Anomalous Source Research Articles

Anomalous leads from Broken Hill, Australia

Results are presented from isotopic analyses of seven Thackaringa-type leads from Broken Hill, Australia, occurring in vein-type deposits. The points representing these leads lie, within very narrow limits, along a straight proves, beyond serious doubt, the contention made in a prene on a Pb/sup 207//Pb/sup 204/ versus Pb/sup 206//Pb/sup 204/ plot. This graph proves, beyond serious doubt, the contention made in a previous paper in 1957, that the Thackaringa-type leads at Broken Hill are a series of anomalous leads. The isotopic analyses are interpreted to indicate that the Thackaringatype leads were deposited at a time not earlier than 1190 plus or minus 35 million years ago and that the source material for the anomalous radiogenic lead component came into existence not before 1970 plus or minus 50 million years ago but not later than 1190 plus or minus 50 million years ago. Approximate values for the thorium-uranium ratios of the anomalous lead sources are included. (auth)