Unveiling mineral phase distribution in the Chelyabinsk LL chondrite using LIBS mapping and cluster analysis

Abstract

The Chelyabinsk meteorite was analyzed using Laser-Induced Breakdown Spectroscopy (LIBS) combined with Raman spectroscopy to characterize chemical and mineralogical heterogeneity across its inner matrix, fusion crust, and metallic inclusions. LIBS spectra acquired at selected points revealed major elements including Fe, Mg, Si, Al, Ca, Cr, Mn, Na, and Ni. Relative intensity ratios normalized to Fe confirmed a higher abundance of rock-forming silicates in the inner matrix, Fe-rich metallic inclusions, and intermediate compositions in the fusion crust. High-resolution LIBS mapping (100 µm) visualized the spatial distribution of mineral phases, with Na + Ca highlighting plagioclase, Fe + Mg olivine and pyroxene, Cr chromite, and Fe + Ni metallic phases. K-means clustering integrated the elemental maps into a single classification, clearly distinguishing five mineral phases. Calibration-Free LIBS (CF-LIBS) was applied at strategically selected points to determine semi-quantitative elemental compositions. A ternary diagram based on the CF-LIBS-derived oxide percentages (FeO–MgO–SiO₂) confirmed the classification of Chelyabinsk as an LL-type ordinary chondrite. This workflow demonstrates that LIBS mapping combined with clustering and CF-LIBS allows rapid, minimally invasive assessment of meteorite heterogeneity, mineral distribution, and classification, providing detailed microscale compositional information while preserving the integrity of rare samples.