We're on the brink of the era of deep ocean mining, says a global pioneer in the study of sea floor mineral deposits. Dr. Steven Scott, a geologist at the University of Toronto, in Toronto, Canada says that advances in marine geology and deep ocean technology have combined to make it realistic to go more than two kilometres underwater for gold and other mineral treasures.
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.
Presently, the world's first two neophyte marine mining companies, Nautilus Minerals and Neptune Minerals are actively exploring the possibility of mining deep sea floor deposits. Neptune is assessing deposits it holds the rights to in territorial waters off the north coast of New Zealand's North Island. Nautilus and its joint venture partner Placer Dome, a Canadian gold mining company, are collecting samples from a deposit to which Nautilus holds the rights in the Bismarck Sea off the eastern coast of Papua New Guinea.
The big question for these companies is the economic potential of undersea deposits of polymetallic sulphides. These sulphur-rich sea floor ore bodies are produced worldwide in underwater volcanic regions by "black smokers." The black smokers are formed when seawater seeps into the porous sea bottom, is heated and re-emerges through vents carrying dissolved minerals. When the hot water hits the cold sea floor water, the minerals precipitate, creating chimney-like towers called black smokers. Over time, these towers collapse and accumulate to form ore deposits, some of which are rich in gold, silver, copper, lead and zinc.
Dr. Scott was the first mining geologist to explore black smokers. In 1982 he joined members of the Scripps Institute of Oceanography and the Woods Hole Oceanographic Institution in the submersible Alvin to explore newly discovered black smokers 2,000 metres below the waves in the Gulf of California off the coast of Mexico. He says that after more than two decades of promoting the possibility of mining the deposits created by black smokers, the launch of the present ventures is a move that's required mining companies to cross a watery psychological barrier.
"Twenty years ago, most mining companies didn't want to hear about this possibility. They thought it was too difficult. But now some are seeing that it's a lot easier to go down through a couple of thousand metres of water than through a couple of thousand metres of rock," says Dr. Scott, who is the Director of the Scotiabank Marine Geology Research Laboratory and the Norman B. Keevil Professor of Ore Genesis at the University of Toronto.
Presently the deepest undersea mines – diamond mines off the coast of southern Africa – are under just a few hundred metres of water. But Dr. Scott points to the offshore oil and gas industry as an example of the possibility for change. The international oil and gas industry went offshore starting in the mid-1940s. Today, about a third of the world's oil comes from under the sea. There are producing wells in 1,500 metres of water off the coast of Brazil, and there's drilling at 2,500 metres depth in the Gulf of Mexico.
The key challenge for new marine mining companies will be developing the technology to extract the ore from the watery depths, says Dr. Scott. He envisions the use of "deep sea versions of robotic coal mining machines" with the ore piped up to mining ships, or semi-submersible platforms as used by the offshore oil industry. He notes that deep sea robotics is a mature industry, driven in large part by the needs of offshore oil exploration and recovery.
Deep sea mining technology was given a major kick-start, notes Dr. Scott, by the approximately $650 million spent internationally in an aborted effort to develop sea floor manganese nodule mining technology in the 1970s and '80s. Manganese nodules, often rich in nickel and copper, are formed by the slow precipitation of the minerals from seawater. The nodules cover vast areas of the deep ocean floor known as the abyssal plains.
Dr. Scott was initially drawn to black smokers as a way of understanding the formation of strikingly similar terrestrial polymetallic sulphide deposits, such as those mined at the Kidd Creek copper and zinc mine in northern Ontario, Canada, and in many other countries in the world, including the United States.
"We wanted to know whether marine geology held clues for the occurrence of these terrestrial deposits. And it does," says Dr. Scott.
Now they've become "living laboratories" for understanding the formation of terrestrial and marine polymetallic sulphide deposits. One of Dr. Scott's postdoctoral students just returned from a vessel drilling the Nautilus claims off the Papua New Guinea coast. She is exploring the role that bacteria play in creating these mineral deposits.
"Getting samples from the interior of these deposits is rare," says Dr. Scott. "What we're interested in from the perspective of pure science is what microorganisms are in these deposits and what they're doing. Are they in fact causing mineralization?"
February 24, 2006
Marine Technology Reporter