Shişr 043 (IIIAB medium octahedrite): The first iron meteorite from the Oman desert

Abstract

The iron meteorite Shişr 043 is a single mass of 8267 g found in the south Oman desert 42 km NE of the Shişr village. It is the first iron identified among the >1400 individual meteorites reported from Oman. The meteorite is a slightly elongated mass showing only minor rusting, a partially smooth and partially rough surface with octahedral cleavage, and a partially preserved metallic fusion crust typically 0.75 mm thick. The undeformed Widmanstätten pattern with a mean kamacite bandwidth of 1.0 +/- 0.1 mm (n = 97) indicates structural classification as a medium octahedrite. From the bulk composition, Ni = 8.06 wt%, Ga = 18.8 ppm, Ge = 37.25 ppm, and Ir = 3.92 ppm, the meteorite is classified as IIIAB, the most common group of iron meteorites. The cosmic-ray exposure (CRE) age based on 3He, 21Ne, 38Ar concentrations and 10Be-21Ne, 26Al-21Ne, and 36Cl-36Ar ratios is 290 +/- 20 Ma. This age falls within the range observed for type IIIAB iron meteorites, but does not coincide with the main cluster. The cosmogenic noble gas and radionuclide data indicate that Shişr 043 had a relatively small preatmospheric mass. The low degree of weathering is consistent with a young terrestrial age of <10,000 years based on the saturated 41Ca concentration. Shişr 043 is not paired with any of the other eight known iron meteorites from the Arabian Peninsula.