DHO 500 Ungrouped achondrite


A stone weighing 116 g was found in the Dhofar region of Oman. Mineralogy and classification (C. Lorenz and M. Ivanova, Vernad.): the rock is a metabreccia and consists of at least three different lithologies: pyroxene-feldspar, pyroxene-olivine and pyroxene-olivine-feldspar. In texture the lithologies vary from medium to coarse-grained, poikiloblastic to equigranular. Mineral chemistry: olivine Fa4.8; CaO - 0.13 wt.%, Cr2O3 - 0.42 wt.%; orthopyroxene is En95Wo2, Fe/Mn ratio is 6 (at); feldspar is An13-34. Olivine and pyroxene are of the same compositions in the lithologies. The minor phases are Ca-rich augite En52Wo44; Cr-rich troilite (up to 3.11 wt% Cr), chromite and essentially rare minute grains of Fe-Ni metal. Weathering grade is W3. Oxygen isotopic composition (R. N. Clayton, UChi): d 18O = +9.21; d 17O = +4.29; D 17O = -0.49, is not in the range of known meteorite groups but close to the winonaite-IAB-IIICD trend, and ureilites. Mineralogically the meteorite may have some links to primitive achondrites but compositions of olivine and troilite are close to those in polymict ureilites. However, this meteorite lacks a carbon-rich matrix. Specimens: a type specimen of 23.5 g and a thin section Vernad; main mass with anonymous finder.