Uses of radioactive carbon dating
This technique has become more widely used since the late 1950s.
Its great advantage is that most rocks contain potassium, usually locked up in feldspars, clays and amphiboles.
However, potassium is very mobile during metamorphism and alteration, and so this technique is not used much for old rocks, but is useful for rocks of the Mesozoic and Cenozoic Eras, particularly unaltered igneous rocks.
Argon-Argon dating (39Ar-40Ar) This technique developed in the late 1960s but came into vogue in the early 1980s, through step-wise release of the isotopes.
The Re-Os isotopic system was first developed in the early 1960s, but recently has been improved for accurate age determinations.
The main limitation is that it only works on certain igneous rocks as most rocks have insufficient Re and Os or lack evolution of the isotopes.
Others place mineral grains under a special microscope, firing a laser beam at the grains which ionises the mineral and releases the isotopes.Radioactive dating is a method of dating rocks and minerals using radioactive isotopes.This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.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.
Another way of expressing this is the half-life period (given the symbol T).