Minera del Altiplano S.A. (MdA), Livent’s Argentine operating subsidiary, owns and operates lithium brine production facilities and related chemical processing plants in the Western Subbasin of Salar del Hombre Muerto (SdHM). The operation is referred to as Project Fenix.
On January 4, 2024, Allkem and Livent Corp. officially completed their merger to become Arcadium Lithium plc. Livent Corp. is now a wholly owned subsidiary of Arcadium Lithium plc.
On March 6, 2025, Rio Tinto completed its acquisition of Arcadium Lithium plc. Rio Tinto is now the ultimate parent company of Arcadium Lithium, which will become Rio Tinto Lithium.
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Summary:
The sedimentary evaporite and associated clastic deposits of the Western Subbasin of Salar del Hombre Muerto (SdHM), which host lithium-rich brine, are characteristic of a mature salar with a halite core. Mature salars have unique hydrogeologic characteristics (high transmissivity and high degree of reservoir homogeneity) favorable to lithium brine extraction. Additionally, the Western Subbasin contains brine with a low ratio of magnesium to lithium, which is preferrable for mineral processing. The shallow (0–40 m bgs) geology at SdHM, where the measured lithium resources occur, was thoroughly characterized prior to development. Pre-development characterization in the early 1990s has been further supported by 25 years of operations at Project Fenix, installation of a brine monitoring well network in 2017, and deep characterization (up to 200 m depth) exploratory boreholes in 2000.
Mineral deposit
There are several key characteristics that allow lithium-rich brines to develop over time within Salar sediments. The characteristics required are an endorheic basin, arid climate, tectonically driven subsidence, igneous or geothermal activity, lithium-bearing source rocks, adequate aquifer(s)/reservoir(s), and sufficient time to concentrate the brine (Bradley et al. 2013). SdHM, along with other lithium-rich salars in the lithium triangle, each bear these characteristics to varying degrees.
The volcanic arc of the western Cordillera, eastern volcanic centers, and Altiplano-Puna magma body, which have been active from the Miocene to present day, are the origin of boron-rich fluids—the source of borate in SdHM (Alonso 1999). The presence of arsenic, antimony, and lithium in modern boron-rich hot springs and buried deposits favors a common origin model for lithium in the SdHM (Alonso 1999). The current chemistry of SdHM resulted from the dissolution of constituents by infiltrating surface water or hydrothermal fluids rich in boron or sodium chloride that flowed into SdHM, were concentrated in solution, and precipitated due to evaporation or supersaturation (Alonso 1999; Houston et al. 2011; Munk et al. 2016). Lithium continues to concentrate in brine after halite saturation is reached (Houston et al. 2011). These mechanisms result in brines that increase in lithium concentration from relatively dilute in fresh water entering the Salar to lithium-rich brine in the Western Subbasin’s halite nucleus (farthest from entering surface waters).
The lateral boundary of the evaporite sedimentary deposits of the Western Subbasin of SdHM is roughly circular in shape, coinciding with the contact between sediment and surrounding bedrock, consisting mainly of Paleozoic metamorphic graywackes and shales. The Incahuasi Formation, consisting of Quaternary-aged clastics, evaporites, basalts, and andesites, forms the northern boundary. Neogene volcanic dacites and andesites form the eastern and southeastern boundary of the depositional basin.
The deposit is hydraulically unbounded at the saddle where the Eastern and Western Subbasins connect, which allows brine in the Eastern Subbasin and brackish water from the Rio de los Patos to enter the Western Subbasin. The deposit is open to the south where the groundwater flow from the Trapiche Aquifer enters the Salar. At both locations, water or lithium-rich brine flows into the deposits of the Western Subbasin. The vertical extent (depth) of the lithium-rich brine deposit has not been determined. Based on surface geophysical surveys, and several deep (>200 m) drilling locations, the bedrock–halite contact is likely greater than 200 m in most of the Western Subbasin and may exceed 900 m in the northwestern portion of the subbasin (WMC 1994).