Thermochronology is the study of the thermal history of rocks. We date minerals such as e.g. apatite and zircon using (U-Th)/Helium dating to investigate when a rock sample has last experienced temperatures between ~40-70°C and 120-180°C respectively. For a standard geothermal gradient of ~25°C/km for the upper crust these temperatures correspond to depths of ~1.5 - 3 and 5 - 7 km.
The method utilizes α-decay of 238U and 232Th (parent isotopes), a process producing 4He atoms (daughter isotopes) which are only preserved below specific temperatures in the targeted minerals. This allows us to pinpoint the time when these temperature thresholds were crossed, by measuring all three isotopes and solving the decay equation.
This method requires careful selection of ideal target mineral crystals under microscope conditions as well as high sensitivity analysis of the parent (U/Th) and daughter (He) isotope ratio to obtain precise, accurate and reproducible data. Our new laboratory enables us to do that.