The ratio of 230 Thorium excess over 232 Thorium isotopes has been determined for different layered deposit zones inside ferromanganese nodules and crusts retrieved in the South Pacific Ocean during various R/V Eltanin cruises. Samples were prepared from the nodules and crusts by peeling or scraping successive layers and measuring the resultant decrease in thickness with calipers. The samples were then ground to a fine powder and split into two aliquots, one for U and Th isotopic analysis, the other for elemental analysis. The Thorium was extracted using Thenoyltrifluoroacetone (TTA) and measured using Alpha-particle spectroscopy.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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 T1, p. 189 of the related publication.