After dehydration, solute-rich fluids are released from the slab and metasomatise the overlying mantle wedge of MORB-like asthenosphere, enriching it with volatiles and large ion lithophile elements (LILE). The current belief is that the generation of andesitic magmas is multistage, and involves crustal melting and assimilation of primary basaltic magmas, magma storage at the base of the crust (underplating by dense, mafic magma as it ascends), and magma homogenization. The underplated magma will add a lot of heat to the base of the crust, thereby inducing crustal melting and assimilation of lower-crustal rocks, creating an area with intense interaction of the mantle magma and crustal magma. This progressively evolving magma will become enriched in volatiles, sulfur, and incompatible elements – an ideal combination for the generation of a magma capable of generating an ore deposit. From this point forward in the evolution of a porphyry deposit, ideal tectonic and structural conditions are necessary to allow the transport of the magma and ensure its emplacement in upper-crustal levels.