THE ORIGIN OF CHROMITIC CHONDRULES AND THE VOLATILITY OF CR UNDER A RANGE OF NEBULAR CONDITIONS

Abstract

We characterize ten chromitic chondrules, two spinelian chondrules and one spinel-bearing chondrule and summarize data for 120 chromitic inclusions discovered in an extensive survey of ordinary chondrites. Compositional and petrographic evidence suggests that chromitic chondrules and inclusions are closely related. TheCr/(Cr + Al) ratios in the spinel of these objects range from 0.5 to 0.9 and bulk Al2O3 contents are uniformly high ( > 10 wt%, except for one with 8 wt%). No other elements having comparable solar abundances are so strongly enriched, and alkali feldspar and merrillite are more common than in normal chondrules.