FUENTES DE LITIO EN LOS SALARES DE JAMA Y MUCAR, PUNA NORTE. ESTUDIO ISOTÓPICO DE Li Y Sr

SARCHI, C.; MEIXNER, A.; LUCASSEN, F.; CAFFE, P.J.; BECCHIO, R.; KASEMANN, S.

Congreso; XIII Congreso de Mineralogía Petrología Ignea Y Metamórfica Y Metalogénesis XIII MINMET- IV PIMMA; 2019

Jama and Mucar salars (northern Puna) are two high-altitude endorheic basins containing anomalous Li-rich brines. In this work we study both salars, separated by a range of Ordovician sedimentary rocks with the aim of understanding the source of Li. For this, we obtained Li and Sr isotopic ratios from rocks, brines, salts and river waters, as Li isotopes reflect low T fractionation processes, and Sr ratios work as a continental weathering tracer which reflect the potential source rock compositions. As shown by 87Sr/86Sr ratios of brines/water and salts samples (0.70 ? 0.71) that overlap the range of Cenozoic volcanic rocks, a clear contribution of the latter to the runoffs collected by these endorheic basins is recognized. Sedimentary Ordovician rocks seem to be of minor importance. The difference in Li concentration observed for salt (average value of 862 μg/g) and brine/water samples (average value of 126 mg/L) is related to brine evaporation processes. As the δ7Li remains the same, we conclude that no fractionation of Li occurs during halite crystallization. However, during weathering a preferential fractionation of 7Li into the solute occurs, leaving a silicate phase enriched in 6Li (salar sediments).