Impact history and origin of lunar meteorite Northwest Africa 15528

No samples from the Moon’s far side have been returned to Earth. Thus, lunar meteorite study can deepen the understanding of the Moon’s far side (if we can identify which lunar meteorites came from the Moon’s far side). The Northwest Africa (NWA) 15528 meteorite is a lunar feldspathic regolith breccia meteorite and we speculated it might originate from the Feldspathic Highlands Terrane (FHT) on the far side of the Moon. Here, we report detailed petrography, major and trace elements, and noble gas (He, Ne, and Ar) isotopes for the clasts and matrix, respectively. The results show that the NWA 15528 lunar meteorite contains diverse clasts, including anorthosite, granulite, basalt, and impact melt clasts. The coarse, well-crystallized, uniform chemical composition minerals may come from intrusive plutonic rocks. Among the anorthosite clasts, the norite/olivine clasts originate from the deep lunar crust, whereas the other anorthosite clasts are from lunar highlands. The Sm concentrations in NWA 15528 were similar to those in the fourth group of Apollo 16 melt samples, demonstrating that NWA 15528 has a typical plagioclase highland meteorite composition. Compared with the Apollo sample data and remote sensing results, the chemical composition of NWA 15528 indicated strong affinities with the FHT area and ferroan anorthosite (FAN) material from the far side of the Moon. The noble gas isotopic composition of NWA 15528 is consistent with a binary mixture of solar wind and cosmogenic components; during stepwise pyrolytic extractions, we observed that the abundance of cosmogenic components decreased, whereas that of solar wind components increased with increasing temperature. The average cosmic-ray exposure (CRE) age of the matrix and granulite is 42±6 Ma, with a shielding depth in the same range of 10–20 g cm−2. The gas retention age of NWA 15528 is 2.14 Ga, and the antiquity age of NWA 15528 is (0.69–0.74)±0.2 Ga (considering 50% 40Arm is 40Artrap) which indicates the different clasts of NWA 15528 are assembled after 0.69–0.74 Ga.