Sarir Tazirbu 001 (ST 001)        25.845°N, 20.698°E

Al Kufrah, Libya

Purchased: 2020 Nov

Classification: Carbonaceous chondrite (C2, ungrouped)

History: Two small black, partially fusion-crusted stones found together in eastern Libya ~40 km NW of Tazirbu were purchased from the finder by Mbark Arjdal in November 2020.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL; L. Garvie, ASU) Very small chondrules (apparent diameter 310±110 µm, N = 21) composed mainly of forsterite, enstatite, aluminous diopside and minor pigeonite together with strongly zoned angular olivine grains are set in a very fine grained matrix (~50 vol.%, almost opaque black in thin section). Accessory phases identified by electron microprobe analysis include iron sulfide, pentlandite, kamacite, cronstedtite and serpentine. No CAI were observed. The powder X-ray diffraction pattern shows reflections for serpentine and a broad low-angle reflection consistent with smectite. The pattern is dominated by strong reflections for olivine, dolomite, magnetite, maghemite, clinoenstatite, pyrrhotite, pentlandite and minor calcite. These reflections sit on a broad, but intense scattering centered around 32° 2theta (Cu K alpha), consistent with amorphous scattering.

Geochemistry: Olivine (Fa_27.9±19.6, range Fa_1.0-54.5, N = 9), enstatite (Fs_1.7±0.6Wo_2.5±1.6, range Fs_1.3-2.1Wo_1.1.4-3.6, N = 2), pigeonite (Fs_5.4Wo_7.0), subcalcic augite (Fs_34.0Wo_30.4), aluminous diopside (Fs_1.2±0.1Wo_40.5±2.5, range Fs_1.1-1.3Wo_42.3-38.7, Al₂O₃ 3.7-7.9 wt.%, TiO₂ 0.8 wt.%, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O -2.677, -5.853, -2.810; δ¹⁸O 4.039, -1.154, 3.537; Δ¹⁷O -4.809, -5.244, -4.677 per mil (all data linearized).

Classification: Carbonaceous chondrite (C2-ungrouped). Although this specimen shares some attributes with ungrouped C2 chondrite Telakoast 001, including very similar textures, some mineral compositions, and oxygen isotopes plotting in the same region below the CCAM trend, the presence of minor serpentine and smectite sets it apart, and leads to an assignment of petrologic type 2.

Specimens: 6.7 g including one polished thin section at UWB; remainder with Mr. M. Arjdal.