Occurrence and implications of secondary olivine veinlets in lunar highland breccia Northwest Africa 11273

1,2Xiaojia Zeng,1,3Shijie Li,4Katherine H. Joy,1,2,3 Xiongyao Li,1,2,3Jianzhong Liu,1,2,3Yang Li,1,2Rui Li,5Shijie Wang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13421]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081 China
2Key Laboratory of Space Manufacturing Technology, Chinese Academy of Sciences, Beijing, 100094 China
3CAS Center for Excellence in Comparative Planetology, Hefei, China
4Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL UK
5State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081 China
Published by arrangement with John Wiley & Sons

Lunar breccias preserve the records of geologic processes on the Moon. In this study, we report the occurrence, petrography, mineralogy, and geologic significance of the observed secondary olivine veinlets in lunar feldspathic breccia meteorite Northwest Africa (NWA) 11273. Bulk‐rock composition measurements show that this meteorite is geochemically similar to other lunar highland meteorites. In NWA 11273, five clasts are observed to host veinlets that are dominated by interconnecting olivine mineral grains. The host clasts are mainly composed of mafic minerals (i.e., pyroxene and olivine) and probably sourced from a basaltic lithology. The studied olivine veinlets (~5 to 30 μm in width) are distributed within the mafic mineral host, but do not extend into the adjacent plagioclase. Chemically, these olivine veinlets are Fe‐richer (Fo41.4–51.9), compared with other olivine grains (Fo54.3–83.1) in lithic clasts and matrix of NWA 11273. By analogy with the secondary olivine veinlets observed in meteorites from asteroid Vesta (howardite–eucrite–diogenite group samples) and lunar mare samples, our study suggests that the newly observed olivine veinlets in NWA 11273 are likely formed by secondary deposition from a lunar fluid, rather than by crystallization from a high‐temperature silicate melt. Such fluid could be sulfur‐ and phosphorous‐poor and likely had an endogenic origin on the Moon. The new occurrence of secondary olivine veinlets in breccia NWA 11273 reveals that the fluid mobility and deposition could be a previously underappreciated geological process on the Moon.

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