Thermochronometers

Thermochronometers are a class of geological techniques used to determine the thermal history of rocks and the surrounding Earth materials. This is achieved by measuring the accumulation of radiation damage in minerals, which occurs at high temperatures. By dating the time of formation of these defects, scientists can infer the temperature at which rocks were exposed throughout their history.

The most commonly used thermochronometer is the apatite fission-track (AFT) technique, which measures the accumulation of damage in the apatite mineral due to the interaction of uranium and lead isotopes. Other methods include the Rb-Sr and K-Ar methods, which measure the release of argon and the accumulation of argon defects in the muscovite and biotite minerals, respectively. The K-feldspar (KIRD) and zircon (ZHe) methods are also used, which measure the thermal exposure of these minerals using the accumulation of anomalous helium isotopes.

Thermochronometric data can provide valuable information on the thermal evolution of the Earth's crust and the surface processes that shape it. This can include the timing of tectonic events, the extent of weathering and erosion, and the duration of mountain building and volcanism. Thermochronometers are also used to analyze the thermal evolution of sedimentary and metamorphic rocks, as well as igneous and fault rocks.

Thermochronometric data has been used extensively to study the evolution of various geological provinces, including mountain ranges and exhumed metamorphic complexes. The technique has also been applied to problems in hydrology, geohazard assessment, and energy resource assessment. By providing a quantitative measure of the thermal history of rocks, thermochronometry has become an essential tool in the field of geology.