A Significant structural belt termed as the "Koshidai-Takabo-Daiyu-in" one, was found in low-grade metamorphic terrain (the Gozaisyo and Hitachi metamorphics) by our researches during 1965-1977. It runs from Daiyu-in (Hitachi City) via Takabo-yama (Kitaibaragi City) to Koshidai-Takanukida villages (Higashishirakawa-gun, Fukushima Pref.) and hereby is estimated to be 70-80 km in its extension. Several diaphthoritic bodies including a small amount of alumino-silicate porphyroblasts, especially kyanite-andalusite ones, were found within the belt. The "Takabo metamorphics" is a kind of diaphthorites, which were firstly paid an attention to these petrological significance by SUGI (1938). A significance of unearthings of the "Koshidai-Takabo-Daiyu-in structural belt" and the alumino-silicate bearing diaphthoritic bodies leds to the conclusions that this belt is not a simple fracture belt but the structural one in a synthetical sense, in which the metasomatized uplifting bodies with alumino-silacate porphyroblasts, hydrothermal-metasomatic altered rocks with metal mineralization of copper and manganese and various acidic plutonics are distributed. These events seem to be related to migmatization activities taken place in certain parts of the "Takanuki metamorphics", probably of the Indosinian Orogeny. In this paper certain significances of the structural belt, kyanite-andalusite porphyroblastic diaphthorite and the "Takabo metamorphics" are mentioned.
