The Th230/Pa231 activity ratio in 7 of 11 manganese nodules is less than 10.8, the theoretical production ratio of activities in the ocean. This finding indicates difierential accumulation of these nuclides in authigenic deposits of manganese-iron oxide.

The analytical procedures for carrier-free separation of uranium, thorium, and protactinium from manganese nodules make use of 232U, 234Th, and 233Pa tracers to monitor yield. Extraction of proactinium uses diisobutyl carbinol extraction and that of uranium and thorium is perforemed using cation exchange techniques.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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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.

Supplement to: Sackett, William M (1966): Manganese Nodules: Thorium-230: Protactinium-231 Ratios. Science, 154(3749), 646-647