ABSTRACT

The difference in the isotopic compositions of barium from some meteorites and from the terrestrial barium is explained as due to the alteration of the isotopic ratios by a combined effect of mass-dependent fractionation, neutron-capture and cosmic-ray irradiation processes, which took place prior to and during the period of formation of the solar system. The abundances of ¹³⁴Ba and ¹³⁵Ba in the meteorite Bruderheim seem to be slightly enhanced due to the decays of 2.06-year ¹³⁴Cs and 2.3 × 10⁶-year ¹³⁵Ba. A small difference in the isotopic compositions of cerium in the Bruderheim meteorite and the terrestiral sample can also be attributed to neutron-capture processes, which occurred during an early irradiation period. It is shown that the barium and xenon isotopic anomalies observed in meteorites are closely related to each other.