^1,2Elana G. Alevy,³Tasha L. Dunn,⁴Alexander N. Krot,^4,5Paul Cardon-Pilotaz,⁶Juliane Gross
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14358]
¹Department of Geology, Colby College, Waterville, Maine, USA
²Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
³Department of Geology, Colby College, Waterville, Maine, USA
⁴ Institute of Geophysics and Planetology, School of Ocean and Earth Science Technology, University of Hawai’i at Mānoa, Honolulu, Hawaii, USA
⁵Ecole Normale Supérieure de Lyon, Lyon, France
⁶Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

Camel Donga 003 (CD 003) was originally classified as a CK3 chondrite based on its coarse-grained matrix, Ni-rich sulfides, Cr-rich magnetite, and CK-like silicate mineralogy. However, after preliminary backscattered electron imaging and elemental mapping of a 400 mm2 thin section of CD 003, subsequent mineral chemistry analysis confirmed that the sample is a fragmental breccia consisting of three oxidized CV lithologies. In the two largest lithologies, both mineralogically pristine and metasomatically altered refractory inclusions are commonly found in close proximity to one another. This suggests that brecciation and mixing of different lithologies in CD 003 occurred on a submillimeter scale. The least abundant lithology—an 8 × 3 mm clast—is distinguished from the other lithologies by its recrystallized matrix, poorly defined chondrules, and equilibrated olivine (Fa42). The homogeneity of matrix and chondrule olivine indicates that this lithology has been metamorphosed to at least petrologic subtype 3.8 conditions. We can trace the provenance of our sample to the main mass of CD 003, which must contain the CK material described in its original classification. Therefore, the presence of the three oxidized CV lithologies suggests that CD 003 is the first CV/CK3 chondrite breccia.

¹Stu Webb,¹Clive R. Neal,²Bridget Guiza,²James M. D. Day
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14362]
¹Department of Civil & Environmental Engineering & Earth Science, University of Notre Dame, Notre Dame, Indiana, USA
²Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
Published by arrangement with John Wiley & Sons

High-Al Apollo 14 basalt 14053 has been identified as an endogenous partial melt product from the lunar interior based on geochemical analyses, specifically low abundances of highly siderophile elements, but exhibits textural characteristics similar to those of impact melts. Prior studies of this sample have described mineralogical differences between “interior” and “exterior” portions, which have been attributed to exposure at the lunar surface and subsequent metamorphism through subsolidus reheating within or in proximity to an impact-ejecta blanket. It has been demonstrated that quantitative textural analysis is a useful tool for distinguishing between lunar rocks altered by impact processes and those produced by endogenic magmatic processes. Such an approach is used in this study to analyze multiple thin sections cut from interior and exterior portions of 14053. The textural heterogeneity of plagioclase crystals among thin sections revealed in this study suggests that an impact-ejecta blanket likely impinged on the western side of 14053. This thermal metamorphism coarsened the plagioclase grains within that portion of 14053 so intensely that components diffused to form subtle layering and moderate textural heterogeneity that was quantifiable. These results also support previous conclusions that suggest the differences in reduction textures within this sample are due to the limited penetration depth of solar-wind implanted hydrogen prior to reheating. Thermal metamorphism can produce textural changes in lunar samples even if below the solidus temperature, such that the plagioclase texture of an endogenous basalt is sufficiently altered to that resembling an impact melt. These results highlight the significance of quantitative petrographic observations of lunar samples to reveal important petrogenetic information that has to be placed in proper spatial context to be understood.