LITHOLOGIC DIVERSITY WITHIN LUNAR REGOLITH BRECCIA METEORITE NORTHWEST AFRICA 8783: CLASTS 3 AND 6

In this study we aim to better understand the diversity of lithologies on the Moon through the examination and classification of lithologic clasts within a lunar regolith breccia meteorite. Northwest Africa (NWA) 8783 is a lunar regolith breccia collected in 2014, and is composed of a variety of mineral and lithologic clasts set in a dark, fine-grained matrix that is cross-cut by several impact glass veins. Very little work has been conducted on this sample, thus this abstract represents a portion of a larger study (see companion abstracts) that is the first to examine the sample in detail through several clasts. One thin-section of NWA 8783 was examined using a petrographic microscope to select representative lithologic clasts for further analysis. Preliminary mineral chemistry data (major and minor elements) from the selected clasts were collected using the Cameca SX 100 electron microprobe (EMP) at the University of Tennessee, Knoxville. This abstract will discuss two of the lithologic clasts, Clast 3 and Clast 6, whereas the other clasts are discussed in two companion abstracts (see Hall et al., and Recchuiti et al., this conference). Clast 3 (450 µm) is composed of olivine (avg. Fo 70.0), pyroxene (En77.4 Fs19.5 Wo3.1), and plagioclase (An 90.9). Clast 6 (600 µm) is composed of olivine (avg Fo80.1), pyroxene (Wo5.2 En68.6 Fs 26.2), and plagioclase (An 95.8). Additional chemical data will be collected, as well as additional X-Ray and BSE images for modal mineralogy calculations, but preliminary mineral chemistry can be used to suggest potential classifications for the clasts. Clast 3 is compositionally similar to lunar Mg-suite rocks (e.g., An 90.9 and Mg# of mafic minerals ~70-83). Clast 6 is compositionally similar to lunar Mg-suite rocks or ferroan anorthosites (FANs), as it lies in a compositional gap between the two (An 95.6 and Mg# of mafic minerals ~72-82). However, although these clasts have some chemical similarities to lunar compositional suites, further analyses are needed to confirm these preliminary classifications, as well as the addition of detailed modal mineralogies.