The mafic rocks of the stratiform complexes of Mangabal I and II, Goiás State, metamorphosed at temperatures around 700±50ºC, low fO2 and P H2O = P T exhibit different parageneses, depending on their aSIO2 . Olivine gabbronorites gave rise to plagioclase (andesine), gedrite and hornblende richer in the pargasitic molecule. The composition of the amphiboles and the absence of quartz in this paragenesis result from lower values of aSIO2 . Recrystallization of gabronorites at higher aSIO2 gave rise to anthophyilite, Mg-hornblende (poorer in pargasitic molecule) and quartz. 'Plagioclase (andesine) also occurs in this association.
