Mineralogical Examination of the Yamato-75 Achondrites and Their Layered Crust Model

• Main Authors: Takeda, Hiroshi, Miyamoto, Masamichi, Ishii, Teruaki, Yanai, Keizo, Matsumoto, Yukio
• Language: English
• Published: 1979
• Subjects: Yamato; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/record/961/files/KJ00000011507.pdf

P(論文) One Fe-rich diogenite and two polymict breccias with eucritic composition have been identified in the Yamato-75 achondrites by the electron microprobe and single crystal X-ray diffraction techniques. The Yamato-75032 diogenite, a monomict breccia, contains a low-Ca inverted pigeonite with a chemical composition close to that of Binda, and a possible primary orthopyroxene. Yamato-75011 and -75015 are polymict breccias which contain mineral and lithic clasts common to eucrites. Binda-like pyroxene fragments were found in Yamato-75015,suggesting that it may represent a variety of materials expected from our layered crust model containing diogenite, Binda-type, Moore County-type, Juvinas-type and Pasamonte-type pyroxenes from bottom to top. Yamato-74659 may be classified as a weathered pyroxene-rich ureilite, which contains the most Mg-rich uninverted pigeonite. The exsolution and shock induced twinning were not observed. Yamato-74123 is another ureilite similar to Kenna. departmental bulletin paper