Zhou Qin, Yang Wei, Chu Zhuyin, Zhu Honggang, Yang Saihong, Zeng Xingguo, Xue Ding-Shuai, Jia Li-Hui, Zhang Guangliang, Zhang Hongbo, Lin Yanhao, Zhang Huijuan, Tian Heng-Ci, Peng Peng, Zhang Dan-Ping, Gu Lixin, Li Chunlai, Wu Fu-Yuan
Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China.
Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
Nature. 2025 Jul;643(8071):371-375. doi: 10.1038/s41586-025-09131-7. Epub 2025 Jul 9.
Lunar mare basalts illuminate the nature of the Moon's mantle, the lunar compositional asymmetry and the early lunar magma ocean (LMO). However, the characteristics of the mantle beneath the vast South Pole-Aitken (SPA) basin on the lunar farside remain a mystery. Here we present the petrology and geochemistry of basalt fragments from Chang'e-6 (CE6), the first returned lunar farside samples from the SPA basin. These 2.8-billion-year-old CE6 basalts share similar major element compositions with the most evolved Apollo 12 ilmenite basalts. They exhibit extreme Sr-Nd depletion, with initial Sr/Sr ratios of 0.699237 to 0.699329 and ε(t) values (a measure of the neodymium isotopic composition) of 15.80 to 16.13. These characteristics indicate an ultra-depleted mantle, resulting from LMO crystallization and/or later depletion by melt extraction. The former scenario implies that the nearside and farside may possess an isotopically analogous depleted mantle endmember. The latter is probably related to the SPA impact, indicating that post-accretion massive impacts could have potentially triggered large-scale melt extraction of the underlying mantle. Either way, originating during the LMO or later melt extraction, the ultra-depleted mantle beneath the SPA basin offers a deep observational window into early lunar crust-mantle differentiation.
月海玄武岩揭示了月球地幔的性质、月球成分的不对称性以及早期月球岩浆海洋（LMO）。然而，月球背面广阔的南极-艾特肯（SPA）盆地之下地幔的特征仍是个谜。在此，我们展示了嫦娥六号（CE6）玄武岩碎块的岩石学和地球化学特征，CE6是首批从SPA盆地返回的月球背面样本。这些有28亿年历史的CE6玄武岩与演化程度最高的阿波罗12号钛铁矿玄武岩具有相似的主要元素组成。它们表现出极端的锶-钕亏损，初始锶/锶比值为0.699237至0.699329，ε(t)值（一种钕同位素组成的度量）为15.80至16.13。这些特征表明存在一个极度亏损的地幔，这是由LMO结晶和/或后期通过熔体提取造成的亏损所致。前一种情况意味着近侧和远侧可能拥有同位素类似的亏损地幔端元。后一种情况可能与SPA撞击有关，表明吸积后大规模撞击可能潜在地引发了下伏地幔的大规模熔体提取。无论哪种方式，无论是起源于LMO期间还是后期熔体提取，SPA盆地之下的极度亏损地幔都为早期月球壳幔分化提供了一个深入的观测窗口。
