On the Zr-in-rutile and Ti-in-zircon geothermometers

The advents of Zr-in-rutile thermometer and Ti-in-zircon thermometer have prompted wide applications to petrological problems as well as ongoing tests of its validity.The thermometers have gained much attention and wide application to different types of high-grade metamorphic rocks due to their simplicity and validity.There are several different calibrations for each thermometer.However,the applicability of those calibrations is still ambiguous with hot debates on interpretation of thermometric data.So far,the studies of all thermometers are only limited to single component thermometer.Some studies have demonstrated that the metamorphic temperatures measured by the Zr-in-rutile thermometer are in good agreement with the results obtained by cation partition thermometers,suggesting that the Zr-in-rutile thermometers is capable of providing the peak metamorphic temperatures.On the other hand,Zr-in-rutile temperatures for Dabie-Sulu UHP metamorphic rocks were remarkably lower than those obtained by the other thermometers.By comparison of the different studies,it is realized that the lower temperatures from the Zr-in-rutile thermometry is possibly caused not only by the variations of TiO2 or SiO2 activity,pressure correction,element diffusivity and retrograde reaction in the presence of fluid,but also by different stages of mineral growth.Therefore,the petrographic paragenesis,mineral inclusions and trace elements,and U-Pb ages should be taken into account when applying the all thermometers to continental subduction-zone UHP metamorphic rocks.On this basis we are in a position to estimate the generations of minerals and conditions of their growth and thus to place reasonable constraints on the interpretation of thermometric data.