Journal
SCIENCE CHINA-EARTH SCIENCES
Volume 66, Issue 8, Pages 1865-1876Publisher
SCIENCE PRESS
DOI: 10.1007/s11430-022-1111-6
Keywords
Mantle convection; Thermal conductivity; Core-mantle boundary heat flow; Primordial mantle material; LLSVPs
Categories
Ask authors/readers for more resources
Thermal conductivity of the mantle varies with pressure and composition, and it plays a crucial role in the thermochemical evolution of the Earth's mantle. Increasing depth-dependent thermal conductivity leads to a larger core-mantle boundary heat flow and more stable thermochemical piles, while decreasing composition-dependent thermal conductivity slightly destabilizes the primordial thermochemical piles. The long-term stability of the piles decreases if the primordial mantle material is compositionally more viscous and this destabilizing effect is enhanced by decreasing composition-dependent thermal conductivity. Overall, the combined effects of depth- and composition-dependent thermal conductivity and compositional viscosity ratio significantly influence the thermochemical evolution of the mantle.
Thermal conductivity plays an important role in the thermochemical evolution of Earth's mantle. Recent mineral physics studies suggest that the thermal conductivity of the mantle varies with pressure and composition, and this may play an important role in the evolution of the Earth's mantle. Meanwhile, the rheology of the deep mantle is also supposed to be composition-dependent. However, the dynamic influences of these factors remain not well understood. In this study, we performed numerical experiments of thermochemical mantle convection in 2-D spherical annulus geometry to systematically investigate the effects of depth- and composition-dependent thermal conductivity and the compositional viscosity ratio on the long-term evolution of the large thermochemical structure of primordial material in Earth's mantle. Our results show that increasing the depth-dependent thermal conductivity leads to a larger core-mantle boundary (CMB) heat flow and allows the formation of more stable large thermochemical piles (e.g., Large Low Shear Velocity Provinces, LLSVPs); while decreasing the composition-dependent thermal conductivity would slightly destabilize the primordial thermochemical piles, increase the altitude of these piles and the temperature differences between the piles and the ambient mantle. If the primordial mantle material is compositionally more viscous (e.g., 20 times than that of the ambient mantle), the long-term stability of the thermochemical piles of primordial material decreases, and this destabilizing effect will be enhanced by decreasing the composition-dependent thermal conductivity. As a result, the thermochemical piles would be unstable in the core-mantle boundary region. Therefore, our study indicates that the combined effects of depth- and composition-dependent thermal conductivity and compositional viscosity ratio are pronounced to the thermochemical evolution of the mantle.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available