Analysis of ferromanganese nodules from the North Pacific

10Be, U and Th isotopes, Ra, 210Pb, Mn, Fe and several trace elements are measured in the hydroxylamine hydrochloride leachates and residues of two ferro-manganese nodules collected from the Central North Pacific. The two nodules which are from the same location are about identical in composition. The 10Be deduced growth rates (2.3 and 3.3 mm/10-6 years) are in good agreement with those reported in literature for other nodules using independent techniques. The order of magnitude discrepancy between the integrated SUP-10 Be activity (in the nodules) with its production rate confirms the earlier explanations put forward by Bhat et al (1970). Additionally it is possible that nodule formation results from only a few hundred meters of the overlying waters. Hydroxylamine hydrochloride appears to be an ideal leachant for the authigenic components in the nodules _ the leach can conveniently be used for most of the analyses.