Studies on diffusion and profiles of elements in deep-sea manganese nodules

Elemental compositions are measured in manganese nodules collected from the Northern Mid-Pacific floor by inductively-coupled plasma atomic emission spectrometry (1CP-AES) and their growth rates are determined by radiometric methods.The result shows that depth distributions of elements in nodules vary with depth as follows; (ⅰ) increase, (ⅱ) decrease and (ⅲ) fluctuation.These internodule variations in elemental compositions are considered to be caused by diffusion and migration of elements in nodules and heterogeneities in textures of nodules.In the present paper, a diffusive model is used to elucidate the inward-increase profile of some elements in nodules.The effective diffusive coefficients are estimated to be of the order of 10^-9 cm²/a for Ni, V and Zn in the nodules, which is less than the value reported for radionuclides.