Abstract

Sediment from the Bauer Deep in the east Pacific is commonly carbonate free, containing only small amounts of detrital minerals, and is enriched in Fe, Mn, Cu, Co, Ni, Zn, and Ba. An Fe-montmorillonite and ferromanganese compounds, occurring both as colloids and micronodules, are the principal phases present. A large proportion of the Fe occurs in the Fe montmorillonite, which appears to originate from the interaction of hydrothermal solutions with sea water. Adsorption and incorporation of metals from sea water on the micronodules or the Fe and Mn oxide colloids best explain the elemental relationships observed for Fe, Mn, Cu, Zn, and Ni in the oxide fraction of the sediment. These processes are responsible for the enrichment of the sediment in Ni, Co, and possibly Mn. Enrichment in Cu and Zn occurs in both the oxides and the Fe montmorillonite.

Sedimentation rates measured in one core provide a minimum value of 2.5 mm/103 yr. The rate of accumulation of authigenic material is more than 2 mm/103 yr. Elemental accumulation rates of Fe, Mn, Cu, Ni, and Zn are comparable to those found near the crest of the East Pacific Rise.

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