The nodules used in this study were collected from two cruises in the western North Pacific by box coring (KH-79-4) and dredging (GH-78-1). After being dried at 110°C each sample extracted from the top, side and bottom of the nodule at various penetration levels were radiochemically analyzed for their Thorium isotopes contents by digesting about 100mg of a nodule sample without application of the successive separation treatment. Thorium in the solution was purified with an anion exchange resin and chemical separation techniques, and electrodeposited onto a silver disc from a hydrochloric acid and ethanol solution. The alpha activities of 228Th, 230Th and 232Th were counted with a spectrometer equipped with a surface barrier silicon detector. The chemical yield was determined by counting the 0 activity of 234Th added before the analysis. The yield ranged from 80 to 95%.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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 3 (pp. 206) of the related publication.