El Médano 350 (EM 350)        ~24°51’S, ~70°30’W

Antofagasta, Chile

Find: 2013 Nov 10

Classification: HED achondrite (Eucrite, polymict)

History: The meteorite was found in the Atacama desert by Jihed Dridi on 2013 November 10

Physical characteristics: The stone was found broken in three fitting pieces. It is an almost full oriented stone with fresh glassy fusion crust and flow lines. Cut surface reveals a grey brecciated interior.

Petrography: (J. Gattacceca CEREGE, A. Jambon UPMC) Brecciated magmatic rock composed mostly of plagioclase and pyroxenes, with accessory chromite, silica, olivine, ilmenite, troilite, metal. There three main lithologies: 1) a macroscopically light lithology with fractured ophitic texture and plagioclase and pyroxene grain size to 600 μm; 2) a macroscopically darker lithology with finer grains (typical size 150 μm), more metal and evidence for strong shock; 3) a cataclastic lithology with large plagioclase and pyroxene clasts (to 5 mm), and both exsolved (augite exsolution in pigeonite) and zoned pyroxenes, set in a comminuted matrix of the same minerals. In the dark lithology, brecciation has obliterated the original magmatic teture. Shock evidence include the presence of melt pockets with quenched texture and shock darkening by small metal and sulfide blebs.

Geochemistry: Low-Ca pyroxenes Fs_29.8-59.1, average Fs_47.1±11.1Wo_4.5±1.2, FeO/MnO 30.9±3.4 (N=11). Plagioclase An_89.1±4.0Ab_10.5±4.0Or_0.4±0.2 (N=9). One olivine from a quenched clast is Fa_84.9. Magnetic susceptibility log χ (× 10^-9 m³/kg) = 3.79 is much higher than the average eucrite (log χ (× 10^-9 m³/kg) = 2.95±0.30, measured on 70 falls by Rochette et al. 2009), pointing to an anomalous rich metal content at the level of the Brient polymict eucrite.

Classification: Achondrite (polymict eucrite, metal-rich). Minimal weathering.

Specimens: Type specimen and main mass at CEREGE.