Garnet-glaucophane-quartz schist adjacent a serpentinite-matrix mélange on the Saganoseki Peninsula, Oita Prefecture [大分県佐賀関半島の蛇紋岩メランジュ近傍で発見された含ざくろ石藍閃石−石英片岩]

Blocks of garnet–glaucophane–quartz schist and gneissic garnet–actinolite schist were found as float adjacent to a serpentinite exposure on the Saganoseki Peninsula, Oita Prefecture. These metamorphic blocks are inferred to have been derived from a serpentinite-matrix mélange exposed in the area. Phengite K–Ar dating of the garnet–glaucophane–quartz schist yielded an age of 94.1 ± 2.1 Ma, indicating that this rock belongs to the Sanbagawa metamorphic rocks or another Cretaceous metamorphic unit. Pressure–temperature conditions estimated by phase-equilibrium modeling for the garnet–glaucophane–quartz schist are approximately 490 °C and 2.1 GPa. These data suggest that the distribution of blueschist–eclogite transitional facies in the Cretaceous metamorphic unit extends to the eastern margin of Kyushu.