CLASSIFICAÇÃO DOS VEIOS QUARTZO-CARBONÁTICOS DE DEPÓSITOS AURÍFEROS NO LINEAMENTO CÓRREGO DO SÍTIO, QF, MG

Os depositos tipo lode-gold orogenicos Cachorro Bravo, Laranjeiras e Carvoaria, associados ao lineamento regional Corrego doSitio (CdS), estao localizados na porcao leste do Quadrilatero Ferrifero, sudeste do craton Sao Francisco. Sao hospedados em rochasmetassedimentares turbiditicas arqueanas do greenstone belt Rio das Velhas e controlados por zonas de cisalhamento NE-SW. Diques esoleiras metamaficos pre- a pos-deformacionais ocorrem intimamente associados a mineralizacao aurifera e constituem excelentes guiasprospectivos em lineamentos regionais como CdS. Cinco sistemas de veios, V1 a V5, sao classificados de acordo com a composicaomineralogica, textura, orientacao, distribuicao espacial e geometria. Dois tipos de quartzo ocorrem nestes veios, sendo o tipo 1predominantemente fume, cedo-hidrotermal, e o tipo 2 leitoso, recristalizado. Apenas os veios V1 (fault-fill veins) sao relacionados amineralizacao aurifera atraves da paragenese arsenopirita+pirita+pirrotita+berthierita+ ouro livre; se desenvolvem concordantes a foliacaomilonitica, S1m, e estao deformados. Veios V2 (oblique-extension veins) sao associados temporalmente aos V1 e, embora nao estejammineralizados nos depositos estudados, sao contemporâneos ao estagio mineralizador. Estes dois sistemas foram formados em regimeductil-ruptil. Veios V3 (extension e breccia veins) sao tardios a mineralizacao e representam um estagio posterior do fluido em regimeductil-ruptil a ruptil; podem estar relacionados a mudanca do campo de tensao regional e colocacao dos diques tardios Db1. Os veios V4(extension veins) possuem reacoes de substituicao mineral que marcam a hidratacao do sistema e podem se associar ao relaxamento dasforcas compressivas. Ja os veios V5 (vein stockworks) ocorrem apenas em diques e soleiras metamaficos Db1 e estudos de inclusoes fluidasindicam que esses contem fluido diferente dos outros sistemas. Palavras Chave: Classificacao de veios quartzo-carbonaticos, ouro orogenico, zonas de cisalhamento, diques e soleiras. ABSTRACT QUARTZ-CARBONATE VEIN CLASSIFICATION OF AURIFEROUS DEPOSITS IN CORREGO DO SITIO LINEAMENT, QF, MG. Theorogenic-type, lode-gold deposits Cachorro Bravo, Laranjeiras and Carvoaria, associated with the Corrego do Sitio (CdS) regional lineamentare located in the eastern portion of the Quadrilatero Ferrifero region, southern Sao Francisco craton, Brazil. They are hosted in Archeanmetaturbiditic rocks of the Rio das Velhas greenstone belt and controlled by NE-SW shear zones. Pre- to post-deformational dikes/sills areclosely related to gold mineralization and constitute excellent prospective guides in these regional lineaments such as CdS. Five veinsystems have been classified, V1 to V5, in accordance to their mineralogical composition, texture, orientation, spatial distribution andgeometry. Two types of quartz occur in these veins, with type 1 being predominantly smoky, early hydrothermal, and type 2 a milky,recrystallized quartz. Only V1 veins (fault-fill vein) are related to gold and have a paragenesis with arsenopyrite+pyrite+pyrrhotite+berthierite+ free gold; they develop along the mylonitic foliation S1m, and have been deformed. The V2 veins (oblique-extension veins) areassociated temporally with V1 and although non-mineralized, in the studied deposits they are contemporaneous to the gold stage. Thesetwo systems are formed under a ductile-brittle regime. The V3 veins (extension and breccias veins) are post gold and represent a late-stagehydrothermal fluid under ductile-brittle to brittle regime; they may be related to changes in the stress field and to the emplacement oflate-stage Db1 dikes. The V4 veins (extension veins) have mineral replacement reactions that represent hydration of the system associatedwith the relaxation of the compressive field. The V5 veins (stockwork style) are limited to metamafic Db1 dykes/sills and fluid inclusionstudies indicate that they contain a different fluid from the others systems. Keywords: Quartz-carbonate vein classification, orogenic gold, shear zones, dikes/sills