Argon Thermochronometers and the Effects of Recrystallization

Rocks exhumed from high temperatures in continental settings contain a record of cooling in potassium-bearing minerals, known as thermochronometers, due to the quantitative retention of radiogenic argon below some characteristic closure temperature. However, thermochronometers may be affected by recrystallization processes occurring below such temperatures, and in some cases argon data record the timing of crystallization rather than cooling. Field, microstructural and isotopic analysis will be used to evaluate the effects of recrystallization on the muscovite and potassium-feldspar thermochronometers, particularly in fault zones. Understanding the effects of recrystallization on thermochronometers is critical for studies of the assembly of the continental crust.