The young basalts on the Moon: Pb–Pb isochron dating in Chang’e-5 Basalt
CE5C0000YJYX03501GP
Dunyi Liu1,3, Alexander Nemchin2,1, Xiaochao Che1, Tao Long1, Chen Wang1, Marc D. Norman4, Katherine H. Joy5, Romain
Tartese5, James Head6, Bradley Jolliff 7, Joshua F. Snape5, Clive R. Neal8, Martin J. Whitehouse9, Carolyn Crow10, Gretchen
Benedix2, Fred Jourdan2, Zhiqing Yang1, Chun Yang1, Jianhui Liu1, Shiwen Xie1, Zemin Bao1, Runlong Fan1, Dapeng Li3,Zengsheng Li3, Stuart G. Webb81

Beijing SHRIMPCenter, Institute of Geology, Chinese Academy of Geological Sciences. 2School of Earth and PlanetarySciences, Curtin University. 3Shandong Institute of Geological Sciences, Jinan, Shandong. 4Research School of Earth Sciences,
The Australian National University. 5Department of Earth and Environmental Sciences, The University of Manchester.
6Department of Earth, Environmental, and Planetary Sciences, Brown University. 7Department of Earth and Planetary
Sciences and The McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis. 8Department ofCivil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame. 9Department ofGeosciences, Swedish Museum of Natural History. 10Department of Geological Sciences, University of Colorado Boulder.

Figure 1. A & B false color energy EDS element maps of the two fragments from CE5C0000YJYX03501GP blue=silica, green=Mg, red=Fe,
white=Al, yellow=Ca, pink=Ti, cyan=K. C Pb-Pb isochrons for CE5C0000YJYX03501GP.

China’s Chang’e-5 mission collected 1731g lunar samples at 43.1°N, 51.8°W in the northeastern Oceanus Procellarum of theMoon. Basalt fragments is the main lithic type in the lunar soil returned by Chang’e-5 that showed five distinct texturaltypes[1], The two scooped basalt fragments from CE5C0000YJYX03501GP both are equidimensional, approximately 3-4 mm
in size and consist of clinopyroxene, plagioclase, olivine, ilmenite, quartz, cristobalite, K-rich glass, barian K-feldspar, troilite
and Ca-phosphates, with small amounts of the Zr-rich minerals baddeleyite and zirconolite[Figure 1. A, B]. The pyroxenes andolivines in the two fragments include highly Fe-rich compositions for lunar basalts. and the bulk compositions of bothfragments indicate elevated FeO (~22-25 wt.%) and low MgO (~5 wt.%). The mineralogy and bulk compositions of two basalt
fragments are consistent with remote sensing data of this region [2]. These 677 ± 3 of 238U/204Pb ratio (μ-value) for the two
fragments imply only a modest (<2%) KREEP component either in their mantle sources or introduced by assimilation duringmagma ascent [2].
The Pb isotope data were collected using a SHRIMP IIe-MC at Beijing SHRIMP Center, Institute of Geology, Chinese
Academy of Geological Sciences, Beijing. 204Pb+, 206Pb+, 207Pb+ and 208Pb+ isotopes were measured simultaneously with multicollectors and the 204Pb/206Pb, 207Pb/206Pb and 208Pb/206Pb ratios were calibrated using BCR-2, BHVO-2. Combining all Pb
isotope data from Zr-rich minerals, Ca-phosphates, K-rich glass and barian K-feldspar for the two basalt fragments, gives anisochron age of 1963 ± 57 Ma [Figure 1. C]. This age constrains the lunar impact chronology of the inner Solar System and thethermal evolution of the Moon. Studies of other basalt fragments from Chang’e-5 have yielded similar results [3, 4], andshowed a relatively low water content [5].
Reference[1] Li C. et al. 2021. National Science Review. [2] Che X. et al. 2021. Science. [3] Li Q. et al. 2021. Nature. [4] Tian H. et al.
2021. Nature. [5] Hu S. et al. 2021. Nature.