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

Zoltán Váci, Carl B. Agee, Munir Humayun, Karen Ziegler, Yemane Asmerom, Victor Polyak, Henner Busemann, Daniela Krietsch, Matthew Heizler, Matthew E. Sanborn, Qing‐Zhu Yin

Meteoritics & Planetary Science
First Published: 2 March 2020

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“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.”