HYDROGEOCHEMICAL CHARACTERIZATION OF SURFACE, SHALLOW, AND DEEP GROUNDWATERS OF THE PRIMARY INFLOW TO THE LITHIUM BRINE AQUIFER OF SALAR DEL HOMBRE MUERTO, ARGENTINA

The Rio de Los Patos watershed of the Puna de Altiplano, Argentina, in Salar del Hombre Muerto is rapidly being developed into a globally important lithium resource and exploration target. Several companies interested in lithium exploitation now operate within the basin, and are beginning to extract water and brine from shallow and deep wells. As such, we investigate the connection between the surface and subsurface waters based on hydrogeochemical data collected within the Rio de Los Patos watershed. We use a suite of geochemical and stable isotope data from surface and groundwater along the length of the Rio de Los Patos, from the high elevation headwaters to the delta region of the Salar del Hombre Muerto. The Rio de Los Patos surface water evolves from Ca-HCO₃ in the headwaters to Na-Cl waters where they ultimately reach the Salar nucleus. Shallow groundwaters are Na-Cl type, however, these waters are enriched in HCO_{3 .} Stable H and O isotopes of the shallow groundwater and surface waters indicate these water chemistries are controlled by evaporation. Surface and shallow groundwater are geochemically similar indicating a connection between the surface and shallow systems. Deep groundwater is Na-Cl type with distinctive chemistry compared to the shallow groundwaters and surface water. The deep groundwater chemistry is likely controlled by mineral precipitation and dissolution, and chemical weathering. All of these hydrogeochemical processes are part of the lithium sourcing and transport to the Salar. Future mining and direct lithium extraction activities within the watershed may alter the water quality of surface and shallow waters. Building a conceptualization of the Rio de Los Patos aquifer based on hydrogeochemistry will aid in our ability to assess how future activities may affect water quality within the basin.