TY - JOUR
T1 - Grain growth kinetics of ringwoodite and its implication for rheology of the subducting slab
AU - Yamazaki, Daisuke
AU - Inoue, Toru
AU - Okamoto, Mana
AU - Irifune, Tetsuo
N1 - Funding Information:
The authors thank T. Shinmei for helpful comments, M. Murayama and H. Asahi for allowing and helping the authors to use FE-SEM at Kochi University, and C. Bina for reading the manuscript of the revised version. The authors are also grateful to S. Karato, J. Van Orman and an anonymous referee for valuable comments. This work was partially supported by a Grant-in-Aid for Scientific Research to D. Y. (no. 15740276) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
PY - 2005/8/15
Y1 - 2005/8/15
N2 - Grain growth rates of Mg2SiO4- and (Mg0.9Fe0.1)2SiO4 -ringwoodites have been studied under the conditions of the mantle transition zone at a pressure of 21 GPa and temperatures ranging from 1473 to 2023 K, using a Kawai-type high-pressure apparatus. The grain growth rates were expressed by Gn - G0n =k0texp (-H*/RT) where G (m) is grain size at time t (s), and G0 is the initial grain size at t=0, with n=4.5 ± 0.8, and H* = 414 kJ/mol and log k0 = -20.4 ± 1.6 m4.5/s for (Mg0.9Fe0.1) 2SiO4-ringwoodite, and H* = 456 kJ/mol and log k0 = -20.2 ± 1.4 m4.5/s for Mg2SiO4-ringwoodite. Using these kinetic parameters for grain growth, we estimated the grain size of ringwoodite in the cold subducting slabs to be less than ∼100 μm. This suggests that the dominant deformation mechanism in the subducting slab is diffusion creep. It is also likely that some cold slabs are softer than the warmer surrounding mantle.
AB - Grain growth rates of Mg2SiO4- and (Mg0.9Fe0.1)2SiO4 -ringwoodites have been studied under the conditions of the mantle transition zone at a pressure of 21 GPa and temperatures ranging from 1473 to 2023 K, using a Kawai-type high-pressure apparatus. The grain growth rates were expressed by Gn - G0n =k0texp (-H*/RT) where G (m) is grain size at time t (s), and G0 is the initial grain size at t=0, with n=4.5 ± 0.8, and H* = 414 kJ/mol and log k0 = -20.4 ± 1.6 m4.5/s for (Mg0.9Fe0.1) 2SiO4-ringwoodite, and H* = 456 kJ/mol and log k0 = -20.2 ± 1.4 m4.5/s for Mg2SiO4-ringwoodite. Using these kinetic parameters for grain growth, we estimated the grain size of ringwoodite in the cold subducting slabs to be less than ∼100 μm. This suggests that the dominant deformation mechanism in the subducting slab is diffusion creep. It is also likely that some cold slabs are softer than the warmer surrounding mantle.
KW - Grain growth
KW - Grain size
KW - Mantle transition zone
KW - Rheology
KW - Ringwoodite
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U2 - 10.1016/j.epsl.2005.06.005
DO - 10.1016/j.epsl.2005.06.005
M3 - Article
AN - SCOPUS:24344439380
SN - 0012-821X
VL - 236
SP - 871
EP - 881
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
IS - 3-4
ER -