CHARACTERISTICS OF BAND STRUCTURE IN IRON-MANGANESE NODULES FROM YELLOW-BROWN SOIL IN WUHAN
武汉黄棕壤中铁锰结核的环带构造、元素富集特点与环境变化意义

Band structure in iron manganese nodule reveals cyclic changes of the environment under which the nodule was formed. Some element contents were measured using scanning electron microscopy equipped with energy dispersive X ray analyzer. Scanning from the edge to the center of the nodule showed the irregular band structure. The fluctuation of the contents of main chemical components, SiO 2, Fe 2O 3 MnO 2 and CaO was found along the section of nodule. CaO is usually located at the outmost part of each band. At least 10 cycles of fluctuation can be seen indicating seasonal water logging during the time of nodule formation. It was suggested that at the beginning of nodule growth it is in weak seasonal water logging but later on it was in strong seasonal water logging. Accumulation of Ba, Ca, Co and Pb in the nodule is associated with Mn. And that of Ni and P is associated with Fe based on the factor analysis.