Abstract
Tectonostratigraphic relationships and paleontological evidence suggest a post-Middle Jurassic depositional age for the protoliths of the Sanbagawa psammitic/pelitic schists. In order to identify the parentage of low-grade metasediments in the Sanbagawa Metamorphic Belt in the southern area of Mima City, Tokushima Prefecure, we have studied the bulk chemistry of psammitic and pelitic schists in the Sanbagawa Belt. The Sanbagawa Belt in the study area can be divided into northern and southern parts on the basis of lithology and structure. Some geochemical signatures of psammitic schists differ from those of the Middle/Late Jurassic sandstones in the Southern Chichibu Belt. The geochemistry of the psammitic and pelitic schists suggests that the parents of the northern and southern parts are the KS-II Unit (Coniacian-Campanian) and KS-I Unit (Albian?-Early Coniacian) of the Northern Shimanto Belt, respectively. These conclusions imply that most of the low-grade metasediments of the Sanbagawa Belt in Shikoku are an underplated, deeper facies of the Cretaceous Shimanto accretionary complex.
