Lithium resource mapping in Afghanistan's Helmand Basin: A multi-criteria approach of zonation using the Analytic Hierarchy Process

The Helmand Basin, which spans southern Afghanistan and parts of Iran and Pakistan, is a hyperarid, endorheic region with a high potential for lithium-brine (Li-brine) deposits. Although lithium is available in nature as a primary source (for instance, granite pegmatite type) and as a secondary source of deposition in salt lakes or palaeo-salars in the subsurface, a generalised methodology for adopting a priority-based lithium exploration policy is still absent. This study, driven by a heuristic approach, specifically explores the Helmand basin's tectonic complexity, as well as its climatic and geological conditions, which make it a promising target for Li-brine exploration. By utilising the Analytic Hierarchy Process (AHP), we systematically identified potential Li-source and accumulation zones by parameterising key factors such as hydrothermal activity, Li-rich lithology, crustal thickness, arid climate, and tectonic subsidence. The spatial zonation model developed in this study predicts areas with varying probabilities for Li-brine systems, highlighting the northeastern basin as the most promising for Li sources. Specific recharge and transport pathways were identified, mapping Li migration from source zones to high-elevation lakes, including Ab-e Istada and Dasht-e Nawar. Additionally, the Godzareh Depression emerged as a significant Li-brine accumulation site, benefiting from regional recharge throughout the entire basin. This study demonstrates the utility of AHP in integrating complex geospatial data for precise Li-brine exploration. The results provide a strategic framework for guiding economically viable lithium resource development, positioning the Helmand Basin as a key contributor to the global Li-brine supply.