| Abstract: | A mathematical model is set up to describe the evolution in time of the activity ratios of the long lived members of the 238U decay series following alteration of the initial state of secular equilibrium in the rock by a rock-water interaction. Both sudden (that is to say, of duration very much shorter than any of the half-lives involved) and continuously acting disturbances are considered. Continuous processes may involve either the removal or the deposition of uranium and these are represented in the formalism as first and zero order effects respectively. Difficulties of principle are identified, but in spite of these an attempt is made to show that the predictions of the model are useful in the interpretation of activity ratios obtained for suites of samples under circumstances in which complementary geochemical information is available. |
