Mineralogical Institute, Faculty of Science, University of Tokyo
Department of Earth Sciences, Kobe University
National Institute of Polar Research
Geological Institute, Faculty of Science, University of Tokyo
抄録(英)
Seven diogenites, two eucritic polymict breccias and one pallasite have been identified in the Yamato-74 meteorites by the electron microprobe and single crystal X-ray diffraction techniques. The texture of Yamato-74010,-74011,-74013,-74037,-74097,-74136 and -74648 is unlike those of the other diogenites. It is not brecciated and texturally the pyroxene seems to have recrystallized to a granoblastic texture with small change in mineral composition. The chemical composition of the orthopyroxenes in these diogenites falls in the range (Ca)_<1.9> (Mg)_<75.1> (Fe)_<23.0> to (Ca)_<3.0> (Mg)_<71.0> (Fe)_<26.0>. The chemistry and textures of these diogenites are the same as those of the Yamato-6902 (b) diogenite previously reported. These Yamato diogenites may represent fragments of the same fall. Yamato-74159 is a polymict breccia which contains mineral and lithic clasts common to eucrites. The Yamato-74450 eucrite shows a variolitic texture, indicating a rapid solidification near the surface of its parent body. A brecciated part containing a pigeonite crystal with augite lamellae is also found in small amounts. The pyroxene trends of Yamato-74450 resemble those of the Pasamonte eucrite. The Yamato-74044 pallasite is the only stony-iron meteorite among the Yamato collection. A preliminary examination of the Yamato-75 meteorites identified one iron-rich diogenite and two eucritic polymict breccias. Yamato-75032 is the most Fe-rich of any known diogenite.
雑誌書誌ID
AA00733561
雑誌名
Memoirs of National Institute of Polar Research. Special issue
A Preliminary Mineralogical Examination of the Yamato-74 Achondrites
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KJ00000011859
(2.3MB)
概要
