Akihiko Okada

Study on the managanese nodule

Chemical and X-ray analyses were performed on the fifteen manganese nodules collected from the Pacific Ocean floor. The results were discussed compared with the previous data on the manganese nodules. Minerals were found to be todorokite, δ-MnO2 and other silicates, montmorillonite, illite, phillipsite and α-SiO2. Average composition shows that copper is concentrated on the deep sea nodules more than the shallow ones, and that the todorokite rich nodules contain more copper and nickel than the δ-MnO2 rich ones. The analyses of fresh water iron-manganese precipitates by bacterial activity suggest that biological process is one of the important factors on the genesis of the sedimentary iron-manganese deposits, including the manganese nodule.

Study on the manganese nodule V. Thermal studies of the iron-manganese phase

The thermal phase transformation of the iron-manganese phase of the Pacific Ocean manganese nodules were studied by the differential thermal and X-ray diffraction methods. X-ray powder patterns of the heated samples at the temperature of 600°C to 1000°C show the occurrence of hematite, bixbyite and cubic and tetragonal (Fe, Mn)3O4. Bixbyite produced by the heat treatment of the iron-manganese phase gives an abnormal X-ray pattern in comparison with the standard sample of bixbyite. Cubic (Fe, Mn)3O4 is produced not only by the reaction of bixbyite with hematite over 900°C, but also at the lower temperature, such as 600°C. While, tetragonal (Fe, Mn)3O4 is a reaction product of cubic (Fe, Mn)3O4 with bixbyite over 900°C in the case of manganese rich nodules. The species and quantities of the products after the heat treatment are assumed to be mostly influenced by the relative contents of iron and manganese in the manganese nodule.

Mineralogical and Petrographical Study of the Zaisho Meteorite, a Pallasite from Japan

Abstract The Zaisho meteorite, a pallasite from Japan, is primarily composed of nickel-iron and olivine, and contains minor amounts of troilite, schreibersite, chromite and farringtonite. The olivine of this meteorite is Fa18.6 in molar composition, and exhibits non-rounded morphology. About 17% of the olivines are kinked crystals. The formational temperature was estimated to be 1220 °C from the Mg-Fe 2+ distribution coefficient in the coexisting olivine-chromite pair.