An Earth Observation based workflow for tracking lithium movements in the Salar de Uyuni region, Bolivia

Abstract:

The increasing global effort to overcome the reliance on fossil fuels is driving the demand for ‘green’ metals such as lithium. This study aims to develop a seamless and repeatable workflow to track the mass of lithium as it moves from its bedrock source in the watershed surrounding South American salt flats (“salars”) to the nucleus of the salar itself where it is concentrated in Li-rich brines. The area of interest is in and around the Salar de Uyuni, Bolivia, the largest salar in the world. We aim to create a watershed-scale to salar-scale understanding of how Li brine deposits develop, where the water and solute comes from, how the brines are created and how abstraction affects the mass balance within the salar. For this research, open source Earth observation (EO) data, i.e. multi/hyperspectral and Synthetic Aperture Radar (SAR) data, is analysed to support the development of robust geological and hydrogeological conceptual models, and numerical groundwater simulations. We explore the potentials of EO data for several research aspects, such as (1) Jointing: it may influence fracture-flow of groundwater and also be significant in terms of surface-area for water-rock interaction, i.e. potentially increasing the ‘leaching’ rates of Li from the bedrock into the water; (2) Weathering: the degree and style of weathering may influence the liberation of Li from rocks into the water; (3) Distribution of clays: the distribution of clays that may restrict the liberation of Li from weathered rock, or may scavenge Li from passing water; (4) Water and moisture: the distribution of water-bodies and sources, including active streams, springs etc.; (5) Geological structure: the presence of neotectonic faults that may disrupt the salar, as well as structures that may provide pathways for the flow of fluids; (6) Lithological mapping and classification: possible refinement of existing geological maps. This workflow will support quantifying the resources of lithium and sustainable extraction in the region.