The Pastos Grandes Project is currently holded by Proyecto Pastos Grandes S.A., indirect wholly-owned Argentinian subsidiary of Lithium Americas (Argentina) Corp.
On March 5, 2024, the Company announced that it and certain of its subsidiaries have executed a definitive agreement with a subsidiary of Ganfeng whereby Ganfeng agrees to acquire US$70 million in newly issued shares of Proyecto Pastos Grandes S.A. (“PPG”), the Company’s indirect wholly-owned Argentinian subsidiary holding the Pastos Grandes Project, which is expected to represent an approximate 14.89% interest in PPG and the project (the “Pastos Grandes Transaction”). Completion of the Pastos Grandes Transaction is expected in the second quarter of 2024.
Summary:
The geology of the Pastos Grandes Project consists of a relatively low permeability upper saline lacustrine unit with variable thickness. This upper unit is underlain in most parts by a lower brine aquifer hosted in unconsolidated sediments that consists of alluvial sediments, a clastic unit, and a basal gravel / breccia unit with a variable thickness of over 400 m to a drilled depth of 635 m.
Salar de Pastos Grandes is a mature salt flat, with a well-developed halite crust. In the central portion of the salar, the crust can reach a thickness of several hundred meters, with a thin clay layer that is constantly being generated through evaporation in the shallower beds.
Mature salars are characterized by a relatively thick and uniform sequence of halite deposits in variable sub-aquatic and sub-aerial conditions. Nevertheless, ancient floods leading to widespread silty clay deposits and volcanic fallout have led to thin intercalated beds that can be recognized in drill core and geophysical surveys.
The brines from Pastos Grandes are solutions saturated in sodium chloride with an average concentration of total dissolved solids (TDS) of 302 g/L and an average density of 1.19 g/cm3. The other components present in the Pastos Grandes brine are K, Li, Mg, SO4, Cl and B with relatively low Ca. The brine can be classified as a sulphate-chloride type with anomalous lithium. Lithium concentrations in Salar de Pastos Grandes have an average value of 392 mg/L, with some samples reaching up to 700 mg/L.
Deposit Type
The Salar de Pastos Grandes is classified as a “Silver Peak, Nevada” type, terrigenous salar. Silver Peak, Nevada, USA was the first lithium-bearing brine deposit exploited in the world. These deposits are characteristic of arid zone, restricted basins within deep structural depressions in-filled with inter bedded clays, salt (halite), sands and gravels. In the Salar de Pastos Grandes, a lithium-bearing aquifer developed during arid climatic periods under similar conditions.
Mineralization
Ulexite hosted in Quaternary and modern sediments is common in the eastern side of the salar, close to the road to Sijes. It occurs either as small rounded concretions (“papas") in red clays and brown sands, or as a continuous layer (“barra”). Ulexite and colemanite are observed in the horizons of borates hosted in the Sijes Formation (Late Miocene) outcropping east and south of the Pastos Grandes Salar.
Halite is a common mineral within the Salar Pastos Grandes and is mined by digging pools of 4 meter by 1 meter wide and 1 meter. The pools become filled with brine rich in NaCl. The water evaporates at a rate of 6-8 mm/day, concentrating crystalline halite. Each pool is filled with salt in 5 to 6 months and "harvested" with backhoes or loaders. It is accumulated for dehydration before being shipped in bulk or in large bags.
Mineralization at the Property includes lithium-potassium rich – relatively low magnesium brine as detected through surface sampling and drilling. The brine can be classified as a sulphate-chloride type with anomalous lithium. Lithium concentrations at the surface at Pastos Grande Salar range from about 100-300 mg/L. Lithium concentrations increase with depth, with holes as shallow as 10 meters reporting as much as 400 mg/L. A value of 578 mg/L was reported at a depth of 30 meters in borehole DW01PG. The highest values at surface occur along the western margin of the salar, while at depth the values increase towards the south-central basin. Potassium-lithium ratios throughout the drilled area are in the 10:1 to 12:1 range. This is comparable to Salar de Hombre Muerto, where process simulations indicated a rate of production for potash at slightly less than 4 tonnes of potash for each tonne of LCE produced.
Average magnesium:lithium ratio is about 6.3:1 based on recent exploration drilling and testing. The lowest values found in the lithium triangle are in the range of 2.5:1.