A HYDROGEOCHEMICAL COMPARISON OF A POTENTIAL LITHIUM BRINE RESOURCE AT DASHT-E-NAWAR, AFGHANISTAN, TO THE LITHIUM BRINE RESOURCE AT CLAYTON VALLEY, NEVADA

The continental, basin brine in Clayton Valley (CV) NV was among the first in the U.S. to be mined for lithium (Li). As a result, CV provides a conceptual deposit model for Li brine resources. A recently published model for Li brine resources suggests they share 6 characteristics: 1) arid climate; 2) closed basin with a salar, and/or salt lake; 3) associated igneous and/or geothermal activity; (4) tectonically driven basin subsidence; (5) a lithium source(s); and 6) sufficient time to concentrate brine.

The Dasht-e-Nawar (DeN) basin in Afghanistan, a volcanic collapse feature at 3115 m elevation, displays most of these characteristics and was a target for Li brine exploration in 2014. DeN basin has dry hot summers and cold winters. An evaporative lake forms on the playa from spring snowmelt and dries by fall. Thermal waters have been reported along its western and southern edges.

In 2014, DeN lake waters and shallow porewaters (1.5m depth) were reported to have ionic strengths of 0.08 and 0.35M, respectively, and Li concentrations of 0.20 and 0.20-0.38 ppm, respectively. Six boreholes were spatially located across the DeN playa, drilled to depths ranging from 45 to 109m, and porewaters were collected every 9m. Analysis of borehole 1, 96m depth total, showed ionic strength and Li concentrations of 0.08M and 76 ppb, respectively, at 4.4m depth. With increasing depth the porewaters became less concentrated, decreasing to an ionic strength of 0.007M at 90m. Li, however, remained fairly constant with depth and increased slightly to 96 ppb at 90m. In contrast, brines in CV are ~3.5M ionic strength and ~230 ppm Li.

Mixing calculations for DeN suggest fresh groundwater diluted the brine over time. We hypothesize that the DeN basin is open to groundwater flow, and despite an apparent similarity with CV, hydrologic conditions were not favorable for formation of a lithium brine.