Summary:
The Kuska project is located in the Salar de Ollagüe basin, between the western and eastern volcano belts. The Salar consists mostly of salt flats (Qs) and unconsolidated deposits. The saline deposits include sulphate, chloride, and borate evaporite minerals. The salt flats are intermontane depressions with endorheic (a closed drainage basin) drainage where evaporite minerals are formed due to the high evaporation rate and constant evapo-concentration of the surface and groundwater.
The eastern and western belts, where the Aucanquilcha and Ollagüe volcanoes are prominently located, consist of stratovolcanoes, ignimbrites, and porphyry domes represented by the following units: Ms3i, P3i, Q3i, Ms3t.
The oldest unit in the area corresponds to andesitic stratovolcanoes (Ms3i and P3i), highly weathered in both the eastern and western belts and surrounded by modern lava centres. The radiometric age K-Ar indicates a range from 15 to 8 mya (Ramirez & Huete, 1981). The composition of this lava is mainly andesitic and incorporates hornblende andesite with pyroxene andesite. The stratigraphic relation of this unit is covered by younger Upper Miocene and Pliocene ignimbrites.
The Ms3t unit corresponds to rhyolitic and dacitic ignimbrites of various degrees of welding. The age of these ignimbrites ranges from 5 to 7 mya (Ramirez & Huete, 1981). These flows are located north of Salar de Ollagüe, covering older units.
Younger stratum volcanoes and volcanic flows (Q3i) of andesitic and dacitic composition also occur in the area. In some areas, porphyritic dacitic domes occur. The domes show flattened shapes with abrupt edges due to high lava viscosity. The craters of the volcanoes have not been strongly affected by weathering. The principal volcano in the area is the Ollagüe volcano, with a conical shape composed of gray, pyroxene-rich andesitic lavas, and pyroclastic sequences. There is a hydrothermal sulphur deposit near the peak. Radiometric dates suggest ages from 3 to 2.5 mya. The domes consist of gray, porphyritic dacite, with feldspar phenocrysts, biotite, and scarce quartz; the age estimated for this unit is 1.5 ±0.1 mya.
Unconsolidated deposits (PPL1C) are distributed throughout the area. These are interbedded with saline deposits and cover many of the older units in the area. These deposits are composed of different kinds of sediments, including alluvial and fluvioglacial sediments, moraines, lahars, and pyroclastic deposits (Maksaev, 1978). It is estimated that the age range is Lower PleistoceneHolocene.
The youngest units in the area are the evaporites which include calcium and sodium sulphate minerals, calcium carbonate, sodium chloride, and borates (MQs). These deposits are continually being formed, so they are considered to be the most modern deposit in the area.
Deposit Type
The deposit type is a brine aquifer within a Salar basin. Based on the available information, the Salar appears to be an immature salar according to the classification developed by Houston (2011). Based on the results of exploration conducted by third parties (Hanson, 2019) and the recent drilling program completed by Wealth Minerals, five tentative hydrogeologic units were defined. The lower four (4) of these units contained lithium-rich brine and were used to estimate the lithium resource. The upper, predominantly clastic unit has not yet been shown to contain lithium-rich brine and was therefore not considered in the resource estimate. These four (4) units make up the main brinesaturated aquifer units; assigned drainable porosity values are shown below.
Mineralization
Mineralization for the Project consists of a lithium-enriched brine that is contained within the pore spaces of the different lithological units formed by evaporitic processes within the Salar basin. In the case of Salar de Ollagüe, the mineralized brine is located only in the deeper part of the aquifer system in the areas explored to date. The boundaries of the mineralization are suspected to be the basin boundary, although some lithium-enriched brine may be contained in the fractures and/or pores of the older rocks that form the basin boundary. Due to the mobility of the brine, the flow regime, and other factors such as the hydraulic properties of the aquifer material, are considered to be just as important as the chemical constituents of the brine.