Physics
Scientific paper
Aug 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004e%26psl.224..249t&link_type=abstract
Earth and Planetary Science Letters, Volume 224, Issue 3-4, p. 249-257.
Physics
14
Core Formation, Permeable Flow, Dihedral Angle, Lower Mantle, Early Earth
Scientific paper
We measured the dihedral angle of molten iron in (Mg,Fe)SiO3-perovskite aggregate with increasing pressure and temperature using laser-heated diamond anvil cell. Results demonstrate that it decreases from 94° at ~27 GPa and ~2400 K to 51° at ~47 GPa and ~3000 K. This value is smaller than the critical angle of 60°, thus allowing iron melt to wet the grain boundaries of silicate perovskite and develop an interconnected melt network within the perovskite-dominant matrix, even at very small melt fractions. The quenched liquid iron contained substantial amounts of oxygen and silicon as pressure and temperature increase. Such a decrease in the dihedral angle is likely due to a reduction in the iron-perovskite interfacial energy by dissolving oxygen and silicon into the liquid iron from coexisting silicate perovskite. These suggest that a wetting behaviour of core melts in the solid silicate mantle changes above ~40 GPa, corresponding to ~1000 km depth in the present Earth, and efficient metal segregation may have proceeded by permeable flow in a late stage of accretion. Oxygen and silicon incorporated during core formation and later by core-mantle boundary process may be important light elements in the Earth's core.
Bando Yoshio
Hirose Kei
Mitome Masanori
Ono Shigeaki
Takafuji Naoto
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