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Yamato 791201
Basic information Name: Yamato 791201
     This is an OFFICIAL meteorite name.
Abbreviation: Y-791201
Observed fall: No
Year found: 1979
Country: Antarctica [Collected by National Institute of Polar Research, Japan]
Mass:help 9.6 g
NHM Catalogue:  5th Edition  (2000)  Diogenite
NIPR Catalogue:  2000 Edition  (2000)  Diogenite-B
MetBase:  v. 7.1  (2006)  Diogenite
Recommended:  Diogenite    [explanation]

This is 1 of 481 approved meteorites classified as Diogenite.   [show all]
Search for other: Achondrites, Diogenites, and HED achondrites
Writeup from MN J7(1):

Y-791201, 81-1: Diogenite

(genomict cumulate eucrites with diogenitic components)

          This specimen is a polymict or genomict cumulate eucrite with a small diogenitic component, or a norite-pyroxenite breccia, but it is texturally similar to the Y-75032-type achondrites. It is not a howardite because neither basalt nor olivine are present. Subangular lithic clasts and fragments of shocked pyroxene and plagioclase are set in a very dark brown glassy matrix with chromite, troilite, and more comminuted minerals. Some lithic clasts are composed of pyroxene, plagioclase, and minor chromite and troilite, but some pyroxene-only rocks and plagioclase-poor rocks are present. Devitrified, shocked plagioclase fragments are more abundant than those in other Y-75032-type achondrites. The modal abundance of plagioclase is 25%.

          The Mg/(Mg+Fe) atomic ratios of pyroxene range from 0.7 to 0.5 and cover the entire range between Fe-rich diogenites and cumulate eucrites. The An contents of plagioclase range from 86 to 93. One large noritic clast, 4.1 x 1.5 mm in size, texturally similar to the Moama cumulate eucrite, is attached to one side of the thin section. It consists of 36% orthopyroxene, 61% plagioclase (An89), and 3% blebby augite. Round pyroxene grains about 1 mm in diameter with blebby inclusions of augite aligned along one crystallographic direction may be low-Ca inverted pigeonite. The bulk pyroxene composition Ca7Mg58Fe35 is intermediate in Mg/(Mg+Fe) ratio between the pyroxene fragments in the matrix. The Mg/(Mg+Fe) ratios of many other small lithic clasts, with approximately half pyroxene and half plagioclase, are a little above 0.5. Plagioclase is shocked, but only a part of the crystal is maskelynite.

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References: Published in Meteorites news : Japanese collection of Antarctic meteorites / Meteorites news : Japanese collection of Antarctic meteorites ,7(1),1-94 (1998-06)
Never published in the Meteoritical Bulletin
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     Catalogue of Meteorites:   (71° 30'S, 35° 40'E)
     Recommended::   (71° 30'S, 35° 40'E)

     This is 1 of 41908 approved meteorites from Antarctica (plus 3802 unapproved names)
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