However, there is a limited range in Sm-Nd isotopes in many igneous rocks, although metamorphic rocks that contain the mineral garnet are useful as this mineral has a large range in Sm-Nd isotopes.
This technique also helps in determining the composition and evolution of the Earth's mantle and bodies in the universe.
The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.
The relationship between the two is: T = 0.693 / λ Many different radioactive isotopes and techniques are used for dating.
All rely on the fact that certain elements (particularly uranium and potassium) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age.
This technique is good for iron meteorites and the mineral molybdenite.
This system is highly favoured for accurate dating of igneous and metamorphic rocks, through many different techniques.