The subject of this Geochemical Perspective is the continental crust – how it formed and at what rate. Important constraints come from the mineralogical and chemical compositions of granitoids, particularly those of the tonalites, trondjhemites and granodiorites (TTG) that are the dominant component of Archean continental crust. When used in conjunction with the results of experimental studies, these data help define the conditions of partial melting and the nature of the source of granitic magmas, as well as the geodynamic setting in which they formed. We learned that the dominant component in their source is mantle-derived basalt. This basalt is...

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