Reaction of metallic iron and minerals under high pressure and its implications for the composition of the Earth's core

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Using 6-8 type high-pressure apparatus, the high pressure experiments on the reaction of silicate minerals and metallic iron was performed at 10-15 GPa, and the solubility of light elements, such as oxygen and silicon, in metallic iron was investigated. At above 2000ﾟC,silicates and metallic iron were in liquid state. The specimen was quenched and recovered to normal pressure-temperature condition, and their texture and chemical compositions were examined.Dendritic textures and spherical grains were found in the metallic grain of recovered specimen at 15GPa. The dendritic textures show that these FeO grains were exsolved from molten metallic iron, and spherical FeO grains are regarded as the crystallized immissible oxygen rich liquid. The amount of dissolved oxygen in the metallic liquid iron was estimated to be about 10wt%. However, the amount of dissolved silicon in the molten iron is very small. Itwas also found that the amount of dissolved oxygen in the metallic phase is largely depend on the composition of the coexisting silicate liquid. The solved oxygen in the metallic phase decreased with the decrease of FeO content of the coexisting silicate liquid. At 10GPa, the amount of dissolved oxygen in the metallic phase was very small, and only hydrogen was dissolved in the molten iron.Unforunately, we have no mateal that do not react with metallic iron and silicates. Hence the specimens of the present experiments were reacted with the sample chamber and/or heating element. In order to reveal the nature of reaction between metallic iron and silicates under high pressures, further developments are required for the sample capsule and sample heating technique.