Northeast Africa 049 (NEA 049)

Sudan

Find: 2021

Classification: HED achondrite (Diogenite, olivine)

History: Cascadia received 6 pieces totaling 112.3 g from Mustapha Oulkouch with images of the uncut 22.5 kg stone. Mr. Oulkouch was told that the stone was found in 2021 in Sudan.

Physical characteristics: Physical Characteristics: None of the pieces received by Cascadia show any evidence for a fusion crust. All of the pieces are mostly composed of a light-yellow-orange-colored matrix containing a sparse mixture of light gray and black clasts/grains.

Petrography: (M. Hutson, A. Ruzicka, Cascadia): A coarse-grained, heavily-fractured olivine-orthopyroxenite (referred to as clast) comprises slightly less than one-third of the thin section. Coarse-grained orthopyroxene (up to 7.5 mm long) poikilitically encloses small (mostly < 50 microns across), rounded olivine grains and subangular to subrounded chromite grains (~200 microns across). Abundant very small (typically <5 μm across) troilite and metal grains are found within both orthopyroxene and chromite grains. Most of the thin section consists of a fine-grained (ranging from < 10 to 400 μm, typically around 40-50 μm) clastic matrix. Approximately 87% of the matrix grains are orthopyroxene, 10% are olivine, 3% are chromite, and metal and troilite (found as inclusions in orthopyroxene and chromite) make up <1%. Matrix olivine grains form clusters strung out to form bands across the section. Yellow staining and pits are associated with these olivine-rich bands. No plagioclase feldspar, high-Ca pyroxene, silica polymorph, phosphate, or typical weathering products such as carbonate or sulfate was observed in either the clast or matrix.

Geochemistry: Orthopyroxene and olivine compositions are essentially the same for both clast and matrix and lie along the trend described for equilibrium assemblages of olivine and orthopyroxene described by Beck and McSween (2010). Low-Ca pyroxene (clast: Fs_24.1±0.4Wo_1.6±0.0, range Fs_23.5-24.6Wo_1.6-1.6, FeO/MnO=27.8±0.9, N=8; matrix: Fs_23.4±0.7Wo_1.5±0.2, range Fs_22.3-25.7Wo_1.3-2.4, FeO/MnO=28.9±0.6, N=28). Olivine (clast: Fa_28.1±0.8, range Fa_27.1-29.0, FeO/MnO=45.4±2.6, N=9; matrix: Fa_28.9±0.4, range Fa_28.2-29.3, FeO/MnO=47.4±1.8, N=9). Chromite (clast: Cr/(Cr+Al)=0.8±0.0, Mg/(Mg+Fe)=0.2±0.0, N=8; matrix: Cr/(Cr+Al)=0.8±0.0, Mg/(Mg+Fe)=0.2±0.0, N=7). Metal grains are close to Ni-free (Ni~0.3 wt%, N=4).

Classification: HED achondrite (Diogenite-olivine bearing) based on mineralogy, including the presence of about 10% olivine, lack of plagioclase feldspar, and based on phase compositions, including equilibrium between olivine and orthopyroxene in both matrix and clast.

Specimens: Cascadia holds 106.3 g in five pieces, as well as a polished thin section; Mustapha Oulkouch and Ahmed Sbai hold the main mass.