Mineralogy of Antarctic aubrites, Yamato-793592 and Allan Hills-78113: Comparison with non-Antarctic aubrites and E-chondrites

• Main Authors: Kimura, Makoto, Lin, Yang-Ting, Ikeda, Yukio, Goresy, Ahmed EL, Yanai, Keizo, Kojima, Hideyasu
• Language: English
• Published: National Institute of Polar Research 1993
• Subjects: Antarctic; The Antarctic; Yamato; Allan Hills; Antarc*
• Online Access: https://nipr.repo.nii.ac.jp/record/4610/files/KJ00000036416.pdf; https://doi.org/10.15094/00004610; https://nipr.repo.nii.ac.jp/records/4610

P(論文) Two Antarctic aubrites, Yamato (Y)-793592 and Allan Hills (ALH)-78113,were mineralogically studied, for comparison with minerals in non-Antarctic aubrites and enstatite chondrites. The Antarctic aubrites are breccias consisting of coarse-grained enstatite fragments and fine-grained matrix. ALH-78113 has 200-300μm dark clasts that are fine-grained aggregates of silicate and opaque minerals. FeO-rich pyroxene (up to Fs_<21>) occurs in the dark clasts. One dark clast has K-feldspar. These dark clasts seem to be exotic inclusions with distinct mineralogy. Daubreelite in the two Antarctic and non-Antarctic aubrites is lower in Zn than those in EH3-5 chondrites. This reflects the depletion of volatile elements in aubrites. Hydrated Na-Cr-sulfides were also found. Djerfisherite is a common accessory mineral in aubrites. It is characterized by low contents of Cu and Na, and high content of Ni, in comparison to djerfisherite in EH3-5 chondrites. Y-793592 has many roedderite grains. The occurrences of roedderite, Na-Cr-sulfides and djerfisherite in aubrites suggest that Al_2O_3 relative to alkali elements may have been fractionated during nebular or magmatic process. departmental bulletin paper