A black smoker hydrothermal vent. Source: Wikimedia Commons.
"Black smokers" are hydrothermal vents that lie hundreds of metres below the ocean surface. These are areas where the seafloor is actively spreading due to movement of the earth's crust. In these areas fractures in the earth's crust release streams of geothermally heated water that are rich in dissolved metals. When these hot fluids hit the cold sea water, metals precipitate out of solution and form mounds and chimneys of mineral rich sulphides known by mining companies as Seafloor Massive Sulphides (SMS). The metal sulphides that are deposited can become massive sulphide ore deposits over time. Since the 1977, when the first one was discovered by researchers from the Scripps Oceanographic Institute, hydrothermal vents have been identified in scores of locations around the world, including in the Manus Basin off the coast of Papua New Guinea, the Kermadec Ridge in New Zealand waters, and along several other fissures around the Pacific Rim.
A sulphide deposit. Source: Nautilus Minerals.
It is the unique mix of what is in those solid undersea deposits that is driving two publicly traded mining companies:
Neptune Minerals of Sydney and
Nautilus Minerals of Vancouver to claim large tracts of seafloor over and around these black smoker sites. If all goes to plan for these companies the first mining of these deposits will occur in 2009 with a brand new ship designed specifically for this purpose. The first deep-sea mining machines — designed to extract gold, silver and copper deposits —
are currently being built for Nautilus Minerals. A £33 million ($A68.5 million) contract for two sea-floor mining tools, capable of working at depths of more than 1700 metres, was awarded last December to a Newcastle-upon-Tyne firm,
Soil Machine Dynamics. The mining machinery is the hardware behind an emerging mineral extraction industry which has taken off rapidly in the last few years. Nautilus is an Australian-dominated but Toronto Stock Exchange listed company investigating undersea mining at a number of sites around the South Pacific.
According to Nautilus CEO David Heydon in 2006 Nautilus had “17,500 km
2 of mineral claims covering what you call on land a ‘mining camp.’” He added that the project had enormous potential because the company could place claims over “the whole mineral belt.”
Latest figures suggest that at the end of 2007 Nautilus had approximately 154,000 km
2 of granted tenements and 210,000 km
2 of tenement applications pending in PNG, Tonga, Solomon Islands, Fiji and New Zealand
Neptune Minerals has lodged three prospecting applications over a total area of 84,880 km2 in New Zealands territorial waters near the undersea Monowai volcano on the Kermadec Arc and along the Colville Ridge. Neptune currently has exploration licenses covering 278,000 km2 in the territorial waters of New Zealand, Papua New Guinea, the Federated States of Micronesia and Vanuatu, and has further license pending covering 436,000 km2 in the territorial waters of New Zealand, Japan, Commonwealth of Northern Mariana Islands, Palau and Italy.
So what is undersea mining? How would it work?
According to David Heydon the set-up proposed by Nautilus for the Solwara Project in Papua New Guinea involves four main components:
- The material will be "disaggregated" from the seabed with a seabed crawler that has a cutter section and dredge head. This unit is operated from the ship via an umbilical cable.
- The cut material will then sucked in and pumped through a 300mm wide pipe. Five pumps spread along the pipe at different depths move the material 1,700 metres to the ship above.
- The material is then collected on the ship in a cargo hold and then transferred to a barge by very large excavators fixed on the ship.
- The material is then processed and refined on shore.
The proposed Nautilus mining technique. Source: Nautilus Minerals
Nautilus estimates that it will be able to mine 6000 tonnes a day from its target site and there is concern from many environmental campaigners and marine biologists that the unusual ecosystems around these sites might be destroyed by mining, as has happened so often on dry land. 'These sites have limited physical integrity and great biodiversity,' says Simon Cripps, director of the WWF's global marine programme.
What environmental effects might subsea mining have?
Nautilus have funded a large Environmental Impact Assessment Study as part of their plan to convince the Papua New Guinea Government to allow the proposed mining to go ahead, however this document is not yet available for viewing by interested environmentalists.
The mining operations will use a strip-mining approach to remove deposits within the top 20 metres of the seafloor. These strips would be located approximately 500 metres to two kilometres from the active vents, but scientist Jochen Halfar of the University of Toronto argues that the cutting and pumping process will disgorge considerable amounts of fine sediment into the water column—a serious problem for vent organisms that feed by filtering the water in their habitat.
Halfar suggests that the mining process could also raise concentrated nutrients from the deep sea to the relatively nutrient-poor surface waters of the ocean, causing algal blooms and potentially contaminating waters that support Papua New Guinea’s commercial fishing industry, as well as local subsistence fishers. Depending on ocean currents, these nutrients could drift widely, disrupting the food chain and potentially damaging ecosystems that lie within other countries’ economic zones or in international waters. This poses additional problems, because while a state has the right to exploit its own resources, international environmental law decrees that it cannot damage the environment beyond its boundaries.
Opponents also point out that mining vessels, designed to extract pure metals from their ores, will also carry thousands of tonnes of sulphurous waste that could cause potentially devastating acidification if dumped back into the sea, whether deliberately or accidentally. Craig Cary, a marine biologist at the University of Delaware in Newark, says "If I was in charge of reviewing permit requests there would be some serious questions to answer. Metal sulphides are nasty substances - how are they going to deal with that?" he says.
One clear Nautilus talking point is that undersea mining is far less environmentally damaging than terrestrial mining.
Scott Trebilcock, vice-president of business development:
Trebilcock believes the operation will cause far less environmental damage than a similar-sized onshore mine. He says: "There's no disturbance to the site around the mine. We'll have no waste rock. Everything we take up will be smelted.
Dr. Steven Scott, a geologist at the University of Toronto who does a lot of work with Nautilus:
It's a transformation that he says has evoked a knee-jerk reaction over the possible environmental impacts of this mining, which he believes could be less destructive than terrestrial mining.
Dr Samantha Smith, formerly of the University of Toronto, now of Nautilus:
The assessment is led by Smith, recently converted to the cause of underwater mining. 'Environmentally, sea floor mining is a better alternative to terrestrial mining,' she argues. 'Mining on land leaves a substantial footprint. It leaves polluted waterways, carbon emissions from heavy machinery and millions of tonnes of waste rock that has to be dumped somewhere.'
The WWF remains sceptical. 'It isn't a useful argument to say that this is less harmful than mining on land, since terrestrial mining is already extremely harmful,' says Cripps. 'Making such a comparison is a counter-productive argument. What we're interested in is seeing a thorough assessment of the real impact that this will have.' If the Solwara Environmental Impact Assessment is ever released perhaps it will go some way towards answering some of the question that independent scientists have regarding the project impacts.
