High Quality Content by WIKIPEDIA articles! Tonalite–trondhjemite–granodiorite (TTG) series are an aggregation of rocks that are formed by melting of hydrous mafic crust at high pressure. It is widely accepted that most Archaean granite–greenstones are dominated by TTG, although Late Archaean terranes, such as in the Yilgarn Craton, are dominated by potassium-rich granitoid rocks that are derived through remelting of older felsic TTG-dominated crust. According to this model, a much greater degree of crustal reworking has occurred in the Pilbara craton than is required by TTG-dominated crust.