Thorium uranium dating
The sample age is based on the difference between the initial ratio of U with the environment (i.e., that it is a closed system.) The method is used for samples that can retain Uranium and Thorium, such as carbonate sediments, bones and teeth. Ages between 1000 and 300,000 years have been reported.
With time, Thorium 230 accumulates in the sample through radiometric decay. The method relies on two separate decay chains, the uranium series from Pb) leads to multiple dating techniques within the overall U–Pb system.The term U–Pb dating normally implies the coupled use of both decay schemes in the 'concordia diagram' (see below).As a result, newly-formed zircon deposits will contain no lead, meaning that any lead found in the mineral is radiogenic.Since the exact rate at which uranium decays into lead is known, the current ratio of lead to uranium in a sample of the mineral can be used to reliably determine its age.
This damage is most concentrated around the parent isotope (U and Th), expelling the daughter isotope (Pb) from its original position in the zircon lattice.