Abstract
Using an iterative numerical approach, we have obtained the self-consistent thermal expansion, heat capacity, and Grüneisen parameters of diopside (MgCaSi2O6) over wide pressure and temperature ranges based on experimental data from the literature. Our results agree well with the published experimental and theoretical data. The determined thermodynamic parameters exhibit nonlinear dependences with increasing pressure. Compared with other minerals in the upper mantle, we found that the adiabatic temperature gradient obtained using the thermodynamic data of diopside is larger than that of garnet while lower than that of olivine, when ignoring the Fe incorporation. Combining our results with thermodynamic parameters of garnet obtained in previous studies, we have estimated the adiabatic temperature gradient and geotherm of an eclogitic upper mantle in a depth range of 200–450 km. The results show that the estimated adiabatic temperature gradient of the eclogite model is ~16% and ~3% lower than that of the pyrolite model at a depth of 200 km and 410 km, respectively. However, the high mantle potential temperature of the eclogite model leads to a similar temperature as the pyrolite model in a depth range of 200–410 km.
Highlights
Temperature is one of the fundamental quantities for determining the physical and chemical properties of the Earth’s interior
Where T and z refer to the temperature and depth, respectively; g refers to the gravitational acceleration; KS refers to the adiabatic bulk modulus; V refers to the specific volume; and α, CP, and γ refer to the thermal expansion, isobaric heat capacity, and Grüneisen parameters, respectively
With the combination of the determined unit-cell volume and previously published vP and vS values at P–Ts [23], the KT, KS, and G of diopside can be calculated via Equations (6)–(8); the results are shown in Table 2 and Figures 2 and 3
Summary
Temperature is one of the fundamental quantities for determining the physical and chemical properties of the Earth’s interior. Considering the temperatures at the seismic discontinuities, several authors derived the thermodynamic parameters of the deep Earth with increasing depth using various thermal equations of state (EoS) [8,9,10]. In these studies, different seismic models and empirical equations or coefficients used in the estimations would cause significant discrepancies in the derived geotherms, influencing the investigations into the physical and chemical properties of the mantle
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
