Effect of Iron Content on the Thermal Conductivity and Thermal Diffusivity of Orthopyroxene

The thermal properties of major minerals play a key role in understanding the internal dynamic mechanism and thermal evolution of the Earth and rocky planets. In this study, we first investigated the effect of Fe on the thermal conductivity (κ) and the thermal diffusivity (D) of orthopyroxene at 1–3 GPa and 293–873 K by the transient plane source method. The κ and D both decrease with increasing temperature and decreasing pressure. With increasing Fe content, the two parameters both quickly decrease from the beginning and then slack off. We further modeled the thermal evolution of S-type asteroids, which strongly depends on the composition model and the dimension of the planet. Combining the present data with surface heat flow and heat production, the lunar's geotherm until 1,400 km is constructed. The core-mantle boundary temperature of the Moon is refined from 1,883 to 1,754 K.