Northwest Africa 14139 (NWA 14139)

(Northwest Africa)

Purchased: 2021 Apr

Classification: Carbonaceous chondrite (C3, ungrouped)

History: Purchased by Ziyao Wang in April 2021 from a dealer in Ouargla, Algeria.

Physical characteristics: A batch of many fine grained, friable black stones (total weight 192 g).

Petrography: (A. Irving, UWS and P. Carpenter, WUSL; L. Garvie, ASU) Optical microscopy coupled with electron microprobe analyses and imaging reveal the presence of very small, glass-bearing chondrules (apparent diameter 270±130 µm, N = 20), mineral fragments and AOA set in an ultra fine-grained matrix (~50 vol.%, opaque in thin section) containing iron sulfide, pentlandite, low-Ti chromite and minor secondary calcite. No CAI were observed. The powder X-ray diffraction profile is dominated by intense reflections for olivine (dominated by magnesian compositions), clinoenstatite, pyrrhotite, pentlandite and calcite. These reflections sit on a medium intensity, broad scattering peak centered around 33° 2theta (Cu K alpha), indicative of amorphous material. Although distinct reflections for phyllosilicates are absent, there is a broad low-angle scattering centered around 13 Å.

Geochemistry: Olivine (Fa_29.7±23.9, range Fa_0.8-65.4, N = 6), low-Ca pyroxene (Fs_2.2±2.5Wo_2.5±1.9, range Fs_0.7-6.6Wo_1.0-4.7, N = 5), augite (Fs_13.7±17.7Wo_39.4±2.3, range Fs_1.2-26.2Wo_41.0-37.7, N = 2). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively, δ¹⁷O -4.933, -5.739, -1.985; δ¹⁸O 1.002, 0.221, 4.810; Δ¹⁷O -5.462, -5.856, -4.525 per mil (all data linearized).

Classification: Carbonaceous chondrite (C3 ungrouped). This material resembles Telakoast 001 in many respects, including textures, mineralogy, mineral compositions and oxygen isotopes (plotting in the same region below the CCAM trend).

Specimens: 24 g including one polished thin section at UWB; remainder with WangZ.