Graphite with growth spirals in Mg-Al-rich granulite from the area to the south of Syowa Station, Antarctica

Abstract

Graphite crystals with growth spirals were first found in an upper granulite-facies sapphirine-spinel-corundum-anorthite-bearing Mg-Al-rich rock from the area to the south of Syowa Station, Antarctica. This finding would be an important clue to the long debated problems about fluids during granulite-facies metamorphism: their absence or presence, behavior, composition, origin and so on. The Mg-Al-rich granulite occurs as a small block enclosed within a dolomitic marble layer. The carbon and oxygen stable isotopic compositions of graphite and coexisting carbonate minerals indicate that they are in equilibrium, and that the fluid from which graphite precipitated was local in origin. The graphite crystals with growth spirals are in direct contact with Mg-cordierite, anorthite, and talc, and probably grew before these minerals as suggested by their textural relations. They probably precipitated from fluid released from partial melts upon cooling after the peak of granulite-facies metamorphism.