The samples analysed were dredged on Pleiades Leg II during a program of heat flow measurements, bottom photography and coring. They are located on topographic mounds in a band 20 km south of the Galapagos Rift on sediments ranging from 20 to 30 m in thickness. The dredge hauls were sampled to represent the diversity of dredged material either Mn encrusted altered basalt or relatively thick Mn coating deposited directly in contact with sediments. Each sample was analysed by atomic absorption spectrophotometry for major elemnts and instrumental neutron activation analysis for minor elements or rare earths.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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 1, pp. 14 of the related publication.