First Location And Characterization Of Lunar Highland Clasts In Chang’E-5 Breccias Using TIMA-SEM-EPMA

Abstract

In this study, we identify for the first time four lunar highland clasts from the breccias (CE5C0800YJYX132GP) returned by the Chang’E 5 (CE-5) mission by combining Tescan Integrated Mineral Analysis (TIMA), Scanning Electron Microscopy (SEM), and Electron Probe Microanalysis (EPMA) techniques. The chemical compositions of plagioclases (An93.9–97.6) and mafic minerals (Fo71.4–87.9 for olivine and Mg65.1–84.6 for pyroxene) in these clasts are remarkably distinct from the more abundant mare basalts in the CE-5 landing site. They are in noritic anorthositic, troctolitic anorthositic, and troctolitic anorthositic compositions, which represent lunar highland crustal materials. Additionally, the three anorthositic clasts in the CE-5 samples are more magnesian than the Apollo ferroan anorthosites (FANs), but are similar to the magnesian anorthosites (MANs) commonly found in lunar highland meteorites. These newly found MANs in the CE-5 breccia are among the few reported in lunar returned samples, and may represent an important component of the lunar highland crust. Placing MANs in the rock lithologies of lunar feldspathic crust require a more complex crust-mantle process than that predicted by the classic Lunar Magma Ocean (LMO) hypothesis. Therefore, future research and characterization of Mg-suite and magnesian anorthositic rocks in CE-5 samples may help elucidate early lunar crustal evolution and crustmantle interaction.