[S-MP32] Deformed rocks, Metamorphic rocks and Tectonics

[SMP32-08] FeAlO₃ phase at ultrahigh-temperature metamorphic conditions: Evidences from the sillimanite—Fe₂O₃ and sillimanite—Fe₃O₄ systems at 9 kbar and 1050 ℃

*Toshisuke Kawasaki¹, Tatsuro Adachi², Hiroaki Ohfuji¹, Yasuhito Osanai² (1.Ehime University, 2.Kyushu University)

Keywords:FeAlO3 phase, sillimanite, corundum, spinel, ultrahigh-temperature granulies

Two high pressure experiments at 9 kbar and 1050 ℃ under moisture condition reveal FeAlO₃ phase is stable under ultrahigh-temperature metamorphic conditions. FeAlO₃ and corundum newly crystallised accompanying SiO₂-rich melt and vapour among sillimanite crystals from the mixture of Rundvågshetta sillimanite and reagent-grade Fe₂O₃ (weight ratio of 95:5) within Pt capsule. We found no hematite in the charge. In contrast, we found FeAlO₃ phase, SiO₂-rich melt and vapour among sillimanite from the mixture of Rundvågshetta sillimanite and reagent-grade Fe₃O₄ at (weight ratio of 86:14) within AuPd capsule. We found a domain composed by FeAlO₃, corundum, magnetite—hercynite spinel and ulvöspinel at the bottom part of the charge. The domain was contact with melt among sillimanite. The present results suggest the possibility that FeAlO₃ phase would be an index mineral of ultrahigh-temperature metamorphism for the partially melted Fe—Al-rich granulites under hydrous and oxidised environments.