Buried Treasure: Deep Sea Mining

10 May 2011 (Last Updated May 10th, 2011 18:30)

As earth's final frontier, the ocean floor has yet to yield its mineral secrets. The prospect of exploring deep sea deposits is sparking interest from industry and concern from environmental activists. Sarah Blackman finds out how companies are overcoming the challenges and speaks to experts to find out what the future holds for deep sea mining.

Buried Treasure: Deep Sea Mining

There are many fictional tales that popularised the myth of buried treasure, but the reality is, the deepest oceans are set to become a hotbed for precious metal mining in as little as two years' time.

Land-based ore bodies are depleting rapidly, as are ore grades, and as the demand for metals in Japan, China and India rises and populations soar, the world is looking for new and unusual sources of minerals in a bid to maintain growth.

The seabed certainly meets this requirement; after all, oceans and seas make up 71% of the earth's surface and, according to a report by Dr Steve Scott, a geologist at the University of Toronto, ocean basins harbor huge mineral resources, many of which carry enormous economic potential, which is only now being realised.

Seafloor sulphides

Underwater mining is not a new concept; companies have been attempting to recover manganese nodules, containing cobalt and nickel, from the abyss for many years. What the industry is now focusing on, however, is extracting seafloor massive sulphides (SMS) contained in 'black smokers', a type of hydrothermal vent.

"Marine mining companies are literally diving into the unknown."

Dr Scott was the first ore deposits geologist to see a black smoker in person, in 1982. These sea vents appear as chimney-like structures that emit a cloud of black material, and particles with high levels of sulfides, such as copper, zinc, lead, silver and gold.

Scott predicted that the world would someday mine for these deposits, but admits that it has been a long time coming. "There was no marine mining industry when I first worked on black smokers," he says. "It required a major proselytizing effort on my part to change the view of the conventional land mining industry."

"The industry is very conservative - for good reason - and had no experience in the deep sea so was reluctant to consider the possibility [of deep sea mining] until recently," Scott adds. In the end, it was a new breed of companies, including Nautilus Minerals, that finally began to surface and tap into the vast offshore resources available.

Nautilus Minerals vice president for investor relations Joe Dowling explains that, ultimately, the world must turn to resources available in the sea to meet the rising demand for metals. "We aim to be a leader in this process, demonstrating that this is an area that can be carefully and responsibly developed for the benefit of local and broader communities around the world."

Underwater projects

So far, SMS deposits have yet to be unearthed, but Nautilus Minerals in well underway with its preparations to mine its Solwara 1 project in the Manus Basin off the coast of Papua New Guinea.

Nautilus has ordered its subsea slurry lift pump which will lift high grade slurry from the bottom of the riser to a production support vessel, 1,600m above the Solwara deposits, discovered by Dr Scott, and Dr Ray Binns of Australia's Commonwealth Scientific and Industrial Research Organisation in 1996.

"The seafloor production tools are essentially based on machinery that is currently in use in other industries, including deep-sea trenching, the oil and gas industry and offshore diamond mining industry, and we have adapted the designs for our specific purposes," Dowling explains. "The riser and lifting system is well developed and the technology has been tried and proven."

Scientists writing in the journal Marine Policy published last year indicated that the Solwara 1 site has 0.87Mt of ore, containing 6.8% copper, 0.4% gold and 23ppm of silver. Nautilus plans to begin mining the area in 2013, and in the meantime it is surveying the seafloor in other areas of the western Pacific, where it has some 500,000km² of exploration territory.

Canadian firm Diamond Fields International and Saudi Arabian group Manafa also have a license to mine the Atlantis II muds in the Red Sea. This site contains 94 million tons of ore, including 1.8 million tons of zinc and 425,000t of copper.

Sink or swim

As a relatively new extraction process, deep sea SMS mining is expected to prove challenging, especially when it comes explaining the concept to environmental activists.

"Nautilus Minerals vice president for investor relations Joe Dowling explains that the world must turn to resources available in the sea."

The sites targeted by Nautilus Minerals, for example, contain volcanic fields which continue to erupt across many square metres of sea floor. Disturbing these already-unsettled areas can lead to plumes of debris being kicked up by production tools.

The biggest problem is biology, says Scott. "The seafloor deposits are home to groups of animals that are not well known in the view of the marine biological community.

"Nautilus is working with a number of biologists to overcome this problem, and has come up with some schemes for protecting this important ecology," Scott adds.

He believes that the challenges facing the deep sea mining industry are not insurmountable. After all, he says, "the oil industry has been working in the deep sea for many years."

There are also environmental advantages over land mining when it comes to deep sea extraction; no big holes are drilled in the ground, there is no waste rock to be disposed of, and no acid mine drainage to contend with.

Diving into the unknown

Land mining differs to the deep sea extraction process in many ways. For example, Nautilus will produce around 1.3 million tons of high grade ore from its Solwara 1 project each year, compared to the tens of million tons of low grade ore recovered on the average land mine each year.

Where on land, companies have 50 trucks or more to recover ore, only a handful of production tools will be used to mine the ocean floor, which can be a harsh environment to work in.

Marine mining companies are literally diving into the unknown, but experts are confident they will be successful in their quests, including Scott. "If they [Nautilus] prove a success, and I think they will, you will see others jump into the game including major land mining companies," he says. "I expect China and Russia to make a move into this area."