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Abstract
We report the petrographic and geochemical characteristics of three unequilibrated ordinary chondrites recently recovered in the Atacama Desert near Antofagasta, Chile: San Juan 126 (H3.1), San Juan 127 (L3.2), and San Juan 128 (LL3.1). Thin section analyses reveal well-preserved chondrules with average diameters ranging from 340 ± 90 µm to 715 ± 180 µm. Primary igneous glass is present in chondrule mesostases, and matrices are largely opaque. Electron microprobe analyses indicate olivine compositions of Fa₁₇.₄ ± 8.9 (H), Fa₁₉.₅ ± 6.3 (L), and Fa₂₀.₉ ± 12.7 (LL), and low-Ca pyroxene compositions of Fs₁₀.₅ ± 4.3, Fs₁₆.₉ ± 7.5, and Fs₁₂.₉ ± 7.6, respectively. Cr₂O₃ concentrations in olivine range from 0.05 to 0.13 wt%. These values, along with chondrule textures and glass preservation, support assignment to low subtypes H3.1, L3.2, and LL3.1, respectively. This study enhances the current inventory of primitive ordinary chondrites and provides further constraints on thermal metamorphism in the early solar system.
