Experimental Melting of Pelagic Sediment, Constraints Relevant to Subduction

The experimental melting relations of pelagic red clay with water indicate a low temperature solidus, close to 650°C. This is significant as the red clay water solidus is lower than the solidus of gabbro with water, to depths of at least 140 km. Such a solidi configuration allows for melting of sediments, whilst gabbroic crust dehydrates, in moderate-temperature steady-state subduction regimes. This new experimental evidence lends support to (1) the sediment melting- gabbro dehydration hypothesis, recently proposed on independent geochemical criteria, and (2) may place relatively narrow limits on temperatures of the upper slab-mantle boundary, over a considerable depth interval, an apropos constraint for thermal modelling of steady-state subduction regimes.