We now have a new geological clock and it is possible to date garnet, one of the most common minerals used by geologists, using the U-Pb method. This method is commonly used in geochronology, but it requires significant amounts of uranium, and for this reason it has always been applied to specific minerals (for example zircon), which however may have important limitations for reconstructing geological processes.

This is what emerges from the study "The age of granulite-facies metamorphism in the Ivrea-Verbano Zone (NW Italy) determined through in-situ U-Pb dating of garnet"; published in the scientific journal of Petrology; led by Omar Bartoli professor of the Department of Geosciences at the University of Padua, together with his colleague Bruna Borges Carvalho and conducted in collaboration with the University of Frankfurt.

"The main challenge has been to use the few billionths of a gram of uranium present in garnet. This approach would not have been possible until a few years ago, but the rapid development of new technologies now allows us to push the analytical limits to very low concentrations"; says Omar Bartoli, the first author of the paper. "Garnet is a unique mineral because it records the pressure and temperature conditions of formation of the rocks, but it was difficult to use it as a geological clock. Instead, our study has shown that garnet has the potential to be a robust geological clock, taking advantage of the few nanograms of uranium collected in a single working day, simply by analysing garnet grains in rocks."

For the University of Padua, the researcher Bruna Borges Carvalho also took part in this study. "We applied this innovative technique to rock samples from one of the world's most famous sections of deep continental crust, which outcrops in the Western Alps and where we have been working on for some years".
Measurements made by the team of researchers have shown that this new geological clock is resistant even to very high temperatures of 1,000°C, and therefore, it can be used in the future in various geological contexts.