2009 年 115 巻 10 号 p. 540-543
This is the first report of lawsonite in pelitic schists from the Kebara Formation, a tectonometamorphic unit exposed between the Sambagawa metamorphic belt and the Chichibu belt in western Kii Peninsula. Lawsonite and pumpellyite have previously been reported from basic schists in the Kebara Formation, suggesting high-P/T metamorphic conditions. The pelitic schists consist mainly of quartz, albite and chlorite along with minor carbonaceous matter and rare phengite, lawsonite, calcite and titanite. The mineral assemblage of the lawsonite-bearing pelitic schists is chlorite+phengite +lawsonite+albite+quartz. This assemblage is basically the same as that reported for lawsonite-bearing pelitic schists from the chlorite zone in the Sambagawa metamorphic belt, i.e. in the Ise area in eastern Kii Peninsula and in the Besshi nappe complex exposed along the Asemigawa River in central Shikoku. These various lawsonite-bearing pelitic schists probably experienced similar high-P/T metamorphic conditions suggesting that the entire Kebara Formation experienced similar high-P/T metamorphism to that of the chlorite zone in the Sambagawa belt.