NWA 18482 (Lunar) - MAIN MASS

Petrography: The meteorite exhibits a coarse-grained breccia texture, dominated by mm-size clasts surrounded by a dark, partially recrystallized glassy matrix scattered with rare vesicles. Most of analysed clastic fragments have a felspathic composition. Within the feldspathic clasts and dispersed in the glassy matrix there are mafic mineral clasts (olivines and pyroxenes) with both FAN and Mg-suite affinity. Pyroxenes with FAN affinity, differently from those with Mg-suite affinity, are finely exsolved. Minor phases detected are oxides with variable composition, FeNi metallic alloy, ilmenite and silica polymorph. Ba-sulphate thin veins are also found filling small cracks and vesicles.

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Mineral Chemistry (EMPA analyses): Olivine with FAN affinity: Fa47.3±15.2 (Fa38.3-83.3, N = 14), olivine with Mg-suite affinity: Fa15.2±2.1 (Fa10.3-20.6, N = 20) (overall FeO/MnO= 89.9±17.5, N = 34)

Low-Ca pyroxene with FAN affinity En33.8-59.0Fs38.2-61.6Wo1.7-5.3 (Mg# = 23.8-46.8, N = 17), low-Ca pyroxene with Mg-suite affinity En77.0-90.5Fs9.1-18.8Wo0.4-4.2 (Mg# = 70.1-83.5, N = 14)

High-Ca pyroxene with FAN affinity En29.9-55.2Fs16.0-58.7Wo6.4-40.9 (Mg# = 22.7-60.8, N = 25), high-Ca pyroxene with Mg-suite affinity En48.4-58.1Fs5.1-9.5Wo34.1-43.3 (Mg# = 74.4-85.6, N = 11)

Plagioclase An95.5-98.3Ab1.5-4.4Or0.0-0.4 (mean An = 96.4±0.6 mol%, N = 36)

Oxides with chromite-rich composition (atomic ratio Cr# = 70.1-79.7, Mg# = 11.0-22.5)

FeNi metallic is kamacite with Ni = 6.0-7.3 wt% (N=3).

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Weathering: Low

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Classification: Lunar Feldspathic melt breccia