Mineralogical Examination of the Allan Hills No.5 Meteorite

• Main Authors: Miyamoto, Masamichi, Takeda, Hiroshi, Yanai, Keizo, Haramura, Hiroshi
• Language: English
• Published: 1979
• Subjects: Allan Hills; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/record/959/files/KJ00000011505.pdf

P(論文) Electron microprobe studies have been made of pyroxenes from the Allan Hills No. 5 meteorite. This meteorite shows the brecciated texture and was identified as 'eucritic polymict breccia'. Representative pyroxenes in this meteorite can be classified into four groups : (A) Pyroxenes which have a chemically uniform core with a Fe-rich rim. (B) Pyroxenes which show both the Mg-Fe chemical zoning and the exsolution texture. (C) Pyroxene which consists of a portion which has a uniform core with a Fe-rich rim like Type (A) and another portion which shows the exsolution texture and the Mg-Fe chemical zoning like Type (B) within a single grain. (D) Juvinas-like pyroxenes which show the fine exsolution texture with the uniform chemical composition. By the discovery of these pyroxenes in this meteorite, it was proved that the pyroxenes contained in eucritic polymict breccias have a close genetic relationship. Based on the mineralogical examination of these pyroxenes and the surface brecciation process of our proposed layered crust model for an achondrite parent body, we suggested that the eucritic polymict breccia is a good candidate for its surface material. departmental bulletin paper