Sn and W mineralisation in the Iberian Peninsula

Abstract

This paper provides a comprehensive review and a refined classification of Sn-W mineralisation in the Iberian Peninsula, based on an extensive review of the available literature. The study synthesises and clarifies previously published information to improve the understanding of the mineralisation processes and their tectonic and magmatic controls. The Sn and W mineralisation in the Iberian Peninsula exhibit a strong correlation with specific granitic suites primarily formed during the late to post-Variscan orogeny. Structural controls, particularly syn- to late-D₃ strike-slip and/or extensional structures developed during the tectonic regime of the late Variscan, appear to be pivotal to facilitate the emplacement of this water-rich granitic magmas, that otherwise would have stalled at deeper environments, and the development of extensive hydrothermal systems. Two main mineralisation styles are identified: Sn-(Nb-Ta-Li) mineralisation under lithostatic pressure conditions, characterised by disseminated cassiterite in some pegmatites and altered granitic cupolas; and Sn-(Nb-Ta-Li) and W-(Sn) deposits formed at shallower levels within the brittle regime. The Sn-(Nb-Ta-Li) mineralisation is primarily associated with S-type granitic intrusions, while the W-(Sn) mineralisation also tends to be linked to these granitic suites, although several W-rich but Sn-poor deposits appear related to I-type granitoids. The metal enrichment in these magmas is likely due to a combination of inheritance from the source of the protoliths and magmatic evolution processes. The observed decoupling between Sn-rich and W-poor deposits versus W-(Sn)-rich deposits suggests contrasting behaviours of W and Sn during magmatic transport, the magmatic-hydrothermal transition, and the subsequent hydrothermal transport and deposition. Both types of deposits likely represent different settings and/or stages within a single magmatic-hydrothermal system.