World's largest lithium deposit

 World's largest lithium deposit confirmed under a US super volcano, valued at $1.5 trillion

A long-dormant super volcano on the Nevada-Oregon border is now at the centre of a trillion-dollar energy battle. Beneath its surface lies a lithium discovery so massive it could redraw the global battery map. Buried beneath an ancient volcanic crater on the Nevada Oregon border sits an enormous deposit of lithium rich clay. Scientists now think this quiet landscape may hold enough lithium to influence the global battery market for decades. A new study argues that McDermitt caldera may host about 20 to 40 million metric tons of lithium, likely the largest deposit yet identified. Using the recent US average contract price for lithium carbonate, about 37,000 dollars / ton, this estimate comes out to be nearly $1.5 trillion.

In the high desert along the Nevada–Oregon border, a quiet basin formed by an ancient super volcano 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. The deposit sits inside a caldera, a large volcanic crater formed when a magma chamber collapses. This particular basin spans roughly 28 miles north to south and 22 miles east to west along the Nevada Oregon line. Work on this deposit was led by Thomas R. Benson, PhD, at Lithium Americas Corporation (LAC). His research focuses on how lithium rich minerals form in volcanic terrains. 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 US a key player in the clean energy economy.

About 16 million years ago, a huge eruption emptied much of the magma chamber beneath this area. The outburst left behind thick sheets of hot ash which later cooled into hard volcanic rock on the caldera floor. Later, the crater held a long lived lake which collected volcanic ash and mud. Those sediments formed lacustrine, formed in a lake environment, claystones that now trap much of the lithium rich clay. 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. Lithium today is best known as the heart of the lithium ion battery, a rechargeable battery which moves lithium ions between two electrodes. These batteries power phones, laptops, electric cars and storage packs which balance wind and solar energy on the grid. The same research group notes that global demand for lithium could reach one million tons per year by 2040, eight times the 2022 output. That is why such a concentrated deposit in a single basin draws so much attention from governments and companies planning long term energy transitions. Volcanic lake deposits like this are shallow and wide, which lowers the strip ratio, amount of waste rock per ton of ore. Compared with deeper hard rock mines, which often means less blasted rock and lower energy use per ton of lithium. Because the richest clays sit near the land surface at Thacker Pass, miners can target the most lithium dense layers directly. The combination of huge tonnage, high grades and relatively simple geometry makes this deposit unusual among known clay hosted lithium resources.

The McDermitt Caldera spans more than 1,000 square km's and was formed 16 million years ago. Over time, volcanic ash and mud accumulated at the basin’s centre, creating lakebed clays rich in lithium-bearing minerals. Recent research 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. Deep below the basin, magma continued to release hydrothermal, hot water rich in dissolved minerals circulating underground, fluids long after the main eruption. Those fluids leached lithium and other elements from volcanic glass and carried them upward into the wet lake sediments. As that chemistry played out, the lake mud first turned into smectite, magnesium rich clay which can absorb lithium into its layers. Later, hotter fluids altered parts of that smectite into another clay called illite which locks in much more lithium. Analyses show that this clay can contain around 1.3 to 2.4 % lithium by weight, roughly double typical claystone deposits. A recent feature noted that the high grade illite layer sits close to the surface, which makes large pit mining possible. Investigators had reported lithium concentrations reaching about 1 % by weight, according to Thomas R. Benson, a geologist at Lithium Americas Corporation.

The US 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/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. Such a giant deposit also raises difficult questions about water, wildlife and the cultural meaning of this landscape. Local tribes and ranching communities have voiced concerns about how a large mine might change springs, grazing areas and sacred sites. Supporters point out that a shallow clay deposit can disturb less land than multiple smaller mines spread across distant regions. Critics respond that even a single large pit can alter groundwater, produce dust and fragment habitat if not carefully managed. 

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. Processing clay-hosted lithium is technically tricky because the metal is bound inside minerals rather than sitting in salty brines. Engineers must grind the clay, use leaching, chemical washing with carefully chosen solutions, and then recover lithium while limiting water use and waste. Geologists studying McDermitt now see a recipe for rich volcanic lithium deposits which blends magma chemistry, basin shape and long lasting heat. The magmas here were peralkaline, igneous composition unusually rich in sodium and potassium, which tend to hold on to lithium as they cool. Later, magma rose again beneath the caldera in a phase called resurgence, renewed uplift driven by fresh magma pushing upward. The movement fractured the overlying rocks, opened pathways for hot fluids, and focused lithium rich illite formation along the southern rim of the basin. Armed with this model, exploration teams scan volcanic basins for matching chemistry, preserved lake beds, and signs of past hot fluid circulation. Only a few places worldwide seem to share McDermitt’s mix of large size, closed basin setting and long lived magmatic activity.

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. 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. The McDermitt caldera lithium deposit is vast, shallow, and chemically unusual, qualities that set it apart from most other known sources. Decisions made over the next few years will determine whether this lithium mostly stays locked in clay or moves into batteries and power grids. Either way, McDermitt has already changed how scientists think about where critical minerals can hide inside old volcanic systems. For those thinking about climate and technology, this makes the link between distant geologic events and the batteries in their daily lives clear. Learning how minerals form in Earth’s crust becomes directly connected to questions about cars, phones and power grids.

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 which concentrated lithium in illite deposits, especially in the southern portion of the caldera. 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 around the world.