Unique achondrite Northwest Africa 11042: Exploring the melting and breakup of the L chondrite parent body

1,2Zoltán Váci,1,2Carl B. Agee,3Munir Humayun,1,2Karen Ziegler,2Yemane Asmerom,2Victor Polyak,4Henner Busemann,4Daniela Krietsch,5Matthew Heizler,6Matthew E. Sanborn,6Qing‐Zhu Yin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13456]
1Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87131 USA
2Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131 USA
3National High Magnetic Field Laboratory, Department of Earth Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, 32310 USA
4Institute of Geochemistry and Petrology, ETH Zürich, 8092 Zurich, Switzerland
5New Mexico Bureau of Geology, New Mexico Institute of Mining and Technology, Socorro, New Mexico, 87801 USA
6Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, 95616 USA
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 11042 is a heavily shocked achondrite with medium‐grained cumulate textures. Its olivine and pyroxene compositions, oxygen isotopic composition, and chromium isotopic composition are consistent with L chondrites. Sm‐Nd dating of its primary phases shows a crystallization age of 4100 ± 160 Ma. Ar‐Ar dating of its shocked mineral maskelynite reveals an age of 484.0 ± 1.5 Ma. This age coincides roughly with the breakup event of the L chondrite parent body evident in the shock ages of many L chondrites and the terrestrial record of fossil L chondritic chromite. NWA 11042 shows large depletions in siderophile elements (<0.01×CI) suggestive of a complex igneous history involving extraction of a Fe‐Ni‐S liquid on the L chondrite parent body. Due to its relatively young crystallization age, the heat source for such an igneous process is most likely impact. Because its mineralogy, petrology, and O isotopes are similar to the ungrouped achondrite NWA 4284 (this work), the two meteorites are likely paired and derived from the same parent body.

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