Closure temperature

Closure temperature is the approximate temperature below which a mineral effectively retains a particular isotopic system during cooling. It depends on diffusion, grain size, cooling rate, and mineral properties.

Diffusion: The net movement of particles from regions of higher concentration to regions of lower concentration. Isotopes diffuse through minerals above closure, allowing the isotopic system to re-equilibrate.
Geochronology: The science of determining the ages of rocks, minerals, and geological events. Closure temperature explains why a mineral age can date cooling rather than crystallization.
Blocking temperature: A temperature scale describing when magnetic moments in a material become stable against thermal agitation. It is the magnetic analogue of thermal retention, but arises from magnetic relaxation rather than isotope diffusion.
Radiometric dating: A method of estimating age from predictable changes in radioactive parent and daughter isotopes. Closure temperature governs when a mineral begins preserving the isotope ratio used to calculate an age.
Diffusion coefficient: A parameter describing how rapidly a substance diffuses through a material under specified conditions. Its temperature dependence controls how quickly an isotopic system can lose daughter products.
Uranium–lead dating: A radiometric dating method that uses radioactive decay of uranium isotopes to lead isotopes. Different minerals and domains retain uranium and lead at different temperatures, shaping their age records.
Isotopic equilibrium: A state in which isotope exchange has balanced isotope distributions among connected reservoirs. Closure marks the loss of effective isotopic re-equilibration, rather than the attainment of equilibrium.
Isotope geochemistry: The study of isotope abundances and variations in geological materials and processes. Closure is one way isotope geochemistry connects mineral-scale transport to geological history.
Dodson equation: An equation estimating a mineral's closure temperature from diffusion kinetics, grain geometry, and cooling rate. It formalizes how cooling rate and mineral dimensions shift the effective retention temperature.
Argon–argon dating: A radiometric dating method that derives ages from argon isotope ratios after neutron irradiation. Argon retention during cooling gives this method sensitivity to mineral thermal histories.

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