Water and its Effect on the Lithosphere-asthenosphere Boundary

The water in the Earth's upper mantle considerably lowers the melting temperature and this was investigated experimentally with the application of a novel experimental and analytical approach. It was shown that the instability of pargasite at depths greater than ~90km and at temperatures higher than 1000-1050 ºC leads to a sharp drop in the upper mantle's solidus temperature. It is speculated that this effect may define Earth's lithosphere–asthenosphere boundary at many geodynamic settings characterised by relatively high heat flow (>60 mW/m2).