Mineralogical and Geochemical Study of the Low-Ti Lunar Basaltic Meteorite NWA_16727

NWA_16727 is a lunar basaltic meteorite recovered from Northwest Africa, characterized by a medium-grained subophitic texture. The primary mineral assemblage consists of pyroxene and maskelynite with small amounts of olivine, chromite, ilmenite, phosphate, silica, Fe-Ni metal, and zircon-rich phases. Pyroxene appears as subhedral to anhedral grains, typically medium-grained. These grains exhibit strong compositional zoning from Mg-rich cores to Fe-rich rims, with Fe/Mn ratios ranging from 47 to 98. Measured Fe# varies between 0.33–0.99, and Mg# varies between 0.50 and 66.9, values consistent with known lunar basalts. Fractures are common, and some grains contain melt pockets. Olivine crystals are zoned grains featuring Mg-rich cores that transition to Fe-rich rims (Fo~6–63), commonly hosting melt inclusions. These compositional differences produce a bimodal olivine population at Fa_36–65 and Fa_70–95, with Fe/Mn ratios of 93–141. Surfaces often show fractures resembling shock-induced features observed in other lunar materials. Raman spectroscopy confirms that plagioclase has been entirely transformed to maskelynite in most instances, demonstrating high-pressure shock metamorphism. Typical compositions range from An_85–91 to Or_0.17–0.76. Maskelynite grains remain relatively clear surface, although microfractures cross-cut certain regions, suggesting extensive shock deformation. Abundant mineral fragments, impact melt veins, and shock-induced glass are observed throughout the sample. Impact melt veins incorporate partially melted pyroxene, silica, glassy melt, and nanometer-scale Fe-metal and troilite. Ilmenite and chromite constitute the main Fe-oxides, typically forming euhedral to subhedral grains associated with pyroxene or olivine. Aggregates of olivine and Cr-Ti-Fe spinels are often rimmed by Fe-rich reaction zones. Fe/Mn ratios in pyroxene and olivine confirm the sample’s lunar origin. Pyroxene Ti/(Ti+Cr) and ratios are comparable to those found in low-Ti basalt groups. Rare Earth Element patterns, normalized to CI chondrites, highlight a negative Eu anomaly in pyroxene, alongside relative depletion of both light and heavy REE. Conversely, plagioclase shows strong LREE enrichment and a significant positive Eu anomaly. Overall, the meteorite is classified as a low-Ti basalt. Its pyroxene compositions closely resemble those of other lunar basalts, especially NWA14526, NWA_13137, and NWA_12008, and the pyroxene and maskelynite REE pattern align well with NWA_12008. Based on comprehensive petrological, mineralogical, and geochemical evidence, we hypothesize that NWA_16727 and NWA_12008 may represent paired meteorites.