Lithium and brine geochemistry in the salars of the Southern Puna, Andean plateau of Argentina

Abstract

The Andean plateau is a small region of South America extending between northwest Argentina, southwest Bolivia and northern Chile. It concentrates the largest global resources of lithium brines in its numerous salars. Of these, the giant salars in Bolivia and Chile have been relatively well studied, however, only little is known about the smaller, but numerous salars in the Argentine Puna region. In this article, we present the results of the first regional-scale reconnaissance exploration of the twelve major salars situated in the southern part of the Puna plateau (24°S - 26°30?S). Hydrochemical data indicate that shallowest brines are characterized by highly variable Li concentrations, with mean Li grades ranging between 57 and 570 mg L-1, and mean Li:Mg ratios from 0.01 to 1.24. A survey of the brine chemistry of the salars across the Puna plateau, including its northern part, has revealed the absence of geographical pattern in Li+ grade distribution. However, a comparison among mean Li+ grades, Li+:Mg2+ ratios, and the size of all salars allows an estimation of their Li mining potential. Specifically, the salt pan of Arizaro represents the high potential mainly due to its size; Antofalla-Botijuelas has a large surface and promising Li:Mg ratios for Li recovering via brine evaporation, though its elongated shape is a constraint; Pastos Grandes, Pozuelos, and Rincón have encouraging Li grades, interesting salar sizes, and relatively easy access. Olaroz, Cauchari, and Hombre Muerto contain the highest Li+ grades in brines of all of the Argentine Puna, and embody the most interesting perspectives of the Argentine plateau and in a regional context. Salar sizes could be related to maximum Li+ grade of brines. Larger salars would be then expected to contain higher Li+ grade brines than smaller ones, which could be considered as a useful criterion for surveys of brine type deposits.