DaG 647

Monomict, recrystallized noncumulate
(Main Group–Nuevo Laredo trend)

standby for dag 647 photo
Found Winter 1996/97
27° 10′ N., 16° 08′ E.

An unusual 1,425 g oriented basaltic meteorite was found in the Libyan Sahara Desert and classified after extensive work as a new type of eucrite by Hiroshi Takeda et al.. It was submitted to the Nomenclature Committee and designated Dar al Gani 647.

The pyroxene and plagioclase in the matrix are recrystallized to a fine-grained granoblastic crystalline texture, which masks the original fragmental texture commonly observed in other monomict eucrites. Dusty pyroxene crystals caused by the presence of chromite and ilmenite are similar to those found in other monomict eucrites and were probably present before the recrystallization phase. A rare silica mineral has also been identified.

In light of its unique mineralogy and textures, DaG 647 appears to have experienced a two-stage thermal history followed by rapid cooling. The initial brecciation and metamorphism occurred early in the crustal evolution of the eucrite parent body, probably 4 Vesta. During this initial metamorphism, the dusty pyroxenes that are characteristic of monomict eucrites were produced. Based on the homogeneous composition of the plagioclase crystals, usually identified only with cumulate eucrites, it can be inferred that DaG 647 later experienced recrystallization at high temperatures (~980°C) followed by an extensive and prolonged annealing phase which homogenized the plagioclase. It was then rapidly cooled (by excavation?) without further shock.

Dar al Gani 647 has a CRE age of ~25 m.y., similar to that of DaG 480, but also an age that references a cluster of HED meteorites that reflects a possible major impact on their parent body. Dar al Gani 647 might be paired with DaG 567. The specimen of DaG 647 pictured above is a 0.6 g very thin partial slice with some remnant fusion crust.

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