Calama 008        22°27’32.7" S, 68°39’12" W

Antofagasta, Chile

Find: 2017 Oct 19

Classification: Ordinary chondrite (L6)

History: Meteorite (11.23 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 11.23 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 (V.V. Sharygin, SIGM and UrFU). Petrographic observation of a polished thin section shows very rare chondrules in a coarse-middle recrystallized matrix. Such chondrules are very poorly delineated and their sizes vary from 500 µm to 3 mm. They have porphyritic texture and mainly consist of olivine, low-Ca-pyroxene and plagioclase, and ± diopside, chromite and blebs of troilite and FeNi-metal. Chromite-plagioclase segregation (300 µm, chondrule ?) was also observed in the matrix. Olivine, low-Ca-pyroxene and plagioclase are main minerals in matrix. Plagioclase grains are larger than 50-100 µm. This indicates petrologic type 6. Undulatory extinction and irregular fractures in olivine, as well as the absence of opaque shock veins and melt pockets, indicate a shock stage of S2. Majority of grains of FeNi metal (kamacite, taenite, rarely tetrataenite, up to 500 µm) and troilite (200-500 µm) are fresh. Weathering products (goethite and other Fe-Ni-hydroxides) occur as in situ partial alteration of FeNi-metals and troilite and fill microfractures in minerals from matrix and chondrules (weathering grade – W2). Clinopyroxene, chromite, chlorapatite and merrillite (200-400 µm) occur locally in the matrix. Single inclusion (5 µm) of molybdenite was found in troilite grain.

Geochemistry: EDS-WDS analyses (V. V. Sharygin, SIGM and UrFU). The primary chondrite paragenesis includes olivine Fa_25.59±0.50 (N=27), orthopyroxene Fs_21.72±0.28Wo_1.61±0.21 (N=22), plagioclase Ab_83.5An_10.8Or_5.7 (N=23), Cr-bearing clinopyroxene En_45.3Fs_8.6Wo_46.1 (N=6), chromite Crt82.3Spl12.4 (N=16), chlorapatite, merrillite and FeNi-metals. Chlorapatite contains F (up to 0.5 wt.%); Cl – 5.30 wt.% (N=3). Merrillite is poor in FeO (0.6-0.7 wt.%). Composition of metals (in wt.%): kamacite (N=9) – Fe 93.71±1.55, Ni – 5.39±1.01, Co – 0.97±0.17; taenite (N=17) – Fe 68.28±4.53, Ni 31.24±4.67, Co 0.50±0.09; tetrataenite (N=3) – Fe 49.22, Ni 50.29, Co 0.33. Fe-Ni-hydroxides sometimes contain 22.6-38.3 wt.% NiO.

Classification: Ordinary chondrite. L6, S2, W2. In chemical composition of olivine and low-Ca pyroxene this meteorite seems to be similar to Calama 006.

Specimens: 8.4 g cut-off – UrFU; 1.25 g cut-off and thin section – SIGM.