Thermal Conductivity and Thermal Diffusivity of Tremolite at High Temperature and Pressure and Implications for the Thermal Structure of the Venusian Lithosphere

Abstract

AbstractThermal conductivity (κ) and thermal diffusivity (D) of tremolite were measured at up to 2.5 GPa and 1,373 K using the transient plane‐source method in a multi‐anvil apparatus. Thermal conductivity and thermal diffusivity of tremolite decrease monotonically before dehydration (<1,173 K) and increase significantly after dehydration. Tremolite exhibits positive pressure dependence before dehydration. Heat capacity (C) of tremolite calculated fromκandDshows a positive pressure dependence and is controlled by an almost constant thermal expansion coefficient (α) with temperature. Conductive heat transport and radiative heat transport dominate the heat transport process before dehydration, and the significant increase in thermal conductivity after dehydration is attributed to convective heat transport. A compositional model of the Venusian lithosphere composed of a basaltic crust and peridotite mantle with or without tremolite was established. The thickness of the Venusian lithosphere with or without tremolite for Venus was calculated by combining the heat flow (from 20 to 80 mW/m2) at a certain depth (from 5 to 25 km) of crust, ranging from 24.4 to 184.6 km.