3D model for the late Carboniferous crustal and lithospheric scale structure of the Variscan belt beneath the French Massif Central. Gravitational collapse is accommodated by (i) lateral flow of the partially molten orogenic root from the western to the eastern side of the French Massif Central and from the internal to the external zone toward the south, and (ii) upward flow to form migmatite domes within Metamorphic Core Complexes. The Sillon Houiller accommodates differential slab retreat between the eastern and western parts of the French Massif Central.