Grain‐scale processes during isothermal‐isobaric melting of lherzolite

Abstract

The grain‐scale processes of peridotite partial melting were examined at 1340°C and 1.5 GPa using reaction couples formed by juxtaposing pre‐synthesized clinopyroxenite against pre‐synthesized harzburgite. Reaction between clinopyroxenite and harzburgite produces a melt‐enriched, orthopyroxene‐free, olivine + clinopyroxene reactive boundary layer. Clinopyroxene compositions vary systematically across the reactive boundary layer with compositional trends similar to the published clinopyroxene core‐to‐rim compositional variations in the bulk lherzolite partial melting studies conducted at similar P ‐ T conditions. The growth of the reactive boundary layer is at the expense of the harzburgite and is consistent with grain‐scale processes that involve dissolution, reprecipitation, and diffusive exchange between the interstitial melt and surrounding crystals.