In the Puna region, located in the NW portion of Argentina all the salar basins have been evolved along the time since the early Quaternary. The brine in each basin has a specific geochemical signature, which is the consequence of the interaction of several factors (temperature, pH) or natural process (weathering). The brine hosted in the deep or shallow aquifers, has some constant ratios among the main ions, which in some cases are key due to their impact on the LCE production cost (Mg, SO4, Cl, As, Fe, etc). In addition, the Li7 isotope contents should be considered as other main feature due to the linking with the evaporation evolution rates and the brine residence time. A combination of the geochemical analysis and Li7 contents would allow to understand the evaporation history and what could be the main lithium source. Conceptually, the brine residence time is very important and a key element that needs to be defined because there is a very straight correlation with the lithium grades.