ARCHEAN AND EARLY PROTEROZOIC EVOLUTION O F THE NORTHEASTERN PART OF THE SAO-FRANCISCO CRATON (VALENTE-SANTA-LUZ AREA, BAHIA, BRAZIL)

The petrographic and structural analysis of the northeastern part of t he Sao Francisco craton allows us to define the Archaean and Palaeopro terozoic evolution. The Archaean evolution corresponds to the emplacem ent of a differentiated calk-alkaline series with gabbro-diorites and monzodiorites, granodiorites and also enderbites and charnockites whos e granulitic paragenesis would be of igneous origin. The Palaeoprotero zoic evolution (Transamazonian) can be divided in two stages : (I)rift ing with sedimentation and volcanism in the present greenstone belt ar ea, migmatization and anatexis in the infracrustal formations; (2) col lisional event (2,0 Ga) with development of the regional foliation and reworking of the migmatites in the present greenstone belt area; rewo rked migmatites and associated granitoids rise diapirically within the supracrustal sequences and define the characteristic structural patte rn of the greenstone belt: N-S elongated migmatitic and granitic domes separated by supracrustal sequence rim synclines.