Chemical compositions of Chang’e-6 lunar soil and substantial addition of noritic crust ejecta from Apollo basin

Abstract The Chang’e-6 (CE-6) mission returned the first-ever soil samples from a farside mare basalt unit within the Apollo basin, the largest impact feature of the South Pole–Aitken (SPA) basin. Here, we integrated petrological and geochemical analyses on this soil and its main components to estimate the compositions of local mare basalt and nonmare components. The landing site basalt is a typical low-Ti basalt with low Mg# (30–31) and low contents of Th (1 ppm) and other incompatible elements. The bulk soil overall shows homogeneous major and trace elemental compositions, which are very different from the local basalt. Combined with petrological constraints, such differences reveal an incorporation of ~40 ± 5 wt% of noritic crust ejecta and 2–3 wt% meteoritic materials, without mantle-rock fragments. The mean composition of nonmare materials corresponds to anorthositic norite or norite (~60 ± 5 vol% plagioclase) and is broadly comparable with Northwest Africa (NWA) 2995 clan meteorites and the prediction from remote sensing data for the SPA basin. The low-Th contents of the basalt, soil, breccia, and impact glasses (1–2 ppm) support negligible Th-rich components in ejecta materials and the underlying mantle and crust. These ground-truth results suggest the dominant distribution of intermediate FeO, mafic crust rocks on the Apollo basin floor, providing insights into the composition of the farside crust within the SPA basin.