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We document, analyse, and interpret direct and rapid infiltration of precipitation to the southern margin of the Salar de Atacama halite-hosted brine aquifer during two intense precipitation events in 2012-2013. We present physical, geochemical, and stable and radioactive isotope data to detail this influx of water. The two events differ distinctly in the mechanisms of recharge. The 2012 event did not produce direct precipitation onto the salar surface, while the 2013 event did. Both events are recorded by abrupt changes in head in observation wells along the halite aquifer margin. Spatially distributed water levels rose by over 30 cm during the larger 2013 event consistent with remotely sensed observations of surface water extent. The lithium concentration and stable isotopic composition of water indicate dilution of brine and dissolution of salt with fresh water. Tritium measurements of precipitation, surface water, and groundwater all indicate modern influx of water to the halite aquifer along the southern margin. We extend these observations by examining the response of the halite aquifer as a whole to precipitation events during the period of 2000-2010. This study suggests that local recharge to the aquifer during sporadic precipitation onto the halite nucleus is an important component of the modern water budget in this hyper-arid environment. The rapid dissolution and salinization along the southern margin of the salar halite nucleus are aided by such precipitation events contributing a modern fresh water component to the water budget of the economically valuable lithium-rich brine. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The accumulation of solutes delivered via shallow groundwater and surface water in arid to hyper-arid closed basins, and the complex hydrogeochemical processes associated with their transport, are key to deciphering mechanisms responsible for the formation of brines and salts in these environments. A rigorous investigation of the hydrogeochemical fluxes and the formation of the Li-enriched brine in the hyper-arid basin of the Salar de Atacama, Chile is presented. Water fluxes within the Salar de Atacama basin range from 0.003 m 3 /s to 1.50 m 3 /s with a poor correlation between discharge and drainage basin area. The inflowing waters have major elemental and Li concentrations that are within the same order of magnitude over a period of several decades. The element fluxes indicate, for example, that 58% of the Li in the halite nucleus and brines is derived from the south and southeast parts of the basin. The average δ 18 O vsmow and δD vsmow of inflow waters indicate that there are varied sources of recharge corresponding to the defined sub watershed regions. The average water flux-weighted 87 Sr/ 86 Sr of inflow waters allows further definition of where in the regional watershed the solutes are derived. The predicted water flux weighted 87 Sr/ 86 Sr of the brines (0.70813) compared to the measured average 87 Sr/ 86 Sr (0.70801), indicates that there may be unaccounted sources of water and solutes to the basin brines. Elemental accumulation time scales for the volume of halite and brine in the nucleus balance on time frames of 0.5 Ma (Mg), 1.0 Ma (Ca), 1.9 Ma (Li) and 2.2 Ma (K) as compared to 47 Ma (Na) and 53 Ma (Cl), further evidence that Na and Cl require additional sources not accounted for in the modern inflows to the topographic watershed. Dissolved noble gas concentrations of marginal and nucleus brines specify that the brines formed in an atmospheric equilibrated state and have since been isolated below the salt crust. A process-based model is presented to explain the extremely high concentrations of Li in brines which incorporates the δ 7 Li isotope signatures of waters in the basin to further decipher, on a first order, the contributions of processes such as low temperature weathering and secondary phase formation. [ABSTRACT FROM AUTHOR]