There were a number of reports over the weekend, about a group of Japanese researchers who say that they have found significant quantities of rare-earth elements (REEs) at multiple sites on the seabed of the Pacific Ocean. In a paper published in Nature Geoscience  on July 3, 2011, lead author Yasushiro Kato and his colleagues shared the extensive work that was undertaken, to obtain and to analyze 2,037 samples from 78 different sites across the Pacific Ocean.
Reuters , the BBC , Nikkei  and others reported that there is an estimated 100 billion tonnes of rare earths in these deposits. Which is rather interesting, because the scientists themselves made no such claim in their paper…
What they do report, are two regions of the sea bed with so-called REE-rich muds:
- one in the eastern South Pacific containing 0.1-0.22% total REEs (including 0.02-0.04% heavy REEs), in layers 10 to 40 meters thick;
- one in the central North Pacific, containing 0.04-0.1% total REEs (including 0.007-0.02% heavy REEs), in layers 30 to greater than 70 meters thick.
The authors compare these muds to the ion-absorption-type clays found in China, which are presently the world’s primary source of heavy REEs. They comment that the mud in the eastern South Pacific has heavy REE content that is “nearly twice as abundant as in the Chinese deposits“. Of course, those Chinese deposits are not sitting under “great water depths (mostly 4,000-5,000 meters)” and below the surface of the sea floor. It is because they are readily accessible and processable, that the Chinese ion-absorption deposits are exploited, despite their very low concentrations of REEs (heavy or otherwise).
Doing a couple of rough calculations, the authors estimate that a 10 meter-thick bed of mud in the eastern South Pacific, with an area of 1 square kilometer, could yield approximately 9,000 tonnes of rare earths. They also estimate that a 70 meter-thick bed of mud in the central North Pacific, with an area of 1 square kilometer, could yield approximately 25,000 tonnes of rare earths. These numbers are not too shabby (if we again forget about the 2.5-3 miles of water sat above them, and their remote location from any significant land masses). As I’ve said elsewhere , I can’t see these deposits ever being commercially exploited, but the empirical work done by the Japanese researchers which is presented in this paper, is impressive.
What the authors do NOT estimate, is a size of the total mineral resource, and wisely so. While they mention that the thick distributions of mud at numerous sites might mean that the REEs on the sea floor “could exceed the world’s current land reserves of [110 million tonnes]“, they acknowledge the considerable challenges and significant variability present on the seafloor, and thus state that “resource estimates for large regions cannot be made until more detailed data are available for areas lacking cores.”
Perhaps the lead author later just threw out a wild-ass, ridiculous guess at the size of the deposits, in response to a reporter’s question. But if he did not, and if the scientists themselves are not making the claim that there are “an estimated 100 billion tonnes of rare-earth deposits”, as reported by Reuters , Nikkei , and the BBC  – just who IS making this claim? Who has inserted these comments into this story, and fed them to the mainstream media, and why might they have done that? Can we find clues in the current pricing turmoil, worries about supply from China, and the increasing politicization of the rare-earths story?
I leave those questions as an exercise for the reader to ponder….