Ideas about granite generation have evolved considerably during the last two decades. The present paper lists what ideas were accepted and later modified, concerning the processes acting during the four stages of granite generation: melting, melt segregation and ascent, and emplacement. The active role of the mantle constitutes a fifth stage. Fluid assisted melting, deduced from metamorphic observations, was used to explain granite and granulite formation. Water seepage into meta-sedimentary rocks can produce granitic melt by depleting melting temperature. CO2 released by the mantle helps transforming rocks into granulites. However, dehydration melting is now considered as being the origin of most granitic melts, as confirmed by experimental melting. First hydrous minerals involved are muscovite, then biotite at higher temperature. At even deeper conditions, hornblende dehydration melting leads to calc-alkaline magmas. Melt segregation was first attributed to compaction and gravity forces due to density contrast between melt and its matrix. This was found insufficient for magma segregation in the continental crust because they were transposed from mantle conditions (decompression melting) to crustal conditions (dehydration melting). Rheology of two-phase materials documents that melt segregation is discontinuous in time, occurring in successive bursts. Analogue and numerical models confirm the discontinuous melt segregation. Compaction and shear localisation interact non-linearly, so that melt segregates into tiny conduits. Melt segregation occurs at low degree of melting. Global diapiric ascent and fractional crystallisation in large convective batholiths also shown to be inadequate and at least partly erroneous. Diapiric ascent cannot overcome the crustal brittle-ductile transition. Fracture-induced ascent faces the neutral buoyancy level at which the ascent should stop, but it doesn't. Non-random orientation of magma feeders within the ambient stress field indicates that deformation controls magma ascent. Detailed gravity and structural analyses indicate that granite plutons are built from several magma injections, each of small size and with evolving chemical composition. Detailed mapping of the contact between successive magma batches documents either continuous feeding, leading to normal petrographic zoning, or by periods separated in time, commonly leading to reverse zoning. The local deformation field controls magma emplacement and imposes the shape of plutons. A typical source for granite magmas involves three components, from the mantle, lower and intermediate crusts. The role of the mantle in driving and controlling essential crustal processes appears necessary in providing stress and heat, as well as specific episodes of time for granite generation. These mechanisms constitute a new paradigm for granite generation.
TOWARD A NEW PARADIGM FOR GRANITE GENERATION