Abundant Non-Mare Components in the Chang'e-6 Lunar Regolith: Constraints From Plagioclase Fragments and Impact Glasses

Abstract

Lunar regolith contains not only materials derived from the local rock unit, but also materials transferred from remote craters, which are crucial for investigating the lithological diversity of the lunar surface. In this study, we conducted detailed petrography and geochemical analyses and measured the cross-sectional area of plagioclase fragments and impact glass particles selected from the Chang'e 6 (CE-6) regolith, the first lunar far-side returned sample. Statistics of plagioclase fragments and impact glass are used to estimate the proportion of the diverse components in the CE-6 regolith. The results reveal 35.7 vol% and 28.2 vol% exotic components in CE-6 plagioclase and impact glass fractions, respectively. As plagioclase, pyroxene and glass particles are the three dominant phases (>95 vol%) in the CE-6 regolith, together with previously reported pyroxene compositions, we estimate that the abundance of the exotic materials is 23.5–33.5 vol%. These exogeneous components include very-low-Ti (VLT) basalt (2%–3%), ferroan anorthosite (5%–9%), Mg-suite (15%–20%), KREEP-related (∼0.1%), and highlands-mare-mixed materials (∼1%). The VLT-basalt component is most likely from the mare basalt unit to the east of the landing site or beneath the local mare layer. Based on the ejecta orientations and model age of impact craters, ferroan anorthite, Mg-suite and KREEP-related materials are likely transferred from Vavilov/Pythagoras (highland anorthosite), Chaffee S/White’ (rich in mafic minerals), and Birkeland (high Th contents) craters, respectively. The abundant non-mare components in the CE-6 regolith contrast to the very scarce exotic materials in the CE-5 lunar regolith, potentially providing valuable insights into the composition of the lunar far-side.