The Thacker Pass Deposit is located within an extinct supervolcano (30 km by 40 km) named McDermitt Caldera, which was formed 16.3 million years ago and is associated with the Yellowstone hotspot. For a few hundred thousand years following the volcanic eruption, water percolated through nearby volcanic rocks resulting in the leaching of lithium. The lithium was then deposited in the caldera basin, forming a large caldera lake and a thick sequence of associated lacustrine deposits.

Renewed volcanism uplifted the center of the caldera, draining the lake and bringing the lithium-rich sediments to the surface of the earth in the vicinity of the present-day Montana Mountains.

Recent drilling confirms that the lithium mineralization is extensive, which suggests that the formation of lithium-rich clays is not associated with hydrothermal activity. The lithium mineralization is due to burial diagenesis and/or primary erosional processes. In the immediate project area, lithium-rich clays are typically overlain by alluvium with an average thickness of approximately 5 m and underlain by rhyolitic volcanics. Interbedded basaltic beds also occur deepening from the northwest to the southeast. The clay itself is interbedded with ash. Mineralogically, the upper clay horizons are dominated by smectite-type clay, while the deeper horizons are dominated by illite-type clay, with the latter showing mineralization of up to 9,000 ppm, and the former up to 4,000 ppm. This differentiation supports the diagenesis hypothesis.

Vertical drilling indicates that the clay intersections range from a few meters up to 90 m.

Lithium Americas Corp. is engaged in a exploration program to expand the resource in the vicinity of the proposed pit area. In 2017, Lithium Americas Corp. identified a new target area south of the proposed pit area called the Southwest Basin. Exploration assay results, published in the May 2017 Technical Report, demonstrate that Li mineralization in the Southwest Basin occurs at grades and depths similar to the proposed pit area. Recent seismic surveys and ongoing exploration drilling aims to increase the confidence of the Southwest Basin resource and define the total extent of Li mineralization throughout the McDermitt Caldera.

The mining operation for the Project is planned as a simple and low-cost open-pit mine using a small fleet of surface miners. Given the soft nature of the claystone, minimal blasting is anticipated and will be limited to areas in the deposit with basalt formations. The mine plan includes excavating highest-grade and lowest strip ore in the early years of production.

The production process is designed to use conventional and commonly-available equipment, arranged to take advantage of the distinctive qualities of the high-grade ore.  The process comprises a series of steps to concentrate, separate and produce battery-grade Li₂CO₃.

First, ore from the mine will be crushed, screened and then transferred as a slurry to the leaching circuit where sulfuric acid will be added to attack the ore and liberate the lithium from the clay. The high-grade quality of the ore allows for leaching to occur in stirred reactors (vats), specifically designed to maximize speed and efficiency of lithium dissolution, while minimizing sulfuric acid consumption. Total leaching time is estimated at three hours.

The resulting lithium-bearing solution will then go through a pH-neutralization step. Neutralization will be achieved with ground limestone during start-up and sustained with recycled alkaline solids from an upstream precipitation process during normal operation. Next, the lithium solution will undergo a crystallization step using steam and electricity from the sulfuric acid production process. Water is removed for recycling, and magnesium sulfate (Epsom salt) is produced. Any magnesium remaining in solution is removed in a second step that involves the addition of reagents to precipitate magnesium hydroxide.

Finally, soda ash will be added to the lithium bearing solution to produce a high-quality, battery-grade Li₂CO₃. Much of the water contained in the lithium solution will be recovered and returned to the process.  The total time projected to manufacture battery-grade Li₂CO₃ from the ore is less than 24 hours. The overall recovery of lithium from the ore is 83%.

Environmental leadership is a core value of Lithium Americas.  Thacker Pass has been engineered to minimize the environmental footprint, by avoiding sensitive environmental habitat and employing the best available environmental control technologies.

Lithium Americas has developed a community engagement plan, recognizing that the well-being of all stakeholders is essential to the success of the Project.  The Project was designed reflecting information collected during numerous stakeholder meetings, including a public open house. This approach is expected to mitigate potential concerns at the design level, and ensures the local community is included early in the development process.  Future public open houses are planned as the project advances to ensure the community is fully engaged.

The process for permitting a lithium mine on federal lands in the USA is currently being reviewed as a result of Presidential Executive Order 13817, which calls for a federal strategy to ensure secure and reliable supplies of critical minerals.  A critical mineral is defined as being a non-fuel mineral, with a vulnerable supply chain, that is essential to the economic or national security of the USA. Lithium is categorized as a critical mineral. The new federal strategy is expected to include streamlining of permitting and review processes to expedite production of critical minerals.

Phase 1 of the project is located entirely on federal lands administered by the Bureau of Land Management (BLM), which will be the lead agency for issuing federal approval under the Mining Law surface management regulations and for the preparation of the Environmental Impact Statement (EIS). Other permits will be required from various state and federal agencies.

The project could benefit from an accelerated permitting procedure that supports the federal mandate to enhance domestic lithium production. For the purposes of the PFS, a construction start date of Q4 2020 was assumed. This may be revised once details of the new federal permitting process are released.

Lithium Americas began the permitting process in Q1 2018 by commencing baseline data collection.  The baseline data collection process is scheduled to be substantially complete by Q4 2018. A Mine Plan of Operations is expected to be ready for submission in Q3 2018, with the EIS to be submitted to the regulators by Q3 2019.  Approvals would be issued following the regulatory review of the EIS.