Hydrogen Partitioning into Molten Iron at High Pressure: Implications for Earth's Core
Takuo Okuchi
Because of dissolution of lighter elements such as sulfur, carbon,
hydrogen, and oxygen, Earth's outer core is about 10 percent less
dense than molten iron at the relevant pressure and temperature conditions. To determine whether hydrogen can account for a major part
of the density deficit and is therefore an important constituent in the
molten iron outer core, the hydrogen concentration in molten iron was
measured at 7.5 gigapascals. From these measurements, the
metal-silicate melt partitioning coefficient of hydrogen was determined
as a function of temperature. If the magma ocean of primordial Earth
was hydrous, more than 95 mole percent of H2O in this ocean
should have reacted with iron to form FeHx, and about 60 percent of the density deficit is reconciled by adding hydrogen to the
core.
Department of Earth and Planetary Sciences, Tokyo Institute of
Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152, Japan.
