| Abstrakt: |
Although lunar soils contain rock and mineral components from the breakdown of a mixture of rock types, a classification based on the abundances of the major silicate minerals plagioclase, olivine, low‐Ca pyroxene (LCP) and high‐Ca pyroxene can be used to evaluate the major compositional classes that are represented within a given soil. We studied the compositional classes for Apollo 15, 16, and 17 soil samples based on the mineral modal abundances derived by X‐ray diffraction (XRD). Using the XRD results as a ground truth, we determined the compositional classes of the Apollo 15, 16, and 17 sampling stations using mineral maps from the Kaguya Multiband Imager (MI), then mapped areas having compositional classes similar to the sampling stations on regional and global scales. Global distribution of compositional classes was also mapped using MI mineral maps, and the major compositional classes of lunar nonmare surfaces are noritic anorthosite (40%), anorthositic norite (24%), and anorthosite (23%). Our maps show that the lunar highlands and the South Pole‐Aitken (SPA) basin are enriched with noritic materials, indicating the widespread occurrence of LCP‐rich and olivine‐poor assemblages. In contrast to the SPA basin and the highlands, the basin rings of Serenitatis, Crisium, Humorum, Nectaris, Orientale, and Hertzsprung exhibit higher olivine/pyroxene ratios (>2), and we interpret this signature as reflecting a contribution from olivine‐rich upper mantle components. Plain Language Summary: Global lunar mineral distributions are closely related to the geologic evolution history of the Moon. In this work, we report the mineralogy of Apollo 15, 16, and 17 soil samples based on the relative abundances of plagioclase, olivine and pyroxenes measured in the laboratory. Using these soil sample results as reference, we map global distribution of minerals with data returned from a Japanese lunar satellite called Kaguya. The mafic mineral distribution provides clues to the upper mantle composition, which is important in studying the thermal history and differentiation of the Moon. Our results show that low‐Ca pyroxene (LCP) is much more abundant than olivine in the lunar highlands and within the South Pole‐Aitken (SPA) basin. Models suggest that the SPA basin excavated more than 100 km deep and might have exposed lunar mantle material that is dominated by LCP. In contrast to the SPA basin and the highlands, the rings of large basins that formed after the SPA basin show higher olivine/pyroxene values, which may reflect a contribution from olivine‐rich upper mantle components. Key Points: Low‐Ca pyroxene (LCP) is much more abundant than olivine in highland surfaces and within the South Pole‐Aitken basinThe nonmare surface of lunar highlands and within the South Pole‐Aitken contain LCP‐rich upper mantle materialOur mineral maps support the hypothesis that the rings of the nearside large basins contain olivine‐rich upper mantle material [ABSTRACT FROM AUTHOR] |
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