Abstract Neves-Corvo, the jewel in the crown of the Iberian pyrite belt, was the most important massive sulfide discovery of the last three decades, both in gross value and significance to exploration for these ores. The deposit consists of five orebodies, which lie beneath a 230-to 800-m-thick succession of rocks of Upper Devonian and Carboniferous age. The massive sulfide orebodies were dated at ca. 350 Ma (Rb-Sr) and are hosted by rhyolitic to rhyodacitic volcanic and volcaniclastic rocks, which are part of a relatively thin Volcanic-Siliceous Complex (≤600 m). The latter is overlain by a thick cover of younger flysch and rests on older, Upper Devonian metasedimentary rocks. Low-angle thrusting has complicated the stratigraphic relationships between these major units. The deposit contains more than 300 million metric tons (Mt) of massive sulfides with about 100 Mt of mineable grade, the balance being highly pyritic. Like most other Iberian pyrite belt deposits, the Neves-Corvo deposit combines many distinctive characteristics of volcanic-hosted massive sulfide (VHMS) deposits worldwide, including very fine grained and metallurgically complex Zn-Pb-(Cu) ores, prominent metal zoning, and hydrothermal alteration of its footwall rocks; with some features akin to those of sedimentary exhalative (SEDEX) deposits. The uncommonly low ratio of volcanic versus sedimentary rocks in the overall footwall succession of the Iberian pyrite belt, the extremely homogeneous lead isotope signatures of the ores throughout the whole district, and the gigantism of many deposits are among the reasons that account to envisaging these deposits as hybrids linking those two major types of massive sulfide mineralization. In addition to these Iberian pyrite belt-like features, the Neves-Corvo deposit possesses some unusual characteristics as well. Among these stand out its uncommonly high copper-to-zinc ratio, which more than doubles that of typical Iberian pyrite belt deposits; its extremely copper rich ores that reflect zone refining within the deeper parts of the orebodies and late enrichment by remobilization phenomena; and its remarkably high tin content. The Neves-Corvo deposit is unique among massive sulfide deposits, as it encloses primary, extremely high grade, stringer and massive cassiterite ores, which may reach 60 wt percent Sn in small lenses of almost pure cassiterite. Additionally, about 200,000 t of tin metal occurs as lower grade cassiterite disseminations in the copper-rich parts of the deposit (avg 0.25 wt % Sn). These exceptional features of the Neves-Corvo ores call for unique ore-forming processes, which probably included a history of metal supply involving multiple sources. Its abnormal ore geochemistry, together with both stable and radiogenic isotope data, suggests that its generative sea-floor hydrothermal system may have included metal and fluid contributions from a deep-seated magmatic or metamorphogenic source, as well as mainly modified seawater, which leached the footwall rocks. The ongoing deposit-scale research in Neves-Corvo has put in evidence critical geologic and genetic factors that determined both the size and the extraordinary ore geochemistry of this deposit and, thus, ultimately, its high value. Relevant insights to integrated exploration have emerged from the identification and characterization of these factors. Also, these insights significantly widen the constraints that must be considered and applied in metallogenic modeling, thereby broadening the number and range of geologic relationships for consideration and application in future exploration projects. The collective consideration of all these understandings is especially significant in defining areas of remaining high exploration potential in long-studied districts like the Iberian pyrite belt and others worldwide.

Abstract Pre and Post Meeting trips (Figures 1.1 and 1.2) The aim of this visit is to observe and discuss stratigraphic, petrologic and structural features of selected outcrops of the Volcano Sedimentary Complex in the Neves Corvo mine vicinity. Emphasis is put on the felsic and mafic volcanic sequences exposed at the Neves Corvo-Rosario and Castro Verde Anticlines (Figure 1.3). The trip departs from the Neves Corvo mine. This stop is behind the main ventilation raise (CPV2) of the Neves Corvo mine. The exposed shales and thinly bedded siltstones belong to the Brancanes Formation, the uppermost unit of the allochthonous suite of the Volcano Sedimentary Complex. Although weathered to yellow or gray colors (the fresh rocks are dark) it is possible to observe the bedding planes and the shale/siltstone alternations. The siltstones display graded bedding, suggesting deposition by weak turbidity currents. The shales are rich in organic matter. Fossils of Posidonia becheri and goniatites are common, indicating a Late Visean age. The cleavage trends N135, 70 NE and its attitude relative to bedding shows that the outcrop is the normal limb of a large anticline. Intersection lineation L1 plunges 101 to SE. It is worth noting that the overlying Mértola Formation turbidites of the Baixo Alentejo Flysch Group provided the same faunal association and Late Visean spores. This suggests a gradual lithological transition between the Brancanes and the Mértola Formation. The cut to the north of the road between the mine main transformer station and the main entrance exhibits the siliceous