^1,2Mu-Han Yang, ¹Qian W.L. Zhang, ³Richard W. Carlson, ^1,2Bi-Wen Wang, ¹Dongjian Ouyang^1,2Qiu-Li Li
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116889]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
³Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
Copyright Elsevier

The Moon’s formation time is a key factor for understanding the early evolution of the Earth-Moon system. The lunar magma ocean (LMO) model explains how cumulate mafic materials crystallizing from the LMO form the source of mare basalts (SMB). The SMB with an equilibrated SmNd system is considered to share an identical initial Pb isotope signature (Pb_SMB). Because Pb is volatile while U is refractory, Pb_SMB can provide constraints for the timing of volatile depletion, most likely dating the time of Moon formation by a giant impact. The Pb_SMB is a link between the initial Pb composition of lunar mare basalts and the Moon’s early evolution via a two-stage Pb evolution model that provides a simplified but informative framework. Using four mare basalts with well-constrained ages and initial Pb isotopic compositions, we estimate the Moon’s formation time at  Ma and the SMB formation time at  Ma, which we regard as the preferred solution within the statistical framework of the model. Our modelling strategy also facilitates the dating of mare basalt fragments lacking Zr-bearing minerals using the initial Pb isotopic compositions constrained by U-poor minerals.