Monitoring geochemistry of the evolution of natural system: salar de Huasco (Chile)

Abstract

Evaporation process affecting brines in salar of Huasco (Chile) has been reproduced at laboratory scale with the main objective of studying its geochemical evolving path. Natural brines have been evaporated under isothermal conditions, precipitating progressively calcite, gypsum, thenardite, and halite. This mineral sequence confirms the evolution of equilibrium conditions calculated by means of PHRQPITZ geochemical code. Geochemical modeling has allowed to determine that saline minerals reach saturation along the experiment performed at different evolutive moments that they do in natural conditions. This fact is due to two main causes, first to the interaction between dilute solutions entering salar with the external saline rim mainly composed of gypsum, whose solubilization causes that brines reach faster saturation respect to gypsum in the natural system compared to experiments in laboratory; and second, to precipitation of mirabilite as consequence of thermal oscillations to daily scale causing that halite equilibrium is reached for higher brine concentrations in salar that in laboratory, since mirabilite precipitation produces a significant depletion of sodium concentration in brines.

Keywords

• Huasco salar's
• evaporation
• geochemistry
• natural brines
• PHRQPITZ
• saturation