^1,2,3C.K. Shearer,^4,5,6D.P. Moriarty,¹S.B. Simon,⁴N. Petro,^1,2J.J. Papike
Journal Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2022JE007409]
¹Institute of Meteoritics, University of New Mexico, Albuquerque, NM, 87131 United States
²Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, 87131 United States
³Lunar and Planetary Institute, Houston, TX, 77058 United States
⁴NASA Goddard Space Flight Center, Greenbelt, MD, 20771 United States
⁵University of Maryland, College Park, MD, 20742 United States
⁶Center for Research and Exploration in Space Science and Technology, College Park, MD, 20742 United States
Published by arrangement with Jon Wiley & Sons

Remote sensing observations have been interpreted to indicate that the Crisium basin-forming event excavated deep crust and upper mantle. Samples from the highlands adjacent to the Crisium basin returned by Luna 20 (L-20) bring a unique perspective for evaluating this concept. The magmatic lithologies returned from the noritic Hilly and Furrowed Terrain (nHFT) by L-20 are coarse-grained feldspar (>300 µm) with inclusions of pyroxene, and a finer-grained norites, troctolites, spinel troctolites, and gabbros (<100 µm). These two suites represent ferroan anorthosites (FANs) and the Mg-suite, respectively. There is limited evidence for mantle or deep crustal material within the nHFT samples. Ultramafic rocks such as dunites and orthopyroxenites are absent, and Mg-rich olivine- and orthopyroxene-bearing-assemblages are derived from magmatic rocks emplaced in the shallow crust. These lithic fragments represent pre-Crisium episodes of magmatism and lunar magma ocean products. The lack of deep lithologies at the L-20 site seems contradictory to excavation models for Crisium. Mineralogical-chemical differences suggest a higher FAN component in the rim and that this represents FANs excavated from the deep lunar crust. If it exists, the Mg-rich olivine previously identified within the Crisium rim is most likely related to deep, complementary versions of the Mg-suite rocks from L-20. The material associated with the Crisium basin is not derived from the lunar mantle but represents crustal lithologies from the shallow to deep crust, a substantial mantle component may have been incorporated into the Crisium basin impact melt sheet, or that our “Earth-analog” for the lunar upper mantle is incorrect.