¹Ziqing Li, ²Mengfan Zhang, ¹Bo Zhang, ³Yuqi Qian, ⁴Tao Long, ⁴Xiaochao Che, ¹Ao Su, ⁵James W. Head
Journal of Geophysical Research: Planets, 131, e2026JE009898 Open Source Link to Article [DOI: 10.1029/2026JE009898]
¹Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, China
²School of Earth and Space Sciences and Institute of Energy, Peking University, Beijing, China
³Department of Earth and Planetary Sciences, NWU-HKU Joint Center of Earth and Planetary Sciences, The University of Hong Kong, Hong Kong, China
⁴Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
⁵Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
Published by arrangement with John Wiley & Sons

The cause of the observed mare basalt asymmetry between the lunar nearside and farside remains a long-lasting conundrum. In this study, we characterized the petrology and geochemistry of the Chang’e-6 low-Ti basalts from the lunar farside, performed petrological modeling of major elements and conducted Monte Carlo simulation of trace elements, for Chang’e-6 and Chang’e-5 basalts. The results from multiple approaches indicate that the young Chang’e-6 (2.8 Ga) and Chang’e-5 (2.0 Ga) basalts both originated from shallow, depleted ilmenite-bearing cumulate (IBC). Based on remote sensing and thermodynamic constraints, we estimated the mantle source ilmenite abundance for young shallow-source basalts (<3.0 Ga) globally. The modeling results indicate that the mantle sources of these basalts on the nearside generally contains ∼16–32 wt% ilmenite, especially beneath the PKT, whereas the mantle sources of these basalts beneath the farside SPA basin only has ∼13–24 wt% ilmenite. The phase equilibrium calculations show that the nearside mantle sources with higher ilmenite abundance leads to a significant decrease in melting point and tends to produce more melt compared to farside mantle sources. Therefore, asymmetric IBCs may play a key role in accounting for asymmetric nearside/farside volcanism.