Sierra Gorda 010        22°30.49’S, 69°07.65’W

Antofagasta, Chile

Find: 2017 Oct 20

Classification: R4-an

History: One individual meteorite (280 g) was found in the desert by T. V. Kryachko.

Physical characteristics: The meteorite has a dark-brown fusion crust and greenish-gray color.

Petrography: M. A. Ivanova (Vernad) Meteorite consists of POP, BO and OP chondrules, up to 0.7 mm and matrix; matrix/chondrule ratio is ~1; some chondrule boundaries are not clear; main minerals are olivine, plagioclase, pyroxene, sulfides (pentlandite, pyrrhotite), magnetite; acsessory minerals are ilmenite and spinel; Fe,Ni metal is absent. Magnetic susceptibility (J. Gattacceca, CEREGE) log χ (× 10^-9 m³/kg) = 4.28 is an order of magnitude higher than for the usual R chondrites, and indicate a magnetite content of ~4 wt%.

Geochemistry: Mineral compositions and geochemistry: M. A. Ivanova (Vernad, SI), V. V. Kozlov (Oxford Instruments OM & Gatan Inc., Moscow Office) Olivine: Fa_36.9±0.3 (N=42), NiO - 0.44 wt%, orthopyroxene: Fs_20.5±6.3Wo_0.9±0.5 (N=35); augite Fs_11.7±0.5Wo_43.4±0.8; diopside Fs_8.4±2.5Wo_46.5±0.5; magnetite is highly enriched in Cr₂O₃ (9.0 wt%, n=27), and TiO₂ (1.56 wt%) and Al₂O₃ (1.6 wt%); plagioclase composition is An_4.7-12.2Ab_83.3-89.0; sulfides are pyrrhotite and pentlandite; Oxygen isotopic compositions: (OU) after acid washing δ¹⁷O 5.684, 5.594; δ¹⁸O 5.005, 4.932; Δ¹⁷O 3.082, 3.029 (all per mil).

Classification: Chondrite, R4. The anomalous designation comes from the Fa content of olivine that is lower than in other R chondrites, and from the unusual and abundant magnetite enriched in Cr₂O₃ (up to 9.0 wt%) and TiO₂ (up to 1.56 wt%).

Specimens: One sample wheighing 64.9 g and a thin section are deposited in Vernad. Main mass with Mr. T. V. Kryachko ([email protected]).