The geological processes that lead to the formation of a new oceanic crust may cause intense hydrothermal activity. This activity supports the existence of an exotic fauna in deep ocean and also forms mineral deposits. Since the discovery of the first hydrothermal field on the East Pacific Rise, there has already been found about 100 hydrothermal sites associated with important metallic sulfide deposits. These sites occur along the oceanic spreading centers in different tectonic settings, but are not continuous globally. They are localized at specific sites where hot rocks are connected to faults and fractures, creating a permeable pathway for the hydrothermal circulation. Seawater penetrates into the oceanic crust and is modified to hydrothermal fluid with high temperature (up to 400°C), low pH and Eh. This fluid interacts with the rocks leaching and transporting metals, which precipitate as massive sulfides at the seafloor or as stockwork in the subseafloor. Metallic sulfide deposits can reach considerable size ranging from 1 to 100 million tones with high concentrations of copper, zinc, lead and precious metals such as gold and silver. Some of these deposits have recently attracted the interest of the scientific community and the international mining industry. They are good examples of modern analogues for understanding the genesis of volcanic-hosted massive sulfides on land and show strong potential mining in the near future. Here we provide a review on the deep-sea sulfide deposits, focusing on its formation, methods of exploration, location and characteristics (mineralogy/metal contents) of the main sites, and also the potential mining impacts.
