^1,2,3Haiyang Xian et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2025.119556]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
²Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
³Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
Copyright Elsevier

Recent discoveries regarding oxidized materials on the moon have challenged the traditional belief that the moon is highly reduced. The oxidized materials occur in either crystalline minerals or glasses, and the complex occurrence makes the origin of these oxidized lunar materials still unclear. Here we report a highly oxidized impact melt clast retrieved by Chang’e 6 mission from the South Pole-Aitken (SPA) basin. The impact melt clast hosts a high content of ferric iron (Fe³⁺) in matrix pigeonite with an Fe³⁺/∑Fe ratio of 0.44 ± 0.06, while xenocryst pyroxene only contains ferrous (Fe²⁺) iron. The observed high Fe³⁺ content indicates that the oxidation state of the local impact clast is even more oxidized than that of Earth’s mantle. The widespread presence of non-spherical Fe-Ni alloy nanoparticles in the impact melt clast suggests that the oxidized materials may have been delivered to the moon by meteorite. These findings reveal an external source of oxidized materials on the moon, emphasizing the potential role of meteoritic materials in the redox cycling of the lunar surface.

¹Zhengyang Wu, ¹Chang Pu, ¹Xiujin Gao, ¹Jinfeng Li, ²Zhixue Du, ¹Zhicheng Jing
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.07.024]
¹Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen 518055, China
²State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Copyright Elsevier

Gallium (Ga) and germanium (Ge) are moderately siderophile and volatile elements whose metal-silicate partitioning behaviors are valuable to understand both core-formation and volatile accretion processes. In this study, we performed metal-silicate partitioning experiments at pressures of 22–70 GPa and temperatures of 3728–4740 K, using laser-heated diamond anvil cells, to explore the effects of pressure, temperature, and metal composition on Ga and Ge partitioning. Thermodynamic modeling using our experimental data and those from the literature reveals that the metal affinities of both Ga and Ge decrease as pressure and temperature increase, with Ga being less siderophile than Ge. Our fitting results confirm that the presence of S and Si in metal can reduce the siderophility of both Ga and Ge, consistent with previous findings at relatively low pressures and temperatures. Our results also demonstrate that O in metal has opposing effects on the metal-silicate partitioning of Ga and Ge. It increases the metal affinity of Ga, contrary to previous thought, but decreases that of Ge. Incorporating these partitioning behaviors, we performed multi-stage core formation modeling to search for accretion scenarios and factors that can reproduce the bulk silicate Earth abundances of Ga, Ge, and S. Our results suggest that Ga and Ge were likely accreted throughout the entire stages of Earth’s accretion rather than accreted solely in the late stage for the final 10–20 % of Earth’s mass growth.