A broad stretch of high desert in northern Nevada and southern Oregon has drawn renewed attention from geologists. Beneath the McDermitt caldera, an ancient supervolcano formed about 16.4 million years ago, researchers have identified extensive lithium mineralisation in clay rich sediments. Recent studies suggest the resource could rank among the largest lithium clay deposits in the world. At Thacker Pass alone, measured and inferred resources are estimated at 533 million tonnes of ore grading about 0.29 per cent lithium, equivalent to more than 1.5 million tonnes of contained lithium. Broader assessments indicate the wider caldera may hold far more, placing the in situ value in the trillion dollar range under current market assumptions.
Geological surveys reveal extensive lithium reserves beneath western US caldera
The lithium is hosted in tuffaceous sediments that filled the caldera after its collapse. These sediments, largely derived from volcanic glass, accumulated in a closed basin environment. Over time they underwent chemical alteration through a process known as closed hydrologic system diagenesis.In the southern and western parts of the basin, entire sedimentary sections contain more than 1500 parts per million lithium. The most lithium rich zone, found in lower sedimentary layers, averages around 3000 ppm and is dominated by claystone. Researchers have identified lithium mainly within illitic clay minerals, chemically similar to tainiolite. Higher in the sequence, lithium occurs in smectite clays at slightly lower grades.
Geological timing points beyond simple hydrothermal origin
According to a study published on MDPI, dating of authigenic potassium feldspar from mineralised layers yielded an age of about 14.9 million years. This is roughly 1.2 million years younger than the end of major magmatic activity in the caldera. That gap complicates a purely hydrothermal explanation tied directly to eruptive heat.Instead, evidence suggests lithium enrichment occurred during early basin sedimentation. Volcanic glass likely released lithium as it altered in alkaline groundwater within the closed basin. Some researchers argue that additional lithium may have entered the system from residual magma or volatile rich fluids during the waning stages of volcanism. The exact balance remains debated.
Resource estimates extend across much of the caldera
The Thacker Pass deposit represents less than one per cent of the surface area of tuffaceous sediments within the caldera. Exploration drilling by multiple companies has identified lithium mineralisation across roughly three quarters of the basin. A government mineral resource assessment assigned similar potential throughout much of the remaining sedimentary sequence.If comparable grades extend widely, the overall resource could exceed earlier global rankings. Current published figures already place McDermitt among the world’s largest in situ lithium resources. Analysts have attached valuations reaching 1.5 trillion dollars, though actual economic recovery would depend on extraction costs, processing technology and market demand.
Strategic importance grows with battery demand
Lithium remains a key component in lithium ion batteries used in electric vehicles and energy storage systems. Most global production comes from brines and hard rock pegmatites. Clay hosted deposits such as McDermitt represent a smaller share of known supply but may become more important as demand expands.Development work at Thacker Pass is progressing toward potential mining. Environmental review and regulatory processes continue. The scale of the deposit is clear. Its full economic and geological story is still being worked through, layer by layer. Go to Source
