The gold-bearing veins from the Piririca region, Ribeira Valley, State of São Paulo, Brazil, show epigenetic features and seem to be mainly related to a ductile-brittle shear zone, subordinate to the Agudos Grandes and Ribeira regional tectonic lineaments. Stratigraphically, presents the area a sequence of metavolcano-sedimentary rocks with associated metabasic rocks, characterized by low-grade metamorphism. These rocks are correlated with the Middle Proterozoic Perau Formation. Within the veins, pyrite and arsenopyrite are the most abundant sulphide minerais, with the following minerais having been detected in subordinate quantities: chalcopyrite, boulangerite, bournonite, jamesonite, tetrahedrite, sphalerite, galena, bornite, ilmenite and gold. Milky quartz is the dominat gangue. In the tentative preliminary paragenetic sequence proposed here, coarsegrained pyrite, arsenopyrite and ilmenite are considered as representing the fírst phase of sulphide deposition and have been affected by a brecciation/mylonitization deformation episode. The other minerais mentioned above represent a post-def ormation phase that occurs in veinlets and fractures, cutting crystals of pyrite and arsenopyrite
