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Oceans hold treasure trove of minerals

CORNELL (US) —While land-based deposits may be a dwindling source of valuable minerals, deposits on the ocean floor could power humanity for centuries.

The minerals, including sulfur, copper, zinc, iron, and precious metals, are contained in volcanogenic massive sulfide (VMS) deposits that form on the ocean floor where tectonic plates pull apart and allow magma (molten rock) to invade the Earth’s 3.7-mile- (6 kilometer-) thick crust.

The magma heats seawater to 662 degrees Fahrenheit (350 degrees Celsius) and moves it through the ocean crust via convection; and the seawater deposits the minerals where it discharges along the ridge axis.

According to model simulations combined with heat flow measurements from the 1980s around the Galapagos Islands, seawater convection cools the entire crust “like a homeowner who lights a fire in his fireplace for the express purpose of cooling his house,” says Lawrence Cathles, professor of earth and atmospheric sciences at Cornell University.

That knowledge, along with the known thickness of the ocean crust, allows researchers to calculate the quantity of dissolved minerals that could be transported over each square meter of ocean floor.

The research is published online in the journal Mineralium Desposita.

If just 3 percent of the dissolved minerals precipitate—an estimate based on earlier studies—the ocean floor would hold reserves vastly greater than those on land, Cathles says.

In the case of copper—a key component in construction, power generation and transmission, industrial machinery, transportation, electronics, plumbing, heating and cooling systems, telecommunications and more—calculations show that just half of the total accumulated amount could be enough to bring the world’s growing population up to a modern standard of living and maintain it for centuries.

“I think there’s a good chance that it’s a lot more than 3 percent,” Cathles says, “but even just taking 3 percent, if you calculate how long the copper on the ocean floor would last, just half of it could last humanity 50 centuries or more.

“You go back to Christ, and then you go twice as far again, and you’ve got that much copper,” he says. “That’s everyone living at a European standard of living, essentially forever.”

Equally large quantities of uranium, lithium, phosphate, potash, and other minerals are dissolved in ocean water and could be extracted, he adds.

With the necessary precautions, extracting the underwater deposits may also be a more environmentally friendly process than mining on land. And it could provide other benefits, both scientific and psychological.

Undersea exploration around ocean ridges could open doors to new research on the fundamental processes behind the formation of Earth’s crust, Cathles notes.

“We are not resource limited on planet Earth. For a human on Earth to complain about resources is like a trillionaire’s child complaining about his allowance or inheritance. It just doesn’t have much credibility in my view.

“I think there’s real risk if we don’t really carefully, and in a credible way, articulate that there are enough resources for everybody,” he adds. “We don’t have to fight over these things.”

More news from Cornell University: www.news.cornell.edu

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