Isotopic and geochemical record of the active to passive margin transition in NW Iberia during the Cambrian-Ordovician: vestiges of a waning continental arc

Time-resolved geochemical data from the orthogneisses of basal units Allochthonous complexes NW Iberian Massif allow us to track changes in composition magmas generated a subduction-related setting that affects continental margin, which evolves building volcanic arc its dismantlement during rifting episode. The are interpreted as peripheral section North African margin Gondwana and record Neoproterozoic Cambrian arc-related magmatism, followed by an episode Cambro-Ordovician rifting. intrusive rocks units, preserved orthogneisses, can be grouped into two magmatic suites: calc-alkaline (c. 493–475 Ma) alkaline per-alkaline 475–470 Ma). association has chemical ranging magnesian calcic metaluminous types ferroan calc-alkalic alkali-calcic peraluminous types. moderately metagranites have alkalic composition. characteristics metaigneous indicate older members suite (tonalites granodiorites) were environment, while formed intraplate extensional setting. negative values εNd (− 7.8 − 1.5) suggest crustal influence generation. range between 2.0 2.2, positive group, suggesting greater participation mantle component. transition is represented alkali-granites, coeval with intrusion basic magmas, likely derived magma underplating triggered after cessation magmatism Ordovician.