麻豆传媒

ROBERT GOODDEN has waited 30 years for this moment. Perhaps not surprisingly, he is a little apprehensive. 鈥淪eldom have I been in a place where the consequences of a 鈥榶es鈥� are so significant, and of a 鈥榥o鈥� so dreary,鈥� he says. 鈥淭he whole world will be watching.鈥�

This month, Seacore, the company Goodden heads, will send its drilling ship to the waters around Papua New Guinea and the North Island of New Zealand. There it will drill as deep as 2000 metres beneath the surface to test the thickness of volcanic ore deposits.

If they are 15 metres thick or more, mining these deposits for gold, zinc, copper, silver and lead could well be commercially viable, and a new industry will be born, one that is touted by some as less intrusive and less environmentally destructive than mining on land. The mineral wealth of more than 70 per cent of the Earth鈥檚 surface is potentially up for grabs, and the mining companies of the world are well aware of it.

Environmentalists are also watching closely. Ocean mining, they say, will add a burden of pollution, noise and dust that could devastate fragile ecosystems about which we know precious little. Whichever way you look at it, there is a lot riding on those 15 metres.

This isn鈥檛 the first time that ocean mining has caused a stir. The first serious attempts to harvest the mineral wealth of the oceans began in the 1960s, when a sharp increase in demand for copper, nickel and cobalt sent prices sky high. But then a potentially lucrative new source of ore was discovered in potato-sized manganese nodules scattered over the ocean floor at depths of between 4000 and 6000 metres. More accurately known as polymetallic nodules, they are made up mainly of manganese, with smaller quantities of nickel, copper, cobalt, iron, silicon and aluminium. As they were mostly found in international waters, they attracted interest from all over the world in the 60s and 70s, and as much as half a billion dollars were sunk into developing technology for mining and processing them. Four private multinational consortia were formed, and government-sponsored enterprises sprang up in the Soviet Union, China and India. Field trials began in the early 1970s using remote-controlled dredges to scoop up the nodules from the depths.

But before nodule mining really got off the drawing board, major new nickel and copper deposits were discovered on land, and the expense of operating deep under the sea began to look excessive, particularly in light of the rise in oil prices as a result of the 1973-1974 embargo, which made travelling to remote parts of the ocean much more costly. Ocean mining was given up as a bad job, and no one has made any serious attempt to try again, until now.

This time, though, the target is different. Rather than gathering large numbers of tiny nodules, potential miners are looking for large areas of volcanic deposits known as sea floor massive sulphides (SMS). These deposits are produced by hydrothermal vents 鈥� underwater geysers that spew hot, metal-rich fluid (see Diagram).

As seawater percolates down through fractures in the Earth鈥檚 crust it is heated by the magma beneath, dissolving zinc, lead, copper, gold and sulphur as it moves through the rock. When the heated fluid is forced back out into cold seawater at temperatures of up to 350 掳C, these elements precipitate out, mainly as black sulphides, forming tall, conical chimneys. In time, these chimneys topple over, leaving piles of metal-rich deposits which recrystallise into mounds of SMS.

Geologists first became interested in SMS deposits in the 1980s, when they noticed remarkable similarities with volcanogenic mineral deposits on land. Some of these land deposits, such as Kidd Creek in Canada and Mount Isa and Broken Hill in Australia, were of enormous economic importance, so a team led by Ray Binns from CSIRO, Australia鈥檚 national research organisation, in collaboration with sea-floor geologist Steve Scott from the University of Toronto, Canada, began to study active vents in situ. They had the idea that many of the major terrestrial deposits had originally formed under the ocean in a similar way, so understanding the process would give vital clues about what to look for on land. There was little interest in mining SMS deposits at the time: at about 200 metres square and typically much less than 10 million tonnes in quantity, most mining companies quickly dismissed them as too small to be economic.

Then, in the mid-90s, 鈥渢he penny finally dropped鈥�, says David Heydon of Sydney-based Nautilus Minerals, one of the firms employing Seacore to drill off New Guinea, while London-based Neptune Minerals funds the New Zealand project (see Map). To mine a mound on the seabed there is no need to sink shafts or build the kind of infrastructure that is used on land. All the equipment needed can be packed up and moved from place to place, and from mound to mound. As a result, small can be economic. 鈥淚nstead of needing a minimum deposit size of, say, 20 million tonnes for your investment to be economic, as on land,鈥� says Heydon, 鈥測ou could mine 10 sites of 2 million tonnes.鈥�

High stakes

Another plus is that deposits are often relatively close to land, within territory controlled and regulated by a single country, which provides greater certainty over ownership than international waters (see 鈥淲ho owns the sea?鈥�). It also puts them within striking distance of smelters, many of which are located on the coast. And most SMS deposits lie in less than 3000 metres of water, depths at which oil and gas producers and cable layers have been working for decades, so the technology to exploit the deposits is already at hand. And since shipping is the cheapest form of bulk transport, it would be relatively easy to move the haul around.

To back up the idea that ocean mining could actually be cheaper than land mining, Nautilus Minerals commissioned international consultants Worley Parsons Engineering to undertake a nine-month study to check out the costs. The conclusion: it was doable. For copper alone, it could cost about half the price of developing a 鈥済reenfield鈥�, land-based mine. 鈥淚n fact, we should have been doing it 10 years ago,鈥� Heydon says.

Even so, the stakes are high. Canadian company Placer Dome, the world鈥檚 fifth-largest gold mining enterprise, agreed to foot the bill for the exploration of the 15,000 square kilometres of Papua New Guinea territorial waters for which Nautilus holds licences. Between January and March this year the company spent $2.7 million on a geophysical exploration programme, and will also be putting up $4 million for the core drilling programme. This has given 鈥渕arket cred鈥� to the push into ocean mining, and in return the company gets a maximum 75 per cent interest in any gold-rich deposits uncovered, while Nautilus retains rights to all the non-gold deposits, in particular the copper.

But as the ocean mining fraternity gets ready to start drilling, environmentalists are becoming increasingly concerned. Active hydrothermal vents, they argue, are unique ecosystems which, despite nearly 25 years of research, are still poorly understood.

鈥淭hese sites are potential reservoirs of unexpected and complex biodiversity, and we have no inventory of them,鈥� says Craig Cary, professor of environmental technology at the University of Waikato in Hamilton, New Zealand. 鈥淚t would be like cutting down a rainforest and then trying to figure out what you have destroyed.鈥� Cary is a trustee of TerraNature, a US and New Zealand-based conservation group that campaigns for tighter regulation of ocean mining activities along the Kermadec ridge to the north-east of New Zealand鈥檚 North Island. This is the area where Neptune Minerals have commissioned Seacore to start drilling.

鈥淚t would be like cutting down a rainforest and then trying to figure out what you have destroyed鈥�

Not a problem, say Heydon and his opposite number at Neptune, Simon McDonald. For a start, both companies say they are only interested in exploring and mining the mounds at inactive vents. Quite apart from the conservation concerns, they say, they need to protect their expensive drilling equipment from hot, probably corrosive fluids.

What鈥檚 more, active sites, by definition, are still being formed and are therefore likely to be immature and small. And why kill the goose when it is in the process of laying more golden eggs?

That may be, says Cary, but active and inactive vents are often clustered close together and the chimney rock is soft and brittle 鈥� about the consistency of coal. Having studied hydrothermal vents for more than 20 years, he is concerned that the technology to be used for mining will inevitably have an effect on life nearby.

While neither enterprise has yet decided on the exact technology to be used, Heydon and McDonald both talk in general terms of remote-controlled machines similar to those used in coal mining. They would have rotating, spiral cutting heads that would break the rock into tennis ball-sized chunks to be sucked up through a pipe to a semi-submersible platform on the surface. There the ore would be dewatered and loaded onto bulk carriers to be taken to the smelter. Alternatively, in shallower waters, the rock might just be 鈥済rabbed鈥� from the surface. These sorts of technologies are already used in diamond mining, albeit in relatively shallow water off the coast of Namibia.

The concern with this method is that it might create plumes of particulate sediment that would clog the delicate gills and filters used by sea creatures to extract oxygen and food from the water. Environmentalists also worry about the impact of noise, particularly on passing whales, dolphins and fish in the seamount area off New Zealand.

Mining advocates counter such arguments by saying that life is sparse in the neighbourhood of inactive sites. Plus, they say, the species living there are good colonisers that are highly adapted to surviving in the face of seismic events and lava flows. 鈥淚 once saw a vent community recently rolled over by a lava flow,鈥� Scott says. 鈥淭ube worms were sticking up from under the lava, and bacteria were already growing on the surface of the flow.鈥�

Going for gold

In addition, say McDonald and Heydon, there is little likelihood of damage from particulate plumes for several reasons. There isn鈥檛 much silt in the ridge areas where they are likely to mine, and the machinery will be designed to suck up any sediment created, they say. As for noise, the cutting equipment is likely to be powered and controlled from the surface, as are the air compressors needed for lifting.

So far the argument is showing no signs of being resolved, but with so much at stake, the companies insist that they are at considerable pains to get things right first time, and that means doing everything they can to minimise the impact on the environment.

First though, Goodden and his team have to prove that mining the deposits will be worthwhile, and they won鈥檛 know that until they drill those cores. 鈥淲e know there鈥檚 the potential of some hard crust material, but nobody really knows what鈥檚 below that. We are taking the best equipiment we can find, and expect to feel our way carefully.鈥�

If they are successful, the race will be on to find the next potential sites, and that鈥檚 where things get tricky. The most difficult job in mining SMS deposits is finding them in the first place. 鈥淲e know where the vents should be 鈥� on mid-ocean ridges and potentially all around the Pacific 鈥榬ing of fire鈥� 鈥� but in practice finding them is difficult,鈥� says Alister Skinner of the British Geological Survey in Edinburgh. 鈥淭hese chimneys may be up to 100 metres in extent 鈥� but that鈥檚 pretty small in the grand scheme of the ocean.鈥�

Geologists may be able to give a heads-up on where active vents are, and therefore where deposits are likely to be found, but exploration for SMS deposits is still very much in its infancy. For example, Justin Baulch, an exploration geologist at Placer Dome, and his team used a battery of geophysical techniques to try to map the extent of the Papua New Guinea deposits. These included deep-towing instruments to profile the surface using sonar and video, and instruments to measure the magnetism, electrical resistance and even gravity of the sea floor. Although they were encouraged by the results, Baulch admits that some techniques were more successful than others.

Whatever the outcome of the drilling programme, it looks as though ocean mining will eventually become a reality one way or another. Government agencies from China, Japan, India, South Korea, Russia and several other countries are busy combing parts of the Pacific and Indian oceans, once again looking for manganese nodules.

Either way the message is clear: 鈥淚f the economics are right,鈥� says Heydon, 鈥渨hatever needs to be done, will be.鈥�