URANIUM-SERIES DATING OF CARNOTITES - CONCORDANCE BETWEEN TH-230 AND PA-231 AGES

Pa-231/U-235 and Th-230/U-234 ages were determined for 17 carnotites f rom two areas in Israel. For this purpose, a simplified one-step metho d was used to purify the protactinium, the extraction into TTA (thenoy l-trifluoro-acetone) at high acidity. Using the test of concordance be tween the two dating methods, 12 of the 17 carnotites were found to ha ve acted as closed chemical systems whereas 4 seem to have gained uran ium. The details of the relationships between the (231)pa/U-235 and th e Th-230/U-234 ages suggest that the uranium gain which took place in the latter 4 cases, occurred in a manner which was approximately conti nuous and linear.