This study proposes a new way to highlight hydrothermal fluid circulations and thermal anomalies in the Earth's crust with a combined evaluation of the age of granite and gneiss apatites (< 200 µm) as well as the behaviour of their chemical elements. As an exploration tool, this approach is very promising and complementary to other geothermal exploration techniques based on numerical modelling. Moreover, it is a cost-effective tool as it allows for constraining geothermal models.