Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining.

Seafloor massive sulphide samples from the Trans-Atlantic Geotraverse active mound on the Mid-Atlantic Ridge were characterised and subjected to leaching experiments to emulate proposed mining processes. Over time, leached Fe is removed from solution by the precipitation of Fe oxy-hydroxides, whereas Cu and Pb leached remained in solution at ppb levels. Results suggest that bulk chemistry is not the main control on leachate concentrations; instead mineralogy and/or galvanic couples between minerals are the driving forces behind the type and concentration of metals that remain in solution.