Description, main morphological features and bulk chemical analysis of Mn deposits from DOMES sites in the Pacific Ocean

Study of the occurrence and physical and chemical character of manganese nodules collected in box cores in DOMES Sites A, B, and C indicates that virtually all nodules lie at the sediment-water interface. Buried nodules are rare. Nodules seem to be smaller and have smoother surfaces at Site A than at Sites B and C. Site C nodules are predominantly 2-6 cm in size and have smooth tops and granular bottoms. Nodules from all sites show non-uniform contents of Mn, Fe, Ni and Cu within individual box cores. The greatest variations were found in box cores from Sites A and C. Mn, Ni, and Cu are generally covariant whereas Fe content is antithetic to Mn content. Large variations in metal content are generally due to differences in oxide mineralogy but some variation is related to clay content. Large nodules tend to be relatively low in Mn, Ni, and Cu. Site B nodules have the highest mean values for Mn, Ni, and Cu and the lowest mean Fe content. Site C nodules and Site A nodules have the same Mn content, but Site C nodules are richer in Ni and poorer in Fe than Site A nodules.