Abstract

Supply of metals to manganese nodules in the south equatorial Pacific is heavily dependent on variations in biological productivity. In the northern part of the Aitutaki-Jarvis transect, under high biological productivity in the surface waters, there is a high flux of Mn, Ni, Cu and Zn to the nodules diagenetically cycled through the interstitial waters of the uppermost sediments, together, in the nodules, with the formation of 10Å manganite. To the south of the high productivity zone, these elements decrease in the nodules at the expense of Fe, CO and Pb of hydrogenetic provenance and δMnO2 is more abundant. However, nodule compositions also reflect the position of the deposits relative to the carbonate compensation depth (CCD), which deepens northwards throughout the region, with Mn, Ni, Cu and Zn being enriched in 10Å manganite bearing nodules from near the CCD under high productivity waters and Fe, Co and Pb being more abundant in X-ray amorphous or δMnO2-bearing nodules away from the CCD and/or in the south of the transect under low productivity waters.

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