Economic potential of sea-floor massive sulphide deposits: ancient and modern

Land–based massive sulphide deposits are of major importance to world mining and world commerce. Major products are base metals (copper, zinc, lead, tin), precious metals (gold, silver), and a number of special metals (e.g. indium, gallium, germanium). More than 100 modern analogues of massive sulphide deposits and hydrothermal systems are presently known at the modern seafloor, including some very large accumulations of metals such as in the Atlantis II Deep in the Red Sea, at Middle Valley at the Juan de Fuca Ridge, and in the TAG deposit at the Mid–Atlantic Ridge. Currently, mining of hydrothermal deposits at the seafloor appears to be most attractive for sites with (1) high gold and base metal grades, (2) site location close to land (i.e. within the Exclusive Economic Zone), (3) shallow water depth not significantly exceeding 2000 m (although the technology exists for mining in deeper water). The environmental impact will be minimal at those sites, which are inactive (i.e. not inhabited by vent fauna) and are not covered by sediments (no creation of sediment plumes due to mining activities). Some of the most prospective gold–rich deposits have been found in the territorial waters of Papua New Guinea. If drilling proves that mineralization extends to depth, these deposits may become the first marine mine sites for gold and base metal sulphide mineralization