Hydrochemistry, isotope studies and salt formation in saline lakes of arid regions: Extra-Andean Patagonia, Argentina

ALVAREZ, MARÍA DEL PILAR; CAROL, ELEONORA; EYMARD, INÉS; BILMES, ANDRÉS; ARIZTEGUI, DANIEL

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2022 vol. 816

0048-9697

The most favourable locations for the development of saline lakes are in the rain-shadow of mountain ranges,which provide large areas of precipitation catchment while the base of the basin is under arid climate and exposedto evaporation. These conditions are found in Extra-Andean Patagonia under the rain-shadow generatedby the Andean cordillera. There, an endorheic basin with two shallow and saline lakes, Cari Laufquen Chica(CLC) and Cari Laufquen Grande (CLG), was studied with the aim of analysing the factors that condition thehydrochemical processes acting in the formation of evaporites associatedwith these environments. Amonitoringnetworkwas installed and five surface and groundwater survey campaigns were carried out at different points inthe basin to define groundwater flow and also to extract samples. In situ pH, electrical conductivity and temperatureand laboratory physicochemical determinations of major ions and stable isotopes of the water were measured.SEM-EDS and XRD analyses of saline crusts fromthe edge of the lakes and adjacent sedimentswere carriedout. The obtained results allowed identifying that CLC and CLG saline lakes have different surface watergroundwaterconfigurations. CLC is a flow-through shallow lake, while CLG is a discharge shallow lake. Theanalysis of the saline precipitates and the chemical facies of the water allows identifying cycles of dissolution,evaporation and precipitation in both saline lakes. However, the different groundwater flow between the twolakes is reflected in their salinity as well as in the evolution and development of saline precipitates. CLC salinelake shows a dissolution-precipitation trend of thenardite and Ca-Mg carbonates, whereas CLG saline lake displaysa trend of dissolution-precipitation of halite, thenardite and trona with strong dominance of halite. Thepresent study identifies for the first time the main factors conditioning hydrochemical processes in these saline lakes of extra-Andean Patagonia. Our results indicate that the hydrological configuration with respect to thegroundwater flow is the prevailing factor setting the hydrochemical processes that trigger the formation of saltcrusts.