The Abukuma plateau, which is located along the Pacific coast of northeastern Japan, is composed mainly of Cretaceous granitic rocks and regional metamorphic rocks. In the central part of the plateau, the Gosaisho metamorphic rock series in the east overthrust onto the Takanuki metamorphic rock series in the west. The Gosaisho series is mostly composed of mafic and siliceous rocks, and the Takanuki series is mainly composed of pelitic-psammitic rocks. In the Gosaisho series, many small ultramafic bodies are present in the areas adjacent to the Takanuki series. These ultramafic rocks are affected by contact metamorphism of the Cretaceous granitic rocks in various degrees, but their protoliths are discerned as mantle peridotites and ultramafic cumulates based on their bulk rock chemistry. The ultramafic cumulates are accompanied by metagabbros. At Mount Otsube, mantle peridotites occupy the foot of the mountain and cumulates comprise its top part. The rock assemblage and geological relationship indicates that the ultramafic bodies in this area are fragments of the lower part of an ophiolite. Bulk rock chemistry of the mantle peridotite as well as its olivine and spinel chemistry suggest that the mantle peridotite is highly depleted and of island arc origin. In view of the spinel chemistry, the ultramafic rocks might be independent of the Gosaisho-Takanuki metamorphic rocks and be fragments of the early Paleozoic Hayachine-Miyamori ophiolite. However, the ultramafic cumulates are much richer in Fe (~ Fo₇₀) than those in other ophiolites in Japan. This dismembered ophiolite, which we call Furudono ophiolite, may be a new type of the Paleozoic ophiolites in Japan.