^1,2Cheng-Yu Du, ^1,2Shao-Bing Zhang, ³Hejiu Hui, ¹Ting Liang, ¹Wan-Cai Li, ¹Yong-Fei Zheng
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.05.006]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
²Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
³State Key Laboratory for Mineral Deposits Research & Lunar and Planetary Science Institute, School of the Earth Sciences and Engineering, Nanjing University, Nanjing, China
Copyright Elsevier

China’s Chang’E-5 (CE-5) lunar mission retrieved the youngest known mare basalt with low magnesium number (Mg#) and high incompatible element contents. However, the nature of its mantle source remains debated. Here we carried out in-situ analyses of major and trace element contents in olivine and pyroxene for CE-5 basalt clasts to constrain the petrogenetic process and mantle source of CE-5 basalt. The results indicate that the pyroxene Ti# (molar Ti/(Ti + Cr)) rose sharply at an early stage into the high-Ti basalt field and subsequently remained constant, implying extensive fractional crystallization of the CE-5 basalt. The near constant Ti content in olivine records an early crystallization of ilmenite at an olivine Mg# of approximately 60. Calculated TiO2 and Cr2O3 contents of the melt equilibrated with the most forsteritic olivine yielded TiO2 content of 6.06 ± 0.77 wt% and Cr2O3 content of 0.516 ± 0.089 wt%. Pyroxene exhibits concurrent decreases in LREE/HREE ratios, Zr/Y ratio and Al content as its Mg# decreases, whereas the early decrease of olivine Zr/Y ratio indicates a primitive melt with high Zr/Y ratio. Integrating these findings with previously reported isotopic data, theoretical modelling supports a hybrid mantle source dominated by orthopyroxene cumulate, with a small proportion of ilmenite-bearing cumulate (IBC, 0.40–0.55%) and KREEP (0.11–0.15%). Such a source region supports a geodynamic mechanism for the young mare magmatism that the IBC-rich hot plume rises from the core-mantle boundary heating the upper mantle that contains small amounts of IBC and KREEP to melt.