Lithium beneath a supervolcano: Geologic processes behind the $1.5 trilion McDermitt Caldera discovery

The confirmation of an exceptionally large lithium deposit within the McDermitt Caldera is reshaping current understanding of mineral formation in volcanic terrains. Recent studies estimate that the caldera may host 20 to 40 million metric tonnes of lithium-rich clay, making it one of the most significant documented accumulations of this critical mineral. The discovery has drawn global attention due to its potential economic value, calculated at approximately 1.5 trillion US dollars based on current lithium carbonate contract prices. The caldera offers a detailed example of how supervolcanic processes, hydrothermal alteration and basin development interact to create economically viable mineral systems.

The McDermitt Caldera formed about 16 million years ago when a major volcanic eruption caused the underlying magma chamber to collapse. The resulting depression evolved into a closed basin that accumulated ash, mud and other fine sediments. These lakebed deposits eventually hardened into claystones that now host lithium-bearing minerals. Continued volcanic activity beneath the caldera released hydrothermal fluids that migrated upward through the saturated sediments. These fluids altered magnesium-rich smectite into illite, a potassium-bearing clay capable of storing substantially higher lithium concentrations. At Thacker Pass, one of the most enriched areas, the illite layer reaches roughly 100 feet in thickness and contains between 1.3 and 2.4 percent lithium by weight. The shallow positioning of this layer suggests that open-pit extraction is feasible if environmental and regulatory conditions permit.

Clay-hosted lithium deposits present notable technical challenges because lithium is structurally bound within the mineral lattice. Extraction requires fine grinding, controlled leaching techniques and careful management of water resources and chemical reagents. Despite these complexities, the unusually high grades and favourable geometry at McDermitt significantly reduce waste-to-ore ratios. As global demand for lithium continues to rise, this deposit is expected to influence exploration strategies for similar volcanic basins. The site demonstrates how volcanic chemistry, basin morphology and long-lived geothermal activity can collectively produce high-value mineral systems. Decisions in the coming years will determine whether the deposit becomes a long-term component of the global energy supply chain, yet the geologic significance of the caldera is already well established.

Find here our article for Geotechnical Slope Design for Lithium Deposits.