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Yamato 691 meteorite (Y-691), Queen Fabiola Mts (Yamato Mts), Queen Maud Land (Dronning Maud Land), Eastern Antarctica, Antarctica

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Latitude & Longitude (WGS84): 71° 50' 54'' South , 36° 31' 9'' East
Latitude & Longitude (decimal): -71.84861,36.51944
Other regions containing this locality:Antarctic Meteorites
Non-native locality type:Meteorite
Meteorite Type:EH3 chondrite meteorite
Köppen climate type:EF : Ice cap climate

Enstatite Chondrite, high-iron [EH3; S4]
Found December 21, 1969; 715 g

Yamato-691 [Also, ‘Y-691’ or, earlier, ‘Yamato (a)’] is a moderately small, very primitive Enstatite Chondrite discovered somewhat accidentally on a Japanese expedition to Antarctica. As an Enstatite Chondrites Yamato-691 is characterized by (1) a dominant Enstatite lithology in chondrules, matrix, and inclusions, (2) accessory Fe-Ni metal and troilite, and (3) a number of minor very reduced and frequently very rare mineral phases. Relatively abundant niningerite plus perryite indicate that Y-691 belongs to the EH (high iron) chemical group of Enstatite chondrites. Sharply defined chondrules, glass, variable pyroxene, and unequilibrated constituents (e.g., the simultaneous presence of silica and olivine) further indicate that Y-691 belongs to the petrologically primitive EH3 type. EH3s are the most common type of EH chondrite and, indeed, ten EH3 chondrites [as of April 2014] are more massive than Y-691. However, Y-691 seems to contain within its small inclusions and assemblages an even richer brew of mineralogical diversity than most other members of its type. A 1987 symposium in Tokyo was dedicated to Y-691 unusual characteristics (several references below are provided below).

Among Y-691’s various chondrules and sometimes glassy inclusions are transparent silica-rich chondrules and dark silicate-containing inclusions frequently rich in refractory minerals. A few tiny pre-solar components have also been found. A new mineral, Wassonite, has been found amidst an unusual assemblage of N-containing mineral phases. Strong pre-terrestrial shock [S4] has left also its mark. While these features are not unique per se, Y-691 appears to contain a larger component of primitive components than we might expect. Yamato-691 is one more example of the fascinating complexities sometimes found in some very small meteorites.

Mineral List

28 valid minerals. 1 (TL) - type locality of valid minerals.

Meteorite/Rock Types Recorded

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- Makoto Shima, Masako Shima and H. Hintenberger (1973): Earth and Planetary Science Letters 19, 246-249.

Ikeda, Y. (1988) Petrochemical study of the Yamato-691 enstatite chondrite (EH3) I: Major element chemical compositions of chondrules and inclusions, Proceedings of the NIPR Symposium, No. 1, 3-13. (March1988)

Ikeda, Y. (1988): Petrochemical study of the Yamato-691 enstatite chondrite (EH3) II: Descriptions and mineral compositions of unusual silicate-inclusions. Proceedings of the NIPR Symposium on Antarctic Meteorites 1, 14-37. [http://ci.nii.ac.jp/naid/110000029852/en/]

El Gorsey, A., Yabuki, H., Ehlers, K., Woolum, D. & Pernicka, E. (1988). Qingzhen and Yamato-691: A tentative alphabet for the EH chondrites. Proceedings NIPR Symposium Antarctic Meteorites 1, 65-101.

Brearley, A. J. & Jones, R. H. (1998): Chondritic Meteorites. In: Planetary Materials (Papike, J. J., Editor): Chapter 3, 398 pages. Mineralogical Society of America: Washington, DC, USA.

Weisberg, M. K., Kimura, M., McCoy, T. J. & Lin, Y. (2005). Olivine and the Thermal History of the E Chondrite Parent Body (abstract): Lunar and Planetary Science Conference XXXVI: abstract no.1420. (March 2005)

Nakamura-Messenger et al., (2011) The Formation of Wassonite: A New Titanium Monosulfide Mineral in the Yamato 691 Enstatite Chondrite: Workshop on Formation of the First Solids in the Solar System: LPI Contribution No. 1639, p. 9091. (Nov 2011)

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