Uranium isotope variations in group II refractory inclusions

The ^(235)U/^(238)U ratio shows little variability in most terrestrial and meteoritic bodies (≤1 ‰) [1-3]. In contrast, large excesses of ^(235)U, up to 3.5 ‰, have been found in a few Calcium-Aluminum rich inclusions (CAIs) and have been interpreted as evidence of live ^(247)Cm (t_(1/2) = 15.6 My) in the early solar system (SS) [4]. Though this is a plausible explanation, it relies on four points with high Nd/U ratio that define a “pseudochron”, so more work is needed to determine the cause of U isotope variations in CAIs. Here, we report some preliminary results on the identification, characterization and U isotopic analysis of 12 fine-grained, group II, CAIs from the Allende meteorite.