Finding Minerals Beneath the Deep Blue Sea
Nicole Branan

Y. Fouquet of IFREMER

This cross section of a seafloor “polymetallic sulfide deposit” — a deposit of metal sulfides that forms when naturally occurring sulfate in seawater mixes with metals in hydrothermal vents at the seafloor — illustrates why developers are hoping to mine the seafloor: Precious metals such as copper and silver can be collected from these vents.

The deep sea is a treasure trove of valuable metals. Rocky chimneys perched atop hydrothermal vents dotting mid-ocean ridges are plump with minerals containing copper, silver and other precious and base metals. Mining companies have long seen economic potential in these enormous metal sulfide deposits, but high costs and technical challenges have thus far thwarted commercial exploitation. Now, thanks to near-record-high mineral prices and some new technologies, several entrepreneurs are gearing up to turn the mineral riches of the deep sea into monetary profits.

Over the past three decades, deep-sea expeditions have turned up rich ore deposits near hydrothermal vents in different spots around the world. These formations contain minerals from deep in Earth’s crust. Such minerals form when cold seawater seeps kilometers downward through cracks in the ocean floor, dissolving metals in hot rocks and magma. These metals react with sulfates in seawater and precipitate as sulfide deposits once they are catapulted back up into the ocean.

Vancouver-based Nautilus Minerals is currently undertaking the world’s largest commercial exploration program for high-grade seafloor massive sulfide systems. The company holds exploration licenses and applications covering more than 300,000 square kilometers in the territorial waters of Papua New Guinea, Fiji, Tonga, the Solomon Islands and New Zealand. U.K.-based Neptune Minerals also holds exploration licenses totaling more than 263,000 square kilometers in the same region. Both companies plan to be in production by the end of the decade.

“We are starting a whole new industry just like the oil and gas industry did 50 years ago when they moved offshore,” says David Heydon, president and CEO of Nautilus Minerals. Massive seafloor mineral deposits — formed through gradual precipitation of dissolved metals over tens of thousands of years — sit at depths of more than a kilometer beneath the sea surface. Nautilus plans to send remotely operated vehicles with cutting blades into the abyss to grind the deposits into golf-ball-sized chunks before pumping them up to the surface. “Unlike mineral deposits on land, the stuff on the seafloor is as soft as coal, so we won’t need drilling and blasting,” Heydon says. The cold water from the seafloor will be filtered and pumped back down 500 meters below the sea surface, and the recovered rocks will be treated on land in conventional processing plants.

The main driving forces behind the new push toward deep-sea mining are skyrocketing metal prices and soaring demand for raw materials, driven largely by the economic growth of China, India and Indonesia, says Steven Scott, a geologist at the University of Toronto in Canada and a member of Nautilus’ board of advisors. “These countries make up a large percentage of the world’s population, and they all need copper, lead, silver and other valuable metals to bring their standards of living up to those of the developed world,” Scott says. And the strong demand from developing economies will likely continue for a long time, he adds.

The prospect of opening the pristine deep seafloor to commercial mining operations has prompted mixed reactions among the scientific community. Some are concerned about possible harmful impacts on the marine environment while others think that deep-sea mining may be less deleterious than mining on land. “There may actually be some environmental advantages of marine mining,” Scott says. For example, one of the negative environmental consequences of land mining is the generation of acid mine waters produced by exposing iron sulfides to the atmosphere, he says. “But these can’t be produced in the ocean because seawater is alkaline.”

Nautilus Minerals Inc.

Nautilus Minerals is using remotely operated vehicles to collect mineral samples from the seafloor in a new deep-sea mining effort. Here, the manipulator hand of the remotely operated vehicle places a seafloor sample in a bin to be brought up and analyzed.

Hydrothermal vents — where developers are looking to extract these metals — are home to unique and diverse ecosystems, which some researchers worry could be harmed during production. Even though the submarine hot springs sport one of the least hospitable environments on the planet, the springs are teeming with life. Amid the scalding water that gushes out of the seafloor fountains live bizarre creatures such as giant tubeworms several meters long and clams the size of Frisbees. These ecosystems are not only of scientific interest, but are being explored for pharmaceutical and biotechnological applications, wrote Jochen Halfar of the University of Toronto in Canada and Rodney Fujita of the Environmental Defense in Oakland, Calif., in Science May 18. Mining activities at these vents or in areas close to them could perturb these ecosystems, potentially causing a radical change in habitat conditions, Fujita says. The deep ocean is still largely unexplored, which means that we still don’t know much about life at these depths, he adds. “For example, we don’t even know yet how many species are down there, or how sensitive these vent systems are to perturbation, or how well they would adapt to any kind of human activity.”

Heydon says Nautilus is putting a lot of effort into assuring that its mining operations are conducted in a way “that causes the least disturbances and doesn’t have any long-term impact on any species.” The company has sponsored several research cruises to areas from New Zealand to Japan on which it has invited scientists and experts from around the world, Heydon adds.

Currently, Nautilus’ main focus is the Solwara 1 prospect in the Manus Basin of Papua New Guinea. The company has been conducting environmental impact studies at the prospect for about a year, says Samantha Smith, environment manager at Nautilus. Mining activities in international waters are governed by the International Seabed Authority (an organization designed solely to organize and control mineral extraction from international waters), but territorial waters fall under the legal jurisdiction of the respective nation. That means that Nautilus has to satisfy the government of Papua New Guinea to obtain mining licenses for Solwara 1. “We are going to submit the environmental impact studies to the Papua New Guinea government, who will refer them to a PNG-based environmental council as well as a scientific advisory board made up of independent world experts,” Smith says. The studies will also be open for public review, she adds.

Heydon acknowledges that Nautilus’ deep-sea mining will have some sort of environmental impact, but he is convinced that it is a better alternative than current land mining operations. “Clearly we have extracted the easiest metal from the planet. We now have to dig deeper and deeper into the land, sometimes 3,000 meters through solid rock. That creates giant holes and a lot of waste material,” he says. Seafloor deposits, on the other hand, sit right on the surface. And while current terrestrial mines often contain less than 1 percent of copper, seafloor deposits can contain 10 percent or more, he says. “At a three to one stripping ratio, that means that about 2 million tons from a 10 percent seafloor mine would produce the same amount of copper as a 1 percent open cut land mine would produce from about 80 million tons of ore and waste.”

Starting a new industry is not only an opportunity but also a big responsibility, Heydon acknowledges. “And we will make sure that the first mine is done as best as possible because we know that the world will be watching us.”

Branan is a freelance writer living in Colorado.

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