[S-IT21] Planetary cores: Structure, formation, and evolution

[SIT21-07] In-situ observations of iron-silicate-water-sulfur system and behaviors of light elements during the Earth’s core-mantle formation

*Riko Iizuka-Oku^1,2, Hirotada Gotou³, Hiroyuki Kagi¹ (1.Geochemical Research Center, Graduate School of Science, The University of Tokyo, 2.Department of Earth and Planetary Sciences, Harvard University, USA, 3.ISSP, The University of Tokyo)

Keywords:Hydrogen, Water, Sulfur, Core, High pressure

The Earth’s core mainly consists of iron and is thought to contain light elements. Hydrogen is one of the candidates that account for the density deficit and significant decrease in the melting temperature of iron. It has become important to study the interaction of multiple light elements with iron and hydrous silicates during the early Earth’s evolution. This study investigated the iron–hydrous silicate containing sulfur system using in-situ X-ray diffraction and imaging observations at 5–10 GPa, up to ~1900 °C to clarify the reactions and the effect of light elements on the iron–silicate segregation process in the primitive Earth. Sequential reactions (phase transformation and hydrogenation of iron, and formation of iron sulfide and silicates) were observed from X-ray diffraction. The newly constructed X-ray imaging system achieved a spatial resolution of ~10 microns to more clearly capture the formation and motion of molten iron droplets with several microns in diameter. Sulfur distorted the shape of iron spheres and affected the growth of those size by reducing the interfacial energy between molten iron and silicates. The light elements in the molten iron and the remaining silicate grains affect the iron–silicate segregation process as the temperature increases.