Major element analyses of manganese nodules from the Southwestern Pacific Basin

Initial attempts to classify the composition of manganese nodules in the Pacific Ocean illustrated the paucity of data for the Southwestern Pacific Basin. Recent major element analyses of 16 manganese nodules from different stations in the Southwestern Pacific Basin collected during the 1974 R. V. Tangaroa cruise are presented. They have shown high contents of elements associated with the silicate phase of nodules (36—54% as oxides on a dry weight basis). The high contents o f the elements may be due to the incomplete replacement of the volcanic nuclei of the nodules by iron-manganese oxides in the initial stages of nodule formation. Some elements (e.g. Na, Mg, Si and Ti) show particularly wide variations in composition in these nodules. Chemical analyses were performed on bulk nodule samples (including nucleus) using X-ray fluorescence spectrometry. Samples were ground in a SFEX mill grinder and ignited at 1000°C in a Pt crucible to drive off volatiles. They were then reduced to a glass bead and reground for analysis.