A vertical profile of dissolved trace metals (Al, Cd, Cu, Mn, Ni) over the median valley of the mid Atlantic ridge, 43°N: Implications for Hydrothermal activity

A detailed hydrographic station was worked over a segment of the median valley at the Mid Atlantic Ridge. Measurements of temperature, salinity, dissolved oxygen and micronutrients showed water in the valley to be well mixed below the height of the sill. In the deeper water, anomalously high concentrations of Mn were present (1.9nM at 3279 m) and these are attributed to hydrothermal activity. Concentrations of Cd, Cu and Ni did not appear to differ from those expected for this region. This is consistent with the level of Mn enrichment and what is known about the likely composition of hydrothermal fluids. Enrichment of Al occurs in the median valley to a much greater extent (40 nM at 2400 m) than would be expected from known compositions of hydrothermal fluids.