Hot springs ("black smokers") on the deep ocean floor are accumulating economic concentrations of copper, zinc, lead and silver sulfides, together with gold. Mining of these deposits is on the verge of becoming a reality, driven by the ever increasing need for raw resources, especially copper. Two entrepreneurial companies have exploration licenses covering vast areas of the seabed in the western Pacific targeting seafloor massive sulfide deposits. A third company is being established. Technological and financial challenges for recovery of seafloor sulfide deposits are not insurmountable and mining these may be less environmentally deleterious than mining on land.


Oceans and seas cover 71 % of Earth, equivalent in surface area to the sum of twice that of Mars plus twice that of our Moon. The surface area of the Pacific Ocean alone is twice that of all the continents. Both the shallow continental margins and the deep ocean basins harbor mineral resources, many of whose economic potential and especially those in the deep basins, we are only beginning to appreciate. The main potential metallic mineral resources are manganese nodules, manganese crusts and polymetallic seafloor massive sulfides. The latter deposits of iron, copper, zinc, lead, silver and gold are the subject of this paper. Although seafloor massive sulfides have been known for four decades, that they might be commercially exploited is a relatively recent idea. The author first expressed this possibility in 1984 (Dotto, 1984; see also Scott, 1985, 1992, 2001) but concluded that the deposits held more value then as natural laboratories in order to learn better how analogous deposits being mined on land may have formed as an exploration aid to finding more. All of this changed over the last decade as entrepreneurial companies saw the possibility of economic exploitation of massive sulfides on the seabed.

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