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Effect of pressure on grain‐growth kinetics of ferropericlase to lower mantle conditions
Author(s) -
Tsujino Noriyoshi,
Nishihara Yu
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl043491
Subject(s) - grain size , kinetics , annealing (glass) , materials science , grain growth , thermodynamics , anisotropy , phase (matter) , mantle (geology) , analytical chemistry (journal) , mineralogy , geology , metallurgy , chemistry , physics , optics , paleontology , chromatography , quantum mechanics , organic chemistry
Grain‐growth kinetics of (Mg 0.85 Fe 0.15 )O ferropericlase was investigated at a temperature of 1873 K up to a pressure of 25 GPa under dry conditions using a Kawai‐type multi‐anvil apparatus. The grain‐growth kinetics of ferropericlase is described by G n − G 0 n = k 0 exp(−) t where G is the average grain‐size at annealing time t ; G 0 , the initial average grain‐size; P , pressure; R , the gas constant; and T , absolute temperature. Least squares fit of this equation for the present data and our previous data on the same material yielded n = 2.8 ± 0.2, k 0 = 10 −8.4±1.1 m 2.8 /s, E * = 273 ± 24 kJ/mol, and V * = 4.5 ± 0.2 cm 3 /mol. The present results show that at the conditions at the top of the lower mantle (700 km depth), the grain‐size of ferropericlase in a single phase system evolves to ∼1 cm after significant geological time of 1 My. The present results may be applied to regions where single phase ferropericlase aggregates are present, say by deformation‐induced phase segregation. In these areas, the grain‐growth kinetics is fast so that one expects a large grain‐size that will results in strong lattice‐preferred orientation causing significant seismic anisotropy.