ABSTRACT
This chapter focuses on deep-sea mining, i.e., activities related to seabed and subsoil minerals located in water deeper than 200 m. There are many scientific challenges in common related to both shallow and deep-sea minerals. The process of nodule formation involves precipitation, around an initial core, of metal complexes dissolved in seawater or present in the surrounding sediments. Their growth rate is slow, only several millimetres per million years. Hydrothermal vent systems are the result of seawater circulating in the ocean crust under the influence of a heat source. Cobalt-rich ferromanganese crusts are found in all oceans on hard, essentially volcanic, substrates in environments with low sedimentation rates. Like nodules, they are formed by the precipitation of metal complexes dissolved in seawater. Hydrothermal vent systems are generally not detectable with multi-beam echo sounders from the sea surface. However, strategies to explore for hydrothermal activity include searching for physical and chemical anomalies in the water column.
