35-5 Exploring Handheld LIBS Calibration Techniques for Use with Igneous Rocks

Session: Minerals in Motion: Tracking Mineral Reactions Using In Situ and Synchrotron Techniques, A Celebration of the Career of Peter Heaney (Posters)

Presenting Author:

Authors:

Abstract:

Handheld laser-induced breakdown spectroscopy (LIBS) is a portable technique that uses laser ablation combined with an internal spectrometer and calibrated regression model to provide the geochemistry of a sample in a matter of seconds. However, a challenge for the community is that LIBS often performs poorly with rocks of heterogeneous textures, such as porphyritic igneous rocks [1,2]. This study aims to improve our ability to use LIBS on igneous rocks to measure their chemistry by testing the reliability of multiple calibration models, including using whole rock and the traditional pressed pellets [1]. Ten rock samples of differing composition and texture (rhyolitic tuff to granodiorite) from the McDermitt Caldera (Nevada, USA) were used for this study, where whole rock geochemical data was collected for each sample. Calibration models were created in the Sci Aps Profile Builder software, where an intensity ratio must be prepared by the user for each element. These intensity ratios are then paired with the known LA-ICP-MS geochemistry and spectra acquired from either a whole rock or its associated pellet. Six rock samples, both as a pellet and the cut rock face, were used for calibration. The other four were then used as unknowns to test the accuracy of whole rock calibrated scans against pellet calibrated scans. Preliminary results suggest that the whole rock calibrated scans overall perform better, but vary by element, where lower concentrations generally perform better than higher. Additionally, thirty scans per sample was shown to be insufficient for good calibration validation, yielding an average R2 of 0.6. Prior research suggests that up to 560 scans per sample may be required [2]. These results suggest that whole rock calibrations should be applied  when measuring unprocessed rock geochemistry. Future investigations need to target improving the construction of intensity ratios and the number of scans required for the best accuracy for each element.

[1] Yan et al. (2025). Journal of Analytical Atomic Spectrometry.

[2] Fontana et al. (2023). Journal of Geochemical Exploration, 246.

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

doi: 10.1130/abs/2025AM-10393

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