Amphibolite-facies metamorphic rocks of the Mt. Tenzan area, northern Kyushu, Southwest Japan: Correlation with the Higo metamorphic rocks

Abstract

The metamorphic rocks exposed in the Sefuri and Tenzan areas, northwestern Kyushu, are composed mainly of mafic rocks with trace amounts of pelitic, ultramafic and calc-silicate rocks and crystalline limestone occurring as lenses or blocks. These rocks underwent regional metamorphism prior to the Cretaceous intrusive rocks. The metamorphic rocks in the Tenzan area, south of the Sefuri area, underwent amphibolite-facies metamorphism and estimated metamorphic P-T conditions of these rocks reach up to 700 °C and 4.0 kbar. On the other hand, the metamorphic conditions in the Sefuri area have been reported to be up to 850 °C and 5.5 kbar. The metamorphic P-T-t path of northwestern Kyushu is interpreted as a clockwise trajectory. These P-T conditions and lithological features suggest that the metamorphic rocks of northwestern Kyushu can be correlated with those of the Higo metamorphic terrane, which is thought to be a candidate of the eastern extension of collision zone between the North China and the South China cratons during Late Permian to the Triassic periods.