All of these systems are based upon the radioactive decay of a parent nuclide to a stable daughter nuclide.Obtaining accurate information from these decay systems for the purposes of determining the age of a mineral or rock requires: (1) the decay constant of the parent nuclide is accurately and precisely determined; (2) closed system behavior, which can be simply stated to mean that the Parent/daughter ratio has only changed by radioactive decay; and (3) the initial daughter nuclide, if present, can be precisely and accurately accounted for.The refractory and durable nature of zircon over a wide range of geological conditions means that it is likely to retain its primary crystallization age even through subsequent metamorphic events.
A year is defined as 86,400 SI seconds and is expressed using annum (latin for years).
When accounting for large amounts of time, annum can be prefaced using the abbreviations k, M, or G representing thousand, million, and billion, respectively (ka, Ma, and Ga).
Radioisotope geochronology in its present form is made possible by radioactive decay.
Radioactive decay, also known as nuclear decay or radioactivity, is the process through which the radioactive (unstable) nucleus of an atom emits particles which lowers it to a lower energy state.
Titanite is most commonly used to date the cooling of metamorphic events using U-Pb isotopes.
Although it can accommodate several 100’s of ppm U in the crystal lattice, it also incorporates variable amounts of Pb.See this GSA Today Letter to Editors for further information.In order to calculate a date using the age equation it is required to determine the ratio of the parent isotope (P) to it's respective daughter isotope (D).In this section we outline the basic principles of the various radio-isotopic geochronometers, differentiating the U-Pb system applied to U-bearing accessory minerals from the isochron geochronometers (Re-Os, Lu-Hf, Pb-Pb etc.) applied to chemical precipitates and organic residues.In order to be able to quantitatively determine the ratio of the parent nuclide (P) to a stable daughter nuclide (D) we need to analyses materials that have high proportions of P relative to D at their formation such that the ingrowth of D overwhelms that any amount of initial D isotope.A good geochronometer must either have little to no initial incorporation of the daughter isotope or must have a fixed ratio from which the radiogenic and nonradiogenic proportions can be determined.