Petrogenesis of Chang’e-6 Basalts and Implication for the Young Volcanism on the Lunar Farside
Chengxiang Yin, Jian Chen, Xiaohui Fu, Haijun Cao, X. Lu, Yiheng Liu, Jin Li, Siyue Chi, Xiaojia Zeng, Zongcheng Ling
Abstract
Abstract Mare basalts from lunar farside are pivotal for unraveling lunar nearside-farside dichotomies and global thermal history. The Chang’e-6 (CE-6) mission conducted the first sampling from a young basaltic unit within the Apollo basin on the lunar farside. Here, we performed comprehensive petrological and geochemical analyses on the CE-6 basalt clasts. The CE-6 basalt is a low-titanium basalt (about 5 wt% TiO 2 ) depleted in KREEP components. The absence of olivine, particularly magnesium-rich olivine, suggests that the basaltic magma underwent extensive fractional crystallization. Thermodynamic modeling supports that there may be 10%–20% late-stage cumulates of magma ocean (clinopyroxene and ilmenite) present in the source region of CE-6 basalt. The magma derived from the partial melting of such lunar mantle may undergo fractional crystallization dominated by olivine and clinopyroxene within a shallow magma cg1hamber, followed by eruption. Modeling of the REE pattern further indicates that 3%–7% batch melting of a depleted lunar mantle source, combined with 21%–59% fractional crystallization, achieves the observed REE abundances of CE-6 basalt. The genesis of CE-6 basalt could be attributed to the synergistic influence of a readily fusible mantle source, resulting from the incorporation of late-stage cumulates, and the crust-mantle deformation induced by large impacts. This could serve as a paradigm for the formation of other young basalts on the Moon.