Chemical composition of manganese nodules from GH80-1 cruise

Manganiferous materials were collected at 49 stations in the Central Pacific Basin, the Mid-Pacific Mountains, the Manihiki Plateau, and the Penrhyn Basin during cruise GH80-1. Manganese nodules were selected from 40 stations for analysis. Samples were separately taken from those samplers. During sample preparation materials other than ferromanganese oxide shells such as rock nuclei were visually removed off when possible. Two subsamples were taken when a nodule has a distinct double-layered internal structure. The samples were kept in plastic containers on board for shore-based analyses and were dried in air at room temperature in a few months after the cruise. One hundred and twelve ground samples were prepared for atomic absorption spectroscopic analyses of Mn, Fe, Cu, Ni, Co, Pb, and Zn. The analyses were carried out on the air-dried powdered samples. Total water contents (H2O tot) were measured by gravimetric method also on the air-dried powdered samples. Acid insoluble fractions were not determined, though these fractions occasionally amount several tens of per cent of nodules.