T208 Lithium Clays, Brines and Pegmatites in the Americas: Challenges of a Critical Metal for the Energy Transition

Tuesday, 24 September 2024
1:30 PM - 5:30 PM
207C

BEST PRACTICES IN LITHIUM BRINE EXPLORATION: A CASE STUDY OF THE PASTOS GRANDES DEPOSIT, ARGENTINA

Paper number: T208-10
Program: Technical Sessions
Time: 3:35 PM – 3:50 PM

Authors

Abstract

Exploration for lithium brine resources in the high Andes of South America is typically limited to multi-million-dollar drilling campaigns and high-cost geophysical surveys. While these exploration tools are essential for defining Mineral Resources, the high costs make them risky enterprises, especially when dealing with deep (>500 m) brines in faulted basins. Using the Pastos Grandes Basin (Salta, Argentina) as a case study, we show how relatively low-cost traditional geological analytical techniques performed in conjunction with drilling and geophysics decreases risk and improves production drilling accuracy at minimal cost. Lithium Argentina Corporation led the effort, advised and assisted by a multi-disciplinary team across several academic institutions in the Americas. We performed 1:90,000 geological mapping of the ~10x15 km basin to define the major stratigraphic units in the region and the location of key thrust faults that project into the subsurface and define the topography of the basement. Detailed logging of the sediment core delineates the lateral and vertical extents of key brine reservoirs and establishes volcanic marker beds. Samples of the marker beds from the core are correlated with the regional stratigraphy via whole-rock geochemistry (XRF, ICPMS) and ash shard geochemistry (EMPA). U/Pb zircon geochronology and Ar/Ar feldspar geochronology on a subset of the volcanic samples from outcrop and core define the age and geometry of the basin and correlate contemporaneous alluvial to lacustrine sedimentary facies. Results indicate that halite bodies are thickest (>700 m) adjacent to large thrust faults and began precipitating – thereby enriching the residual brine in lithium – about three million years ago, approximately double the amount of accumulation and enrichment time than previously thought. Reinterpretation of drilling and geophysical data conceptualize these results in a more accurate geological framework that can be used to improve the definition of Mineral Resources and help guide lithium brine production well drilling for traditional brine operations and govern reinjection strategies required for direct lithium extraction (DLE) techniques.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-404923

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