In the high desert along the Nevada–Oregon border, a quiet basin formed by an ancient supervolcano is rapidly becoming a global focal point. Hidden beneath the McDermitt Caldera lies what scientists now believe is the world’s largest known deposit of lithium, the element driving the battery revolution behind electric vehicles, smartphones, and renewable energy storage.
This site, called Thacker Pass, is already reshaping how geologists think about mineral formation in volcanic terrains. Early findings estimate the deposit could hold 20 to 40 million metric tons of lithium—potentially more than double Bolivia’s Salar de Uyuni, long considered the planet’s largest source. If fully confirmed and extracted, the lithium buried here could power hundreds of millions of EVs and make the United States a key player in the clean energy economy.
But the mine sits at the heart of a collision between mineral demand and environmental and cultural preservation. The project, backed by billions in federal support and major automaker partnerships, faces growing pushback from Indigenous tribes and environmental advocates. At stake is not just a trove of critical minerals, but a national test of how far America is willing to go to secure its clean energy future.
The Caldera With a Trillion-Dollar Core
The McDermitt Caldera spans more than 1,000 square kilometers and was formed 16 million years ago by a massive volcanic eruption. Over time, volcanic ash and mud accumulated at the basin’s center, creating lakebed clays rich in lithium-bearing minerals. Recent research published in Science Advances revealed that post-eruption hydrothermal fluids transformed magnesium-rich smectite into illite, a potassium-bearing clay containing significantly higher lithium concentrations—up to 2.4% by weight in some zones at Thacker Pass.
The scale of this lithium enrichment is unmatched. Traditional lithium clay deposits average less than 1% lithium content; at Thacker Pass, the illite layer alone is about 100 feet thick, shallow enough for open-pit mining, which reduces operational complexity and cost.
Unlike lithium from brines or hard rock, clay-hosted lithium poses unique challenges. The metal is chemically bonded within mineral structures, requiring a more intensive extraction process involving leaching and chemical washing. Still, the shallow geometry and unusually high grades at Thacker Pass offer a low strip ratio, which translates to less waste rock per ton of lithium—a critical metric for mine feasibility.
The site’s formation, mineral composition, and access have positioned it as one of the most promising critical mineral deposits in North America.
Billions in Backing and a Battery Race at Stake
The U.S. Department of Energy has approved a $2.23 billion loan to fund construction at Thacker Pass, part of the Biden administration’s push to onshore clean energy supply chains. The funding was granted through the Advanced Technology Vehicles Manufacturing program and is among the largest ever awarded to a lithium project.
Project developer Lithium Americas Corp. began construction in 2023 and aims to reach 40,000 metric tons of lithium carbonate output annually in its first phase. Production will expand in stages, eventually reaching 160,000 tons per year over five phases, according to the company’s official technical report. The full operation is expected to span 85 years, making it one of the longest-lived lithium assets in the world.
To secure its battery supply, General Motors has entered into a 20-year offtake agreement for 100% of Phase 1 production and a significant share of Phase 2. GM also owns a 38% equity stake in the project.
Despite the support from Washington and Detroit, the project remains divisive. Tribal communities, including members of the Fort McDermitt Paiute and Shoshone Tribe, have expressed concern about the mine’s potential impact on ancestral lands, springs, and archaeological sites. A coalition of tribes and environmental groups has filed legal challenges, some still pending, against the Bureau of Land Management’s 2021 Record of Decision approving the mine.
Geology Reimagined: Lithium in Volcanic Basins
Thacker Pass is challenging conventional thinking about lithium geology. Until recently, global lithium production was dominated by spodumene pegmatites (hard rock in Australia) and evaporite brines (salt flats in South America). The McDermitt Caldera adds a new category to the mix: volcano-sedimentary lithium systems, formed through a blend of magma chemistry, closed-basin lake environments, and long-lived geothermal circulation.
In the case of McDermitt, peralkaline magmas rich in sodium and potassium helped retain lithium during cooling, making the surrounding ash and tuff highly fertile for clay formation. Resurgent magma movement fractured the overlying rock, creating conduits for hot fluids that concentrated lithium in illite deposits—especially in the southern portion of the caldera, where Thacker Pass now sits.
These findings suggest that similar caldera basins could hold untapped lithium potential. Geologists are now revisiting other resurgent volcanic systems in the American West and abroad, looking for the same mix of mineralogy and heat-driven alteration. The discovery marks a shift in critical mineral exploration strategies as demand for lithium accelerates.