Mafic rocks are often the key to magmatic and metamorphic processes that take place deep within the continental crust. Their chemical composition, taken together with field and petrographic study, are useful in assessing the nature of their mantle source and possible geological setting in which they were emplaced. A metagabbro body in the high-grade terrain of Guaxupé, southeastern Brazil, serves as a good example for deciphering the origin of basic magmas in a granulite belt. The metagabbro largely preserves igneous textures, recrystallized in granulite facies, despite the fact that it occurs in a zone of intense ductile deformation that has affected the charnockite and garnet-biotite gneiss country rocks. The basic body varies from olivine websterite, through websterite to gabbro, and major and trace elements confirm the narrow range of its differentiation. K, Rb, and the HFSE, Zr, Nb, Ti, and P are low; their Zr/Y ratios are lower than for other mafic granulites of this region; REE and multi-element values point to a continental margin setting; their Sm-Nd isotopes suggest an enriched mantle source. These rocks possibly represent a component of basaltic underplating in the Guaxupé nappe that caused high thermal gradients responsible for granulite facies metamorphism, as well as partial melting of crustal rocks, such as garnet-biotite gneisses, under high-grade conditions.6 241263Almeida, F.F.M., Hasui, Y., Brito Neves, B.B., Fuck, R.A., Brazilian structural provinces: An introduction (1981) Earth Science Rev., 17, pp. 1-29Baker, J.M., Newton, R.C., Standard thermodynamic properties of meionite, Ca4Al6Si6O24CO3, from experimental phase equilibrium data (1994) Amer. Miner., 79, pp. 478-484Ballhaus, C., Berry, R.F., Crystallization pressure and cooling history of the Giles layered igneous complex, central Australia (1991) J. 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