Lithium goldrush hits sleepy Oregon-Nevada border

Deposit in 19-million-year old caldera could dwarf sources in Bolivia, Chile and Australia

A lithium find in the McDermitt Caldera region on the border between US states of Oregon and Nevada has excited media attentions with the promise of lithium deposits exceeding those in Bolivia, which make up nearly a quarter of the world's resources.

Abandoned Mining Complex Property, Buildings and Tower - McDermitt Mine Nevada

Abandoned mining complex property, buildings and tower in McDermitt, Nevada

As the element is vital to the greening of the world economy, particularly in electric vehicles, attention has been focused on lithium, with major gas and oil companies now joining the search for deposits.

Reported in a paper in the US journal Science Advances at the end of August, the western US caldera find has now captured the attention of mainstream media, with Fox Business reporting that "it is believed that the caldera contains around 20 to 40 million metric tons of lithium – a figure that would dwarf deposits in Chile and Australia."

Bolivia is home to 21 million tonnes out of the 89 million tonnes that make up the world's known lithium resources and has become a focus for those concerned about the security of supply of the chemical necessary for relatively light-weight rechargeable batteries.

The recent paper said estimates suggested there could be between 20 to 40 million tonnes of lithium contained within sediments of the whole McDermitt caldera, with the maximum likely amount set at 120 million tonnes buried in the collapsed volcano crater.

"Even if this estimation is high due to variations in sediment thickness and/or lithium grade, the lithium inventory contained in McDermitt Caldera sediments would still be on par with, if not considerably larger than, the 10.2 million of Li inventory estimated to be contained in brines beneath the Salar de Uyuni in Bolivia previously considered the largest Li deposit on Earth," the paper said.

McDermitt Caldera sits on Oregon's southern border with Nevada. It is about 28 miles (45km) long north–south and 22 miles (35km) wide east–west at an elevation of around 6,816 feet or 2,078 meters and is likely to be the oldest of a sequence of calderas formed by the Yellowstone hotspot. Indigenous American groups including the People of Red Mountain oppose lithium exploration in the Mcdermitt Caldera, and have filed several requests for injunctions with the Bureau of Land Management.

Illite, the shale-like clay which contains the lithium, was previously assumed to be everywhere at depth in the caldera, Thomas Benson, a geologist at Lithium Americas Corporation, told Chemistry World.

Benson's team — which wrote the paper — said a layer of illite was about 40m thick and formed in the lake sediments by hot brine via a process making it particularly rich in lithium.

Belgian geologist Anouk Borst explained that the multistep process meant the researchers "seem to have hit the sweet spot where the clays are preserved close to the surface, so they won't have to extract as much rock, yet it hasn't been weathered away yet." ®

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