Boundary between the Sambagawa and Chichibu belts in the Odai area, Mie Prefecture, eastern Kii Peninsula, Japan

Abstract

Abstract:The Sambagawa and Chichibu pelitic rocks are in direct contact in Kohtaki outcrop, which has been found out in field studies carried out in the Odai area, eastern Kii Peninsula. In the Kohtaki outcrop, it is suggested that difference in degree of metamorphic recrystallization between the two lithologies can be recognized by naked eyes, i.e. the Sambagawa pelitic phyllite is more highly recrystallized than the Chichibu pelitic mixed rock. In addition to this observation, overall difference in their constituent protolith was used to determine the boundary between the Sambagawa and Chichibu belts. The result suggests that the pelitic mixed rock in the Chichibu belt overlies pelitic phyllite in the Sambagawa belt with a moderately south dipping tectonic boundary, in contradiction with a previous study. It is also discussed that the juxtaposition of the two belts already completed by the end of the Sambagawa main deformation stage, Ds, which is associated with regional-scale E-W stretching. The Kohtaki outcrop likely preserves original structural relationships between the Sambagawa and Chichibu belts.