Kaoru Oinuma

The distribution of clay minerals in the recent sediments of the Japan Sea

Abstract Investigation of 81 surface sediment samples from the Japan Sea and six from four rivers in Japan leads to the following conclusions: the distributions of clay minerals such as montmorillonite, chlorite, illite and kaolinite are strongly influenced by the supply or transportation, or both, of fine-grained materials by two water systems. River runoff from Japanese islands and the Asian continent is particularly important, and the Tsushima Warm Current that flows northeastward in the Japan Sea is also influential.

The distribution of clay minerals in recent sediments of the Okhotsk Sea

Abstract The clay fractions of surface sediments from the Okhotsk Sea contain montmorillonite, chlorite, illite, and small amounts of kaolinite. The concentrations of these minerals differ from place to place, but they are not determined by submarine topography such as basins and rises. The distribution seems to be influenced mainly by the supply of clay minerals from volcanic materials, various rocks, and soils in the bordering lands.

An Interstratified Chlorite-Vermiculite in Weathered Red Shale Near Toyoma, Japan

Abstract An interstratified chlorite-vermiculite altered from chlorite by weathering is found in the weathered red shale near Toyoma in Miyagi Pref., Japan. This mineral shows a very strong reflection at 14.7a with an almost regular series of basal reflections, but does not show a reflection with a long spacing. The characteristic behaviour of the basal reflections after various treatments shows clearly the presence of chlorite and vermiculite layers in this mineral. The ratio of chlorite layer and vermiculite layer is 1:1 in the mineral. The structure of this mineral deviates from a 1:1 regular interstratification of chlorite and vermiculite layers, but is not a completely random one. Dehydration of the vermiculite layer occurs mainly at about 56-83°C and 159°C, and dehydration of the hydroxyl sheet in the chlorite layer occurs at about 555°C. The chemical formula obtained for the mineral is 11.2SiO 2 4.2A1 2 O 3 8.7MgO 3.OFe 2 O 3 10.6H 2 O. Cation exchange capacity is estimated to be 60meq/100g and the calculated interlayer charge of vermiculite layer is 1.01 on the basis of a O 2o (OH) 4 unit.

Clay mineral composition in shallow water sediment samples near the Antarctic Peninsula and in deep-sea core samples from the pacific and the Indian-Antarctic Basins

Clay minerals in seven shallow water (100 to 600 m deep) dredged samples and in two deep-sea (3,000 to 5,000 m deep) core samples near West Antarctica were investigated by X-ray diffraction analyses. Variation of montmorillonite concentration appears to be closely related to volcanic activity. Chlorite is the most dominant constituent in most of the dredged samples, though it is not a principal component in core samples. Illite concentration is negatively correlated to that of montmorillonite. Kaolinite is found in four out of seven dredged samples near and around the Antarctic Peninsula while the content of kaolinite in two deep-sea cores from the Pacific-Antarctic Basin and the Indian-Antarctic Basin is more abundant than in the dredged samples. The clay mineral composition in the latter two basins may be closely related to volcanic activity and mechanical weathering products near and on Antarctica.