REACTIONS BETWEEN MOLTEN IRON AND SILICATE MELTS AT HIGH-PRESSURE - IMPLICATIONS FOR THE CHEMICAL EVOLUTION OF EARTHS CORE

Reactions between molten iron and silicate melt were investigated with mixtures of pure iron and silicates (1Fe + 3MgSiO(3) enstatite and 1Fe + 3(Mg0.9Fe0.1)(2)SiO4 olivine in volumetric ratio) as starting materials at pressures of 10-26 GPa and temperatures of about 2500 degrees C. The results show that a certain amount of Si (up to about 2%) dissolves in molten iron from silicate melt and that the dissolution is enhanced with increasing pressure. Many small spherical blobs composed of SiO2 and FeO present in coalesced iron grains were interpreted as quenched immiscible liquid formed during cooling. Therefore O also dissolves in molten iron under the experimental conditions. No evidence for dissolution of Mg was obtained. The present study also indicates that Si and O are important light elements of Earth's core if core segregation occurred in the deep magma ocean. The chemical evolution of Earth's core is discussed on the bases of the current core formation model and the present experimental results.