Teachings of Queen Kunti, Ch 23: “Human prosperity flourishes by natural gifts and not by gigantic industrial enterprises. The gigantic industrial enterprises are products of a godless civilization, and they cause the destruction of the noble aims of human life. The more we go on increasing such troublesome industries to squeeze out the vital energy of the human being, the more there will be unrest and dissatisfaction of the people in general, although a few only can live lavishly by exploitation.”

The Promise and Perils of Seafloor Mining

Can minerals be extracted from the seafloor without environmental impacts?

Minerals in deep sea

Source: Oceanus Magazine – A year ago, the Canadian mining company Nautilus Minerals was poised to launch a new industry: mining the deep ocean floor. All Nautilus had to do was finish building special equipment and arranging permits to work at a site it had leased off the shores of Papua New Guinea (PNG). Then it would commence grinding copper-rich rock on the seafloor into a slurry, vacuuming it up, and pumping it to a ship on the surface (see interactive). The company would also recover precious metals such as gold and silver, as well as zinc and other commercially traded metals.

Nautilus’ plans alarmed many scientists. The mining was targeted at hydrothermal vents, where chemical-rich fluids spewing from the seafloor spur the accumulation of not only metals, but also lush communities of exotic life. Ever since deep-sea vents were first discovered in 1977, they have yielded a treasure trove of scientific clues about how our planet’s surface formed, how the oceans’ chemistry works, even how life may have started on Earth. What if a gold rush into these unique ecosystems were to produce a subsea version of the environmental damage that mining has caused on land?

“It seemed like Nautilus was in a real fast race to get the first mine on the seafloor,” said geophysicist Maurice Tivey of Woods Hole Oceanographic Institution (WHOI). “A lot of people thought it was too early.”

But then copper prices plummeted with the global economic slowdown, and Nautilus put many of its plans on hold. “I think a lot of us on the science side were actually relieved,” Tivey said. But will the pause in the action make a difference?

In April 2009, a wide range of stakeholders from 20 countries pondered that and other issues at a conference on seabed mining convened by scientists at WHOI. Environmentalists, representatives from Nautilus and other major mining companies, international policymakers, and 98 scientists in a diverse range of fields gathered to share knowledge, seek common ground, and discuss seabed mining guidelines.

With scientists just beginning to understand the geological, chemical, and biological forces that conspire to create vents, mineral deposits, and vent life communities, the conference explored how the scientific community can best bring its knowledge to bear. How can scientists help locate and evaluate mineral-rich sites? How can they help protect the unique oases of deep-sea life at vents?

Where the minerals are
The metals lie in what are called seafloor massive sulfide deposits. They form as the result of a series of chemical reactions that start when seawater filters down through permeable ocean crust into rocks heated by magma below. The heat catalyzes reactions that leach metals from the rocks into the fluids. The hot fluids—which can reach up to 750°F (400°C) under the pressure in the deep—rise buoyantly back to the seafloor. As they emerge from the crust, they encounter cold water, which causes metal sulfides to precipitate out of the fluids and form solid deposits near and on the seafloor.

The ocean’s known sulfide deposits may be only a fraction of what’s actually there. “There’s a lot of real estate out there where no data have been collected,” said WHOI geochemist Chris German.

Scientists think most are either in or near the 40,000-mile (60,000-kilometer) long mid-ocean ridge system. There, the Earth’s tectonic plates are forming and actively spreading apart, creating volcanically active mountains that blister across the oceans’ floors in patterns roughly resembling the stitched seams on a baseball.

Minerals precipitating from fluids coming out of hydrothermal vents can create chimney-like structures jutting out of the seafloor. The fluids billow out of the growing chimneys in smoky-looking, dark or white plumes (see interactive). These were first discovered on fast-spreading ridges where volcanic activity occurs relatively frequently. But it turns out that venting can take many forms and also occurs on slow- and even ultra-slow spreading ridges.

Scientists now think that slower spreading ridges produce larger massive sulfide deposits. That’s because in these places, huge ramp-like faults penetrate deep into the crust and act as conduits. They bring a long-lasting supply of heated fluid from deep inside the Earth and deliver the minerals over tens of thousands of years to the same spot near the seafloor.

Many massive sulfide deposits mined on land may have formed in the deep sea and then were raised or thrust above the water during the formation of islands and continents. The island of Cyprus, for example, holds 30 massive sulfide deposits, which were a main source of copper for ancient Rome.

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