Dhofar 535

Oman

Found 2000 January 16

Chondrite (ungrouped)

Many stones weighing a total of 204 g were found in the Dhofar region of Oman. Mineralogy and classification (M. Ivanova, Vernad; L. Taylor, UTenn): the meteorite consists of chondrules, 0.08–3.2 mm in diameter, (0.86 mm in average) of different types, PO, POP, BO, RP, CC, and their fragments embedded in a fine-grained matrix. Chondrule/matrix ratio is 1.1. Olivine and low-Ca pyroxene have large compositional ranges: olivine has Fa1–50, CaO 0.2 wt%; Al2O3 0.06 wt%, Cr2O3 0.09 wt%, PMD of Fa 42%; low-Ca pyroxene is Wo2– 3.5En53–95; chondrules contain glassy mesostasis. Accessory minerals include: pigeonite, chromite, troilite, rare hydroxides, and rare FeNi metal (Ni 5 wt%; Co 0.4 wt%). Thermoluminescence studies (A. I. Ivliev, Vernad) indicate petrologic type 3.2/3.3. The meteorite is heavily weathered, and some silicates are altered. Weathering grade is W5; shock stage is S1. Based on the very low abundance of FeNi metal and hydroxides, Dho 535 could belong to either the LL or R chondrite groups but with very abundant matrix. The average size of chondrules is consistent with LL chondrites. A histogram showing the distribution of olivine is similar to unequilibrated ordinary chondrites. FeNi metal is mostly kamacite, typical for H chondrites and unusual for R chondrites. Sulfide assemblages and chromite chemistry are also unusual for R chondrites. The absence of refractory objects and olivine chemistry distinguish Dho 535 from C3 chondrites. Oxygen isotope composition (R. N. Clayton, UChi): δ¹⁸O = +8.56‰; δ¹⁷O = +4.96‰, Δ¹⁷Ο = 4.51‰ [sic; note from Database Editor: this should probably be Δ¹⁷Ο = 0.51‰] is unusual for any chondrite type. Specimens: type specimen of 46.8 g and thin section, Vernad; main mass with anonymous finder.