Dating metamorphic rocks
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.
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.
This decay process leads to a more balanced nucleus and when the number of protons and neutrons balance, the atom becomes stable.
This radioactivity can be used for dating, since a radioactive 'parent' element decays into a stable 'daughter' element at a constant rate.
This technique has become more widely used since the late 1950s.
For geological purposes, this is taken as one year.
The amount of 14C present and the known rate of decay of 14C and the equilibrium value gives the length of time elapsed since the death of the organism.
This method faces problems because the cosmic ray flux has changed over time, but a calibration factor is applied to take this into account.
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.