High pressure-temperature point on an Archaean geotherm, implied magma genesis by crustal anatexis, and consequences for garnet-pyroxene thermometry and barometry

Abstract
The presence of metasediments indicates derivation of at least part of the 2.8 Ga old Scourie gneiss complex from a wet supracrustal series. The dry, large ion lithophile element depleted character of the present complex indicates an episode of anatexis and removal of granitic magmas during the evolution of the gneisses. This paper concentrates on the evidence for very high temperatures of metamorphism, the nature of the processes of anatexis and magma ascent and their implications for heat transfer in the Archaean crust; finally it reviews the credibility of some garnetpyroxene thermometers and barometers in the light of the external constraints placed upon possible solutions by the crustal setting of these granulite facies gneisses.