IODINE-XENON STUDIES OF BJURBOLE AND PARNALLEE USING RELAX

Iodine-xenon analyses of chondrules from the Bjurbole L4 and Parnallee LL3.5 meteorites have been made using a continuous wave laser micropr obe and the resonance ionisation mass spectrometer RELAX. The excess X e-129 content released from the Bjurbole chondrule is lower than previ ous stepped-heating studies have found, suggesting that the technique does not completely degas the samples. Nonetheless, clear isochrons we re produced, and data for initial Xe-129/Xe-130 are consistent with ea rlier work. A correlation is evident in each chondrule between Xe-131 and Xe-128, perhaps indicating a common host-phase for their parent nuclides, a condition possibly fulfilled by a Te- and I-bearing sulfid e. The I-Xe system of a Parnallee macrochondrule exhibits no excess Xe -129, possibly as a result of thermal alteration or deformation before accumulation of the meteorite. A cristobalite-bearing chondrule deple ted in O-16 yields an I-Xe age of 4.5 +/- 0.5 Ma after the mean Bjurbo le age.