Indium-Rich Sulfides in the Iberian Pyrite Belt: Evidence from Variscan Syn-Tectonic Remobilization in the Lagoa Salgada VMS Deposit

Indium is a critical metal predominantly recovered as a by-product of Zn and Cu ores, reflecting its preferential incorporation into sphalerite in volcanogenic massive sulfide (VMS) systems. This study investigates the timing and mechanisms of indium remobilization during Variscan deformation at the Lagoa Salgada VMS deposit, Iberian Pyrite Belt (IPB), using integrated petrography, in situ geochemistry, and geochronology of sulfide-bearing stockwork veins. Optical petrography constrains mineral paragenesis, and micro-LIBS mapping revealed elemental distribution patterns. Mineral chemistry was quantified by SEM–EDS and EPMA, and LA-ICP-MS was employed for trace element analysis and Rb–Sr dating of white mica. Rb–Sr geochronology yields an age of 317.6 ± 7.5 Ma, dating deformation-related white mica contemporaneous with sulfide recrystallization and constraining syn-tectonic remobilization to late Bashkirian Variscan deformation. Textural and geochemical relationships indicate that indium redistribution occurred during orogenic shortening. These results provide direct evidence that the critical metal endowment in VMS deposits may be substantially modified by orogenic processes, highlighting the need to incorporate deformation-driven remobilization process into predictive exploration models. Understanding syn-tectonic mineralization is essential for refining exploration strategies in brownfield scenarios such as Lagoa Salgada and Neves-Corvo as well as in greenfield VMS exploration.