Komatiite melting temperature

The coohng history of the mantle Figure 3.25 shows the secular cooling curve for the mantle from Richter (1988), the calculated potential temperatures for Archaean komatiites and basalts, and an estimated temperature for the Archaean subcontinental mantle. Two important conclusions follow. First, it is clear that the Archaean mantle had both hot and cool regions. Potential temperatures calculated from dry komatiite melting temperatures imply an anomalously hot mantle source,... 

Asahara Y. and Ohtani E. (2001) Melting relations of the hydrous primitive mantle in the CMAS-H2O system at high pressures and temperatures, and imphcations for generation of komatiites. Pkys. Earth Planet. Inter. 125, 31-44. 

Calculations based on radioactive heat production show that the Archaean mantle was hotter than the modern mantle. High mantle potential temperatures calculated from the ultramafic lavas - komatiites, common in the Archaean - led to the assumption that the Archaean mantle was substantially hotter than the modern mantle. However, the recent proposal that komatiites are the product of cooler, wet mantle melting weakens the argument for a very hot Archaean mantle, and there are now good grounds for arguing that the temperature of the Earth s mantle has declined by only 100-200°C since the mid-late Archaean. 

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