The conductance effect of melt in the upper mantle and origin of high conductivity anomalies in the asthenosphere
Geophysical electromagnetic depth soundings have revealed that there are significantly high conductivity anomalies with certain conductivity anisotropies in some local areas of the asthenosphere.However,the origin of those anomalies has long been controversial.It has long been a mainstream view that those high conductivity anomalies in the asthenosphere could be caused by a small amount of melts generated by the partial melting of peridotite.High-temperature and high-pressure experiments have shown that the high conductivity of a tiny amount of partial melts can result in the obvious increase of the bulk conductivity of mantle peridotites.The conductance effect of a small amount of melts in the solid-melt mixed system is controlled by a series of factors,such as the conductivity(associated with compositions of melts)and amount(or fraction)of the melts themselves and their spatial distribution(i.e.,the connectivity and topological structure)in the system.In this paper,we have briefly summarized advances of researches on the structure and conductivity of partial melts in the upper mantle in recent decades,have reviewed some potential issues in explaining the origin of high conductivity anomalies in the asthenosphere,and have prospected some future directions of relevant researches.
asthenosphereperidotiteelectrical conductivitymelts in the mantleexperimental study
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