Compositional variations in manganese nodules collected from the North Penrhyn Basin

Manganese nodules collected from the North Penrhyn Basin are characterized by low content of Mn and Fe, medium content of Ni and Cu, and medium Mn/Fe ratios. The average content of Ni plus Co is 1.11%, maximum 1.89%. Ni content slightly exceeds the Cu content in the nodules. Ni and Cu are strongly correlated with Mn, whereas Co is strongly correlated with Fe. Nodules containing Ni+Cu+Co near or in excess of 1% are rich in Mn and have a high Mn/Fe ratio. Those with highest content of Ni+Cu+Co are concentrated at or near the carbonate compensation depth. Nodules metal contents vary with latitude and have a reciprocal relationship with abundance. Contents of Mn, Ni, Cu and Ni+Cu+Co are high in nodules found at 2–6°S and vary decreasingly toward 1°N and 12°S, whereas Co content varies increasingly from 2°S towards 12°S. Nodule compositional variations with latitude are controlled by biological productivity, carbonate compensation depth, sedimentation rate, and bottom current.