Jiddat al Harasis 422             19°50.357′N, 56°28.762′E

Oman

Find: 3 March 2007

Achondrite (ureilite impact melt breccia with dunite clasts)

History: A single stone was found during a search for meteorites by M. Eggimann, E. Gnos, E. Janots, B. Hofmann, L. Huber and F. Zurfluh.

Physical characteristics: Rounded reddish-brown single stone with a mass of 61.48 g, no fusion crust preserved, wind polished surface. Heterogeneous surface with protruding clasts.

Petrography (E. Janots, IMM E. Gnos, MHNGE; B. Hofmann, NMBE): The rock is a dimict breccia and shows a thorough fine-grained, equigranular recrystallization/reequilibration texture of clasts and matrix. Dunite clasts (~50%) are up to 14 mm long, nearly free of carbon platelets, secondary iron hydroxides and large pores. The dunite clasts consist of nearly pure, homogeneous olivine (Fa_19–21) with triple joints. The groundmass, ~50% of the stone, consists of olivine (Fa_10–17), orthopyroxene (Fs_9–12Wo_0.5–5,0) and augite (Fs_9–12Wo_20–35), abundant carbon platelets (up to 1 mm) consisting of graphite and diamond and Fe-oxyhydroxides. At the contact with pores and carbon/Fe-hydroxides, olivine and pyroxene show a narrow reduction rim depleted in Fe. The groundmass contains numerous pores up to 1 mm in size, partially filled with secondary bassanite (based on Raman spectroscopy). The groundmass is interpreted as ureilite impact melt with residual carbon phases.

Geochemistry: Oxygen isotopes (I. A. Franchi and R. C. Greenwood, OU) of dunite clast δ¹⁷O = 2.87, δ¹⁸O = 7.57, and Δ¹⁷O = −1.07 (mean of two replicates). Oxygen isotopes of matrix: δ¹⁷O = 3.31, δ¹⁸O = 8.31, and Δ¹⁷O = −1.00 (mean of two replicates) (Δ¹⁷O= δ¹⁷O-0.52 δ¹⁸O). Both, clast and matrix analyses plot within the ureilite field.

Classification: Ureilite (impact melt breccia with dunite clasts)
Type specimens: All at NMBE.