From the origin to the mature stage of salt flats: implications for the extreme Li-enrichment of its interstitial brines
Abstract
The 40% of the worldwide Lithium (Li) used for the development of mobile phone and electric car batteries, as well as in the pharmacological industry, is extracted from the brine that fills the pores and cavities of salt flats (salars). Additionally, the brines of salt flats content 80% of the world's Li-reserves. However, the origin of the extreme Li-enrichment of these brines is still unknown.
The thick accumulation of salts and its associated brines in salt flats results from the groundwater discharge near the land surface by phreatic evaporation for thousands to millions of years. The strong evaporation contributes the enrichment in major cations and anions as well as other rare elements (e.g. Li, B, Ba, Sr, Br, I and F) which are very attractive for mining exploitation. However, only evaporation cannot explain by itself the extreme concentrations of some of these elements that are reached in the brines considering the present-day inflows geochemistry. Several alternative hypotheses have been proposed to explain the extreme Li-enrichment of the salt flat brines although none of them has been able probed neither endorsed by a numerical model till the date: (1) leaching of water-soluble salts from the surrounding volcanic rocks and hypothetical ancient salt flats buried between them, (2) leaching of Li-rich clays and (3) hydrothermal activity associated with faults. The lack in numerical models that have allowed to validate these hypotheses and to explain the origin and evolution of salt flats has been favoured by the difficulty and high computational cost of reproduce the evaporation process joint to the strong hydro-thermo-haline coupling and its dependency on density and viscosity. The goal of this work is to modelling the evolution of the Salar de Atacama, the highest Li-concentration in the world, from its origin to its mature stage considering the presence of faults to explain present brine geochemistry.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR11C0060M
- Keywords:
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- 1805 Computational hydrology;
- HYDROLOGY;
- 1822 Geomechanics;
- HYDROLOGY;
- 1858 Rocks: chemical properties;
- HYDROLOGY;
- 1859 Rocks: physical properties;
- HYDROLOGY