Lithium exploration on the eastern Puna plateau (23°-24°S).

CÓRDOBA, F.; LÓPEZ STEINMETZ, R.; GARCÍA, G.

San Salvador de Jujuy

Workshop; Proceedings 3rd International Workshop on Lithium, Industrial Minerals and Energy (IWLiME 2016).; 2016

Universidad de Jujuy

The study area involves the Guayatayoc Basin, an endorheic basin with a surface of ~ 17000 km2. The low lying area (3400 m a. s. l.) of this basin includes a ~400 km² playa lake system. The western catchment area corresponds to the Las Burras Sub-basin, which involves the Coranzuli and Pastos Chicos Rivers. Data obtained previously by our group in the study area have allowed 1) to propose a chronological and evolutionary based model for the sedimentary basin, and 2) to assess the timing of endorheic drainage onset. The exploration of ionic facies in the Guayatayoc Basin was assessed by hydrochemical determinations of residual brines and feed waters. Residual brines from the playa lake contain up to 125 mg/l of lithium, and the Las Burras River supplies the most concentrated lithium (3.75 mg/l) inflows of the basin. Our team is currently involved in in-depth investigations aimed to unravel the lithium cycle, from its mobilization at the source to its storage in the final depositional site in brine-type salar reservoirs. XRD analyses and ongoing ICP-MS determinations of playa lake sediments would be indicating the presence of rare lithium micas, which represent the first occurrence of rare lithium micas in an Andean salar. These Li-micas include taenolite and eucryptite, two igneous minerals that suggest a clastic supply from the intrusive rocks exposed along the western side of the basin. Preliminary results obtained from water samples collected in the three main tributary rivers of the western Guayatayoc Basin, revealed an additional interesting feature. The lithium concentration appears to stay constant through the catchment area (e.g., 1.93 mg/l of Li+ near the source of the Coranzuli River and 1.97 mg/l downstream, in the Las Burras River). This raises the question ? which we consider a new working hypothesis in our on-going investigation ? does Li+ have a near-conservative behaviour in natural systems, i.e., before reaching the salar?