T200 Sedimentary Basins I

Tuesday, 3 November 2015
8:00 AM - 12:00 PM
Room 349/350

LITHIUM BRINE EXPLORATION AT DASHT-E-NAWAR BASIN, AFGHANISTAN

Paper number: T200-13
Program: Technical Sessions
Time: 10:50 AM – 11:05 AM

Authors

Abstract

In 2014 the playa of the Dasht-e-Nawar basin was investigated for the presence of lithium brine. The basin is located in Ghazni Province, east-central Afghanistan, and contains andesite and rhyodacite tuffs, and cinder cones which are remnants of the Early Pleistocene-aged Dashtinovar Series that once covered the region. A seasonal evaporative lake occupies the center of the basin and basin fill is comprised of Holocene-aged playa sediments. The basin is bounded by faults which create a closed structure. It was hypothesized that hydrothermal waters, heated by remnants of the volcanic system, leached lithium from the volcanics which was then concentrated, over time, in pore waters of the basin to form a lithium brine.

The U.S. Department of Defense Task Force for Business and Stability Operations (TFBSO) managed the exploration activities. The U.S. Geological Survey (USGS) collaborated with the TFBSO by providing analysis of Landsat imagery to assist field data collection; oversight of passive seismic data collection and analysis; and an independent analysis of the chemistry and mineralogy of the subsurface samples.

Six boreholes were drilled in the dry lake surface of Dasht-e-Nawar basin. A total of 406 m of sediment core was collected, along with 44 pore-water samples. The longest core was 109 m; the shortest 45 m. Field measurements of the pore waters were collected for pH (7.89-9.40) and conductivity (299-7799 µS/cm). Major cation concentrations in the pore waters were Na (3–1440 mg/L) > Mg (12.1–267 mg/L) > Ca (7.2–79.6 mg/L) > K (<0.05–59.9 mg/L). Lithium ranged from <50 to 227 μg/L and did not show a consistent pattern with either borehole location or sample depth.

Interpretation of the passive seismic survey suggests that the maximum sediment thickness at the north of the basin is 107 m, and in the south it is 173 m. While the boreholes did not penetrate to the basin floor, the low Li concentrations and low conductivity values in pore waters do not suggest the presence of a viable Li brine resource at Dasht-e-Nawar.