11-10 Investigating the Moon’s Geological History via Petrological Analysis of a Meteoritic Polymict Regolith Basaltic Breccia

Session: Applications of Igneous Petrology, Geochemistry, and Geochronology to Understanding Earth and Other Planetary Systems (Posters)

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Decades of lunar exploration and sample-return missions underpin our understanding of the Moon’s geological evolution from early differentiation, to serial magmatism, later volcanism, and impacts. Lunar meteorites, likely sourced from regions not sampled by surface missions, can provide a broader sampling of lithologies, and therefore, have the potential to yield new insights into the Moon’s history. The 2018-2019 Antarctic Search for Meteorites (ANSMET) season returned 8 polymict basaltic lunar regolith breccias from the Dominion Range (DOM) in the Transantarctic Mountains. This study focuses on sample DOM 18262. Through a detailed textural, mineralogical, and geochemical investigation the history of basaltic magmatism on the Moon will be assessed, and potential basaltic source provinces on the lunar surface will be evaluated. Sample DOM 18262 is the second smallest of the suite at 6.78g. The studied thin section of this study measures 1.6cm by 1.1cm. Characterization via SEM-EDS reveals a clast-poor (<10%) breccia, dominated by a glassy matrix where clast and mineral fragments are surrounded by glass spherules (up to 600µm), melt pockets, and melt veins. The clast population primarily consists of basalts, impact melt breccias, microbreccias, and 3-phase symplectites. ~80% of the section is surrounded by a glassy, variably vesiculated fusion crust with vesicles ranging from <0.1mm to 0.2mm. In places, fusion crust textures also resemble those of lunar agglutinates. Major mineral fragments are euhedral to subhedral. These include clinopyroxene, anorthitic plagioclase, fayalitic olivine, and ilmenite. Troilite, apatite, and silica exist as minor minerals while spinel, alkali feldspar, and iron oxide phases are rare. Clinopyroxenes and anorthitic plagioclases are often compositionally zoned with clinopyroxenes also exhibiting fine-scale (<5µm) exsolution lamellae. Subsequent analyses via Electron Probe MicroAnalysis (EPMA) will quantify the chemical composition of the major and minor phases identified via SEM-EDS. Chemical data will be used to evaluate potential basaltic provenance (e.g., low vs. high Ti terranes via Fe# vs. Ti# in clinopyroxenes) and the potential contribution from FAN-materials to breccia petrogenesis (e.g., plagioclase An# vs. pyroxene Mg#). Collectively, data will be used to evaluate the origin of DOM 18262 through comparison to other known basaltic lunar suites from meteoritic and returned collections in order to advance understanding of the Moon’s geological evolution.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

doi: 10.1130/abs/2026SE-12837

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