Mineralização aurífera em veios de pirita maciça na Serra da Paciência, Bahia: tipologia distinta dos conglomerados com Au-U do grupo Jacobina

Abstract

Gold mineralization that differs from the classic conglomerate-hosted Au-U mineralization from Serra da Jacobina was found at Serra da Paciência, 6km north-northwest of Pindobaçu town, Bahia State. The mineralization occurs 100 meters south of garimpo Mina Velha and consists of a 40cm-thick gold-bearing vein of massive pyrite hosted in a chloritite (metamorphosed ultramafic dike), which intrudes quartzites of the Cruz das Almas Formation (Jacobina Group). The chloritite has N-S direction, thickness between 1,5 and 2 m and is affected by a reverse fault of 095/63 attitude. Samples of massive pyrite returned Au grades of 336 and 385 ppb. At the garimpo Mina Velha gold mineralization is related to pyrite-bearing quartz veins hosted by chloritite affected by the same reverse fault. Gold values in samples from Mina Velha range from 239 ppb, in the chloritite, to 22,660 ppb, in the pyrite-bearing quartz vein. The gold occurrence related to massive pyrite vein reveals to be a prospective alternative different from the conglomerate-hosted Au-U of the Jacobina group.