부산대학교 도서관

Electrical conductivity of mantle minerals is highly sensitive to water content, so estimates of this physical parameter based on long‐period electromagnetic induction data can help to constrain mantle hydration. Reliable constraints require conductivity model with sufficient resolution at relevant depths, as well as a comprehensive uncertainty analysis. In this global induction study, we combine data from the primarily ionospheric diurnal variation and longer‐period magnetospheric ring current bands. Joint inversion of these two data sources allows significantly improved vertical resolution of radial conductivity variations, especially in the mantle transition zone (MTZ). We then evaluate how uncertainties in the resulting conductivity model, in thermal models, and in laboratory results affect water content estimates, focusing on the MTZ. Our analysis suggests that the conductivity model is best explained by a dry MTZ with pyrolitic composition. Considering the uncertainties, an upper bound on average water content in the MTZ is 0.3 wt.% of water. Plain Language Summary: The mantle transition zone is a key player in the deep global water cycle, but its water content has been long debated. Since electrical conductivity can provide tight constraints on mantle water content, this study utilizes the geomagnetic fields to probe the electrical conductivity of deep mantle and estimates the water content based on the averaged conductivity‐depth profile. Our new conductivity model for continent mantle is characterized by high resolution in 200–800 km depth. Since the interpretation of conductivity profiles depends on laboratory results which contain experimental errors and other uncertainty, here we analyze the effect of these uncertainties on water content estimates. The result shows that the conductivity model is compatible with a pyrolitic mantel transition zone with water less than 0.3 wt.%. Key Points: A new conductivity model for continental mantle has been obtained by joint inversion of diurnal variations and magnetospheric signalsThe broader frequency range used improves depth resolution of mantle transition zone (MTZ) electrical conductivityThe conductivity model is not compatible with a pyrolitic MTZ with water content exceeding 0.3 wt.% [ABSTRACT FROM AUTHOR]