El Médano 301 classified as ‘ungrouped chondrite’
El Médano 301
classified as ungrouped chondrite with affinities to NWA 7135
“El Médano 301 ~24°51’S, ~70°32’W
Find: 2013 Nov 09
Classification: Ungrouped chondrite
History: A single stone was found in the Atacama desert by Pierre Rochette on November 4, 2013.
Physical characteristics: A single brown stone without fusion crust
Petrography: Closely packed, well-defined chondrules with average apparent diameter 490±330 μm (N=60). Main minerals are olivine (forsterite), enstatite, diopside, chlorapatite, chromite, troilite, kamacite, taenite. Metal and sulfides have been extensively replaced by weathering products.
Geochemistry: Olivine Fa3.9±0.4 (Fa3.6-5.0, PMD 5.5%, FeO/MnO=8.0±1.3, N=10), Cr2O3 0.02±0.03 wt%. Orthopyroxene Fs13.1±5.7 (Fs6.6-21.0, PMD=40%, N=11). Oxygen isotopic composition (J. Gattacceca, C. Sonzogni, CEREGE) is δ17O = 3.58 ‰, δ18O = 5.38 ‰, Δ17O = 0.78‰ (analysis of one 1.5 mg sample of hand-picked separated silicates after acid cleaning). Magnetic susceptiblity log χ (× 10-9 m3/kg)=4.62.
Classification: Chondrite-ung. With Fa3.6-5.0, this meteorite has affinities with NWA 7135 that has Fa4.8-6.3 and similar oxygen isotope composition, although NWA 7135 is more reduced, with occurrence of schreibersite and oldhamite.
Specimens: Polished section, main mass and type specimen at CEREGE”