Interest grows in under-sea minerals

Press, 4 March 1981, Page 16

Interest grows in under-sea minerals

From the “Economist,” London. '

Commercial interest in deep-sea minerals is being given a shot-in the arm by new laws in developed countries. Tired of waiting for an international law of the sea from the United Nations, several European countries' are following America’s, lead in passing national laws to govern deep-sea mining. But nobody is going to get | rich quick. The technology for j deep-sea mining is ill proven f and the economics precarious, > Even if the projects under ? consideration go ahead, they | will not make a large differ-1 ence to world mineral re- a sources. ' I Three types of mineral re- ?. source are arousing interest:-' managanese '• nodules, hot springs in the Red Sea and hot springs along mid-ocean ridges. The Red Sea minerals are the only ones that look reasonably close to exploitation. The Red Sea itself is the creation of a geological rift slowly pushing Africa and Arabia apart; The rifting process generates hot springs on the sea bottom, two i kilometres beneath the surface. I These springs carry, from the V interior of the earth, metals and other materials that then rain down on the seafloor, forming a mud that is rich in i zinc, silver and copper.

* Especially interesting is a Red Sea area of about 60 square kilometres- called the Atlantis II deep. Sudan and Saudi Arabia have formed' a joint commission for its exploitation. The Saudis have. financed about ?30M worth of studies (supervised by. French consultants) with Preussag of Hanover, West Germany, as the main contractor for devel-, oping the technology. The mud is very sticky and has to be diluted so that it can be sucked aboard a drilling ship. There, air and special flotation chemicals are injected into the muddy broth; metalliferous particles stick to the air bubbles to form a froth that can be skimmed off for land-based processing. The remaining mud is pumped deep into the sea where, arguably, it will do no harm to the Red Sea’s beautiful and, for the tourist and fishing industries, important coral reefs. Many scientists are highly sceptical about claims that no harm will be done. ; Preliminary experiments : testing the feasibility of mining' have been successfuL Pilot- < scale; mining operations could take place in 1983 and will be needed before feasibility can be finally assessed. So far the • economics look quite promis- !

ing. If fall-scale mining does go ahead, the main product would -be 60,000-80,000 tonnes of zinc a year — a mere 1 per cent of present world production. The deep-sea minerals that have attracted the most publicity are manganese nodules. Wide areas of the ocean floor are littered with these potatosized nuggets which contain nickel, copper, cobalt, molybdenum and manganese. Five industrial consortia have spent . around ?300M between them exploring the commercial potential of nodules. At least as much again would .be needed for the next stage of pilot studies. A consortium of the consortia might be an attractive way of pooling these development costs — except that each consortium has been developing a different technology. Would the effort be worth it? A recent estimate is that the real prices of the metals involved would have to rise 70 per cent for the companies to attain a 20 per cent rate of return. The “safe bet” is that nodule mining will not be attractive till the 1990 s (if at all). Even then, cobalt would be the only mineral representing a significant share of world production. Even more speculative commercially are the minerals being spewed by hot springs along sea-floor ridges in the S mid-ocean. It is true that depo-

sits containing up to 20 per cent of “useful” metals have been found. But these deposits are small, isolated and difficult to find even in a submersible. They would also be difficult to mine. The interesting minerals tend to be found at sites where the water containing them is exceedingly hot (around 350 deg. C), hot enough to melt parts of any of today's submersibles.

Exploration of these hot yents has only recently begun in earnest. France and the United States are particularly active in research. But the importance seems more scientific than commercial, though the science may eventually lead to commercial spin-offs. Among the puzzles deepocean scientists are tackling are the following: . How do rich ore deposits get

formed? Many of the best landbased'deposits are thought to have been created by hot vents when these land areas were once at the bottom of the sea. Studying hot vents could provide clues for mineral exploration on land. How is oil formed? Some vents may give scientists a chance to watch oil being created. These vents occur in the Gulf of California, where the Colorado River has left huge deposits of mud. The vents apparently cook organic matter in the mud, making an oily scum of petroleum. Why is the sea salty? It used to be thought sediments carried by rivers were the main source of salt in the sea. Now it seems that hot vents may be a more important source of salt In which case, why is the sea not saltier than it is?

Why are manganese nodules so plentiful? This is perhaps the most bizarre puzzle. There is strong evidence that nodules grow only a few millimetres every 100,000 years. There is equally strong evidence that sediments are accumulating on the ocean floor much faster, by as much as one millimetre per 1000 years. So scientists are at a loss to explain why the nodules are not buried in mud. One preposterous-sounding explanation is that maybe animals roll the nodules around. Tell that one to the sharks.