3D Geological Model and Interpretation of Structural Evolution of the Masa Valverde VMS Deposit, Iberian Pyrite Belt (Spain)

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.