^1,2Runwu Li, ^1,2Ming Tang, ¹Jiaxi Wang
Earth and Planetary Science Letters 671, 119650 Link to Article [https://doi.org/10.1016/j.epsl.2025.119650]
¹Key Laboratory of Orogenic Belt and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University, Beijing 100871, China
²Research Institute of Extraterrestrial Material (RIEMPKU), School of Earth and Space Sciences, Peking University, Beijing 100871, China
Copyright Elsevier

The samples returned by the recent Chang’e-5 (CE-5) mission confirmed active lunar magmatism at least two billion years ago, which challenged the long-held view of an inactive Moon through much of its lifespan. However, the origin of this extended lunar magmatism remains mysterious. The CE-5 lunar soil and basalt fragments exhibit a strong fractionation between middle and heavy rare earth elements, a phenomenon rarely observed in the Apollo samples. We confirm this fractionation as a primary magmatic signature with measurements of the pyroxenes. By coupling phase equilibria modeling and element partitioning calculations, we show that this fractionation can only be produced if the magma source contained ∼5-10% garnet at a minimum depth of ∼700 km. We suggest the primary CE-5 magma may have originated from the lunar lower mantle. For melting to occur, one possibility is that convection may have been sustained in the deep lunar mantle until at least two billion years ago. Alternatively, the CE-5 magma may have tapped the melt-bearing layer near the core, as indicated by recent seismic observations.