Pastos Grandes and Pozuelos are both classified as salars, which are brine formations containing elevated levels of metals in solution, typically as salts. Salars can be found at elevations from 1,000 [m] to more than 4,000 [m] above sea level. They typically represent the end product of a basin infill process that starts with the erosion of the surrounding relief, beginning with deposition of colluvial talus and fan gravels and grading upwards to sheet sands and playa silts and clays as the basin fills. There are numerous variations on the model and the literature provides ample discussion of the relevant tectonic and sedimentary processes involved in both general and specific terms (Hardie et al, 1978; Reading, 1996; Warren, 1999; Einsele, 2000); and specifically with regard to the Altiplano-Puna (Ericksen and Salas, 1989; Alonso et al, 1991; Chong et al., 1999, Bobst et al, 2001; Lowenstein et al., 2003; Risacher et al., 2003; Vinante and Alonso, 2006).

Lithium brine projects differ significantly from hard rock mining projects due to their fluid nature. The important considerations of a brine deposit are the contained elements and chemistry of the brine and the characteristics of the host aquifer, such as aquifer extent, thickness, internal variations/heterogeneity and the physical aquifer properties, particularly porosity.

Lithium brine projects can be subdivided into two broad ‘deposit types’, depending on the salar characteristics (Houston et. al., 2011):
- Mature salars (those containing extensive thicknesses – often hundreds of meters - of halite, such as the salar de Atacama, the salar Pozuelos and the salar Hombre Muerto operation), and;
- Immature salars, which are dominated by clastic sediments, with (usually) limited thicknesses of halite. Examples are salar de Pastos Grandes, salar Pocitos and salar Olaroz/Cauchari.

Mineralization at salar de Pozuelos and Pastos Grandes consists of a lithium and potassium enriched brine of the SO4-Na-Cl variety. The brine is present throughout the salar as one or more aquifers separated by semi-permeable layers composed of sand/clay/halite mixtures. Borates (as ulexite) are primarily present within the upper 1 [m] – 2 [m] of the playa zone in the northern sector of the salar de Pozuelos basin. Borates at Pastos Grandes may be present in thin zones at almost any depth in the salar.

Sampling of brines at Pozuelos shows that the Mg:Li ratio is typically in the range of approximately 5:1 to 7:1, with lithium grades varying across the salar and with depth, but typically in the range of approximately 300 [mg/l] to approximately 600 [mg/l]. Brines at Pastos Grandes show relatively low surface values for lithum (100 [mg/l] – 300 [mg/l]) but can be locally higher. Samples recovered at depth show increased lithium values typically in the range of 300 [mg/l] to approximately 600 [mg/l]. The average Mg:Li ratio at Pastos Grandes is approximately 6.3:1.

Calcium and sulphate values at Pozuelos and Pastos Grandes are complementary, permitting blending of the brines to achieve efficient precipitation of undesirable salts.

The mining method considers 24-hour extraction of brine from production wells. Brine extraction considers the use of electrical submersible pumps in each production well. The brine is pumped through a pipe network that connects each production well field (Pastos Grandes and Pozuelos) with the Brine Transfer/Mixing Pond located at Pozuelos. From there the mixed brine is pumped to the evaporation ponds, the first stage of the project’s processing component.

The operating brine extraction wells will be relocated throughout the brine resource areas of both salars during the life of the project.
Additional wells are added as required to provide constant blended flow as the salar draws down over time. The associated network of brine gathering pipelines will be relocated and amended to service the operating well locations as they progress across the salars. It is envisioned that brine will be supplied by a combination of deep and shallow wells and trenches.

Basic mining infrastructure for brine extraction considers:
- Consolidated access road and platform for rig and well services
- Consolidated pad for drill location and drilling equipment
- Production wells, including pumps and electricity supply
- Pipe network connecting each well area to the process area (evaporation ponds and process plant) .

A total of 1200 [m3/h] of raw brine feed is required to support the lithium carbonate production system. The system targets a blend of 500 [m3/h] from Pastos Grandes and 700 [m3/h] from Pozuelos. The Pozuelos feed blend initially targets production of 500 [m3/h] from the deep southern depositional centre, with the remainder being produced from shallow trenches immediately south of the evaporation ponds.

When the higher grade portions of Pozuelos are depleted after several years of operations, additional wells will be added in the lower grade areas, which will be supported by additional primary evaporation ponds. This is currently expected to occur in Year 7. The connection between Pozuelos and the well field in Pastos Grandes is expected to be completed in Year 3 of mining operations.

The project considers the production of 20,000 tons per year (TPY) of Battery-Grade Lithium Carbonate (Li2CO3). The lithium is obtained from brines extracted from Pastos Grandes and Pozuelos Salars to produce a brine blend within the desired ratio of impurity elements.

The process plant is conveniently divided into two discrete building blocks:

- Brine Treatment Plant, which comprises the processes of evaporation and chemical treatment for impurity removal in three sections:
- Primary concentration and primary brine treatment stage,
- Secondary concentration and secondary brine treatment stage,
- Tertiary concentration stage where the target lithium-in-brine concentration is achieved by evaporation.

- Lithium Carbonate Plant which comprises the final purification stages before lithium carbonate is produced, filtered, milled, dried and bagged for export. Included in this section are:
- Ion Exchange for the removal of impurities,
- Precipitation of lithium carbonate employing sodium carbonate,
- Drying, size reduction and packaging of the final product.

The process, used on the PPG project employs common process building blocks to extract and produce lithium from salar brines. As conceptualized for this preliminary study and report, the process relies on commonly available techniques and equipment. The author has not reviewed the process in detail for any available patents and recommends that this is done in the future to ensure that the process is fully within the rights of LSC to operate as designed.

The overall operation, including ponds and process plant, has been sized for an 85% mechanical and process availability.