Unique achondrite Northwest Africa 11042: Exploring the melting and breakup of the L chondrite parent body. (2nd March 2020)

• Record Type: Journal Article
• Authors: Váci, Zoltán; Agee, Carl B.; Humayun, Munir; Ziegler, Karen; Asmerom, Yemane; Polyak, Victor; Busemann, Henner; Krietsch, Daniela; Heizler, Matthew; Sanborn, Matthew E.; Yin, Qing‐Zhu
• Is Part Of: Meteoritics & planetary science. Volume 55:Number 3(2020)
• Page Start: 622
• Page End: 648
• Publication Date: 2020-03-02
• Subjects: Meteorites -- Periodicals; Planetology -- Periodicals; 523.4
• DOI: 10.1111/maps.13456
• Languages: English
• ISSNs: 1086-9379

Abstract

Abstract: 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.