Metapelite, metapsammite, and metachert of the Ryoke metamorphic belt are widely distributed in the Dando-san area, Aichi Prefecture. These rocks are intruded by the Kamihara tonalite (Older Ryoke granitoid) in the southwestern part of the area and by the Busetsu granite (Younger Ryoke granitoid) in the northern to northeastern part. The mapping of metamorphic zones, based on metapelite mineral assemblages, reveals two large-scale thermal structures unrelated to the distribution of granitoids in the area. The metamorphic grade increases from the central part of the area toward the southeast in the first structure, and from the center toward the northwest in the second one. The first thermal structure is considered to have formed during Ryoke regional metamorphism, on the basis of inter-tectonic growth of andalusite without K-feldspar, and from comparison with the metamorphic zonation in the Hongu-san area located in the south-western direction. In contrast, the occurrence of post-tectonic andalusite coexisting with K-feldspar in the northwestern part of the area shows that the second thermal structure was produced under lower pressure conditions after regional metamorphism. This metamorphic event may have produced finegrained, high-grade metamorphic rocks that formed during a rapid increase in temperature.
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