Sediment-Peridotite Reaction Controls Fore-Arc Metasomatism and Arc Magma Geochemical Signatures

Subduction of oceanic crust buries an average thickness 300–500 m sediment that eventually dehydrates or partially melts. Progressive release fluid/melt metasomatizes the fore-arc mantle, forming serpentinite at low temperatures and phlogopite-bearing pyroxenite where slab surface reaches 700–900 °C. This is sufficiently high to melt subducted sediments before they approach depths arc magmas are formed. Here, we present experiments on reactions between melts peridotite 2–6 GPa/750–1100 °C, which correspond a subducting slab. The reaction volatile-bearing partial derived from with depleted leads separation elements layered arrangement metasomatic phases, layers consisting orthopyroxene, mica-pyroxenite, clinopyroxenite. selective incorporation in these closely resembles chemical patterns found K-rich magmas. Trace were imaged using LA-ICP-TOFMS, applied here investigate distribution trace within layers. Experiments different duration enabled estimates growth front, ranges 1–5 m/ky. These explain contents high-field strength as being due their loss during melting sedimentary materials fore-arc.