The Pinhal Group is a very important lithostratigraphic unit that border the São Francisco Craton, in the NE of the State of São Paulo and SSW of the State of Minas Gerais, southern Brazil. The Pinhal and Socorro Complexes are the main granitic-migmatitic areas of this unit, including "migmatites forming granites", migmatites, "normal granites" and several medium to high grade metamorphic country rocks. The granitic suite include various equigranular and porphyroid types and porphyritic, pegmatitic and aplitic dikes. Geochronologic age determinations indicate their relation with "Brazilian Cycle" (Baikalian Cycle, of Upper Precambrian age); the country rocks belong to the Amparo Group (Middle Precambriam), which rocks underwent an intensive remobilization during the Brazilian Cycle. The "migmatites forming granites" are surrounded by an aureole of migmatites composed of 3 zones: the outer zone is formed by layered migmatites, the medium one by agmatitic and "schollen" migmatites; and the inner one by "schlieren", nebulitic and homophanic migmatites. The central granitic core is equigranular or porphyroid. The migmatitic aureole is frequently disturbed by faults, by "normal granite" instrusions or by the interference of adjacent aureoles; these disturbances lead to very complex (polyphasic) migmatites. Strong metassomatic phenomena affected the rocks of the Pinhal Group, at two distinct phases. The first one, of potassic character, in characterized by an intensive development of microcline mega-crystals; and the second one, of sodic nature, by the formation of pure albite. In each phase, distinct metassomatic pulsations have been observed, linked with the several intrusion and tectonic events which have affected the complexes which form megadiapirs of polydiapiric nature. The big granite plutons have arisen from the base of the sialic crust along "thermal channels" related to zones of tectonic weakness. During this slow ascension these bodies have undergone deep modifications (remobilization, subsolidus recrystalization, metasomatism, assimilation and fractional crystalization), without significative changes in their chemical character. From the regional point of view the Pinhal Group is correlated to the Serra dos Órgãos Group, in the Rio de Janeiro State. Economic geology in the investigated region is mainly related to pegmatites exploitation.
