Abstract:

The mineral-petrological characteristics and shocked effects of the monomict and polymict ureilites are studied in this paper.On the basis of Δ17O,δ13C,MgO/(MgO+FeO)mol%,noble gases,abundances and types of pyroxenes in ureilites,we discussed the classification and origin model.Ureilites are ultramafic magmatic rooks and they exhibit some characteristics of both primitive and differentiated achondrites.Ureilites generally originate from a once partially molten,originally chondritic parent body.Most typical ureilites have monomict textures.The Polymict ureilites are a few,their fragmental breccias contain lithic clasts of monomict ureilite material and other materials.The origin model is mainly ultramafic igneous cumulates or partially melted residues.