Partial melting and crust-mantle interaction in subduction channels: Constraints from experimental petrology

Abstract

It is proposed in the subduction channel model that the plate interface interaction is a basic mechanism for the mass and energy exchange between Earth’s surface and interior. The significant difference in composition and nature between continental lithosphere and oceanic lithosphere inevitably leads to variations in deep physical and chemical processes as well as crust-mantle interaction products in these two settings. Many studies of experimental petrology have provided constraints on the potential partial melting and crust-mantle interaction in oceanic subduction channels for silicate and carbonate rocks. The partial melts of mafic and felsic compositions are adakitic or non-adakitic granitic melts depending on melting pressure or depth. A trivial amount of CO2 can lower significantly the melting temperature of peridotites and lead to pronounced enrichment of incompatible elements in carbonate melt. The silica saturated or unsaturated melts can react with mantle-wedge peridotites in subduction channels to generate complex products. However, the existing experiments are mostly dedicated to island arc settings above oceanic subduction zones rather than dehydration melting above continental subduction zones. It is crucial to conduct high pressure and high temperature experiments to investigate all possible reactions between peridotites and crustal materials and their derivatives under the conditions responsible for the slab-mantle interface in continental subduction channels. Experimental results, combined with natural observations, are possible to elucidate the processes of metamorphic dehydration, partial melting and mantle metasomatism in continental subduction channels.