ABSTRACT

Physical studies such as differential thermal analysis, thermal gravity analysis, infrared absorption and thermal transformation of mineral phase have been carried out for terrestrial ferro-manganese nodules formed in limestone areas of the Ryukyu Islands. The differential thermal analysis data indicate that they are grouped into four different types regardless of indistinct patterns of X-ray diffractometry. The first group shows endothermic peaks at near 120, 320 and 560°C. The second goup is close to the first group except showing a quite enhanced endothermic peak at 320°C. The third type of nodules shows one more additional endothermic peak at near 800°C. The final fourth group shows only two endothermic peaks at near 120 and 560°C. The X-ray diffraction patterns for heated samples at various temperatures indicate that magnetite is formed at temperatures over 700°C. Braunite also seems to be formed at the same temperature range but it disappears at 1, 000°C. The mineral composition of the manganese nodules has been also discussed by the study of infrared absorption patterns with particular reference to quartz, goethite, amorphous state of ferrihydrite and artifitially formed silica gel.