Last-minute notification: Thacker Pass Lithium Deposit Zoom Presentation at 12:30 CST on Wednesday March 22
Jack Gibbons
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Kansas Geological Society
“The origin of the Thacker Pass lithium deposit, the largest known lithium resource in the United States”
Dr. Thomas R. Benson
Vice President, Global Exploration
Lithium Americas Corporation
Topic: Kansas Geological Society's Zoom Meeting Dr. Thomas Benson, VP Lithium Americus " The Origin of the Thacker Pass Lithium Deposit, the Largest in the US"
Time: Mar 22, 2023 12:30 PM Central Time (US and Canada)
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Meeting ID: 848 1181 5958
Passcode: 972042
Abstract. As the electrification of the automobile industry intensifies, demand for lithium (Li) for use in Li-ion batteries is projected to surpass expected supply by mid-decade. This is resulting in a “lithium rush” for new Li resources, including those hosted in sedimentary rocks. Most published sedimentary resources contain whole-rock Li concentrations considerably less than 2,000 ppm Li. The one notable exception is the Thacker Pass deposit in the mid-Miocene McDermitt Caldera in northern Nevada. This resource, hosted in clay-rich caldera lake sediments, has an average resource grade of ~3,000 ppm Li, with whole-rock concentrations up to 9,000 ppm Li. These sediments are present throughout much of the ~40x30 km caldera, leading Castor and Henry (2020) to estimate a total Li mass of up to ~120 Mt Li (640 Mt LCE) within the McDermitt Caldera. New data from collaboration with over 20 researchers from universities and feder labs indicate that the bulk of the Li-bearing clays likely precipitated as neoformed Mg-rich, Al-poor (Stillings et al., 2018) trioctahedral smectites within a high-pH, highly alkaline closed caldera lake system. The Mg smectites in the paleo McDermitt Lake were especially high in Li due to prolonged degassing of the underlying Li-rich intracldera tuff, which provided sustained high temperatures and added fluids rich in F, Cl, and additional Li to the system (Ingraffia et al., 2020). In the southern portion of the caldera near Thacker Pass, a hydrothermal event associated with magmatic resurgence introduced a high-temperature, low-pH, and Li-rich fluid into the system and altered a thick portion of the smectites to a Li-rich illite similar to tainiolite (Morissette, 2012). This illitic zone is extremely enriched in Li, with whole-rock concentrations consistently over 4,000 ppm Li and up to 9,000 ppm Li. To date, the illite and its associated high grades have only been documented in the vicinity of Thacker Pass along post-caldera fractures near the center of magmatic resurgence. We hypothesize that the McDermitt Caldera lake sediments at Thacker Pass have a distinctively higher grade than other clay-type resources because of this post-caldera resurgent event. Ongoing research with external collaborators aims to expand and improve upon this model using advanced mineral structure characterization techniques, Li and stable isotopic analyses, K-Ar, 40Ar/39Ar, and U-Pb geochronology, trace element geochemistry, hydrogeochemistry, and 3D geological mapping.
Bio: Tom Benson is the Vice President of Global Exploration at Lithium Americas Corporation. He received his Ph.D. in volcanology from Stanford University in 2017 for his research on global lithium resources associated with large caldera-forming eruptions. His research has gained international acclaim, appearing in Nature, The Smithsonian, NPR, and Wired, among other media outlets. Before this, Dr. Benson researched geothermal systems as an undergraduate at Harvard University, Research Associate at the Massachusetts Institute of Technology, and Fulbright Scholar in Iceland. Before joining Lithium Americas Corporation full-time in 2018, Dr. Benson worked as Adjunct Assistant Professor at New York University, Research Associate at the American Museum of Natural History, Visiting Scholar at Columbia University, and Consulting Geologist for Lithium Americas Corporation. As Vice President of Global Exploration Lithium Americas, Dr. Benson leads exploration efforts across the world and helps guide exploration programs at the Cauchari-Olaroz, Pastos Grandes, and Thacker Pass projects. He also is actively engaged in peer-reviewed research on the origins of sedimentary, brine, and pegmatite lithium deposits