Zinciferous mineralization at the Neves-Corvo deposit, Iberian Pyrite Belt, Portugal: the other end of the spectrum

The Neves-Corvo deposit is widely known as a world-class copper mine, but it constitutes as well one of the world's largest repositories of zinc, especially in its northernmost orebody Lombador -, which represents alone 62% of the total zinc reserves of the deposit. The orebody lies on a stratabound stockwork that extends across its entire length. Hydrothermal alteration in the Lombador orebody contrasts with alteration signatures ascribed to the high-temperature parts of the ore-forming system, namely at the Corvo and Graca orebodies. A chloritic core grades outwards into sericitic peripheral zones, but intense carbonatization constitutes a key distinctive feature of the zinc mineralization. The zinc-related mineralization and alteration facies indicate mild temperatures, and formation from reduced, Fe-rich, moderately low pH, CO2-enriched solutions, and a combination of sub-seafloor replacement and episodic direct exhalation onto the seafloor in closed basins. A magmatic-hydrothermal model emerged from the ore geochemistry, hydrothermal alteration patterns, trace elements, and unique stable and radiogenic isotopic signatures found at the Corvo orebody. Conversely, direct magmatic contributions to the metal budget of the low-temperature end of the Neves-Corvo mineralization spectrum are precluded by the Pb and Nd isotope signatures of the Lombador zinciferous ores, which compare to typical IPB deposits.