High-temperature behavior of quartz-in-garnet system revealed by in situ Raman spectroscopy

Quartz is one of the most abundant minerals in the Earth crust and therefore quartz inclusions in garnet are of great interest for elastic geobarometry, an approach that exploits the elastic properties of the mineral pair to back-calculate the conditions of inclusion entrapment. However, the high-temperature behavior of quartz inclusions close to the a-I3 transition bound-ary has not been studied experimentally. We have therefore performed in situ high-temperature Raman spectroscopy on a quartz-in-garnet system up to 1000 K, and have also collected an improved reference data set for the temperature dependence of the Raman scattering of free quartz. Our results show that the a-to-fi phase transition is hindered by the stress imposed by the host on the quartz inclusion, resulting in a thermosalient effect of the whole host-inclusion system or a mechanical cracking of the host mineral.