Iron-manganese crusts were chosen from existing collections in order to cover as wide an area and depth range as possible. Sampling was concentrated in the Central Pacific seamount provinces where crusts are most commonly found coating lithic substrates. Two Mn nodules from similar areas were also sampled for comparison. Sub-samples were taken for isotopic analysis from known depths within individual crusts and nodules either by use of a stainless steel dental drill or by chipping away surface oxide layers. After grinding in an agate pestle and mortar, authigenic Fe-Mn oxides were leached with warm 25N HCl Solutions were evaporated to dryness and Nd isolated and analysed isotopically. All ratios were normalized to a 143Nd/144Nd ratio of 0.7219, and repeated analyses of the La Jolla standard gave an average value of 0.511847 ± 21 (unweighted).

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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 is digitized from Table 1, pp. 8 of the linked publication.--Comment: e-Nd = [ ((143Nd/144Nd)Sample - (143Nd/144Nd)CHUR) / (143Nd/144Nd)CHUR)] * 10000 where CHUR stands for "chondritic uniform reservoir" at 2.5 Ga