KREEP materials recorded in impact glasses of Chang'e-6 regolith returned from the South Pole-Aitken Basin

The Chang'e-6 mission achieved the first-ever sample return from the lunar farside. The landing site is located within the South Pole-Aitken (SPA) basin, which is the largest and oldest impact structure on the Moon. In this study, approximately 2360 glass beads were separated from 5 g of lunar soil. Among them, 640 homogeneous impact-generated glass beads were selected to investigate the compositional characteristics of the sampling site and surrounding unsampled regions. The average major element composition of these glass beads deviates significantly from that of local basalt, and the TiO₂ content displays a bimodal distribution (∼3.1 wt% and ∼0.6 wt%), indicating substantial input from low-Ti exotic components. Based on their major element characteristics, 116 glass beads were selected for trace element analysis. Four chemically distinct types of glass beads were identified: regolith-like (n = 37), basalt-like (n = 2), feldspathic-like (n = 18) and KREEP-like (n = 27). The first two types originate from local regolith and basalt, respectively. The feldspathic-like glasses are characterized by high Al, low Ti, high Mg#, and significantly positive Eu anomalies, indicating that their source materials most likely originated from noritic lithologies formed through differentiation of impact melt within the SPA basin. The KREEP-like glasses are enriched in incompatible trace elements, exhibit high ⁸⁷Rb/⁸⁶Sr ratios, and show distinctly negative Eu anomalies, which point to the incorporation of KREEP components in their source materials. Based on the compositional characteristics of the sampling region, along with La, Cr concentrations and Mg# of the KREEP-like glass beads, we infer the potential existence of KREEP-rich high-Al basalts, Mg-suite, and alkali-suite distributions in the areas surrounding the landing site. This study provides direct sample-based evidence for the presence of KREEP components within the SPA basin, offering constraints on the mechanisms through which KREEP asymmetry accounts for the Moon's dichotomy.