Isotopic and compositional constraints on the source of basalt collected from the lunar farside
Xiaochao Che, Tao Long, A. A. Nemchin, Shiwen Xie, Le Qiao, Zengsheng Li, Yiyi Ban, Runlong Fan, Chun Yang, Dunyi Liu
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 238 U/ 204 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.