The manganese content of 4 manganese nodules was determined by atomic absorption. The decrease of total alpha activity was used to evaluate Mn accumulation. Because CaCO3 is a Mn-free diluent, the Mn concentration results and the nodules accumulation rate results are given on a carbonate-free basis. Nodule densities were assumed to be 2.5 g/cm³. The Mn accumulation rates are calculated per unit cross sectional area of the nodule rather than per unit surface area.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.This dataset represents the digitized Table 2 - Part 2, pp. 145 of the related publication.