Evidence for a multilayered internal structure of the chondritic acapulcoite-lodranite parent asteroid
© 2018 Elsevier Ltd 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 δ18O, δ17O, and Δ17O, respectively, with a bulk chromium isotopic compositions of ε54Cr = −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.
Publication Source (Journal or Book title)
Geochimica et Cosmochimica Acta
Li, S., Yin, Q., Bao, H., Sanborn, M., Irving, A., Ziegler, K., Agee, C., Marti, K., Miao, B., Li, X., Li, Y., & Wang, S. (2018). Evidence for a multilayered internal structure of the chondritic acapulcoite-lodranite parent asteroid. Geochimica et Cosmochimica Acta, 242, 82-101. https://doi.org/10.1016/j.gca.2018.09.004