Metamorphosed and metamorphogenic ores of the Neves Corvo volcanogenic massive sulfide deposit, Iberian Pyrite Belt, Portugal

Neves Corvo the highest-grade deposit ever found on the Iberian Pyrite Belt, the richest volcanic massive sulfide (VMS) metallogenic province in the World, has been intensely studied during the last decade. In spite of research, the origin of Neves Corvo remains problematic. Based on extensive research on the characteristics of Neves Corvo fluid inclusions, I present a new interpretation for the genesis of the copper and tin ores overlying the massive sulfides, and for the stockwork copper ore. Quartz and cassiterite from these orebodies contain abundant dense aqueous carbonic fluids, the pressures of formation of which are incompatible with formation in a VMS environment. Petrographic and tectonostratigraphic evidence support a metamorphic origin. I propose that the rubane ores are metamorphogenic, and formed during orogenic recrystallization that affected the rocks about 30 m.y. after their formation; copper deposits in fissures are a stockwork ore intensely modified during the same metamorphic event.