Yamato 691 meteorite, Queen Fabiola Mts, Queen Maud Land, Eastern Antarctica, Antarcticai

Regional Level Types
Yamato 691 meteorite	Meteorite Fall Location
Queen Fabiola Mts	Mountain Range
Queen Maud Land	Region
Eastern Antarctica	Region
Antarctica	Continent

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.

Other Regions, Features and Areas containing this locality

References