Internal constitution of manganese nodules from the Central Indian Ocean Basin

17-19Morphological, chemical, physical and acoustic properties of Mn-nodules in the Indian Ocean are inter-linked and depend much on local and regional oceanic environments. These nodules are anisotropic and sound propagation is faster parallel to their elongation. Denser nodules show low attenuation. Density and P-wave velocity in nodules increase significantly on saturation with water. Nodule density is related directly to nodule size, P-wave velocity and Mn/Fe ratio; and inversely to water content, attenuation and Co concentration. Nodules with rough surface from siliceous clay region record highest density, P-wave velocity and Mn/Fe ratio