231-10 Water and Lithium Flux Between Topographically Closed Basins Governs Deposit Formation in a High Andean Salar

Session: Critical Mineral Resources and Recovery in the Americas: Emerging Methods in Exploration and Sustainable Extraction (Posters)

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The Salar de Pozuelos (Salta, Argentina) is an endorheic, lithium-bearing salt flat in the “Lithium Triangle” of Argentina, Chile, and Bolivia—a region hosting approximately half of global lithium resources, including two thirds of lithium brine. Lithium brine development requires certain characteristics: aridity, salt crust formation, thermal activity, lithium-rich sources, tectonic subsidence, time, and basin hydrogeology. Geologic, morphologic, and contemporary climatic conditions in the Salar de Pozuelos cannot account for the present-day brine’s grade and resource scale. Elsewhere, regional groundwater flow has been shown to sustain individual basins’ brine budgets. Fully describing lithium sources, sinks, and processes is crucial for defining resource quality and longevity, while potential lateral coupling in lithium cycling implicates regionwide impacts from a single extraction project. 

This study characterizes the Salar de Pozuelos hydrologic watershed and its connection with the neighboring, upgradient Salar de Pastos Grandes via a canyon incised through a lithium-bearing evaporite unit. A machine learning model derived from high-resolution remote sensing imagery is applied to predict the thickness and geometry of the canyon’s alluvial infill, which, together with physical hydrologic field measurements, provides the basis for a groundwater flow model. Initial results suggest that the daily amount of lithium brine flowing into Pozuelos from Pastos Grandes is similar in magnitude to the daily yield from a fully operational pumping well. Model results are compared to passive seismicity measurements made at discrete points within the canyon, which are processed to estimate the depth where stratigraphic competency increases and to proxy alluvial infill thickness. Results demonstrate that infill thickens upstream towards Pastos Grandes, evidencing the canyon’s incision, and structural and stratigraphic controls on the infill gradient are also investigated. Solute mass balance calculations, part of a broader water budget characterization for Pozuelos, indicate that the basin’s hydrologic watershed is not closed within the basin’s topographic watershed. Thus, its lithium supply depends on resources originating hydraulically upstream, where extraction is likely to alter the regional hydrology in which the deposit evolved. This contemporary conceptualization will help direct stratigraphic, geochronologic, and paleo hydrogeochemical research into the canyon’s incision, and its role in the Pozuelos deposit’s origins and accumulation rates, as well as aid the siting and sustainable productivity of brine pumping wells in both basins. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10571

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