Uranium series dating
With 238U the Pb/U ratio grows much more slowly with age, but the idea is the same.If you took rocks of all ages and plotted their two Pb/U ratios from their two isotope pairs against each other on a graph, the points would form a beautiful line called a concordia (see the example in the right column).The two cascades are different—235U becomes 207Pb and 238U becomes 206Pb.What makes this fact useful is that they occur at different rates, as expressed in their half-lives (the time it takes for half the atoms to decay).
If nothing disturbs the grain to release any of this radiogenic lead, dating it is straightforward in concept.
Once disequilibrium occurs, secular equilibrium status will be restored, or in...
Our editors will review what you’ve submitted and determine whether to revise the article.
In these cases, the concordia diagram is a valuable tool.
Consider the concordia: as zircons age, they move outward along the curve.