Progress in marine hard mineral exploration and exploitation has been severely restricted by technologic gaps and the lack of discovery of deposits that can be exploited at a competitive price in the world markets. Immediate needs include improved techniques of placer drilling to permit more reliable evaluation of in situ deposits and improved systems of dredging and processing in greater depths of water and in heavier seas.
New exploration techniques for locating and characterizing the subsurface deposits, and breakthroughs in low-cost methods for rapid detailed three-dimentional mapping of the seafloor relief similar to the photogrammetry breakthrough on land, would offer new incentives to industry.
Advances in solution mining, in situ extraction techniques and rapid excavation with the possibilities of sub-sea entry, could eventually shift the emphasis in ocean mining from near shore placers to large-scale exploitation of deeply buried consolidated deposits.
The techniques currently used in sub-sea mineral exploitation, and, to some extent, in exploration, differ for the different types of mineral occurrences. These types include:
the unconsolidated surficial deposits on and immediately beneath the sea bottom, such as placers of heavy metals, construction aggregate materials, and deep water nodular deposits, which can be mined by dredging techniques,
the subsurface deposits of soluble minerals and fluids, such as salt dome sulfur, geothermal energy, and bedded salt and potash, which can be recovered through bore holes, and
the consolidated sub-surface deposits, such as coal, certain types of iron ore, and other metallic deposits in lode and veins, which at present can only be exploited by conventional underground mining with shaft entry from the coast or artificial islands.
In recent years offshore dredging of unconsolidated surficial deposits has become the most publicized facet of marine mining, largely because of the sudden awareness of the future importance of the oceans as a source of various types of minerals, because of the exciting development in the exploitation of offshore diamonds in Southwest Africa, and because of the surficial deposits having the potential for low capital investment, quick returns, high profits, and the advantage of operational mobility of the floating dredges. Over 65 nearshore dredging operations are currently active in exploiting the surficial deposits, such as diamonds, gold, tin, iron sands, titanium sands and other heavy minerals, lime shells, and sand & gravel (Cruickshank, 1968). But the world1s production of offshore surficial deposits, now with an estimated total annual value of about $227 million, has not shown any large increase during recent years, and publicity has a tendency to over-emphasize some of the smaller, if more romantic and newsworthy operations (Cruickshank et al, 1968). It is even surpassed by sub-sea underground mining of coal and iron ore, which has an estimated annual value about $352 million. Indeed, despite intense interest in sub-sea mining, most of the new activities in recent years, with the exception of offshore sulfur which had a production value of $37 million in 1967, have remained in conceptual and exploratory stages.