Jiddat al Harasis 203                       19°58.980'N, 56°24.821'E

Oman

Find: 25 December 2002

Mesosiderite (2C)

History: Thirty-one specimens (total mass >46.2 kg) belonging to the same fall event were recovered in 2003-2005 in adjacent areas of JaH and RaS.

Physical characteristics: We describe the best-characterized specimen of this group, 1231.2 g, found by A. Al-Kathiri, M. Eggimann, and S. Lorenzetti. Strongly weathered surface; partial disintegration. Large pyroxene clasts are visible on surface.

Petrography: (E. Gnos, MHNGE; B. Hofmann, NMBE; A. Al-Kathiri, UBE/MCI) The stone has a brecciated texture with a recrystallized matrix. Poikilitic minerals are absent. Point counting in reflected light (n = 500) yielded in vol%, orthopyroxene (some large clasts exceed 5 cm in size) = 68.8, plagioclase (+ silica + phosphate) = 7.8, metal/oxide = 17.2, troilite = 4.6, and isolated, up to 6.5 mm-sized olivine clasts = 1.6. Many orthopyroxene crystals contain abundant sulfide and metallic inclusions along healed cracks. Metal is heavily weathered (80-100%), troilite shows partial oxidation.

Mineral composition and Geochemistry: Microprobe analyses of pyroxene yielded a compositional range of Fs_31.0-33.3Wo_1.8-40 (average Fs_28.4Wo_2.5). Bulk composition: After subtraction of metal-derived Fe from bulk analyses and assuming a Fe/Mn ratio of the non-metal fraction of 30, a diogenitic composition with SiO₂ = 51.0, Al₂O₃ = 3.9, MgO = 21.5, CaO = 3.6, and Na₂O = 0.23 (all wt%; (REE ~ 2 × CI). Normative plagioclase in silicate fraction is <12 wt%. Estimated primary metal content is 23.5 wt%. Oxygen isotopes: (I. A. Franchi and R. C. Greenwood, OU) δ¹⁷O = 1.403, δ¹⁸O = 3.143, and Δ¹⁷O = -0.232 (mean of 2 analyses).

Classification: Mesosiderite (2C); minimal shock, extensive weathering. Classification as 2C mesosiderite is based on low plagioclase content and recrystallized matrix without poikilitic minerals.

Specimens: Type specimen and main mass at NMBE.

Submitted by: Beda Hofmann, NMBE.