Sulfidation Textures of FeNi Alloy in Unequilibrated Chondrites and Its Petrogenesis

A lot of troilite reaction rim textures formed through sulfidation of FeNi alloy of kamacite and taenite with sulfur rich gas have been identified especially in C03 unequilibrated carbonaceous chondrites. Troilite formation through sulfidation of FeNi alloy of kamacite and taenite with sulfur rich gas in the solar nebula is expected from the reaction kinetics as well as from the equilibrium condensation theory. On the other hand, heating experiments of mixtures including metallic iron grains and troilite powder show that troilite rim textures can be formed on chondrite parent body. Recent study shows that troilite reaction rim textures are more abundant for higher petrologic subtype (•¬ 3.2). This would mean that sulfidation of metallic iron would have also proceeded in CO3 parent body when petrologic subtype in C03s is due to thermal metamorphism in CO3 parent body.