Summary:
Salar del Hombre Muerto (SHM) is situated in the southern zone of the central Andean Puna-Altiplano plateau of South America. It is characterized by low-lying internally drained basins (salars), which are fault-bounded by mountain ranges and volcanic edifices. Salar infill geology within the SHM is regionally variable. The channel occupied by Alba Sabrina, most of the northern sector of the Eastern Subbasin including Tramo, and the southern sector of the Eastern Subbasin are clastic sediment-dominated; while the Western Subbasin and the Natalia Maria area on the eastern margin of Tincalayu Peninsula in the Eastern Subbasin are halite-dominated.
The Alba Sabrina property includes a NE-SW trending channel in the northwestern sector of the SHM, formed by the Tincalayu Peninsula (east side) and Cordon del Gallego Range (west side). This semi-isolated salar channel is clastic-dominated, with no halite intersected by drilling. Here, the bottom of the salar basin is demarcated by unaltered, low permeability Falda Ciénaga Formation quartzite. The basin infill sequence includes the basal Brecciated Quartzite, Upper Middle Sediments, Basalt, and the upper Interlayered Fine and Coarse Sediments units.
The Natalia Maria property is a halite-dominated area of the SHM, on the eastern margin of Tincalayu Peninsula. The western half of the property extends onto the Tincalayu Peninsula where Sijes Formation sediments and Incahausi Formation basalts outcrop. The eastern half of the property is in the salar. Infill units intersected by drilling include Compact Halite, Halite, Basalt, Interbedded Halite and Sediments, and the upper Interlayered Fine and Coarse Sediments units.
Tramo is in the clastic-dominated northeastern sector of the SHM. The property area is dominated by salar deposits, with a small outcrop of Sijes Formation in the southwest corner and alluvial fans on the northern, eastern, and western margins of the property. Infill geology at Tramo is a combination of lithologies that occur on the other Project properties. Basal Conglomerate, Interbedded Halite and Sediments, and Interlayered Fine and Coarse Sediments occur on the eastern side of the property. The western side of the property is dominated by Interbedded Halite and Sediments with an upper layer of Interlayered Fine and Coarse Sediments. This westward increase in halite indicates a transition towards the halite-dominated region of the salar on the eastern margin of Tincalayu Peninsula. The hydrogeological basement has not been intersected by drilling at Tramo.
Brine Resources in the Alba Sabrina, Natalia Maria, and Tramo properties of the HMN Project are defined relative to a 500 mg/L lithium cut-off. Overall, the information at the HMN Project indicates that the lithium grades and the levels of impurities compare favourably against other brine deposits.
The SHM has two large, hydraulically connected subbasins with aspects of both Evaporitedominant and Clastic-dominant salar types. The Eastern Subbasin is predominantly clasticdominated and transitions into a halite-dominated salar along the northwestern margin of the subbasin adjacent to the Tincalayu Peninsula. Tramo is located within the clastic-dominated region of the northern sector of the Eastern Subbasin, and Natalia Maria in the halite-dominated region. The Western Subbasin is halite-dominated with a halite core that transitions into an outer clastic-dominated perimeter at the margins. Alba Sabrina occupies a clastic-dominated NE-SW trending channel located at the northern margin of the Western Subbasin.
The SHM meets these conditions. The salar catchment is closed with no apparent natural outflows. Volcanic rocks of the Cerro Galan caldera and Cerro Ratones, and geothermal activity within the basin are potential sources of lithium to the salar (Godfrey et al., 2013). There is clear evidence that evaporation has led to the accumulation of evaporites and lithium brines in the near surface of the salar and at depth. The salar has a complex structural history and is characterized by a number of down-dropped, fault-bounded subbasins.
In terms of infill materials, salars that contain brine deposits are of two principal lithologic types: clastic-dominant and evaporite-dominant. The formation of one or the other may depend on the energy of the system during deposition. Evaporite formation may be favoured during relatively dry periods of low inflow, and deposition of clastic materials during higher inflow periods. Similarly, deposition of clastic materials may be favoured around the margins of the salar basin, while the more quiescent central zone may be dominated by evaporites. Consequently, both types of deposits may occur at different levels and zones of a given salar, depending on the prevailing conditions of deposition.
Evaporite-dominant salars contain mostly halite deposits, which can reach hundreds of metres in thickness. In the shallower zones, the porosity and permeability of halite may be amenable to economic extraction of brines. In the deeper zones of evaporite-dominant salars, permeability may decrease due to evaporite cementation and recrystallization.
Clastic-dominant salars are characterized by predominantly clastic strata interbedded with minor evaporites, particularly halite. Porosity and permeability of the clastic layers are controlled by lithology, stratigraphy, and faults. Clastic-dominant salars are exemplified by the Silver Peak deposit in Nevada and Argentina's Cauchari Salar.