Application of Handheld LIBS to Quantitative Analysis of Carbonate Minerals

Presented at International Online Meeting on Laser Induced Breakdown Spectroscopy (IOMLIBS), July 2020.

‍Authors: Yonghwi Kim, University of Lorraine; Cécile Fabre, University of Lorraine; Jean Cauzid, University of Lorraine

Handheld LIBS is effectively applicable for in-field determination of carbonates and quantifying carbonate mixtures. The study achieved accurate results with limited sample pre-treatment and faster analyses than other conventional techniques.

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Abstract: Handheld Laser-induced breakdown spectroscopy (LIBS) device is able to perform real-time determination in the field with limited sample pre-treatment of permitting accurate, and faster analyses than the other conventional techniques. In this study, natural carbonate standards of calcite structure were analysed to investigate the spectral applicability for both mineral discrimination and quantitative analysis in Ca-Mg-Fe-Mn carbonate system. Carbonate minerals are formed by the combination of (CO3)2- ion with various monovalent or divalent cations, and the target minerals in this study are rhombohedral carbonates such as calcite (CaCO3), magnesite (MgCO3), siderite (FeCO3), rhodochrosite (MnCO3), dolomite (CaMg[CO3]2) and ankerite (Ca[Fe,Mg,Mn][CO3]2). LIBS intensity and peak area from several peak candidates were compared with each elemental content such as Ca, Mg, Fe and Mn determined by portable X-Ray Fluorescence (pXRF) in order to investigate the highest correlation with the chemical composition. LIBS data were averaged over 5 randomly chosen locations on each pressed pellet. Each location was measured with a 15 points square-grid, and each point consists of 4 successive LIBS analyses except for the first cleaning shot. Both the intensity and peak area display a positive linear trend with the elemental concentrations, with a regression coefficient (R2) greater than 0.96 except for Mg. This result can be explained that pXRF analysis is difficult to detect light elements quantitatively while LIBS can retrieve chemical information from the light elements. Synthetic mixtures of calcite-dolomite, calcite-ankerite and ankerite-dolomite were used to assess the quantitative relationship between the spectral ratios and the mineral volumes in the two-component systems. We confirmed that Mg/Ca ratio is highly correlated with the calcite-dolomite and calcite-ankerite mixtures, while Fe/Ca ratio shows a distinct trend on the calcite-ankerite and ankerite-dolomite mixtures. The results of this study demonstrate that LIBS is effectively applicable to the determination of carbonates and quantification of the carbonate mixtures.

‍Access to presentation: https://www.researchgate.net/publication/342946409_Application_of_handheld_laser-induced_breakdown_spectroscopy_LIBS_to_quantitative_analysis_of_carbonate_minerals

‍About this conference: IOM-LIBS 2020 brought together scientists working on LIBS to discuss recent research and applications in an online forum in an effort to continue scientific communication during the coronavirus pandemic.

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