Teghaza 001        23.031765, -4.646299

Gao, Mali

Find: 2022

Classification: Martian meteorite (Shergottite)

History: This meteorite was found at the beginning of September 2022 during a meteorite search expedition north of the archaeological area of Taghaza in Mali, by Sahrawi meteorite hunters. The find locality is approximately 73 km SSE of Teghaza, and 34 km ENE of Bir Chali. Eight identically appearing stones were found at this locality. The largest stone is 442 g.

Physical characteristics: The eight recovered stones lack fusion crust and their sandblasted surfaces show a mix of fine dark grains. The largest pieces have caliche coatings where they were buried in the desert pavement. Freshly broken surfaces reveal light-colored and brown-orange grains and shiny clear maskelynite.

Petrography: (A. Ross and C. Agee, UNM) Backscatter electron images, SEM images, and reflected light microscopy show that this meteorite is made up of approximately 50% pyroxene and 40% maskelynite. Some of the pigeonitic pyroxenes have exsolution lamellae and the sub-calcic augites occur as separate phases, both are unzoned and compositionally equilibrated. A significant proportion of the pyroxene grains show layered alteration phases in their cores. The alteration is made up of thin layers of Fe-oxide and Mn-oxide with low microprobe totals consistent with ferrihydrite and manganese hydroxide. Most plagioclase has been transformed to maskelynite, however some fine-grained perthitic patches with higher orthoclase contents up to Or₁₁ are present. Other minor ubiquitous phases include ilmenite, Ti-Cr spinel, Fe-sulfide, silica, and Cl-rich apatite.

Geochemistry: (A. Ross and C. Agee, UNM) Pigeonite Fs_41.0±4.1Wo_9.7±3.0, Fe/Mn=33±1, n=7; sub-calcic augite Fs_25.1±1.5Wo_36.0±0.2, Fe/Mn=31±1, n=4; maskelynite An_48.5±4.3Ab_49.0±3.6, n=6. Oxygen isotopes (K. Ziegler, UNM): 5 acid-washed bulk meteorite fragments analyzed by laser fluorination gave δ¹⁸O= 6.231, 6.359, 6.872, 6.378, 5.897; δ¹⁷O= 3.516, 3.580, 3.871, 3.604, 3.323; Δ¹⁷O= 0.276, 0.273, 0.298, 0.288, 0.257; (linearized, all per mil, TFL slope=0.52).

Classification: Pyroxene-phyric shergottite. Martian meteorite based on Fe/Mn of pyroxenes and An-content of maskelynite. Δ¹⁷O is also consistent with SNC meteorites, however δ¹⁸O values are higher than the normal SNC range, likely due to the mixing of a primary SNC δ¹⁸O component with a higher δ¹⁸O alteration phase or phases such as observed in many pyroxene cores.

Specimens: 22 g including a probe mount on deposit at UNM, Bachir Salek holds the main mass.