Abstract
The district lies on the northeastern end of the region of crystalline schists north of Tokyuama., The schists belong to the Sangun-Motoyama Group, which is a metamorphic, facies of the Palaeozoic Chichibu rocks in the Inner Zone of Southwestern Japan., The crystalline schists of the district are due to the regional type of metamorphism., They are composed of graphite-sericite-schists of argillaceous rock origin, sericite-chlorite-schists of arenaceous rock origin, quartz-schists of chert origin and green-schists or green-rocks., Two large masses of green-rocks at Deai (D in Fig., 1) and Miyanokushi (M in Fig., 1) are represented by coarse-grained albite-epidote-gabbros in the centre, and the marginal parts exibit some schistosity., Compared with the metamorphic grade of schists of the district, these two masses of green-rocks may be synkinematic intrusives of spilitic nature., Near Meotobuchi (Mb in Fig., 1) is a green-schist carrying relic minerals, only sample in the district showing basic igneous rock., Stilpnomelane group of minerals is universally found in green-rocks of the district, but the metamorphic differentiation is not distinct., The district is cut from SW to NE by an overthrust, which is named Kitayama overthrust in the adjoining Sugane district to the west., The overthrust can be traced to the WSW about 70 m, and may safely be regarded as the western continuation of the oga overthrust in the Nariwa district, Okayama prefecture., Kawayama ore body lies in the crushed zone of the hanging wall of the overthrust., The shape of ore body is almost parellel to the thrust plane., Synclinal axes of the northern and the southern parts intersect near the Kawayama ore body on the overthrust.,
