¹Lingzhi Sun,¹Paul G. Lucey
Earth and Planetary Science Letters 643, 118931 Link to Article [https://doi.org/10.1016/j.epsl.2024.118931]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

The South Pole-Aitken (SPA) basin, excavating more than 100 km depth, must have exposed extensive lunar mantle materials, making it a promising location for sampling mantle material. To investigate the distribution of potential mantle materials across the SPA basin, we mapped the distribution of Mg# and major minerals contents using Moon Mineralogy Mapping data and radiative transfer modeling. We found that the potential mantle material exposed by SPA is Mg-rich orthopyroxenite, and we identified the locations of seven mantle candidate sites. The Chang’E-6 sample return site is located near mantle candidate sites within the Apollo basin, making it promising to return the first unambiguous mantle sample. Our Mg# and mineral mapping results show that the SPA ejecta is enriched in low-Ca pyroxene (LCP) with Mg#≥85, consistent with a post-overturn upper mantle composition. The enrichment of LCP in the SPA upper mantle may result from a low content of dunite or incomplete overturn.

¹C. J. Floyd,²S. Benito,¹P.-E. Martin,¹L. E. Jenkins,³E. Dunham,^1,4,5L. Daly,¹M. R. Lee
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14250]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
²Ruhr-Universität Bochum, Chair of Materials Technology, Bochum, Germany
³Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, California, USA
⁴Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales, Australia
⁵Department of Materials, University of Oxford, Oxford, UK
Published by arrangement with John Wiley & Sons

The sizes of chondrules are a valuable tool for understanding relationships between meteorite groups and the affinity of ungrouped chondrites, documenting temporal/spatial variability in the solar nebula, and exploring the effects of parent body processing. Many of the recently reported sizes of chondrules within the CM carbonaceous chondrites differ significantly from the established literature average and are more closely comparable to those of chondrules within CO chondrites. Here, we report an updated analysis of chondrule dimensions within the CM group based on data from 1937 chondrules, obtained across a suite of CM lithologies ranging from petrologic subtypes CM2.2 to CM2.7. Our revised average CM chondrule size is 194 μm. Among the samples examined, a relationship was observed between petrologic subtype and chondrule size such that chondrule long-axis lengths are greater in the more highly aqueously altered lithologies. These findings suggest a greater similarity between the CM and CO chondrites than previously thought and support arguments for a genetic link between the two groups (i.e., the CM-CO clan). Using the 2-D and 3-D data gathered, we also apply numerous stereological corrections to examine their usefulness in correcting 2-D chondrule measurements within the CM chondrites. Alongside this analysis, we present the details of a standardized methodology for 2-D chondrule size measurement to facilitate more reliable inter-study comparisons.