A search for isotopic anomalies in uranium

Abstract

The 238 U/ 235 U ratios for nine bulk chondritic meteorites and a terrestrial basalt were measured. The total range in 238 U/ 235 U determined for both total meteorites and for acid leaches was from 137.2 to 138.3 and to within the error limits indistinguishable from normal terrestrial U. The typical errors in a single determination are ±6‰ (2σ M ) for a 2 ng U sample from a chondrite. Taking the extreme values of δ 235 U for each measurement the maximum amount of excess 235 U that can be allowed to be present ranges from 2 × 10 8 to 2 × 10 9 atoms per gram of bulk meteorite. These results do not support the claims of variations in 238 U/ 235 U at the percentage levels or number of excess 235 U atoms in some of the same meteorites as reported by several other previous workers.