The Geochemistry of Granites Associated with W-Sn Deposits of North and Central Portugal and Castilla-León in Spain

Tungsten and tin are critical raw materials for the European Union, yet robust exploration guides for these metals remain poorly defined. The Variscan granites of the Iberian Peninsula host numerous W-Sn deposits, but the geochemical criteria that distinguish productive from barren intrusions are still debated. This study presents a comprehensive whole-rock geochemical dataset from North and Central Portugal and Castilla-León in Spain. We demonstrate that while all studied granites are peraluminous, chondrite-normalised REE patterns allow discrimination of 15 distinct geochemical groups that correlate with emplacement age and mineralisation type. Tin-specialised leucogranites (e.g., Golpejas and Enaras) are characterised by extremely low ΣREE (<40 ppm), flat patterns (La/YbN < 10), and absent to positive Eu anomalies, together with enrichments in Rb (>800 ppm) and Sn (>500 ppm), and very low K/Rb ratios (<70). In contrast, tungsten-bearing granites (e.g., Borralha, Valderrodrigo) exhibit moderate to high ΣREE (40–272 ppm), strongly fractionated patterns (La/YbN > 15), and pronounced negative Eu anomalies (Eu/Eu* < 0.4). These differences confirm that W and Sn mineralisation in NW Iberia arise from distinct magma sources and differentiation paths. This work verifies how, through their mode of occurrence and the geochemistry of rare earth elements and trace elements, potentially mineralised granites can be distinguished and how they can be used in exploration programs.