Granites and the nature of the Variscan Crust

Unlike the neighbouring cratonic crust, the orogenic crust of the European Variscan belt is granite-rich and seldom has a mafic lower layer. In this work, we compiled a database of ca. 1500 plutons, classified by type, to elucidate the evolution of the Belt and the origin of this uncommon crust. The core of the belt originated by massive melting of fertile quartzo-feldspathic sources (felsic meta-igneous or meta-sediments) derived from an Ediacaran–Ordovician accretionary system. As a consequence of Variscan processes, an unusually felsic lower crust formed either by relamination or by extensive crustal anatexis producing a granitic upper crust and a laminated, restitic lower crust. This is in strong contrast to conventional models, formulated mainly in magmatic arcs, assuming mafic lower crustal compositions. Thus, global estimates on nature and evolution of the continental crust should take into account the specificity of orogenic systems resulting in distinct crustal structures and compositions.