PARAGÊNESE E SUCESSÃO MINERAL NAS DIFERENTES ETAPAS DA EVOLUÇÃO DA MINERALIZAÇÃO Cu-Pb-Zn DO DISTRITO DE CAMAQUÃ, RS

Abstract

The sulfide mineralization of die Camaqua Mines (Cu) and of the Santa Maria Deposit (Pb-Zn). State of Rio Grande do Sul, southern Brazil, is associated with red bed conglomerates and sandstones, deposited hi an alluvial fan environment at the end of the Brasiliano Event. The non opaque cement and ore mineral analysis allow to identify four main phases hi the mineralization process occurred after the sedimentation: the eodiagenetic and mesogenetic phases are represented by the formation of hematite I-rutile and pyrite I-marcasite, respectively; the late diagenetic to epigenetic phase has occurred at deep burial levels and it was superimposed to the least non opaque cements. It comprises the galena-sphalerite-chalcopyrite paragenesis in the Santa Maria Deposit and the pyrite Il-chalcocite I-bornite I-chalcopyrite paragenetic sucession in the Camaqua Mines; the paleo-oxidation/cementation phase took place after uplift and unroofing. It is well observed in the Camaqua Mines where the previous sulfide phases were altered and replaced by die hematite IT-bomite Il-chalcocite TI-covellite. In the Santa Maria Deposit occur the hematite n-stephanite-chalcocite II-covellite-native silver paragenesis; and the tectonic remobilization phase of the previous ore cements has occurred during bed tilting and leaded to the formation of pvrite-bomite-chalcopyrite-quartz and hematite-bornite-chalcocite-barite-calcite veins in the Camaqua Mines, and only of veinlets with galena-sphalerite in die Santa Maria Deposit. The deposition of die Guaritas Formation occurred when die mineralization process had finished, i.e. after the tilting of die Bom Jardim Group beds.