Where does the Lithium come from to enrich brines in closed basins?

HICKSON, C.; COIRA, B.L.; COOLBAUGH, M.

Washington

Congreso; American Exploration & Mining Association 124th Annual Meeting; 2018

American Exploration & Mining Association

Exploration for economic deposits of lithium brine in areas of the world that contain high elevation internally drained (closed basins) with rapid evaporation rates continues. Numerous companies have entered the race to identify deposits outside of the known production areas such as the Atacama region of Chile and Clayton Valley in Nevada, USA. Identifying brines outside of Clayton Valley in Nevada remains elusive, but at least two companies have started to focus on the fine grained claystones that are found in several valleys, while others continue to explore for a brine-based resource. In general, lithium brine deposits are pre-request on a set of geological and climatological factors: 1) a source of lithium, 2) an extraction mechanism, 3) a transport mechanism, 4) a trap (closed basin), 5) a suitable solar evaporation rate, and 6) scale (mass flux of lithium and limited dissolved salt competition). Geothermal fluids may contribute to more efficient and selective extraction of lithium from basin sediments and basement rocks; they may help transport the enriched fluids due to thermal upwelling; and finally provide long term mass flux that over sufficient time leads to significant endowment in basins. The basins of western Nevada have many of these prerequisites, but are dominated by clastic sediments and have relatively high subsidence and sedimentation rates. For these reasons it is likely that lithium-enriched brines are deeper than in the mature basins of South America. Since few basins in Nevada have had deep drilling, paleo-brines may remain to be discovered at depths not yet investigated by exploration companies. In Argentina?s western Puna area, Salinas Grandes mirrors the high value Lithium concentrations found in the Atacama Salar of Chile. Intervening basins tend to have lower Lithium and higher Magnesiumvalues than these large flanking basins. Salinas Grandes has been shown to have Lithium values up to 3,000 mg/l. It has strong inflow from the Las Burras river which drains and extensive geothermal area. Li concentrations in the river have been reported at 3.75 mg/l. Additionally, the basin has significant fine-grained volcanic ash deposits as well as being underlain by Ordovician rocks that have Lithium values. Lithium bearing micas have been found within the clastic sediments. The variability in lithium endowment between basins in South America, and specifically Salinas Grandes, is likely related to the first three factors listed above ? source, extraction and transport, with additional variability related to the robustness of the geothermal systems in the various basins.