Insights into the Petrogenesis of Lunar Basaltic Breccia Dominion Range (DOM) 18666

The Moon preserves an extensive record of the geological processes which have shaped the evolution of planetary surfaces over billions of years. This work focuses on characterizing the mineralogies, textures, and chemistries of a brecciated lunar basaltic meteorite that was returned from the Dominion Range (DOM), Antarctica, during the 2018 Antarctic Search for Meteorites expedition: sample DOM 18666. Initial phase identification, textural observations, and elemental mapping is being conducted via Polarized Light Microscopy (PLM) and Scanning Electron Microscopy Energy Dispersive X-Ray Spectroscopy (SEM-EDS). Sample 18666, 12 is clast-poor (<5%) with the majority of clasts identified to date being gabbroic in nature (coarse-grained, co-existing Ca-rich plagioclase with clinopyroxene). In addition, a SiO2 polymorph coexisting with Ca-rich plagioclase in one clast (700 m across) has also been identified (likely cristobalite based on crystal habit). Individual mineral fragments are common with Ca-rich plagioclase, clinopyroxene, minor olivine and trace ilmenite. To complement thin section study, a 19.970 mm³ rock chip of DOM 18666 was analyzed via X-ray computed tomography (XCT). Preliminary volumetric analyses of meteorite components via Blob 3D are consistent with PLM and SEM-EDS observations with major pyroxene and plagioclase feldspar (+matrix), minor olivine, and trace ilmenite (<0.1 vol.%). Analysis of component orientations via Stereo32 revealed that no significant clustering exists (i.e., mineral phases lack preferred orientations). Given the overall basaltic nature of 18666, and the trace levels of ilmenite, it is inferred that DOM 18666 originated from a region on the Moon within (or near to) the low-Ti maria. Future work will focus on utilizing SEM-EDS maps as guides for in-situ elemental analysis via electron probe microanalysis (EPMA) and laser ablation plasma mass spectroscopy (LA-ICP-MS) in order to evaluate the petrogenetic history of individual mineral grains. In addition, study of DOM 18666 via Electron Back Scatter Diffraction (EBSD) will permit an assessment of the degree of shock this brecciated sample experienced. Collectively, the data acquired will contribute to our understanding of lunar meteorite petrogenesis and the production of breccias on planetary objects.