Isotopic and compositional constraints on the source of basalt collected from the lunar farside.

Che, Xiaochao; Long, Tao; Nemchin, Alexander; Xie, Shiwen; Qiao, Le; Li, Zengsheng; Ban, Yiyi; Fan, Runlong et al. · Science · 2025

basic_science · Level V

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Abstract

Volcanism on the Moon has produced surface basalt deposits, which record lunar interior processes. The Chang'e-6 mission retrieved samples from the South Pole-Aitken basin (SPA) on the Moon's far side. We analyzed basalt fragments collected by Chang'e-6 and found that their composition resembles that of low-titanium basalts previously sampled by the Apollo missions. Uranium-lead (U-Pb) dating indicated a basalt age of 2823.0 ± 5.9 million years and a source <sup>238</sup>U/<sup>204</sup>Pb ratio (μ-value) of 480 ± 56. This high μ-value indicates that the source contained materials that formed during the late stages of lunar magma ocean (LMO) crystallization. The results are consistent with the LMO model, but the Chang'e-6 basalt deviates from the trend in Apollo mission samples of younger basalts having higher μ-values. We suggest that this indicates post-LMO modification of the mantle by the SPA impact.