U th dating wiki


22-Oct-2020 08:52

The existence of two 'parallel' uranium-lead decay routes allows several dating techniques within the overall U-Pb system.

The term 'U-Pb dating' normally implies the coupled use of both decay schemes.

These types of minerals often produce lower precision ages than igneous and metamorphic minerals traditionally used for age dating, but are more common in the geologic record.

During the alpha decay steps, the zircon crystal experiences radiation damage, associated with each alpha decay.

and most refined of the radiometric dating schemes.

It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range. This mineral incorporates uranium and thorium atoms into its crystal structure, but strongly rejects lead when forming.

The methods discussed in this article each require two isotopes: a parent isotope which is soluble (or the commonly occurring compounds of which are soluble) and a radioactive daughter isotope which is not soluble.

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Where crystals such as zircon with uranium and thorium inclusions do not occur, uranium-lead dating techniques have also been applied to other minerals such as calcite/aragonite and other carbonate minerals.

This method has a couple of advantages over sediment traps.

First, it is quicker: it doesn't take long to obtain a sediment core sample, whereas a sediment trap has to be left in place for at least a year to produce useful results.

This is particularly true of Pb; since it has a half-life of only 22 years, this makes it useless for most geological purposes.

However, it can be used to gauge the rates of deposition of marine sediment as an alternative to the use of sediment traps.

However, use of a single decay scheme (usually Pb) leads to the U–Pb isochron dating method, analogous to the rubidium–strontium dating method.