Subduction zone chemical fluxes and thermometry

The flux of H2O and trace elements from a subducted slab to the overlying mantle wedge imparts a distinctive geochemical flavour to arc magmas. In this talk I will use high-pressure experiments and thermodynamic calculations to show that the trace element flux is controlled by the presence (or absence) of a variety of accessory mineral phases in the subducted slab. Minerals such as monazite, allanite, rutile and zircon, although present in tiny amounts in the diverse rock types that are carried down subduction zones, exercise a disproportionate influence on fluid chemistry. The strong temperature dependence of accessory mineral solubility means that the trace element chemistry of arc magmas is a sensitive probe of the thermal structure of subduction zones.