Telakoast 001        27.261583° N, 5.357341° E

Tamanghasset, Algeria

Find: 2020 Nov

Classification: Carbonaceous chondrite (C3, ungrouped)

History: Found near Daïet Djerdjir, Algeria, in November 2020.

Physical characteristics: A single very fresh, black fusion-crusted stone (60 g) with one shield-like surface.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL; L. Garvie, ASU) The specimen consists of small, well-formed chondrules (apparent diameter 420±320 µm, N = 20) plus zoned olivine fragments set in a very fine grained matrix (black in thin section). Olivine compositions exhibit a wide range in Fa content with a somewhat bimodal distribution. No CAI were found. Accessory phases identified by electron microprobe analysis are Fe sulfide, FeNi sulfide and kamacite (partly replaced by very fine grained mixtures of indeterminate Fe-S-P-O-bearing phases). X-ray diffraction analysis confirms that olivine has two discrete compositions (one near forsterite and one near Fa₁₂ or higher); clinoenstatite, calcite, pyrrhotite, pentlandite and maghemite were also identified, but reflections for serpentine or smectite are absent.

Geochemistry: Olivine (Fa_31.6±28.5, range Fa_0.8-81.3, N = 8; Cr₂O₃ in ferroan olivine 0.09-0.45 wt.%, mean 0.25 wt.%, sd 0.14 wt.%, N = 6), low-Ca pyroxene (Fs_15.1±17.0Wo_1.9±1.7, range Fs_2.4-34.5Wo_0.8-3.8, N = 3), pigeonite (Fs_1.7Wo_11.9), aluminous diopside (Fs_2.4±1.8Wo_41.7±1.1, range Fs_1.1-3.7Wo_42.4-40.9, Al₂O₃ 4.6-4.8 wt.%, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O -4.148, -6.412, -8.012, -4.481, -6.945; δ¹⁸O 2.152, -0.796, -3.151, 0.750, -1.880; Δ¹⁷O -5.284, -5.991, -6.348, -4.877, -5.953 per mil (all data linearized).

Classification: Carbonaceous chondrite (C3-ungrouped). Oxygen isotopic compositions are significantly displaced from the CCAM trend to more negative δ¹⁷O coupled with higher δ¹⁸O values, implying that this is an ungrouped anhydrous carbonaceous chondrite specimen.

Specimens: 12.6 g including one polished thin section at UWB; 2.1 g, PSF; remainder with Mr. B. Hoefnagels.