Tindouf 005        27º21’37.2’’N, 7º45’11.0’’W

Tindouf, Algeria

Find: 17 Apr 2013

Classification: HED achondrite (Eucrite, polymict)

History: On April 17, 2013, Mulay Ahmed found three stones near to the secondary school "12 de Octubre" in the Saharawi refugee camps in Tindouf, Algeria. The main stone was recognized as a possible achondrite specimen by meteorite collector José Antonio Sanchez Santana.

Physical characteristics: Three pieces of 126, 8 and 2 g. Irregular exterior, no fusion crust. A saw cut reveals a polymict breccia with numerous fragmental light and dark clasts.

Petrography: (J. Llorca, UPC). The meteorite is a microbreccia of clasts in a semi-opaque, dark-brown, microcrystalline, impact-melt matrix. The matrix is heterogeneous and is composed of mono and polymineralic fragments. Clast/matrix ratio is approximately 70/30. The larger clasts (maximum dimension 4 mm) are mainly of anorthositic and ophitic basalt lithologies; many have been shocked and partly granulated. The smaller clasts (minimum dimension less than 0.1 mm) are individual mineral grains (mainly pyroxene and plagioclase). Minerals are anorthite, pigeonite and augite (some with fine exsolution lamellae). Accessory minerals are ilmenite, silica polymorph and Al-Ti-bearing chromite. The section is notable for the absence of olivine.

Geochemistry: (R. Pablo Lozano, IGME). Microprobe analyses show plagioclase ranges from An_94-96 with a mean of An_95.4±0.5 (n=23). Pyroxene is variable in composition: pigeonite (Fs_53-59Wo_2-11; Fe/Mn=28-42) with a mean of Fs_57.1±0.3 (n=15) and augite (Fs_24-28Wo_41-45; Fe/Mn=28-39) with a mean of Fs_25.8±0.9 (n=12). Pigeonite and augite grains have Fe/(Fe+Mg)=0.647–0.780 with Ti/(Ti+Cr)=0.35–0.98. Chromite has Cr/(Cr+Al)=0.90. Impact melt glassy matrix composition is SiO₂=49.49, Al₂O₃=17.05, FeO=13.33, MnO=0.18, MgO=5.09, CaO=12.56, Na₂O=0.82, K₂O=0.07, TiO₂=0.49, Cr₂O₃=0.27 and P₂O₅= 0.04 (all in wt.%). Bulk chemistry (J. Reyes, IGME). We used 0.5 grams of sample for analysis. XRF of subsample gave abundances of (in wt.%): SiO₂=46.17, TiO₂=0.55, Al₂O₃=12.47, Fe₂O₃=20.51, MgO=6,38, CaO=10.72 and K₂O<0.10. Na₂O= 0.43 wt.% by AAS. Trace elements were measured with ICP-MS (all in ppm): Be=0.25, V=49.1, Cr=1001, Co=8.65, Ni=26.4, Cu=13, Zn=21.3, As=0.72, Se=2.77, Mo<0.5, Ag<0.1, Cd=2.61, Sb=0.38, Ba=1090, Tl<0.1, Pb<2, Th=0.33 and U=0.22. Oxygen isotopes (R. Greenwood, OU). δ¹⁷O=1.89; δ¹⁸O=4.05; Δ¹⁷O=-0.21 (all values in ‰).

Classification (R. Pablo Lozano, IGME). Achondrite, polymict eucrite. Terrestrial weathering is moderate. Tindouf 005 is similar to Dhofar 1626 but the first one has fewer anorthosites than the second one and the exolution lamellaes are quite frequent in Tindouf 005.

Specimens. Type specimen (16.9 g), two co-type specimens (1.8 + 1.3 g) and a probe mount are on deposit at Museo Geominero (IGME). A thin section is on deposit at UPC. José Antonio Sánchez Santana holds the main mass.