Mónica Arias

Antimony (Sb) is a critical raw material whose European supply depends strongly on imports, renewing interest in the metallogenic framework of historical Sb provinces. This review compiles and reassesses 100 Sb deposits and occurrences from Spain and Portugal within a unified geological, structural, and mineralogical framework. Six broad deposit types and twelve mineral associations are recognized, with the Central Iberian Zone containing the largest number and greatest diversity of occurrences. The regional distribution of mineralization indicates a hierarchical control in which long-lived Variscan shear zones and crustal faults organized hydrothermal circulation, whereas second-order fractures, breccias, and favorable lithological or stratigraphic horizons localized ore deposition. Vein-type and stratabound mineralization are therefore interpreted as potentially related expressions of evolving tectono-hydrothermal systems rather than necessarily distinct genetic families. Gold-bearing Sb systems are particularly developed in western Iberia, whereas carbonate-hosted Sb-Hg mineralization characterizes the Cantabrian Zone and Sb-Cu associations are prominent in the South Portuguese Zone. An integrated multistage model is proposed in which heterogeneous pre-ore metal reservoirs, Variscan crustal architecture, late Variscan reactivation, magmatic and thermal activity, and local structural-lithological traps collectively controlled Sb mobilization and deposition. The model emphasizes repeated tectono-hydrothermal reactivation rather than a single universal metal or fluid source.

This study presents a 3D geological model and structural interpretation of the Masa Valverde volcanogenic massive sulfide (VMS) deposit in the Iberian Pyrite Belt. The deposit is hosted by felsic porphyritic volcanic rocks, volcanic tuffs, and black shales. A 3D geological model of the orebodies and host rocks, constructed from 145 drill-core logs, allowed us to build 16 cross-sections spaced 100 m apart and constrain the mineralization geometry and its structural evolution. Mineralization formed during Early Carboniferous transtensional tectonics within an extensional basin, where an extensional duplex structure controlled the development of the primary massive sulfide body and its associated stockwork. Subsequent counterclockwise rotation of the principal stress axes reactivated extensional faults as reverse faults during tectonic inversion. This deformation strongly modified the VMS system through buttressing, generating extensive open spaces, and promoting the brecciation and recrystallization of both the stockwork and massive sulfides. These processes produced a new paragenesis dominated by chalcopyrite and sphalerite, with minor galena among other minerals, which cemented the breccias, partially replaced earlier mineral assemblages, and filled open fractures. The resulting Cu-Zn enrichment, spatially associated with buttressed zones, provides new insights into ore remobilization with direct implications for the development of the ongoing underground mine.

This study presents a 3D geological model and structural interpretation of the Masa Valverde volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt. The deposit is hosted by felsic porphyritic volcanic rocks, volcanic tuffs and black shales. A 3D geological model of the orebodies and host rocks, constructed from 145 drillcore logs, allowed us to build 16 cross-sections spaced 100 m apart, and constrain the mineralisation geometry and its structural evolution. Mineralization formed during Early Carboniferous transtensional tectonics within an extensional basin, where an extensional duplex structure controlled the development of the primary massive sulfide body and its associated stockwork. Subsequent counterclockwise rotation of the principal stress axes reactivated extensional faults as reverse faults during tectonic inversion. This deformation strongly modified the VMS system through buttressing, generating extensive open spaces and promoting brecciation and recrystallization of both the stockwork and massive sulfides. These processes produced a new paragenesis dominated by chalcopyrite and sphalerite, with minor galena among other minerals, which cemented the breccias, partially replaced earlier mineral assemblages, and filled open fractures. The resulting Cu-Zn enrichment, spatially associated with buttressed zones, provides new insights into ore remobilization with direct implications for the development of the ongoing underground mine.

The Touro volcanogenic massive sulfide (VMS) deposit is located in the NW of the Iberian Variscan massif in the Galicia-Trás-os-Montes Zone, an amalgamation of several allochthonous terrains. The Órdenes complex is the most extensive of the allochthone complexes, and amphibolites and paragneisses host the deposit, characterized as being massive or semimassive (stringers) sulfides, mostly made up of pyrrhotite and chalcopyrite. The total resources are 103 Mt, containing 0.41% copper. A 3D model of the different orebodies and host rocks was generated using data from 1090 drill core logs. The model revealed that the structure of the area is a N–S-trending antiform. The orebodies crop out in the limbs and in the hinge zone. The mineralized structures are mostly tabular, up to 100 m in thickness and subhorizontal. Based on the petrography, geochemistry and the 3D model, the Touro deposit is classified as a VMS of the mafic-siliciclastic type formed in an Ordovician back-arc setting, which was buried and metamorphosed in Middle Devonian.