The Sonora lithium project located in Sonora, Mexico, is located approximately 11km from the town of Bacadehuachi and 170km from the US-Mexico border.

The project is being developed as an open-pit strip mine with operation planned in two stages. Stage 1 will last for four years with an annual production capacity of approximately 17,500t of lithium carbonate, while stage 2 will ramp up the production to 35,000 tonnes per annum (tpa).

The mining project is also designed to produce up to 28,800tpa of potassium sulfate (K2SO4), for sale to the fertiliser industry.

Bacanora Minerals (70%) is developing the project in a joint venture with Cadence Minerals (30%). Bacanora will also act as the operator.

Bankable feasibility study of the project was completed in January 2018, with first stage operations expected to be commenced in the first quarter of 2020.

Sonora lithium project location, geology, and mineralisation

The Sonora lithium project is situated within the Sonoran Desert in an area of 8,154ha on the western portion of the Sierra Madre Occidental physiographic province.

The property is underlain by rhyolitic tuffs of Oligocene to Miocene age, ignimbrites and breccias of the upper volcanic complex of the Sierra Madre Occidental.

The mineralisation consists of two discreet upper and lower units of lithium-bearing clays localised within volcaniclastic sediment successions in the basins.

Sonora lithium project reserves

As of January 2018, the proven and probable ore reserves at Sonora were estimated to be 244Mt, grading 3,480ppm Li and 1.45% potassium. The mine is estimated to contain 4.5Mt of lithium carbonate-equivalent (LCE).

Mining and ore processing at Sonora lithium project

Open-pit strip mining, using front-end loaders and haul trucks, is proposed as the primary mining method for the operation. A fleet of dozers, graders, and water trucks will also be used for the mining.

Approximately 37.1Mt of ore at a diluted grade of 4,151ppm of lithium and 1.76% potassium will be mined through its life-of-mine.

The integrated processing plant is expected to process 1.1Mt of ore a year during Stage 1, which will be increased to approximately 2.2Mtpa in Stage 2.

The plant will also simultaneously produce K2SO4/SOP product through a series of evaporation and precipitation stages.

The processing plant comprises a pre-concentration stage to produce concentrate slurry prior to roasting. The concentrate will be heated in a kiln, at approximately 950°C, in combination with re-cycled sodium sulphate (Na2SO4) to produce an intermediate lithium sulphate (Li2SO4) product.

The material will then pass through hydrometallurgical treatment, filtration, cleaning, precipitation, and packaging processes to produce a high-grade Li2CO3 final battery-grade product.

Infrastructure

Access to the project area from the town of Bacadéhuachi is through a 11km-long secondary, dry-weather road, across various privately-owned ranches.

Workers will be accommodated at the modular, camp style facilities to facilitate Stage 1 operations. The facilities will be upgraded as part of the second stage operations.

Power supply for the project will be provided by a combined heat and power (CHP) natural gas turbine, which will generate 33kV power.

Two existing water wells, located 7km north of the plant site, will supply raw water to the processing plant and accommodation facility under stage 1. A third well is proposed for Stage 2 mining operations.

Project financing and off-take agreements entered

Bacanora signed an investment and off-take agreement with Ganfeng Lithium (GFL) for the Sonora project, in June 2019. Ganfeng agreed to acquire 29.99% equity interest in Bacanora for a cash consideration of £14.4m and will earn right to purchase 50% of lithium produced under the stage 1. It is also be eligible to purchase 75% of lithium products under stage 2.

As of December 2018, Bacanora secured $240m in project financing from three companies, including $150m from RK Mine Finance, and $65m and $25m conditional equity commitments respectively from the State General Reserve Fund of Oman (SGRF) and Hanwa, a trading group based in Japan.

Hanwa will receive lithium from Stage 1 production for an initial period of ten years. SGRF, the sovereign wealth fund of Oman, has the option to off-take 10,000tpa of lithium, under a strategic investment agreement.

In August 2015, Bacanora Minerals and Cadence (formerly Rare Earth Minerals) signed a partnership agreement with Tesla to supply lithium from the Sonora project.

Contractors involved

Bacanora Minerals engaged Hatch as the engineering consultant of Sonora lithium project, in October 2014.

Ausenco Services prepared the technical report on the feasibility study of the project. Ausenco also participated in the feasibility study preparation along with SRK Consulting (UK), Independent Mining Consultants (IMC), and Solum Consulting Group.

IMC worked on the mine plan optimisation and equipment selection as well as prepared the mineral reserve estimate of the project.