Oxygen isotopic heterogeneities, their petrological correlations, and implications for melt origins of chondrules in unequilibrated ordinary chondrites

Clayton et al. (1976, 1982) established that equilibrated ordinary chondrites (EOC's) can be divided into the H- and L-groups on the basis of their oxygen isotopic composition. The present investigation is concerned with new oxygen isotopic analyses of petrologically well-characterized individual chondrules from the unequilibrated chondrites Dhajala (H3,4), Hallingeberg (L3), and Semarkona (LL3). A study is conducted regarding the implications of isotopic/petrologial correlations for the origin of chondrules in ordinary chondrites. It is found that the oxygen isotopic heterogeneities among chondrules are reminiscent of the bulk elemental and phase compositional heterogeneities among the same and other chondrules as reported by Gooding et al. (1979, 1980). It is concluded that chondrules formed possibly as a result of the melting of preexisting materials which were both chemically and isotopically heterogeneous.