The radiometric dating of an igneous rock provides
For most radioactive nuclides, the half-life depends solely on nuclear properties and is essentially a constant.
For all other nuclides, the proportion of the original nuclide to its decay products changes in a predictable way as the original nuclide decays over time.All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus.The temperature at which this happens is known as the closure temperature or blocking temperature and is specific to a particular material and isotopic system.These temperatures are experimentally determined in the lab by artificially resetting sample minerals using a high-temperature furnace.Another possibility is spontaneous fission into two or more nuclides.
While the moment in time at which a particular nucleus decays is unpredictable, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life, usually given in units of years when discussing dating techniques.
Precision is enhanced if measurements are taken on multiple samples from different locations of the rock body.
Alternatively, if several different minerals can be dated from the same sample and are assumed to be formed by the same event and were in equilibrium with the reservoir when they formed, they should form an isochron. In uranium–lead dating, the concordia diagram is used which also decreases the problem of nuclide loss.
Finally, correlation between different isotopic dating methods may be required to confirm the age of a sample.
For example, the age of the Amitsoq gneisses from western Greenland was determined to be Accurate radiometric dating generally requires that the parent has a long enough half-life that it will be present in significant amounts at the time of measurement (except as described below under "Dating with short-lived extinct radionuclides"), the half-life of the parent is accurately known, and enough of the daughter product is produced to be accurately measured and distinguished from the initial amount of the daughter present in the material.
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.