Abstract
We applied our newly developed intergranular enrichment factor, which can examine the intergranular components, to reported geochemical data obtained from numerous mantle xenoliths collected from elsewhere. The analysis based on the enrichment factor, interface thickness, and grain size in rocks reveals that the enrichments of incompatible elements at intergranular regions are typically ~10^3 larger than that expected from equilibrium chemical segregation at interfaces (i.e., grain and interphase boundaries). The best explanation for the observed intergranular enrichment is the presence of ~0.1 vol% of melt in all rocks. We propose that such specific amount of melt corresponds to the critical melt fraction, where melt starts to separate from the rock, eventually appearing at the Earth's surface.
