Cooling history and source characteristics of the Chang'e-6 low-Ti basalt: Constraints from plagioclase

作者：Di Zhang, Wei Yang, Huijuan Zhang, Honggang Zhu, Yunhong Fan, Hengci Tian, Shitou Wu, Lihui Jia, Lixin Gu, Yangting Lin · 发表于：Icarus · 年份：2026 · DOI：10.1016/j.icarus.2026.117076 · 研究领域：Geological and Geochemical Analysis、High-pressure geophysics and materials、Paleontology and Stratigraphy of Fossils

The Chang'e-6 (CE-6) mission returned the first lunar farside samples from a basalt unit in the South Pole–Aitken Basin, which can provide novel insights into lunar volcanism. This study investigates the cooling history and source characteristics of the CE-6 low-Ti basalt fragments through the analysis of plagioclase crystal size distribution (CSD) and mineral geochemistry. Most samples indicate single-stage cooling, but a few show multi-stage cooling with microlites (acicular-radiate texture) and megacrysts (tabular-skeletal texture) forming at various rates. The cooling rate estimated by plagioclase CSD analysis ranges from 2.04 to 14.71 °C/h, which is slower than those of the Chang'e-5 and Luna-16 basalts, although comparable to the Apollo low-Ti basalts and lunar meteorites. The residence periods vary from 0.6 to 4.29 days, and thermodynamic modeling suggests average burial depths of 0.57 ± 0.11 m within the lava flow. The equilibrium melt of plagioclase, as estimated by trace element modeling, exhibits low Ba/Sr and La/Sr ratios, indicating that the mantle source is nearly KREEP-free (<0.1%).