High‐pressure and high‐temperature reactions between silicates and liquid iron alloys, in the diamond anvil cell, studied by analytical electron microscopy

Abstract

We report new experimental results on mixtures of iron alloys and silicates (Fe + forsterite, Fe + (Mg 0.89 ,Fe 0.11 )SiO 3 enstatite, Fe + (Mg 0.89 ,Fe 0.11 ) 2 SiO 4 olivine, Fe + FeS + (Mg 0.83 ,Fe 0.17 ) 2 SiO 4 olivine, and FeS + (Mg 0.83 ,Fe 0.17 ) 2 SiO 4 olivine) reacted at about 70 GPa and 130 GPa, at high temperature in a laser‐heated diamond anvil cell. The recovered samples were studied by analytical transmission electron microscopy. We found that chemical reactions occurred between molten iron alloys and solid oxides, leading to a dissolution of oxygen in the molten metallic phase, and a drastic depletion of iron in the oxides in contact with the metallic phase. Chromium and manganese partition into the liquid iron. Oxygen is therefore a serious candidate for being a light element in the Earth's core, and oxides which have experienced a high‐pressure contact with molten iron should have a rather low Fe/Fe+Mg ratio.