Abstract: The scale and nature of the exsolution textures developed in some titanomagnetites have been used to calculate the rate at which the oxides were cooling at the time of exsolution. The cooling rates were calculated by evaluating a kinetic model, which describes the growth of an ulvöspinel-rich lamella in titanomagnetite during exsolution. The model was evaluated both by numerical techniques and by an approximate analytical method.

The cooling rates during titanomagnetite exsolution of the Taberg, Skaergaard and part of the Mt. Yamaska intrusions were calculated to be approximately 130, 12 and 6000°C per 1000 years respectively. These values are in good agreement with cooling rates calculated from heat flow models of the intrusions.