231-7 Handheld LIBS as a Fast, Eco-Friendly, and Low-Cost Tool to Evaluate Lithium Distribution in Native Tropical to Subtropical Topsoils From Minas Gerais State, Brazil

Session: Critical Mineral Resources and Recovery in the Americas: Emerging Methods in Exploration and Sustainable Extraction (Posters)

Poster Booth No.: 277

Presenting Author:

Marcela Vieira da Costa

Authors:

Vieira da Costa, Marcela¹, Lelis Leal de Souza, José João², Granate Sá e Melo Marques, João José³, Benson, Thomas R.⁴, Guimarães Guilherme, Luiz Roberto⁵, Chappaz, Anthony⁶, Teixeira Ribeiro, Bruno⁷, Sirbescu, Mona C.⁸

Abstract:

Global demand for lithium (Li) is exponentially increasing, primarily due to its critical role in batteries powering the transition to low-carbon energy industries. However, Li has also emerged as a potential environmental contaminant, especially due to improper management of battery waste or extractive industry. Therefore, developing effective methods to monitor background Li concentrations in soils with minimal anthropogenic influence is crucial for both environmental monitoring and mineral exploration.

This study aims to develop new calibration models using a handheld laser-induced breakdown spectroscopy (LIBS) device to quantify Li, K, and Rb concentrations in highly-weathered topsoils from Minas Gerais (MG), a state with significant Li reserves. A total of 27 NIST, OREAS, NRC, and USGS certified reference materials (CRMs) with Li concentrations ranging from 3 to 130 mg kg^-1, were selected based on their chemical similarity to tropical soils. The CRMs were pelletized and used to calibrate LIBS. The calibrations were applied to 200 pelletized topsoil samples from a MG state-wide legacy soil collection, with minimal anthropogenic activity. A subset of the samples (n = 8) was also analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to validate LIBS performance. Additionally, an interpolated map of Li concentrations obtained by LIBS was generated and compared with Brazilian Geological Survey (SGB) soil Li distribution maps, including Li mining districts.

The calibration RMSEs for Li, K, and Rb were 7, 4475, and 18 mg kg^-1, respectively. Li concentrations measured by LIBS ranged from 1.8 to 206 mg kg^-1, significantly expanding the detectable range for LIBS compared to prior studies, which focused mainly on temperate soils with Li concentrations ≥ 50 mg kg^-1. Strong correlations between LIBS and ICP-MS were observed, with R² values of 0.76, 0.96, and 0.85 for Li, K, and Rb, respectively. Moreover, anticipated geochemical trends were followed: Li and Rb correlated positively, while Li correlated negatively with the K/Rb ratio. Interpolated LIBS map also showed strong spatial agreement with SGB-reported soil Li data and known Li deposits across Minas Gerais. These findings highlight the potential of handheld LIBS equipped with a matrix-matched calibration as a rapid, cost-effective tool to map Li concentrations as low as a few mg kg^-1, and to identify anomalous areas, relevant to environmental monitoring and exploration surveys, in tropical to sub-tropical soils.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8770

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