Fig. 1. Illustration of mantle melting due to decompression (a), heating (b) and release of water (c). Solidus temperature for peridotite (thick curve in a), b) and c)) is taken from Takahashi (1986). Thin curves give typical geotherms with a potential temperature Tp =1400 °C. In a) upwelling and decompression may be due to 50% thinning of the lithosphere. In b) the mantle temperature is increased by 200°C by e.g. the arrival of a plume. In c) the solidus is decreased due to 2.9 wt% water (Inoue and Sawamoto, 1992). The thin dashed curve give the saturated wet solidus temperature.