Yamato 791197

Lunar Meteorite: Yamato 791197

Antarctica, Yamato Mountains




Four views of Yamato 791197. Note the vesicular fusion crust, as on other lunar meteorites that are regolith breccias. (Photos courtesy of the NIPR)

Yamato 79197 is a regolith breccia composed mainly of material from the feldspathic highlands. Notice that the matrix is as dark as meteorites containing much more volcanic material, such as Yamato 981031.

The scale to the left has millimeter tick marks.

Mass: 52.4
Type: feldspathic regolith breccia

from NIPR Meteorite Newsletter No. 7

Y-791197 is a polymict microbreccia containing clasts in a dark brown glassy matrix, similar to lunar anorthositic regolith breccias. Two or more types of clasts are observed in the thin section, such as polymineralic, monomineralic and melt clasts. Most of larger clasts are polymineralic, frequently composed of calcic plagioclase, olivine, and pyroxene; less commonly plagioclases, or plagioclases alone. Smaller clasts are mineral fragments dominantly plagioclases, with some pyroxenes and olivines, and melted lithic fragments. The clasts also show a variety of textures, including troctolitic, gabbroic, diabasic, basaltic and shock-melted glassy clasts. Most of them are more feldspathic than the HED achondrites. Y-791197 appears to be a regolith breccia with glass spherules and abundant clasts, especially feldspathic clasts, set in a dark brown glassy matrix. The PTS shows that recrystallized matrix breccias containing plagioclase fragments are the other abundant clasts. The matrix glass compositions scatter around those of the bulk rock and are similar to those of the Apollo 16 regolith breccias.

The poikilitic matrix texture is not as well developed as that observed in the Apollo 16 regolith breccias, and it is very fine-grained and can be designated them as micropoikilitic breccias. One clast (HPF) consists of dark yellowish brown to reddish brown iron-rich pyroxene, small amounts of plagioclase, fayalite, and dark mesostasis-like materials including fayalite, minor silica mineral and ilmenite. A poikilitic clast (PK1) clast has a texture with a few subround plagioclase crystals up to 0.2 mm in diameter set in a fine grayish poikilitic-like matrix. Fine-grained (up to 30 microns) olivine and pyroxene are rarely found in the matrix. The plagioclase compositions are calcic and the An contents range from 95 to 97. The Fa contents of olivine range from 36 to 49. Other small lithic clasts are: noritic and troctolitic anorthosites and shocked anorthosites. One clast (SA) consists of rounded euhedral pleonaste spinel enclosed in anorthite. This clast could be a fragment of spinel cataclasite.

More Information

Antarctic Meteorite Research Center | National Institute of Polar Research

Meteoritical Bulletin Database

Yamato 791197

Map

NIPR Location Map

References

Fukuoka T., Laul J. C., Smith M. R., Hughes S. S., and Schmitt R. A. (1986) Chemistry of Yamato-791197 Antarctic meteorite: Evidence for its lunar highlands origin. Mem. Nat. Inst. Polar Res., Spec. Iss. 41, 84-95.

Goodrich C.A. and Keil K. (1987) Mare basalts and other clasts in Yamato lunar meteorites Y-791197, -82192 and -82193. Mem. Nat. Inst. Polar Res., Spec. Iss. 46, 56-70.

Koeberl C. (1988) Trace element geochemistry of lunar meteorites Yamato-791197 and -82192. Proc. NIPR Symp. Antarct. Meteorites 1, 122-134. Nat. Inst. Polar Res., Tokyo.

Korotev R. L. (2005) Lunar geochemistry as told by lunar meteorites. Chemie der Erde 65, 297–346.

Korotev R. L., Jolliff B. L., Zeigler R. A., Gillis J. J., and Haskin L. A. (2003) Feldspathic lunar meteorites and their implications for compositional remote sensing of the lunar surface and the composition of the lunar crust, Geochim. Cosmochim. Acta 67, 4895–4923.

Lindstrom M. M., Lindstrom D. J., Korotev R. L., and Haskin L. A. (1986) Lunar meteorite Yamato-791197: A polymict anorthositic norite from the lunar highlands. Mem. Nat. Inst. Polar Res., Spec. Iss. 41, 58-75.

Nishiizumi K., Arnold J. R., Klein J., Fink D., Middleton R., Kubik P. W., Sharma P., Elmore D., and Reedy R. C. (1991) Exposure histories of lunar meteorites: ALHA81005, MAC81004, MAC81005, and Y791197. Geochim. Cosmochim. Acta 55, 3149-3155.

Ostertag R., Stöffler D., Bischoff A., Palme H., Schultz L., Spettel B., Weber H., Weckwerth G., and Wänke H. (1986) Lunar meteorite Yamato-791197: Petrography, shock history and chemical composition. Mem. Nat. Inst. Polar Res., Spec. Iss. 41, 17-44.

Palme H., Spettel B., Jochum K. P., Dreibus G., Weber H., Weckwerth G., Wänke H., Bischoff A., and Stöffler D. (1991) Lunar highland meteorites and the composition of the lunar crust, Geochim. Cosmochim. Acta 55, 3105-3122.

Sears D. W. G., Benoit P. H., Sears H., Batchelor J. D., and Symes S. (1991) The natural thermoluminescence of meteorites: III. lunar and basaltic meteorites, Geochim. Cosmochim. Acta 55, 3167-3180.

Sutton S. R. (1986) Thermoluminescence of lunar meteorites Yamato-791197 and ALHA-81005. Proc. 10th Symp. Antarctic Meteorites, Mem. Nat. Inst. Polar Res., Spec. Iss. 41, 133–139.

Takahashi K. and Masuda a. (1987) Two lunar meteorites, Yamato-791197 and –82192: REE abundances and geochronological dating, Mem. Nat. Inst. Polar Res., Spec. Iss. 46, 71–88. Nat. Inst. Polar Res., Tokyo.

Takaoka N. (1986) Noble gases in Yamato-791197: Evidence for lunar highland origin, Proc. 10th Symp. Antarctic Meteorites, Mem. Nat. Inst. Polar Res., Spec. Iss. 41, 124–132.

Vogt S., Fink D., Klein J., Middleton R., Dockhorn B., Korschinek G., Nolte E., and Herzog G. F. (1991) Exposure histories of the lunar meteorites: MAC88104, MAC88105, Y791197, and Y86032. Geochim. Cosmochim. Acta 55, 3157-3165.

Warren P. H. and Bridges J. C. (2004) Lunar meteorite Yamato-983885: A relatively KREEPy regolith breccia not paired with Y-791197 (abstract). In 67th Annual Meteoritical Society Meeting, abstract no. 5095.

Warren P. H. and Kallemeyn G. W. (1986) Geochemistry of lunar meteorite Yamato-791197: Comparison with ALHA81005 and other lunar samples. Mem. Nat. Inst. Polar Res. Spec. Iss. 41, 3-16. Nat. Inst. Polar Res., Tokyo.

Warren P. H. and Kallemeyn G. W. (1987) Geochemistry of lunar meteorite Yamato-82192: Comparison with Yamato-791197, ALHA81005, and other lunar samples. Mem. Nat. Inst. Polar Res., Spec. Iss. 46, 3-20.

Warren P. H. and Kallemeyn G. W. (1991) Geochemical investigations of five lunar meteorites: Implications for the composition, origin and evolution of the lunar crust. Proc. NIPR Symp. Antarct. Meteorites 4, 91-117. Nat. Inst. Polar Res., Tokyo.

Yanai K. and Kojima H. (1984) Lunar meteorite in Japanese collection of the Yamato meteorites (abstract). Papers Presented to the Ninth Symposium on Antarctic Meteorites, 42-43, National Institute of Polar Research, Tokyo.

Yanai K. and Kojima H. (1984) Yamato-791197: A lunar meteorite in the Japanese collection of Antarctic meteorites. Mem. Nat. Inst. Polar Res., Spec. Iss. 35, 18–34.

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Chemical Classification

Overview | Yamato 791197

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Prepared by:

Randy L. Korotev

Department of Earth and Planetary Sciences
Washington University in St. Louis

Please don't contact me about the meteorite you think you’ve found until you read this and this.

e-mail: korotev@wustl.edu

Last revised: 12-Dec-2006