Calama 450        22°18.89’S, 68°46.93’W

Antofagasta, Chile

Find: 16 Mar 2021

Classification: Ordinary chondrite (type 4)

History: one individual meteorite was found in a hot desert of Chile

Physical characteristics: a sample of meteorite has a brown fusion crust.

Petrography: M. A. Ivanova, C.A. Lorenz (Vernad) The meteorite has a chondritic texture and contains chondrules and chondrule fragments. Chondrules (diameter 619±273 µm, N=75) are represented by RP, PP, GP and rare GOP types. Most of the chondrules are intensively fractured. The silicates in the chondrules are full of tiny opaque inclusions. Two small CAIs occur in the meteorite. The chondrules are embedded in a devitrified melt containing tiny inclusions of opaque phases. This material does not contain any clasts or fragments. Melt pockets are present. Olivine has planar fractures and undulatory extinction indicating a shock stage S3. The fractures propagated across the rock and along the interchondrule spaces are filled with Fe,Ni hydroxide (13 vol.%) with the relics of Fe,Ni metal (0.9 vol.%). Carbonate inclusions occurs in the hydroxide veinlets. Due to more than 95 vol.% of metal is replaced by Fe,Ni hydroxide the weathering grade is W4. Petrological type is 4, since olivine is homogeneous and chondrules are well delineated.

Geochemistry: Mineral compositions and geochemistry: M. A. Ivanova (Vernad), N.G. Zinovieva (MSU). Olivine: Fa _0.72±0.59 (N=32), PMD-0.5%; orthopyroxene: Fs_1.07±1.64Wo_2.62±1.44 (N=35), Fe/Mn = 3.67±2.36 (N=35), however, more ferrous low-Ca pyroxene exists: up to Fs_11.88Wo_3.47. Ca-pyroxene is represented by pigeonite and augite. Diopside (Wo_45.8±0.9Fs_2.6±1.9) occurs in melilite-spinel CAIs and some chondrules; plagioclase has variable composition (An_29.6±9.0Ab_70.3±9.0); Fe,Ni-metal contains (wt.%) Si - 0.08±0.02, Ni - 5.8±0.5, Co - 0.51±0.02; sulfide is represented by Cr-rich troilite, daubreelite and very tiny oxidized grains of alabandite and probably oldhamite. Oxygen isotopic composition (J. Gattacceca, C. Sonzogni, D. Au Yang, CEREGE) from analysis of one acid-washed 1.58 mg aliquot of a powdered 102 mg bulk sample is δ¹⁷O=4.134, δ¹⁸O=6.518, Δ¹⁷O=0.745 (all ‰, slope 0.52, analytical uncertainties 0.115, 0.062, and 0.005‰, respectively).

Classification: based on homogeneous and very reduced composition of olivine (Fa_0.72±0.59), low content of Si in low-Ni metal (0.08±0.02 wt.%) presence of CAIs, different sulfides and oxygen isotopic compositions close to LL group, this meteorites is a very reduced ungrouped ordinary chondrite with melted matrix.

Specimens: a fragment of meteorite (1.7 g) and 1 polished section are deposited in Vernad.