The Cu Stockwork and Massive Sulfide Ore of the Feitais Volcanic-Hosted Massive Sulfide Deposit, Aljustrel, Iberian Pyrite Belt, Portugal: A Mineralogical, Fluid Inclusion, and Isotopic Investigation

摘要

The Variscan Feitais volcanic-hosted massive sulfide deposit in the Aljustrel district of the Iberian Pyrite Belt consists of 55 million metric tons of Zn-Pb-Cu massive sulfide overlying a Cu-rich stockwork. The massive ore is overlain by up to 30 m of feldspar-phyric, rhyolitic volcaniclastic rock and locally by a jasper and/or chert layer up to 15 m thick. The massive sulfide orebody consists dominantly of pyrite, sphalerite, galena, chalcopyrite, tetrahedrite-tennantite, arsenopyrite, and bournonite, together with minor quartz, chlorite, sericite, carbonate, and barite. The orebody is up to 100 m thick and is underlain by a tabular alteration zone of chlorite-dominated, locally silicified, felsic volcanic rock, the upper 30 to 60 m of which contains chalcopyrite-quartz-chlorite-sericite-carbonate–bearing stockwork vein(let)s that prior to deformation were at a shallow angle to the base of the massive orebody. Chloritized footwall rocks extend up to 20 m below the Cu stockwork zone and are underlain by up to 50 m of quartz-sericite-pyrite–altered rhyolitic rock. The stockwork veins also contain pyrite, tetrahedrite-tennantite, sphalerite, and arsenopyrite. Pyrite, both in stockwork and massive ore, locally displays partly recrystallized framboidal, reniform, and cellular textures.