The condensation origin of zoned metal grains in Queen Alexandra Range 94411: Implications for the formation of the Bencubbin-like chondrites

Thermodynamic analysis of the compositional profiles across large chemicall y-zoned Fe,Ni metal grains in the Bencubbin-like chondrite Queen Alexandra Range (QUE) 94411 suggests that these grains formed by non-equilibrium gas- solid condensation under variable oxidizing conditions, isolation degree, a nd Cr depletion factors. The oxidizing conditions must have resulted from t he complete vaporization of nebular regions with enhanced dust/gas ratios ( similar to 10-40 x solar). Because the origin of each of the metal grains s tudied requires different condensation parameters (dust/gas ratio, isolatio n degree, and Cr depletion factor), a high degree of heterogeneity in the f ormation region of the Bencubbin-like chondrite metal is required. To prese rve compositional zoning of the metal grains and prevent their melting and sulfidization, the grains must have been removed from the hot condensation region into cold regions where the accretion of the Bencubbin-like asteroid al body took place.