Evidence for a multilayered internal structure of the chondritic acapulcoite-lodranite parent asteroid. (1st December 2018)

• Record Type: Journal Article
• Authors: Li, Shijie; Yin, Qing-Zhu; Bao, Huiming; Sanborn, Matthew E.; Irving, Anthony; Ziegler, Karen; Agee, Carl; Marti, Kurt; Miao, Bingkui; Li, Xiongyao; Li, Yang; Wang, Shijie
• Is Part Of: Geochimica et cosmochimica acta. Volume 242(2018)
• Page Start: 82
• Page End: 101
• Publication Date: 2018-12-01
• Subjects: GRV 020043 -- Acapulcoite -- Lodranite -- Oxygen isotope -- Chromium isotope; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2018.09.004
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: We report a petrography, mineral chemistry, oxygen and chromium isotopic study of Grove Mountains (GRV) 020043 together with a subset of other acapulcoites and lodranites. GRV 020043 is a petrologic type 4 chondrite, with chondrules of diverse types and sizes, and is composed of low-Ca pyroxene (40 vol.%), olivine (24 vol.%), diopside (8 vol.%), plagioclase (10 vol.%), Fe-Ni metal (kamacite and taenite), troilite and some accessory minerals (chromite and apatite). The olivine in GRV 020043 has an average fayalite content (Fa) of 10.7 mol.% with the low-Ca pyroxene having an average ferrosilite content (Fs) of 10.8 mol.%. The whole rock oxygen isotopic composition of GRV 020043 is +3.226 ± 0.267‰, +0.797 ± 0.131‰, and −0.927 ± 0.017‰ for δ 18 O, δ 17 O, and Δ 17 O, respectively, with a bulk chromium isotopic compositions of ε 54 Cr = −0.48 ± 0.10. These characteristics of GRV 020043 are different from all established or ungrouped chondrites but agree with those of the acapulcoite-lodranite clan. We therefore suggest that GRV 020043 represents the chondritic precursor of acapulcoite-lodranite parent body. The similarity of bulk oxygen and chromium isotopic compositions among GRV 020043, Acapulco, Northwest Africa (NWA) 468 (metal-rich lodranite), NWA 8118 (lodranite), NWA 8287 (acapulcoite), and NWA 8422 (lodranite) indicates that they originated from a common oxygen and chromium reservoir in the protoplanetary disk or may have derived from a parent body with a differentiated multilayer structure.