The successful drilling on Legs 51, 52, and 53 created a rare opportunity to investigate the long-term effects of seawater-rock interactions on the mineralogy and chemistry of basalts erupted on the sea floor. The purpose of this paper is to describe the weathering of the basalts in terms of the changes in their mineralogy and chemistry, and to compare the weathering observed in Hole 418A with that in the upper parts of Hole 417A.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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: Humphris, Susan E; Thompson, Robert N; Marriner, Giselle F (1980): The mineralogy and geochemistry of basalt weathering, holes 417A and 418A. In: Donnelly, T.; Francheteau, J.; Bryan, W.; Robinson, P.; Flower, M.; Salisbury, M.; et al., Initial Reports of the Deep Sea Drilling Project, U.S. Government Printing Office, LI, LII, LIII, 1201-1217