Rare earths treasure trove found in seabed near Minami-Torishima

March 22, 2013

By HARUFUMI MORI/ Staff Writer

Scientists said March 21 that they have identified rich seabed deposits of rare earth elements in a Japanese exclusive economic zone near Minami-Torishima, a coral reef 2,000 kilometers southeast of Tokyo.

The team of researchers from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the University of Tokyo said they used the Kairei, a JAMSTEC deep-sea research vessel, to sample soil and mud down to depths of more than 10 meters beneath the seabed at seven locations near Minami-Torishima in January. They have so far studied two of the drilling core samples. The seabed around Minami-Torishima is 5,600-5,800 meters below the surface of the ocean.

In one of the two samples, the concentration of rare earth elements in the mud peaked at 6,600 ppm, or 0.66 percent, at a depth of 3 meters beneath the seafloor.

The concentrations turned out to be so high that daily mining of 10,000 tons of seabed mud in the area could cover more than 40 percent of total domestic demand in Japan, said Yasuhiro Kato, a professor of Earth resources studies at the University of Tokyo.

Rare earth elements are a generic term for 17 elements that constitute part of rare metals. Neodymium, one of them, is a raw material for high-performance magnets that are used in motors in smartphones and computer disk drives and other products. Yttrium, another rare earth element, is used to make fluorescent substances in light-emitting diodes and other products.

Although rare earth elements are indispensable in the manufacturing of parts for electric vehicles and other high-tech products, their prices have fluctuated violently in recent years due to export regulations by China, which has a 90 percent share in their global output.

The latest find has rare earth element concentrations more than 10 times the corresponding figures in deposits being mined in China--between 300 and 500 ppm. The deposits were also found to lie in abundance at relatively shallow depths of only several meters beneath the seabed.

Scientists previously believed that more than 10-meter-thick deposits of mud covered the layers of rare earth elements, obstructing mining.

But the depth beneath the water surface is still expected to present considerable challenges.

The Chikyu, a JAMSTEC deep-sea drilling vessel, has recovered seabed mud from a depth of 2,500 meters for research purposes. A seabed oil field has been developed overseas at a depth of 3,000 meters.

But the development of seabed resources at depths of more than 5,000 meters has no precedent, either at home or abroad. There remains a mountain of technological challenges, including how to withstand water pressure and ocean currents and how to process the mining products in the ocean, sources said.

The costs of mining are also expected to influence the development potential.

Although the annual domestic demand in Japan for rare earth elements used to stand around 20,000-30,000 tons, that demand likely plunged considerably last year due partly to inventory adjustments, the development of replacement substances and recycling efforts. Market prices have fallen to about 20 percent of the 2011 peak figures for some elements, the sources said.

By HARUFUMI MORI/ Staff Writer
  • 1
submit to reddit
A seabed mud sample taken from a depth of more than 5,000 meters near Minami-Torishima island is rich in rare earth elements. The photo was taken on March 21 at the science ministry in Tokyo. (Harufumi Mori)

A seabed mud sample taken from a depth of more than 5,000 meters near Minami-Torishima island is rich in rare earth elements. The photo was taken on March 21 at the science ministry in Tokyo. (Harufumi Mori)

Toggle
  • A seabed mud sample taken from a depth of more than 5,000 meters near Minami-Torishima island is rich in rare earth elements. The photo was taken on March 21 at the science ministry in Tokyo. (Harufumi Mori)
  • Minami-Torishima island in December 2003 (Asahi Shimbun file photo)
  • The Asahi Shimbun

More AJW