¹S. Effraimidou, ¹I. Baziotis, ¹M. Simopoulou, ²L. Ferrière, ³C. Sanchez-Valle, ³S. Klemme, ³J. Berndt, ⁴P. D. Asimow
Meteoritics & Planetary Science (in Press) Open Access Link to Article [DOI: 10.1111/maps.70228]
¹Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Athens, Greece
²Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
³Institut für Mineralogie, Universität Münster, Münster, Germany
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Published by arrangement with John Wiley & Sons

This study investigates the petrography and mineralogy of three L-type ordinary chondrite meteorites: Northwest Africa (NWA) 4137 (L6), Homestead (L5), and Kunashak (L6). We studied the shock-related deformation features in the matrix and the characteristics of the melt veins, including the presence or absence of high-pressure (HP) phases. Our goal is to constrain the shock history of these meteorites, including constraints on peak shock conditions and on post-shock thermal histories. All three studied meteorites are strongly shocked, with textural evidence indicating shock stages up to S4 and development of melt veins. However, NWA 4137 is the only one of these meteorites in which HP phases were observed; we identified wadsleyite, majorite, albitic jadeite, tuite, and xieite within melt veins, indicating peak shock pressure in the range of 11–23 GPa. In contrast, the investigated melt veins in Homestead and Kunashak lack any HP phases despite indicators of comparable shock intensity to that observed in NWA 4137. The absence of HP phases in these two meteorites is attributed to a high post-shock temperature that favored back-transformation into low-P minerals during decompression over preservation of HP phases. These case studies testify to the importance of the full pressure (P)–temperature (T)–time (t) path experienced by meteoritic samples during shock events in determining their ultimate mineralogy.

¹Pengfei Liu (>10)
Proceedings of the National Academy of Sciences (in Press) Link to Article [DOI: 10.1073/pnas.2608395123]
¹Macau Institute of Space Technology and Application, Macau University of Science and Technology, Macau 999078, China
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On the lunar surface α-Fe and Fe-Ni alloys are widespread and the dominant carriers of the lunar remanent magnetization. Metallic γ-Fe, however, is stable only at high temperatures and has not been documented in lunar samples. Here we report the identification of ambient stable γ-Fe preserved as nanometer-scale particles in Chang’e-6 impact glass fragments from the South Pole-Aitken Basin. Electron holography analyses reveal that these γ-Fe particles have a magnetic vortex domain state. Based on these results, we propose that the formation and preservation of γ-Fe at lunar surface temperature requires incorporation of trace γ-phase-stabilizing elements together with extremely rapid quenching during lunar impact processes. Our findings provide a basis for understanding the lunar core dynamo evolution and impact-induced magnetic recording mechanisms.