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Deep sea rich in valuable metals: cost would be high to mine Pacific rare earth elements.

Mud at the bottom of the Pacific Ocean contains surprising levels of rare earth elements, 17 chemicals with exotic names like neodymium and europium that are crucial to technologies ranging from cell phones and televisions to fluorescent lightbulbs and wind turbines.

Hot plumes from hydrothermai vents pulled these materials out of seawater and deposited them on the seafloor, bit by bit, over tens of millions of years. One square patch of metal-rich mud 2.3 kilometers wide might contain enough rare earths to meet most of the global demand for a year, Japanese geologists report online July 3 in Nature Geoscience.

"I believe that rare earth resources undersea are much more promising than on-land resources," says Yasuhiro Kato, a University of Tokyo geologist who led the study.

About 97 percent of the world's rare earth elements come from China, which has restricted exports in recent years. With prices skyrocketing, shortages are feared--especially in Japan, which lacks minable deposits of these elements.

Kato's team analyzed seafloor cores taken from 78 sites throughout the Pacific Ocean. Near Hawaii and in the southeast Pacific, concentrations of rare earths were comparable to those found in clays mined in China. Some deposits of heavy rare earths such as dysprosium, a component of magnets in hybrid car motors, contained twice as much as in the clays.

Deep-sea mining is an old idea, but one that has yet to prove itself in the face of high costs and environmental concerns. Discovered decades ago, chunks of manganese on the ocean floor and deposits of metals such as zinc and copper in the Red Sea have proven impractical to mine.


Sunken treasure Geologists measured concentrations of rare earth elements in ocean sediments at 78 Pacific sites. In some places (shown), concentrations were comparable to those in clays in China, which produces most of the world's supply. SOURCE: Y. KATO ET AL/NATURE GEOSCIENCE 2011

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Title Annotation:Earth
Author:Powell, Devin
Publication:Science News
Geographic Code:0PACI
Date:Aug 13, 2011
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