Why ocean mud might matter to your future iPhone

Odds are, if you name any electronic device, it relies on a group of metals known as the rare earths. These metals (most are found on the periodic table in the Lanthanide group) have special properties useful for a wide range of things like magnets, batteries, lasers, lamps, X-ray scanners, and catalysts. Without them, you canâ??t make wind turbines or smart phones or hybrid cars, so global demand is high and getting higher.Â*

Given that information, consider the following fact: China currently produces 97 percent of the worldâ??s supply of rare earth elements. If ever a market has been cornered, itâ??s this one.

China isnâ??t the only nation with economic sources of rare earths, though. If you put together the former USSR states, Australia, and the US, youâ??ll find about one-third of global reservesâ??roughly the same amount that China possesses. China has dominated the supply because of its cheap labor and loose environmental regulations, but other sources will soon need to come online to meet rising demand (including from within China itself). Skyrocketing prices will only help stimulate production, but more accessible deposits would also be a boon.

Enter a paper published in Nature Geoscience. A group of Japanese researchers have identified a vast new source: the seafloor. Using sediment cores from 78 locations that cover a big chunk of the Pacific Ocean, theyâ??ve found huge areas where the concentration of rare earths in the sediment is well above the level that makes mining worthwhile. In the eastern South Pacific and the central North Pacific, the concentrations are comparable to the deposits in China, except that the heavier of the rare earth elementsâ??gadolinium on upâ??are twice as abundant in the seafloor deposits.

In addition, the muds contain viable amounts of other metalsâ??namely vanadium, cobalt, nickel, copper, zinc, molybdenum, and manganese. And like a late night infomercial, it seems to get even better!Â*Thorium and uranium are much less abundant than in continental deposits, minimizing issues with radioactivity.Â*

The icing on the cake is that rare earth extractionâ??liberating the metals from the compounds that they're part ofâ??is also much easier for these deposits than for continental ones. The authors note that almost all the rare earths are easily extracted with just a few hours in dilute acid.

Thanks, hydrothermal activity!

The seafloor deposits appear to be connected with hydrothermal activity. Iron compounds that precipitate out of hydrothermal fluids are thought to scavenge the rare earth elements from the surrounding seawater, taking them out of the water column and concentrating them in sediment.

Three main factors control the distribution of high quality rare earth resources on the seafloor: proximity to hydrothermal activity (common at mid-ocean spreading centers), direction of deep-water currents, and general sedimentation rate. If youâ??ve got lots of carbonate mud or continental clay being deposited, youâ??ll dilute the rare earth concentration of the mud beyond usefulness.

The researchers calculate that a single square kilometer of seafloor sediment (the layers of interest range from 3 to 70 meters thick) in these regions could provide up to one-fifth of the current annual demand for rare earths. The authors summarize the impact of their findings by noting, â??Unless the great water depths have a significant impact on the technological and economic viability of mining on [the] seafloor, theÂ? mud in the Pacific Ocean may constitute a highly promising resource for the future.â??

Nature Geoscience, 2011. DOI: 10.1038/NGEO1185 Â*(About DOIs).

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