Calama 023        22°28.050’S, 68°38.786’W

Antofagasta, Chile

Find: 19 Oct 2017

Classification: Ordinary chondrite (H6)

History: Meteorite (284.04 g) was found 19 October 2017 by the UrFU meteorite expedition-2017 in Chile (Pastukhovich A.Yu., Larionov M.Yu., Kruglikov N.A., Kolunin R.N.) near Chiu-Chiu, Calama region.

Physical characteristics: Total mass is 284.04 g. The meteorite has roughly rounded shape. Exterior of the stone is desert polished. The surface and interior of the meteorite is light to dark brown in color due to Fe-hydroxides. No fusion crust was observed.

Petrography: Classification (Victor V. Sharygin, SIGM and UrFU). Very rare chondrules in a coarse recrystallized matrix. Chondrules are poorly delineated and their sizes vary from 200 µm to 2 mm. The largest chondrules (1-2 mm) are visible macroscopically and represented by PO, POP and RP textural types. They mainly consist of olivine, low-Ca-pyroxene and plagioclase, diopside, and ±chromite and blebs of troilite and FeNi-metal. Olivine, low-Ca-pyroxene and plagioclase are main minerals in matrix. Clinopyroxene, chromite, ilmenite and merrillite (50-300 µm) occur locally in the matrix, chlorapatite was not observed. Large olivine grains from matrix and POP chondrules may contains partially crystallized (silicate-melt?) inclusions (low-Ca-pyroxene + diopside + plagioclase/glass + troilite). Plagioclase grains in the matrix are larger than 50 µm, indicating a petrologic type of 6 for the meteorite. The absence of opaque shock veins and weak undulatory extinction and irregular fractures in olivine indicate a shock stage of S2. Majority of grains of FeNi metal (kamacite, taenite, tetrataenite, up to 1.5 mm) and troilite (100-500 µm) are fresh. Pentlandite (±Ni-rich pyrrhotite, up to 50 µm) is rare in troilite on the contact with kamacite. In addition, alabandite + Ni-rich pyrrhotite (?) association (3x10 µm) was found in a kamacite-hosted troilite bleb (70 µm). Grains of copper (up to 5 µm) were observed in a kamacite-taenite-tetrataenite-troilite aggregate. Weathering products (goethite, Fe-Ni-Cl-hydroxide and other Fe-Ni-hydroxides, Fe-S-hydroxide) occur as in situ partial alteration of FeNi-metals and troilite and fill microfractures in minerals from matrix and chondrules (weathering grade – W2). The association of trevorite + akaganeite is common as an alteration product of Ni-rich metal grains (taenite or kamacite + taenite + tetrataenite). Rare Fe-Ni-hydroxides veins are crosscut the meteorite sample.

Geochemistry: EDS-WDS analyses (Victor V. Sharygin, SIGM and UrFU). The primary chondrite paragenesis includes olivine Fa_19.44±0.18 (N=36), orthopyroxene Fs_17.28±0.35Wo_1.45±0.14 (N=36), plagioclase Ab_82.5An_11.8Or_5.7 (n=10), Cr-bearing clinopyroxene En_47.4Fs_7.0Wo_45.6 (N=8, Cr₂O₃ – 0.83 wt.%), chromite Crt_81.5Spl_13.9 (N=16), ilmenite Ilm_79.4Gk_10.9 (N=10), merrillite, and FeNi-metals. Merrillite is poor in FeO (0.4-0.8 wt.%, N=14). Composition of metals and sulfides (in wt.%): kamacite (N=27) – Fe 92.83±0.31, Ni – 6.73±0.13, Co – 0.44±0.05; taenite (N=12) – Fe 75.44, Ni 24.26, Co 0.28; tetrataenite (N=14) – Fe 47.24, Ni 52.59, Co 0.14; pentlandite (N=5) – Fe 45.99, Ni 20.67, Co 0.27, S 33.05; alabandite (N=2) – Mn 53.45; Fe 9.12, Ni 1.09, Co 0.14, S – 36.28.

Classification: Ordinary chondrite. H6, S2, W2.

Specimens: 249.36 g sample – UrFU; 27.25 g sample and thin section – SIGM.