Multiphase magmatism and crustal reworking in the Álamo Complex (Central Iberian Zone): evidence from geochemistry and zircon U-Pb geochronology

Abstract

The Álamo Complex, part of the Galician–Castilian Lineament within the Central Iberian Zone, lies between the Ollo de Sapo Domain and the Schist–Greywacke Complex. It comprises six tectonometamorphic sectors dominated by psammitic–pelitic metasediments (MTS), gneisses, migmatites, leucogranites and tourmaline-rich rocks. Zircon U–Pb dating identifies three Ediacaran partial melting events (∼628, 584 and 549 Ma) that occurred under high-pressure conditions within the kyanite stability field. These contrast with a low-pressure Variscan partial melting episode (∼310–315 Ma). Orthogneisses and leucogranites dated at ∼482–465 Ma record Cambro–Ordovician magmatism, characterized by abundant inherited Ediacaran zircon cores, indicating significant crustal recycling. Petrographic and geochemical similarities, together with shared zircon inheritance patterns, link the Álamo Complex with the Ollo de Sapo Domain and other segments of the Galician–Castilian Lineament, suggesting a common magmatic evolution. Tourmaline-rich rocks likely formed by boron metasomatism initiated during the Ediacaran and enhanced by recurrent partial melting. Variscan magmatism is represented by intrusive mafic and granitic bodies (∼307–311 Ma) and tourmaline-bearing leucogranites, reflecting continued reworking of Ediacaran crust into the Late Palaeozoic. These results shed light on the crustal evolution of Central Iberia.