k=k0exp(−H⁎/RT) with log k0(mn/s)=−5.8(±2.4) and activation enthalpy H⁎=221(±61) kJ/mol, and R is the gas constant and T is the absolute temperature. Extrapolation of the grain growth law of ε-iron to the inner core conditions suggests that the grain size in the inner core is in a range from several hundred meters to several kilometers, which is intermediate among the previous estimations, and hence the dominant deformation mechanism is considered to be Harper–Dorn creep rather than diffusion creep as pointed out by the previous work. This indicates the relatively uniform viscosity in the entire inner core.
KW - grain growth
KW - inner core
KW - ε-iron
UR - http://www.scopus.com/inward/record.url?scp=85006298142&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85006298142&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2016.11.049
DO - 10.1016/j.epsl.2016.11.049
M3 - Article
AN - SCOPUS:85006298142
VL - 459
SP - 238
EP - 243
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
ER -