Iodine-xenon studies of petrographically and chemically characterized Chainpur chondrules

INAA, noble gas, and petrographic studies conducted on samples of 18 chondrules and matric material from the Chainpur (LL3) indicate that the I-129/I-127 ratio, R(0), varies by a factor of more than 10 among the chondrules. This corresponds to a greater-than-50 Ma span in apparent I-Xe ages. Models which invoke either gas-dust mixing or nebular heterogeneity cannot satisfactorily explain these data, any more than can hypotheses which attribute the variations to differences in formation age, metamorphic rate, or time of aqueous alteration. It is alternatively suggested that the variations represent periods of low-grade shock events.