Lithium isotopic geochemistry and georesources: recent applications and future direction
Résumé
The fascinating growth in clean and renewable energies to every corner of the world is essential for the global sustainability. Research on Li-brine deposits and pegmatites is challenged by defining Li concentration, its origins and enrichment processes in order to develop innovative exploration tools. Lithium (6Li ~ 7.5% and 7Li ~ 92.5%) is a fluid-mobile element and, due to the large relative mass difference between its two stable isotopes, it is subject to significant low and high temperature mass fractionation which could provide key information on the nature and formation of Li-rich brines and adding information about basin history and the natural Li enrichment process. In the present study, we first analyzed and compared stable isotopic compositions from 4 Argentinean Li rich salars. The Pozuelos, Centenario, Ratones and Hombre Muerto belong to the world-class brine resources of the “lithium triangle”. Our results show that the dominant source of Li is related to water/rock interactions (surface, saline waters with andesites, pegmatites, pyroclastics). Second, we report Li isotopic compositions from the Monts d'Ambazac Pegmatite Field (French Massif Central). The process of partial melting of protoliths enriched in earth rare-element bearing phases (mica & garnet) seems to be more responsible for Li-isotope fractionation than Li-diffusion or fractional crystallization at the temperature of pegmatite consolidation.