Summary:
The lithium occurrences at Falchani are hosted in an ash-flow Tuff named Lithium Rich Tuff (LRT) and volcanoclastic breccias (Upper and Lower Breccia, UBX and LBX) that bound the LRT. Lithium mineralization is also observed in the basal Coarse Felsic Intrusion (CFI) which is interpreted to be a stratiform felsic intrusion underlying the above lithium host rocks. Elevated concentrations of cesium, potassium, and rubidium are associated with lithium mineralization and these elements show potential to be included as a byproduct of lithium processing to produce battery grade lithium carbonate. The general dimensions of the mineralized zone at Falchani covers an area approximately 3,300 m wide by 2,440 m long extending from outcrop to a maximum modelled depth of approximately 1,000 m below surface. The mineralization is continuous from surface. The highest and most consistent lithium grades occur in the LRT. The basement mineralized coarse felsic intrusion has a known depth of 400 m from drillhole intercepts, however the maximum thickness of the unit is still unknown.
Lithium mineralization within the Falchani Project is hosted in shallowly dipping acidic tuffs, with pyroclasts from sub-macroscopic to 60 mm in size. These volcanic rocks are contained within the Macusani Volcanic Field (MVF) and described further by Torro et al. 2022. Primary minerals constituting the tuff are quartz, orthoclase, and plagioclase in a groundmass of amorphous glass. Crude bedding is evident in some outcrops and is based on strata containing larger and smaller pyroclasts. The petrography of the samples analysed by Thatcher (2011) indicate that the acidic volcanics (crystal lapilli tuffs) may contain varying rock type compositions ranging from rhyolite to dacite to latite which supports the likely presence of stratigraphic layering of the volcanic pile.
In the immediate vicinity of the boreholes drilled at Falchani, the youngest rocks appear to be classified by Plateau Energy Metals as the Upper Rhyolite. The Upper Rhyolite forms prominent outcrops, demonstrates crude bedding, and is shallowly dipping to the northnortheast. Outcrops of the Upper Rhyolite demonstrate similar appearance to the acidic tuffs of the Yapamayo and Sapanuta Members of the Quenamari Formation, which host nearby uranium mineralization.
Below the Upper Rhyolite is the Upper Breccia, which separates the Upper Rhyolite from the Lithium Rich Tuff (LRT). The Upper Breccia is not well defined in outcrop but is very distinctive in core. The Upper Breccia contains angular clasts of volcanic material, in a very fine groundmass. The LRT is a light grey to white, very fine-grained rock, with prominent layering.
The contact between the LRT and the Lower Breccia is less marked than the Upper Breccia. The Lower Breccia has been identified in outcrop in the Tres Hermanas trenches and has been interpreted from drilling. Below the Lower Breccia is Coarse Felsic Intrusion (CFI), another lithium mineralized basement lithological unit.
The thickness of the Upper Breccia varies from 10 m to 20 m, while the thickness of the Lithiumrich Tuff varies in drilling from 50 m to 140 m. The Lower Breccia unit varies in thickness. Recent drilling further demonstrates that the Lower Breccia unit may reach thicknesses of up to 175 m and contains large (up to 20 m intercept lengths) blocks of Lithium-rich Tuff. The CFI below the Lower Breccia extends beyond the limits of the modelled resource and has been intersected by 28 drillholes with the max depth of 407 m in drillhole PZ01-TV3. The CFI is interpreted to have a higher density of 2.7 g/cm3 in comparison to the upper mineralized zones. The density has been determined based on the similarity to that of analogous igneous intrusive rock types such as andesite and granite.
Mineralization
The general dimensions of the mineralized zone at Falchani covers an area approximately 3,300 m wide by 2,440 m long extending from outcrop to a maximum modelled depth of approximately 1000 m below surface. The mineralization is continuous from surface to depth. The highest and most consistent lithium grades occur in the Lithium Rich Tuff. The basement mineralized coarse felsic intrusion has a known depth of 400 m from drillhole intercepts, however the maximum thickness of the unit is still unknown.