United States

Thacker Pass Project

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Overview

Mine TypeOpen Pit
StageConstruction
Commodities
  • Lithium
Mining Method
  • Truck & Shovel / Loader
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ShapshotThacker Pass is a top-tier, generational asset and hosts the largest known Measured and Indicated (M&I) lithium resource in the U.S. with significant exploration potential due to its unique geology.

Thacker Pass will be critical to the U.S. supply chain as the best and fastest option to achieve meaningful domestic production of lithium at a large-scale.

Construction commenced in March 2023 after notice to proceed from the Bureau of Land Management.

Construction budget of $145 million (cash spend) in second half of 2023, of which $51.1 million was spent in Q3 2023 primarily on advancing engineering, earthworks and the workforce hub.

Owners

SourceSource
CompanyInterestOwnership
Lithium Americas Corp. 100 % Indirect
Lithium Nevada Corp. (LNC), a wholly owned subsidiary of Lithium Americas Corp. (LAC), is advancing the Thacker Pass Project. The Project is 100% owned by LNC.

Contractors

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Deposit type

  • Sedimentary

Summary:

The Thacker Pass Project is located within an extinct 40x30 km supervolcano named McDermitt Caldera, which was formed approximately 16.3 million years ago (Ma) as part of a hotspot currently underneath the Yellowstone Plateau. Following an initial eruption and concurrent collapse of the McDermitt Caldera, a large lake formed in the caldera basin. This lake water was extremely enriched in lithium and resulted in the accumulation of lithium-rich clays. Late volcanic activity uplifted the caldera, draining the lake and bringing the lithium-rich moat sediments to the surface resulting in the near-surface lithium deposit which is the subject of the Project.

Lithium enrichment (>1,000 ppm Li) in the Thacker Pass Deposit and deposits of the Montana Mountains occur throughout the caldera lake sedimentary sequence above the intra-caldera Tuff of Long Ridge. The deeper illite-rich portion of the sedimentary sequence contains higher lithium than the shallower, smectite-rich portion. The uplift of the Montana Mountains during both caldera resurgence and Basin and Range faulting led to increased rates of weathering and erosion of a large volume of caldera lake sediments. As a result, much of the sediments in the Montana Mountains have eroded away.

South of the Montana Mountains in the Thacker Pass Deposit, caldera lake sediments dip slightly away from the center of resurgence. Because of the lower elevations in Thacker Pass, a smaller volume of the original caldera lake sedimentary package eroded south of the Montana Mountains. As a result, the thickness of the sedimentary package increases with distance from the Montana Mountains. The proposed open-pit mining activity is concentrated just south of the Montana Mountains in Thacker Pass where lithium enrichment is close to the surface with minimal overburden.

Mineralization
The Thacker Pass Deposit sits sub-horizontally beneath a thin alluvial cover at Thacker Pass and is partially exposed at the surface. The Thacker Pass Deposit contains the targeted multi-phase mining development of the Thacker Pass Project. It lies at relatively low elevations (between 1,500 m and 1,300 m) in caldera lake sediments that have been separated from the topographically higher deposits to the north due to post-caldera resurgence and Basin and Range normal faulting. Exposures of the sedimentary rocks at Thacker Pass are limited to a few drainages and isolated road cuts. Therefore, the stratigraphic sequence in the deposit is primarily derived from core drilling.

The sedimentary section, which has a maximum drilled thickness of about 160 m, consists of alternating layers of claystone and volcanic ash. Basaltic lavas occur intermittently within the sedimentary sequence. The claystone comprises 40% to 90% of the section. In many intervals, the claystone and ash are intimately intermixed. The claystones are variably brown, tan, gray, bluish-gray and black, whereas the ash is generally white or very light gray. Individual claystone-rich units may laterally reach distances of more than 152 m, though unit thickness can vary by as much as 20%. Ash-rich layers are more variable and appear to have some textures that suggest reworking. All units exhibit finely graded bedding and laminar textures that imply a shallow lacustrine (lake) depositional environment.

Surficial oxidation persists to depths of 15 m to 30 m in the moat sedimentary rock. Oxidized claystone is brown, tan, or light greenish-tan and contains iron oxide, whereas ash is white with some orange-brown iron oxide. The transition from oxidized to unoxidized rock occurs over intervals as much as 4.5 m thick.

The moat sedimentary section at Thacker Pass overlies the hard, dense, indurated intra-caldera Tuff of Long Ridge. A zone of weakly to strongly silicified sedimentary rock, the Hot Pond Zone (HPZ), occurs at the base of the sedimentary section above the Tuff of Long Ridge in most of the cores retrieved from the Thacker Pass Deposit. Both the HPZ and the underlying Tuff of Long Ridge are generally oxidized.

Core from each drill hole has been examined and drill logs have been prepared that record rock type, color, accessory minerals, textures and other features of significance. The core has mostly been divided into sample intervals for chemical analyses delineated on the basis of lithology. Figure 7-3 shows a generalized interpretation of the lithology for core hole WLC-043 which is located roughly in the middle of the proposed mine pit area.

Most of the moat sedimentary rocks drilled in the Thacker Pass basin contain high levels of lithium (>1,000 ppm). Intervals that consist mostly of ash or volcanic rock have lithium contents of less than 800 ppm whereas intervals dominated by claystone contain more lithium (>1,000 ppm). Many intervals have very high lithium contents (>4,000 ppm). Intervals with extreme lithium contents (>8,000 ppm) occur sporadically in the deposit.

There is no obvious change in lithium content across the boundary between oxidized and unoxidized rock. The highest lithium grades generally occur in the middle and lower parts of the sedimentary rock section, or in sections where these rocks have been uplifted to surface.

The lithium content of the Thacker Pass Deposit claystone can generally be correlated to the color and texture of the rock, as well as the amount of mixed-in ash. Intervals with the highest lithium grades (>4,000 ppm) generally contain gray to dark-gray or black claystone with less than 10% ash. Intervals of bluish-gray claystone with low ash content have moderate lithium content (generally 2,500 ppm to 3,000 ppm). Intervals of light-colored claystone (e.g., tan, light gray, greenish-tan) have lower lithium grades (generally 1,500 ppm to 2,500 ppm). Intervals of mixed claystone and ash are common and have variable lithium contents (generally 1,500 ppm to 3,000 ppm) depending on the type of claystone and proportion of ash present.

Mineralogy
Clay in the Thacker Pass Deposit includes two distinctly different mineral types, smectite and illite, based on chemistry and X-ray diffraction (XRD) spectra. Clay with XRD spectra that are indicative of smectite (12 – 15 Å basal spacing) occurs at relatively shallow depths in the deposit (Castor and Henry, 2020). Smectite drill intervals contain roughly 2,000 – 4,000 ppm Li. The chemistry and structure of the smectite at McDermitt is most similar to hectorite, a subtype of smectite (Na0,3(Mg,Li)3Si4O10(OH)2), though chemically the clay is intermediate between hectorite and two other smectites, stevensite and saponite (Morissette, 2012). Supported hectorite clay occurs elsewhere in the McDermitt Caldera and has been documented by several authors (e.g., Odom, 1992; Rytuba and Glanzman, 1978; Morissette, 2012; Castor and Henry, 2020).

Drill intervals with higher lithium contents (commonly 4,000 ppm Li or greater) contain clay 001 d spacing typical for illite (Morissette, 2012; Castor and Henry, 2020). This illite clay occurs at relative moderate to deep depths in the moat sedimentary section and sporadically occurs in intervals that contain values approaching 9,000 ppm lithium in terms of a whole-rock assay, higher than what a hectorite crystal can accommodate. The Li-rich illite is similar in character to tainiolite, a subtype of illite (K2[Mg4Li2]Si8O20(OH,F)4) (Morissette, 2012; Castor and Henry, 2020). A relatively thin zone of interstratified smectite-illite clay is found between the smectite and illite-type clay (Castor and Henry, 2020). Clays in this mixed layer contain basal spacing intermediate between illite and smectite.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityUnitsAvg. AnnualLOM
Lithium t 66,7832,671,318
All production numbers are expressed as carbonate.

Operational metrics

Metrics
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* According to 2022 study.

Production Costs

CommodityUnitsAverage
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* According to 2022 study / presentation.

Operating Costs

Currency2022
OP mining costs ($/t mined) USD 5.2 *  
* According to 2022 study.

Project Costs

MetricsUnitsLOM Total
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Sustaining CapEx $M USD  ......  Subscribe
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OP OpEx $M USD  ......  Subscribe
Processing OpEx $M USD 1,159
G&A costs $M USD 573
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Gross revenue (LOM) $M USD  ......  Subscribe
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Heavy Mobile Equipment

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Personnel

Mine Management

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Total WorkforceYear
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