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JAPANESE scientists claim to have discovered substantial rare-earth deposits in the Pacific Ocean, in quantities that far outstrip current global reserves.

The team has said that it couldn’t estimate when attempts to extract the minerals may start, but claimed that the seabed may hold 80b-100b t of the valuable elements. If so, the reserves of rare-earths buried in the seabed would be almost 1,000 times greater than those on dry land.

“We estimate that an area of just 1 km², surrounding one of the sampling sites, could provide one-fifth of the current annual world consumption of these elements,” said Yasuhiro Kato, the team leader and associate professor of earth sciences at the University of Tokyo, in the recently published report.

The significance of their find has the potential to be huge. China currently produces 97% of the world’s rare earths, operating a virtual monopoly of the valuable metals, and over recent years has been moving to further strengthen its control. Japan is particularly anxious to find other sources, after its hi-tech manufacturing sector spent months battling for supplies of essential components in the wake a diplomatic row with its neighbour last year.

“World demand for rare-earth elements and the metal yttrium—which are crucial for novel electronic equipment and green-energy technologies—is increasing rapidly,” said Kato.

“Several types of seafloor sediment harbour high concentrations of these elements,” he continued. “However, seafloor sediments have not been regarded as a rare-earth element and yttrium resource, because data on the distribution of these deposits [was] insufficient.”

The team studied drill core samples from dozens of sites dotted throughout the Pacific Ocean. Over the course of its research the scientists found more evidence of rare-earths than anyone could have predicted, uncovering a “highly promising huge resource” of the elusive elements.

It is thought that the deposits originated in hydrothermal vents deep below the surface, before interacting with seawater and other minerals. The scientists believe that these then fall to the seabed, helping to form layers of rare-earth-rich mud that can be up to 70 m thick. One site in particular is estimated to hold 25,000 t of the minerals within only 1 km².

For all their potential, though, it is worth remembering that the deposits were mostly found at depths of between 4,000 m and 5,000 m. The mud is expected to be significantly easier to extract than most land-based minerals, but the extra costs involved with deepwater mining may keep any plans shelved for years to come. Nautilus Minerals, which plans to develop a copper and gold mining project in the Bismarck Sea of Papua New Guinea, plans on working at a depth of around 1,600 m.

Karo and his team, however, remain optimistic about their discovery.

“Unless the great water depths have a significant impact on the technological and economic viability of mining rare-earths on the seafloor,” they said, “the rare-earth-rich mud in the Pacific Ocean may constitute a highly promising… resource for the future.”

Nature Geoscience doi: 10.1038/ngeo1185